Annotation of src/usr.bin/ssh/sshconnect.c, Revision 1.164
1.1 deraadt 1: /*
1.39 deraadt 2: * Author: Tatu Ylonen <ylo@cs.hut.fi>
3: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4: * All rights reserved
5: * Code to connect to a remote host, and to perform the client side of the
6: * login (authentication) dialog.
1.78 deraadt 7: *
8: * As far as I am concerned, the code I have written for this software
9: * can be used freely for any purpose. Any derived versions of this
10: * software must be clearly marked as such, and if the derived work is
11: * incompatible with the protocol description in the RFC file, it must be
12: * called by a name other than "ssh" or "Secure Shell".
1.39 deraadt 13: */
1.1 deraadt 14:
15: #include "includes.h"
1.164 ! djm 16: RCSID("$OpenBSD: sshconnect.c,v 1.163 2005/05/24 17:32:44 avsm Exp $");
1.1 deraadt 17:
1.66 markus 18: #include <openssl/bn.h>
1.71 markus 19:
1.91 markus 20: #include "ssh.h"
1.1 deraadt 21: #include "xmalloc.h"
22: #include "rsa.h"
1.59 markus 23: #include "buffer.h"
1.1 deraadt 24: #include "packet.h"
25: #include "uidswap.h"
1.21 markus 26: #include "compat.h"
1.58 markus 27: #include "key.h"
1.71 markus 28: #include "sshconnect.h"
1.58 markus 29: #include "hostfile.h"
1.91 markus 30: #include "log.h"
31: #include "readconf.h"
32: #include "atomicio.h"
33: #include "misc.h"
1.51 markus 34:
1.140 jakob 35: #include "dns.h"
36:
1.70 markus 37: char *client_version_string = NULL;
38: char *server_version_string = NULL;
1.59 markus 39:
1.153 jakob 40: int matching_host_key_dns = 0;
1.145 jakob 41:
1.124 markus 42: /* import */
1.43 markus 43: extern Options options;
1.50 markus 44: extern char *__progname;
1.124 markus 45: extern uid_t original_real_uid;
46: extern uid_t original_effective_uid;
1.135 djm 47: extern pid_t proxy_command_pid;
1.91 markus 48:
1.132 markus 49: static int show_other_keys(const char *, Key *);
1.150 jakob 50: static void warn_changed_key(Key *);
1.132 markus 51:
1.39 deraadt 52: /*
53: * Connect to the given ssh server using a proxy command.
54: */
1.109 itojun 55: static int
1.124 markus 56: ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
1.1 deraadt 57: {
1.164 ! djm 58: char *command_string, *tmp;
1.38 markus 59: int pin[2], pout[2];
1.69 deraadt 60: pid_t pid;
1.49 markus 61: char strport[NI_MAXSERV];
1.164 ! djm 62: size_t len;
1.38 markus 63:
64: /* Convert the port number into a string. */
1.49 markus 65: snprintf(strport, sizeof strport, "%hu", port);
1.38 markus 66:
1.135 djm 67: /*
68: * Build the final command string in the buffer by making the
69: * appropriate substitutions to the given proxy command.
70: *
1.154 djm 71: * Use "exec" to avoid "sh -c" processes on some platforms
1.135 djm 72: * (e.g. Solaris)
73: */
1.164 ! djm 74: len = strlen(proxy_command) + 6;
! 75: tmp = xmalloc(len);
! 76: strlcpy(tmp, "exec ", len);
! 77: strlcat(tmp, proxy_command, len);
! 78: command_string = percent_expand(tmp, "h", host,
! 79: "p", strport, (char *)NULL);
! 80: xfree(tmp);
1.38 markus 81:
82: /* Create pipes for communicating with the proxy. */
83: if (pipe(pin) < 0 || pipe(pout) < 0)
84: fatal("Could not create pipes to communicate with the proxy: %.100s",
1.118 deraadt 85: strerror(errno));
1.38 markus 86:
87: debug("Executing proxy command: %.500s", command_string);
88:
89: /* Fork and execute the proxy command. */
90: if ((pid = fork()) == 0) {
91: char *argv[10];
92:
93: /* Child. Permanently give up superuser privileges. */
1.124 markus 94: seteuid(original_real_uid);
95: setuid(original_real_uid);
1.38 markus 96:
97: /* Redirect stdin and stdout. */
98: close(pin[1]);
99: if (pin[0] != 0) {
100: if (dup2(pin[0], 0) < 0)
101: perror("dup2 stdin");
102: close(pin[0]);
103: }
104: close(pout[0]);
105: if (dup2(pout[1], 1) < 0)
106: perror("dup2 stdout");
107: /* Cannot be 1 because pin allocated two descriptors. */
108: close(pout[1]);
109:
110: /* Stderr is left as it is so that error messages get
111: printed on the user's terminal. */
1.89 markus 112: argv[0] = _PATH_BSHELL;
1.38 markus 113: argv[1] = "-c";
114: argv[2] = command_string;
115: argv[3] = NULL;
116:
117: /* Execute the proxy command. Note that we gave up any
118: extra privileges above. */
1.89 markus 119: execv(argv[0], argv);
120: perror(argv[0]);
1.38 markus 121: exit(1);
122: }
123: /* Parent. */
124: if (pid < 0)
125: fatal("fork failed: %.100s", strerror(errno));
1.135 djm 126: else
127: proxy_command_pid = pid; /* save pid to clean up later */
1.38 markus 128:
129: /* Close child side of the descriptors. */
130: close(pin[0]);
131: close(pout[1]);
132:
133: /* Free the command name. */
1.164 ! djm 134: xfree(command_string);
1.38 markus 135:
136: /* Set the connection file descriptors. */
137: packet_set_connection(pout[0], pin[1]);
1.1 deraadt 138:
1.110 markus 139: /* Indicate OK return */
140: return 0;
1.1 deraadt 141: }
142:
1.39 deraadt 143: /*
144: * Creates a (possibly privileged) socket for use as the ssh connection.
