Annotation of src/usr.bin/ssh/sshconnect.c, Revision 1.188
1.188 ! stevesk 1: /* $OpenBSD: sshconnect.c,v 1.187 2006/07/05 02:42:09 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>
1.172 stevesk 26: #include <paths.h>
1.188 ! stevesk 27: #include <pwd.h>
1.71 markus 28:
1.91 markus 29: #include "ssh.h"
1.1 deraadt 30: #include "xmalloc.h"
31: #include "rsa.h"
1.59 markus 32: #include "buffer.h"
1.1 deraadt 33: #include "packet.h"
34: #include "uidswap.h"
1.21 markus 35: #include "compat.h"
1.58 markus 36: #include "key.h"
1.71 markus 37: #include "sshconnect.h"
1.58 markus 38: #include "hostfile.h"
1.91 markus 39: #include "log.h"
40: #include "readconf.h"
41: #include "atomicio.h"
42: #include "misc.h"
1.140 jakob 43: #include "dns.h"
1.186 stevesk 44: #include "version.h"
1.140 jakob 45:
1.70 markus 46: char *client_version_string = NULL;
47: char *server_version_string = NULL;
1.59 markus 48:
1.169 stevesk 49: static int matching_host_key_dns = 0;
1.145 jakob 50:
1.124 markus 51: /* import */
1.43 markus 52: extern Options options;
1.50 markus 53: extern char *__progname;
1.124 markus 54: extern uid_t original_real_uid;
55: extern uid_t original_effective_uid;
1.135 djm 56: extern pid_t proxy_command_pid;
1.91 markus 57:
1.132 markus 58: static int show_other_keys(const char *, Key *);
1.150 jakob 59: static void warn_changed_key(Key *);
1.132 markus 60:
1.39 deraadt 61: /*
62: * Connect to the given ssh server using a proxy command.
63: */
1.109 itojun 64: static int
1.124 markus 65: ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
1.1 deraadt 66: {
1.164 djm 67: char *command_string, *tmp;
1.38 markus 68: int pin[2], pout[2];
1.69 deraadt 69: pid_t pid;
1.49 markus 70: char strport[NI_MAXSERV];
1.38 markus 71:
72: /* Convert the port number into a string. */
1.49 markus 73: snprintf(strport, sizeof strport, "%hu", port);
1.38 markus 74:
1.135 djm 75: /*
76: * Build the final command string in the buffer by making the
77: * appropriate substitutions to the given proxy command.
78: *
1.154 djm 79: * Use "exec" to avoid "sh -c" processes on some platforms
1.135 djm 80: * (e.g. Solaris)
81: */
1.179 djm 82: xasprintf(&tmp, "exec %s", proxy_command);
1.164 djm 83: command_string = percent_expand(tmp, "h", host,
84: "p", strport, (char *)NULL);
85: xfree(tmp);
1.38 markus 86:
87: /* Create pipes for communicating with the proxy. */
88: if (pipe(pin) < 0 || pipe(pout) < 0)
89: fatal("Could not create pipes to communicate with the proxy: %.100s",
1.118 deraadt 90: strerror(errno));
1.38 markus 91:
92: debug("Executing proxy command: %.500s", command_string);
93:
94: /* Fork and execute the proxy command. */
95: if ((pid = fork()) == 0) {
96: char *argv[10];
97:
98: /* Child. Permanently give up superuser privileges. */
1.184 markus 99: permanently_drop_suid(original_real_uid);
1.38 markus 100:
101: /* Redirect stdin and stdout. */
102: close(pin[1]);
103: if (pin[0] != 0) {
104: if (dup2(pin[0], 0) < 0)
105: perror("dup2 stdin");
106: close(pin[0]);
107: }
108: close(pout[0]);
109: if (dup2(pout[1], 1) < 0)
110: perror("dup2 stdout");
111: /* Cannot be 1 because pin allocated two descriptors. */
112: close(pout[1]);
113:
114: /* Stderr is left as it is so that error messages get
115: printed on the user's terminal. */
1.89 markus 116: argv[0] = _PATH_BSHELL;
1.38 markus 117: argv[1] = "-c";
118: argv[2] = command_string;
119: argv[3] = NULL;
120:
121: /* Execute the proxy command. Note that we gave up any
122: extra privileges above. */
1.89 markus 123: execv(argv[0], argv);
124: perror(argv[0]);
1.38 markus 125: exit(1);
126: }
127: /* Parent. */
128: if (pid < 0)
129: fatal("fork failed: %.100s", strerror(errno));
1.135 djm 130: else
131: proxy_command_pid = pid; /* save pid to clean up later */
1.38 markus 132:
133: /* Close child side of the descriptors. */
134: close(pin[0]);
135: close(pout[1]);
136:
137: /* Free the command name. */
1.164 djm 138: xfree(command_string);
1.38 markus 139:
140: /* Set the connection file descriptors. */
141: packet_set_connection(pout[0], pin[1]);
1.1 deraadt 142:
1.110 markus 143: /* Indicate OK return */
144: return 0;
1.1 deraadt 145: }
146:
1.39 deraadt 147: /*
148: * Creates a (possibly privileged) socket for use as the ssh connection.
