Annotation of src/usr.bin/ssh/sshconnect.c, Revision 1.170
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"
1.170 ! djm 16: RCSID("$OpenBSD: sshconnect.c,v 1.169 2005/10/15 15:28:12 stevesk 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"
1.140 jakob 34: #include "dns.h"
35:
1.70 markus 36: char *client_version_string = NULL;
37: char *server_version_string = NULL;
1.59 markus 38:
1.169 stevesk 39: static int matching_host_key_dns = 0;
1.145 jakob 40:
1.124 markus 41: /* import */
1.43 markus 42: extern Options options;
1.50 markus 43: extern char *__progname;
1.124 markus 44: extern uid_t original_real_uid;
45: extern uid_t original_effective_uid;
1.135 djm 46: extern pid_t proxy_command_pid;
1.91 markus 47:
1.132 markus 48: static int show_other_keys(const char *, Key *);
1.150 jakob 49: static void warn_changed_key(Key *);
1.132 markus 50:
1.39 deraadt 51: /*
52: * Connect to the given ssh server using a proxy command.
53: */
1.109 itojun 54: static int
1.124 markus 55: ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
1.1 deraadt 56: {
1.164 djm 57: char *command_string, *tmp;
1.38 markus 58: int pin[2], pout[2];
1.69 deraadt 59: pid_t pid;
1.49 markus 60: char strport[NI_MAXSERV];
1.164 djm 61: size_t len;
1.38 markus 62:
63: /* Convert the port number into a string. */
1.49 markus 64: snprintf(strport, sizeof strport, "%hu", port);
1.38 markus 65:
1.135 djm 66: /*
67: * Build the final command string in the buffer by making the
68: * appropriate substitutions to the given proxy command.
69: *
1.154 djm 70: * Use "exec" to avoid "sh -c" processes on some platforms
1.135 djm 71: * (e.g. Solaris)
72: */
1.164 djm 73: len = strlen(proxy_command) + 6;
74: tmp = xmalloc(len);
75: strlcpy(tmp, "exec ", len);
76: strlcat(tmp, proxy_command, len);
77: command_string = percent_expand(tmp, "h", host,
78: "p", strport, (char *)NULL);
79: xfree(tmp);
1.38 markus 80:
81: /* Create pipes for communicating with the proxy. */
82: if (pipe(pin) < 0 || pipe(pout) < 0)
83: fatal("Could not create pipes to communicate with the proxy: %.100s",
1.118 deraadt 84: strerror(errno));
1.38 markus 85:
86: debug("Executing proxy command: %.500s", command_string);
87:
88: /* Fork and execute the proxy command. */
89: if ((pid = fork()) == 0) {
90: char *argv[10];
91:
92: /* Child. Permanently give up superuser privileges. */
1.124 markus 93: seteuid(original_real_uid);
94: setuid(original_real_uid);
1.38 markus 95:
96: /* Redirect stdin and stdout. */
97: close(pin[1]);
98: if (pin[0] != 0) {
99: if (dup2(pin[0], 0) < 0)
100: perror("dup2 stdin");
101: close(pin[0]);
102: }
103: close(pout[0]);
104: if (dup2(pout[1], 1) < 0)
105: perror("dup2 stdout");
106: /* Cannot be 1 because pin allocated two descriptors. */
107: close(pout[1]);
108:
109: /* Stderr is left as it is so that error messages get
110: printed on the user's terminal. */
1.89 markus 111: argv[0] = _PATH_BSHELL;
1.38 markus 112: argv[1] = "-c";
113: argv[2] = command_string;
114: argv[3] = NULL;
115:
116: /* Execute the proxy command. Note that we gave up any
117: extra privileges above. */
1.89 markus 118: execv(argv[0], argv);
119: perror(argv[0]);
1.38 markus 120: exit(1);
121: }
122: /* Parent. */
123: if (pid < 0)
124: fatal("fork failed: %.100s", strerror(errno));
1.135 djm 125: else
126: proxy_command_pid = pid; /* save pid to clean up later */
1.38 markus 127:
128: /* Close child side of the descriptors. */
129: close(pin[0]);
130: close(pout[1]);
131:
132: /* Free the command name. */
1.164 djm 133: xfree(command_string);
1.38 markus 134:
135: /* Set the connection file descriptors. */
136: packet_set_connection(pout[0], pin[1]);
1.1 deraadt 137:
1.110 markus 138: /* Indicate OK return */
139: return 0;
1.1 deraadt 140: }
141:
1.39 deraadt 142: /*
143: * Creates a (possibly privileged) socket for use as the ssh connection.
144: */
1.109 itojun 145: static int
1.139 markus 146: ssh_create_socket(int privileged, struct addrinfo *ai)
1.1 deraadt 147: {
1.105 markus 148: int sock, gaierr;
149: struct addrinfo hints, *res;
1.1 deraadt 150:
1.40 markus 151: /*
152: * If we are running as root and want to connect to a privileged
153: * port, bind our own socket to a privileged port.
