Annotation of src/usr.bin/ssh/sshconnect.c, Revision 1.194
1.194 ! stevesk 1: /* $OpenBSD: sshconnect.c,v 1.193 2006/07/22 20:48:23 stevesk Exp $ */
1.1 deraadt 2: /*
1.39 deraadt 3: * Author: Tatu Ylonen <ylo@cs.hut.fi>
4: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5: * All rights reserved
6: * Code to connect to a remote host, and to perform the client side of the
7: * login (authentication) dialog.
1.78 deraadt 8: *
9: * As far as I am concerned, the code I have written for this software
10: * can be used freely for any purpose. Any derived versions of this
11: * software must be clearly marked as such, and if the derived work is
12: * incompatible with the protocol description in the RFC file, it must be
13: * called by a name other than "ssh" or "Secure Shell".
1.39 deraadt 14: */
1.1 deraadt 15:
16: #include "includes.h"
1.174 stevesk 17:
18: #include <sys/types.h>
19: #include <sys/wait.h>
1.175 stevesk 20: #include <sys/stat.h>
1.187 stevesk 21: #include <sys/socket.h>
22:
23: #include <netinet/in.h>
1.172 stevesk 24:
1.176 stevesk 25: #include <ctype.h>
1.190 stevesk 26: #include <errno.h>
1.191 stevesk 27: #include <netdb.h>
1.172 stevesk 28: #include <paths.h>
1.188 stevesk 29: #include <pwd.h>
1.193 stevesk 30: #include <string.h>
1.192 stevesk 31: #include <unistd.h>
1.71 markus 32:
1.91 markus 33: #include "ssh.h"
1.1 deraadt 34: #include "xmalloc.h"
35: #include "rsa.h"
1.59 markus 36: #include "buffer.h"
1.1 deraadt 37: #include "packet.h"
38: #include "uidswap.h"
1.21 markus 39: #include "compat.h"
1.58 markus 40: #include "key.h"
1.71 markus 41: #include "sshconnect.h"
1.58 markus 42: #include "hostfile.h"
1.91 markus 43: #include "log.h"
44: #include "readconf.h"
45: #include "atomicio.h"
46: #include "misc.h"
1.140 jakob 47: #include "dns.h"
1.186 stevesk 48: #include "version.h"
1.140 jakob 49:
1.70 markus 50: char *client_version_string = NULL;
51: char *server_version_string = NULL;
1.59 markus 52:
1.169 stevesk 53: static int matching_host_key_dns = 0;
1.145 jakob 54:
1.124 markus 55: /* import */
1.43 markus 56: extern Options options;
1.50 markus 57: extern char *__progname;
1.124 markus 58: extern uid_t original_real_uid;
59: extern uid_t original_effective_uid;
1.135 djm 60: extern pid_t proxy_command_pid;
1.91 markus 61:
1.132 markus 62: static int show_other_keys(const char *, Key *);
1.150 jakob 63: static void warn_changed_key(Key *);
1.132 markus 64:
1.39 deraadt 65: /*
66: * Connect to the given ssh server using a proxy command.
67: */
1.109 itojun 68: static int
1.124 markus 69: ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
1.1 deraadt 70: {
1.164 djm 71: char *command_string, *tmp;
1.38 markus 72: int pin[2], pout[2];
1.69 deraadt 73: pid_t pid;
1.49 markus 74: char strport[NI_MAXSERV];
1.38 markus 75:
76: /* Convert the port number into a string. */
1.49 markus 77: snprintf(strport, sizeof strport, "%hu", port);
1.38 markus 78:
1.135 djm 79: /*
80: * Build the final command string in the buffer by making the
81: * appropriate substitutions to the given proxy command.
82: *
1.154 djm 83: * Use "exec" to avoid "sh -c" processes on some platforms
1.135 djm 84: * (e.g. Solaris)
85: */
1.179 djm 86: xasprintf(&tmp, "exec %s", proxy_command);
1.164 djm 87: command_string = percent_expand(tmp, "h", host,
88: "p", strport, (char *)NULL);
89: xfree(tmp);
1.38 markus 90:
91: /* Create pipes for communicating with the proxy. */
92: if (pipe(pin) < 0 || pipe(pout) < 0)
93: fatal("Could not create pipes to communicate with the proxy: %.100s",
1.118 deraadt 94: strerror(errno));
1.38 markus 95:
96: debug("Executing proxy command: %.500s", command_string);
97:
98: /* Fork and execute the proxy command. */
99: if ((pid = fork()) == 0) {
100: char *argv[10];
101:
102: /* Child. Permanently give up superuser privileges. */
1.184 markus 103: permanently_drop_suid(original_real_uid);
1.38 markus 104:
105: /* Redirect stdin and stdout. */
106: close(pin[1]);
107: if (pin[0] != 0) {
108: if (dup2(pin[0], 0) < 0)
109: perror("dup2 stdin");
110: close(pin[0]);
111: }
112: close(pout[0]);
113: if (dup2(pout[1], 1) < 0)
114: perror("dup2 stdout");
115: /* Cannot be 1 because pin allocated two descriptors. */
116: close(pout[1]);
117:
118: /* Stderr is left as it is so that error messages get
119: printed on the user's terminal. */
1.89 markus 120: argv[0] = _PATH_BSHELL;
1.38 markus 121: argv[1] = "-c";
122: argv[2] = command_string;
123: argv[3] = NULL;
124:
125: /* Execute the proxy command. Note that we gave up any
126: extra privileges above. */
1.89 markus 127: execv(argv[0], argv);
128: perror(argv[0]);
1.38 markus 129: exit(1);
130: }
131: /* Parent. */
132: if (pid < 0)
133: fatal("fork failed: %.100s", strerror(errno));
1.135 djm 134: else
135: proxy_command_pid = pid; /* save pid to clean up later */
1.38 markus 136:
137: /* Close child side of the descriptors. */
138: close(pin[0]);
139: close(pout[1]);
140:
141: /* Free the command name. */
1.164 djm 142: xfree(command_string);
1.38 markus 143:
144: /* Set the connection file descriptors. */
145: packet_set_connection(pout[0], pin[1]);
1.1 deraadt 146:
1.110 markus 147: /* Indicate OK return */
148: return 0;
1.1 deraadt 149: }
150:
1.39 deraadt 151: /*
152: * Creates a (possibly privileged) socket for use as the ssh connection.