145: */
1.109 itojun 146: static int
1.139 markus 147: ssh_create_socket(int privileged, struct addrinfo *ai)
1.1 deraadt 148: {
1.105 markus 149: int sock, gaierr;
150: struct addrinfo hints, *res;
1.1 deraadt 151:
1.40 markus 152: /*
153: * If we are running as root and want to connect to a privileged
154: * port, bind our own socket to a privileged port.
155: */
1.38 markus 156: if (privileged) {
157: int p = IPPORT_RESERVED - 1;
1.124 markus 158: PRIV_START;
1.139 markus 159: sock = rresvport_af(&p, ai->ai_family);
1.124 markus 160: PRIV_END;
1.38 markus 161: if (sock < 0)
1.139 markus 162: error("rresvport: af=%d %.100s", ai->ai_family,
163: strerror(errno));
1.55 markus 164: else
165: debug("Allocated local port %d.", p);
1.105 markus 166: return sock;
167: }
1.139 markus 168: sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
1.105 markus 169: if (sock < 0)
170: error("socket: %.100s", strerror(errno));
171:
172: /* Bind the socket to an alternative local IP address */
173: if (options.bind_address == NULL)
174: return sock;
175:
176: memset(&hints, 0, sizeof(hints));
1.139 markus 177: hints.ai_family = ai->ai_family;
178: hints.ai_socktype = ai->ai_socktype;
179: hints.ai_protocol = ai->ai_protocol;
1.105 markus 180: hints.ai_flags = AI_PASSIVE;
181: gaierr = getaddrinfo(options.bind_address, "0", &hints, &res);
182: if (gaierr) {
183: error("getaddrinfo: %s: %s", options.bind_address,
184: gai_strerror(gaierr));
185: close(sock);
186: return -1;
187: }
188: if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
189: error("bind: %s: %s", options.bind_address, strerror(errno));
190: close(sock);
191: freeaddrinfo(res);
192: return -1;
1.38 markus 193: }
1.105 markus 194: freeaddrinfo(res);
1.38 markus 195: return sock;
1.1 deraadt 196: }
197:
1.141 djm 198: static int
199: timeout_connect(int sockfd, const struct sockaddr *serv_addr,
200: socklen_t addrlen, int timeout)
201: {
202: fd_set *fdset;
203: struct timeval tv;
204: socklen_t optlen;
1.142 djm 205: int fdsetsz, optval, rc, result = -1;
1.141 djm 206:
207: if (timeout <= 0)
208: return (connect(sockfd, serv_addr, addrlen));
209:
1.156 djm 210: set_nonblock(sockfd);
1.141 djm 211: rc = connect(sockfd, serv_addr, addrlen);
1.156 djm 212: if (rc == 0) {
213: unset_nonblock(sockfd);
1.141 djm 214: return (0);
1.156 djm 215: }
1.141 djm 216: if (errno != EINPROGRESS)
217: return (-1);
218:
219: fdsetsz = howmany(sockfd + 1, NFDBITS) * sizeof(fd_mask);
220: fdset = (fd_set *)xmalloc(fdsetsz);
221:
1.147 markus 222: memset(fdset, 0, fdsetsz);
1.141 djm 223: FD_SET(sockfd, fdset);
224: tv.tv_sec = timeout;
225: tv.tv_usec = 0;
226:
1.162 deraadt 227: for (;;) {
1.141 djm 228: rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
229: if (rc != -1 || errno != EINTR)
230: break;
231: }
232:
1.162 deraadt 233: switch (rc) {
1.141 djm 234: case 0:
235: /* Timed out */
236: errno = ETIMEDOUT;
1.142 djm 237: break;
1.141 djm 238: case -1:
239: /* Select error */
1.154 djm 240: debug("select: %s", strerror(errno));
1.142 djm 241: break;
1.141 djm 242: case 1:
243: /* Completed or failed */
244: optval = 0;
245: optlen = sizeof(optval);
1.154 djm 246: if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
1.148 markus 247: &optlen) == -1) {
1.154 djm 248: debug("getsockopt: %s", strerror(errno));
1.142 djm 249: break;
1.148 markus 250: }
1.141 djm 251: if (optval != 0) {
252: errno = optval;
1.142 djm 253: break;
1.141 djm 254: }
1.142 djm 255: result = 0;
1.156 djm 256: unset_nonblock(sockfd);
1.141 djm 257: break;
258: default:
259: /* Should not occur */
260: fatal("Bogus return (%d) from select()", rc);
261: }
262:
1.142 djm 263: xfree(fdset);
264: return (result);
1.141 djm 265: }
266:
1.39 deraadt 267: /*
1.49 markus 268: * Opens a TCP/IP connection to the remote server on the given host.