154: */
1.38 markus 155: if (privileged) {
156: int p = IPPORT_RESERVED - 1;
1.124 markus 157: PRIV_START;
1.139 markus 158: sock = rresvport_af(&p, ai->ai_family);
1.124 markus 159: PRIV_END;
1.38 markus 160: if (sock < 0)
1.139 markus 161: error("rresvport: af=%d %.100s", ai->ai_family,
162: strerror(errno));
1.55 markus 163: else
164: debug("Allocated local port %d.", p);
1.105 markus 165: return sock;
166: }
1.139 markus 167: sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
1.105 markus 168: if (sock < 0)
169: error("socket: %.100s", strerror(errno));
170:
171: /* Bind the socket to an alternative local IP address */
172: if (options.bind_address == NULL)
173: return sock;
174:
175: memset(&hints, 0, sizeof(hints));
1.139 markus 176: hints.ai_family = ai->ai_family;
177: hints.ai_socktype = ai->ai_socktype;
178: hints.ai_protocol = ai->ai_protocol;
1.105 markus 179: hints.ai_flags = AI_PASSIVE;
180: gaierr = getaddrinfo(options.bind_address, "0", &hints, &res);
181: if (gaierr) {
182: error("getaddrinfo: %s: %s", options.bind_address,
183: gai_strerror(gaierr));
184: close(sock);
185: return -1;
186: }
187: if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
188: error("bind: %s: %s", options.bind_address, strerror(errno));
189: close(sock);
190: freeaddrinfo(res);
191: return -1;
1.38 markus 192: }
1.105 markus 193: freeaddrinfo(res);
1.38 markus 194: return sock;
1.1 deraadt 195: }
196:
1.141 djm 197: static int
198: timeout_connect(int sockfd, const struct sockaddr *serv_addr,
199: socklen_t addrlen, int timeout)
200: {
201: fd_set *fdset;
202: struct timeval tv;
203: socklen_t optlen;
1.142 djm 204: int fdsetsz, optval, rc, result = -1;
1.141 djm 205:
206: if (timeout <= 0)
207: return (connect(sockfd, serv_addr, addrlen));
208:
1.156 djm 209: set_nonblock(sockfd);
1.141 djm 210: rc = connect(sockfd, serv_addr, addrlen);
1.156 djm 211: if (rc == 0) {
212: unset_nonblock(sockfd);
1.141 djm 213: return (0);
1.156 djm 214: }
1.141 djm 215: if (errno != EINPROGRESS)
216: return (-1);
217:
218: fdsetsz = howmany(sockfd + 1, NFDBITS) * sizeof(fd_mask);
219: fdset = (fd_set *)xmalloc(fdsetsz);
220:
1.147 markus 221: memset(fdset, 0, fdsetsz);
1.141 djm 222: FD_SET(sockfd, fdset);
223: tv.tv_sec = timeout;
224: tv.tv_usec = 0;
225:
1.162 deraadt 226: for (;;) {
1.141 djm 227: rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
228: if (rc != -1 || errno != EINTR)
229: break;
230: }
231:
1.162 deraadt 232: switch (rc) {
1.141 djm 233: case 0:
234: /* Timed out */
235: errno = ETIMEDOUT;
1.142 djm 236: break;
1.141 djm 237: case -1:
238: /* Select error */
1.154 djm 239: debug("select: %s", strerror(errno));
1.142 djm 240: break;
1.141 djm 241: case 1:
242: /* Completed or failed */
243: optval = 0;
244: optlen = sizeof(optval);
1.154 djm 245: if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
1.148 markus 246: &optlen) == -1) {
1.154 djm 247: debug("getsockopt: %s", strerror(errno));
1.142 djm 248: break;
1.148 markus 249: }
1.141 djm 250: if (optval != 0) {
251: errno = optval;
1.142 djm 252: break;
1.141 djm 253: }
1.142 djm 254: result = 0;
1.156 djm 255: unset_nonblock(sockfd);
1.141 djm 256: break;
257: default:
258: /* Should not occur */
259: fatal("Bogus return (%d) from select()", rc);
260: }
261:
1.142 djm 262: xfree(fdset);
263: return (result);
1.141 djm 264: }
265:
1.39 deraadt 266: /*
1.49 markus 267: * Opens a TCP/IP connection to the remote server on the given host.
268: * The address of the remote host will be returned in hostaddr.
1.124 markus 269: * If port is 0, the default port will be used. If needpriv is true,
1.39 deraadt 270: * a privileged port will be allocated to make the connection.
1.124 markus 271: * This requires super-user privileges if needpriv is true.
1.39 deraadt 272: * Connection_attempts specifies the maximum number of tries (one per
273: * second). If proxy_command is non-NULL, it specifies the command (with %h
274: * and %p substituted for host and port, respectively) to use to contact
275: * the daemon.