149: */
1.109 itojun 150: static int
1.139 markus 151: ssh_create_socket(int privileged, struct addrinfo *ai)
1.1 deraadt 152: {
1.105 markus 153: int sock, gaierr;
154: struct addrinfo hints, *res;
1.1 deraadt 155:
1.40 markus 156: /*
157: * If we are running as root and want to connect to a privileged
158: * port, bind our own socket to a privileged port.
159: */
1.38 markus 160: if (privileged) {
161: int p = IPPORT_RESERVED - 1;
1.124 markus 162: PRIV_START;
1.139 markus 163: sock = rresvport_af(&p, ai->ai_family);
1.124 markus 164: PRIV_END;
1.38 markus 165: if (sock < 0)
1.139 markus 166: error("rresvport: af=%d %.100s", ai->ai_family,
167: strerror(errno));
1.55 markus 168: else
169: debug("Allocated local port %d.", p);
1.105 markus 170: return sock;
171: }
1.139 markus 172: sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
1.105 markus 173: if (sock < 0)
174: error("socket: %.100s", strerror(errno));
175:
176: /* Bind the socket to an alternative local IP address */
177: if (options.bind_address == NULL)
178: return sock;
179:
180: memset(&hints, 0, sizeof(hints));
1.139 markus 181: hints.ai_family = ai->ai_family;
182: hints.ai_socktype = ai->ai_socktype;
183: hints.ai_protocol = ai->ai_protocol;
1.105 markus 184: hints.ai_flags = AI_PASSIVE;
185: gaierr = getaddrinfo(options.bind_address, "0", &hints, &res);
186: if (gaierr) {
187: error("getaddrinfo: %s: %s", options.bind_address,
188: gai_strerror(gaierr));
189: close(sock);
190: return -1;
191: }
192: if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
193: error("bind: %s: %s", options.bind_address, strerror(errno));
194: close(sock);
195: freeaddrinfo(res);
196: return -1;
1.38 markus 197: }
1.105 markus 198: freeaddrinfo(res);
1.38 markus 199: return sock;
1.1 deraadt 200: }
201:
1.141 djm 202: static int
203: timeout_connect(int sockfd, const struct sockaddr *serv_addr,
204: socklen_t addrlen, int timeout)
205: {
206: fd_set *fdset;
207: struct timeval tv;
208: socklen_t optlen;
1.179 djm 209: int optval, rc, result = -1;
1.141 djm 210:
211: if (timeout <= 0)
212: return (connect(sockfd, serv_addr, addrlen));
213:
1.156 djm 214: set_nonblock(sockfd);
1.141 djm 215: rc = connect(sockfd, serv_addr, addrlen);
1.156 djm 216: if (rc == 0) {
217: unset_nonblock(sockfd);
1.141 djm 218: return (0);
1.156 djm 219: }
1.141 djm 220: if (errno != EINPROGRESS)
221: return (-1);
222:
1.179 djm 223: fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
224: sizeof(fd_mask));
1.141 djm 225: FD_SET(sockfd, fdset);
226: tv.tv_sec = timeout;
227: tv.tv_usec = 0;
228:
1.162 deraadt 229: for (;;) {
1.141 djm 230: rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
231: if (rc != -1 || errno != EINTR)
232: break;
233: }
234:
1.162 deraadt 235: switch (rc) {
1.141 djm 236: case 0:
237: /* Timed out */
238: errno = ETIMEDOUT;
1.142 djm 239: break;
1.141 djm 240: case -1:
241: /* Select error */
1.154 djm 242: debug("select: %s", strerror(errno));
1.142 djm 243: break;
1.141 djm 244: case 1:
245: /* Completed or failed */
246: optval = 0;
247: optlen = sizeof(optval);
1.154 djm 248: if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
1.148 markus 249: &optlen) == -1) {
1.154 djm 250: debug("getsockopt: %s", strerror(errno));
1.142 djm 251: break;
1.148 markus 252: }
1.141 djm 253: if (optval != 0) {
254: errno = optval;
1.142 djm 255: break;
1.141 djm 256: }
1.142 djm 257: result = 0;
1.156 djm 258: unset_nonblock(sockfd);
1.141 djm 259: break;
260: default:
261: /* Should not occur */
262: fatal("Bogus return (%d) from select()", rc);
263: }
264:
1.142 djm 265: xfree(fdset);
266: return (result);
1.141 djm 267: }
268:
1.39 deraadt 269: /*
1.49 markus 270: * Opens a TCP/IP connection to the remote server on the given host.
271: * The address of the remote host will be returned in hostaddr.
1.124 markus 272: * If port is 0, the default port will be used. If needpriv is true,
1.39 deraadt 273: * a privileged port will be allocated to make the connection.
1.124 markus 274: * This requires super-user privileges if needpriv is true.
1.39 deraadt 275: * Connection_attempts specifies the maximum number of tries (one per
276: * second). If proxy_command is non-NULL, it specifies the command (with %h
277: * and %p substituted for host and port, respectively) to use to contact
278: * the daemon.
