/* $OpenBSD: sshconnect.c,v 1.212 2008/10/14 18:11:33 stevesk Exp $ */ /* * Author: Tatu Ylonen * Copyright (c) 1995 Tatu Ylonen , 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "xmalloc.h" #include "ssh.h" #include "rsa.h" #include "buffer.h" #include "packet.h" #include "uidswap.h" #include "compat.h" #include "key.h" #include "sshconnect.h" #include "hostfile.h" #include "log.h" #include "readconf.h" #include "atomicio.h" #include "misc.h" #include "dns.h" #include "version.h" char *client_version_string = NULL; char *server_version_string = NULL; static int matching_host_key_dns = 0; /* import */ extern Options options; extern char *__progname; extern uid_t original_real_uid; extern uid_t original_effective_uid; extern pid_t proxy_command_pid; static int show_other_keys(const char *, Key *); static void warn_changed_key(Key *); /* * Connect to the given ssh server using a proxy command. */ static int ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) { char *command_string, *tmp; int pin[2], pout[2]; pid_t pid; char *shell, strport[NI_MAXSERV]; if ((shell = getenv("SHELL")) == NULL) shell = _PATH_BSHELL; /* Convert the port number into a string. */ snprintf(strport, sizeof strport, "%hu", port); /* * Build the final command string in the buffer by making the * appropriate substitutions to the given proxy command. * * Use "exec" to avoid "sh -c" processes on some platforms * (e.g. Solaris) */ xasprintf(&tmp, "exec %s", proxy_command); command_string = percent_expand(tmp, "h", host, "p", strport, (char *)NULL); xfree(tmp); /* Create pipes for communicating with the proxy. */ if (pipe(pin) < 0 || pipe(pout) < 0) fatal("Could not create pipes to communicate with the proxy: %.100s", strerror(errno)); debug("Executing proxy command: %.500s", command_string); /* Fork and execute the proxy command. */ if ((pid = fork()) == 0) { char *argv[10]; /* Child. Permanently give up superuser privileges. */ permanently_drop_suid(original_real_uid); /* Redirect stdin and stdout. */ close(pin[1]); if (pin[0] != 0) { if (dup2(pin[0], 0) < 0) perror("dup2 stdin"); close(pin[0]); } close(pout[0]); if (dup2(pout[1], 1) < 0) perror("dup2 stdout"); /* Cannot be 1 because pin allocated two descriptors. */ close(pout[1]); /* Stderr is left as it is so that error messages get printed on the user's terminal. */ argv[0] = shell; argv[1] = "-c"; argv[2] = command_string; argv[3] = NULL; /* Execute the proxy command. Note that we gave up any extra privileges above. */ execv(argv[0], argv); perror(argv[0]); exit(1); } /* Parent. */ if (pid < 0) fatal("fork failed: %.100s", strerror(errno)); else proxy_command_pid = pid; /* save pid to clean up later */ /* Close child side of the descriptors. */ close(pin[0]); close(pout[1]); /* Free the command name. */ xfree(command_string); /* Set the connection file descriptors. */ packet_set_connection(pout[0], pin[1]); packet_set_timeout(options.server_alive_interval, options.server_alive_count_max); /* Indicate OK return */ return 0; } /* * Creates a (possibly privileged) socket for use as the ssh connection. */ static int ssh_create_socket(int privileged, struct addrinfo *ai) { int sock, gaierr; struct addrinfo hints, *res; /* * If we are running as root and want to connect to a privileged * port, bind our own socket to a privileged port. */ if (privileged) { int p = IPPORT_RESERVED - 1; PRIV_START; sock = rresvport_af(&p, ai->ai_family); PRIV_END; if (sock < 0) error("rresvport: af=%d %.100s", ai->ai_family, strerror(errno)); else debug("Allocated local port %d.", p); return sock; } sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); if (sock < 0) error("socket: %.100s", strerror(errno)); /* Bind the socket to an alternative local IP address */ if (options.bind_address == NULL) return sock; memset(&hints, 0, sizeof(hints)); hints.ai_family = ai->ai_family; hints.ai_socktype = ai->ai_socktype; hints.ai_protocol = ai->ai_protocol; hints.ai_flags = AI_PASSIVE; gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res); if (gaierr) { error("getaddrinfo: %s: %s", options.bind_address, ssh_gai_strerror(gaierr)); close(sock); return -1; } if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { error("bind: %s: %s", options.bind_address, strerror(errno)); close(sock); freeaddrinfo(res); return -1; } freeaddrinfo(res); return sock; } static int timeout_connect(int sockfd, const struct sockaddr *serv_addr, socklen_t addrlen, int *timeoutp) { fd_set *fdset; struct timeval tv, t_start; socklen_t optlen; int optval, rc, result = -1; gettimeofday(&t_start, NULL); if (*timeoutp <= 0) { result = connect(sockfd, serv_addr, addrlen); goto done; } set_nonblock(sockfd); rc = connect(sockfd, serv_addr, addrlen); if (rc == 0) { unset_nonblock(sockfd); result = 0; goto done; } if (errno != EINPROGRESS) { result = -1; goto done; } fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), sizeof(fd_mask)); FD_SET(sockfd, fdset); ms_to_timeval(&tv, *timeoutp); for (;;) { rc = select(sockfd + 1, NULL, fdset, NULL, &tv); if (rc != -1 || errno != EINTR) break; } switch (rc) { case 0: /* Timed out */ errno = ETIMEDOUT; break; case -1: /* Select error */ debug("select: %s", strerror(errno)); break; case 1: /* Completed or failed */ optval = 0; optlen = sizeof(optval); if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, &optlen) == -1) { debug("getsockopt: %s", strerror(errno)); break; } if (optval != 0) { errno = optval; break; } result = 0; unset_nonblock(sockfd); break; default: /* Should not occur */ fatal("Bogus return (%d) from select()", rc); } xfree(fdset); done: if (result == 0 && *timeoutp > 0) { ms_subtract_diff(&t_start, timeoutp); if (*timeoutp <= 0) { errno = ETIMEDOUT; result = -1; } } return (result); } /* * Opens a TCP/IP connection to the remote server on the given host. * The address of the remote host will be returned in hostaddr. * If port is 0, the default port will be used. If needpriv is true, * a privileged port will be allocated to make the connection. * This requires super-user privileges if needpriv is true. * Connection_attempts specifies the maximum number of tries (one per * second). If proxy_command is non-NULL, it specifies the command (with %h * and %p substituted for host and port, respectively) to use to contact * the daemon. */ int ssh_connect(const char *host, struct sockaddr_storage * hostaddr, u_short port, int family, int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv, const char *proxy_command) { int gaierr; int on = 1; int sock = -1, attempt; char ntop[NI_MAXHOST], strport[NI_MAXSERV]; struct addrinfo hints, *ai, *aitop; debug2("ssh_connect: needpriv %d", needpriv); /* If a proxy command is given, connect using it. */ if (proxy_command != NULL) return ssh_proxy_connect(host, port, proxy_command); /* No proxy command. */ memset(&hints, 0, sizeof(hints)); hints.ai_family = family; hints.ai_socktype = SOCK_STREAM; snprintf(strport, sizeof strport, "%u", port); if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) fatal("%s: Could not resolve hostname %.100s: %s", __progname, host, ssh_gai_strerror(gaierr)); for (attempt = 0; attempt < connection_attempts; attempt++) { if (attempt > 0) { /* Sleep a moment before retrying. */ sleep(1); debug("Trying again..."); } /* * Loop through addresses for this host, and try each one in * sequence until the connection succeeds. */ for (ai = aitop; ai; ai = ai->ai_next) { if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) continue; if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop, sizeof(ntop), strport, sizeof(strport), NI_NUMERICHOST|NI_NUMERICSERV) != 0) { error("ssh_connect: getnameinfo failed"); continue; } debug("Connecting to %.200s [%.100s] port %s.", host, ntop, strport); /* Create a socket for connecting. */ sock = ssh_create_socket(needpriv, ai); if (sock < 0) /* Any error is already output */ continue; if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, timeout_ms) >= 0) { /* Successful connection. */ memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); break; } else { debug("connect to address %s port %s: %s", ntop, strport, strerror(errno)); close(sock); sock = -1; } } if (sock != -1) break; /* Successful