276: */
1.38 markus 277: int
1.49 markus 278: ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
1.115 markus 279: u_short port, int family, int connection_attempts,
1.124 markus 280: int needpriv, const char *proxy_command)
1.1 deraadt 281: {
1.90 markus 282: int gaierr;
283: int on = 1;
1.49 markus 284: int sock = -1, attempt;
1.90 markus 285: char ntop[NI_MAXHOST], strport[NI_MAXSERV];
1.49 markus 286: struct addrinfo hints, *ai, *aitop;
1.38 markus 287:
1.136 markus 288: debug2("ssh_connect: needpriv %d", needpriv);
1.38 markus 289:
290: /* If a proxy command is given, connect using it. */
291: if (proxy_command != NULL)
1.124 markus 292: return ssh_proxy_connect(host, port, proxy_command);
1.38 markus 293:
294: /* No proxy command. */
295:
1.49 markus 296: memset(&hints, 0, sizeof(hints));
1.115 markus 297: hints.ai_family = family;
1.49 markus 298: hints.ai_socktype = SOCK_STREAM;
1.126 deraadt 299: snprintf(strport, sizeof strport, "%u", port);
1.49 markus 300: if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
1.50 markus 301: fatal("%s: %.100s: %s", __progname, host,
302: gai_strerror(gaierr));
1.38 markus 303:
1.46 markus 304: /*
305: * Try to connect several times. On some machines, the first time
306: * will sometimes fail. In general socket code appears to behave
307: * quite magically on many machines.
1.110 markus 308: */
309: for (attempt = 0; ;) {
1.38 markus 310: if (attempt > 0)
311: debug("Trying again...");
312:
1.49 markus 313: /* Loop through addresses for this host, and try each one in
1.68 markus 314: sequence until the connection succeeds. */
1.49 markus 315: for (ai = aitop; ai; ai = ai->ai_next) {
316: if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
317: continue;
318: if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
319: ntop, sizeof(ntop), strport, sizeof(strport),
320: NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
321: error("ssh_connect: getnameinfo failed");
322: continue;
323: }
324: debug("Connecting to %.200s [%.100s] port %s.",
325: host, ntop, strport);
326:
327: /* Create a socket for connecting. */
1.139 markus 328: sock = ssh_create_socket(needpriv, ai);
1.49 markus 329: if (sock < 0)
1.110 markus 330: /* Any error is already output */
1.49 markus 331: continue;
332:
1.141 djm 333: if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
334: options.connection_timeout) >= 0) {
1.49 markus 335: /* Successful connection. */
1.102 markus 336: memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
1.38 markus 337: break;
1.49 markus 338: } else {
1.131 itojun 339: debug("connect to address %s port %s: %s",
340: ntop, strport, strerror(errno));
1.40 markus 341: /*
342: * Close the failed socket; there appear to
343: * be some problems when reusing a socket for
344: * which connect() has already returned an
345: * error.
346: */
1.38 markus 347: close(sock);
348: }
349: }
1.49 markus 350: if (ai)
351: break; /* Successful connection. */
1.1 deraadt 352:
1.110 markus 353: attempt++;
354: if (attempt >= connection_attempts)
355: break;
1.38 markus 356: /* Sleep a moment before retrying. */
357: sleep(1);
358: }
1.49 markus 359:
360: freeaddrinfo(aitop);
361:
1.38 markus 362: /* Return failure if we didn't get a successful connection. */
1.130 itojun 363: if (attempt >= connection_attempts) {
1.159 markus 364: error("ssh: connect to host %s port %s: %s",
1.130 itojun 365: host, strport, strerror(errno));
1.159 markus 366: return (-1);
1.130 itojun 367: }
1.38 markus 368:
369: debug("Connection established.");
1.90 markus 370:
1.155 markus 371: /* Set SO_KEEPALIVE if requested. */
372: if (options.tcp_keep_alive &&
1.90 markus 373: setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
374: sizeof(on)) < 0)
375: error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1.38 markus 376:
377: /* Set the connection. */
378: packet_set_connection(sock, sock);
1.1 deraadt 379:
1.110 markus 380: return 0;
1.59 markus 381: }
382:
1.43 markus 383: /*
1.39 deraadt 384: * Waits for the server identification string, and sends our own
385: * identification string.
386: */
1.109 itojun 387: static void
1.95 itojun 388: ssh_exchange_identification(void)
1.1 deraadt 389: {
1.38 markus 390: char buf[256], remote_version[256]; /* must be same size! */
1.165 djm 391: int remote_major, remote_minor, mismatch;
1.38 markus 392: int connection_in = packet_get_connection_in();
393: int connection_out = packet_get_connection_out();
1.93 stevesk 394: int minor1 = PROTOCOL_MINOR_1;
1.165 djm 395: u_int i;
1.38 markus 396:
1.163 avsm 397: /* Read other side's version identification. */
1.75 markus 398: for (;;) {
399: for (i = 0; i < sizeof(buf) - 1; i++) {
1.163 avsm 400: size_t len = atomicio(read, connection_in, &buf[i], 1);
401:
1.167 djm 402: if (len != 1 && errno == EPIPE)
1.163 avsm 403: fatal("ssh_exchange_identification: Connection closed by remote host");
404: else if (len != 1)
1.75 markus 405: fatal("ssh_exchange_identification: read: %.100s", strerror(errno));
406: if (buf[i] == '\r') {
407: buf[i] = '\n';
408: buf[i + 1] = 0;
409: continue; /**XXX wait for \n */
410: }
411: if (buf[i] == '\n') {
412: buf[i + 1] = 0;
413: break;
414: }
1.38 markus 415: }
1.75 markus 416: buf[sizeof(buf) - 1] = 0;
1.76 markus 417: if (strncmp(buf, "SSH-", 4) == 0)
1.38 markus 418: break;
1.75 markus 419: debug("ssh_exchange_identification: %s", buf);
1.38 markus 420: }
1.59 markus 421: server_version_string = xstrdup(buf);
1.38 markus 422:
1.40 markus 423: /*
424: * Check that the versions match. In future this might accept
425: * several versions and set appropriate flags to handle them.
