diff options
author | kris <kris@FreeBSD.org> | 2000-03-26 07:37:48 +0000 |
---|---|---|
committer | kris <kris@FreeBSD.org> | 2000-03-26 07:37:48 +0000 |
commit | 6948a837767a9680a772b450c7b732a4ae2cb6b3 (patch) | |
tree | b3a49bfc6fa4a3d8454dabb3d5e8eb13430c567f /crypto/openssh | |
parent | e46dd7a5de99ccc52b80f94f507cb226ce21c6d0 (diff) | |
download | FreeBSD-src-6948a837767a9680a772b450c7b732a4ae2cb6b3.zip FreeBSD-src-6948a837767a9680a772b450c7b732a4ae2cb6b3.tar.gz |
Resolve conflicts.
Diffstat (limited to 'crypto/openssh')
-rw-r--r-- | crypto/openssh/auth-krb4.c | 11 | ||||
-rw-r--r-- | crypto/openssh/auth-rsa.c | 37 | ||||
-rw-r--r-- | crypto/openssh/bufaux.c | 8 | ||||
-rw-r--r-- | crypto/openssh/cipher.c | 16 | ||||
-rw-r--r-- | crypto/openssh/cipher.h | 8 | ||||
-rw-r--r-- | crypto/openssh/fingerprint.c | 4 | ||||
-rw-r--r-- | crypto/openssh/packet.h | 6 | ||||
-rw-r--r-- | crypto/openssh/rsa.c | 6 | ||||
-rw-r--r-- | crypto/openssh/servconf.c | 4 | ||||
-rw-r--r-- | crypto/openssh/ssh-agent.c | 9 | ||||
-rw-r--r-- | crypto/openssh/ssh.1 | 527 | ||||
-rw-r--r-- | crypto/openssh/ssh.c | 13 | ||||
-rw-r--r-- | crypto/openssh/ssh.h | 36 | ||||
-rw-r--r-- | crypto/openssh/sshconnect.c | 92 | ||||
-rw-r--r-- | crypto/openssh/sshd.8 | 385 | ||||
-rw-r--r-- | crypto/openssh/sshd.c | 66 |
16 files changed, 684 insertions, 544 deletions
diff --git a/crypto/openssh/auth-krb4.c b/crypto/openssh/auth-krb4.c index 8c308bd..0b09eb9 100644 --- a/crypto/openssh/auth-krb4.c +++ b/crypto/openssh/auth-krb4.c @@ -141,7 +141,7 @@ int krb4_init(uid_t uid) { static int cleanup_registered = 0; - char *tkt_root = TKT_ROOT; + const char *tkt_root = TKT_ROOT; struct stat st; int fd; @@ -188,19 +188,20 @@ auth_krb4(const char *server_user, KTEXT auth, char **client) KTEXT_ST reply; char instance[INST_SZ]; int r, s; + socklen_t slen; u_int cksum; Key_schedule schedule; struct sockaddr_in local, foreign; s = packet_get_connection_in(); - r = sizeof(local); + slen = sizeof(local); memset(&local, 0, sizeof(local)); - if (getsockname(s, (struct sockaddr *) & local, &r) < 0) + if (getsockname(s, (struct sockaddr *) & local, &slen) < 0) debug("getsockname failed: %.100s", strerror(errno)); - r = sizeof(foreign); + slen = sizeof(foreign); memset(&foreign, 0, sizeof(foreign)); - if (getpeername(s, (struct sockaddr *) & foreign, &r) < 0) { + if (getpeername(s, (struct sockaddr *) & foreign, &slen) < 0) { debug("getpeername failed: %.100s", strerror(errno)); fatal_cleanup(); } diff --git a/crypto/openssh/auth-rsa.c b/crypto/openssh/auth-rsa.c index d385ab7..7829cac 100644 --- a/crypto/openssh/auth-rsa.c +++ b/crypto/openssh/auth-rsa.c @@ -17,7 +17,7 @@ */ #include "includes.h" -RCSID("$Id: auth-rsa.c,v 1.18 2000/02/11 10:59:11 markus Exp $"); +RCSID("$Id: auth-rsa.c,v 1.19 2000/03/23 22:15:33 markus Exp $"); #include "rsa.h" #include "packet.h" @@ -25,6 +25,7 @@ RCSID("$Id: auth-rsa.c,v 1.18 2000/02/11 10:59:11 markus Exp $"); #include "ssh.h" #include "mpaux.h" #include "uidswap.h" +#include "match.h" #include "servconf.h" #include <openssl/rsa.h> @@ -61,10 +62,9 @@ extern unsigned char session_id[16]; */ int -auth_rsa_challenge_dialog(BIGNUM *e, BIGNUM *n) +auth_rsa_challenge_dialog(RSA *pk) { BIGNUM *challenge, *encrypted_challenge; - RSA *pk; BN_CTX *ctx; unsigned char buf[32], mdbuf[16], response[16]; MD5_CTX md; @@ -77,19 +77,11 @@ auth_rsa_challenge_dialog(BIGNUM *e, BIGNUM *n) /* Generate a random challenge. */ BN_rand(challenge, 256, 0, 0); ctx = BN_CTX_new(); - BN_mod(challenge, challenge, n, ctx); + BN_mod(challenge, challenge, pk->n, ctx); BN_CTX_free(ctx); - /* Create the public key data structure. */ - pk = RSA_new(); - pk->e = BN_new(); - BN_copy(pk->e, e); - pk->n = BN_new(); - BN_copy(pk->n, n); - /* Encrypt the challenge with the public key. */ rsa_public_encrypt(encrypted_challenge, challenge, pk); - RSA_free(pk); /* Send the encrypted challenge to the client. */ packet_start(SSH_SMSG_AUTH_RSA_CHALLENGE); @@ -141,7 +133,7 @@ auth_rsa(struct passwd *pw, BIGNUM *client_n) FILE *f; unsigned long linenum = 0; struct stat st; - BIGNUM *e, *n; + RSA *pk; /* Temporarily use the user's uid. */ temporarily_use_uid(pw->pw_uid); @@ -203,8 +195,9 @@ auth_rsa(struct passwd *pw, BIGNUM *client_n) /* Flag indicating whether authentication has succeeded. */ authenticated = 0; - e = BN_new(); - n = BN_new(); + pk = RSA_new(); + pk->e = BN_new(); + pk->n = BN_new(); /* * Go though the accepted keys, looking for the current key. If @@ -242,7 +235,7 @@ auth_rsa(struct passwd *pw, BIGNUM *client_n) options = NULL; /* Parse the key from the line. */ - if (!auth_rsa_read_key(&cp, &bits, e, n)) { + if (!auth_rsa_read_key(&cp, &bits, pk->e, pk->n)) { debug("%.100s, line %lu: bad key syntax", SSH_USER_PERMITTED_KEYS, linenum); packet_send_debug("%.100s, line %lu: bad key syntax", @@ -252,19 +245,20 @@ auth_rsa(struct passwd *pw, BIGNUM *client_n) /* cp now points to the comment part. */ /* Check if the we have found the desired key (identified by its modulus). */ - if (BN_cmp(n, client_n) != 0) + if (BN_cmp(pk->n, client_n) != 0) continue; /* check the real bits */ - if (bits != BN_num_bits(n)) + if (bits != BN_num_bits(pk->n)) log("Warning: %s, line %ld: keysize mismatch: " "actual %d vs. announced %d.", - file, linenum, BN_num_bits(n), bits); + file, linenum, BN_num_bits(pk->n), bits); /* We have found the desired key. */ + /* Perform the challenge-response dialog for this key. */ - if (!auth_rsa_challenge_dialog(e, n)) { + if (!auth_rsa_challenge_dialog(pk)) { /* Wrong response. */ verbose("Wrong response to RSA authentication challenge."); packet_send_debug("Wrong response to RSA authentication challenge."); @@ -467,8 +461,7 @@ auth_rsa(struct passwd *pw, BIGNUM *client_n) /* Close the file. */ fclose(f); - BN_clear_free(n); - BN_clear_free(e); + RSA_free(pk); if (authenticated) packet_send_debug("RSA authentication accepted."); diff --git a/crypto/openssh/bufaux.c b/crypto/openssh/bufaux.c index 4e25768..6a0c559 100644 --- a/crypto/openssh/bufaux.c +++ b/crypto/openssh/bufaux.c @@ -16,7 +16,7 @@ */ #include "includes.h" -RCSID("$Id: bufaux.c,v 1.7 1999/11/24 19:53:44 markus Exp $"); +RCSID("$Id: bufaux.c,v 1.8 2000/03/16 20:56:14 markus Exp $"); #include "ssh.h" #include <openssl/bn.h> @@ -33,7 +33,7 @@ buffer_put_bignum(Buffer *buffer, BIGNUM *value) { int bits = BN_num_bits(value); int bin_size = (bits + 7) / 8; - char *buf = xmalloc(bin_size); + char unsigned *buf = xmalloc(bin_size); int oi; char msg[2]; @@ -47,7 +47,7 @@ buffer_put_bignum(Buffer *buffer, BIGNUM *value) PUT_16BIT(msg, bits); buffer_append(buffer, msg, 2); /* Store the binary data. */ - buffer_append(buffer, buf, oi); + buffer_append(buffer, (char *)buf, oi); memset(buf, 0, bin_size); xfree(buf); @@ -69,7 +69,7 @@ buffer_get_bignum(Buffer *buffer, BIGNUM *value) bytes = (bits + 7) / 8; if (buffer_len(buffer) < bytes) fatal("buffer_get_bignum: input buffer too small"); - bin = buffer_ptr(buffer); + bin = (unsigned char*) buffer_ptr(buffer); BN_bin2bn(bin, bytes, value); buffer_consume(buffer, bytes); diff --git a/crypto/openssh/cipher.c b/crypto/openssh/cipher.c index e3698f0..3ad4c73 100644 --- a/crypto/openssh/cipher.c +++ b/crypto/openssh/cipher.c @@ -13,7 +13,7 @@ */ #include "includes.h" -RCSID("$Id: cipher.c,v 1.19 2000/02/22 15:19:29 markus Exp $"); +RCSID("$Id: cipher.c,v 1.20 2000/03/22 09:55:10 markus Exp $"); #include "ssh.h" #include "cipher.h" @@ -105,18 +105,6 @@ swap_bytes(const unsigned char *src, unsigned char *dst_, int n) } } -void (*cipher_attack_detected) (const char *fmt,...) = fatal; - -static inline void -detect_cbc_attack(const unsigned char *src, - unsigned int len) -{ - return; - - log("CRC-32 CBC insertion attack detected"); - cipher_attack_detected("CRC-32 CBC insertion attack detected"); -} - /* * Names of all encryption algorithms. * These must match the numbers defined in cipher.h. @@ -299,7 +287,6 @@ cipher_decrypt(CipherContext *context, unsigned char *dest, break; case SSH_CIPHER_3DES: - /* CRC-32 attack? */ SSH_3CBC_DECRYPT(context->u.des3.key1, context->u.des3.key2, &context->u.des3.iv2, context->u.des3.key3, &context->u.des3.iv3, @@ -307,7 +294,6 @@ cipher_decrypt(CipherContext *context, unsigned char *dest, break; case SSH_CIPHER_BLOWFISH: - detect_cbc_attack(src, len); swap_bytes(src, dest, len); BF_cbc_encrypt((void *) dest, dest, len, &context->u.bf.key, context->u.bf.iv, diff --git a/crypto/openssh/cipher.h b/crypto/openssh/cipher.h index bb87f88..492dda3 100644 --- a/crypto/openssh/cipher.h +++ b/crypto/openssh/cipher.h @@ -12,7 +12,7 @@ * $FreeBSD$ */ -/* RCSID("$Id: cipher.h,v 1.10 1999/11/24 19:53:46 markus Exp $"); */ +/* RCSID("$Id: cipher.h,v 1.11 2000/03/22 09:55:10 markus Exp $"); */ #ifndef CIPHER_H #define CIPHER_H @@ -89,10 +89,4 @@ void cipher_decrypt(CipherContext * context, unsigned char *dest, const unsigned char *src, unsigned int len); -/* - * If and CRC-32 attack is detected this function is called. Defaults to - * fatal, changed to packet_disconnect in sshd and ssh. - */ -extern void (*cipher_attack_detected) (const char *fmt, ...); - #endif /* CIPHER_H */ diff --git a/crypto/openssh/fingerprint.c b/crypto/openssh/fingerprint.c index cf75788..c219abb 100644 --- a/crypto/openssh/fingerprint.c +++ b/crypto/openssh/fingerprint.c @@ -30,7 +30,7 @@ */ #include "includes.h" -RCSID("$Id: fingerprint.c,v 1.4 1999/11/24 16:15:25 markus Exp $"); +RCSID("$Id: fingerprint.c,v 1.5 2000/03/16 20:56:14 markus Exp $"); #include "ssh.h" #include "xmalloc.h" @@ -48,7 +48,7 @@ fingerprint(BIGNUM *e, BIGNUM *n) static char retval[80]; MD5_CTX md; unsigned char d[16]; - char *buf; + unsigned char *buf; int nlen, elen; nlen = BN_num_bytes(n); diff --git a/crypto/openssh/packet.h b/crypto/openssh/packet.h index 41f9557..791b354 100644 --- a/crypto/openssh/packet.h +++ b/crypto/openssh/packet.h @@ -14,7 +14,7 @@ * $FreeBSD$ */ -/* RCSID("$Id: packet.h,v 1.9 2000/01/04 16:54:58 markus Exp $"); */ +/* RCSID("$Id: packet.h,v 1.10 2000/03/16 20:56:14 markus Exp $"); */ #ifndef PACKET_H #define PACKET_H @@ -145,7 +145,7 @@ char *packet_get_string(unsigned int *length_ptr); * The error message should not contain a newline. The total length of the * message must not exceed 1024 bytes. */ -void packet_disconnect(const char *fmt,...) __attribute__((format(printf, 1, 2)));; +void packet_disconnect(const char *fmt,...) __attribute__((format(printf, 1, 2))); /* * Sends a diagnostic message to the other side. This message can be sent at @@ -157,7 +157,7 @@ void packet_disconnect(const char *fmt,...) __attribute__((format(printf, 1, * remote side protocol flags do not indicate that it supports SSH_MSG_DEBUG, * this will do nothing. */ -void packet_send_debug(const char *fmt,...) __attribute__((format(printf, 1, 2)));; +void packet_send_debug(const char *fmt,...) __attribute__((format(printf, 1, 2))); /* Checks if there is any buffered output, and tries to write some of the output. */ void packet_write_poll(void); diff --git a/crypto/openssh/rsa.c b/crypto/openssh/rsa.c index 6f9c7cd..4098470 100644 --- a/crypto/openssh/rsa.c +++ b/crypto/openssh/rsa.c @@ -37,7 +37,7 @@ */ #include "includes.h" -RCSID("$Id: rsa.c,v 1.12 2000/02/21 21:47:31 markus Exp $"); +RCSID("$Id: rsa.c,v 1.13 2000/03/16 20:56:14 markus Exp $"); #include "rsa.h" #include "ssh.h" @@ -112,7 +112,7 @@ rsa_generate_key(RSA *prv, RSA *pub, unsigned int bits) void rsa_public_encrypt(BIGNUM *out, BIGNUM *in, RSA *key) { - char *inbuf, *outbuf; + unsigned char *inbuf, *outbuf; int len, ilen, olen; if (BN_num_bits(key->e) < 2 || !BN_is_odd(key->e)) @@ -143,7 +143,7 @@ rsa_public_encrypt(BIGNUM *out, BIGNUM *in, RSA *key) void rsa_private_decrypt(BIGNUM *out, BIGNUM *in, RSA *key) { - char *inbuf, *outbuf; + unsigned char *inbuf, *outbuf; int len, ilen, olen; olen = BN_num_bytes(key->n); diff --git a/crypto/openssh/servconf.c b/crypto/openssh/servconf.c index 32f04c7..0fcd4ee 100644 --- a/crypto/openssh/servconf.c +++ b/crypto/openssh/servconf.c @@ -13,7 +13,7 @@ */ #include "includes.h" -RCSID("$Id: servconf.c,v 1.30 2000/02/24 18:22:16 markus Exp $"); +RCSID("$Id: servconf.c,v 1.31 2000/03/07 20:40:41 markus Exp $"); #include "ssh.h" #include "servconf.h" @@ -102,7 +102,7 @@ fill_default_server_options(ServerOptions *options) if (options->print_motd == -1) options->print_motd = 1; if (options->x11_forwarding == -1) - options->x11_forwarding = 1; + options->x11_forwarding = 0; if (options->x11_display_offset == -1) options->x11_display_offset = 10; if (options->strict_modes == -1) diff --git a/crypto/openssh/ssh-agent.c b/crypto/openssh/ssh-agent.c index b15d998..cd573b0 100644 --- a/crypto/openssh/ssh-agent.c +++ b/crypto/openssh/ssh-agent.c @@ -1,4 +1,4 @@ -/* $OpenBSD: ssh-agent.c,v 1.25 2000/01/02 21:51:03 markus Exp $ */ +/* $OpenBSD: ssh-agent.c,v 1.26 2000/03/16 20:56:14 markus Exp $ */ /* * Author: Tatu Ylonen <ylo@cs.hut.fi> @@ -11,7 +11,7 @@ */ #include "includes.h" -RCSID("$OpenBSD: ssh-agent.c,v 1.25 2000/01/02 21:51:03 markus Exp $"); +RCSID("$OpenBSD: ssh-agent.c,v 1.26 2000/03/16 20:56:14 markus Exp $"); #include "ssh.h" #include "rsa.h" @@ -410,6 +410,7 @@ after_select(fd_set *readset, fd_set *writeset) { unsigned int i; int len, sock; + socklen_t slen; char buf[1024]; struct sockaddr_un sunaddr; @@ -419,8 +420,8 @@ after_select(fd_set *readset, fd_set *writeset) break; case AUTH_SOCKET: if (FD_ISSET(sockets[i].fd, readset)) { - len = sizeof(sunaddr); - sock = accept(sockets[i].fd, (struct sockaddr *) & sunaddr, &len); + slen = sizeof(sunaddr); + sock = accept(sockets[i].fd, (struct sockaddr *) & sunaddr, &slen); if (sock < 0) { perror("accept from AUTH_SOCKET"); break; diff --git a/crypto/openssh/ssh.1 b/crypto/openssh/ssh.1 index 49a1613..caee364 100644 --- a/crypto/openssh/ssh.1 +++ b/crypto/openssh/ssh.1 @@ -9,7 +9,7 @@ .