153: */
1.109 itojun 154: static int
1.139 markus 155: ssh_create_socket(int privileged, struct addrinfo *ai)
1.1 deraadt 156: {
1.105 markus 157: int sock, gaierr;
158: struct addrinfo hints, *res;
1.1 deraadt 159:
1.40 markus 160: /*
161: * If we are running as root and want to connect to a privileged
162: * port, bind our own socket to a privileged port.
163: */
1.38 markus 164: if (privileged) {
165: int p = IPPORT_RESERVED - 1;
1.124 markus 166: PRIV_START;
1.139 markus 167: sock = rresvport_af(&p, ai->ai_family);
1.124 markus 168: PRIV_END;
1.38 markus 169: if (sock < 0)
1.139 markus 170: error("rresvport: af=%d %.100s", ai->ai_family,
171: strerror(errno));
1.55 markus 172: else
173: debug("Allocated local port %d.", p);
1.105 markus 174: return sock;
175: }
1.139 markus 176: sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
1.105 markus 177: if (sock < 0)
178: error("socket: %.100s", strerror(errno));
179:
180: /* Bind the socket to an alternative local IP address */
181: if (options.bind_address == NULL)
182: return sock;
183:
184: memset(&hints, 0, sizeof(hints));
1.139 markus 185: hints.ai_family = ai->ai_family;
186: hints.ai_socktype = ai->ai_socktype;
187: hints.ai_protocol = ai->ai_protocol;
1.105 markus 188: hints.ai_flags = AI_PASSIVE;
189: gaierr = getaddrinfo(options.bind_address, "0", &hints, &res);
190: if (gaierr) {
191: error("getaddrinfo: %s: %s", options.bind_address,
192: gai_strerror(gaierr));
193: close(sock);
194: return -1;
195: }
196: if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
197: error("bind: %s: %s", options.bind_address, strerror(errno));
198: close(sock);
199: freeaddrinfo(res);
200: return -1;
1.38 markus 201: }
1.105 markus 202: freeaddrinfo(res);
1.38 markus 203: return sock;
1.1 deraadt 204: }
205:
1.141 djm 206: static int
207: timeout_connect(int sockfd, const struct sockaddr *serv_addr,
208: socklen_t addrlen, int timeout)
209: {
210: fd_set *fdset;
211: struct timeval tv;
212: socklen_t optlen;
1.179 djm 213: int optval, rc, result = -1;
1.141 djm 214:
215: if (timeout <= 0)
216: return (connect(sockfd, serv_addr, addrlen));
217:
1.156 djm 218: set_nonblock(sockfd);
1.141 djm 219: rc = connect(sockfd, serv_addr, addrlen);
1.156 djm 220: if (rc == 0) {
221: unset_nonblock(sockfd);
1.141 djm 222: return (0);
1.156 djm 223: }
1.141 djm 224: if (errno != EINPROGRESS)
225: return (-1);
226:
1.179 djm 227: fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
228: sizeof(fd_mask));
1.141 djm 229: FD_SET(sockfd, fdset);
230: tv.tv_sec = timeout;
231: tv.tv_usec = 0;
232:
1.162 deraadt 233: for (;;) {
1.141 djm 234: rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
235: if (rc != -1 || errno != EINTR)
236: break;
237: }
238:
1.162 deraadt 239: switch (rc) {
1.141 djm 240: case 0:
241: /* Timed out */
242: errno = ETIMEDOUT;
1.142 djm 243: break;
1.141 djm 244: case -1:
245: /* Select error */
1.154 djm 246: debug("select: %s", strerror(errno));
1.142 djm 247: break;
1.141 djm 248: case 1:
249: /* Completed or failed */
250: optval = 0;
251: optlen = sizeof(optval);
1.154 djm 252: if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
1.148 markus 253: &optlen) == -1) {
1.154 djm 254: debug("getsockopt: %s", strerror(errno));
1.142 djm 255: break;
1.148 markus 256: }
1.141 djm 257: if (optval != 0) {
258: errno = optval;
1.142 djm 259: break;
1.141 djm 260: }
1.142 djm 261: result = 0;
1.156 djm 262: unset_nonblock(sockfd);
1.141 djm 263: break;
264: default:
265: /* Should not occur */
266: fatal("Bogus return (%d) from select()", rc);
267: }
268:
1.142 djm 269: xfree(fdset);
270: return (result);
1.141 djm 271: }
272:
1.39 deraadt 273: /*
1.49 markus 274: * Opens a TCP/IP connection to the remote server on the given host.
275: * The address of the remote host will be returned in hostaddr.
1.124 markus 276: * If port is 0, the default port will be used. If needpriv is true,
1.39 deraadt 277: * a privileged port will be allocated to make the connection.
1.124 markus 278: * This requires super-user privileges if needpriv is true.
1.39 deraadt 279: * Connection_attempts specifies the maximum number of tries (one per
280: * second). If proxy_command is non-NULL, it specifies the command (with %h
281: * and %p substituted for host and port, respectively) to use to contact
282: * the daemon.
283: */
1.38 markus 284: int
1.49 markus 285: ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
1.115 markus 286: u_short port, int family, int connection_attempts,
1.124 markus 287: int needpriv, const char *proxy_command)
1.1 deraadt 288: {
1.90 markus 289: int gaierr;
290: int on = 1;
1.49 markus 291: int sock = -1, attempt;
1.90 markus 292: char ntop[NI_MAXHOST], strport[NI_MAXSERV];
1.49 markus 293: struct addrinfo hints, *ai, *aitop;
1.38 markus 294:
1.136 markus 295: debug2("ssh_connect: needpriv %d", needpriv);
1.38 markus 296:
297: /* If a proxy command is given, connect using it. */
298: if (proxy_command != NULL)
1.124 markus 299: return ssh_proxy_connect(host, port, proxy_command);
1.38 markus 300:
301: /* No proxy command. */
302:
1.49 markus 303: memset(&hints, 0, sizeof(hints));
1.115 markus 304: hints.ai_family = family;
1.49 markus 305: hints.ai_socktype = SOCK_STREAM;
1.126 deraadt 306: snprintf(strport, sizeof strport, "%u", port);
1.49 markus 307: if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
1.50 markus 308: fatal("%s: %.100s: %s", __progname, host,
309: gai_strerror(gaierr));
1.38 markus 310:
1.181 markus 311: for (attempt = 0; attempt < connection_attempts; attempt++) {
1.38 markus 312: if (attempt > 0)
313: debug("Trying again...");
314:
1.181 markus 315: /*
316: * Loop through addresses for this host, and try each one in
317: * sequence until the connection succeeds.
318: */
1.49 markus 319: for (ai = aitop; ai; ai = ai->ai_next) {
320: if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
321: continue;
322: if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
323: ntop, sizeof(ntop), strport, sizeof(strport),
324: NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
325: error("ssh_connect: getnameinfo failed");
326: continue;
327: }
328: debug("Connecting to %.200s [%.100s] port %s.",
329: host, ntop, strport);
330:
331: /* Create a socket for connecting. */
1.139 markus 332: sock = ssh_create_socket(needpriv, ai);
1.49 markus 333: if (sock < 0)
1.110 markus 334: /* Any error is already output */
1.49 markus 335: continue;
336:
1.141 djm 337: if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
338: options.connection_timeout) >= 0) {
1.49 markus 339: /* Successful connection. */
1.102 markus 340: memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
1.38 markus 341: break;
1.49 markus 342: } else {
1.131 itojun 343: debug("connect to address %s port %s: %s",
344: ntop, strport, strerror(errno));
1.38 markus 345: close(sock);
1.181 markus 346: sock = -1;
1.38 markus 347: }
348: }
1.181 markus 349: if (sock != -1)
1.49 markus 350: break; /* Successful connection. */
1.1 deraadt 351:
1.38 markus 352: /* Sleep a moment before retrying. */
353: sleep(1);
354: }
1.49 markus 355:
356: freeaddrinfo(aitop);
357:
1.38 markus 358: /* Return failure if we didn't get a successful connection. */
1.181 markus 359: if (sock == -1) {
1.159 markus 360: error("ssh: connect to host %s port %s: %s",
1.130 itojun 361: host, strport, strerror(errno));
1.159 markus 362: return (-1);
1.130 itojun 363: }
1.38 markus 364:
365: debug("Connection established.");
1.90 markus 366:
1.155 markus 367: /* Set SO_KEEPALIVE if requested. */
368: if (options.tcp_keep_alive &&
1.90 markus 369: setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
370: sizeof(on)) < 0)
371: error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1.38 markus 372:
373: /* Set the connection. */
374: packet_set_connection(sock, sock);
1.1 deraadt 375:
1.110 markus 376: return 0;
1.59 markus 377: }
378:
1.43 markus 379: /*
1.39 deraadt 380: * Waits for the server identification string, and sends our own
381: * identification string.
382: */
1.109 itojun 383: static void
1.95 itojun 384: ssh_exchange_identification(void)
1.1 deraadt 385: {
1.38 markus 386: char buf[256], remote_version[256]; /* must be same size! */
1.165 djm 387: int remote_major, remote_minor, mismatch;
1.38 markus 388: int connection_in = packet_get_connection_in();
389: int connection_out = packet_get_connection_out();
1.93 stevesk 390: int minor1 = PROTOCOL_MINOR_1;
1.185 djm 391: u_int i, n;
1.38 markus 392:
1.163 avsm 393: /* Read other side's version identification. */
1.185 djm 394: for (n = 0;;) {
1.75 markus 395: for (i = 0; i < sizeof(buf) - 1; i++) {
1.163 avsm 396: size_t len = atomicio(read, connection_in, &buf[i], 1);
397:
1.167 djm 398: if (len != 1 && errno == EPIPE)
1.163 avsm 399: fatal("ssh_exchange_identification: Connection closed by remote host");
400: else if (len != 1)
1.75 markus 401: fatal("ssh_exchange_identification: read: %.100s", strerror(errno));
402: if (buf[i] == '\r') {
403: buf[i] = '\n';
404: buf[i + 1] = 0;
405: continue; /**XXX wait for \n */
406: }
407: if (buf[i] == '\n') {
408: buf[i + 1] = 0;
409: break;
410: }
1.185 djm 411: if (++n > 65536)
412: fatal("ssh_exchange_identification: No banner received");
1.38 markus 413: }
1.75 markus 414: buf[sizeof(buf) - 1] = 0;
1.76 markus 415: if (strncmp(buf, "SSH-", 4) == 0)
1.38 markus 416: break;
1.75 markus 417: debug("ssh_exchange_identification: %s", buf);
1.38 markus 418: }
1.59 markus 419: server_version_string = xstrdup(buf);
1.38 markus 420:
1.40 markus 421: /*
422: * Check that the versions match. In future this might accept
423: * several versions and set appropriate flags to handle them.
424: */
1.59 markus 425: if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
426: &remote_major, &remote_minor, remote_version) != 3)
1.38 markus 427: fatal("Bad remote protocol version identification: '%.100s'", buf);
428: debug("Remote protocol version %d.%d, remote software version %.100s",
1.118 deraadt 429: remote_major, remote_minor, remote_version);
1.38 markus 430:
1.59 markus 431: compat_datafellows(remote_version);
1.64 markus 432: mismatch = 0;
1.59 markus 433:
1.116 deraadt 434: switch (remote_major) {
1.64 markus 435: case 1:
436: if (remote_minor == 99 &&
437: (options.protocol & SSH_PROTO_2) &&
438: !(options.protocol & SSH_PROTO_1_PREFERRED)) {
439: enable_compat20();
440: break;
441: }
442: if (!(options.protocol & SSH_PROTO_1)) {
443: mismatch = 1;
444: break;
445: }
446: if (remote_minor < 3) {
447: fatal("Remote machine has too old SSH software version.");
1.81 markus 448: } else if (remote_minor == 3 || remote_minor == 4) {
1.64 markus 449: /* We speak 1.3, too. */
450: enable_compat13();
1.81 markus 451: minor1 = 3;
1.64 markus 452: if (options.forward_agent) {
1.138 itojun 453: logit("Agent forwarding disabled for protocol 1.3");
1.64 markus 454: options.forward_agent = 0;
455: }
456: }
457: break;
458: case 2:
459: if (options.protocol & SSH_PROTO_2) {
460: enable_compat20();
461: break;
1.38 markus 462: }
1.64 markus 463: /* FALLTHROUGH */
1.68 markus 464: default:
1.64 markus 465: mismatch = 1;
466: break;
1.38 markus 467: }
1.64 markus 468: if (mismatch)
1.38 markus 469: fatal("Protocol major versions differ: %d vs. %d",
1.64 markus 470: (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
471: remote_major);
1.38 markus 472: /* Send our own protocol version identification. */
473: snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
1.64 markus 474: compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
1.81 markus 475: compat20 ? PROTOCOL_MINOR_2 : minor1,
1.59 markus 476: SSH_VERSION);
1.146 deraadt 477: if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf))
1.38 markus 478: fatal("write: %.100s", strerror(errno));
1.59 markus 479: client_version_string = xstrdup(buf);
480: chop(client_version_string);
481: chop(server_version_string);
482: debug("Local version string %.100s", client_version_string);
1.1 deraadt 483: }
484:
1.96 markus 485: /* defaults to 'no' */
1.109 itojun 486: static int
1.112 markus 487: confirm(const char *prompt)
1.1 deraadt 488: {
1.119 markus 489: const char *msg, *again = "Please type 'yes' or 'no': ";
490: char *p;
491: int ret = -1;
1.96 markus 492:
493: if (options.batch_mode)
494: return 0;
1.119 markus 495: for (msg = prompt;;msg = again) {
496: p = read_passphrase(msg, RP_ECHO);
497: if (p == NULL ||
498: (p[0] == '\0') || (p[0] == '\n') ||
499: strncasecmp(p, "no", 2) == 0)
500: ret = 0;
1.127 markus 501: if (p && strncasecmp(p, "yes", 3) == 0)
1.119 markus 502: ret = 1;
503: if (p)
504: xfree(p);
505: if (ret != -1)
506: return ret;
1.1 deraadt 507: }
508: }
509:
1.39 deraadt 510: /*
1.108 markus 511: * check whether the supplied host key is valid, return -1 if the key
512: * is not valid. the user_hostfile will not be updated if 'readonly' is true.
1.39 deraadt 513: */
1.109 itojun 514: static int
1.189 dtucker 515: check_host_key(char *hostname, struct sockaddr *hostaddr, Key *host_key,
1.108 markus 516: int readonly, const char *user_hostfile, const char *system_hostfile)
1.1 deraadt 517: {
1.58 markus 518: Key *file_key;
1.152 jakob 519: const char *type = key_type(host_key);
1.189 dtucker 520: char *ip = NULL, *host = NULL;
1.100 markus 521: char hostline[1000], *hostp, *fp;
1.38 markus 522: HostStatus host_status;
523: HostStatus ip_status;
1.161 djm 524: int r, local = 0, host_ip_differ = 0;
1.49 markus 525: char ntop[NI_MAXHOST];
1.119 markus 526: char msg[1024];
1.145 jakob 527: int len, host_line, ip_line;
1.85 markus 528: const char *host_file = NULL, *ip_file = NULL;
1.49 markus 529:
530: /*
531: * Force accepting of the host key for loopback/localhost. The
532: * problem is that if the home directory is NFS-mounted to multiple
533: * machines, localhost will refer to a different machine in each of
534: * them, and the user will get bogus HOST_CHANGED warnings. This
535: * essentially disables host authentication for localhost; however,
536: * this is probably not a real problem.
537: */
1.70 markus 538: /** hostaddr == 0! */
1.49 markus 539: switch (hostaddr->sa_family) {
540: case AF_INET:
1.108 markus 541: local = (ntohl(((struct sockaddr_in *)hostaddr)->
1.168 djm 542: sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
1.49 markus 543: break;
544: case AF_INET6:
1.108 markus 545: local = IN6_IS_ADDR_LOOPBACK(
546: &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
1.49 markus 547: break;
548: default:
549: local = 0;
550: break;
551: }
1.111 markus 552: if (options.no_host_authentication_for_localhost == 1 && local &&
553: options.host_key_alias == NULL) {
1.88 markus 554: debug("Forcing accepting of host key for "
555: "loopback/localhost.");
1.108 markus 556: return 0;
1.49 markus 557: }
1.42 markus 558:
559: /*
1.88 markus 560: * We don't have the remote ip-address for connections
561: * using a proxy command
1.42 markus 562: */
1.84 markus 563: if (options.proxy_command == NULL) {
564: if (getnameinfo(hostaddr, hostaddr->sa_len, ntop, sizeof(ntop),
1.86 markus 565: NULL, 0, NI_NUMERICHOST) != 0)
1.84 markus 566: fatal("check_host_key: getnameinfo failed");
1.189 dtucker 567: ip = put_host_port(ntop, options.port);
1.84 markus 568: } else {
569: ip = xstrdup("<no hostip for proxy command>");
1.86 markus 570: }
1.88 markus 571: /*
572: * Turn off check_host_ip if the connection is to localhost, via proxy
573: * command or if we don't have a hostname to compare with
574: */
1.189 dtucker 575: if (options.check_host_ip && (local ||
576: strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
1.88 markus 577: options.check_host_ip = 0;
1.86 markus 578:
579: /*
1.189 dtucker 580: * Allow the user to record the key under a different name or
581: * differentiate a non-standard port. This is useful for ssh
582: * tunneling over forwarded connections or if you run multiple
583: * sshd's on different ports on the same machine.
1.86 markus 584: */
585: if (options.host_key_alias != NULL) {
1.189 dtucker 586: host = xstrdup(options.host_key_alias);
1.86 markus 587: debug("using hostkeyalias: %s", host);
1.189 dtucker 588: } else {
589: host = put_host_port(hostname, options.port);
1.84 markus 590: }
1.38 markus 591:
1.46 markus 592: /*
593: * Store the host key from the known host file in here so that we can
594: * compare it with the key for the IP address.
595: */
1.58 markus 596: file_key = key_new(host_key->type);
1.38 markus 597:
1.40 markus 598: /*
1.170 djm 599: * Check if the host key is present in the user's list of known
1.40 markus 600: * hosts or in the systemwide list.
601: */
1.85 markus 602: host_file = user_hostfile;
1.108 markus 603: host_status = check_host_in_hostfile(host_file, host, host_key,
1.118 deraadt 604: file_key, &host_line);
1.85 markus 605: if (host_status == HOST_NEW) {
606: host_file = system_hostfile;
1.108 markus 607: host_status = check_host_in_hostfile(host_file, host, host_key,
608: file_key, &host_line);
1.85 markus 609: }
1.40 markus 610: /*
611: * Also perform check for the ip address, skip the check if we are
612: * localhost or the hostname was an ip address to begin with
613: */
1.88 markus 614: if (options.check_host_ip) {
1.58 markus 615: Key *ip_key = key_new(host_key->type);
1.38 markus 616:
1.85 markus 617: ip_file = user_hostfile;
1.108 markus 618: ip_status = check_host_in_hostfile(ip_file, ip, host_key,
619: ip_key, &ip_line);
1.85 markus 620: if (ip_status == HOST_NEW) {
621: ip_file = system_hostfile;
1.108 markus 622: ip_status = check_host_in_hostfile(ip_file, ip,
623: host_key, ip_key, &ip_line);
1.85 markus 624: }
1.38 markus 625: if (host_status == HOST_CHANGED &&
1.58 markus 626: (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
1.38 markus 627: host_ip_differ = 1;
628:
1.58 markus 629: key_free(ip_key);
1.38 markus 630: } else
631: ip_status = host_status;
632:
1.58 markus 633: key_free(file_key);
1.38 markus 634:
635: switch (host_status) {
636: case HOST_OK:
637: /* The host is known and the key matches. */
1.72 markus 638: debug("Host '%.200s' is known and matches the %s host key.",
639: host, type);
1.85 markus 640: debug("Found key in %s:%d", host_file, host_line);
1.88 markus 641: if (options.check_host_ip && ip_status == HOST_NEW) {
1.108 markus 642: if (readonly)
1.138 itojun 643: logit("%s host key for IP address "
1.108 markus 644: "'%.128s' not in list of known hosts.",
645: type, ip);
646: else if (!add_host_to_hostfile(user_hostfile, ip,
1.160 djm 647: host_key, options.hash_known_hosts))
1.138 itojun 648: logit("Failed to add the %s host key for IP "
1.108 markus 649: "address '%.128s' to the list of known "
650: "hosts (%.30s).", type, ip, user_hostfile);
1.88 markus 651: else
1.138 itojun 652: logit("Warning: Permanently added the %s host "
1.108 markus 653: "key for IP address '%.128s' to the list "
654: "of known hosts.", type, ip);
1.38 markus 655: }
656: break;
657: case HOST_NEW:
1.108 markus 658: if (readonly)
659: goto fail;
1.38 markus 660: /* The host is new. */
661: if (options.strict_host_key_checking == 1) {
1.108 markus 662: /*
663: * User has requested strict host key checking. We
664: * will not add the host key automatically. The only
665: * alternative left is to abort.
666: */
667: error("No %s host key is known for %.200s and you "
668: "have requested strict checking.", type, host);
669: goto fail;
1.38 markus 670: } else if (options.strict_host_key_checking == 2) {
1.145 jakob 671: char msg1[1024], msg2[1024];
672:
673: if (show_other_keys(host, host_key))
674: snprintf(msg1, sizeof(msg1),
1.168 djm 675: "\nbut keys of different type are already"
676: " known for this host.");
1.145 jakob 677: else
678: snprintf(msg1, sizeof(msg1), ".");
1.38 markus 679: /* The default */
1.100 markus 680: fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1.145 jakob 681: msg2[0] = '\0';
682: if (options.verify_host_key_dns) {
1.153 jakob 683: if (matching_host_key_dns)
1.145 jakob 684: snprintf(msg2, sizeof(msg2),
685: "Matching host key fingerprint"
686: " found in DNS.\n");
687: else
688: snprintf(msg2, sizeof(msg2),
689: "No matching host key fingerprint"
690: " found in DNS.\n");
691: }
1.119 markus 692: snprintf(msg, sizeof(msg),
1.108 markus 693: "The authenticity of host '%.200s (%s)' can't be "
1.132 markus 694: "established%s\n"
1.145 jakob 695: "%s key fingerprint is %s.\n%s"
1.108 markus 696: "Are you sure you want to continue connecting "
1.132 markus 697: "(yes/no)? ",
1.145 jakob 698: host, ip, msg1, type, fp, msg2);
1.100 markus 699: xfree(fp);
1.119 markus 700: if (!confirm(msg))
1.108 markus 701: goto fail;
1.38 markus 702: }
1.161 djm 703: /*
704: * If not in strict mode, add the key automatically to the
705: * local known_hosts file.
706: */
1.88 markus 707: if (options.check_host_ip && ip_status == HOST_NEW) {
1.161 djm 708: snprintf(hostline, sizeof(hostline), "%s,%s",
709: host, ip);
1.38 markus 710: hostp = hostline;
1.161 djm 711: if (options.hash_known_hosts) {
712: /* Add hash of host and IP separately */
713: r = add_host_to_hostfile(user_hostfile, host,
714: host_key, options.hash_known_hosts) &&
715: add_host_to_hostfile(user_hostfile, ip,
716: host_key, options.hash_known_hosts);
717: } else {
718: /* Add unhashed "host,ip" */
719: r = add_host_to_hostfile(user_hostfile,
720: hostline, host_key,
721: options.hash_known_hosts);
722: }
723: } else {
724: r = add_host_to_hostfile(user_hostfile, host, host_key,
725: options.hash_known_hosts);
1.38 markus 726: hostp = host;
1.161 djm 727: }
1.38 markus 728:
1.161 djm 729: if (!r)
1.138 itojun 730: logit("Failed to add the host to the list of known "
1.108 markus 731: "hosts (%.500s).", user_hostfile);
1.38 markus 732: else
1.138 itojun 733: logit("Warning: Permanently added '%.200s' (%s) to the "
1.108 markus 734: "list of known hosts.", hostp, type);
1.38 markus 735: break;
736: case HOST_CHANGED:
737: if (options.check_host_ip && host_ip_differ) {
1.158 avsm 738: char *key_msg;
1.38 markus 739: if (ip_status == HOST_NEW)
1.158 avsm 740: key_msg = "is unknown";
1.38 markus 741: else if (ip_status == HOST_OK)
1.158 avsm 742: key_msg = "is unchanged";
1.38 markus 743: else
1.158 avsm 744: key_msg = "has a different value";
1.38 markus 745: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
746: error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
747: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1.72 markus 748: error("The %s host key for %s has changed,", type, host);
1.38 markus 749: error("and the key for the according IP address %s", ip);
1.158 avsm 750: error("%s. This could either mean that", key_msg);
1.38 markus 751: error("DNS SPOOFING is happening or the IP address for the host");
1.85 markus 752: error("and its host key have changed at the same time.");
1.88 markus 753: if (ip_status != HOST_NEW)
1.85 markus 754: error("Offending key for IP in %s:%d", ip_file, ip_line);
1.38 markus 755: }
756: /* The host key has changed. */
1.150 jakob 757: warn_changed_key(host_key);
1.38 markus 758: error("Add correct host key in %.100s to get rid of this message.",
1.87 markus 759: user_hostfile);
1.85 markus 760: error("Offending key in %s:%d", host_file, host_line);
1.38 markus 761:
1.40 markus 762: /*
763: * If strict host key checking is in use, the user will have
764: * to edit the key manually and we can only abort.
765: */
1.108 markus 766: if (options.strict_host_key_checking) {
767: error("%s host key for %.200s has changed and you have "
768: "requested strict checking.", type, host);
769: goto fail;
770: }
1.38 markus 771:
1.40 markus 772: /*
773: * If strict host key checking has not been requested, allow
1.144 djm 774: * the connection but without MITM-able authentication or
1.194 ! stevesk 775: * forwarding.
1.40 markus 776: */
1.38 markus 777: if (options.password_authentication) {
1.108 markus 778: error("Password authentication is disabled to avoid "
779: "man-in-the-middle attacks.");
1.38 markus 780: options.password_authentication = 0;
1.144 djm 781: }
782: if (options.kbd_interactive_authentication) {
783: error("Keyboard-interactive authentication is disabled"
784: " to avoid man-in-the-middle attacks.");
785: options.kbd_interactive_authentication = 0;
786: options.challenge_response_authentication = 0;
787: }
788: if (options.challenge_response_authentication) {
789: error("Challenge/response authentication is disabled"
790: " to avoid man-in-the-middle attacks.");
791: options.challenge_response_authentication = 0;
1.38 markus 792: }
793: if (options.forward_agent) {
1.108 markus 794: error("Agent forwarding is disabled to avoid "
795: "man-in-the-middle attacks.");
1.38 markus 796: options.forward_agent = 0;
1.83 markus 797: }
798: if (options.forward_x11) {
1.108 markus 799: error("X11 forwarding is disabled to avoid "
800: "man-in-the-middle attacks.");
1.83 markus 801: options.forward_x11 = 0;
802: }
1.108 markus 803: if (options.num_local_forwards > 0 ||
804: options.num_remote_forwards > 0) {
805: error("Port forwarding is disabled to avoid "
806: "man-in-the-middle attacks.");
807: options.num_local_forwards =
1.118 deraadt 808: options.num_remote_forwards = 0;
1.194 ! stevesk 809: }
! 810: if (options.tun_open != SSH_TUNMODE_NO) {
! 811: error("Tunnel forwarding is disabled to avoid "
! 812: "man-in-the-middle attacks.");
! 813: options.tun_open = SSH_TUNMODE_NO;
1.38 markus 814: }
1.40 markus 815: /*
816: * XXX Should permit the user to change to use the new id.
817: * This could be done by converting the host key to an
818: * identifying sentence, tell that the host identifies itself
819: * by that sentence, and ask the user if he/she whishes to
820: * accept the authentication.
821: */
1.38 markus 822: break;
1.132 markus 823: case HOST_FOUND:
824: fatal("internal error");
825: break;
1.88 markus 826: }
827:
828: if (options.check_host_ip && host_status != HOST_CHANGED &&
829: ip_status == HOST_CHANGED) {
1.119 markus 830: snprintf(msg, sizeof(msg),
831: "Warning: the %s host key for '%.200s' "
832: "differs from the key for the IP address '%.128s'"
833: "\nOffending key for IP in %s:%d",
834: type, host, ip, ip_file, ip_line);
835: if (host_status == HOST_OK) {
836: len = strlen(msg);
837: snprintf(msg + len, sizeof(msg) - len,
838: "\nMatching host key in %s:%d",
1.125 deraadt 839: host_file, host_line);
1.119 markus 840: }
1.88 markus 841: if (options.strict_host_key_checking == 1) {
1.143 djm 842: logit("%s", msg);
1.108 markus 843: error("Exiting, you have requested strict checking.");
844: goto fail;
1.88 markus 845: } else if (options.strict_host_key_checking == 2) {
1.119 markus 846: strlcat(msg, "\nAre you sure you want "
847: "to continue connecting (yes/no)? ", sizeof(msg));
848: if (!confirm(msg))
1.108 markus 849: goto fail;
1.119 markus 850: } else {
1.143 djm 851: logit("%s", msg);
1.88 markus 852: }
1.38 markus 853: }
1.82 provos 854:
855: xfree(ip);
1.189 dtucker 856: xfree(host);
1.108 markus 857: return 0;
858:
859: fail:
860: xfree(ip);
1.189 dtucker 861: xfree(host);
1.108 markus 862: return -1;
863: }
864:
1.140 jakob 865: /* returns 0 if key verifies or -1 if key does NOT verify */
1.108 markus 866: int
867: verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
868: {
869: struct stat st;
1.153 jakob 870: int flags = 0;
1.140 jakob 871:
1.153 jakob 872: if (options.verify_host_key_dns &&
873: verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
874:
875: if (flags & DNS_VERIFY_FOUND) {
876:
877: if (options.verify_host_key_dns == 1 &&
878: flags & DNS_VERIFY_MATCH &&
879: flags & DNS_VERIFY_SECURE)
880: return 0;
881:
882: if (flags & DNS_VERIFY_MATCH) {
883: matching_host_key_dns = 1;
884: } else {
885: warn_changed_key(host_key);
886: error("Update the SSHFP RR in DNS with the new "
887: "host key to get rid of this message.");
888: }
1.140 jakob 889: }
890: }
1.108 markus 891:
892: /* return ok if the key can be found in an old keyfile */
893: if (stat(options.system_hostfile2, &st) == 0 ||
894: stat(options.user_hostfile2, &st) == 0) {
895: if (check_host_key(host, hostaddr, host_key, /*readonly*/ 1,
896: options.user_hostfile2, options.system_hostfile2) == 0)
897: return 0;
898: }
899: return check_host_key(host, hostaddr, host_key, /*readonly*/ 0,
900: options.user_hostfile, options.system_hostfile);
1.51 markus 901: }
1.70 markus 902:
1.51 markus 903: /*
904: * Starts a dialog with the server, and authenticates the current user on the
905: * server. This does not need any extra privileges. The basic connection
906: * to the server must already have been established before this is called.
907: * If login fails, this function prints an error and never returns.
908: * This function does not require super-user privileges.
909: */
910: void
1.120 markus 911: ssh_login(Sensitive *sensitive, const char *orighost,
1.103 markus 912: struct sockaddr *hostaddr, struct passwd *pw)
1.51 markus 913: {
914: char *host, *cp;
1.70 markus 915: char *server_user, *local_user;
916:
917: local_user = xstrdup(pw->pw_name);
918: server_user = options.user ? options.user : local_user;
1.51 markus 919:
920: /* Convert the user-supplied hostname into all lowercase. */
921: host = xstrdup(orighost);
922: for (cp = host; *cp; cp++)
923: if (isupper(*cp))
1.178 deraadt 924: *cp = (char)tolower(*cp);
1.51 markus 925:
926: /* Exchange protocol version identification strings with the server. */
927: ssh_exchange_identification();
928:
929: /* Put the connection into non-blocking mode. */
930: packet_set_nonblocking();
931:
932: /* key exchange */
933: /* authenticate user */
1.59 markus 934: if (compat20) {
935: ssh_kex2(host, hostaddr);
1.120 markus 936: ssh_userauth2(local_user, server_user, host, sensitive);
1.59 markus 937: } else {
938: ssh_kex(host, hostaddr);
1.120 markus 939: ssh_userauth1(local_user, server_user, host, sensitive);
1.59 markus 940: }
1.182 markus 941: xfree(local_user);
1.97 markus 942: }
943:
944: void
945: ssh_put_password(char *password)
946: {
947: int size;
948: char *padded;
949:
1.99 deraadt 950: if (datafellows & SSH_BUG_PASSWORDPAD) {
1.107 markus 951: packet_put_cstring(password);
1.99 deraadt 952: return;
953: }
1.97 markus 954: size = roundup(strlen(password) + 1, 32);
1.179 djm 955: padded = xcalloc(1, size);
1.97 markus 956: strlcpy(padded, password, size);
957: packet_put_string(padded, size);
958: memset(padded, 0, size);
959: xfree(padded);
1.132 markus 960: }
961:
962: static int
963: show_key_from_file(const char *file, const char *host, int keytype)
964: {
965: Key *found;
966: char *fp;
967: int line, ret;
968:
969: found = key_new(keytype);
970: if ((ret = lookup_key_in_hostfile_by_type(file, host,
971: keytype, found, &line))) {
972: fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
1.138 itojun 973: logit("WARNING: %s key found for host %s\n"
1.133 markus 974: "in %s:%d\n"
1.132 markus 975: "%s key fingerprint %s.",
976: key_type(found), host, file, line,
977: key_type(found), fp);
978: xfree(fp);
979: }
980: key_free(found);
981: return (ret);
982: }
983:
984: /* print all known host keys for a given host, but skip keys of given type */
985: static int
986: show_other_keys(const char *host, Key *key)
987: {
988: int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1};
989: int i, found = 0;
990:
991: for (i = 0; type[i] != -1; i++) {
992: if (type[i] == key->type)
993: continue;
994: if (type[i] != KEY_RSA1 &&
995: show_key_from_file(options.user_hostfile2, host, type[i])) {
996: found = 1;
997: continue;
998: }
999: if (type[i] != KEY_RSA1 &&
1000: show_key_from_file(options.system_hostfile2, host, type[i])) {
1001: found = 1;
1002: continue;
1003: }
1004: if (show_key_from_file(options.user_hostfile, host, type[i])) {
1005: found = 1;
1006: continue;
1007: }
1008: if (show_key_from_file(options.system_hostfile, host, type[i])) {
1009: found = 1;
1010: continue;
1011: }
1012: debug2("no key of type %d for host %s", type[i], host);
1013: }
1014: return (found);
1.150 jakob 1015: }
1016:
1017: static void
1018: warn_changed_key(Key *host_key)
1019: {
1020: char *fp;
1.151 jakob 1021: const char *type = key_type(host_key);
1.150 jakob 1022:
1023: fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1024:
1025: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1026: error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1027: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1028: error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1029: error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1030: error("It is also possible that the %s host key has just been changed.", type);
1031: error("The fingerprint for the %s key sent by the remote host is\n%s.",
1032: type, fp);
1033: error("Please contact your system administrator.");
1034:
1035: xfree(fp);
1.171 reyk 1036: }
1037:
1038: /*
1039: * Execute a local command
1040: */
1041: int
1042: ssh_local_cmd(const char *args)
1043: {
1044: char *shell;
1045: pid_t pid;
1046: int status;
1047:
1048: if (!options.permit_local_command ||
1049: args == NULL || !*args)
1050: return (1);
1051:
1052: if ((shell = getenv("SHELL")) == NULL)
1053: shell = _PATH_BSHELL;
1054:
1055: pid = fork();
1056: if (pid == 0) {
1057: debug3("Executing %s -c \"%s\"", shell, args);
1058: execl(shell, shell, "-c", args, (char *)NULL);
1059: error("Couldn't execute %s -c \"%s\": %s",
1060: shell, args, strerror(errno));
1061: _exit(1);
1062: } else if (pid == -1)
1063: fatal("fork failed: %.100s", strerror(errno));
1064: while (waitpid(pid, &status, 0) == -1)
1065: if (errno != EINTR)
1066: fatal("Couldn't wait for child: %s", strerror(errno));
1067:
1068: if (!WIFEXITED(status))
1069: return (1);
1070:
1071: return (WEXITSTATUS(status));
1.1 deraadt 1072: }