426: */
1.59 markus 427: if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
428: &remote_major, &remote_minor, remote_version) != 3)
1.38 markus 429: fatal("Bad remote protocol version identification: '%.100s'", buf);
430: debug("Remote protocol version %d.%d, remote software version %.100s",
1.118 deraadt 431: remote_major, remote_minor, remote_version);
1.38 markus 432:
1.59 markus 433: compat_datafellows(remote_version);
1.64 markus 434: mismatch = 0;
1.59 markus 435:
1.116 deraadt 436: switch (remote_major) {
1.64 markus 437: case 1:
438: if (remote_minor == 99 &&
439: (options.protocol & SSH_PROTO_2) &&
440: !(options.protocol & SSH_PROTO_1_PREFERRED)) {
441: enable_compat20();
442: break;
443: }
444: if (!(options.protocol & SSH_PROTO_1)) {
445: mismatch = 1;
446: break;
447: }
448: if (remote_minor < 3) {
449: fatal("Remote machine has too old SSH software version.");
1.81 markus 450: } else if (remote_minor == 3 || remote_minor == 4) {
1.64 markus 451: /* We speak 1.3, too. */
452: enable_compat13();
1.81 markus 453: minor1 = 3;
1.64 markus 454: if (options.forward_agent) {
1.138 itojun 455: logit("Agent forwarding disabled for protocol 1.3");
1.64 markus 456: options.forward_agent = 0;
457: }
458: }
459: break;
460: case 2:
461: if (options.protocol & SSH_PROTO_2) {
462: enable_compat20();
463: break;
1.38 markus 464: }
1.64 markus 465: /* FALLTHROUGH */
1.68 markus 466: default:
1.64 markus 467: mismatch = 1;
468: break;
1.38 markus 469: }
1.64 markus 470: if (mismatch)
1.38 markus 471: fatal("Protocol major versions differ: %d vs. %d",
1.64 markus 472: (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
473: remote_major);
1.38 markus 474: /* Send our own protocol version identification. */
475: snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
1.64 markus 476: compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
1.81 markus 477: compat20 ? PROTOCOL_MINOR_2 : minor1,
1.59 markus 478: SSH_VERSION);
1.146 deraadt 479: if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf))
1.38 markus 480: fatal("write: %.100s", strerror(errno));
1.59 markus 481: client_version_string = xstrdup(buf);
482: chop(client_version_string);
483: chop(server_version_string);
484: debug("Local version string %.100s", client_version_string);
1.1 deraadt 485: }
486:
1.96 markus 487: /* defaults to 'no' */
1.109 itojun 488: static int
1.112 markus 489: confirm(const char *prompt)
1.1 deraadt 490: {
1.119 markus 491: const char *msg, *again = "Please type 'yes' or 'no': ";
492: char *p;
493: int ret = -1;
1.96 markus 494:
495: if (options.batch_mode)
496: return 0;
1.119 markus 497: for (msg = prompt;;msg = again) {
498: p = read_passphrase(msg, RP_ECHO);
499: if (p == NULL ||
500: (p[0] == '\0') || (p[0] == '\n') ||
501: strncasecmp(p, "no", 2) == 0)
502: ret = 0;
1.127 markus 503: if (p && strncasecmp(p, "yes", 3) == 0)
1.119 markus 504: ret = 1;
505: if (p)
506: xfree(p);
507: if (ret != -1)
508: return ret;
1.1 deraadt 509: }
510: }
511:
1.39 deraadt 512: /*
1.108 markus 513: * check whether the supplied host key is valid, return -1 if the key
514: * is not valid. the user_hostfile will not be updated if 'readonly' is true.
1.39 deraadt 515: */
1.109 itojun 516: static int
1.70 markus 517: check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key,
1.108 markus 518: int readonly, const char *user_hostfile, const char *system_hostfile)
1.1 deraadt 519: {
1.58 markus 520: Key *file_key;
1.152 jakob 521: const char *type = key_type(host_key);
1.46 markus 522: char *ip = NULL;
1.100 markus 523: char hostline[1000], *hostp, *fp;
1.38 markus 524: HostStatus host_status;
525: HostStatus ip_status;
1.161 djm 526: int r, local = 0, host_ip_differ = 0;
1.49 markus 527: char ntop[NI_MAXHOST];
1.119 markus 528: char msg[1024];
1.145 jakob 529: int len, host_line, ip_line;
1.85 markus 530: const char *host_file = NULL, *ip_file = NULL;
1.49 markus 531:
532: /*
533: * Force accepting of the host key for loopback/localhost. The
534: * problem is that if the home directory is NFS-mounted to multiple
535: * machines, localhost will refer to a different machine in each of
536: * them, and the user will get bogus HOST_CHANGED warnings. This
537: * essentially disables host authentication for localhost; however,
538: * this is probably not a real problem.