\" .\" Created: Sat Apr 22 21:55:14 1995 ylo .\" -.\" $Id: ssh.1,v 1.38 2000/02/28 19:51:58 markus Exp $ +.\" $Id: ssh.1,v 1.43 2000/03/24 03:04:46 brad Exp $ .\" $FreeBSD$ .\" .Dd September 25, 1999 @@ -53,9 +53,11 @@ .Sh DESCRIPTION .Nm (Secure Shell) is a program for logging into a remote machine and for -executing commands on a remote machine. It is intended to replace +executing commands on a remote machine. +It is intended to replace rlogin and rsh, and provide secure encrypted communications between -two untrusted hosts over an insecure network. X11 connections and +two untrusted hosts over an insecure network. +X11 connections and arbitrary TCP/IP ports can also be forwarded over the secure channel. .Pp .Nm @@ -77,15 +79,16 @@ or exists in the user's home directory on the remote machine and contains a line containing the name of the client machine and the name of the user on that machine, the user is -permitted to log in. This form of authentication alone is normally not +permitted to log in. +This form of authentication alone is normally not allowed by the server because it is not secure. .Pp The second (and primary) authentication method is the .Pa rhosts or .Pa hosts.equiv -method combined with RSA-based host authentication. It -means that if the login would be permitted by +method combined with RSA-based host authentication. +It means that if the login would be permitted by .Pa \&.rhosts , .Pa \&.shosts , .Pa /etc/hosts.equiv , @@ -98,10 +101,10 @@ and .Pa $HOME/.ssh/known_hosts in the .Sx FILES -section), only then login is -permitted. This authentication method closes security holes due to IP -spoofing, DNS spoofing and routing spoofing. [Note to the -administrator: +section), only then login is permitted. +This authentication method closes security holes due to IP +spoofing, DNS spoofing and routing spoofing. +[Note to the administrator: .Pa /etc/hosts.equiv , .Pa \&.rhosts , and the rlogin/rsh protocol in general, are inherently insecure and should be @@ -113,34 +116,39 @@ supports RSA based authentication. The scheme is based on public-key cryptography: there are cryptosystems where encryption and decryption are done using separate keys, and it is not possible to derive the decryption key from the encryption key. -RSA is one such system. The idea is that each user creates a public/private -key pair for authentication purposes. The -server knows the public key, and only the user knows the private key. -The file +RSA is one such system. +The idea is that each user creates a public/private +key pair for authentication purposes. +The server knows the public key, and only the user knows the private key. +The file .Pa $HOME/.ssh/authorized_keys lists the public keys that are permitted for logging -in. When the user logs in, the +in. +When the user logs in, the .Nm program tells the server which key pair it would like to use for -authentication. The server checks if this key is permitted, and if +authentication. +The server checks if this key is permitted, and if so, sends the user (actually the .Nm program running on behalf of the user) a challenge, a random number, -encrypted by the user's public key. The challenge can only be -decrypted using the proper private key. The user's client then decrypts the +encrypted by the user's public key. +The challenge can only be +decrypted using the proper private key. +The user's client then decrypts the challenge using the private key, proving that he/she knows the private key but without disclosing it to the server. .Pp .Nm -implements the RSA authentication protocol automatically. The user -creates his/her RSA key pair by running +implements the RSA authentication protocol automatically. +The user creates his/her RSA key pair by running .Xr ssh-keygen 1 . This stores the private key in .Pa \&.ssh/identity and the public key in .Pa \&.ssh/identity.pub -in the user's home directory. The user should then -copy the +in the user's home directory. +The user should then copy the .Pa identity.pub to .Pa \&.ssh/authorized_keys @@ -149,24 +157,28 @@ in his/her home directory on the remote machine (the file corresponds to the conventional .Pa \&.rhosts file, and has one key -per line, though the lines can be very long). After this, the user -can log in without giving the password. RSA authentication is much +per line, though the lines can be very long). +After this, the user can log in without giving the password. +RSA authentication is much more secure than rhosts authentication. .Pp The most convenient way to use RSA authentication may be with an -authentication agent. See +authentication agent. +See .Xr ssh-agent 1 for more information. .Pp If other authentication methods fail, .Nm -prompts the user for a password. The password is sent to the remote +prompts the user for a password. +The password is sent to the remote host for checking; however, since all communications are encrypted, the password cannot be seen by someone listening on the network. .Pp When the user's identity has been accepted by the server, the server either executes the given command, or logs into the machine and gives -the user a normal shell on the remote machine. All communication with +the user a normal shell on the remote machine. +All communication with the remote command or shell will be automatically encrypted. .Pp If a pseudo-terminal has been allocated (normal login session), the @@ -183,19 +195,22 @@ the session blocks waiting for forwarded X11 or TCP/IP connections to terminate, it can be backgrounded with .Ic ~& (this should not be used while the user shell is active, as it can cause the -shell to hang). All available escapes can be listed with +shell to hang). +All available escapes can be listed with .Ic ~? . .Pp A single tilde character can be sent as .Ic ~~ (or by following the tilde by a character other than those described above). The escape character must always follow a newline to be interpreted as -special. The escape character can be changed in configuration files +special. +The escape character can be changed in configuration files or on the command line. .Pp If no pseudo tty has been allocated, the session is transparent and can be used to reliably transfer binary -data. On most systems, setting the escape character to +data. +On most systems, setting the escape character to .Dq none will also make the session transparent even if a tty is used. .Pp @@ -211,7 +226,8 @@ environment variable is set), the connection to the X11 display is automatically forwarded to the remote side in such a way that any X11 programs started from the shell (or command) will go through the encrypted channel, and the connection to the real X server will be made -from the local machine. The user should not manually set +from the local machine. +The user should not manually set .Ev DISPLAY . Forwarding of X11 connections can be configured on the command line or in configuration files. @@ -221,7 +237,8 @@ The value set by .Nm will point to the server machine, but with a display number greater -than zero. This is normal, and happens because +than zero. +This is normal, and happens because .Nm creates a .Dq proxy @@ -233,7 +250,8 @@ will also automatically set up Xauthority data on the server machine. For this purpose, it will generate a random authorization cookie, store it in Xauthority on the server, and verify that any forwarded connections carry this cookie and replace it by the real cookie when -the connection is opened. The real authentication cookie is never +the connection is opened. +The real authentication cookie is never sent to the server machine (and no cookies are sent in the plain). .Pp If the user is using an authentication agent, the connection to the agent @@ -241,37 +259,42 @@ is automatically forwarded to the remote side unless disabled on command line or in a configuration file. .Pp Forwarding of arbitrary TCP/IP connections over the secure channel can -be specified either on command line or in a configuration file. One -possible application of TCP/IP forwarding is a secure connection to an -electronic purse; another is going through firewalls. +be specified either on command line or in a configuration file. +One possible application of TCP/IP forwarding is a secure connection to an +electronic purse; another is going trough firewalls. .Pp .Nm automatically maintains and checks a database containing RSA-based -identifications for all hosts it has ever been used with. The -database is stored in +identifications for all hosts it has ever been used with. +The database is stored in .Pa \&.ssh/known_hosts -in the user's home directory. Additionally, the file +in the user's home directory. +Additionally, the file .Pa /etc/ssh/ssh_known_hosts -is automatically checked for known hosts. Any new hosts are -automatically added to the user's file. If a host's identification +is automatically checked for known hosts. +Any new hosts are automatically added to the user's file. +If a host's identification ever changes, .Nm warns about this and disables password authentication to prevent a -trojan horse from getting the user's password. Another purpose of +trojan horse from getting the user's password. +Another purpose of this mechanism is to prevent man-in-the-middle attacks which could -otherwise be used to circumvent the encryption. The +otherwise be used to circumvent the encryption. +The .Cm StrictHostKeyChecking option (see below) can be used to prevent logins to machines whose host key is not known or has changed. .Sh OPTIONS .Bl -tag -width Ds .It Fl a -Disables forwarding of the authentication agent connection. This may -also be specified on a per-host basis in the configuration file. +Disables forwarding of the authentication agent connection. +This may also be specified on a per-host basis in the configuration file. .It Fl c Ar blowfish|3des Selects the cipher to use for encrypting the session. .Ar 3des -is used by default. It is believed to be secure. +is used by default. +It is believed to be secure. .Ar 3des (triple-des) is an encrypt-decrypt-encrypt triple with three different keys. It is presumably more secure than the @@ -283,22 +306,24 @@ is a fast block cipher, it appears very secure and is much faster than .It Fl e Ar ch|^ch|none Sets the escape character for sessions with a pty (default: .Ql ~ ) . -The escape character is only recognized at the beginning of a line. The -escape character followed by a dot +The escape character is only recognized at the beginning of a line. +The escape character followed by a dot .Pq Ql \&. closes the connection, followed by control-Z suspends the connection, and followed by itself sends the -escape character once. Setting the character to +escape character once. +Setting the character to .Dq none disables any escapes and makes the session fully transparent. .It Fl f Requests .Nm -to go to background just before command execution. This is useful -if +to go to background just before command execution. +This is useful if .Nm is going to ask for passwords or passphrases, but the user -wants it in the background. This implies +wants it in the background. +This implies .Fl n . The recommended way to start X11 programs at a remote site is with something like @@ -306,29 +331,32 @@ something like .It Fl g Allows remote hosts to connect to local forwarded ports. .It Fl i Ar identity_file -Selects the file from which the identity (private key) for -RSA authentication is read. Default is +Selects the file from which the identity (private key) for +RSA authentication is read. +Default is .Pa \&.ssh/identity -in the user's home directory. Identity files may also be specified on -a per-host basis in the configuration file. It is possible to have -multiple +in the user's home directory. +Identity files may also be specified on +a per-host basis in the configuration file. +It is possible to have multiple .Fl i options (and multiple identities specified in configuration files). .It Fl k -Disables forwarding of Kerberos tickets and AFS tokens. This may -also be specified on a per-host basis in the configuration file. +Disables forwarding of Kerberos tickets and AFS tokens. +This may also be specified on a per-host basis in the configuration file. .It Fl l Ar login_name -Specifies the user to log in as on the remote machine. This may also -be specified on a per-host basis in the configuration file. +Specifies the user to log in as on the remote machine. +This also may be specified on a per-host basis in the configuration file. .It Fl n Redirects stdin from .Pa /dev/null (actually, prevents reading from stdin). This must be used when .Nm -is run in the background. A common trick is to use this to run X11 -programs in a remote machine. For example, +is run in the background. +A common trick is to use this to run X11 programs on a remote machine. +For example, .Ic ssh -n shadows.cs.hut.fi emacs & will start an emacs on shadows.cs.hut.fi, and the X11 connection will be automatically forwarded over an encrypted channel. @@ -343,10 +371,11 @@ option.) .It Fl o Ar option Can be used to give options in the format used in the config file. This is useful for specifying options for which there is no separate -command-line flag. The option has the same format as a line in the -configuration file. +command-line flag. +The option has the same format as a line in the configuration file. .It Fl p Ar port -Port to connect to on the remote host. This can be specified on a +Port to connect to on the remote host. +This can be specified on a per-host basis in the configuration file. .It Fl P Use a non-privileged port for outgoing connections. @@ -357,35 +386,40 @@ Note that this option turns off and .Cm RhostsRSAAuthentication . .It Fl q -Quiet mode. Causes all warning and diagnostic messages to be -suppressed. Only fatal errors are displayed. +Quiet mode. +Causes all warning and diagnostic messages to be suppressed. +Only fatal errors are displayed. .It Fl t -Force pseudo-tty allocation. This can be used to execute arbitrary -screen-based programs on a remote machine, which can be very useful -e.g. when implementing menu services. +Force pseudo-tty allocation. +This can be used to execute arbitrary +screen-based programs on a remote machine, which can be very useful, +e.g., when implementing menu services. .It Fl v -Verbose mode. Causes +Verbose mode. +Causes .Nm -to print debugging messages about its progress. This is helpful in +to print debugging messages about its progress. +This is helpful in debugging connection, authentication, and configuration problems. The verbose mode is also used to display .Xr skey 1 challenges, if the user entered "s/key" as password. .It Fl x -Disables X11 forwarding. This can also be specified on a per-host -basis in a configuration file. +Disables X11 forwarding. +This can also be specified on a per-host basis in a configuration file. .It Fl X Enables X11 forwarding. .It Fl C Requests compression of all data (including stdin, stdout, stderr, and -data for forwarded X11 and TCP/IP connections). The compression -algorithm is the same used by +data for forwarded X11 and TCP/IP connections). +The compression algorithm is the same used by .Xr gzip 1 , and the .Dq level can be controlled by the .Cm CompressionLevel -option (see below). Compression is desirable on modem lines and other +option (see below). +Compression is desirable on modem lines and other slow connections, but will only slow down things on fast networks. The default value can be set on a host-by-host basis in the configuration files; see the @@ -393,8 +427,8 @@ configuration files; see the option below. .It Fl L Ar port:host:hostport Specifies that the given port on the local (client) host is to be -forwarded to the given host and port on the remote side. This works -by allocating a socket to listen to +forwarded to the given host and port on the remote side. +This works by allocating a socket to listen to .Ar port on the local side, and whenever a connection is made to this port, the connection is forwarded over the secure channel, and a connection is @@ -402,14 +436,15 @@ made to .Ar host port .Ar hostport -from the remote machine. Port forwardings can also be specified in the -configuration file. Only root can forward privileged ports. +from the remote machine. +Port forwardings can also be specified in the configuration file. +Only root can forward privileged ports. IPv6 addresses can be specified with an alternative syntax: .Ar port/host/hostport .It Fl R Ar port:host:hostport Specifies that the given port on the remote (server) host is to be -forwarded to the given host and port on the local side. This works -by allocating a socket to listen to +forwarded to the given host and port on the local side. +This works by allocating a socket to listen to .Ar port on the remote side, and whenever a connection is made to this port, the connection is forwarded over the secure channel, and a connection is @@ -417,8 +452,9 @@ made to .Ar host port .Ar hostport -from the local machine. Port forwardings can also be specified in the -configuration file. Privileged ports can be forwarded only when +from the local machine. +Port forwardings can also be specified in the configuration file. +Privileged ports can be forwarded only when logging in as root on the remote machine. .It Fl 4 Forces @@ -437,10 +473,12 @@ command line options, user's configuration file and system-wide configuration file .Pq Pa /etc/ssh/ssh_config . For each parameter, the first obtained value -will be used. The configuration files contain sections bracketed by -"Host" specifications, and that section is only applied for hosts that -match one of the patterns given in the specification. The matched -host name is the one given on the command line. +will be used. +The configuration files contain sections bracketed by +.Dq Host +specifications, and that section is only applied for hosts that +match one of the patterns given in the specification. +The matched host name is the one given on the command line. .Pp Since the first obtained value for each parameter is used, more host-specific declarations should be given near the beginning of the @@ -467,25 +505,28 @@ given after the keyword. and .Ql ? can be used as wildcards in the -patterns. A single +patterns. +A single .Ql \&* as a pattern can be used to provide global -defaults for all hosts. The host is the +defaults for all hosts. +The host is the .Ar hostname argument given on the command line (i.e., the name is not converted to a canonicalized host name before matching). .It Cm AFSTokenPassing -Specifies whether to pass AFS tokens to remote host. The argument to -this keyword must be +Specifies whether to pass AFS tokens to remote host. +The argument to this keyword must be .Dq yes or .Dq no . .It Cm BatchMode If set to .Dq yes , -passphrase/password querying will be disabled. This -option is useful in scripts and other batch jobs where you have no -user to supply the password. The argument must be +passphrase/password querying will be disabled. +This option is useful in scripts and other batch jobs where you have no +user to supply the password. +The argument must be .Dq yes or .Dq no . @@ -494,38 +535,43 @@ If this flag is set to .Dq yes , ssh will additionally check the host ip address in the .Pa known_hosts -file. This allows ssh to detect if a host key changed due to DNS spoofing. +file. +This allows ssh to detect if a host key changed due to DNS spoofing. If the option is set to .Dq no , the check will not be executed. .It Cm Cipher -Specifies the cipher to use for encrypting the session. Currently, +Specifies the cipher to use for encrypting the session. +Currently, .Dq blowfish , and .Dq 3des -are supported. The default is +are supported. +The default is .Dq 3des . .It Cm Compression -Specifies whether to use compression. The argument must be +Specifies whether to use compression. +The argument must be .Dq yes or .Dq no . .It Cm CompressionLevel -Specifies the compression level to use if compression is enable. The -argument must be an integer from 1 (fast) to 9 (slow, best). The -default level is 6, which is good for most applications. The meaning -of the values is the same as in +Specifies the compression level to use if compression is enable. +The argument must be an integer from 1 (fast) to 9 (slow, best). +The default level is 6, which is good for most applications. +The meaning of the values is the same as in .Xr gzip 1 . .It Cm ConnectionAttempts Specifies the number of tries (one per second) to make before falling -back to rsh or exiting. The argument must be an integer. This may be -useful in scripts if the connection sometimes fails. +back to rsh or exiting. +The argument must be an integer. +This may be useful in scripts if the connection sometimes fails. .It Cm EscapeChar Sets the escape character (default: .Ql ~ ) . The escape character can also -be set on the command line. The argument should be a single -character, +be set on the command line. +The argument should be a single character, .Ql ^ followed by a letter, or .Dq none @@ -540,13 +586,15 @@ fails due to a connection refused error (there is no listening on the remote host), .Xr rsh 1 should automatically be used instead (after a suitable warning about -the session being unencrypted). The argument must be +the session being unencrypted). +The argument must be .Dq yes or .Dq no . .It Cm ForwardAgent Specifies whether the connection to the authentication agent (if any) -will be forwarded to the remote machine. The argument must be +will be forwarded to the remote machine. +The argument must be .Dq yes or .Dq no . @@ -554,7 +602,8 @@ or Specifies whether X11 connections will be automatically redirected over the secure channel and .Ev DISPLAY -set. The argument must be +set. +The argument must be .Dq yes or .Dq no . @@ -573,10 +622,10 @@ The default is Specifies a file to use instead of .Pa /etc/ssh/ssh_known_hosts . .It Cm HostName -Specifies the real host name to log into. This can be used to specify -nicknames or abbreviations for hosts. Default is the name given on the -command line. Numeric IP addresses are also permitted (both on the -command line and in +Specifies the real host name to log into. +This can be used to specify nicknames or abbreviations for hosts. +Default is the name given on the command line. +Numeric IP addresses are also permitted (both on the command line and in .Cm HostName specifications). .It Cm IdentityFile @@ -585,80 +634,89 @@ is read (default .Pa .ssh/identity in the user's home directory). Additionally, any identities represented by the authentication agent -will be used for authentication. The file name may use the tilde -syntax to refer to a user's home directory. It is possible to have +will be used for authentication. +The file name may use the tilde +syntax to refer to a user's home directory. +It is possible to have multiple identity files specified in configuration files; all these identities will be tried in sequence. .It Cm KeepAlive Specifies whether the system should send keepalive messages to the -other side. If they are sent, death of the connection or crash of one -of the machines will be properly noticed. However, this means that +other side. +If they are sent, death of the connection or crash of one +of the machines will be properly noticed. +However, this means that connections will die if the route is down temporarily, and some people find it annoying. .Pp The default is .Dq yes (to send keepalives), and the client will notice -if the network goes down or the remote host dies. This is important -in scripts, and many users want it too. +if the network goes down or the remote host dies. +This is important in scripts, and many users want it too. .Pp To disable keepalives, the value should be set to .Dq no in both the server and the client configuration files. .It Cm KerberosAuthentication -Specifies whether Kerberos authentication will be used. The argument to -this keyword must be +Specifies whether Kerberos authentication will be used. +The argument to this keyword must be .Dq yes or .Dq no . .It Cm KerberosTgtPassing -Specifies whether a Kerberos TGT will be forwarded to the server. This -will only work if the Kerberos server is actually an AFS kaserver. The -argument to this keyword must be +Specifies whether a Kerberos TGT will be forwarded to the server. +This will only work if the Kerberos server is actually an AFS kaserver. +The argument to this keyword must be .Dq yes or .Dq no . .It Cm LocalForward Specifies that a TCP/IP port on the local machine be forwarded over -the secure channel to given host:port from the remote machine. The -first argument must be a port number, and the second must be -host:port. Multiple forwardings may be specified, and additional -forwardings can be given on the command line. Only the root can -forward privileged ports. +the secure channel to given host:port from the remote machine. +The first argument must be a port number, and the second must be +host:port. +Multiple forwardings may be specified, and additional +forwardings can be given on the command line. +Only the superuser can forward privileged ports. .It Cm LogLevel Gives the verbosity level that is used when logging messages from .Nm ssh . The possible values are: -QUIET, FATAL, ERROR, INFO, CHAT and DEBUG. +QUIET, FATAL, ERROR, INFO, VERBOSE and DEBUG. The default is INFO. .It Cm NumberOfPasswordPrompts -Specifies the number of password prompts before giving up. The -argument to this keyword must be an integer. Default is 3. +Specifies the number of password prompts before giving up. +The argument to this keyword must be an integer. +Default is 3. .It Cm PasswordAuthentication -Specifies whether to use password authentication. The argument to -this keyword must be +Specifies whether to use password authentication. +The argument to this keyword must be .Dq yes or .Dq no . .It Cm Port -Specifies the port number to connect on the remote host. Default is -22. +Specifies the port number to connect on the remote host. +Default is 22. .It Cm ProxyCommand -Specifies the command to use to connect to the server. The command +Specifies the command to use to connect to the server. +The command string extends to the end of the line, and is executed with .Pa /bin/sh . In the command string, -.Dq %h +.Ql %h will be substituted by the host name to connect and -.Dq %p -by the port. The command can be basically anything, -and should read from its stdin and write to its stdout. It should -eventually connect an +.Ql %p +by the port. +The command can be basically anything, +and should read from its standard input and write to its standard output. +It should eventually connect an .Xr sshd 8 server running on some machine, or execute .Ic sshd -i -somewhere. Host key management will be done using the +somewhere. +Host key management will be done using the HostName of the host being connected (defaulting to the name typed by the user). Note that @@ -667,32 +725,37 @@ is not available for connects with a proxy command. .Pp .It Cm RemoteForward Specifies that a TCP/IP port on the remote machine be forwarded over -the secure channel to given host:port from the local machine. The -first argument must be a port number, and the second must be -host:port. Multiple forwardings may be specified, and additional -forwardings can be given on the command line. Only the root can -forward privileged ports. +the secure channel to given host:port from the local machine. +The first argument must be a port number, and the second must be +host:port. +Multiple forwardings may be specified, and additional +forwardings can be given on the command line. +Only the superuser can forward privileged ports. .It Cm RhostsAuthentication -Specifies whether to try rhosts based authentication. Note that this +Specifies whether to try rhosts based authentication. +Note that this declaration only affects the client side and has no effect whatsoever -on security. Disabling rhosts authentication may reduce +on security. +Disabling rhosts authentication may reduce authentication time on slow connections when rhosts authentication is -not used. Most servers do not permit RhostsAuthentication because it -is not secure (see RhostsRSAAuthentication). The argument to this -keyword must be +not used. +Most servers do not permit RhostsAuthentication because it +is not secure (see RhostsRSAAuthentication). +The argument to this keyword must be .Dq yes or .Dq no . .It Cm RhostsRSAAuthentication Specifies whether to try rhosts based authentication with RSA host -authentication. This is the primary authentication method for most -sites. The argument must be +authentication. +This is the primary authentication method for most sites. +The argument must be .Dq yes or .Dq no . .It Cm RSAAuthentication -Specifies whether to try RSA authentication. The argument to this -keyword must be +Specifies whether to try RSA authentication. +The argument to this keyword must be .Dq yes or .Dq no . @@ -702,8 +765,8 @@ running. .It Cm SkeyAuthentication Specifies whether to use .Xr skey 1 -authentication. The argument to -this keyword must be +authentication. +The argument to this keyword must be .Dq yes or .Dq no . @@ -715,16 +778,19 @@ If this flag is set to .Nm ssh will never automatically add host keys to the .Pa $HOME/.ssh/known_hosts -file, and refuses to connect hosts whose host key has changed. This -provides maximum protection against trojan horse attacks. However, it -can be somewhat annoying if you don't have good +file, and refuses to connect hosts whose host key has changed. +This provides maximum protection against trojan horse attacks. +However, it can be somewhat annoying if you don't have good .Pa /etc/ssh/ssh_known_hosts files installed and frequently -connect new hosts. Basically this option forces the user to manually -add any new hosts. Normally this option is disabled, and new hosts -will automatically be added to the known host files. The host keys of -known hosts will be verified automatically in either case. The -argument must be +connect new hosts. +Basically this option forces the user to manually +add any new hosts. +Normally this option is disabled, and new hosts +will automatically be added to the known host files. +The host keys of +known hosts will be verified automatically in either case. +The argument must be .Dq yes or .Dq no . @@ -743,23 +809,26 @@ turns off and .Cm RhostsRSAAuthentication . .It Cm User -Specifies the user to log in as. This can be useful if you have a -different user name in different machines. This saves the trouble of +Specifies the user to log in as. +This can be useful if you have a different user name on different machines. +This saves the trouble of having to remember to give the user name on the command line. .It Cm UserKnownHostsFile Specifies a file to use instead of .Pa $HOME/.ssh/known_hosts . .It Cm UseRsh -Specifies that rlogin/rsh should be used for this host. It is -possible that the host does not at all support the +Specifies that rlogin/rsh should be used for this host. +It is possible that the host does not at all support the .Nm -protocol. This causes +protocol. +This causes .Nm -to immediately exec +to immediately execute .Xr rsh 1 . All other options (except .Cm HostName ) -are ignored if this has been specified. The argument must be +are ignored if this has been specified. +The argument must be .Dq yes or .Dq no . @@ -770,15 +839,17 @@ will normally set the following environment variables: .It Ev DISPLAY The .Ev DISPLAY -variable indicates the location of the X11 server. It is -automatically set by +variable indicates the location of the X11 server. +It is automatically set by .Nm to point to a value of the form .Dq hostname:n where hostname indicates -the host where the shell runs, and n is an integer \*(>= 1. Ssh uses -this special value to forward X11 connections over the secure -channel. The user should normally not set DISPLAY explicitly, as that +the host where the shell runs, and n is an integer \*(>= 1. +.Nm +uses this special value to forward X11 connections over the secure +channel. +The user should normally not set DISPLAY explicitly, as that will render the X11 connection insecure (and will require the user to manually copy any required authorization cookies). .It Ev HOME @@ -789,7 +860,7 @@ Synonym for set for compatibility with systems that use this variable. .It Ev MAIL Set to point the user's mailbox. -.It Ev PATH +.It Ev PATH Set to the default .Ev PATH , as specified when compiling @@ -798,12 +869,14 @@ as specified when compiling indicates the path of a unix-domain socket used to communicate with the agent. .It Ev SSH_CLIENT -Identifies the client end of the connection. The variable contains +Identifies the client end of the connection. +The variable contains three space-separated values: client ip-address, client port number, and server port number. .It Ev SSH_TTY This is set to the name of the tty (path to the device) associated -with the current shell or command. If the current session has no tty, +with the current shell or command. +If the current session has no tty, this variable is not set. .It Ev TZ The timezone variable is set to indicate the present timezone if it @@ -829,7 +902,8 @@ in See .Xr sshd 8 . .It Pa $HOME/.ssh/identity -Contains the RSA authentication identity of the user. This file +Contains the RSA authentication identity of the user. +This file contains sensitive data and should be readable by the user but not accessible by others (read/write/execute). Note that @@ -840,39 +914,50 @@ generating the key; the passphrase will be used to encrypt the sensitive part of this file using 3DES. .It Pa $HOME/.ssh/identity.pub Contains the public key for authentication (public part of the -identity file in human-readable form). The contents of this file -should be added to +identity file in human-readable form). +The contents of this file should be added to .Pa $HOME/.ssh/authorized_keys on all machines -where you wish to log in using RSA authentication. This file is not -sensitive and can (but need not) be readable by anyone. This file is +where you wish to log in using RSA authentication. +This file is not +sensitive and can (but need not) be readable by anyone. +This file is never used automatically and is not necessary; it is only provided for the convenience of the user. .It Pa $HOME/.ssh/config -This is the per-user configuration file. The format of this file is -described above. This file is used by the +This is the per-user configuration file. +The format of this file is described above. +This file is used by the .Nm -client. This file does not usually contain any sensitive information, +client. +This file does not usually contain any sensitive information, but the recommended permissions are read/write for the user, and not accessible by others. .It Pa $HOME/.ssh/authorized_keys -Lists the RSA keys that can be used for logging in as this user. The -format of this file is described in the +Lists the RSA keys that can be used for logging in as this user. +The format of this file is described in the .Xr sshd 8 -manual page. In the simplest form the format is the same as the .pub +manual page. +In the simplest form the format is the same as the .pub identity files (that is, each line contains the number of bits in modulus, public exponent, modulus, and comment fields, separated by -spaces). This file is not highly sensitive, but the recommended +spaces). +This file is not highly sensitive, but the recommended permissions are read/write for the user, and not accessible by others. .It Pa /etc/ssh/ssh_known_hosts -Systemwide list of known host keys. This file should be prepared by the +Systemwide list of known host keys. +This file should be prepared by the system administrator to contain the public host keys of all machines in the -organization. This file should be world-readable. This file contains +organization. +This file should be world-readable. +This file contains public keys, one per line, in the following format (fields separated by spaces): system name, number of bits in modulus, public exponent, -modulus, and optional comment field. When different names are used +modulus, and optional comment field. +When different names are used for the same machine, all such names should be listed, separated by -commas. The format is described on the +commas. +The format is described on the .Xr sshd 8 manual page. .Pp @@ -884,32 +969,37 @@ does not convert the user-supplied name to a canonical name before checking the key, because someone with access to the name servers would then be able to fool host authentication. .It Pa /etc/ssh/ssh_config -Systemwide configuration file. This file provides defaults for those +Systemwide configuration file. +This file provides defaults for those values that are not specified in the user's configuration file, and -for those users who do not have a configuration file. This file must -be world-readable. +for those users who do not have a configuration file. +This file must be world-readable. .It Pa $HOME/.rhosts This file is used in .Pa \&.rhosts authentication to list the -host/user pairs that are permitted to log in. (Note that this file is +host/user pairs that are permitted to log in. +(Note that this file is also used by rlogin and rsh, which makes using this file insecure.) Each line of the file contains a host name (in the canonical form returned by name servers), and then a user name on that host, -separated by a space. One some machines this file may need to be +separated by a space. +One some machines this file may need to be world-readable if the user's home directory is on a NFS partition, because .Xr sshd 8 -reads it as root. Additionally, this file must be owned by the user, -and must not have write permissions for anyone else. The recommended +reads it as root. +Additionally, this file must be owned by the user, +and must not have write permissions for anyone else. +The recommended permission for most machines is read/write for the user, and not accessible by others. .Pp Note that by default .Xr sshd 8 will be installed so that it requires successful RSA host -authentication before permitting \s+2.\s0rhosts authentication. If your -server machine does not have the client's host key in +authentication before permitting \s+2.\s0rhosts authentication. +If your server machine does not have the client's host key in .Pa /etc/ssh/ssh_known_hosts , you can store it in .Pa $HOME/.ssh/known_hosts . @@ -930,16 +1020,20 @@ or .It Pa /etc/hosts.equiv This file is used during .Pa \&.rhosts -authentication. It contains +authentication. +It contains canonical hosts names, one per line (the full format is described on the .Xr sshd 8 -manual page). If the client host is found in this file, login is +manual page). +If the client host is found in this file, login is automatically permitted provided client and server user names are the -same. Additionally, successful RSA host authentication is normally -required. This file should only be writable by root. +same. +Additionally, successful RSA host authentication is normally +required. +This file should only be writable by root. .It Pa /etc/ssh/shosts.equiv -This file is processed exactly as +This file is processed exactly as .Pa /etc/hosts.equiv . This file may be useful to permit logins using .Nm @@ -969,7 +1063,8 @@ is required for proper operation. .Sh AUTHOR OpenSSH is a derivative of the original (free) ssh 1.2.12 release by Tatu Ylonen, -but with bugs removed and newer features re-added. Rapidly after the +but with bugs removed and newer features re-added. +Rapidly after the 1.2.12 release, newer versions of the original ssh bore successively more restrictive licenses, and thus demand for a free version was born. This version of OpenSSH diff --git a/crypto/openssh/ssh.c b/crypto/openssh/ssh.c index cfaab25..149f945 100644 --- a/crypto/openssh/ssh.c +++ b/crypto/openssh/ssh.c @@ -13,7 +13,7 @@ */ #include "includes.h" -RCSID("$Id: ssh.c,v 1.41 2000/02/28 19:51:58 markus Exp $"); +RCSID("$Id: ssh.c,v 1.43 2000/03/23 21:52:02 markus Exp $"); #include "xmalloc.h" #include "ssh.h" @@ -176,6 +176,7 @@ main(int ac, char **av) struct stat st; struct passwd *pw, pwcopy; int interactive = 0, dummy; + int have_pty = 0; uid_t original_effective_uid; int plen; @@ -616,9 +617,6 @@ main(int ac, char **av) if (host_private_key_loaded) RSA_free(host_private_key); /* Destroys contents safely */ - /* Close connection cleanly after attack. */ - cipher_attack_detected = packet_disconnect; - /* Enable compression if requested. */ if (options.compression) { debug("Requesting compression at level %d.", options.compression_level); @@ -670,9 +668,10 @@ main(int ac, char **av) /* Read response from the server. */ type = packet_read(&plen); - if (type == SSH_SMSG_SUCCESS) + if (type == SSH_SMSG_SUCCESS) { interactive = 1; - else if (type == SSH_SMSG_FAILURE) + have_pty = 1; + } else if (type == SSH_SMSG_FAILURE) log("Warning: Remote host failed or refused to allocate a pseudo tty."); else packet_disconnect("Protocol error waiting for pty request response."); @@ -800,7 +799,7 @@ main(int ac, char **av) } /* Enter the interactive session. */ - exit_status = client_loop(tty_flag, tty_flag ? options.escape_char : -1); + exit_status = client_loop(have_pty, tty_flag ? options.escape_char : -1); /* Close the connection to the remote host. */ packet_close(); diff --git a/crypto/openssh/ssh.h b/crypto/openssh/ssh.h index 8d6267c..7b32bda 100644 --- a/crypto/openssh/ssh.h +++ b/crypto/openssh/ssh.h @@ -14,7 +14,7 @@ * $FreeBSD$ */ -/* RCSID("$Id: ssh.h,v 1.33 2000/02/01 22:32:53 d Exp $"); */ +/* RCSID("$Id: ssh.h,v 1.34 2000/03/23 22:15:33 markus Exp $"); */ #ifndef SSH_H #define SSH_H @@ -321,8 +321,7 @@ int auth_rhosts(struct passwd * pw, const char *client_user); * its host key. Returns true if authentication succeeds. */ int -auth_rhosts_rsa(struct passwd * pw, const char *client_user, - BIGNUM * client_host_key_e, BIGNUM * client_host_key_n); +auth_rhosts_rsa(struct passwd * pw, const char *client_user, RSA* client_host_key); /* * Tries to authenticate the user using password. Returns true if @@ -371,40 +370,11 @@ int get_local_port(void); /* - * Tries to match the host name (which must be in all lowercase) against the - * comma-separated sequence of subpatterns (each possibly preceded by ! to - * indicate negation). Returns true if there is a positive match; zero - * otherwise. - */ -int match_hostname(const char *host, const char *pattern, unsigned int len); - -/* - * Checks whether the given host is already in the list of our known hosts. - * Returns HOST_OK if the host is known and has the specified key, HOST_NEW - * if the host is not known, and HOST_CHANGED if the host is known but used - * to have a different host key. The host must be in all lowercase. - */ -typedef enum { - HOST_OK, HOST_NEW, HOST_CHANGED -} HostStatus; -HostStatus -check_host_in_hostfile(const char *filename, const char *host, - BIGNUM * e, BIGNUM * n, BIGNUM * ke, BIGNUM * kn); - -/* - * Appends an entry to the host file. Returns false if the entry could not - * be appended. - */ -int -add_host_to_hostfile(const char *filename, const char *host, - BIGNUM * e, BIGNUM * n); - -/* * Performs the RSA authentication challenge-response dialog with the client, * and returns true (non-zero) if the client gave the correct answer to our * challenge; returns zero if the client gives a wrong answer. */ -int auth_rsa_challenge_dialog(BIGNUM * e, BIGNUM * n); +int auth_rsa_challenge_dialog(RSA *pk); /* * Reads a passphrase from /dev/tty with echo turned off. Returns the diff --git a/crypto/openssh/sshconnect.c b/crypto/openssh/sshconnect.c index bcbd3af..ca5cee2 100644 --- a/crypto/openssh/sshconnect.c +++ b/crypto/openssh/sshconnect.c @@ -10,7 +10,7 @@ */ #include "includes.h" -RCSID("$OpenBSD: sshconnect.c,v 1.56 2000/02/18 08:50:33 markus Exp $"); +RCSID("$OpenBSD: sshconnect.c,v 1.58 2000/03/23 22:15:33 markus Exp $"); #include <openssl/bn.h> #include "xmalloc.h" @@ -23,9 +23,12 @@ RCSID("$OpenBSD: sshconnect.c,v 1.56 2000/02/18 08:50:33 markus Exp $"); #include "uidswap.h" #include "compat.h" #include "readconf.h" -#include "fingerprint.h" +#include <openssl/rsa.h> +#include <openssl/dsa.h> #include <openssl/md5.h> +#include "key.h" +#include "hostfile.h" /* Session id for the current session. */ unsigned char session_id[16]; @@ -634,6 +637,7 @@ try_krb4_authentication() char *realm; CREDENTIALS cred; int r, type, plen; + socklen_t slen; Key_schedule schedule; u_long checksum, cksum; MSG_DAT msg_data; @@ -676,16 +680,16 @@ try_krb4_authentication() /* Zero the buffer. */ (void) memset(auth.dat, 0, MAX_KTXT_LEN); - r = sizeof(local); + slen = sizeof(local); memset(&local, 0, sizeof(local)); if (getsockname(packet_get_connection_in(), - (struct sockaddr *) & local, &r) < 0) + (struct sockaddr *) & local, &slen) < 0) debug("getsockname failed: %s", strerror(errno)); - r = sizeof(foreign); + slen = sizeof(foreign); memset(&foreign, 0, sizeof(foreign)); if (getpeername(packet_get_connection_in(), - (struct sockaddr *) & foreign, &r) < 0) { + (struct sockaddr *) & foreign, &slen) < 0) { debug("getpeername failed: %s", strerror(errno)); fatal_cleanup(); } @@ -747,7 +751,7 @@ send_krb4_tgt() CREDENTIALS *creds; char pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ]; int r, type, plen; - unsigned char buffer[8192]; + char buffer[8192]; struct stat st; /* Don't do anything if we don't have any tickets. */ @@ -768,7 +772,7 @@ send_krb4_tgt() debug("Kerberos V4 ticket expired: %s", TKT_FILE); return 0; } - creds_to_radix(creds, buffer); + creds_to_radix(creds, (unsigned char *)buffer); xfree(creds); packet_start(SSH_CMSG_HAVE_KRB4_TGT); @@ -794,7 +798,7 @@ send_afs_tokens(void) struct ClearToken ct; int i, type, len, plen; char buf[2048], *p, *server_cell; - unsigned char buffer[8192]; + char buffer[8192]; /* Move over ktc_GetToken, here's something leaner. */ for (i = 0; i < 100; i++) { /* just in case */ @@ -836,10 +840,10 @@ send_afs_tokens(void) creds.pinst[0] = '\0'; /* Encode token, ship it off. */ - if (!creds_to_radix(&creds, buffer)) + if (!creds_to_radix(&creds, (unsigned char*) buffer)) break; packet_start(SSH_CMSG_HAVE_AFS_TOKEN); - packet_put_string((char *) buffer, strlen(buffer)); + packet_put_string(buffer, strlen(buffer)); packet_send(); packet_write_wait(); @@ -1104,7 +1108,9 @@ out: int try_skey_authentication() { - int type, i, payload_len; + int type, i; + int payload_len; + unsigned int clen; char *challenge, *response; debug("Doing skey authentication."); @@ -1124,7 +1130,8 @@ try_skey_authentication() debug("No challenge for skey authentication."); return 0; } - challenge = packet_get_string(&payload_len); + challenge = packet_get_string(&clen); + packet_integrity_check(payload_len, (4 + clen), type); if (options.cipher == SSH_CIPHER_NONE) log("WARNING: Encryption is disabled! " "Reponse will be transmitted in clear text."); @@ -1306,9 +1313,9 @@ read_yes_or_no(const char *prompt, int defval) */ void -check_host_key(char *host, struct sockaddr *hostaddr, RSA *host_key) +check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) { - RSA *file_key; + Key *file_key; char *ip = NULL; char hostline[1000], *hostp; HostStatus host_status; @@ -1358,47 +1365,34 @@ check_host_key(char *host, struct sockaddr *hostaddr, RSA *host_key) * Store the host key from the known host file in here so that we can * compare it with the key for the IP address. */ - file_key = RSA_new(); - file_key->n = BN_new(); - file_key->e = BN_new(); + file_key = key_new(host_key->type); /* * Check if the host key is present in the user\'s list of known * hosts or in the systemwide list. */ - host_status = check_host_in_hostfile(options.user_hostfile, host, - host_key->e, host_key->n, - file_key->e, file_key->n); + host_status = check_host_in_hostfile(options.user_hostfile, host, host_key, file_key); if (host_status == HOST_NEW) - host_status = check_host_in_hostfile(options.system_hostfile, host, - host_key->e, host_key->n, - file_key->e, file_key->n); + host_status = check_host_in_hostfile(options.system_hostfile, host, host_key, file_key); /* * Also perform check for the ip address, skip the check if we are * localhost or the hostname was an ip address to begin with */ if (options.check_host_ip && !local && strcmp(host, ip)) { - RSA *ip_key = RSA_new(); - ip_key->n = BN_new(); - ip_key->e = BN_new(); - ip_status = check_host_in_hostfile(options.user_hostfile, ip, - host_key->e, host_key->n, - ip_key->e, ip_key->n); + Key *ip_key = key_new(host_key->type); + ip_status = check_host_in_hostfile(options.user_hostfile, ip, host_key, ip_key); if (ip_status == HOST_NEW) - ip_status = check_host_in_hostfile(options.system_hostfile, ip, - host_key->e, host_key->n, - ip_key->e, ip_key->n); + ip_status = check_host_in_hostfile(options.system_hostfile, ip, host_key, ip_key); if (host_status == HOST_CHANGED && - (ip_status != HOST_CHANGED || - (BN_cmp(ip_key->e, file_key->e) || BN_cmp(ip_key->n, file_key->n)))) + (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) host_ip_differ = 1; - RSA_free(ip_key); + key_free(ip_key); } else ip_status = host_status; - RSA_free(file_key); + key_free(file_key); switch (host_status) { case HOST_OK: @@ -1406,8 +1400,7 @@ check_host_key(char *host, struct sockaddr *hostaddr, RSA *host_key) debug("Host '%.200s' is known and matches the host key.", host); if (options.check_host_ip) { if (ip_status == HOST_NEW) { - if (!add_host_to_hostfile(options.user_hostfile, ip, - host_key->e, host_key->n)) + if (!add_host_to_hostfile(options.user_hostfile, ip, host_key)) log("Failed to add the host key for IP address '%.30s' to the list of known hosts (%.30s).", ip, options.user_hostfile); else @@ -1427,12 +1420,12 @@ check_host_key(char *host, struct sockaddr *hostaddr, RSA *host_key) } else if (options.strict_host_key_checking == 2) { /* The default */ char prompt[1024]; - char *fp = fingerprint(host_key->e, host_key->n); + char *fp = key_fingerprint(host_key); snprintf(prompt, sizeof(prompt), "The authenticity of host '%.200s' can't be established.\n" - "Key fingerprint is %d %s.\n" + "Key fingerprint is %s.\n" "Are you sure you want to continue connecting (yes/no)? ", - host, BN_num_bits(host_key->n), fp); + host, fp); if (!read_yes_or_no(prompt, -1)) fatal("Aborted by user!\n"); } @@ -1443,8 +1436,7 @@ check_host_key(char *host, struct sockaddr *hostaddr, RSA *host_key) hostp = host; /* If not in strict mode, add the key automatically to the local known_hosts file. */ - if (!add_host_to_hostfile(options.user_hostfile, hostp, - host_key->e, host_key->n)) + if (!add_host_to_hostfile(options.user_hostfile, hostp, host_key)) log("Failed to add the host to the list of known hosts (%.500s).", options.user_hostfile); else @@ -1512,6 +1504,14 @@ check_host_key(char *host, struct sockaddr *hostaddr, RSA *host_key) if (options.check_host_ip) xfree(ip); } +void +check_rsa_host_key(char *host, struct sockaddr *hostaddr, RSA *host_key) +{ + Key k; + k.type = KEY_RSA; + k.rsa = host_key; + check_host_key(host, hostaddr, &k); +} /* * SSH1 key exchange @@ -1587,7 +1587,7 @@ ssh_kex(char *host, struct sockaddr *hostaddr) 8 + 4 + sum_len + 0 + 4 + 0 + 0 + 4 + 4 + 4, SSH_SMSG_PUBLIC_KEY); - check_host_key(host, hostaddr, host_key); + check_rsa_host_key(host, hostaddr, host_key); client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN; @@ -1875,7 +1875,6 @@ ssh_userauth(int host_key_valid, RSA *own_host_key, fatal("Permission denied."); /* NOTREACHED */ } - /* * Starts a dialog with the server, and authenticates the current user on the * server. This does not need any extra privileges. The basic connection @@ -1906,6 +1905,7 @@ ssh_login(int host_key_valid, RSA *own_host_key, const char *orighost, ssh_kex(host, hostaddr); if (supported_authentications == 0) fatal("supported_authentications == 0."); + /* authenticate user */ ssh_userauth(host_key_valid, own_host_key, original_real_uid, host); } diff --git a/crypto/openssh/sshd.8 b/crypto/openssh/sshd.8 index b76b8ee..521bee6 100644 --- a/crypto/openssh/sshd.8 +++ b/crypto/openssh/sshd.8 @@ -9,7 +9,7 @@ .\" .\" Created: Sat Apr 22 21:55:14 1995 ylo .\" -.\" $Id: sshd.8,v 1.34 2000/02/24 18:22:16 markus Exp $ +.\" $Id: sshd.8,v 1.37 2000/03/24 03:04:46 brad Exp $ .\" $FreeBSD$ .\" .Dd September 25, 1999 @@ -34,39 +34,48 @@ .Xr ssh 1 . Together these programs replace rlogin and rsh programs, and provide secure encrypted communications between two untrusted hosts -over an insecure network. The programs are intended to be as easy to +over an insecure network. +The programs are intended to be as easy to install and use as possible. .Pp .Nm -is the daemon that listens for connections from clients. It is -normally started at boot from +is the daemon that listens for connections from clients. +It is normally started at boot from .Pa /etc/rc.network . It forks a new -daemon for each incoming connection. The forked daemons handle +daemon for each incoming connection. +The forked daemons handle key exchange, encryption, authentication, command execution, and data exchange. .Pp .Nm -works as follows. Each host has a host-specific RSA key -(normally 1024 bits) used to identify the host. Additionally, when +works as follows. +Each host has a host-specific RSA key +(normally 1024 bits) used to identify the host. +Additionally, when the daemon starts, it generates a server RSA key (normally 768 bits). This key is normally regenerated every hour if it has been used, and is never stored on disk. .Pp Whenever a client connects the daemon, the daemon sends its host -and server public keys to the client. The client compares the +and server public keys to the client. +The client compares the host key against its own database to verify that it has not changed. -The client then generates a 256 bit random number. It encrypts this +The client then generates a 256 bit random number. +It encrypts this random number using both the host key and the server key, and sends -the encrypted number to the server. Both sides then start to use this +the encrypted number to the server. +Both sides then start to use this random number as a session key which is used to encrypt all further -communications in the session. The rest of the session is encrypted +communications in the session. +The rest of the session is encrypted using a conventional cipher, currently Blowfish and 3DES, with 3DES -being is used by default. The client selects the encryption algorithm +being is used by default. +The client selects the encryption algorithm to use from those offered by the server. .Pp -Next, the server and the client enter an authentication dialog. The -client tries to authenticate itself using +Next, the server and the client enter an authentication dialog. +The client tries to authenticate itself using .Pa .rhosts authentication, .Pa .rhosts @@ -76,7 +85,8 @@ based authentication. .Pp Rhosts authentication is normally disabled because it is fundamentally insecure, but can be enabled in the server -configuration file if desired. System security is not improved unless +configuration file if desired. +System security is not improved unless .Xr rshd 8 , .Xr rlogind 8 , .Xr rexecd 8 , @@ -89,13 +99,15 @@ and into that machine). .Pp If the client successfully authenticates itself, a dialog for -preparing the session is entered. At this time the client may request +preparing the session is entered. +At this time the client may request things like allocating a pseudo-tty, forwarding X11 connections, forwarding TCP/IP connections, or forwarding the authentication agent connection over the secure channel. .Pp Finally, the client either requests a shell or execution of a command. -The sides then enter session mode. In this mode, either side may send +The sides then enter session mode. +In this mode, either side may send data at any time, and such data is forwarded to/from the shell or command on the server side, and the user terminal in the client side. .Pp @@ -105,7 +117,8 @@ the client, and both sides exit. .Pp .Nm can be configured using command-line options or a configuration -file. Command-line options override values specified in the +file. +Command-line options override values specified in the configuration file. .Pp .Nm @@ -118,20 +131,23 @@ The options are as follows: Specifies the number of bits in the server key (default 768). .Pp .It Fl d -Debug mode. The server sends verbose debug output to the system -log, and does not put itself in the background. The server also will -not fork and will only process one connection. This option is only -intended for debugging for the server. +Debug mode. +The server sends verbose debug output to the system +log, and does not put itself in the background. +The server also will not fork and will only process one connection. +This option is only intended for debugging for the server. .It Fl f Ar configuration_file -Specifies the name of the configuration file. The default is +Specifies the name of the configuration file. +The default is .Pa /etc/ssh/sshd_config . .Nm refuses to start if there is no configuration file. .It Fl g Ar login_grace_time Gives the grace time for clients to authenticate themselves (default -300 seconds). If the client fails to authenticate the user within -this many seconds, the server disconnects and exits. A value of zero -indicates no limit. +300 seconds). +If the client fails to authenticate the user within +this many seconds, the server disconnects and exits. +A value of zero indicates no limit. .It Fl h Ar host_key_file Specifies the file from which the host key is read (default .Pa /etc/ssh/ssh_host_key ) . @@ -146,24 +162,28 @@ is being run from inetd. .Nm is normally not run from inetd because it needs to generate the server key before it can -respond to the client, and this may take tens of seconds. Clients -would have to wait too long if the key was regenerated every time. -However, with small key sizes (e.g. 512) using +respond to the client, and this may take tens of seconds. +Clients would have to wait too long if the key was regenerated every time. +However, with small key sizes (e.g., 512) using .Nm from inetd may be feasible. .It Fl k Ar key_gen_time Specifies how often the server key is regenerated (default 3600 -seconds, or one hour). The motivation for regenerating the key fairly +seconds, or one hour). +The motivation for regenerating the key fairly often is that the key is not stored anywhere, and after about an hour, it becomes impossible to recover the key for decrypting intercepted communications even if the machine is cracked into or physically -seized. A value of zero indicates that the key will never be regenerated. +seized. +A value of zero indicates that the key will never be regenerated. .It Fl p Ar port Specifies the port on which the server listens for connections (default 22). .It Fl q -Quiet mode. Nothing is sent to the system log. Normally the beginning, +Quiet mode. +Nothing is sent to the system log. +Normally the beginning, authentication, and termination of each connection is logged. .It Fl Q Do not print an error message if RSA support is missing. @@ -189,39 +209,43 @@ reads configuration data from .Pa /etc/ssh/sshd_config (or the file specified with .Fl f -on the command line). The file -contains keyword-value pairs, one per line. Lines starting with +on the command line). +The file contains keyword-value pairs, one per line. +Lines starting with .Ql # and empty lines are interpreted as comments. .Pp The following keywords are possible. .Bl -tag -width Ds .It Cm AFSTokenPassing -Specifies whether an AFS token may be forwarded to the server. Default is +Specifies whether an AFS token may be forwarded to the server. +Default is .Dq yes . .It Cm AllowGroups This keyword can be followed by a number of group names, separated -by spaces. If specified, login is allowed only for users whose primary +by spaces. +If specified, login is allowed only for users whose primary group matches one of the patterns. .Ql \&* and .Ql ? can be used as -wildcards in the patterns. Only group names are valid, a numerical group -id isn't recognized. By default login is allowed regardless of -the primary group. +wildcards in the patterns. +Only group names are valid, a numerical group ID isn't recognized. +By default login is allowed regardless of the primary group. .Pp .It Cm AllowUsers This keyword can be followed by a number of user names, separated -by spaces. If specified, login is allowed only for users names that +by spaces. +If specified, login is allowed only for users names that match one of the patterns. .Ql \&* and .Ql ? can be used as -wildcards in the patterns. Only user names are valid, a numerical user -id isn't recognized. By default login is allowed regardless of -the user name. +wildcards in the patterns. +Only user names are valid, a numerical user ID isn't recognized. +By default login is allowed regardless of the user name. .Pp .It Cm CheckMail Specifies whether @@ -256,27 +280,27 @@ and any parameter. .It Cm DenyGroups This keyword can be followed by a number of group names, separated -by spaces. Users whose primary group matches one of the patterns +by spaces. +Users whose primary group matches one of the patterns aren't allowed to log in. .Ql \&* and .Ql ? can be used as -wildcards in the patterns. Only group names are valid, a numerical group -id isn't recognized. By default login is allowed regardless of -the primary group. +wildcards in the patterns. +Only group names are valid, a numerical group ID isn't recognized. +By default login is allowed regardless of the primary group. .Pp .It Cm DenyUsers This keyword can be followed by a number of user names, separated -by spaces. Login is disallowed for user names that match -one of the patterns. +by spaces. +Login is disallowed for user names that match one of the patterns. .Ql \&* and .Ql ? -can be used as -wildcards in the patterns. Only user names are valid, a numerical user -id isn't recognized. By default login is allowed regardless of -the user name. +can be used as wildcards in the patterns. +Only user names are valid, a numerical user ID isn't recognized. +By default login is allowed regardless of the user name. .It Cm HostKey Specifies the file containing the private host key (default .Pa /etc/ssh/ssh_host_key ) . @@ -292,7 +316,9 @@ files will not be used in authentication. .Pa /etc/hosts.equiv and .Pa /etc/ssh/shosts.equiv -are still used. The default is +.Pa /etc/shosts.equiv +are still used. +The default is .Dq yes . .It Cm IgnoreUserKnownHosts Specifies whether @@ -305,10 +331,13 @@ The default is .Dq no . .It Cm KeepAlive Specifies whether the system should send keepalive messages to the -other side. If they are sent, death of the connection or crash of one -of the machines will be properly noticed. However, this means that +other side. +If they are sent, death of the connection or crash of one +of the machines will be properly noticed. +However, this means that connections will die if the route is down temporarily, and some people -find it annoying. On the other hand, if keepalives are not send, +find it annoying. +On the other hand, if keepalives are not send, sessions may hang indefinitely on the server, leaving .Dq ghost users and consuming server resources. @@ -316,25 +345,27 @@ users and consuming server resources. The default is .Dq yes (to send keepalives), and the server will notice -if the network goes down or the client host reboots. This avoids -infinitely hanging sessions. +if the network goes down or the client host reboots. +This avoids infinitely hanging sessions. .Pp To disable keepalives, the value should be set to .Dq no in both the server and the client configuration files. .It Cm KerberosAuthentication -Specifies whether Kerberos authentication is allowed. This can -be in the form of a Kerberos ticket, or if +Specifies whether Kerberos authentication is allowed. +This can be in the form of a Kerberos ticket, or if .Cm PasswordAuthentication is yes, the password provided by the user will be validated through -the Kerberos KDC. Default is +the Kerberos KDC. +Default is .Dq yes . .It Cm KerberosOrLocalPasswd If set then if password authentication through Kerberos fails then the password will be validated via any additional local mechanism such as .Pa /etc/passwd -or SecurID. Default is +or SecurID. +Default is .Dq yes . .It Cm KerberosTgtPassing Specifies whether a Kerberos TGT may be forwarded to the server. @@ -343,15 +374,18 @@ Default is as this only works when the Kerberos KDC is actually an AFS kaserver. .It Cm KerberosTicketCleanup Specifies whether to automatically destroy the user's ticket cache -file on logout. Default is +file on logout. +Default is .Dq yes . .It Cm KeyRegenerationInterval The server key is automatically regenerated after this many seconds -(if it has been used). The purpose of regeneration is to prevent +(if it has been used). +The purpose of regeneration is to prevent decrypting captured sessions by later breaking into the machine and -stealing the keys. The key is never stored anywhere. If the value is -0, the key is never regenerated. The default is 3600 -(seconds). +stealing the keys. +The key is never stored anywhere. +If the value is 0, the key is never regenerated. +The default is 3600 (seconds). .It Cm ListenAddress Specifies what local address .Nm @@ -363,7 +397,8 @@ Additionally, the options must precede this option. .It Cm LoginGraceTime The server disconnects after this time if the user has not -successfully logged in. If the value is 0, there is no time limit. +successfully logged in. +If the value is 0, there is no time limit. The default is 600 (seconds). .It Cm LogLevel Gives the verbosity level that is used when logging messages from @@ -379,8 +414,8 @@ The default is .Dq yes . .It Cm PermitEmptyPasswords When password authentication is allowed, it specifies whether the -server allows login to accounts with empty password strings. The default -is +server allows login to accounts with empty password strings. +The default is .Dq no . .It Cm PermitRootLogin Specifies whether the root can log in using @@ -405,17 +440,19 @@ normally not allowed). .It Cm Port Specifies the port number that .Nm -listens on. The default is 22. +listens on. +The default is 22. Multiple options of this type are permitted. .It Cm PrintMotd Specifies whether .Nm should print .Pa /etc/motd -when a user logs in interactively. (On some systems it is also -printed by the shell, +when a user logs in interactively. +(On some systems it is also printed by the shell, .Pa /etc/profile , -or equivalent.) The default is +or equivalent.) +The default is .Dq yes . .It Cm RandomSeed Obsolete - accepted and ignored with a warning. @@ -423,8 +460,8 @@ Random number generation uses other techniques. .It Cm RhostsAuthentication Specifies whether authentication using rhosts or .Pa /etc/hosts.equiv -files is sufficient. Normally, this method should not be permitted -because it is insecure. +files is sufficient. +Normally, this method should not be permitted because it is insecure. .Cm RhostsRSAAuthentication should be used instead, because it performs RSA-based host authentication in addition @@ -437,18 +474,21 @@ The default is Specifies whether rhosts or .Pa /etc/hosts.equiv authentication together -with successful RSA host authentication is allowed. The default is +with successful RSA host authentication is allowed. +The default is .Dq no . .It Cm RSAAuthentication -Specifies whether pure RSA authentication is allowed. The default is +Specifies whether pure RSA authentication is allowed. +The default is .Dq yes . .It Cm ServerKeyBits -Defines the number of bits in the server key. The minimum value is -512, and the default is 768. +Defines the number of bits in the server key. +The minimum value is 512, and the default is 768. .It Cm SkeyAuthentication Specifies whether .Xr skey 1 -authentication is allowed. The default is +authentication is allowed. +The default is .Dq yes . Note that OPIE authentication is enabled only if .Cm PasswordAuthentication @@ -457,30 +497,35 @@ is allowed, too. Specifies whether .Nm should check file modes and ownership of the -user's files and home directory before accepting login. This -is normally desirable because novices sometimes accidentally leave their -directory or files world-writable. The default is +user's files and home directory before accepting login. +This is normally desirable because novices sometimes accidentally leave their +directory or files world-writable. +The default is .Dq yes . .It Cm SyslogFacility Gives the facility code that is used when logging messages from .Nm sshd . The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2, -LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7. The default is AUTH. +LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7. +The default is AUTH. .It Cm UseLogin Specifies whether .Xr login 1 -is used. The default is +is used. +The default is .Dq no . .It Cm X11DisplayOffset Specifies the first display number available for .Nm sshd Ns 's -X11 forwarding. This prevents +X11 forwarding. +This prevents .Nm from interfering with real X11 servers. The default is 10. .It Cm X11Forwarding -Specifies whether X11 forwarding is permitted. The default is -.Dq yes . +Specifies whether X11 forwarding is permitted. +The default is +.Dq no . Note that disabling X11 forwarding does not improve security in any way, as users can always install their own forwarders. .El @@ -535,12 +580,15 @@ Runs user's shell or command. The .Pa $HOME/.ssh/authorized_keys file lists the RSA keys that are -permitted for RSA authentication. Each line of the file contains one +permitted for RSA authentication. +Each line of the file contains one key (empty lines and lines starting with a .Ql # are ignored as -comments). Each line consists of the following fields, separated by -spaces: options, bits, exponent, modulus, comment. The options field +comments). +Each line consists of the following fields, separated by +spaces: options, bits, exponent, modulus, comment. +The options field is optional; its presence is determined by whether the line starts with a number or not (the option field never starts with a number). The bits, exponent, modulus and comment fields give the RSA key; the @@ -548,47 +596,58 @@ comment field is not used for anything (but may be convenient for the user to identify the key). .Pp Note that lines in this file are usually several hundred bytes long -(because of the size of the RSA key modulus). You don't want to type -them in; instead, copy the +(because of the size of the RSA key modulus). +You don't want to type them in; instead, copy the .Pa identity.pub file and edit it. .Pp The options (if present) consists of comma-separated option -specifications. No spaces are permitted, except within double quotes. +specifications. +No spaces are permitted, except within double quotes. The following option specifications are supported: .Bl -tag -width Ds .It Cm from="pattern-list" Specifies that in addition to RSA authentication, the canonical name of the remote host must be present in the comma-separated list of -patterns ('*' and '?' serve as wildcards). The list may also contain -patterns negated by prefixing them with '!'; if the canonical host -name matches a negated pattern, the key is not accepted. The purpose +patterns +.Pf ( Ql * +and +.Ql ? +serve as wildcards). +The list may also contain +patterns negated by prefixing them with +.Ql ! ; +if the canonical host name matches a negated pattern, the key is not accepted. +The purpose of this option is to optionally increase security: RSA authentication by itself does not trust the network or name servers or anything (but the key); however, if somebody somehow steals the key, the key -permits an intruder to log in from anywhere in the world. This -additional option makes using a stolen key more difficult (name +permits an intruder to log in from anywhere in the world. +This additional option makes using a stolen key more difficult (name servers and/or routers would have to be compromised in addition to just the key). .It Cm command="command" Specifies that the command is executed whenever this key is used for -authentication. The command supplied by the user (if any) is ignored. +authentication. +The command supplied by the user (if any) is ignored. The command is run on a pty if the connection requests a pty; -otherwise it is run without a tty. A quote may be included in the -command by quoting it with a backslash. This option might be useful -to restrict certain RSA keys to perform just a specific operation. An -example might be a key that permits remote backups but nothing -else. Notice that the client may specify TCP/IP and/or X11 +otherwise it is run without a tty. +A quote may be included in the command by quoting it with a backslash. +This option might be useful +to restrict certain RSA keys to perform just a specific operation. +An example might be a key that permits remote backups but nothing else. +Notice that the client may specify TCP/IP and/or X11 forwardings unless they are explicitly prohibited. .It Cm environment="NAME=value" Specifies that the string is to be added to the environment when -logging in using this key. Environment variables set this way -override other default environment values. Multiple options of this -type are permitted. +logging in using this key. +Environment variables set this way +override other default environment values. +Multiple options of this type are permitted. .It Cm no-port-forwarding Forbids TCP/IP forwarding when this key is used for authentication. -Any port forward requests by the client will return an error. This -might be used, e.g., in connection with the +Any port forward requests by the client will return an error. +This might be used, e.g., in connection with the .Cm command option. .It Cm no-X11-forwarding @@ -611,19 +670,21 @@ The .Pa /etc/ssh/ssh_known_hosts and .Pa $HOME/.ssh/known_hosts -files contain host public keys for all known hosts. The global file should +files contain host public keys for all known hosts. +The global file should be prepared by the administrator (optional), and the per-user file is maintained automatically: whenever the user connects an unknown host -its key is added to the per-user file. +its key is added to the per-user file. .Pp Each line in these files contains the following fields: hostnames, -bits, exponent, modulus, comment. The fields are separated by spaces. +bits, exponent, modulus, comment. +The fields are separated by spaces. .Pp Hostnames is a comma-separated list of patterns ('*' and '?' act as wildcards); each pattern in turn is matched against the canonical host name (when authenticating a client) or against the user-supplied -name (when authenticating a server). A pattern may also be preceded -by +name (when authenticating a server). +A pattern may also be preceded by .Ql ! to indicate negation: if the host name matches a negated pattern, it is not accepted (by that line) even if it matched another @@ -639,10 +700,13 @@ Lines starting with and empty lines are ignored as comments. .Pp When performing host authentication, authentication is accepted if any -matching line has the proper key. It is thus permissible (but not +matching line has the proper key. +It is thus permissible (but not recommended) to have several lines or different host keys for the same -names. This will inevitably happen when short forms of host names -from different domains are put in the file. It is possible +names. +This will inevitably happen when short forms of host names +from different domains are put in the file. +It is possible that the files contain conflicting information; authentication is accepted if valid information can be found from either file. .Pp @@ -673,7 +737,9 @@ does not start if this file is group/world-accessible. .It Pa /etc/ssh/ssh_host_key.pub Contains the public part of the host key. This file should be world-readable but writable only by -root. Its contents should match the private part. This file is not +root. +Its contents should match the private part. +This file is not really used for anything; it is only provided for the convenience of the user so its contents can be copied to known hosts files. These two files are created using @@ -683,21 +749,22 @@ Contains the process ID of the .Nm listening for connections (if there are several daemons running concurrently for different ports, this contains the pid of the one -started last). The contents of this file are not sensitive; it can be -world-readable. +started last). +The contents of this file are not sensitive; it can be world-readable. .It Pa $HOME/.ssh/authorized_keys Lists the RSA keys that can be used to log into the user's account. This file must be readable by root (which may on some machines imply it being world-readable if the user's home directory resides on an NFS -volume). It is recommended that it not be accessible by others. The -format of this file is described above. +volume). +It is recommended that it not be accessible by others. +The format of this file is described above. .It Pa "/etc/ssh/ssh_known_hosts" and "$HOME/.ssh/known_hosts" These files are consulted when using rhosts with RSA host -authentication to check the public key of the host. The key must be -listed in one of these files to be accepted. +authentication to check the public key of the host. +The key must be listed in one of these files to be accepted. The client uses the same files -to verify that the remote host is the one we intended to -connect. These files should be writable only by root/the owner. +to verify that the remote host is the one we intended to connect. +These files should be writable only by root/the owner. .Pa /etc/ssh/ssh_known_hosts should be world-readable, and .Pa $HOME/.ssh/known_hosts @@ -705,9 +772,11 @@ can but need not be world-readable. .It Pa /etc/nologin If this file exists, .Nm -refuses to let anyone except root log in. The contents of the file +refuses to let anyone except root log in. +The contents of the file are displayed to anyone trying to log in, and non-root connections are -refused. The file should be world-readable. +refused. +The file should be world-readable. .It Pa /etc/hosts.allow If compiled with .Sy LIBWRAP @@ -715,13 +784,16 @@ support, tcp-wrappers access controls may be defined here as described in .Xr hosts_access 5 . .It Pa $HOME/.rhosts This file contains host-username pairs, separated by a space, one per -line. The given user on the corresponding host is permitted to log in -without password. The same file is used by rlogind and rshd. +line. +The given user on the corresponding host is permitted to log in +without password. +The same file is used by rlogind and rshd. The file must be writable only by the user; it is recommended that it not be accessible by others. .Pp -If is also possible to use netgroups in the file. Either host or user +If is also possible to use netgroups in the file. +Either host or user name may be of the form +@groupname to specify all hosts or all users in the group. .It Pa $HOME/.shosts @@ -733,21 +805,26 @@ not used by rlogin and rshd, so using this permits access using SSH only. .It Pa /etc/hosts.equiv This file is used during .Pa .rhosts -authentication. In the -simplest form, this file contains host names, one per line. Users on +authentication. +In the simplest form, this file contains host names, one per line. +Users on those hosts are permitted to log in without a password, provided they -have the same user name on both machines. The host name may also be +have the same user name on both machines. +The host name may also be followed by a user name; such users are permitted to log in as .Em any -user on this machine (except root). Additionally, the syntax +user on this machine (except root). +Additionally, the syntax .Dq +@group -can be used to specify netgroups. Negated entries start with +can be used to specify netgroups. +Negated entries start with .Ql \&- . .Pp If the client host/user is successfully matched in this file, login is automatically permitted provided the client and server user names are the -same. Additionally, successful RSA host authentication is normally -required. This file must be writable only by root; it is recommended +same. +Additionally, successful RSA host authentication is normally required. +This file must be writable only by root; it is recommended that it be world-readable. .Pp .Sy "Warning: It is almost never a good idea to use user names in" @@ -755,8 +832,9 @@ that it be world-readable. Beware that it really means that the named user(s) can log in as .Em anybody , which includes bin, daemon, adm, and other accounts that own critical -binaries and directories. Using a user name practically grants the -user root access. The only valid use for user names that I can think +binaries and directories. +Using a user name practically grants the user root access. +The only valid use for user names that I can think of is in negative entries. .Pp Note that this warning also applies to rsh/rlogin. @@ -766,20 +844,22 @@ This is processed exactly as However, this file may be useful in environments that want to run both rsh/rlogin and ssh. .It Pa $HOME/.ssh/environment -This file is read into the environment at login (if it exists). It -can only contain empty lines, comment lines (that start with +This file is read into the environment at login (if it exists). +It can only contain empty lines, comment lines (that start with .Ql # ) , -and assignment lines of the form name=value. The file should be writable +and assignment lines of the form name=value. +The file should be writable only by the user; it need not be readable by anyone else. .It Pa $HOME/.ssh/rc If this file exists, it is run with .Pa /bin/sh after reading the -environment files but before starting the user's shell or command. If -X11 spoofing is in use, this will receive the "proto cookie" pair in +environment files but before starting the user's shell or command. +If X11 spoofing is in use, this will receive the "proto cookie" pair in standard input (and .Ev DISPLAY -in environment). This must call +in environment). +This must call .Xr xauth 1 in that case. .Pp @@ -808,12 +888,13 @@ readable by anyone else. Like .Pa $HOME/.ssh/rc . This can be used to specify -machine-specific login-time initializations globally. This file -should be writable only by root, and should be world-readable. +machine-specific login-time initializations globally. +This file should be writable only by root, and should be world-readable. .Sh AUTHOR OpenSSH is a derivative of the original (free) ssh 1.2.12 release by Tatu Ylonen, -but with bugs removed and newer features re-added. Rapidly after the +but with bugs removed and newer features re-added. +Rapidly after the 1.2.12 release, newer versions of the original ssh bore successively more restrictive licenses, and thus demand for a free version was born. This version of OpenSSH diff --git a/crypto/openssh/sshd.c b/crypto/openssh/sshd.c index 627d09c..b2b7e90 100644 --- a/crypto/openssh/sshd.c +++ b/crypto/openssh/sshd.c @@ -13,7 +13,7 @@ */ #include "includes.h" -RCSID("$OpenBSD: sshd.c,v 1.88 2000/02/15 16:52:57 markus Exp $"); +RCSID("$OpenBSD: sshd.c,v 1.94 2000/03/23 22:15:34 markus Exp $"); #include "xmalloc.h" #include "rsa.h" @@ -564,9 +564,6 @@ main(int ac, char **av) unmounted if desired. */ chdir("/"); - /* Close connection cleanly after attack. */ - cipher_attack_detected = packet_disconnect; - /* Start listening for a socket, unless started from inetd. */ if (inetd_flag) { int s1, s2; @@ -1288,7 +1285,8 @@ void do_authentication() { struct passwd *pw, pwcopy; - int plen, ulen; + int plen; + unsigned int ulen; char *user; #ifdef LOGIN_CAP login_cap_t *lc; @@ -1423,11 +1421,13 @@ do_authloop(struct passwd * pw) { int attempt = 0; unsigned int bits; - BIGNUM *client_host_key_e, *client_host_key_n; + RSA *client_host_key; BIGNUM *n; char *client_user, *password; char user[1024]; - int plen, dlen, nlen, ulen, elen; + unsigned int dlen; + int plen, nlen, elen; + unsigned int ulen; int type = 0; void (*authlog) (const char *fmt,...) = verbose; #ifdef HAVE_LIBPAM @@ -1584,21 +1584,24 @@ do_authloop(struct passwd * pw) client_user = packet_get_string(&ulen); /* Get the client host key. */ - client_host_key_e = BN_new(); - client_host_key_n = BN_new(); + client_host_key = RSA_new(); + if (client_host_key == NULL) + fatal("RSA_new failed"); + client_host_key->e = BN_new(); + client_host_key->n = BN_new(); + if (client_host_key->e == NULL || client_host_key->n == NULL) + fatal("BN_new failed"); bits = packet_get_int(); - packet_get_bignum(client_host_key_e, &elen); - packet_get_bignum(client_host_key_n, &nlen); + packet_get_bignum(client_host_key->e, &elen); + packet_get_bignum(client_host_key->n, &nlen); - if (bits != BN_num_bits(client_host_key_n)) + if (bits != BN_num_bits(client_host_key->n)) error("Warning: keysize mismatch for client_host_key: " - "actual %d, announced %d", BN_num_bits(client_host_key_n), bits); + "actual %d, announced %d", BN_num_bits(client_host_key->n), bits); packet_integrity_check(plen, (4 + ulen) + 4 + elen + nlen, type); - authenticated = auth_rhosts_rsa(pw, client_user, - client_host_key_e, client_host_key_n); - BN_clear_free(client_host_key_e); - BN_clear_free(client_host_key_n); + authenticated = auth_rhosts_rsa(pw, client_user, client_host_key); + RSA_free(client_host_key); snprintf(user, sizeof user, " ruser %s", client_user); xfree(client_user); @@ -1684,6 +1687,21 @@ do_authloop(struct passwd * pw) break; } + /* + * Check if the user is logging in as root and root logins + * are disallowed. + * Note that root login is allowed for forced commands. + */ + if (authenticated && pw->pw_uid == 0 && !options.permit_root_login) { + if (forced_command) { + log("Root login accepted for forced command."); + } else { + authenticated = 0; + log("ROOT LOGIN REFUSED FROM %.200s", + get_canonical_hostname()); + } + } + /* Raise logging level */ if (authenticated || attempt == AUTH_FAIL_LOG || @@ -1739,7 +1757,7 @@ do_fake_authloop(char *user) int plen; int type = packet_read(&plen); #ifdef SKEY - int dlen; + unsigned int dlen; char *password, *skeyinfo; /* Try to send a fake s/key challenge. */ if (options.skey_authentication == 1 && @@ -1823,6 +1841,8 @@ do_authenticated(struct passwd * pw) int row, col, xpixel, ypixel, screen; char ttyname[64]; char *command, *term = NULL, *display = NULL, *proto = NULL, *data = NULL; + int plen; + unsigned int dlen; int n_bytes; /* @@ -1846,7 +1866,6 @@ do_authenticated(struct passwd * pw) * or a command. */ while (1) { - int plen, dlen; /* Get a packet from the client. */ type = packet_read(&plen); @@ -1925,7 +1944,7 @@ do_authenticated(struct passwd * pw) if (display) packet_disconnect("Protocol error: X11 display already set."); { - int proto_len, data_len; + unsigned int proto_len, data_len; proto = packet_get_string(&proto_len); data = packet_get_string(&data_len); packet_integrity_check(plen, 4 + proto_len + 4 + data_len + 4, type); @@ -1950,8 +1969,9 @@ do_authenticated(struct passwd * pw) xauthfile = NULL; goto fail; } - restore_uid(); strlcat(xauthfile, "/cookies", MAXPATHLEN); + open(xauthfile, O_RDWR|O_CREAT|O_EXCL, 0600); + restore_uid(); fatal_add_cleanup(xauthfile_cleanup_proc, NULL); break; #else /* XAUTH_PATH */ @@ -2006,7 +2026,7 @@ do_authenticated(struct passwd * pw) goto do_forced_command; /* Get command from the packet. */ { - int dlen; + unsigned int dlen; command = packet_get_string(&dlen); debug("Executing command '%.500s'", command); packet_integrity_check(plen, 4 + dlen, type); @@ -2900,7 +2920,7 @@ do_child(const char *command, struct passwd * pw, const char *term, f = popen(XAUTH_PATH " -q -", "w"); if (f) { fprintf(f, "add %s %s %s\n", display, auth_proto, auth_data); - fclose(f); + pclose(f); } else fprintf(stderr, "Could not run %s -q -\n", XAUTH_PATH); } |