connection. */ } freeaddrinfo(aitop); /* Return failure if we didn't get a successful connection. */ if (sock == -1) { error("ssh: connect to host %s port %s: %s", host, strport, strerror(errno)); return (-1); } debug("Connection established."); /* Set SO_KEEPALIVE if requested. */ if (want_keepalive && setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, sizeof(on)) < 0) error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); /* Set the connection. */ packet_set_connection(sock, sock); packet_set_timeout(options.server_alive_interval, options.server_alive_count_max); return 0; } /* * Waits for the server identification string, and sends our own * identification string. */ static void ssh_exchange_identification(int timeout_ms) { char buf[256], remote_version[256]; /* must be same size! */ int remote_major, remote_minor, mismatch; int connection_in = packet_get_connection_in(); int connection_out = packet_get_connection_out(); int minor1 = PROTOCOL_MINOR_1; u_int i, n; size_t len; int fdsetsz, remaining, rc; struct timeval t_start, t_remaining; fd_set *fdset; fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask); fdset = xcalloc(1, fdsetsz); /* Read other side's version identification. */ remaining = timeout_ms; for (n = 0;;) { for (i = 0; i < sizeof(buf) - 1; i++) { if (timeout_ms > 0) { gettimeofday(&t_start, NULL); ms_to_timeval(&t_remaining, remaining); FD_SET(connection_in, fdset); rc = select(connection_in + 1, fdset, NULL, fdset, &t_remaining); ms_subtract_diff(&t_start, &remaining); if (rc == 0 || remaining <= 0) fatal("Connection timed out during " "banner exchange"); if (rc == -1) { if (errno == EINTR) continue; fatal("ssh_exchange_identification: " "select: %s", strerror(errno)); } } len = atomicio(read, connection_in, &buf[i], 1); if (len != 1 && errno == EPIPE) fatal("ssh_exchange_identification: " "Connection closed by remote host"); else if (len != 1) fatal("ssh_exchange_identification: " "read: %.100s", strerror(errno)); if (buf[i] == '\r') { buf[i] = '\n'; buf[i + 1] = 0; continue; /**XXX wait for \n */ } if (buf[i] == '\n') { buf[i + 1] = 0; break; } if (++n > 65536) fatal("ssh_exchange_identification: " "No banner received"); } buf[sizeof(buf) - 1] = 0; if (strncmp(buf, "SSH-", 4) == 0) break; debug("ssh_exchange_identification: %s", buf); } server_version_string = xstrdup(buf); xfree(fdset); /* * Check that the versions match. In future this might accept * several versions and set appropriate flags to handle them. */ if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", &remote_major, &remote_minor, remote_version) != 3) fatal("Bad remote protocol version identification: '%.100s'", buf); debug("Remote protocol version %d.%d, remote software version %.100s", remote_major, remote_minor, remote_version); compat_datafellows(remote_version); mismatch = 0; switch (remote_major) { case 1: if (remote_minor == 99 && (options.protocol & SSH_PROTO_2) && !(options.protocol & SSH_PROTO_1_PREFERRED)) { enable_compat20(); break; } if (!(options.protocol & SSH_PROTO_1)) { mismatch = 1; break; } if (remote_minor < 3) { fatal("Remote machine has too old SSH software version."); } else if (remote_minor == 3 || remote_minor == 4) { /* We speak 1.3, too. */ enable_compat13(); minor1 = 3; if (options.forward_agent) { logit("Agent forwarding disabled for protocol 1.3"); options.forward_agent = 0; } } break; case 2: if (options.protocol & SSH_PROTO_2) { enable_compat20(); break; } /* FALLTHROUGH */ default: mismatch = 1; break; } if (mismatch) fatal("Protocol major versions differ: %d vs. %d", (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, remote_major); /* Send our own protocol version identification. */ snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s", compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, compat20 ? PROTOCOL_MINOR_2 : minor1, SSH_VERSION, compat20 ? "\r\n" : "\n"); if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf)) fatal("write: %.100s", strerror(errno)); client_version_string = xstrdup(buf); chop(client_version_string); chop(server_version_string); debug("Local