279: */
1.38 markus 280: int
1.49 markus 281: ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
1.115 markus 282: u_short port, int family, int connection_attempts,
1.124 markus 283: int needpriv, const char *proxy_command)
1.1 deraadt 284: {
1.90 markus 285: int gaierr;
286: int on = 1;
1.49 markus 287: int sock = -1, attempt;
1.90 markus 288: char ntop[NI_MAXHOST], strport[NI_MAXSERV];
1.49 markus 289: struct addrinfo hints, *ai, *aitop;
1.38 markus 290:
1.136 markus 291: debug2("ssh_connect: needpriv %d", needpriv);
1.38 markus 292:
293: /* If a proxy command is given, connect using it. */
294: if (proxy_command != NULL)
1.124 markus 295: return ssh_proxy_connect(host, port, proxy_command);
1.38 markus 296:
297: /* No proxy command. */
298:
1.49 markus 299: memset(&hints, 0, sizeof(hints));
1.115 markus 300: hints.ai_family = family;
1.49 markus 301: hints.ai_socktype = SOCK_STREAM;
1.126 deraadt 302: snprintf(strport, sizeof strport, "%u", port);
1.49 markus 303: if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
1.50 markus 304: fatal("%s: %.100s: %s", __progname, host,
305: gai_strerror(gaierr));
1.38 markus 306:
1.181 markus 307: for (attempt = 0; attempt < connection_attempts; attempt++) {
1.38 markus 308: if (attempt > 0)
309: debug("Trying again...");
310:
1.181 markus 311: /*
312: * Loop through addresses for this host, and try each one in
313: * sequence until the connection succeeds.
314: */
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));
1.38 markus 341: close(sock);
1.181 markus 342: sock = -1;
1.38 markus 343: }
344: }
1.181 markus 345: if (sock != -1)
1.49 markus 346: break; /* Successful connection. */
1.1 deraadt 347:
1.38 markus 348: /* Sleep a moment before retrying. */
349: sleep(1);
350: }
1.49 markus 351:
352: freeaddrinfo(aitop);
353:
1.38 markus 354: /* Return failure if we didn't get a successful connection. */
1.181 markus 355: if (sock == -1) {
1.159 markus 356: error("ssh: connect to host %s port %s: %s",
1.130 itojun 357: host, strport, strerror(errno));
1.159 markus 358: return (-1);
1.130 itojun 359: }
1.38 markus 360:
361: debug("Connection established.");
1.90 markus 362:
1.155 markus 363: /* Set SO_KEEPALIVE if requested. */
364: if (options.tcp_keep_alive &&
1.90 markus 365: setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
366: sizeof(on)) < 0)
367: error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1.38 markus 368:
369: /* Set the connection. */
370: packet_set_connection(sock, sock);
1.1 deraadt 371:
1.110 markus 372: return 0;
1.59 markus 373: }
374:
1.43 markus 375: /*
1.39 deraadt 376: * Waits for the server identification string, and sends our own
377: * identification string.
378: */
1.109 itojun 379: static void
1.95 itojun 380: ssh_exchange_identification(void)
1.1 deraadt 381: {
1.38 markus 382: char buf[256], remote_version[256]; /* must be same size! */
1.165 djm 383: int remote_major, remote_minor, mismatch;
1.38 markus 384: int connection_in = packet_get_connection_in();
385: int connection_out = packet_get_connection_out();
1.93 stevesk 386: int minor1 = PROTOCOL_MINOR_1;
1.185 djm 387: u_int i, n;
1.38 markus 388:
1.163 avsm 389: /* Read other side's version identification. */
1.185 djm 390: for (n = 0;;) {
1.75 markus 391: for (i = 0; i < sizeof(buf) - 1; i++) {
1.163 avsm 392: size_t len = atomicio(read, connection_in, &buf[i], 1);
393:
1.167 djm 394: if (len != 1 && errno == EPIPE)
1.163 avsm 395: fatal("ssh_exchange_identification: Connection closed by remote host");
396: else if (len != 1)
1.75 markus 397: fatal("ssh_exchange_identification: read: %.100s", strerror(errno));
398: if (buf[i] == '\r') {
399: buf[i] = '\n';
400: buf[i + 1] = 0;
401: continue; /**XXX wait for \n */
402: }
403: if (buf[i] == '\n') {
404: buf[i + 1] = 0;
405: break;
406: }
1.185 djm 407: if (++n > 65536)
408: fatal("ssh_exchange_identification: No banner received");
1.38 markus 409: }
1.75 markus 410: buf[sizeof(buf) - 1] = 0;
1.76 markus 411: if (strncmp(buf, "SSH-", 4) == 0)
1.38 markus 412: break;
1.75 markus 413: debug("ssh_exchange_identification: %s", buf);
1.38 markus 414: }
1.59 markus 415: server_version_string = xstrdup(buf);
1.38 markus 416:
1.40 markus 417: /*
418: * Check that the versions match. In future this might accept
419: * several versions and set appropriate flags to handle them.