539: */
1.70 markus 540: /** hostaddr == 0! */
1.49 markus 541: switch (hostaddr->sa_family) {
542: case AF_INET:
1.108 markus 543: local = (ntohl(((struct sockaddr_in *)hostaddr)->
1.168 djm 544: sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
1.49 markus 545: break;
546: case AF_INET6:
1.108 markus 547: local = IN6_IS_ADDR_LOOPBACK(
548: &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
1.49 markus 549: break;
550: default:
551: local = 0;
552: break;
553: }
1.111 markus 554: if (options.no_host_authentication_for_localhost == 1 && local &&
555: options.host_key_alias == NULL) {
1.88 markus 556: debug("Forcing accepting of host key for "
557: "loopback/localhost.");
1.108 markus 558: return 0;
1.49 markus 559: }
1.42 markus 560:
561: /*
1.88 markus 562: * We don't have the remote ip-address for connections
563: * using a proxy command
1.42 markus 564: */
1.84 markus 565: if (options.proxy_command == NULL) {
566: if (getnameinfo(hostaddr, hostaddr->sa_len, ntop, sizeof(ntop),
1.86 markus 567: NULL, 0, NI_NUMERICHOST) != 0)
1.84 markus 568: fatal("check_host_key: getnameinfo failed");
569: ip = xstrdup(ntop);
570: } else {
571: ip = xstrdup("<no hostip for proxy command>");
1.86 markus 572: }
1.88 markus 573: /*
574: * Turn off check_host_ip if the connection is to localhost, via proxy
575: * command or if we don't have a hostname to compare with
576: */
577: if (options.check_host_ip &&
578: (local || strcmp(host, ip) == 0 || options.proxy_command != NULL))
579: options.check_host_ip = 0;
1.86 markus 580:
581: /*
582: * Allow the user to record the key under a different name. This is
583: * useful for ssh tunneling over forwarded connections or if you run
584: * multiple sshd's on different ports on the same machine.
585: */
586: if (options.host_key_alias != NULL) {
587: host = options.host_key_alias;
588: debug("using hostkeyalias: %s", host);
1.84 markus 589: }
1.38 markus 590:
1.46 markus 591: /*
592: * Store the host key from the known host file in here so that we can
593: * compare it with the key for the IP address.
594: */
1.58 markus 595: file_key = key_new(host_key->type);
1.38 markus 596:
1.40 markus 597: /*
1.170 ! djm 598: * Check if the host key is present in the user's list of known
1.40 markus 599: * hosts or in the systemwide list.
600: */
1.85 markus 601: host_file = user_hostfile;
1.108 markus 602: host_status = check_host_in_hostfile(host_file, host, host_key,
1.118 deraadt 603: file_key, &host_line);
1.85 markus 604: if (host_status == HOST_NEW) {
605: host_file = system_hostfile;
1.108 markus 606: host_status = check_host_in_hostfile(host_file, host, host_key,
607: file_key, &host_line);
1.85 markus 608: }
1.40 markus 609: /*
610: * Also perform check for the ip address, skip the check if we are
611: * localhost or the hostname was an ip address to begin with
612: */
1.88 markus 613: if (options.check_host_ip) {
1.58 markus 614: Key *ip_key = key_new(host_key->type);
1.38 markus 615:
1.85 markus 616: ip_file = user_hostfile;
1.108 markus 617: ip_status = check_host_in_hostfile(ip_file, ip, host_key,
618: ip_key, &ip_line);
1.85 markus 619: if (ip_status == HOST_NEW) {
620: ip_file = system_hostfile;
1.108 markus 621: ip_status = check_host_in_hostfile(ip_file, ip,
622: host_key, ip_key, &ip_line);
1.85 markus 623: }
1.38 markus 624: if (host_status == HOST_CHANGED &&
1.58 markus 625: (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
1.38 markus 626: host_ip_differ = 1;
627:
1.58 markus 628: key_free(ip_key);
1.38 markus 629: } else
630: ip_status = host_status;
631:
1.58 markus 632: key_free(file_key);
1.38 markus 633:
634: switch (host_status) {
635: case HOST_OK:
636: /* The host is known and the key matches. */
1.72 markus 637: debug("Host '%.200s' is known and matches the %s host key.",
638: host, type);
1.85 markus 639: debug("Found key in %s:%d", host_file, host_line);
1.88 markus 640: if (options.check_host_ip && ip_status == HOST_NEW) {
1.108 markus 641: if (readonly)
1.138 itojun 642: logit("%s host key for IP address "
1.108 markus 643: "'%.128s' not in list of known hosts.",
644: type, ip);
645: else if (!add_host_to_hostfile(user_hostfile, ip,
1.160 djm 646: host_key, options.hash_known_hosts))
1.138 itojun 647: logit("Failed to add the %s host key for IP "
1.108 markus 648: "address '%.128s' to the list of known "
649: "hosts (%.30s).", type, ip, user_hostfile);
1.88 markus 650: else
1.138 itojun 651: logit("Warning: Permanently added the %s host "
1.108 markus 652: "key for IP address '%.128s' to the list "
653: "of known hosts.", type, ip);
1.38 markus 654: }
655: break;
656: case HOST_NEW:
1.108 markus 657: if (readonly)
658: goto fail;
1.38 markus 659: /* The host is new. */
660: if (options.strict_host_key_checking == 1) {
1.108 markus 661: /*
662: * User has requested strict host key checking. We
663: * will not add the host key automatically. The only
664: * alternative left is to abort.
