Annotation of src/usr.bin/ssh/sshconnect.c, Revision 1.76
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: * Created: Sat Mar 18 22:15:47 1995 ylo
6: * Code to connect to a remote host, and to perform the client side of the
7: * login (authentication) dialog.
8: */
1.1 deraadt 9:
10: #include "includes.h"
1.76 ! markus 11: RCSID("$OpenBSD: sshconnect.c,v 1.75 2000/06/17 19:24:34 markus Exp $");
1.1 deraadt 12:
1.66 markus 13: #include <openssl/bn.h>
1.71 markus 14: #include <openssl/dsa.h>
15: #include <openssl/rsa.h>
16:
1.1 deraadt 17: #include "xmalloc.h"
18: #include "rsa.h"
19: #include "ssh.h"
1.59 markus 20: #include "buffer.h"
1.1 deraadt 21: #include "packet.h"
22: #include "uidswap.h"
1.21 markus 23: #include "compat.h"
1.27 markus 24: #include "readconf.h"
1.58 markus 25: #include "key.h"
1.71 markus 26: #include "sshconnect.h"
1.58 markus 27: #include "hostfile.h"
1.51 markus 28:
1.70 markus 29: char *client_version_string = NULL;
30: char *server_version_string = NULL;
1.59 markus 31:
1.43 markus 32: extern Options options;
1.50 markus 33: extern char *__progname;
1.43 markus 34:
1.39 deraadt 35: /*
36: * Connect to the given ssh server using a proxy command.
37: */
1.3 provos 38: int
1.41 markus 39: ssh_proxy_connect(const char *host, u_short port, uid_t original_real_uid,
1.3 provos 40: const char *proxy_command)
1.1 deraadt 41: {
1.38 markus 42: Buffer command;
43: const char *cp;
44: char *command_string;
45: int pin[2], pout[2];
1.69 deraadt 46: pid_t pid;
1.49 markus 47: char strport[NI_MAXSERV];
1.38 markus 48:
49: /* Convert the port number into a string. */
1.49 markus 50: snprintf(strport, sizeof strport, "%hu", port);
1.38 markus 51:
52: /* Build the final command string in the buffer by making the
53: appropriate substitutions to the given proxy command. */
54: buffer_init(&command);
55: for (cp = proxy_command; *cp; cp++) {
56: if (cp[0] == '%' && cp[1] == '%') {
57: buffer_append(&command, "%", 1);
58: cp++;
59: continue;
60: }
61: if (cp[0] == '%' && cp[1] == 'h') {
62: buffer_append(&command, host, strlen(host));
63: cp++;
64: continue;
65: }
66: if (cp[0] == '%' && cp[1] == 'p') {
1.49 markus 67: buffer_append(&command, strport, strlen(strport));
1.38 markus 68: cp++;
69: continue;
70: }
71: buffer_append(&command, cp, 1);
72: }
73: buffer_append(&command, "\0", 1);
74:
75: /* Get the final command string. */
76: command_string = buffer_ptr(&command);
77:
78: /* Create pipes for communicating with the proxy. */
79: if (pipe(pin) < 0 || pipe(pout) < 0)
80: fatal("Could not create pipes to communicate with the proxy: %.100s",
81: strerror(errno));
82:
83: debug("Executing proxy command: %.500s", command_string);
84:
85: /* Fork and execute the proxy command. */
86: if ((pid = fork()) == 0) {
87: char *argv[10];
88:
89: /* Child. Permanently give up superuser privileges. */
90: permanently_set_uid(original_real_uid);
91:
92: /* Redirect stdin and stdout. */
93: close(pin[1]);
94: if (pin[0] != 0) {
95: if (dup2(pin[0], 0) < 0)
96: perror("dup2 stdin");
97: close(pin[0]);
98: }
99: close(pout[0]);
100: if (dup2(pout[1], 1) < 0)
101: perror("dup2 stdout");
102: /* Cannot be 1 because pin allocated two descriptors. */
103: close(pout[1]);
104:
105: /* Stderr is left as it is so that error messages get
106: printed on the user's terminal. */
107: argv[0] = "/bin/sh";
108: argv[1] = "-c";
109: argv[2] = command_string;
110: argv[3] = NULL;
111:
112: /* Execute the proxy command. Note that we gave up any
113: extra privileges above. */
114: execv("/bin/sh", argv);
115: perror("/bin/sh");
116: exit(1);
117: }
118: /* Parent. */
119: if (pid < 0)
120: fatal("fork failed: %.100s", strerror(errno));
121:
122: /* Close child side of the descriptors. */
123: close(pin[0]);
124: close(pout[1]);
125:
126: /* Free the command name. */
127: buffer_free(&command);
128:
129: /* Set the connection file descriptors. */
130: packet_set_connection(pout[0], pin[1]);
1.1 deraadt 131:
1.38 markus 132: return 1;
1.1 deraadt 133: }
134:
1.39 deraadt 135: /*
136: * Creates a (possibly privileged) socket for use as the ssh connection.