420: */
1.59 markus 421: if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
422: &remote_major, &remote_minor, remote_version) != 3)
1.38 markus 423: fatal("Bad remote protocol version identification: '%.100s'", buf);
424: debug("Remote protocol version %d.%d, remote software version %.100s",
1.118 deraadt 425: remote_major, remote_minor, remote_version);
1.38 markus 426:
1.59 markus 427: compat_datafellows(remote_version);
1.64 markus 428: mismatch = 0;
1.59 markus 429:
1.116 deraadt 430: switch (remote_major) {
1.64 markus 431: case 1:
432: if (remote_minor == 99 &&
433: (options.protocol & SSH_PROTO_2) &&
434: !(options.protocol & SSH_PROTO_1_PREFERRED)) {
435: enable_compat20();
436: break;
437: }
438: if (!(options.protocol & SSH_PROTO_1)) {
439: mismatch = 1;
440: break;
441: }
442: if (remote_minor < 3) {
443: fatal("Remote machine has too old SSH software version.");
1.81 markus 444: } else if (remote_minor == 3 || remote_minor == 4) {
1.64 markus 445: /* We speak 1.3, too. */
446: enable_compat13();
1.81 markus 447: minor1 = 3;
1.64 markus 448: if (options.forward_agent) {
1.138 itojun 449: logit("Agent forwarding disabled for protocol 1.3");
1.64 markus 450: options.forward_agent = 0;
451: }
452: }
453: break;
454: case 2:
455: if (options.protocol & SSH_PROTO_2) {
456: enable_compat20();
457: break;
1.38 markus 458: }
1.64 markus 459: /* FALLTHROUGH */
1.68 markus 460: default:
1.64 markus 461: mismatch = 1;
462: break;
1.38 markus 463: }
1.64 markus 464: if (mismatch)
1.38 markus 465: fatal("Protocol major versions differ: %d vs. %d",
1.64 markus 466: (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
467: remote_major);
1.38 markus 468: /* Send our own protocol version identification. */
469: snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
1.64 markus 470: compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
1.81 markus 471: compat20 ? PROTOCOL_MINOR_2 : minor1,
1.59 markus 472: SSH_VERSION);
1.146 deraadt 473: if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf))
1.38 markus 474: fatal("write: %.100s", strerror(errno));
1.59 markus 475: client_version_string = xstrdup(buf);
476: chop(client_version_string);
477: chop(server_version_string);
478: debug("Local version string %.100s", client_version_string);
1.1 deraadt 479: }
480:
1.96 markus 481: /* defaults to 'no' */
1.109 itojun 482: static int
1.112 markus 483: confirm(const char *prompt)
1.1 deraadt 484: {
1.119 markus 485: const char *msg, *again = "Please type 'yes' or 'no': ";
486: char *p;
487: int ret = -1;
1.96 markus 488:
489: if (options.batch_mode)
490: return 0;
1.119 markus 491: for (msg = prompt;;msg = again) {
492: p = read_passphrase(msg, RP_ECHO);
493: if (p == NULL ||
494: (p[0] == '\0') || (p[0] == '\n') ||
495: strncasecmp(p, "no", 2) == 0)
496: ret = 0;
1.127 markus 497: if (p && strncasecmp(p, "yes", 3) == 0)
1.119 markus 498: ret = 1;
499: if (p)
500: xfree(p);
501: if (ret != -1)
502: return ret;
1.1 deraadt 503: }
504: }
505:
1.39 deraadt 506: /*
1.108 markus 507: * check whether the supplied host key is valid, return -1 if the key
508: * is not valid. the user_hostfile will not be updated if 'readonly' is true.
1.39 deraadt 509: */
1.109 itojun 510: static int
1.70 markus 511: check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key,
1.108 markus 512: int readonly, const char *user_hostfile, const char *system_hostfile)
1.1 deraadt 513: {
1.58 markus 514: Key *file_key;
1.152 jakob 515: const char *type = key_type(host_key);
1.46 markus 516: char *ip = NULL;
1.100 markus 517: char hostline[1000], *hostp, *fp;
1.38 markus 518: HostStatus host_status;
519: HostStatus ip_status;
1.161 djm 520: int r, local = 0, host_ip_differ = 0;
1.49 markus 521: char ntop[NI_MAXHOST];
1.119 markus 522: char msg[1024];
1.145 jakob 523: int len, host_line, ip_line;
1.85 markus 524: const char *host_file = NULL, *ip_file = NULL;
1.49 markus 525:
526: /*
527: * Force accepting of the host key for loopback/localhost. The
528: * problem is that if the home directory is NFS-mounted to multiple
529: * machines, localhost will refer to a different machine in each of
530: * them, and the user will get bogus HOST_CHANGED warnings. This
531: * essentially disables host authentication for localhost; however,
532: * this is probably not a real problem.
533: */
1.70 markus 534: /** hostaddr == 0! */
1.49 markus 535: switch (hostaddr->sa_family) {
536: case AF_INET:
1.108 markus 537: local = (ntohl(((struct sockaddr_in *)hostaddr)->
1.168 djm 538: sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
1.49 markus 539: break;
540: case AF_INET6:
1.108 markus 541: local = IN6_IS_ADDR_LOOPBACK(
542: &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
1.49 markus 543: break;
544: default:
545: local = 0;
546: break;
547: }
1.111 markus 548: if (options.no_host_authentication_for_localhost == 1 && local &&
549: options.host_key_alias == NULL) {
1.88 markus 550: debug("Forcing accepting of host key for "
551: "loopback/localhost.");
1.108 markus 552: return 0;
1.49 markus 553: }
1.42 markus 554:
555: /*
1.88 markus 556: * We don't have the remote ip-address for connections
557: * using a proxy command
1.42 markus 558: */
1.84 markus 559: if (options.proxy_command == NULL) {
560: if (getnameinfo(hostaddr, hostaddr->sa_len, ntop, sizeof(ntop),
1.86 markus 561: NULL, 0, NI_NUMERICHOST) != 0)
1.84 markus 562: fatal("check_host_key: getnameinfo failed");
563: ip = xstrdup(ntop);
564: } else {
565: ip = xstrdup("<no hostip for proxy command>");
1.86 markus 566: }
1.88 markus 567: /*
568: * Turn off check_host_ip if the connection is to localhost, via proxy
569: * command or if we don't have a hostname to compare with
570: */
571: if (options.check_host_ip &&
572: (local || strcmp(host, ip) == 0 || options.proxy_command != NULL))
573: options.check_host_ip = 0;
1.86 markus 574:
575: /*
576: * Allow the user to record the key under a different name. This is
577: * useful for ssh tunneling over forwarded connections or if you run
578: * multiple sshd's on different ports on the same machine.
579: */
580: if (options.host_key_alias != NULL) {
581: host = options.host_key_alias;
582: debug("using hostkeyalias: %s", host);
1.84 markus 583: }
1.38 markus 584:
1.46 markus 585: /*
586: * Store the host key from the known host file in here so that we can
587: * compare it with the key for the IP address.
588: */
1.58 markus 589: file_key = key_new(host_key->type);
1.38 markus 590:
1.40 markus 591: /*
1.170 djm 592: * Check if the host key is present in the user's list of known
1.40 markus 593: * hosts or in the systemwide list.
594: */
1.85 markus 595: host_file = user_hostfile;
1.108 markus 596: host_status = check_host_in_hostfile(host_file, host, host_key,
1.118 deraadt 597: file_key, &host_line);
1.85 markus 598: if (host_status == HOST_NEW) {
599: host_file = system_hostfile;
1.108 markus 600: host_status = check_host_in_hostfile(host_file, host, host_key,
601: file_key, &host_line);
1.85 markus 602: }
1.40 markus 603: /*
604: * Also perform check for the ip address, skip the check if we are
605: * localhost or the hostname was an ip address to begin with
606: */
1.88 markus 607: if (options.check_host_ip) {
1.58 markus 608: Key *ip_key = key_new(host_key->type);
1.38 markus 609:
1.85 markus 610: ip_file = user_hostfile;
1.108 markus 611: ip_status = check_host_in_hostfile(ip_file, ip, host_key,
612: ip_key, &ip_line);
1.85 markus 613: if (ip_status == HOST_NEW) {
614: ip_file = system_hostfile;
1.108 markus 615: ip_status = check_host_in_hostfile(ip_file, ip,
616: host_key, ip_key, &ip_line);
1.85 markus 617: }
1.38 markus 618: if (host_status == HOST_CHANGED &&
1.58 markus 619: (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
1.38 markus 620: host_ip_differ = 1;
621:
1.58 markus 622: key_free(ip_key);
1.38 markus 623: } else
624: ip_status = host_status;
625:
1.58 markus 626: key_free(file_key);
1.38 markus 627:
628: switch (host_status) {
629: case HOST_OK:
630: /* The host is known and the key matches. */
1.72 markus 631: debug("Host '%.200s' is known and matches the %s host key.",
632: host, type);
1.85 markus 633: debug("Found key in %s:%d", host_file, host_line);
1.88 markus 634: if (options.check_host_ip && ip_status == HOST_NEW) {
1.108 markus 635: if (readonly)
1.138 itojun 636: logit("%s host key for IP address "
1.108 markus 637: "'%.128s' not in list of known hosts.",
638: type, ip);
639: else if (!add_host_to_hostfile(user_hostfile, ip,
1.160 djm 640: host_key, options.hash_known_hosts))
1.138 itojun 641: logit("Failed to add the %s host key for IP "
1.108 markus 642: "address '%.128s' to the list of known "
643: "hosts (%.30s).", type, ip, user_hostfile);
1.88 markus 644: else
1.138 itojun 645: logit("Warning: Permanently added the %s host "
1.108 markus 646: "key for IP address '%.128s' to the list "
647: "of known hosts.", type, ip);
1.38 markus 648: }
649: break;
650: case HOST_NEW:
1.108 markus 651: if (readonly)
652: goto fail;
1.38 markus 653: /* The host is new. */
654: if (options.strict_host_key_checking == 1) {
1.108 markus 655: /*
656: * User has requested strict host key checking. We
657: * will not add the host key automatically. The only
658: * alternative left is to abort.
659: */
660: error("No %s host key is known for %.200s and you "
661: "have requested strict checking.", type, host);
662: goto fail;
1.38 markus 663: } else if (options.strict_host_key_checking == 2) {
1.145 jakob 664: char msg1[1024], msg2[1024];
665:
666: if (show_other_keys(host, host_key))
667: snprintf(msg1, sizeof(msg1),
1.168 djm 668: "\nbut keys of different type are already"
669: " known for this host.");
1.145 jakob 670: else
671: snprintf(msg1, sizeof(msg1), ".");
1.38 markus 672: /* The default */
1.100 markus 673: fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1.145 jakob 674: msg2[0] = '\0';
675: if (options.verify_host_key_dns) {
1.153 jakob 676: if (matching_host_key_dns)
1.145 jakob 677: snprintf(msg2, sizeof(msg2),
678: "Matching host key fingerprint"
679: " found in DNS.\n");
680: else
681: snprintf(msg2, sizeof(msg2),
682: "No matching host key fingerprint"
683: " found in DNS.\n");
684: }
1.119 markus 685: snprintf(msg, sizeof(msg),
1.108 markus 686: "The authenticity of host '%.200s (%s)' can't be "
1.132 markus 687: "established%s\n"
1.145 jakob 688: "%s key fingerprint is %s.\n%s"
1.108 markus 689: "Are you sure you want to continue connecting "
1.132 markus 690: "(yes/no)? ",
1.145 jakob 691: host, ip, msg1, type, fp, msg2);
1.100 markus 692: xfree(fp);
1.119 markus 693: if (!confirm(msg))
1.108 markus 694: goto fail;
1.38 markus 695: }
1.161 djm 696: /*
697: * If not in strict mode, add the key automatically to the
698: * local known_hosts file.
699: */
1.88 markus 700: if (options.check_host_ip && ip_status == HOST_NEW) {
1.161 djm 701: snprintf(hostline, sizeof(hostline), "%s,%s",
702: host, ip);
1.38 markus 703: hostp = hostline;
1.161 djm 704: if (options.hash_known_hosts) {
705: /* Add hash of host and IP separately */
706: r = add_host_to_hostfile(user_hostfile, host,
707: host_key, options.hash_known_hosts) &&
708: add_host_to_hostfile(user_hostfile, ip,
709: host_key, options.hash_known_hosts);
710: } else {
711: /* Add unhashed "host,ip" */
712: r = add_host_to_hostfile(user_hostfile,
713: hostline, host_key,
714: options.hash_known_hosts);
715: }
716: } else {
717: r = add_host_to_hostfile(user_hostfile, host, host_key,
718: options.hash_known_hosts);
1.38 markus 719: hostp = host;
1.161 djm 720: }
1.38 markus 721:
1.161 djm 722: if (!r)
1.138 itojun 723: logit("Failed to add the host to the list of known "
1.108 markus 724: "hosts (%.500s).", user_hostfile);
1.38 markus 725: else
1.138 itojun 726: logit("Warning: Permanently added '%.200s' (%s) to the "
1.108 markus 727: "list of known hosts.", hostp, type);
1.38 markus 728: break;
729: case HOST_CHANGED:
730: if (options.check_host_ip && host_ip_differ) {
1.158 avsm 731: char *key_msg;
1.38 markus 732: if (ip_status == HOST_NEW)
1.158 avsm 733: key_msg = "is unknown";
1.38 markus 734: else if (ip_status == HOST_OK)
1.158 avsm 735: key_msg = "is unchanged";
1.38 markus 736: else
1.158 avsm 737: key_msg = "has a different value";
1.38 markus 738: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
739: error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
740: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1.72 markus 741: error("The %s host key for %s has changed,", type, host);
1.38 markus 742: error("and the key for the according IP address %s", ip);
1.158 avsm 743: error("%s. This could either mean that", key_msg);
1.38 markus 744: error("DNS SPOOFING is happening or the IP address for the host");
1.85 markus 745: error("and its host key have changed at the same time.");
1.88 markus 746: if (ip_status != HOST_NEW)
1.85 markus 747: error("Offending key for IP in %s:%d", ip_file, ip_line);
1.38 markus 748: }
749: /* The host key has changed. */
1.150 jakob 750: warn_changed_key(host_key);
1.38 markus 751: error("Add correct host key in %.100s to get rid of this message.",
1.87 markus 752: user_hostfile);
1.85 markus 753: error("Offending key in %s:%d", host_file, host_line);
1.38 markus 754:
1.40 markus 755: /*
756: * If strict host key checking is in use, the user will have
757: * to edit the key manually and we can only abort.
758: */
1.108 markus 759: if (options.strict_host_key_checking) {
760: error("%s host key for %.200s has changed and you have "
761: "requested strict checking.", type, host);
762: goto fail;
763: }
1.38 markus 764:
1.40 markus 765: /*
766: * If strict host key checking has not been requested, allow
1.144 djm 767: * the connection but without MITM-able authentication or
1.40 markus 768: * agent forwarding.
769: */
1.38 markus 770: if (options.password_authentication) {
1.108 markus 771: error("Password authentication is disabled to avoid "
772: "man-in-the-middle attacks.");
1.38 markus 773: options.password_authentication = 0;
1.144 djm 774: }
775: if (options.kbd_interactive_authentication) {
776: error("Keyboard-interactive authentication is disabled"
777: " to avoid man-in-the-middle attacks.");
778: options.kbd_interactive_authentication = 0;
779: options.challenge_response_authentication = 0;
780: }
781: if (options.challenge_response_authentication) {
782: error("Challenge/response authentication is disabled"
783: " to avoid man-in-the-middle attacks.");
784: options.challenge_response_authentication = 0;
1.38 markus 785: }
786: if (options.forward_agent) {
1.108 markus 787: error("Agent forwarding is disabled to avoid "
788: "man-in-the-middle attacks.");
1.38 markus 789: options.forward_agent = 0;
1.83 markus 790: }
791: if (options.forward_x11) {
1.108 markus 792: error("X11 forwarding is disabled to avoid "
793: "man-in-the-middle attacks.");
1.83 markus 794: options.forward_x11 = 0;
795: }
1.108 markus 796: if (options.num_local_forwards > 0 ||
797: options.num_remote_forwards > 0) {
798: error("Port forwarding is disabled to avoid "
799: "man-in-the-middle attacks.");
800: options.num_local_forwards =
1.118 deraadt 801: options.num_remote_forwards = 0;
1.38 markus 802: }
1.40 markus 803: /*
804: * XXX Should permit the user to change to use the new id.
805: * This could be done by converting the host key to an
806: * identifying sentence, tell that the host identifies itself
807: * by that sentence, and ask the user if he/she whishes to
808: * accept the authentication.
809: */
1.38 markus 810: break;
1.132 markus 811: case HOST_FOUND:
812: fatal("internal error");
813: break;
1.88 markus 814: }
815:
816: if (options.check_host_ip && host_status != HOST_CHANGED &&
817: ip_status == HOST_CHANGED) {
1.119 markus 818: snprintf(msg, sizeof(msg),
819: "Warning: the %s host key for '%.200s' "
820: "differs from the key for the IP address '%.128s'"
821: "\nOffending key for IP in %s:%d",
822: type, host, ip, ip_file, ip_line);
823: if (host_status == HOST_OK) {
824: len = strlen(msg);
825: snprintf(msg + len, sizeof(msg) - len,
826: "\nMatching host key in %s:%d",
1.125 deraadt 827: host_file, host_line);
1.119 markus 828: }
1.88 markus 829: if (options.strict_host_key_checking == 1) {
1.143 djm 830: logit("%s", msg);
1.108 markus 831: error("Exiting, you have requested strict checking.");
832: goto fail;
1.88 markus 833: } else if (options.strict_host_key_checking == 2) {
1.119 markus 834: strlcat(msg, "\nAre you sure you want "
835: "to continue connecting (yes/no)? ", sizeof(msg));
836: if (!confirm(msg))
1.108 markus 837: goto fail;
1.119 markus 838: } else {
1.143 djm 839: logit("%s", msg);
1.88 markus 840: }
1.38 markus 841: }
1.82 provos 842:
843: xfree(ip);
1.108 markus 844: return 0;
845:
846: fail:
847: xfree(ip);
848: return -1;
849: }
850:
1.140 jakob 851: /* returns 0 if key verifies or -1 if key does NOT verify */
1.108 markus 852: int
853: verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
854: {
855: struct stat st;
1.153 jakob 856: int flags = 0;
1.140 jakob 857:
1.153 jakob 858: if (options.verify_host_key_dns &&
859: verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
860:
861: if (flags & DNS_VERIFY_FOUND) {
862:
863: if (options.verify_host_key_dns == 1 &&
864: flags & DNS_VERIFY_MATCH &&
865: flags & DNS_VERIFY_SECURE)
866: return 0;
867:
868: if (flags & DNS_VERIFY_MATCH) {
869: matching_host_key_dns = 1;
870: } else {
871: warn_changed_key(host_key);
872: error("Update the SSHFP RR in DNS with the new "
873: "host key to get rid of this message.");
874: }
1.140 jakob 875: }
876: }
1.108 markus 877:
878: /* return ok if the key can be found in an old keyfile */
879: if (stat(options.system_hostfile2, &st) == 0 ||
880: stat(options.user_hostfile2, &st) == 0) {
881: if (check_host_key(host, hostaddr, host_key, /*readonly*/ 1,
882: options.user_hostfile2, options.system_hostfile2) == 0)
883: return 0;
884: }
885: return check_host_key(host, hostaddr, host_key, /*readonly*/ 0,
886: options.user_hostfile, options.system_hostfile);
1.51 markus 887: }
1.70 markus 888:
1.51 markus 889: /*
890: * Starts a dialog with the server, and authenticates the current user on the
891: * server. This does not need any extra privileges. The basic connection
892: * to the server must already have been established before this is called.
893: * If login fails, this function prints an error and never returns.
894: * This function does not require super-user privileges.