269: * The address of the remote host will be returned in hostaddr.
1.124 markus 270: * If port is 0, the default port will be used. If needpriv is true,
1.39 deraadt 271: * a privileged port will be allocated to make the connection.
1.124 markus 272: * This requires super-user privileges if needpriv is true.
1.39 deraadt 273: * Connection_attempts specifies the maximum number of tries (one per
274: * second). If proxy_command is non-NULL, it specifies the command (with %h
275: * and %p substituted for host and port, respectively) to use to contact
276: * the daemon.
277: */
1.38 markus 278: int
1.49 markus 279: ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
1.115 markus 280: u_short port, int family, int connection_attempts,
1.124 markus 281: int needpriv, const char *proxy_command)
1.1 deraadt 282: {
1.90 markus 283: int gaierr;
284: int on = 1;
1.49 markus 285: int sock = -1, attempt;
1.90 markus 286: char ntop[NI_MAXHOST], strport[NI_MAXSERV];
1.49 markus 287: struct addrinfo hints, *ai, *aitop;
1.90 markus 288: struct servent *sp;
1.38 markus 289:
1.136 markus 290: debug2("ssh_connect: needpriv %d", needpriv);
1.38 markus 291:
292: /* Get default port if port has not been set. */
293: if (port == 0) {
294: sp = getservbyname(SSH_SERVICE_NAME, "tcp");
295: if (sp)
296: port = ntohs(sp->s_port);
297: else
298: port = SSH_DEFAULT_PORT;
299: }
300: /* If a proxy command is given, connect using it. */
301: if (proxy_command != NULL)
1.124 markus 302: return ssh_proxy_connect(host, port, proxy_command);
1.38 markus 303:
304: /* No proxy command. */
305:
1.49 markus 306: memset(&hints, 0, sizeof(hints));
1.115 markus 307: hints.ai_family = family;
1.49 markus 308: hints.ai_socktype = SOCK_STREAM;
1.126 deraadt 309: snprintf(strport, sizeof strport, "%u", port);
1.49 markus 310: if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
1.50 markus 311: fatal("%s: %.100s: %s", __progname, host,
312: gai_strerror(gaierr));
1.38 markus 313:
1.46 markus 314: /*
315: * Try to connect several times. On some machines, the first time
316: * will sometimes fail. In general socket code appears to behave
317: * quite magically on many machines.
1.110 markus 318: */
319: for (attempt = 0; ;) {
1.38 markus 320: if (attempt > 0)
321: debug("Trying again...");
322:
1.49 markus 323: /* Loop through addresses for this host, and try each one in
1.68 markus 324: sequence until the connection succeeds. */
1.49 markus 325: for (ai = aitop; ai; ai = ai->ai_next) {
326: if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
327: continue;
328: if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
329: ntop, sizeof(ntop), strport, sizeof(strport),
330: NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
331: error("ssh_connect: getnameinfo failed");
332: continue;
333: }
334: debug("Connecting to %.200s [%.100s] port %s.",
335: host, ntop, strport);
336:
337: /* Create a socket for connecting. */
1.139 markus 338: sock = ssh_create_socket(needpriv, ai);
1.49 markus 339: if (sock < 0)
1.110 markus 340: /* Any error is already output */
1.49 markus 341: continue;
342:
1.141 djm 343: if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
344: options.connection_timeout) >= 0) {
1.49 markus 345: /* Successful connection. */
1.102 markus 346: memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
1.38 markus 347: break;
1.49 markus 348: } else {
1.131 itojun 349: debug("connect to address %s port %s: %s",
350: ntop, strport, strerror(errno));
1.40 markus 351: /*
352: * Close the failed socket; there appear to
353: * be some problems when reusing a socket for
354: * which connect() has already returned an
355: * error.
356: */
1.38 markus 357: close(sock);
358: }
359: }
1.49 markus 360: if (ai)
361: break; /* Successful connection. */
1.1 deraadt 362:
1.110 markus 363: attempt++;
364: if (attempt >= connection_attempts)
365: break;
1.38 markus 366: /* Sleep a moment before retrying. */
367: sleep(1);
368: }
1.49 markus 369:
370: freeaddrinfo(aitop);
371:
1.38 markus 372: /* Return failure if we didn't get a successful connection. */
1.130 itojun 373: if (attempt >= connection_attempts) {
1.159 markus 374: error("ssh: connect to host %s port %s: %s",
1.130 itojun 375: host, strport, strerror(errno));
1.159 markus 376: return (-1);
1.130 itojun 377: }
1.38 markus 378:
379: debug("Connection established.");
1.90 markus 380:
1.155 markus 381: /* Set SO_KEEPALIVE if requested. */
382: if (options.tcp_keep_alive &&
1.90 markus 383: setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
384: sizeof(on)) < 0)
385: error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1.38 markus 386:
387: /* Set the connection. */
388: packet_set_connection(sock, sock);
1.1 deraadt 389:
1.110 markus 390: return 0;
1.59 markus 391: }
392:
1.43 markus 393: /*
1.39 deraadt 394: * Waits for the server identification string, and sends our own
395: * identification string.