137: */
1.38 markus 138: int
1.49 markus 139: ssh_create_socket(uid_t original_real_uid, int privileged, int family)
1.1 deraadt 140: {
1.38 markus 141: int sock;
1.1 deraadt 142:
1.40 markus 143: /*
144: * If we are running as root and want to connect to a privileged
145: * port, bind our own socket to a privileged port.
146: */
1.38 markus 147: if (privileged) {
148: int p = IPPORT_RESERVED - 1;
1.49 markus 149: sock = rresvport_af(&p, family);
1.38 markus 150: if (sock < 0)
1.55 markus 151: error("rresvport: af=%d %.100s", family, strerror(errno));
152: else
153: debug("Allocated local port %d.", p);
1.38 markus 154: } else {
1.46 markus 155: /*
156: * Just create an ordinary socket on arbitrary port. We use
157: * the user's uid to create the socket.
158: */
1.38 markus 159: temporarily_use_uid(original_real_uid);
1.49 markus 160: sock = socket(family, SOCK_STREAM, 0);
1.38 markus 161: if (sock < 0)
1.49 markus 162: error("socket: %.100s", strerror(errno));
1.38 markus 163: restore_uid();
164: }
165: return sock;
1.1 deraadt 166: }
167:
1.39 deraadt 168: /*
1.49 markus 169: * Opens a TCP/IP connection to the remote server on the given host.
170: * The address of the remote host will be returned in hostaddr.
171: * If port is 0, the default port will be used. If anonymous is zero,
1.39 deraadt 172: * a privileged port will be allocated to make the connection.
173: * This requires super-user privileges if anonymous is false.
174: * Connection_attempts specifies the maximum number of tries (one per
175: * second). If proxy_command is non-NULL, it specifies the command (with %h
176: * and %p substituted for host and port, respectively) to use to contact
177: * the daemon.
178: */
1.38 markus 179: int
1.49 markus 180: ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
1.41 markus 181: u_short port, int connection_attempts,
1.38 markus 182: int anonymous, uid_t original_real_uid,
183: const char *proxy_command)
1.1 deraadt 184: {
1.49 markus 185: int sock = -1, attempt;
1.38 markus 186: struct servent *sp;
1.49 markus 187: struct addrinfo hints, *ai, *aitop;
188: char ntop[NI_MAXHOST], strport[NI_MAXSERV];
189: int gaierr;
1.38 markus 190: struct linger linger;
191:
192: debug("ssh_connect: getuid %d geteuid %d anon %d",
193: (int) getuid(), (int) geteuid(), anonymous);
194:
195: /* Get default port if port has not been set. */
196: if (port == 0) {
197: sp = getservbyname(SSH_SERVICE_NAME, "tcp");
198: if (sp)
199: port = ntohs(sp->s_port);
200: else
201: port = SSH_DEFAULT_PORT;
202: }
203: /* If a proxy command is given, connect using it. */
204: if (proxy_command != NULL)
205: return ssh_proxy_connect(host, port, original_real_uid, proxy_command);
206:
207: /* No proxy command. */
208:
1.49 markus 209: memset(&hints, 0, sizeof(hints));
210: hints.ai_family = IPv4or6;
211: hints.ai_socktype = SOCK_STREAM;
212: snprintf(strport, sizeof strport, "%d", port);
213: if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
1.50 markus 214: fatal("%s: %.100s: %s", __progname, host,
215: gai_strerror(gaierr));
1.38 markus 216:
1.46 markus 217: /*
218: * Try to connect several times. On some machines, the first time
219: * will sometimes fail. In general socket code appears to behave
220: * quite magically on many machines.