665: */
666: error("No %s host key is known for %.200s and you "
667: "have requested strict checking.", type, host);
668: goto fail;
1.38 markus 669: } else if (options.strict_host_key_checking == 2) {
1.145 jakob 670: char msg1[1024], msg2[1024];
671:
672: if (show_other_keys(host, host_key))
673: snprintf(msg1, sizeof(msg1),
1.168 djm 674: "\nbut keys of different type are already"
675: " known for this host.");
1.145 jakob 676: else
677: snprintf(msg1, sizeof(msg1), ".");
1.38 markus 678: /* The default */
1.100 markus 679: fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1.145 jakob 680: msg2[0] = '\0';
681: if (options.verify_host_key_dns) {
1.153 jakob 682: if (matching_host_key_dns)
1.145 jakob 683: snprintf(msg2, sizeof(msg2),
684: "Matching host key fingerprint"
685: " found in DNS.\n");
686: else
687: snprintf(msg2, sizeof(msg2),
688: "No matching host key fingerprint"
689: " found in DNS.\n");
690: }
1.119 markus 691: snprintf(msg, sizeof(msg),
1.108 markus 692: "The authenticity of host '%.200s (%s)' can't be "
1.132 markus 693: "established%s\n"
1.145 jakob 694: "%s key fingerprint is %s.\n%s"
1.108 markus 695: "Are you sure you want to continue connecting "
1.132 markus 696: "(yes/no)? ",
1.145 jakob 697: host, ip, msg1, type, fp, msg2);
1.100 markus 698: xfree(fp);
1.119 markus 699: if (!confirm(msg))
1.108 markus 700: goto fail;
1.38 markus 701: }
1.161 djm 702: /*
703: * If not in strict mode, add the key automatically to the
704: * local known_hosts file.
705: */
1.88 markus 706: if (options.check_host_ip && ip_status == HOST_NEW) {
1.161 djm 707: snprintf(hostline, sizeof(hostline), "%s,%s",
708: host, ip);
1.38 markus 709: hostp = hostline;
1.161 djm 710: if (options.hash_known_hosts) {
711: /* Add hash of host and IP separately */
712: r = add_host_to_hostfile(user_hostfile, host,
713: host_key, options.hash_known_hosts) &&
714: add_host_to_hostfile(user_hostfile, ip,
715: host_key, options.hash_known_hosts);
716: } else {
717: /* Add unhashed "host,ip" */
718: r = add_host_to_hostfile(user_hostfile,
719: hostline, host_key,
720: options.hash_known_hosts);
721: }
722: } else {
723: r = add_host_to_hostfile(user_hostfile, host, host_key,
724: options.hash_known_hosts);
1.38 markus 725: hostp = host;
1.161 djm 726: }
1.38 markus 727:
1.161 djm 728: if (!r)
1.138 itojun 729: logit("Failed to add the host to the list of known "
1.108 markus 730: "hosts (%.500s).", user_hostfile);
1.38 markus 731: else
1.138 itojun 732: logit("Warning: Permanently added '%.200s' (%s) to the "
1.108 markus 733: "list of known hosts.", hostp, type);
1.38 markus 734: break;
735: case HOST_CHANGED:
736: if (options.check_host_ip && host_ip_differ) {
1.158 avsm 737: char *key_msg;
1.38 markus 738: if (ip_status == HOST_NEW)
1.158 avsm 739: key_msg = "is unknown";
1.38 markus 740: else if (ip_status == HOST_OK)
1.158 avsm 741: key_msg = "is unchanged";
1.38 markus 742: else
1.158 avsm 743: key_msg = "has a different value";
1.38 markus 744: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
745: error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
746: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1.72 markus 747: error("The %s host key for %s has changed,", type, host);
1.38 markus 748: error("and the key for the according IP address %s", ip);
1.158 avsm 749: error("%s. This could either mean that", key_msg);
1.38 markus 750: error("DNS SPOOFING is happening or the IP address for the host");
1.85 markus 751: error("and its host key have changed at the same time.");
1.88 markus 752: if (ip_status != HOST_NEW)
1.85 markus 753: error("Offending key for IP in %s:%d", ip_file, ip_line);
1.38 markus 754: }
755: /* The host key has changed. */
1.150 jakob 756: warn_changed_key(host_key);
1.38 markus 757: error("Add correct host key in %.100s to get rid of this message.",
1.87 markus 758: user_hostfile);
1.85 markus 759: error("Offending key in %s:%d", host_file, host_line);
1.38 markus 760:
1.40 markus 761: /*
762: * If strict host key checking is in use, the user will have
763: * to edit the key manually and we can only abort.