396: */
1.109 itojun 397: static void
1.95 itojun 398: ssh_exchange_identification(void)
1.1 deraadt 399: {
1.38 markus 400: char buf[256], remote_version[256]; /* must be same size! */
1.64 markus 401: int remote_major, remote_minor, i, mismatch;
1.38 markus 402: int connection_in = packet_get_connection_in();
403: int connection_out = packet_get_connection_out();
1.93 stevesk 404: int minor1 = PROTOCOL_MINOR_1;
1.38 markus 405:
1.163 avsm 406: /* Read other side's version identification. */
1.75 markus 407: for (;;) {
408: for (i = 0; i < sizeof(buf) - 1; i++) {
1.163 avsm 409: size_t len = atomicio(read, connection_in, &buf[i], 1);
410:
411: if (len != 1 && errno == EPIPE)
412: fatal("ssh_exchange_identification: Connection closed by remote host");
413: else if (len != 1)
1.75 markus 414: fatal("ssh_exchange_identification: read: %.100s", strerror(errno));
415: if (buf[i] == '\r') {
416: buf[i] = '\n';
417: buf[i + 1] = 0;
418: continue; /**XXX wait for \n */
419: }
420: if (buf[i] == '\n') {
421: buf[i + 1] = 0;
422: break;
423: }
1.38 markus 424: }
1.75 markus 425: buf[sizeof(buf) - 1] = 0;
1.76 markus 426: if (strncmp(buf, "SSH-", 4) == 0)
1.38 markus 427: break;
1.75 markus 428: debug("ssh_exchange_identification: %s", buf);
1.38 markus 429: }
1.59 markus 430: server_version_string = xstrdup(buf);
1.38 markus 431:
1.40 markus 432: /*
433: * Check that the versions match. In future this might accept
434: * several versions and set appropriate flags to handle them.
435: */
1.59 markus 436: if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
437: &remote_major, &remote_minor, remote_version) != 3)
1.38 markus 438: fatal("Bad remote protocol version identification: '%.100s'", buf);
439: debug("Remote protocol version %d.%d, remote software version %.100s",
1.118 deraadt 440: remote_major, remote_minor, remote_version);
1.38 markus 441:
1.59 markus 442: compat_datafellows(remote_version);
1.64 markus 443: mismatch = 0;
1.59 markus 444:
1.116 deraadt 445: switch (remote_major) {
1.64 markus 446: case 1:
447: if (remote_minor == 99 &&
448: (options.protocol & SSH_PROTO_2) &&
449: !(options.protocol & SSH_PROTO_1_PREFERRED)) {
450: enable_compat20();
451: break;
452: }
453: if (!(options.protocol & SSH_PROTO_1)) {
454: mismatch = 1;
455: break;
456: }
457: if (remote_minor < 3) {
458: fatal("Remote machine has too old SSH software version.");
1.81 markus 459: } else if (remote_minor == 3 || remote_minor == 4) {
1.64 markus 460: /* We speak 1.3, too. */
461: enable_compat13();
1.81 markus 462: minor1 = 3;
1.64 markus 463: if (options.forward_agent) {
1.138 itojun 464: logit("Agent forwarding disabled for protocol 1.3");
1.64 markus 465: options.forward_agent = 0;
466: }
467: }
468: break;
469: case 2:
470: if (options.protocol & SSH_PROTO_2) {
471: enable_compat20();
472: break;
1.38 markus 473: }
1.64 markus 474: /* FALLTHROUGH */
1.68 markus 475: default:
1.64 markus 476: mismatch = 1;
477: break;
1.38 markus 478: }
1.64 markus 479: if (mismatch)
1.38 markus 480: fatal("Protocol major versions differ: %d vs. %d",
1.64 markus 481: (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
482: remote_major);
1.38 markus 483: /* Send our own protocol version identification. */
484: snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
1.64 markus 485: compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
1.81 markus 486: compat20 ? PROTOCOL_MINOR_2 : minor1,
1.59 markus 487: SSH_VERSION);
1.146 deraadt 488: if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf))
1.38 markus 489: fatal("write: %.100s", strerror(errno));
1.59 markus 490: client_version_string = xstrdup(buf);
491: chop(client_version_string);
492: chop(server_version_string);
493: debug("Local version string %.100s", client_version_string);
1.1 deraadt 494: }
495:
1.96 markus 496: /* defaults to 'no' */
1.109 itojun 497: static int
1.112 markus 498: confirm(const char *prompt)
1.1 deraadt 499: {
1.119 markus 500: const char *msg, *again = "Please type 'yes' or 'no': ";
501: char *p;
502: int ret = -1;
1.96 markus 503:
504: if (options.batch_mode)
505: return 0;
1.119 markus 506: for (msg = prompt;;msg = again) {
507: p = read_passphrase(msg, RP_ECHO);
508: if (p == NULL ||
509: (p[0] == '\0') || (p[0] == '\n') ||
510: strncasecmp(p, "no", 2) == 0)
511: ret = 0;
1.127 markus 512: if (p && strncasecmp(p, "yes", 3) == 0)
1.119 markus 513: ret = 1;
514: if (p)
515: xfree(p);
516: if (ret != -1)
517: return ret;
1.1 deraadt 518: }
519: }
520:
1.39 deraadt 521: /*
1.108 markus 522: * check whether the supplied host key is valid, return -1 if the key
523: * is not valid. the user_hostfile will not be updated if 'readonly' is true.
1.39 deraadt 524: */
1.109 itojun 525: static int
1.70 markus 526: check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key,
1.108 markus 527: int readonly, const char *user_hostfile, const char *system_hostfile)
1.1 deraadt 528: {
1.58 markus 529: Key *file_key;
1.152 jakob 530: const char *type = key_type(host_key);
1.46 markus 531: char *ip = NULL;
1.100 markus 532: char hostline[1000], *hostp, *fp;
1.38 markus 533: HostStatus host_status;
534: HostStatus ip_status;
1.161 djm 535: int r, local = 0, host_ip_differ = 0;
1.49 markus 536: char ntop[NI_MAXHOST];
1.119 markus 537: char msg[1024];
1.145 jakob 538: int len, host_line, ip_line;
1.85 markus 539: const char *host_file = NULL, *ip_file = NULL;
1.49 markus 540:
541: /*
542: * Force accepting of the host key for loopback/localhost. The
543: * problem is that if the home directory is NFS-mounted to multiple
544: * machines, localhost will refer to a different machine in each of
545: * them, and the user will get bogus HOST_CHANGED warnings. This
546: * essentially disables host authentication for localhost; however,
547: * this is probably not a real problem.
548: */
1.70 markus 549: /** hostaddr == 0! */
1.49 markus 550: switch (hostaddr->sa_family) {
551: case AF_INET:
1.108 markus 552: local = (ntohl(((struct sockaddr_in *)hostaddr)->
553: sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
1.49 markus 554: break;
555: case AF_INET6:
1.108 markus 556: local = IN6_IS_ADDR_LOOPBACK(
557: &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
1.49 markus 558: break;
559: default:
560: local = 0;
561: break;
562: }
1.111 markus 563: if (options.no_host_authentication_for_localhost == 1 && local &&
564: options.host_key_alias == NULL) {
1.88 markus 565: debug("Forcing accepting of host key for "
566: "loopback/localhost.");
1.108 markus 567: return 0;
1.49 markus 568: }
1.42 markus 569:
570: /*
1.88 markus 571: * We don't have the remote ip-address for connections
572: * using a proxy command
1.42 markus 573: */
1.84 markus 574: if (options.proxy_command == NULL) {
575: if (getnameinfo(hostaddr, hostaddr->sa_len, ntop, sizeof(ntop),
1.86 markus 576: NULL, 0, NI_NUMERICHOST) != 0)
1.84 markus 577: fatal("check_host_key: getnameinfo failed");
578: ip = xstrdup(ntop);
579: } else {
580: ip = xstrdup("<no hostip for proxy command>");
1.86 markus 581: }
1.88 markus 582: /*
583: * Turn off check_host_ip if the connection is to localhost, via proxy
584: * command or if we don't have a hostname to compare with
585: */
586: if (options.check_host_ip &&
587: (local || strcmp(host, ip) == 0 || options.proxy_command != NULL))
588: options.check_host_ip = 0;
1.86 markus 589:
590: /*
591: * Allow the user to record the key under a different name. This is
592: * useful for ssh tunneling over forwarded connections or if you run
593: * multiple sshd's on different ports on the same machine.
594: */
595: if (options.host_key_alias != NULL) {
596: host = options.host_key_alias;
597: debug("using hostkeyalias: %s", host);
1.84 markus 598: }
1.38 markus 599:
1.46 markus 600: /*
601: * Store the host key from the known host file in here so that we can
602: * compare it with the key for the IP address.
603: */
1.58 markus 604: file_key = key_new(host_key->type);
1.38 markus 605:
1.40 markus 606: /*
607: * Check if the host key is present in the user\'s list of known
608: * hosts or in the systemwide list.