221: */
1.38 markus 222: for (attempt = 0; attempt < connection_attempts; attempt++) {
223: if (attempt > 0)
224: debug("Trying again...");
225:
1.49 markus 226: /* Loop through addresses for this host, and try each one in
1.68 markus 227: sequence until the connection succeeds. */
1.49 markus 228: for (ai = aitop; ai; ai = ai->ai_next) {
229: if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
230: continue;
231: if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
232: ntop, sizeof(ntop), strport, sizeof(strport),
233: NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
234: error("ssh_connect: getnameinfo failed");
235: continue;
236: }
237: debug("Connecting to %.200s [%.100s] port %s.",
238: host, ntop, strport);
239:
240: /* Create a socket for connecting. */
1.68 markus 241: sock = ssh_create_socket(original_real_uid,
1.49 markus 242: !anonymous && geteuid() == 0 && port < IPPORT_RESERVED,
243: ai->ai_family);
244: if (sock < 0)
245: continue;
246:
247: /* Connect to the host. We use the user's uid in the
248: * hope that it will help with tcp_wrappers showing
249: * the remote uid as root.
1.40 markus 250: */
1.38 markus 251: temporarily_use_uid(original_real_uid);
1.49 markus 252: if (connect(sock, ai->ai_addr, ai->ai_addrlen) >= 0) {
253: /* Successful connection. */
1.74 markus 254: memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
1.38 markus 255: restore_uid();
256: break;
1.49 markus 257: } else {
1.38 markus 258: debug("connect: %.100s", strerror(errno));
259: restore_uid();
1.40 markus 260: /*
261: * Close the failed socket; there appear to
262: * be some problems when reusing a socket for
263: * which connect() has already returned an
264: * error.
265: */
1.38 markus 266: shutdown(sock, SHUT_RDWR);
267: close(sock);
268: }
269: }
1.49 markus 270: if (ai)
271: break; /* Successful connection. */
1.1 deraadt 272:
1.38 markus 273: /* Sleep a moment before retrying. */
274: sleep(1);
275: }
1.49 markus 276:
277: freeaddrinfo(aitop);
278:
1.38 markus 279: /* Return failure if we didn't get a successful connection. */
280: if (attempt >= connection_attempts)
281: return 0;
282:
283: debug("Connection established.");
284:
1.40 markus 285: /*
286: * Set socket options. We would like the socket to disappear as soon
287: * as it has been closed for whatever reason.
288: */
289: /* setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1.38 markus 290: linger.l_onoff = 1;
291: linger.l_linger = 5;
292: setsockopt(sock, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
293:
294: /* Set the connection. */
295: packet_set_connection(sock, sock);
1.1 deraadt 296:
1.38 markus 297: return 1;
1.59 markus 298: }
299:
1.43 markus 300: /*
1.39 deraadt 301: * Waits for the server identification string, and sends our own
302: * identification string.