895: */
896: void
1.120 markus 897: ssh_login(Sensitive *sensitive, const char *orighost,
1.103 markus 898: struct sockaddr *hostaddr, struct passwd *pw)
1.51 markus 899: {
900: char *host, *cp;
1.70 markus 901: char *server_user, *local_user;
902:
903: local_user = xstrdup(pw->pw_name);
904: server_user = options.user ? options.user : local_user;
1.51 markus 905:
906: /* Convert the user-supplied hostname into all lowercase. */
907: host = xstrdup(orighost);
908: for (cp = host; *cp; cp++)
909: if (isupper(*cp))
1.178 deraadt 910: *cp = (char)tolower(*cp);
1.51 markus 911:
912: /* Exchange protocol version identification strings with the server. */
913: ssh_exchange_identification();
914:
915: /* Put the connection into non-blocking mode. */
916: packet_set_nonblocking();
917:
918: /* key exchange */
919: /* authenticate user */
1.59 markus 920: if (compat20) {
921: ssh_kex2(host, hostaddr);
1.120 markus 922: ssh_userauth2(local_user, server_user, host, sensitive);
1.59 markus 923: } else {
924: ssh_kex(host, hostaddr);
1.120 markus 925: ssh_userauth1(local_user, server_user, host, sensitive);
1.59 markus 926: }
1.182 markus 927: xfree(local_user);
1.97 markus 928: }
929:
930: void
931: ssh_put_password(char *password)
932: {
933: int size;
934: char *padded;
935:
1.99 deraadt 936: if (datafellows & SSH_BUG_PASSWORDPAD) {
1.107 markus 937: packet_put_cstring(password);
1.99 deraadt 938: return;
939: }
1.97 markus 940: size = roundup(strlen(password) + 1, 32);
1.179 djm 941: padded = xcalloc(1, size);
1.97 markus 942: strlcpy(padded, password, size);
943: packet_put_string(padded, size);
944: memset(padded, 0, size);
945: xfree(padded);
1.132 markus 946: }
947:
948: static int
949: show_key_from_file(const char *file, const char *host, int keytype)
950: {
951: Key *found;
952: char *fp;
953: int line, ret;
954:
955: found = key_new(keytype);
956: if ((ret = lookup_key_in_hostfile_by_type(file, host,
957: keytype, found, &line))) {
958: fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
1.138 itojun 959: logit("WARNING: %s key found for host %s\n"
1.133 markus 960: "in %s:%d\n"
1.132 markus 961: "%s key fingerprint %s.",
962: key_type(found), host, file, line,
963: key_type(found), fp);
964: xfree(fp);
965: }
966: key_free(found);
967: return (ret);
968: }
969:
970: /* print all known host keys for a given host, but skip keys of given type */
971: static int
972: show_other_keys(const char *host, Key *key)
973: {
974: int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1};
975: int i, found = 0;
976:
977: for (i = 0; type[i] != -1; i++) {
978: if (type[i] == key->type)
979: continue;
980: if (type[i] != KEY_RSA1 &&
981: show_key_from_file(options.user_hostfile2, host, type[i])) {
982: found = 1;
983: continue;
984: }
985: if (type[i] != KEY_RSA1 &&
986: show_key_from_file(options.system_hostfile2, host, type[i])) {
987: found = 1;
988: continue;
989: }
990: if (show_key_from_file(options.user_hostfile, host, type[i])) {
991: found = 1;
992: continue;
993: }
994: if (show_key_from_file(options.system_hostfile, host, type[i])) {
995: found = 1;
996: continue;
997: }
998: debug2("no key of type %d for host %s", type[i], host);
999: }
1000: return (found);
1.150 jakob 1001: }
1002:
1003: static void
1004: warn_changed_key(Key *host_key)
1005: {
1006: char *fp;
1.151 jakob 1007: const char *type = key_type(host_key);
1.150 jakob 1008:
1009: fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1010:
1011: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1012: error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1013: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1014: error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1015: error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1016: error("It is also possible that the %s host key has just been changed.", type);
1017: error("The fingerprint for the %s key sent by the remote host is\n%s.",
1018: type, fp);
1019: error("Please contact your system administrator.");
1020:
1021: xfree(fp);
1.171 reyk 1022: }
1023:
1024: /*
1025: * Execute a local command
1026: */
1027: int
1028: ssh_local_cmd(const char *args)
1029: {
1030: char *shell;
1031: pid_t pid;
1032: int status;
1033:
1034: if (!options.permit_local_command ||
1035: args == NULL || !*args)
1036: return (1);
1037:
1038: if ((shell = getenv("SHELL")) == NULL)
1039: shell = _PATH_BSHELL;
1040:
1041: pid = fork();
1042: if (pid == 0) {
1043: debug3("Executing %s -c \"%s\"", shell, args);
1044: execl(shell, shell, "-c", args, (char *)NULL);
1045: error("Couldn't execute %s -c \"%s\": %s",
1046: shell, args, strerror(errno));
1047: _exit(1);
1048: } else if (pid == -1)
1049: fatal("fork failed: %.100s", strerror(errno));
1050: while (waitpid(pid, &status, 0) == -1)
1051: if (errno != EINTR)
1052: fatal("Couldn't wait for child: %s", strerror(errno));
1053:
1054: if (!WIFEXITED(status))
1055: return (1);
1056:
1057: return (WEXITSTATUS(status));
1.1 deraadt 1058: }