version string %.100s", client_version_string); } /* defaults to 'no' */ static int confirm(const char *prompt) { const char *msg, *again = "Please type 'yes' or 'no': "; char *p; int ret = -1; if (options.batch_mode) return 0; for (msg = prompt;;msg = again) { p = read_passphrase(msg, RP_ECHO); if (p == NULL || (p[0] == '\0') || (p[0] == '\n') || strncasecmp(p, "no", 2) == 0) ret = 0; if (p && strncasecmp(p, "yes", 3) == 0) ret = 1; if (p) xfree(p); if (ret != -1) return ret; } } /* * check whether the supplied host key is valid, return -1 if the key * is not valid. the user_hostfile will not be updated if 'readonly' is true. */ #define RDRW 0 #define RDONLY 1 #define ROQUIET 2 static int check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, Key *host_key, int readonly, const char *user_hostfile, const char *system_hostfile) { Key *file_key; const char *type = key_type(host_key); char *ip = NULL, *host = NULL; char hostline[1000], *hostp, *fp, *ra; HostStatus host_status; HostStatus ip_status; int r, local = 0, host_ip_differ = 0; char ntop[NI_MAXHOST]; char msg[1024]; int len, host_line, ip_line, cancelled_forwarding = 0; const char *host_file = NULL, *ip_file = NULL; /* * Force accepting of the host key for loopback/localhost. The * problem is that if the home directory is NFS-mounted to multiple * machines, localhost will refer to a different machine in each of * them, and the user will get bogus HOST_CHANGED warnings. This * essentially disables host authentication for localhost; however, * this is probably not a real problem. */ /** hostaddr == 0! */ switch (hostaddr->sa_family) { case AF_INET: local = (ntohl(((struct sockaddr_in *)hostaddr)-> sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; break; case AF_INET6: local = IN6_IS_ADDR_LOOPBACK( &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); break; default: local = 0; break; } if (options.no_host_authentication_for_localhost == 1 && local && options.host_key_alias == NULL) { debug("Forcing accepting of host key for " "loopback/localhost."); return 0; } /* * We don't have the remote ip-address for connections * using a proxy command */ if (options.proxy_command == NULL) { if (getnameinfo(hostaddr, hostaddr->sa_len, ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) fatal("check_host_key: getnameinfo failed"); ip = put_host_port(ntop, port); } else { ip = xstrdup(""); } /* * Turn off check_host_ip if the connection is to localhost, via proxy * command or if we don't have a hostname to compare with */ if (options.check_host_ip && (local || strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) options.check_host_ip = 0; /* * Allow the user to record the key under a different name or * differentiate a non-standard port. This is useful for ssh * tunneling over forwarded connections or if you run multiple * sshd's on different ports on the same machine. */ if (options.host_key_alias != NULL) { host = xstrdup(options.host_key_alias); debug("using hostkeyalias: %s", host); } else { host = put_host_port(hostname, port); } /* * 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 = 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_file = user_hostfile; host_status = check_host_in_hostfile(host_file, host, host_key, file_key, &host_line); if (host_status == HOST_NEW) { host_file = system_hostfile; host_status = check_host_in_hostfile(host_file, host, host_key, file_key, &host_line); } /* * 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) { Key *ip_key = key_new(host_key->type); ip_file = user_hostfile; ip_status = check_host_in_hostfile(ip_file, ip, host_key, ip_key, &ip_line); if (ip_status == HOST_NEW) { ip_file = system_hostfile; ip_status = check_host_in_hostfile(ip_file, ip, host_key, ip_key, &ip_line); } if (host_status == HOST_CHANGED && (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) host_ip_differ = 1; key_free(ip_key); } else ip_status = host_status; key_free(file_key); switch (host_status) { case HOST_OK: /* The host is known and the key matches. */ debug("Host '%.200s' is known and matches the %s host key.", host, type); debug("Found key in %s:%d", host_file, host_line); if (options.check_host_ip && ip_status == HOST_NEW) { if (readonly) logit("%s host key for IP address " "'%.128s' not in list of known hosts.", type, ip); else if (!add_host_to_hostfile(user_hostfile, ip, host_key, options.hash_known_hosts)) logit("Failed to add the %s host key for IP " "address '%.128s' to the list of known " "hosts (%.30s).", type, ip, user_hostfile); else logit("Warning: Permanently added the %s host " "key for IP address '%.128s' to the list " "of known hosts.", type, ip); } else if (options.visual_host_key) { fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); ra = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_RANDOMART); logit("Host key fingerprint is %s\n%s\n", fp, ra); xfree(ra); xfree(fp); } break; case HOST_NEW: if (options.host_key_alias == NULL && port != 0 && port != SSH_DEFAULT_PORT) { debug("checking without port identifier"); if (check_host_key(hostname, hostaddr, 0, host_key, ROQUIET, user_hostfile, system_hostfile) == 0) { debug("found matching key w/out port"); break; } } if (readonly) goto fail; /* The host is new. */ if (options.strict_host_key_checking == 1) { /* * User has requested strict host key checking. We * will not add the host key automatically. The only * alternative left is to abort. */ error("No %s host key is known for %.200s and you " "have requested strict checking.", type, host); goto fail; } else if (options.strict_host_key_checking == 2) { char msg1[1024], msg2[1024]; if (show_other_keys(host, host_key)) snprintf(msg1, sizeof(msg1), "\nbut keys of different type are already" " known for this host."); else snprintf(msg1, sizeof(msg1), "."); /* The default */ fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); ra = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_RANDOMART); msg2[0] = '\0'; if (options.verify_host_key_dns) { if (matching_host_key_dns) snprintf(msg2, sizeof(msg2), "Matching host key fingerprint" " found in DNS.\n"); else snprintf(msg2, sizeof(msg2), "No matching host key fingerprint" " found in DNS.\n"); } snprintf(msg, sizeof(msg), "The authenticity of host '%.200s (%s)' can't be " "established%s\n" "%s key fingerprint is %s.%s%s\n%s" "Are you sure you want to continue connecting " "(yes/no)? ", host, ip, msg1, type, fp, options.visual_host_key ? "\n" : "", options.visual_host_key ? ra : "", msg2); xfree(ra); xfree(fp); if (!confirm(msg)) goto fail; } /* * If not in strict mode, add the key automatically to the * local known_hosts file. */ if (options.check_host_ip && ip_status == HOST_NEW) { snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); hostp = hostline; if (options.hash_known_hosts) { /* Add hash of host and IP separately */ r = add_host_to_hostfile(user_hostfile, host, host_key, options.hash_known_hosts) && add_host_to_hostfile(user_hostfile, ip, host_key, options.hash_known_hosts); } else { /* Add unhashed "host,ip" */ r = add_host_to_hostfile(user_hostfile, hostline, host_key, options.hash_known_hosts); } } else { r = add_host_to_hostfile(user_hostfile, host, host_key, options.hash_known_hosts); hostp = host; } if (!r) logit("Failed to add the host to the list of known " "hosts (%.500s).", user_hostfile); else logit("Warning: Permanently added '%.200s' (%s) to the " "list of known hosts.", hostp, type); break; case HOST_CHANGED: if (readonly == ROQUIET) goto fail; if (options.check_host_ip && host_ip_differ) { char *key_msg; if (ip_status == HOST_NEW) key_msg = "is unknown"; else if (ip_status == HOST_OK) key_msg = "is unchanged"; else key_msg = "has a different value"; error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); error("The %s host key for %s has changed,", type, host); error("and the key for the corresponding IP address %s", ip); error("%s. This could either mean that", key_msg); error("DNS SPOOFING is happening or the IP address for the host"); error("and its host key have changed at the same time."); if (ip_status != HOST_NEW) error("Offending key for IP in %s:%d", ip_file, ip_line); } /* The host key has changed. */ warn_changed_key(host_key); error("Add correct host key in %.100s to get rid of this message.", user_hostfile); error("Offending key in %s:%d", host_file, host_line); /* * If strict host key checking is in use, the user will have * to edit the key manually and we can only abort. */ if (options.strict_host_key_checking) { error("%s host key for %.200s has changed and you have " "requested strict checking.", type, host); goto fail; } /* * If strict host key checking has not been requested, allow * the connection but without MITM-able authentication or * forwarding. */ if (options.password_authentication) { error("Password authentication is disabled to avoid " "man-in-the-middle attacks."); options.password_authentication = 0; cancelled_forwarding = 1; } if (options.kbd_interactive_authentication) { error("Keyboard-interactive authentication is disabled" " to avoid man-in-the-middle attacks."); options.kbd_interactive_authentication = 0; options.challenge_response_authentication = 0; cancelled_forwarding = 1; } if (options.challenge_response_authentication) { error("Challenge/response authentication is disabled" " to avoid man-in-the-middle attacks."); options.challenge_response_authentication = 0; cancelled_forwarding = 1; } if (options.forward_agent) { error("Agent forwarding is disabled to avoid " "man-in-the-middle attacks."); options.forward_agent = 0; cancelled_forwarding = 1; } if (options.forward_x11) { error("X11 forwarding is disabled to avoid " "man-in-the-middle attacks."); options.forward_x11 = 0; cancelled_forwarding = 1; } if (options.num_local_forwards > 0 || options.num_remote_forwards > 0) { error("Port forwarding is disabled to avoid " "man-in-the-middle attacks."); options.num_local_forwards = options.num_remote_forwards = 0; cancelled_forwarding = 1; } if (options.tun_open != SSH_TUNMODE_NO) { error("Tunnel forwarding is disabled to avoid " "man-in-the-middle attacks."); options.tun_open = SSH_TUNMODE_NO; cancelled_forwarding = 1; } if (options.exit_on_forward_failure && cancelled_forwarding) fatal("Error: forwarding disabled due to host key " "check failure"); /* * XXX Should permit the user to change to use the new id. * This could be done by converting the host key to an * identifying sentence, tell that the host identifies itself * by that sentence, and ask the user if he/she whishes to * accept the authentication. */ break; case HOST_FOUND: fatal("internal error"); break; } if (options.check_host_ip && host_status != HOST_CHANGED && ip_status == HOST_CHANGED) { snprintf(msg, sizeof(msg), "Warning: the %s host key for '%.200s' " "differs from the key for the IP address '%.128s'" "\nOffending key for IP in %s:%d", type, host, ip, ip_file, ip_line); if (host_status == HOST_OK) { len = strlen(msg); snprintf(msg + len, sizeof(msg) - len, "\nMatching host key in %s:%d", host_file, host_line); } if (options.strict_host_key_checking == 1) { logit("%s", msg); error("Exiting, you have requested strict checking."); goto fail; } else if (options.strict_host_key_checking == 2) { strlcat(msg, "\nAre you sure you want " "to continue connecting (yes/no)? ", sizeof(msg)); if (!confirm(msg)) goto fail; } else { logit("%s", msg); } } xfree(ip); xfree(host); return 0; fail: xfree(ip); xfree(host); return -1; } /* returns 0 if key verifies or -1 if key does NOT verify */ int verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) { struct stat st; int flags = 0; if (options.verify_host_key_dns && verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { if (flags & DNS_VERIFY_FOUND) { if (options.verify_host_key_dns == 1 && flags & DNS_VERIFY_MATCH && flags & DNS_VERIFY_SECURE) return 0; if (flags & DNS_VERIFY_MATCH) { matching_host_key_dns = 1; } else { warn_changed_key(host_key); error("Update the SSHFP RR in DNS with the new " "host key to get rid of this message."); } } } /* return ok if the key can be found in an old keyfile */ if (stat(options.system_hostfile2, &st) == 0 || stat(options.user_hostfile2, &st) == 0) { if (check_host_key(host, hostaddr, options.port, host_key, RDONLY, options.user_hostfile2, options.system_hostfile2) == 0) return 0; } return check_host_key(host, hostaddr, options.port, host_key, RDRW, options.user_hostfile, options.system_hostfile); } /* * Starts a dialog with the server, and authenticates the current user on the * server. This does not need any extra privileges. The basic connection * to the server must already have been established before this is called. * If login fails, this function prints an error and never returns. * This function does not require super-user privileges. */ void ssh_login(Sensitive *sensitive, const char *orighost, struct sockaddr *hostaddr, struct passwd *pw, int timeout_ms) { char *host, *cp; char *server_user, *local_user; local_user = xstrdup(pw->pw_name); server_user = options.user ? options.user : local_user; /* Convert the user-supplied hostname into all lowercase. */ host = xstrdup(orighost); for (cp = host; *cp; cp++) if (isupper(*cp)) *cp = (char)tolower(*cp); /* Exchange protocol version identification strings with the server. */ ssh_exchange_identification(timeout_ms); /* Put the connection into non-blocking mode. */ packet_set_nonblocking(); /* key exchange */ /* authenticate user */ if (compat20) { ssh_kex2(host, hostaddr); ssh_userauth2(local_user, server_user, host, sensitive); } else { ssh_kex(host, hostaddr); ssh_userauth1(local_user, server_user, host, sensitive); } xfree(local_user); } void ssh_put_password(char *password) { int size; char *padded; if (datafellows & SSH_BUG_PASSWORDPAD) { packet_put_cstring(password); return; } size = roundup(strlen(password) + 1, 32); padded = xcalloc(1, size); strlcpy(padded, password, size); packet_put_string(padded, size); memset(padded, 0, size); xfree(padded); } static int show_key_from_file(const char *file, const char *host, int keytype) { Key *found; char *fp, *ra; int line, ret; found = key_new(keytype); if ((ret = lookup_key_in_hostfile_by_type(file, host, keytype, found, &line))) { fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); ra = key_fingerprint(found, SSH_FP_MD5, SSH_FP_RANDOMART); logit("WARNING: %s key found for host %s\n" "in %s:%d\n" "%s key fingerprint %s.\n%s\n", key_type(found), host, file, line, key_type(found), fp, ra); xfree(ra); xfree(fp); } key_free(found); return (ret); } /* print all known host keys for a given host, but skip keys of given type */ static int show_other_keys(const char *host, Key *key) { int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1}; int i, found = 0; for (i = 0; type[i] != -1; i++) { if (type[i] == key->type) continue; if (type[i] != KEY_RSA1 && show_key_from_file(options.user_hostfile2, host, type[i])) { found = 1; continue; } if (type[i] != KEY_RSA1 && show_key_from_file(options.system_hostfile2, host, type[i])) { found = 1; continue; } if (show_key_from_file(options.user_hostfile, host, type[i])) { found = 1; continue; } if (show_key_from_file(options.system_hostfile, host, type[i])) { found = 1; continue; } debug2("no key of type %d for host %s", type[i], host); } return (found); } static void warn_changed_key(Key *host_key) { char *fp; const char *type = key_type(host_key); fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); error("It is also possible that the %s host key has just been changed.", type); error("The fingerprint for the %s key sent by the remote host is\n%s.", type, fp); error("Please contact your system administrator."); xfree(fp); } /* * Execute a local command */ int ssh_local_cmd(const char *args) { char *shell; pid_t pid; int status; if (!options.permit_local_command || args == NULL || !*args) return (1); if ((shell = getenv("SHELL")) == NULL) shell = _PATH_BSHELL; pid = fork(); if (pid == 0) { debug3("Executing %s -c \"%s\"", shell, args); execl(shell, shell, "-c", args, (char *)NULL); error("Couldn't execute %s -c \"%s\": %s", shell, args, strerror(errno)); _exit(1); } else if (pid == -1) fatal("fork failed: %.100s", strerror(errno)); while (waitpid(pid, &status, 0) == -1) if (errno != EINTR) fatal("Couldn't wait for child: %s", strerror(errno)); if (!WIFEXITED(status)) return (1); return (WEXITSTATUS(status)); }