diff options
Diffstat (limited to 'crypto/openssh/sshconnect1.c')
| -rw-r--r-- | crypto/openssh/sshconnect1.c | 1307 |
1 files changed, 1307 insertions, 0 deletions
diff --git a/crypto/openssh/sshconnect1.c b/crypto/openssh/sshconnect1.c new file mode 100644 index 0000000..368b412 --- /dev/null +++ b/crypto/openssh/sshconnect1.c @@ -0,0 +1,1307 @@ +/* + * Author: Tatu Ylonen <ylo@cs.hut.fi> + * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland + * All rights reserved + * Code to connect to a remote host, and to perform the client side of the + * login (authentication) dialog. + * + * As far as I am concerned, the code I have written for this software + * can be used freely for any purpose. Any derived versions of this + * software must be clearly marked as such, and if the derived work is + * incompatible with the protocol description in the RFC file, it must be + * called by a name other than "ssh" or "Secure Shell". + */ + +#include "includes.h" +RCSID("$OpenBSD: sshconnect1.c,v 1.52 2002/08/08 13:50:23 aaron Exp $"); +RCSID("$FreeBSD$"); + +#include <openssl/bn.h> +#include <openssl/md5.h> + +#ifdef KRB4 +#include <krb.h> +#endif +#ifdef KRB5 +#include <krb5.h> +#ifndef HEIMDAL +#define krb5_get_err_text(context,code) error_message(code) +#endif /* !HEIMDAL */ +#endif +#ifdef AFS +#include <kafs.h> +#include "radix.h" +#endif + +#include "ssh.h" +#include "ssh1.h" +#include "xmalloc.h" +#include "rsa.h" +#include "buffer.h" +#include "packet.h" +#include "mpaux.h" +#include "uidswap.h" +#include "log.h" +#include "readconf.h" +#include "key.h" +#include "authfd.h" +#include "sshconnect.h" +#include "authfile.h" +#include "readpass.h" +#include "cipher.h" +#include "canohost.h" +#include "auth.h" + +/* Session id for the current session. */ +u_char session_id[16]; +u_int supported_authentications = 0; + +extern Options options; +extern char *__progname; + +/* + * Checks if the user has an authentication agent, and if so, tries to + * authenticate using the agent. + */ +static int +try_agent_authentication(void) +{ + int type; + char *comment; + AuthenticationConnection *auth; + u_char response[16]; + u_int i; + Key *key; + BIGNUM *challenge; + + /* Get connection to the agent. */ + auth = ssh_get_authentication_connection(); + if (!auth) + return 0; + + if ((challenge = BN_new()) == NULL) + fatal("try_agent_authentication: BN_new failed"); + /* Loop through identities served by the agent. */ + for (key = ssh_get_first_identity(auth, &comment, 1); + key != NULL; + key = ssh_get_next_identity(auth, &comment, 1)) { + + /* Try this identity. */ + debug("Trying RSA authentication via agent with '%.100s'", comment); + xfree(comment); + + /* Tell the server that we are willing to authenticate using this key. */ + packet_start(SSH_CMSG_AUTH_RSA); + packet_put_bignum(key->rsa->n); + packet_send(); + packet_write_wait(); + + /* Wait for server's response. */ + type = packet_read(); + + /* The server sends failure if it doesn\'t like our key or + does not support RSA authentication. */ + if (type == SSH_SMSG_FAILURE) { + debug("Server refused our key."); + key_free(key); + continue; + } + /* Otherwise it should have sent a challenge. */ + if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) + packet_disconnect("Protocol error during RSA authentication: %d", + type); + + packet_get_bignum(challenge); + packet_check_eom(); + + debug("Received RSA challenge from server."); + + /* Ask the agent to decrypt the challenge. */ + if (!ssh_decrypt_challenge(auth, key, challenge, session_id, 1, response)) { + /* + * The agent failed to authenticate this identifier + * although it advertised it supports this. Just + * return a wrong value. + */ + log("Authentication agent failed to decrypt challenge."); + memset(response, 0, sizeof(response)); + } + key_free(key); + debug("Sending response to RSA challenge."); + + /* Send the decrypted challenge back to the server. */ + packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); + for (i = 0; i < 16; i++) + packet_put_char(response[i]); + packet_send(); + packet_write_wait(); + + /* Wait for response from the server. */ + type = packet_read(); + + /* The server returns success if it accepted the authentication. */ + if (type == SSH_SMSG_SUCCESS) { + ssh_close_authentication_connection(auth); + BN_clear_free(challenge); + debug("RSA authentication accepted by server."); + return 1; + } + /* Otherwise it should return failure. */ + if (type != SSH_SMSG_FAILURE) + packet_disconnect("Protocol error waiting RSA auth response: %d", + type); + } + ssh_close_authentication_connection(auth); + BN_clear_free(challenge); + debug("RSA authentication using agent refused."); + return 0; +} + +/* + * Computes the proper response to a RSA challenge, and sends the response to + * the server. + */ +static void +respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv) +{ + u_char buf[32], response[16]; + MD5_CTX md; + int i, len; + + /* Decrypt the challenge using the private key. */ + /* XXX think about Bleichenbacher, too */ + if (rsa_private_decrypt(challenge, challenge, prv) <= 0) + packet_disconnect( + "respond_to_rsa_challenge: rsa_private_decrypt failed"); + + /* Compute the response. */ + /* The response is MD5 of decrypted challenge plus session id. */ + len = BN_num_bytes(challenge); + if (len <= 0 || len > sizeof(buf)) + packet_disconnect( + "respond_to_rsa_challenge: bad challenge length %d", len); + + memset(buf, 0, sizeof(buf)); + BN_bn2bin(challenge, buf + sizeof(buf) - len); + MD5_Init(&md); + MD5_Update(&md, buf, 32); + MD5_Update(&md, session_id, 16); + MD5_Final(response, &md); + + debug("Sending response to host key RSA challenge."); + + /* Send the response back to the server. */ + packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); + for (i = 0; i < 16; i++) + packet_put_char(response[i]); + packet_send(); + packet_write_wait(); + + memset(buf, 0, sizeof(buf)); + memset(response, 0, sizeof(response)); + memset(&md, 0, sizeof(md)); +} + +/* + * Checks if the user has authentication file, and if so, tries to authenticate + * the user using it. + */ +static int +try_rsa_authentication(int idx) +{ + BIGNUM *challenge; + Key *public, *private; + char buf[300], *passphrase, *comment, *authfile; + int i, type, quit; + + public = options.identity_keys[idx]; + authfile = options.identity_files[idx]; + comment = xstrdup(authfile); + + debug("Trying RSA authentication with key '%.100s'", comment); + + /* Tell the server that we are willing to authenticate using this key. */ + packet_start(SSH_CMSG_AUTH_RSA); + packet_put_bignum(public->rsa->n); + packet_send(); + packet_write_wait(); + + /* Wait for server's response. */ + type = packet_read(); + + /* + * The server responds with failure if it doesn\'t like our key or + * doesn\'t support RSA authentication. + */ + if (type == SSH_SMSG_FAILURE) { + debug("Server refused our key."); + xfree(comment); + return 0; + } + /* Otherwise, the server should respond with a challenge. */ + if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) + packet_disconnect("Protocol error during RSA authentication: %d", type); + + /* Get the challenge from the packet. */ + if ((challenge = BN_new()) == NULL) + fatal("try_rsa_authentication: BN_new failed"); + packet_get_bignum(challenge); + packet_check_eom(); + + debug("Received RSA challenge from server."); + + /* + * If the key is not stored in external hardware, we have to + * load the private key. Try first with empty passphrase; if it + * fails, ask for a passphrase. + */ + if (public->flags & KEY_FLAG_EXT) + private = public; + else + private = key_load_private_type(KEY_RSA1, authfile, "", NULL); + if (private == NULL && !options.batch_mode) { + snprintf(buf, sizeof(buf), + "Enter passphrase for RSA key '%.100s': ", comment); + for (i = 0; i < options.number_of_password_prompts; i++) { + passphrase = read_passphrase(buf, 0); + if (strcmp(passphrase, "") != 0) { + private = key_load_private_type(KEY_RSA1, + authfile, passphrase, NULL); + quit = 0; + } else { + debug2("no passphrase given, try next key"); + quit = 1; + } + memset(passphrase, 0, strlen(passphrase)); + xfree(passphrase); + if (private != NULL || quit) + break; + debug2("bad passphrase given, try again..."); + } + } + /* We no longer need the comment. */ + xfree(comment); + + if (private == NULL) { + if (!options.batch_mode) + error("Bad passphrase."); + + /* Send a dummy response packet to avoid protocol error. */ + packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); + for (i = 0; i < 16; i++) + packet_put_char(0); + packet_send(); + packet_write_wait(); + + /* Expect the server to reject it... */ + packet_read_expect(SSH_SMSG_FAILURE); + BN_clear_free(challenge); + return 0; + } + + /* Compute and send a response to the challenge. */ + respond_to_rsa_challenge(challenge, private->rsa); + + /* Destroy the private key unless it in external hardware. */ + if (!