303: */
1.38 markus 304: void
305: ssh_exchange_identification()
1.1 deraadt 306: {
1.38 markus 307: char buf[256], remote_version[256]; /* must be same size! */
1.64 markus 308: int remote_major, remote_minor, i, mismatch;
1.38 markus 309: int connection_in = packet_get_connection_in();
310: int connection_out = packet_get_connection_out();
311:
312: /* Read other side\'s version identification. */
1.75 markus 313: for (;;) {
314: for (i = 0; i < sizeof(buf) - 1; i++) {
1.76 ! markus 315: int len = atomicio(read, connection_in, &buf[i], 1);
1.75 markus 316: if (len < 0)
317: fatal("ssh_exchange_identification: read: %.100s", strerror(errno));
318: if (len != 1)
319: fatal("ssh_exchange_identification: Connection closed by remote host");
320: if (buf[i] == '\r') {
321: buf[i] = '\n';
322: buf[i + 1] = 0;
323: continue; /**XXX wait for \n */
324: }
325: if (buf[i] == '\n') {
326: buf[i + 1] = 0;
327: break;
328: }
1.38 markus 329: }
1.75 markus 330: buf[sizeof(buf) - 1] = 0;
1.76 ! markus 331: if (strncmp(buf, "SSH-", 4) == 0)
1.38 markus 332: break;
1.75 markus 333: debug("ssh_exchange_identification: %s", buf);
1.38 markus 334: }
1.59 markus 335: server_version_string = xstrdup(buf);
1.38 markus 336:
1.40 markus 337: /*
338: * Check that the versions match. In future this might accept
339: * several versions and set appropriate flags to handle them.
340: */
1.59 markus 341: if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
342: &remote_major, &remote_minor, remote_version) != 3)
1.38 markus 343: fatal("Bad remote protocol version identification: '%.100s'", buf);
344: debug("Remote protocol version %d.%d, remote software version %.100s",
345: remote_major, remote_minor, remote_version);
346:
1.59 markus 347: compat_datafellows(remote_version);
1.64 markus 348: mismatch = 0;
1.59 markus 349:
1.64 markus 350: switch(remote_major) {
351: case 1:
352: if (remote_minor == 99 &&
353: (options.protocol & SSH_PROTO_2) &&
354: !(options.protocol & SSH_PROTO_1_PREFERRED)) {
355: enable_compat20();
356: break;
357: }
358: if (!(options.protocol & SSH_PROTO_1)) {
359: mismatch = 1;
360: break;
361: }
362: if (remote_minor < 3) {
363: fatal("Remote machine has too old SSH software version.");
364: } else if (remote_minor == 3) {
365: /* We speak 1.3, too. */
366: enable_compat13();
367: if (options.forward_agent) {
368: log("Agent forwarding disabled for protocol 1.3");
369: options.forward_agent = 0;
370: }
371: }
372: break;
373: case 2:
374: if (options.protocol & SSH_PROTO_2) {
375: enable_compat20();
376: break;
1.38 markus 377: }
1.64 markus 378: /* FALLTHROUGH */
1.68 markus 379: default:
1.64 markus 380: mismatch = 1;
381: break;
1.38 markus 382: }
1.64 markus 383: if (mismatch)
1.38 markus 384: fatal("Protocol major versions differ: %d vs. %d",
1.64 markus 385: (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
386: remote_major);
1.70 markus 387: if (compat20)
388: packet_set_ssh2_format();
1.38 markus 389: /* Send our own protocol version identification. */
390: snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
1.64 markus 391: compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
1.65 markus 392: compat20 ? PROTOCOL_MINOR_2 : PROTOCOL_MINOR_1,
1.59 markus 393: SSH_VERSION);
1.45 deraadt 394: if (atomicio(write, connection_out, buf, strlen(buf)) != strlen(buf))
1.38 markus 395: fatal("write: %.100s", strerror(errno));
1.59 markus 396: client_version_string = xstrdup(buf);
397: chop(client_version_string);
398: chop(server_version_string);
399: debug("Local version string %.100s", client_version_string);
1.1 deraadt 400: }
401:
1.38 markus 402: int
403: read_yes_or_no(const char *prompt, int defval)
1.1 deraadt 404: {
1.38 markus 405: char buf[1024];
406: FILE *f;
407: int retval = -1;
408:
409: if (isatty(0))
410: f = stdin;
411: else
412: f = fopen("/dev/tty", "rw");
413:
414: if (f == NULL)
415: return 0;
416:
417: fflush(stdout);
418:
419: while (1) {
420: fprintf(stderr, "%s", prompt);
421: if (fgets(buf, sizeof(buf), f) == NULL) {
422: /* Print a newline (the prompt probably didn\'t have one). */
423: fprintf(stderr, "\n");
424: strlcpy(buf, "no", sizeof buf);
425: }
426: /* Remove newline from response. */
427: if (strchr(buf, '\n'))
428: *strchr(buf, '\n') = 0;
429:
430: if (buf[0] == 0)
431: retval = defval;
432: if (strcmp(buf, "yes") == 0)
433: retval = 1;
434: if (strcmp(buf, "no") == 0)
435: retval = 0;
436:
437: if (retval != -1) {
438: if (f != stdin)
439: fclose(f);
440: return retval;
441: }
1.1 deraadt 442: }
443: }
444:
1.39 deraadt 445: /*
1.46 markus 446: * check whether the supplied host key is valid, return only if ok.
1.39 deraadt 447: */
1.46 markus 448:
1.38 markus 449: void
1.70 markus 450: check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key,
451: const char *user_hostfile, const char *system_hostfile)
1.1 deraadt 452: {
1.58 markus 453: Key *file_key;
1.72 markus 454: char *type = key_type(host_key);
1.46 markus 455: char *ip = NULL;
1.38 markus 456: char hostline[1000], *hostp;
457: HostStatus host_status;
458: HostStatus ip_status;
1.49 markus 459: int local = 0, host_ip_differ = 0;
460: char ntop[NI_MAXHOST];
461:
462: /*
463: * Force accepting of the host key for loopback/localhost. The
464: * problem is that if the home directory is NFS-mounted to multiple
465: * machines, localhost will refer to a different machine in each of
466: * them, and the user will get bogus HOST_CHANGED warnings. This
467: * essentially disables host authentication for localhost; however,
468: * this is probably not a real problem.
469: */
1.70 markus 470: /** hostaddr == 0! */
1.49 markus 471: switch (hostaddr->sa_family) {
472: case AF_INET:
473: local = (ntohl(((struct sockaddr_in *)hostaddr)->sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
474: break;
475: case AF_INET6:
476: local = IN6_IS_ADDR_LOOPBACK(&(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
477: break;
478: default:
479: local = 0;
480: break;
481: }
482: if (local) {
483: debug("Forcing accepting of host key for loopback/localhost.");
484: return;
485: }
1.42 markus 486:
487: /*
1.44 markus 488: * Turn off check_host_ip for proxy connects, since
1.42 markus 489: * we don't have the remote ip-address
490: */
491: if (options.proxy_command != NULL && options.check_host_ip)
492: options.check_host_ip = 0;
1.38 markus 493:
1.49 markus 494: if (options.check_host_ip) {
495: if (getnameinfo(hostaddr, hostaddr->sa_len, ntop, sizeof(ntop),
496: NULL, 0, NI_NUMERICHOST) != 0)
497: fatal("check_host_key: getnameinfo failed");
498: ip = xstrdup(ntop);
499: }
1.38 markus 500:
1.46 markus 501: /*
502: * Store the host key from the known host file in here so that we can
503: * compare it with the key for the IP address.
504: */
1.58 markus 505: file_key = key_new(host_key->type);
1.38 markus 506:
1.40 markus 507: /*
508: * Check if the host key is present in the user\'s list of known
509: * hosts or in the systemwide list.