764: */
1.108 markus 765: if (options.strict_host_key_checking) {
766: error("%s host key for %.200s has changed and you have "
767: "requested strict checking.", type, host);
768: goto fail;
769: }
1.38 markus 770:
1.40 markus 771: /*
772: * If strict host key checking has not been requested, allow
1.144 djm 773: * the connection but without MITM-able authentication or
1.40 markus 774: * agent forwarding.
775: */
1.38 markus 776: if (options.password_authentication) {
1.108 markus 777: error("Password authentication is disabled to avoid "
778: "man-in-the-middle attacks.");
1.38 markus 779: options.password_authentication = 0;
1.144 djm 780: }
781: if (options.kbd_interactive_authentication) {
782: error("Keyboard-interactive authentication is disabled"
783: " to avoid man-in-the-middle attacks.");
784: options.kbd_interactive_authentication = 0;
785: options.challenge_response_authentication = 0;
786: }
787: if (options.challenge_response_authentication) {
788: error("Challenge/response authentication is disabled"
789: " to avoid man-in-the-middle attacks.");
790: options.challenge_response_authentication = 0;
1.38 markus 791: }
792: if (options.forward_agent) {
1.108 markus 793: error("Agent forwarding is disabled to avoid "
794: "man-in-the-middle attacks.");
1.38 markus 795: options.forward_agent = 0;
1.83 markus 796: }
797: if (options.forward_x11) {
1.108 markus 798: error("X11 forwarding is disabled to avoid "
799: "man-in-the-middle attacks.");
1.83 markus 800: options.forward_x11 = 0;
801: }
1.108 markus 802: if (options.num_local_forwards > 0 ||
803: options.num_remote_forwards > 0) {
804: error("Port forwarding is disabled to avoid "
805: "man-in-the-middle attacks.");
806: options.num_local_forwards =
1.118 deraadt 807: options.num_remote_forwards = 0;
1.38 markus 808: }
1.40 markus 809: /*
810: * XXX Should permit the user to change to use the new id.
811: * This could be done by converting the host key to an
812: * identifying sentence, tell that the host identifies itself
813: * by that sentence, and ask the user if he/she whishes to
814: * accept the authentication.
815: */
1.38 markus 816: break;
1.132 markus 817: case HOST_FOUND:
818: fatal("internal error");
819: break;
1.88 markus 820: }
821:
822: if (options.check_host_ip && host_status != HOST_CHANGED &&
823: ip_status == HOST_CHANGED) {
1.119 markus 824: snprintf(msg, sizeof(msg),
825: "Warning: the %s host key for '%.200s' "
826: "differs from the key for the IP address '%.128s'"
827: "\nOffending key for IP in %s:%d",
828: type, host, ip, ip_file, ip_line);
829: if (host_status == HOST_OK) {
830: len = strlen(msg);
831: snprintf(msg + len, sizeof(msg) - len,
832: "\nMatching host key in %s:%d",
1.125 deraadt 833: host_file, host_line);
1.119 markus 834: }
1.88 markus 835: if (options.strict_host_key_checking == 1) {
1.143 djm 836: logit("%s", msg);
1.108 markus 837: error("Exiting, you have requested strict checking.");
838: goto fail;
1.88 markus 839: } else if (options.strict_host_key_checking == 2) {
1.119 markus 840: strlcat(msg, "\nAre you sure you want "
841: "to continue connecting (yes/no)? ", sizeof(msg));
842: if (!confirm(msg))
1.108 markus 843: goto fail;
1.119 markus 844: } else {
1.143 djm 845: logit("%s", msg);
1.88 markus 846: }
1.38 markus 847: }
1.82 provos 848:
849: xfree(ip);
1.108 markus 850: return 0;
851:
852: fail:
853: xfree(ip);
854: return -1;
855: }
856:
1.140 jakob 857: /* returns 0 if key verifies or -1 if key does NOT verify */
1.108 markus 858: int
859: verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
860: {
861: struct stat st;
1.153 jakob 862: int flags = 0;
1.140 jakob 863:
1.153 jakob 864: if (options.verify_host_key_dns &&
865: verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
866:
867: if (flags & DNS_VERIFY_FOUND) {
868:
869: if (options.verify_host_key_dns == 1 &&
870: flags & DNS_VERIFY_MATCH &&
871: flags & DNS_VERIFY_SECURE)
872: return 0;
873:
874: if (flags & DNS_VERIFY_MATCH) {
875: matching_host_key_dns = 1;
876: } else {
877: warn_changed_key(host_key);
878: error("Update the SSHFP RR in DNS with the new "
879: "host key to get rid of this message.");
880: }
1.140 jakob 881: }
882: }
1.108 markus 883:
884: /* return ok if the key can be found in an old keyfile */
885: if (stat(options.system_hostfile2, &st) == 0 ||
886: stat(options.user_hostfile2, &st) == 0) {
887: if (check_host_key(host, hostaddr, host_key, /*readonly*/ 1,
888: options.user_hostfile2, options.system_hostfile2) == 0)
889: return 0;
890: }
891: return check_host_key(host, hostaddr, host_key, /*readonly*/ 0,
892: options.user_hostfile, options.system_hostfile);
1.51 markus 893: }
1.70 markus 894:
1.51 markus 895: /*
896: * Starts a dialog with the server, and authenticates the current user on the
897: * server. This does not need any extra privileges. The basic connection
898: * to the server must already have been established before this is called.