(private->flags & KEY_FLAG_EXT)) + key_free(private); + + /* We no longer need the challenge. */ + BN_clear_free(challenge); + + /* Wait for response from the server. */ + type = packet_read(); + if (type == SSH_SMSG_SUCCESS) { + debug("RSA authentication accepted by server."); + return 1; + } + if (type != SSH_SMSG_FAILURE) + packet_disconnect("Protocol error waiting RSA auth response: %d", type); + debug("RSA authentication refused."); + return 0; +} + +/* + * Tries to authenticate the user using combined rhosts or /etc/hosts.equiv + * authentication and RSA host authentication. + */ +static int +try_rhosts_rsa_authentication(const char *local_user, Key * host_key) +{ + int type; + BIGNUM *challenge; + + debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication."); + + /* Tell the server that we are willing to authenticate using this key. */ + packet_start(SSH_CMSG_AUTH_RHOSTS_RSA); + packet_put_cstring(local_user); + packet_put_int(BN_num_bits(host_key->rsa->n)); + packet_put_bignum(host_key->rsa->e); + packet_put_bignum(host_key->rsa->n); + packet_send(); + packet_write_wait(); + + /* Wait for server's response. */ + type = packet_read(); + + /* The server responds with failure if it doesn't admit our + .rhosts authentication or doesn't know our host key. */ + if (type == SSH_SMSG_FAILURE) { + debug("Server refused our rhosts authentication or host key."); + return 0; + } + /* Otherwise, the server should respond with a challenge. */ + if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) + packet_disconnect("Protocol error during RSA authentication: %d", type); + + /* Get the challenge from the packet. */ + if ((challenge = BN_new()) == NULL) + fatal("try_rhosts_rsa_authentication: BN_new failed"); + packet_get_bignum(challenge); + packet_check_eom(); + + debug("Received RSA challenge for host key from server."); + + /* Compute a response to the challenge. */ + respond_to_rsa_challenge(challenge, host_key->rsa); + + /* We no longer need the challenge. */ + BN_clear_free(challenge); + + /* Wait for response from the server. */ + type = packet_read(); + if (type == SSH_SMSG_SUCCESS) { + debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server."); + return 1; + } + if (type != SSH_SMSG_FAILURE) + packet_disconnect("Protocol error waiting RSA auth response: %d", type); + debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused."); + return 0; +} + +#ifdef KRB4 +static int +try_krb4_authentication(void) +{ + KTEXT_ST auth; /* Kerberos data */ + char *reply; + char inst[INST_SZ]; + char *realm; + CREDENTIALS cred; + int r, type; + socklen_t slen; + Key_schedule schedule; + u_long checksum, cksum; + MSG_DAT msg_data; + struct sockaddr_in local, foreign; + struct stat st; + + /* Don't do anything if we don't have any tickets. */ + if (stat(tkt_string(), &st) < 0) + return 0; + + strlcpy(inst, (char *)krb_get_phost(get_canonical_hostname(1)), + INST_SZ); + + realm = (char *)krb_realmofhost(get_canonical_hostname(1)); + if (!realm) { + debug("Kerberos v4: no realm for %s", get_canonical_hostname(1)); + return 0; + } + /* This can really be anything. */ + checksum = (u_long)getpid(); + + r = krb_mk_req(&auth, KRB4_SERVICE_NAME, inst, realm, checksum); + if (r != KSUCCESS) { + debug("Kerberos v4 krb_mk_req failed: %s", krb_err_txt[r]); + return 0; + } + /* Get session key to decrypt the server's reply with. */ + r = krb_get_cred(KRB4_SERVICE_NAME, inst, realm, &cred); + if (r != KSUCCESS) { + debug("get_cred failed: %s", krb_err_txt[r]); + return 0; + } + des_key_sched((des_cblock *) cred.session, schedule); + + /* Send authentication info to server. */ + packet_start(SSH_CMSG_AUTH_KERBEROS); + packet_put_string((char *) auth.dat, auth.length); + packet_send(); + packet_write_wait(); + + /* Zero the buffer. */ + (void) memset(auth.dat, 0, MAX_KTXT_LEN); + + slen = sizeof(local); + memset(&local, 0, sizeof(local)); + if (getsockname(packet_get_connection_in(), + (struct sockaddr *)&local, &slen) < 0) + debug("getsockname failed: %s", strerror(errno)); + + slen = sizeof(foreign); + memset(&foreign, 0, sizeof(foreign)); + if (getpeername(packet_get_connection_in(), + (struct sockaddr *)&foreign, &slen) < 0) { + debug("getpeername failed: %s", strerror(errno)); + fatal_cleanup(); + } + /* Get server reply. */ + type = packet_read(); + switch (type) { + case SSH_SMSG_FAILURE: + /* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */ + debug("Kerberos v4 authentication failed."); + return 0; + break; + + case SSH_SMSG_AUTH_KERBEROS_RESPONSE: + /* SSH_SMSG_AUTH_KERBEROS_SUCCESS */ + debug("Kerberos v4 authentication accepted."); + + /* Get server's response. */ + reply = packet_get_string((u_int *) &auth.length); + if (auth.length >= MAX_KTXT_LEN) + fatal("Kerberos v4: Malformed response from server"); + memcpy(auth.dat, reply, auth.length); + xfree(reply); + + packet_check_eom(); + + /* + * If his response isn't properly encrypted with the session + * key, and the decrypted checksum fails to match, he's + * bogus. Bail out. + */ + r = krb_rd_priv(auth.dat, auth.length, schedule, &cred.session, + &foreign, &local, &msg_data); + if (r != KSUCCESS) { + debug("Kerberos v4 krb_rd_priv failed: %s", + krb_err_txt[r]); + packet_disconnect("Kerberos v4 challenge failed!"); + } + /* Fetch the (incremented) checksum that we supplied in the request. */ + memcpy((char *)&cksum, (char *)msg_data.app_data, + sizeof(cksum)); + cksum = ntohl(cksum); + + /* If it matches, we're golden. */ + if (cksum == checksum + 1) { + debug("Kerberos v4 challenge successful."); + return 1; + } else + packet_disconnect("Kerberos v4 challenge failed!"); + break; + + default: + packet_disconnect("Protocol error on Kerberos v4 response: %d", type); + } + return 0; +} + +#endif /* KRB4 */ + +#ifdef KRB5 +static int +try_krb5_authentication(krb5_context *context, krb5_auth_context *auth_context) +{ + krb5_error_code problem; + const char *tkfile; + struct stat buf; + krb5_ccache ccache = NULL; + const char *remotehost; + krb5_data ap; + int type; + krb5_ap_rep_enc_part *reply = NULL; + int ret; + + memset(&ap, 0, sizeof(ap)); + + problem = krb5_init_context(context); + if (problem) { + debug("Kerberos v5: krb5_init_context failed"); + ret = 0; + goto out; + } + + problem = krb5_auth_con_init(*context, auth_context); + if (problem) { + debug("Kerberos v5: krb5_auth_con_init failed"); + ret = 0; + goto out; + } + +#ifndef HEIMDAL + problem = krb5_auth_con_setflags(*context, *auth_context, + KRB5_AUTH_CONTEXT_RET_TIME); + if (problem) { + debug("Keberos v5: krb5_auth_con_setflags failed"); + ret = 0; + goto out; + } +#endif + + tkfile = krb5_cc_default_name(*context); + if (strncmp(tkfile, "FILE:", 5) == 0) + tkfile += 5; + + if (stat(tkfile, &buf) == 0 && getuid() != buf.st_uid) { + debug("Kerberos v5: could not get default ccache (permission denied)."); + ret = 0; + goto out; + } + + problem = krb5_cc_default(*context, &ccache); + if (problem) { + debug("Kerberos v5: krb5_cc_default failed: %s", + krb5_get_err_text(*context, problem)); + ret = 0; + goto out; + } + + remotehost = get_canonical_hostname(1); + + problem = krb5_mk_req(*context, auth_context, AP_OPTS_MUTUAL_REQUIRED, + "host", remotehost, NULL, ccache, &ap); + if (problem) { + debug("Kerberos v5: krb5_mk_req failed: %s", + krb5_get_err_text(*context, problem)); + ret = 0; + goto out; + } + + packet_start(SSH_CMSG_AUTH_KERBEROS); + packet_put_string((char *) ap.data, ap.length); + packet_send(); + packet_write_wait(); + + xfree(ap.data); + ap.length = 0; + + type = packet_read(); + switch (type) { + case SSH_SMSG_FAILURE: + /* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */ + debug("Kerberos v5 authentication failed."); + ret = 0; + break; + + case SSH_SMSG_AUTH_KERBEROS_RESPONSE: + /* SSH_SMSG_AUTH_KERBEROS_SUCCESS */ + debug("Kerberos v5 authentication accepted."); + + /* Get server's response. */ + ap.data = packet_get_string((unsigned int *) &ap.length); + packet_check_eom(); + /* XXX je to dobre? */ + + problem = krb5_rd_rep(*context, *auth_context, &ap, &reply); + if (problem) { + ret = 0; + } + ret = 1; + break; + + default: + packet_disconnect("Protocol error on Kerberos v5 response: %d", + type); + ret = 0; + break; + + } + + out: + if (ccache != NULL) + krb5_cc_close(*context, ccache); + if (reply != NULL) + krb5_free_ap_rep_enc_part(*context, reply); + if (ap.length > 0) +#ifdef HEIMDAL + krb5_data_free(&ap); +#else + krb5_free_data_contents(*context, &ap); +#endif + + return (ret); +} + +static void +send_krb5_tgt(krb5_context context, krb5_auth_context auth_context) +{ + int fd, type; + krb5_error_code problem; + krb5_data outbuf; + krb5_ccache ccache = NULL; + krb5_creds creds; +#ifdef HEIMDAL + krb5_kdc_flags flags; +#else + int forwardable; +#endif + const char *remotehost; + + memset(&creds, 0, sizeof(creds)); + memset(&outbuf, 0, sizeof(outbuf)); + + fd = packet_get_connection_in(); + +#ifdef HEIMDAL + problem = krb5_auth_con_setaddrs_from_fd(context, auth_context, &fd); +#else + problem = krb5_auth_con_genaddrs(context, auth_context, fd, + KRB5_AUTH_CONTEXT_GENERATE_REMOTE_FULL_ADDR | + KRB5_AUTH_CONTEXT_GENERATE_LOCAL_FULL_ADDR); +#endif + if (problem) + goto out; + + problem = krb5_cc_default(context, &ccache); + if (problem) + goto out; + + problem = krb5_cc_get_principal(context, ccache, &creds.client); + if (problem) + goto out; + + remotehost = get_canonical_hostname(1); + +#ifdef HEIMDAL + problem = krb5_build_principal(context, &creds.server, + strlen(creds.client->realm), creds.client->realm, + "krbtgt", creds.client->realm, NULL); +#else + problem = krb5_build_principal(context, &creds.server, + creds.client->realm.length, creds.client->realm.data, + "host", remotehost, NULL); +#endif + if (problem) + goto out; + + creds.times.endtime = 0; + +#ifdef HEIMDAL + flags.i = 0; + flags.b.forwarded = 1; + flags.b.forwardable = krb5_config_get_bool(context, NULL, + "libdefaults", "forwardable", NULL); + problem = krb5_get_forwarded_creds(context, auth_context, + ccache, flags.i, remotehost, &creds, &outbuf); +#else + forwardable = 1; + problem = krb5_fwd_tgt_creds(context, auth_context, remotehost, + creds.client, creds.server, ccache, forwardable, &outbuf); +#endif + + if (problem) + goto out; + + packet_start(SSH_CMSG_HAVE_KERBEROS_TGT); + packet_put_string((char *)outbuf.data, outbuf.length); + packet_send(); + packet_write_wait(); + + type = packet_read(); + + if (type == SSH_SMSG_SUCCESS) { + char *pname; + + krb5_unparse_name(context, creds.client, &pname); + debug("Kerberos v5 TGT forwarded (%s).", pname); + xfree(pname); + } else + debug("Kerberos v5 TGT forwarding failed."); + + return; + + out: + if (problem) + debug("Kerberos v5 TGT forwarding failed: %s", + krb5_get_err_text(context, problem)); + if (creds.client) + krb5_free_principal(context, creds.client); + if (creds.server) + krb5_free_principal(context, creds.server); + if (ccache) + krb5_cc_close(context, ccache); + if (outbuf.data) + xfree(outbuf.data); +} +#endif /* KRB5 */ + +#ifdef AFS +static void +send_krb4_tgt(void) +{ + CREDENTIALS *creds; + struct stat st; + char buffer[4096], pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ]; + int problem, type; + + /* Don't do anything if we don't have any tickets. */ + if (stat(tkt_string(), &st) < 0) + return; + + creds = xmalloc(sizeof(*creds)); + + problem = krb_get_tf_fullname(TKT_FILE, pname, pinst, prealm); + if (problem) + goto out; + + problem = krb_get_cred("krbtgt", prealm, prealm, creds); + if (problem) + goto out; + + if (time(0) > krb_life_to_time(creds->issue_date, creds->lifetime)) { + problem = RD_AP_EXP; + goto out; + } + creds_to_radix(creds, (u_char *)buffer, sizeof(buffer)); + + packet_start(SSH_CMSG_HAVE_KERBEROS_TGT); + packet_put_cstring(buffer); + packet_send(); + packet_write_wait(); + + type = packet_read(); + + if (type == SSH_SMSG_SUCCESS) + debug("Kerberos v4 TGT forwarded (%s%s%s@%s).", + creds->pname, creds->pinst[0] ? "." : "", + creds->pinst, creds->realm); + else + debug("Kerberos v4 TGT rejected."); + + xfree(creds); + return; + + out: + debug("Kerberos v4 TGT passing failed: %s", krb_err_txt[problem]); + xfree(creds); +} + +static void +send_afs_tokens(void) +{ + CREDENTIALS creds; + struct ViceIoctl parms; + struct ClearToken ct; + int i, type, len; + char buf[2048], *p, *server_cell; + char buffer[8192]; + + /* Move over ktc_GetToken, here's something leaner. */ + for (i = 0; i < 100; i++) { /* just in case */ + parms.in = (char *) &i; + parms.in_size = sizeof(i); + parms.out = buf; + parms.out_size = sizeof(buf); + if (k_pioctl(0, VIOCGETTOK, &parms, 0) != 0) + break; + p = buf; + + /* Get secret token. */ + memcpy(&creds.ticket_st.length, p, sizeof(u_int)); + if (creds.ticket_st.length > MAX_KTXT_LEN) + break; + p += sizeof(u_int); + memcpy(creds.ticket_st.dat, p, creds.ticket_st.length); + p += creds.ticket_st.length; + + /* Get clear token. */ + memcpy(&len, p, sizeof(len)); + if (len != sizeof(struct ClearToken)) + break; + p += sizeof(len); + memcpy(&ct, p, len); + p += len; + p += sizeof(len); /* primary flag */ + server_cell = p; + + /* Flesh out our credentials. */ + strlcpy(creds.service, "afs", sizeof(creds.service)); + creds.instance[0] = '\0'; + strlcpy(creds.realm, server_cell, REALM_SZ); + memcpy(creds.session, ct.HandShakeKey, DES_KEY_SZ); + creds.issue_date = ct.BeginTimestamp; + creds.lifetime = krb_time_to_life(creds.issue_date, + ct.EndTimestamp); + creds.kvno = ct.AuthHandle; + snprintf(creds.pname, sizeof(creds.pname), "AFS ID %d", ct.ViceId); + creds.pinst[0] = '\0'; + + /* Encode token, ship it off. */ + if (creds_to_radix(&creds, (u_char *)buffer, + sizeof(buffer)) <= 0) + break; + packet_start(SSH_CMSG_HAVE_AFS_TOKEN); + packet_put_cstring(buffer); + packet_send(); + packet_write_wait(); + + /* Roger, Roger. Clearance, Clarence. What's your vector, + Victor? */ + type = packet_read(); + + if (type == SSH_SMSG_FAILURE) + debug("AFS token for cell %s rejected.", server_cell); + else if (type != SSH_SMSG_SUCCESS) + packet_disconnect("Protocol error on AFS token response: %d", type); + } +} + +#endif /* AFS */ + +/* + * Tries to authenticate with any string-based challenge/response system. + * Note that the client code is not tied to s/key or TIS. + */ +static int +try_challenge_response_authentication(void) +{ + int type, i; + u_int clen; + char prompt[1024]; + char *challenge, *response; + + debug("Doing challenge response authentication."); + + for (i = 0; i < options.number_of_password_prompts; i++) { + /* request a challenge */ + packet_start(SSH_CMSG_AUTH_TIS); + packet_send(); + packet_write_wait(); + + type = packet_read(); + if (type != SSH_SMSG_FAILURE && + type != SSH_SMSG_AUTH_TIS_CHALLENGE) { + packet_disconnect("Protocol error: got %d in response " + "to SSH_CMSG_AUTH_TIS", type); + } + if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) { + debug("No challenge."); + return 0; + } + challenge = packet_get_string(&clen); + packet_check_eom(); + snprintf(prompt, sizeof prompt, "%s%s", challenge, + strchr(challenge, '\n') ? "" : "\nResponse: "); + xfree(challenge); + if (i != 0) + error("Permission denied, please try again."); + if (options.cipher == SSH_CIPHER_NONE) + log("WARNING: Encryption is disabled! " + "Response will be transmitted in clear text."); + response = read_passphrase(prompt, 0); + if (strcmp(response, "") == 0) { + xfree(response); + break; + } + packet_start(SSH_CMSG_AUTH_TIS_RESPONSE); + ssh_put_password(response); + memset(response, 0, strlen(response)); + xfree(response); + packet_send(); + packet_write_wait(); + type = packet_read(); + if (type == SSH_SMSG_SUCCESS) + return 1; + if (type != SSH_SMSG_FAILURE) + packet_disconnect("Protocol error: got %d in response " + "to SSH_CMSG_AUTH_TIS_RESPONSE", type); + } + /* failure */ + return 0; +} + +/* + * Tries to authenticate with plain passwd authentication. + */ +static int +try_password_authentication(char *prompt) +{ + int type, i; + char *password; + + debug("Doing password authentication."); + if (options.cipher == SSH_CIPHER_NONE) + log("WARNING: Encryption is disabled! Password will be transmitted in clear text."); + for (i = 0; i < options.number_of_password_prompts; i++) { + if (i != 0) + error("Permission denied, please try again."); + password = read_passphrase(prompt, 0); + packet_start(SSH_CMSG_AUTH_PASSWORD); + ssh_put_password(password); + memset(password, 0, strlen(password)); + xfree(password); + packet_send(); + packet_write_wait(); + + type = packet_read(); + if (type == SSH_SMSG_SUCCESS) + return 1; + if (type != SSH_SMSG_FAILURE) + packet_disconnect("Protocol error: got %d in response to passwd auth", type); + } + /* failure */ + return 0; +} + +/* + * SSH1 key exchange + */ +void +ssh_kex(char *host, struct sockaddr *hostaddr) +{ + int i; + BIGNUM *key; + Key *host_key, *server_key; + int bits, rbits; + int ssh_cipher_default = SSH_CIPHER_3DES; + u_char session_key[SSH_SESSION_KEY_LENGTH]; + u_char cookie[8]; + u_int supported_ciphers; + u_int server_flags, client_flags; + u_int32_t rand = 0; + + debug("Waiting for server public key."); + + /* Wait for a public key packet from the server. */ + packet_read_expect(SSH_SMSG_PUBLIC_KEY); + + /* Get cookie from the packet. */ + for (i = 0; i < 8; i++) + cookie[i] = packet_get_char(); + + /* Get the public key. */ + server_key = key_new(KEY_RSA1); + bits = packet_get_int(); + packet_get_bignum(server_key->rsa->e); + packet_get_bignum(server_key->rsa->n); + + rbits = BN_num_bits(server_key->rsa->n); + if (bits != rbits) { + log("Warning: Server lies about size of server public key: " + "actual size is %d bits vs. announced %d.", rbits, bits); + log("Warning: This may be due to an old implementation of ssh."); + } + /* Get the host key. */ + host_key = key_new(KEY_RSA1); + bits = packet_get_int(); + packet_get_bignum(host_key->rsa->e); + packet_get_bignum(host_key->rsa->n); + + rbits = BN_num_bits(host_key->rsa->n); + if (bits != rbits) { + log("Warning: Server lies about size of server host key: " + "actual size is %d bits vs. announced %d.", rbits, bits); + log("Warning: This may be due to an old implementation of ssh."); + } + + /* Get protocol flags. */ + server_flags = packet_get_int(); + packet_set_protocol_flags(server_flags); + + supported_ciphers = packet_get_int(); + supported_authentications = packet_get_int(); + packet_check_eom(); + + debug("Received server public key (%d bits) and host key (%d bits).", + BN_num_bits(server_key->rsa->n), BN_num_bits(host_key->rsa->n)); + + if (verify_host_key(host, hostaddr, host_key) == -1) + fatal("Host key verification failed."); + + client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN; + + compute_session_id(session_id, cookie, host_key->rsa->n, server_key->rsa->n); + + /* Generate a session key. */ + arc4random_stir(); + + /* + * Generate an encryption key for the session. The key is a 256 bit + * random number, interpreted as a 32-byte key, with the least + * significant 8 bits being the first byte of the key. + */ + for (i = 0; i < 32; i++) { + if (i % 4 == 0) + rand = arc4random(); + session_key[i] = rand & 0xff; + rand >>= 8; + } + + /* + * According to the protocol spec, the first byte of the session key + * is the highest byte of the integer. The session key is xored with + * the first 16 bytes of the session id. + */ + if ((key = BN_new()) == NULL) + fatal("respond_to_rsa_challenge: BN_new failed"); + BN_set_word(key, 0); + for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { + BN_lshift(key, key, 8); + if (i < 16) + BN_add_word(key, session_key[i] ^ session_id[i]); + else + BN_add_word(key, session_key[i]); + } + + /* + * Encrypt the integer using the public key and host key of the + * server (key with smaller modulus first). + */ + if (BN_cmp(server_key->rsa->n, host_key->rsa->n) < 0) { + /* Public key has smaller modulus. */ + if (BN_num_bits(host_key->rsa->n) < + BN_num_bits(server_key->rsa->n) + SSH_KEY_BITS_RESERVED) { + fatal("respond_to_rsa_challenge: host_key %d < server_key %d + " + "SSH_KEY_BITS_RESERVED %d", + BN_num_bits(host_key->rsa->n), + BN_num_bits(server_key->rsa->n), + SSH_KEY_BITS_RESERVED); + } + rsa_public_encrypt(key, key, server_key->rsa); + rsa_public_encrypt(key, key, host_key->rsa); + } else { + /* Host key has smaller modulus (or they are equal). */ + if (BN_num_bits(server_key->rsa->n) < + BN_num_bits(host_key->rsa->n) + SSH_KEY_BITS_RESERVED) { + fatal("respond_to_rsa_challenge: server_key %d < host_key %d + " + "SSH_KEY_BITS_RESERVED %d", + BN_num_bits(server_key->rsa->n), + BN_num_bits(host_key->rsa->n), + SSH_KEY_BITS_RESERVED); + } + rsa_public_encrypt(key, key, host_key->rsa); + rsa_public_encrypt(key, key, server_key->rsa); + } + + /* Destroy the public keys since we no longer need them. */ + key_free(server_key); + key_free(host_key); + + if (options.cipher == SSH_CIPHER_NOT_SET) { + if (cipher_mask_ssh1(1) & supported_ciphers & (1 << ssh_cipher_default)) + options.cipher = ssh_cipher_default; + } else if (options.cipher == SSH_CIPHER_ILLEGAL || + !(cipher_mask_ssh1(1) & (1 << options.cipher))) { + log("No valid SSH1 cipher, using %.100s instead.", + cipher_name(ssh_cipher_default)); + options.cipher = ssh_cipher_default; + } + /* Check that the selected cipher is supported. */ + if (!(supported_ciphers & (1 << options.cipher))) + fatal("Selected cipher type %.100s not supported by server.", + cipher_name(options.cipher)); + + debug("Encryption type: %.100s", cipher_name(options.cipher)); + + /* Send the encrypted session key to the server. */ + packet_start(SSH_CMSG_SESSION_KEY); + packet_put_char(options.cipher); + + /* Send the cookie back to the server. */ + for (i = 0; i < 8; i++) + packet_put_char(cookie[i]); + + /* Send and destroy the encrypted encryption key integer. */ + packet_put_bignum(key); + BN_clear_free(key); + + /* Send protocol flags. */ + packet_put_int(client_flags); + + /* Send the packet now. */ + packet_send(); + packet_write_wait(); + + debug("Sent encrypted session key."); + + /* Set the encryption key. */ + packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher); + + /* We will no longer need the session key here. Destroy any extra copies. */ + memset(session_key, 0, sizeof(session_key)); + + /* + * Expect a success message from the server. Note that this message + * will be received in encrypted form. + */ + packet_read_expect(SSH_SMSG_SUCCESS); + + debug("Received encrypted confirmation."); +} + +/* + * Authenticate user + */ +void +ssh_userauth1(const char *local_user, const char *server_user, char *host, + Sensitive *sensitive) +{ +#ifdef KRB5 + krb5_context context = NULL; + krb5_auth_context auth_context = NULL; +#endif + int i, type; + + if (supported_authentications == 0) + fatal("ssh_userauth1: server supports no auth methods"); + + /* Send the name of the user to log in as on the server. */ + packet_start(SSH_CMSG_USER); + packet_put_cstring(server_user); + packet_send(); + packet_write_wait(); + + /* + * The server should respond with success if no authentication is + * needed (the user has no password). Otherwise the server responds + * with failure. + */ + type = packet_read(); + + /* check whether the connection was accepted without authentication. */ + if (type == SSH_SMSG_SUCCESS) + goto success; + if (type != SSH_SMSG_FAILURE) + packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER", type); + +#ifdef KRB5 + if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) && + options.kerberos_authentication) { + debug("Trying Kerberos v5 authentication."); + + if (try_krb5_authentication(&context, &auth_context)) { + type = packet_read(); + if (type == SSH_SMSG_SUCCESS) + goto success; + if (type != SSH_SMSG_FAILURE) + packet_disconnect("Protocol error: got %d in response to Kerberos v5 auth", type); + } + } +#endif /* KRB5 */ + +#ifdef KRB4 + if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) && + options.kerberos_authentication) { + debug("Trying Kerberos v4 authentication."); + + if (try_krb4_authentication()) { + type = packet_read(); + if (type == SSH_SMSG_SUCCESS) + goto success; + if (type != SSH_SMSG_FAILURE) + packet_disconnect("Protocol error: got %d in response to Kerberos v4 auth", type); + } + } +#endif /* KRB4 */ + + /* + * Use rhosts authentication if running in privileged socket and we + * do not wish to remain anonymous. + */ + if ((supported_authentications & (1 << SSH_AUTH_RHOSTS)) && + options.rhosts_authentication) { + debug("Trying rhosts authentication."); + packet_start(SSH_CMSG_AUTH_RHOSTS); + packet_put_cstring(local_user); + packet_send(); + packet_write_wait(); + + /* The server should respond with success or failure. */ + type = packet_read(); + if (type == SSH_SMSG_SUCCESS) + goto success; + if (type != SSH_SMSG_FAILURE) + packet_disconnect("Protocol error: got %d in response to rhosts auth", + type); + } + /* + * Try .rhosts or /etc/hosts.equiv authentication with RSA host + * authentication. + */ + if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) && + options.rhosts_rsa_authentication) { + for (i = 0; i < sensitive->nkeys; i++) { + if (sensitive->keys[i] != NULL && + sensitive->keys[i]->type == KEY_RSA1 && + try_rhosts_rsa_authentication(local_user, + sensitive->keys[i])) + goto success; + } + } + /* Try RSA authentication if the server supports it. */ + if ((supported_authentications & (1 << SSH_AUTH_RSA)) && + options.rsa_authentication) { + /* + * Try RSA authentication using the authentication agent. The + * agent is tried first because no passphrase is needed for + * it, whereas identity files may require passphrases. + */ + if (try_agent_authentication()) + goto success; + + /* Try RSA authentication for each identity. */ + for (i = 0; i < options.num_identity_files; i++) + if (options.identity_keys[i] != NULL && + options.identity_keys[i]->type == KEY_RSA1 && + try_rsa_authentication(i)) + goto success; + } + /* Try challenge response authentication if the server supports it. */ + if ((supported_authentications & (1 << SSH_AUTH_TIS)) && + options.challenge_response_authentication && !options.batch_mode) { + if (try_challenge_response_authentication()) + goto success; + } + /* Try password authentication if the server supports it. */ + if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) && + options.password_authentication && !options.batch_mode) { + char prompt[80]; + + snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password: ", + server_user, host); + if (try_password_authentication(prompt)) + goto success; + } + /* All authentication methods have failed. Exit with an error message. */ + fatal("Permission denied."); + /* NOTREACHED */ + + success: +#ifdef KRB5 + /* Try Kerberos v5 TGT passing. */ + if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) && + options.kerberos_tgt_passing && context && auth_context) { + if (options.cipher == SSH_CIPHER_NONE) + log("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!"); + send_krb5_tgt(context, auth_context); + } + if (auth_context) + krb5_auth_con_free(context, auth_context); + if (context) + krb5_free_context(context); +#endif + +#ifdef AFS + /* Try Kerberos v4 TGT passing if the server supports it. */ + if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) && + options.kerberos_tgt_passing) { + if (options.cipher == SSH_CIPHER_NONE) + log("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!"); + send_krb4_tgt(); + } + /* Try AFS token passing if the server supports it. */ + if ((supported_authentications & (1 << SSH_PASS_AFS_TOKEN)) && + options.afs_token_passing && k_hasafs()) { + if (options.cipher == SSH_CIPHER_NONE) + log("WARNING: Encryption is disabled! Token will be transmitted in the clear!"); + send_afs_tokens(); + } +#endif /* AFS */ + + return; /* need statement after label */ +} |