609: */
1.85 markus 610: host_file = user_hostfile;
1.108 markus 611: host_status = check_host_in_hostfile(host_file, host, host_key,
1.118 deraadt 612: file_key, &host_line);
1.85 markus 613: if (host_status == HOST_NEW) {
614: host_file = system_hostfile;
1.108 markus 615: host_status = check_host_in_hostfile(host_file, host, host_key,
616: file_key, &host_line);
1.85 markus 617: }
1.40 markus 618: /*
619: * Also perform check for the ip address, skip the check if we are
620: * localhost or the hostname was an ip address to begin with
621: */
1.88 markus 622: if (options.check_host_ip) {
1.58 markus 623: Key *ip_key = key_new(host_key->type);
1.38 markus 624:
1.85 markus 625: ip_file = user_hostfile;
1.108 markus 626: ip_status = check_host_in_hostfile(ip_file, ip, host_key,
627: ip_key, &ip_line);
1.85 markus 628: if (ip_status == HOST_NEW) {
629: ip_file = system_hostfile;
1.108 markus 630: ip_status = check_host_in_hostfile(ip_file, ip,
631: host_key, ip_key, &ip_line);
1.85 markus 632: }
1.38 markus 633: if (host_status == HOST_CHANGED &&
1.58 markus 634: (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
1.38 markus 635: host_ip_differ = 1;
636:
1.58 markus 637: key_free(ip_key);
1.38 markus 638: } else
639: ip_status = host_status;
640:
1.58 markus 641: key_free(file_key);
1.38 markus 642:
643: switch (host_status) {
644: case HOST_OK:
645: /* The host is known and the key matches. */
1.72 markus 646: debug("Host '%.200s' is known and matches the %s host key.",
647: host, type);
1.85 markus 648: debug("Found key in %s:%d", host_file, host_line);
1.88 markus 649: if (options.check_host_ip && ip_status == HOST_NEW) {
1.108 markus 650: if (readonly)
1.138 itojun 651: logit("%s host key for IP address "
1.108 markus 652: "'%.128s' not in list of known hosts.",
653: type, ip);
654: else if (!add_host_to_hostfile(user_hostfile, ip,
1.160 djm 655: host_key, options.hash_known_hosts))
1.138 itojun 656: logit("Failed to add the %s host key for IP "
1.108 markus 657: "address '%.128s' to the list of known "
658: "hosts (%.30s).", type, ip, user_hostfile);
1.88 markus 659: else
1.138 itojun 660: logit("Warning: Permanently added the %s host "
1.108 markus 661: "key for IP address '%.128s' to the list "
662: "of known hosts.", type, ip);
1.38 markus 663: }
664: break;
665: case HOST_NEW:
1.108 markus 666: if (readonly)
667: goto fail;
1.38 markus 668: /* The host is new. */
669: if (options.strict_host_key_checking == 1) {
1.108 markus 670: /*
671: * User has requested strict host key checking. We
672: * will not add the host key automatically. The only
673: * alternative left is to abort.
674: */
675: error("No %s host key is known for %.200s and you "
676: "have requested strict checking.", type, host);
677: goto fail;
1.38 markus 678: } else if (options.strict_host_key_checking == 2) {
1.145 jakob 679: char msg1[1024], msg2[1024];
680:
681: if (show_other_keys(host, host_key))
682: snprintf(msg1, sizeof(msg1),
683: "\nbut keys of different type are already"
684: " known for this host.");
685: else
686: snprintf(msg1, sizeof(msg1), ".");
1.38 markus 687: /* The default */
1.100 markus 688: fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1.145 jakob 689: msg2[0] = '\0';
690: if (options.verify_host_key_dns) {
1.153 jakob 691: if (matching_host_key_dns)
1.145 jakob 692: snprintf(msg2, sizeof(msg2),
693: "Matching host key fingerprint"
694: " found in DNS.\n");
695: else
696: snprintf(msg2, sizeof(msg2),
697: "No matching host key fingerprint"
698: " found in DNS.\n");
699: }
1.119 markus 700: snprintf(msg, sizeof(msg),
1.108 markus 701: "The authenticity of host '%.200s (%s)' can't be "
1.132 markus 702: "established%s\n"
1.145 jakob 703: "%s key fingerprint is %s.\n%s"
1.108 markus 704: "Are you sure you want to continue connecting "
1.132 markus 705: "(yes/no)? ",
1.145 jakob 706: host, ip, msg1, type, fp, msg2);
1.100 markus 707: xfree(fp);
1.119 markus 708: if (!confirm(msg))
1.108 markus 709: goto fail;
1.38 markus 710: }
1.161 djm 711: /*
712: * If not in strict mode, add the key automatically to the
713: * local known_hosts file.
714: */
1.88 markus 715: if (options.check_host_ip && ip_status == HOST_NEW) {
1.161 djm 716: snprintf(hostline, sizeof(hostline), "%s,%s",
717: host, ip);
1.38 markus 718: hostp = hostline;
1.161 djm 719: if (options.hash_known_hosts) {
720: /* Add hash of host and IP separately */
721: r = add_host_to_hostfile(user_hostfile, host,
722: host_key, options.hash_known_hosts) &&
723: add_host_to_hostfile(user_hostfile, ip,
724: host_key, options.hash_known_hosts);
725: } else {
726: /* Add unhashed "host,ip" */
727: r = add_host_to_hostfile(user_hostfile,
728: hostline, host_key,
729: options.hash_known_hosts);
730: }
731: } else {
732: r = add_host_to_hostfile(user_hostfile, host, host_key,
733: options.hash_known_hosts);
1.38 markus 734: hostp = host;
1.161 djm 735: }
1.38 markus 736:
1.161 djm 737: if (!r)
1.138 itojun 738: logit("Failed to add the host to the list of known "
1.108 markus 739: "hosts (%.500s).", user_hostfile);
1.38 markus 740: else
1.138 itojun 741: logit("Warning: Permanently added '%.200s' (%s) to the "
1.108 markus 742: "list of known hosts.", hostp, type);
1.38 markus 743: break;
744: case HOST_CHANGED:
745: if (options.check_host_ip && host_ip_differ) {
1.158 avsm 746: char *key_msg;
1.38 markus 747: if (ip_status == HOST_NEW)
1.158 avsm 748: key_msg = "is unknown";
1.38 markus 749: else if (ip_status == HOST_OK)
1.158 avsm 750: key_msg = "is unchanged";
1.38 markus 751: else
1.158 avsm 752: key_msg = "has a different value";
1.38 markus 753: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
754: error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
755: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1.72 markus 756: error("The %s host key for %s has changed,", type, host);
1.38 markus 757: error("and the key for the according IP address %s", ip);
1.158 avsm 758: error("%s. This could either mean that", key_msg);
1.38 markus 759: error("DNS SPOOFING is happening or the IP address for the host");
1.85 markus 760: error("and its host key have changed at the same time.");
1.88 markus 761: if (ip_status != HOST_NEW)
1.85 markus 762: error("Offending key for IP in %s:%d", ip_file, ip_line);
1.38 markus 763: }
764: /* The host key has changed. */
1.150 jakob 765: warn_changed_key(host_key);
1.38 markus 766: error("Add correct host key in %.100s to get rid of this message.",
1.87 markus 767: user_hostfile);
1.85 markus 768: error("Offending key in %s:%d", host_file, host_line);
1.38 markus 769:
1.40 markus 770: /*
771: * If strict host key checking is in use, the user will have
772: * to edit the key manually and we can only abort.
773: */
1.108 markus 774: if (options.strict_host_key_checking) {
775: error("%s host key for %.200s has changed and you have "
776: "requested strict checking.", type, host);
777: goto fail;
778: }
1.38 markus 779:
1.40 markus 780: /*
781: * If strict host key checking has not been requested, allow
1.144 djm 782: * the connection but without MITM-able authentication or
1.40 markus 783: * agent forwarding.
784: */
1.38 markus 785: if (options.password_authentication) {
1.108 markus 786: error("Password authentication is disabled to avoid "
787: "man-in-the-middle attacks.");
1.38 markus 788: options.password_authentication = 0;
1.144 djm 789: }
790: if (options.kbd_interactive_authentication) {
791: error("Keyboard-interactive authentication is disabled"
792: " to avoid man-in-the-middle attacks.");
793: options.kbd_interactive_authentication = 0;
794: options.challenge_response_authentication = 0;
795: }
796: if (options.challenge_response_authentication) {
797: error("Challenge/response authentication is disabled"
798: " to avoid man-in-the-middle attacks.");
799: options.challenge_response_authentication = 0;
1.38 markus 800: }
801: if (options.forward_agent) {
1.108 markus 802: error("Agent forwarding is disabled to avoid "
803: "man-in-the-middle attacks.");
1.38 markus 804: options.forward_agent = 0;
1.83 markus 805: }
806: if (options.forward_x11) {
1.108 markus 807: error("X11 forwarding is disabled to avoid "
808: "man-in-the-middle attacks.");
1.83 markus 809: options.forward_x11 = 0;
810: }
1.108 markus 811: if (options.num_local_forwards > 0 ||
812: options.num_remote_forwards > 0) {
813: error("Port forwarding is disabled to avoid "
814: "man-in-the-middle attacks.");
815: options.num_local_forwards =
1.118 deraadt 816: options.num_remote_forwards = 0;
1.38 markus 817: }
1.40 markus 818: /*
819: * XXX Should permit the user to change to use the new id.
820: * This could be done by converting the host key to an
821: * identifying sentence, tell that the host identifies itself
822: * by that sentence, and ask the user if he/she whishes to
823: * accept the authentication.
824: */
1.38 markus 825: break;
1.132 markus 826: case HOST_FOUND:
827: fatal("internal error");
828: break;
1.88 markus 829: }
830:
831: if (options.check_host_ip && host_status != HOST_CHANGED &&
832: ip_status == HOST_CHANGED) {
1.119 markus 833: snprintf(msg, sizeof(msg),
834: "Warning: the %s host key for '%.200s' "
835: "differs from the key for the IP address '%.128s'"
836: "\nOffending key for IP in %s:%d",
837: type, host, ip, ip_file, ip_line);
838: if (host_status == HOST_OK) {
839: len = strlen(msg);
840: snprintf(msg + len, sizeof(msg) - len,
841: "\nMatching host key in %s:%d",
1.125 deraadt 842: host_file, host_line);
1.119 markus 843: }
1.88 markus 844: if (options.strict_host_key_checking == 1) {
1.143 djm 845: logit("%s", msg);
1.108 markus 846: error("Exiting, you have requested strict checking.");
847: goto fail;
1.88 markus 848: } else if (options.strict_host_key_checking == 2) {
1.119 markus 849: strlcat(msg, "\nAre you sure you want "
850: "to continue connecting (yes/no)? ", sizeof(msg));
851: if (!confirm(msg))
1.108 markus 852: goto fail;
1.119 markus 853: } else {
1.143 djm 854: logit("%s", msg);
1.88 markus 855: }
1.38 markus 856: }
1.82 provos 857:
858: xfree(ip);
1.108 markus 859: return 0;
860:
861: fail:
862: xfree(ip);
863: return -1;
864: }
865:
1.140 jakob 866: /* returns 0 if key verifies or -1 if key does NOT verify */
1.108 markus 867: int
868: verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
869: {
870: struct stat st;
1.153 jakob 871: int flags = 0;
1.140 jakob 872:
1.153 jakob 873: if (options.verify_host_key_dns &&
874: verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
875:
876: if (flags & DNS_VERIFY_FOUND) {
877:
878: if (options.verify_host_key_dns == 1 &&
879: flags & DNS_VERIFY_MATCH &&
880: flags & DNS_VERIFY_SECURE)
881: return 0;
882:
883: if (flags & DNS_VERIFY_MATCH) {
884: matching_host_key_dns = 1;
885: } else {
886: warn_changed_key(host_key);
887: error("Update the SSHFP RR in DNS with the new "
888: "host key to get rid of this message.");
889: }
1.140 jakob 890: }
891: }
1.108 markus 892:
893: /* return ok if the key can be found in an old keyfile */
894: if (stat(options.system_hostfile2, &st) == 0 ||
895: stat(options.user_hostfile2, &st) == 0) {
896: if (check_host_key(host, hostaddr, host_key, /*readonly*/ 1,
897: options.user_hostfile2, options.system_hostfile2) == 0)
898: return 0;
899: }
900: return check_host_key(host, hostaddr, host_key, /*readonly*/ 0,
901: options.user_hostfile, options.system_hostfile);
1.51 markus 902: }
1.70 markus 903:
1.51 markus 904: /*
905: * Starts a dialog with the server, and authenticates the current user on the
906: * server. This does not need any extra privileges. The basic connection
907: * to the server must already have been established before this is called.
908: * If login fails, this function prints an error and never returns.
909: * This function does not require super-user privileges.
910: */
911: void
1.120 markus 912: ssh_login(Sensitive *sensitive, const char *orighost,
1.103 markus 913: struct sockaddr *hostaddr, struct passwd *pw)
1.51 markus 914: {
915: char *host, *cp;
1.70 markus 916: char *server_user, *local_user;
917:
918: local_user = xstrdup(pw->pw_name);
919: server_user = options.user ? options.user : local_user;
1.51 markus 920:
921: /* Convert the user-supplied hostname into all lowercase. */
922: host = xstrdup(orighost);
923: for (cp = host; *cp; cp++)
924: if (isupper(*cp))
925: *cp = tolower(*cp);
926:
927: /* Exchange protocol version identification strings with the server. */
928: ssh_exchange_identification();
929:
930: /* Put the connection into non-blocking mode. */
931: packet_set_nonblocking();
932:
933: /* key exchange */
934: /* authenticate user */
1.59 markus 935: if (compat20) {
936: ssh_kex2(host, hostaddr);
1.120 markus 937: ssh_userauth2(local_user, server_user, host, sensitive);
1.59 markus 938: } else {
939: ssh_kex(host, hostaddr);
1.120 markus 940: ssh_userauth1(local_user, server_user, host, sensitive);
1.59 markus 941: }
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);
955: padded = xmalloc(size);
956: memset(padded, 0, size);
957: strlcpy(padded, password, size);
958: packet_put_string(padded, size);
959: memset(padded, 0, size);
960: xfree(padded);
1.132 markus 961: }
962:
963: static int
964: show_key_from_file(const char *file, const char *host, int keytype)
965: {
966: Key *found;
967: char *fp;
968: int line, ret;
969:
970: found = key_new(keytype);
971: if ((ret = lookup_key_in_hostfile_by_type(file, host,
972: keytype, found, &line))) {
973: fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
1.138 itojun 974: logit("WARNING: %s key found for host %s\n"
1.133 markus 975: "in %s:%d\n"
1.132 markus 976: "%s key fingerprint %s.",
977: key_type(found), host, file, line,
978: key_type(found), fp);
979: xfree(fp);
980: }
981: key_free(found);
982: return (ret);
983: }
984:
985: /* print all known host keys for a given host, but skip keys of given type */
986: static int
987: show_other_keys(const char *host, Key *key)
988: {
989: int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1};
990: int i, found = 0;
991:
992: for (i = 0; type[i] != -1; i++) {
993: if (type[i] == key->type)
994: continue;
995: if (type[i] != KEY_RSA1 &&
996: show_key_from_file(options.user_hostfile2, host, type[i])) {
997: found = 1;
998: continue;
999: }
1000: if (type[i] != KEY_RSA1 &&
1001: show_key_from_file(options.system_hostfile2, host, type[i])) {
1002: found = 1;
1003: continue;
1004: }
1005: if (show_key_from_file(options.user_hostfile, host, type[i])) {
1006: found = 1;
1007: continue;
1008: }
1009: if (show_key_from_file(options.system_hostfile, host, type[i])) {
1010: found = 1;
1011: continue;
1012: }
1013: debug2("no key of type %d for host %s", type[i], host);
1014: }
1015: return (found);
1.150 jakob 1016: }
1017:
1018: static void
1019: warn_changed_key(Key *host_key)
1020: {
1021: char *fp;
1.151 jakob 1022: const char *type = key_type(host_key);
1.150 jakob 1023:
1024: fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1025:
1026: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1027: error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1028: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1029: error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1030: error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1031: error("It is also possible that the %s host key has just been changed.", type);
1032: error("The fingerprint for the %s key sent by the remote host is\n%s.",
1033: type, fp);
1034: error("Please contact your system administrator.");
1035:
1036: xfree(fp);
1.1 deraadt 1037: }
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