899: * If login fails, this function prints an error and never returns.
900: * This function does not require super-user privileges.
901: */
902: void
1.120 markus 903: ssh_login(Sensitive *sensitive, const char *orighost,
1.103 markus 904: struct sockaddr *hostaddr, struct passwd *pw)
1.51 markus 905: {
906: char *host, *cp;
1.70 markus 907: char *server_user, *local_user;
908:
909: local_user = xstrdup(pw->pw_name);
910: server_user = options.user ? options.user : local_user;
1.51 markus 911:
912: /* Convert the user-supplied hostname into all lowercase. */
913: host = xstrdup(orighost);
914: for (cp = host; *cp; cp++)
915: if (isupper(*cp))
916: *cp = tolower(*cp);
917:
918: /* Exchange protocol version identification strings with the server. */
919: ssh_exchange_identification();
920:
921: /* Put the connection into non-blocking mode. */
922: packet_set_nonblocking();
923:
924: /* key exchange */
925: /* authenticate user */
1.59 markus 926: if (compat20) {
927: ssh_kex2(host, hostaddr);
1.120 markus 928: ssh_userauth2(local_user, server_user, host, sensitive);
1.59 markus 929: } else {
930: ssh_kex(host, hostaddr);
1.120 markus 931: ssh_userauth1(local_user, server_user, host, sensitive);
1.59 markus 932: }
1.97 markus 933: }
934:
935: void
936: ssh_put_password(char *password)
937: {
938: int size;
939: char *padded;
940:
1.99 deraadt 941: if (datafellows & SSH_BUG_PASSWORDPAD) {
1.107 markus 942: packet_put_cstring(password);
1.99 deraadt 943: return;
944: }
1.97 markus 945: size = roundup(strlen(password) + 1, 32);
946: padded = xmalloc(size);
947: memset(padded, 0, size);
948: strlcpy(padded, password, size);
949: packet_put_string(padded, size);
950: memset(padded, 0, size);
951: xfree(padded);
1.132 markus 952: }
953:
954: static int
955: show_key_from_file(const char *file, const char *host, int keytype)
956: {
957: Key *found;
958: char *fp;
959: int line, ret;
960:
961: found = key_new(keytype);
962: if ((ret = lookup_key_in_hostfile_by_type(file, host,
963: keytype, found, &line))) {
964: fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
1.138 itojun 965: logit("WARNING: %s key found for host %s\n"
1.133 markus 966: "in %s:%d\n"
1.132 markus 967: "%s key fingerprint %s.",
968: key_type(found), host, file, line,
969: key_type(found), fp);
970: xfree(fp);
971: }
972: key_free(found);
973: return (ret);
974: }
975:
976: /* print all known host keys for a given host, but skip keys of given type */
977: static int
978: show_other_keys(const char *host, Key *key)
979: {
980: int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1};
981: int i, found = 0;
982:
983: for (i = 0; type[i] != -1; i++) {
984: if (type[i] == key->type)
985: continue;
986: if (type[i] != KEY_RSA1 &&
987: show_key_from_file(options.user_hostfile2, host, type[i])) {
988: found = 1;
989: continue;
990: }
991: if (type[i] != KEY_RSA1 &&
992: show_key_from_file(options.system_hostfile2, host, type[i])) {
993: found = 1;
994: continue;
995: }
996: if (show_key_from_file(options.user_hostfile, host, type[i])) {
997: found = 1;
998: continue;
999: }
1000: if (show_key_from_file(options.system_hostfile, host, type[i])) {
1001: found = 1;
1002: continue;
1003: }
1004: debug2("no key of type %d for host %s", type[i], host);
1005: }
1006: return (found);
1.150 jakob 1007: }
1008:
1009: static void
1010: warn_changed_key(Key *host_key)
1011: {
1012: char *fp;
1.151 jakob 1013: const char *type = key_type(host_key);
1.150 jakob 1014:
1015: fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1016:
1017: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1018: error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1019: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1020: error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1021: error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1022: error("It is also possible that the %s host key has just been changed.", type);
1023: error("The fingerprint for the %s key sent by the remote host is\n%s.",
1024: type, fp);
1025: error("Please contact your system administrator.");
1026:
1027: xfree(fp);
1.1 deraadt 1028: }
![[BACK]](/icons/back.gif){kind=icon}
Return to sshconnect.c CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh