diff options
Diffstat (limited to 'crypto/openssh/sshconnect.c')
| -rw-r--r-- | crypto/openssh/sshconnect.c | 1106 |
1 files changed, 1106 insertions, 0 deletions
diff --git a/crypto/openssh/sshconnect.c b/crypto/openssh/sshconnect.c new file mode 100644 index 0000000..a222233 --- /dev/null +++ b/crypto/openssh/sshconnect.c @@ -0,0 +1,1106 @@ +/* $OpenBSD: sshconnect.c,v 1.200 2006/10/10 10:12:45 markus Exp $ */ +/* + * 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" + +#include <sys/types.h> +#include <sys/wait.h> +#include <sys/stat.h> +#include <sys/socket.h> +#ifdef HAVE_SYS_TIME_H +# include <sys/time.h> +#endif + +#include <netinet/in.h> +#include <arpa/inet.h> + +#include <ctype.h> +#include <errno.h> +#include <netdb.h> +#ifdef HAVE_PATHS_H +#include <paths.h> +#endif +#include <pwd.h> +#include <stdarg.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> + +#include "xmalloc.h" +#include "key.h" +#include "hostfile.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; + +#ifndef INET6_ADDRSTRLEN /* for non IPv6 machines */ +#define INET6_ADDRSTRLEN 46 +#endif + +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 strport[NI_MAXSERV]; + + /* 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] = _PATH_BSHELL; + 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]); + + /* 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, "0", &hints, &res); + if (gaierr) { + error("getaddrinfo: %s: %s", options.bind_address, + 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 timeout) +{ + fd_set *fdset; + struct timeval tv; + socklen_t optlen; + int optval, rc, result = -1; + + if (timeout <= 0) + return (connect(sockfd, serv_addr, addrlen)); + + set_nonblock(sockfd); + rc = connect(sockfd, serv_addr, addrlen); + if (rc == 0) { + unset_nonblock(sockfd); + return (0); + } + if (errno != EINPROGRESS) + return (-1); + + fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), + sizeof(fd_mask)); + FD_SET(sockfd, fdset); + tv.tv_sec = timeout; + tv.tv_usec = 0; + + 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); + 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 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: %.100s: %s", __progname, host, + 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, + options.connection_timeout) >= 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 (options.tcp_keep_alive && + 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); + + return 0; +} + +/* + * Waits for the server identification string, and sends our own + * identification string. + */ +static void +ssh_exchange_identification(void) +{ + 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; + + /* Read other side's version identification. */ + for (n = 0;;) { + for (i = 0; i < sizeof(buf) - 1; i++) { + size_t 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); + + /* + * 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\n", + compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, + compat20 ? PROTOCOL_MINOR_2 : minor1, + SSH_VERSION); + 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; + HostStatus host_status; + HostStatus ip_status; + int r, local = 0, host_ip_differ = 0; + int salen; + char ntop[NI_MAXHOST]; + char msg[1024]; + int len, host_line, ip_line; + 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; + salen = sizeof(struct sockaddr_in); + break; + case AF_INET6: + local = IN6_IS_ADDR_LOOPBACK( + &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); + salen = sizeof(struct sockaddr_in6); + break; + default: + local = 0; + salen = sizeof(struct sockaddr_storage); + 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, salen, ntop, sizeof(ntop), + NULL, 0, NI_NUMERICHOST) != 0) + fatal("check_host_key: getnameinfo failed"); + ip = put_host_port(ntop, port); + } else { + ip = xstrdup("<no hostip for proxy command>"); + } + /* + * 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); + } + 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, 2, + 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); + 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.\n%s" + "Are you sure you want to continue connecting " + "(yes/no)? ", + host, ip, msg1, type, fp, msg2); + 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 according 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; + } + 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; + } + if (options.challenge_response_authentication) { + error("Challenge/response authentication is disabled" + " to avoid man-in-the-middle attacks."); + options.challenge_response_authentication = 0; + } + if (options.forward_agent) { + error("Agent forwarding is disabled to avoid " + "man-in-the-middle attacks."); + options.forward_agent = 0; + } + if (options.forward_x11) { + error("X11 forwarding is disabled to avoid " + "man-in-the-middle attacks."); + options.forward_x11 = 0; + } + 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; + } + 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; + } + /* + * 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) +{ + 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(); + + /* 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; + 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); + logit("WARNING: %s key found for host %s\n" + "in %s:%d\n" + "%s key fingerprint %s.", + key_type(found), host, file, line, + key_type(found), fp); + 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)); +} |