510: */
1.70 markus 511: host_status = check_host_in_hostfile(user_hostfile, host, host_key, file_key);
1.38 markus 512: if (host_status == HOST_NEW)
1.70 markus 513: host_status = check_host_in_hostfile(system_hostfile, host, host_key, file_key);
1.40 markus 514: /*
515: * Also perform check for the ip address, skip the check if we are
516: * localhost or the hostname was an ip address to begin with
517: */
1.38 markus 518: if (options.check_host_ip && !local && strcmp(host, ip)) {
1.58 markus 519: Key *ip_key = key_new(host_key->type);
1.70 markus 520: ip_status = check_host_in_hostfile(user_hostfile, ip, host_key, ip_key);
1.38 markus 521:
522: if (ip_status == HOST_NEW)
1.70 markus 523: ip_status = check_host_in_hostfile(system_hostfile, ip, host_key, ip_key);
1.38 markus 524: if (host_status == HOST_CHANGED &&
1.58 markus 525: (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
1.38 markus 526: host_ip_differ = 1;
527:
1.58 markus 528: key_free(ip_key);
1.38 markus 529: } else
530: ip_status = host_status;
531:
1.58 markus 532: key_free(file_key);
1.38 markus 533:
534: switch (host_status) {
535: case HOST_OK:
536: /* The host is known and the key matches. */
1.72 markus 537: debug("Host '%.200s' is known and matches the %s host key.",
538: host, type);
1.38 markus 539: if (options.check_host_ip) {
540: if (ip_status == HOST_NEW) {
1.70 markus 541: if (!add_host_to_hostfile(user_hostfile, ip, host_key))
1.72 markus 542: log("Failed to add the %s host key for IP address '%.30s' to the list of known hosts (%.30s).",
543: type, ip, user_hostfile);
1.38 markus 544: else
1.72 markus 545: log("Warning: Permanently added the %s host key for IP address '%.30s' to the list of known hosts.",
546: type, ip);
1.38 markus 547: } else if (ip_status != HOST_OK)
1.72 markus 548: log("Warning: the %s host key for '%.200s' differs from the key for the IP address '%.30s'",
549: type, host, ip);
1.38 markus 550: }
551: break;
552: case HOST_NEW:
553: /* The host is new. */
554: if (options.strict_host_key_checking == 1) {
555: /* User has requested strict host key checking. We will not add the host key
556: automatically. The only alternative left is to abort. */
1.72 markus 557: fatal("No %s host key is known for %.200s and you have requested strict checking.", type, host);
1.38 markus 558: } else if (options.strict_host_key_checking == 2) {
559: /* The default */
560: char prompt[1024];
1.58 markus 561: char *fp = key_fingerprint(host_key);
1.38 markus 562: snprintf(prompt, sizeof(prompt),
1.45 deraadt 563: "The authenticity of host '%.200s' can't be established.\n"
1.72 markus 564: "%s key fingerprint is %s.\n"
1.45 deraadt 565: "Are you sure you want to continue connecting (yes/no)? ",
1.72 markus 566: host, type, fp);
1.38 markus 567: if (!read_yes_or_no(prompt, -1))
568: fatal("Aborted by user!\n");
569: }
570: if (options.check_host_ip && ip_status == HOST_NEW && strcmp(host, ip)) {
571: snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
572: hostp = hostline;
573: } else
574: hostp = host;
575:
576: /* If not in strict mode, add the key automatically to the local known_hosts file. */
1.70 markus 577: if (!add_host_to_hostfile(user_hostfile, hostp, host_key))
1.38 markus 578: log("Failed to add the host to the list of known hosts (%.500s).",
1.70 markus 579: user_hostfile);
1.38 markus 580: else
1.72 markus 581: log("Warning: Permanently added '%.200s' (%s) to the list of known hosts.",
582: hostp, type);
1.38 markus 583: break;
584: case HOST_CHANGED:
585: if (options.check_host_ip && host_ip_differ) {
586: char *msg;
587: if (ip_status == HOST_NEW)
588: msg = "is unknown";
589: else if (ip_status == HOST_OK)
590: msg = "is unchanged";
591: else
592: msg = "has a different value";
593: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
594: error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
595: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1.72 markus 596: error("The %s host key for %s has changed,", type, host);
1.38 markus 597: error("and the key for the according IP address %s", ip);
598: error("%s. This could either mean that", msg);
599: error("DNS SPOOFING is happening or the IP address for the host");
600: error("and its host key have changed at the same time");
601: }
602: /* The host key has changed. */
603: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1.47 markus 604: error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1.38 markus 605: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
606: error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
607: error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1.72 markus 608: error("It is also possible that the %s host key has just been changed.", type);
1.38 markus 609: error("Please contact your system administrator.");
610: error("Add correct host key in %.100s to get rid of this message.",
1.70 markus 611: user_hostfile);
1.38 markus 612:
1.40 markus 613: /*
614: * If strict host key checking is in use, the user will have
615: * to edit the key manually and we can only abort.
616: */
1.38 markus 617: if (options.strict_host_key_checking)
1.72 markus 618: fatal("%s host key for %.200s has changed and you have requested strict checking.", type, host);
1.38 markus 619:
1.40 markus 620: /*
621: * If strict host key checking has not been requested, allow
622: * the connection but without password authentication or
623: * agent forwarding.
624: */
1.38 markus 625: if (options.password_authentication) {
626: error("Password authentication is disabled to avoid trojan horses.");
627: options.password_authentication = 0;
628: }
629: if (options.forward_agent) {
630: error("Agent forwarding is disabled to avoid trojan horses.");
631: options.forward_agent = 0;
632: }
1.40 markus 633: /*
634: * XXX Should permit the user to change to use the new id.
635: * This could be done by converting the host key to an
636: * identifying sentence, tell that the host identifies itself
637: * by that sentence, and ask the user if he/she whishes to
638: * accept the authentication.
639: */
1.38 markus 640: break;
641: }
642: if (options.check_host_ip)
643: xfree(ip);
1.51 markus 644: }
1.70 markus 645:
1.51 markus 646: /*
647: * Starts a dialog with the server, and authenticates the current user on the
648: * server. This does not need any extra privileges. The basic connection
649: * to the server must already have been established before this is called.
650: * If login fails, this function prints an error and never returns.
651: * This function does not require super-user privileges.
652: */
653: void
654: ssh_login(int host_key_valid, RSA *own_host_key, const char *orighost,
655: struct sockaddr *hostaddr, uid_t original_real_uid)
656: {
1.70 markus 657: struct passwd *pw;
1.51 markus 658: char *host, *cp;
1.70 markus 659: char *server_user, *local_user;
660:
661: /* Get local user name. Use it as server user if no user name was given. */
662: pw = getpwuid(original_real_uid);
663: if (!pw)
664: fatal("User id %d not found from user database.", original_real_uid);
665: local_user = xstrdup(pw->pw_name);
666: server_user = options.user ? options.user : local_user;
1.51 markus 667:
668: /* Convert the user-supplied hostname into all lowercase. */
669: host = xstrdup(orighost);
670: for (cp = host; *cp; cp++)
671: if (isupper(*cp))
672: *cp = tolower(*cp);
673:
674: /* Exchange protocol version identification strings with the server. */
675: ssh_exchange_identification();
676:
677: /* Put the connection into non-blocking mode. */
678: packet_set_nonblocking();
679:
680: /* key exchange */
681: /* authenticate user */
1.59 markus 682: if (compat20) {
683: ssh_kex2(host, hostaddr);
1.70 markus 684: ssh_userauth2(server_user, host);
1.59 markus 685: } else {
686: ssh_kex(host, hostaddr);
1.70 markus 687: ssh_userauth(local_user, server_user, host, host_key_valid, own_host_key);
1.59 markus 688: }
1.1 deraadt 689: }
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