diff options
Diffstat (limited to 'crypto/openssh/auth1.c')
-rw-r--r-- | crypto/openssh/auth1.c | 468 |
1 files changed, 468 insertions, 0 deletions
diff --git a/crypto/openssh/auth1.c b/crypto/openssh/auth1.c new file mode 100644 index 0000000..38114d8 --- /dev/null +++ b/crypto/openssh/auth1.c @@ -0,0 +1,468 @@ +/* + * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland + * All rights reserved + */ + +#include "includes.h" +RCSID("$OpenBSD: auth1.c,v 1.2 2000/04/29 18:11:52 markus Exp $"); + +#include "xmalloc.h" +#include "rsa.h" +#include "ssh.h" +#include "packet.h" +#include "buffer.h" +#include "cipher.h" +#include "mpaux.h" +#include "servconf.h" +#include "compat.h" +#include "auth.h" +#include "session.h" + +/* import */ +extern ServerOptions options; +extern char *forced_command; + +/* + * convert ssh auth msg type into description + */ +char * +get_authname(int type) +{ + static char buf[1024]; + switch (type) { + case SSH_CMSG_AUTH_PASSWORD: + return "password"; + case SSH_CMSG_AUTH_RSA: + return "rsa"; + case SSH_CMSG_AUTH_RHOSTS_RSA: + return "rhosts-rsa"; + case SSH_CMSG_AUTH_RHOSTS: + return "rhosts"; +#ifdef KRB4 + case SSH_CMSG_AUTH_KERBEROS: + return "kerberos"; +#endif +#ifdef SKEY + case SSH_CMSG_AUTH_TIS_RESPONSE: + return "s/key"; +#endif + } + snprintf(buf, sizeof buf, "bad-auth-msg-%d", type); + return buf; +} + +/* + * The user does not exist or access is denied, + * but fake indication that authentication is needed. + */ +void +do_fake_authloop1(char *user) +{ + int attempt = 0; + + log("Faking authloop for illegal user %.200s from %.200s port %d", + user, + get_remote_ipaddr(), + get_remote_port()); + + /* Indicate that authentication is needed. */ + packet_start(SSH_SMSG_FAILURE); + packet_send(); + packet_write_wait(); + + /* + * Keep reading packets, and always respond with a failure. This is + * to avoid disclosing whether such a user really exists. + */ + for (attempt = 1;; attempt++) { + /* Read a packet. This will not return if the client disconnects. */ + int plen; + int type = packet_read(&plen); +#ifdef SKEY + unsigned int dlen; + char *password, *skeyinfo; + password = NULL; + /* Try to send a fake s/key challenge. */ + if (options.skey_authentication == 1 && + (skeyinfo = skey_fake_keyinfo(user)) != NULL) { + if (type == SSH_CMSG_AUTH_TIS) { + packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE); + packet_put_string(skeyinfo, strlen(skeyinfo)); + packet_send(); + packet_write_wait(); + continue; + } else if (type == SSH_CMSG_AUTH_PASSWORD && + options.password_authentication && + (password = packet_get_string(&dlen)) != NULL && + dlen == 5 && + strncasecmp(password, "s/key", 5) == 0 ) { + packet_send_debug(skeyinfo); + } + } + if (password != NULL) + xfree(password); +#endif + if (attempt > AUTH_FAIL_MAX) + packet_disconnect(AUTH_FAIL_MSG, user); + + /* + * Send failure. This should be indistinguishable from a + * failed authentication. + */ + packet_start(SSH_SMSG_FAILURE); + packet_send(); + packet_write_wait(); + } + /* NOTREACHED */ + abort(); +} + +/* + * read packets and try to authenticate local user *pw. + * return if authentication is successfull + */ +void +do_authloop(struct passwd * pw) +{ + int attempt = 0; + unsigned int bits; + RSA *client_host_key; + BIGNUM *n; + char *client_user, *password; + char user[1024]; + unsigned int dlen; + int plen, nlen, elen; + unsigned int ulen; + int type = 0; + void (*authlog) (const char *fmt,...) = verbose; + + /* Indicate that authentication is needed. */ + packet_start(SSH_SMSG_FAILURE); + packet_send(); + packet_write_wait(); + + for (attempt = 1;; attempt++) { + int authenticated = 0; + strlcpy(user, "", sizeof user); + + /* Get a packet from the client. */ + type = packet_read(&plen); + + /* Process the packet. */ + switch (type) { +#ifdef AFS + case SSH_CMSG_HAVE_KERBEROS_TGT: + if (!options.kerberos_tgt_passing) { + /* packet_get_all(); */ + verbose("Kerberos tgt passing disabled."); + break; + } else { + /* Accept Kerberos tgt. */ + char *tgt = packet_get_string(&dlen); + packet_integrity_check(plen, 4 + dlen, type); + if (!auth_kerberos_tgt(pw, tgt)) + verbose("Kerberos tgt REFUSED for %s", pw->pw_name); + xfree(tgt); + } + continue; + + case SSH_CMSG_HAVE_AFS_TOKEN: + if (!options.afs_token_passing || !k_hasafs()) { + /* packet_get_all(); */ + verbose("AFS token passing disabled."); + break; + } else { + /* Accept AFS token. */ + char *token_string = packet_get_string(&dlen); + packet_integrity_check(plen, 4 + dlen, type); + if (!auth_afs_token(pw, token_string)) + verbose("AFS token REFUSED for %s", pw->pw_name); + xfree(token_string); + } + continue; +#endif /* AFS */ +#ifdef KRB4 + case SSH_CMSG_AUTH_KERBEROS: + if (!options.kerberos_authentication) { + /* packet_get_all(); */ + verbose("Kerberos authentication disabled."); + break; + } else { + /* Try Kerberos v4 authentication. */ + KTEXT_ST auth; + char *tkt_user = NULL; + char *kdata = packet_get_string((unsigned int *) &auth.length); + packet_integrity_check(plen, 4 + auth.length, type); + + if (auth.length < MAX_KTXT_LEN) + memcpy(auth.dat, kdata, auth.length); + xfree(kdata); + + authenticated = auth_krb4(pw->pw_name, &auth, &tkt_user); + + if (authenticated) { + snprintf(user, sizeof user, " tktuser %s", tkt_user); + xfree(tkt_user); + } + } + break; +#endif /* KRB4 */ + + case SSH_CMSG_AUTH_RHOSTS: + if (!options.rhosts_authentication) { + verbose("Rhosts authentication disabled."); + break; + } + /* + * Get client user name. Note that we just have to + * trust the client; this is one reason why rhosts + * authentication is insecure. (Another is + * IP-spoofing on a local network.) + */ + client_user = packet_get_string(&ulen); + packet_integrity_check(plen, 4 + ulen, type); + + /* Try to authenticate using /etc/hosts.equiv and + .rhosts. */ + authenticated = auth_rhosts(pw, client_user); + + snprintf(user, sizeof user, " ruser %s", client_user); + xfree(client_user); + break; + + case SSH_CMSG_AUTH_RHOSTS_RSA: + if (!options.rhosts_rsa_authentication) { + verbose("Rhosts with RSA authentication disabled."); + break; + } + /* + * Get client user name. Note that we just have to + * trust the client; root on the client machine can + * claim to be any user. + */ + client_user = packet_get_string(&ulen); + + /* Get the client host key. */ + 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); + + if (bits != BN_num_bits(client_host_key->n)) + log("Warning: keysize mismatch for client_host_key: " + "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); + RSA_free(client_host_key); + + snprintf(user, sizeof user, " ruser %s", client_user); + xfree(client_user); + break; + + case SSH_CMSG_AUTH_RSA: + if (!options.rsa_authentication) { + verbose("RSA authentication disabled."); + break; + } + /* RSA authentication requested. */ + n = BN_new(); + packet_get_bignum(n, &nlen); + packet_integrity_check(plen, nlen, type); + authenticated = auth_rsa(pw, n); + BN_clear_free(n); + break; + + case SSH_CMSG_AUTH_PASSWORD: + if (!options.password_authentication) { + verbose("Password authentication disabled."); + break; + } + /* + * Read user password. It is in plain text, but was + * transmitted over the encrypted channel so it is + * not visible to an outside observer. + */ + password = packet_get_string(&dlen); + packet_integrity_check(plen, 4 + dlen, type); + + /* Try authentication with the password. */ + authenticated = auth_password(pw, password); + + memset(password, 0, strlen(password)); + xfree(password); + break; + +#ifdef SKEY + case SSH_CMSG_AUTH_TIS: + debug("rcvd SSH_CMSG_AUTH_TIS"); + if (options.skey_authentication == 1) { + char *skeyinfo = skey_keyinfo(pw->pw_name); + if (skeyinfo == NULL) { + debug("generating fake skeyinfo for %.100s.", pw->pw_name); + skeyinfo = skey_fake_keyinfo(pw->pw_name); + } + if (skeyinfo != NULL) { + /* we send our s/key- in tis-challenge messages */ + debug("sending challenge '%s'", skeyinfo); + packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE); + packet_put_string(skeyinfo, strlen(skeyinfo)); + packet_send(); + packet_write_wait(); + continue; + } + } + break; + case SSH_CMSG_AUTH_TIS_RESPONSE: + debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE"); + if (options.skey_authentication == 1) { + char *response = packet_get_string(&dlen); + debug("skey response == '%s'", response); + packet_integrity_check(plen, 4 + dlen, type); + authenticated = (skey_haskey(pw->pw_name) == 0 && + skey_passcheck(pw->pw_name, response) != -1); + xfree(response); + } + break; +#else + case SSH_CMSG_AUTH_TIS: + /* TIS Authentication is unsupported */ + log("TIS authentication unsupported."); + break; +#endif + + default: + /* + * Any unknown messages will be ignored (and failure + * returned) during authentication. + */ + log("Unknown message during authentication: type %d", type); + 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 || + type == SSH_CMSG_AUTH_PASSWORD) + authlog = log; + + authlog("%s %s for %.200s from %.200s port %d%s", + authenticated ? "Accepted" : "Failed", + get_authname(type), + pw->pw_uid == 0 ? "ROOT" : pw->pw_name, + get_remote_ipaddr(), + get_remote_port(), + user); + + if (authenticated) + return; + + if (attempt > AUTH_FAIL_MAX) + packet_disconnect(AUTH_FAIL_MSG, pw->pw_name); + + /* Send a message indicating that the authentication attempt failed. */ + packet_start(SSH_SMSG_FAILURE); + packet_send(); + packet_write_wait(); + } +} + +/* + * Performs authentication of an incoming connection. Session key has already + * been exchanged and encryption is enabled. + */ +void +do_authentication() +{ + struct passwd *pw, pwcopy; + int plen; + unsigned int ulen; + char *user; + + /* Get the name of the user that we wish to log in as. */ + packet_read_expect(&plen, SSH_CMSG_USER); + + /* Get the user name. */ + user = packet_get_string(&ulen); + packet_integrity_check(plen, (4 + ulen), SSH_CMSG_USER); + + setproctitle("%s", user); + +#ifdef AFS + /* If machine has AFS, set process authentication group. */ + if (k_hasafs()) { + k_setpag(); + k_unlog(); + } +#endif /* AFS */ + + /* Verify that the user is a valid user. */ + pw = getpwnam(user); + if (!pw || !allowed_user(pw)) + do_fake_authloop1(user); + xfree(user); + + /* Take a copy of the returned structure. */ + memset(&pwcopy, 0, sizeof(pwcopy)); + pwcopy.pw_name = xstrdup(pw->pw_name); + pwcopy.pw_passwd = xstrdup(pw->pw_passwd); + pwcopy.pw_uid = pw->pw_uid; + pwcopy.pw_gid = pw->pw_gid; + pwcopy.pw_dir = xstrdup(pw->pw_dir); + pwcopy.pw_shell = xstrdup(pw->pw_shell); + pw = &pwcopy; + + /* + * If we are not running as root, the user must have the same uid as + * the server. + */ + if (getuid() != 0 && pw->pw_uid != getuid()) + packet_disconnect("Cannot change user when server not running as root."); + + debug("Attempting authentication for %.100s.", pw->pw_name); + + /* If the user has no password, accept authentication immediately. */ + if (options.password_authentication && +#ifdef KRB4 + (!options.kerberos_authentication || options.kerberos_or_local_passwd) && +#endif /* KRB4 */ + auth_password(pw, "")) { + /* Authentication with empty password succeeded. */ + log("Login for user %s from %.100s, accepted without authentication.", + pw->pw_name, get_remote_ipaddr()); + } else { + /* Loop until the user has been authenticated or the + connection is closed, do_authloop() returns only if + authentication is successfull */ + do_authloop(pw); + } + + /* The user has been authenticated and accepted. */ + packet_start(SSH_SMSG_SUCCESS); + packet_send(); + packet_write_wait(); + + /* Perform session preparation. */ + do_authenticated(pw); +} |