Annotation of src/usr.bin/ssh/sshconnect.c, Revision 1.72
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"
1.72 ! markus 11: RCSID("$OpenBSD: sshconnect.c,v 1.71 2000/04/26 21:28:33 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. */
254: memcpy(hostaddr, ai->ai_addr, sizeof(*hostaddr));
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;
1.1 deraadt 298: }
299:
1.59 markus 300: char *
301: chop(char *s)
302: {
303: char *t = s;
304: while (*t) {
305: if(*t == '\n' || *t == '\r') {
306: *t = '\0';
307: return s;
308: }
309: t++;
310: }
311: return s;
312:
313: }
314:
1.43 markus 315: /*
1.39 deraadt 316: * Waits for the server identification string, and sends our own
317: * identification string.
318: */
1.38 markus 319: void
320: ssh_exchange_identification()
1.1 deraadt 321: {
1.38 markus 322: char buf[256], remote_version[256]; /* must be same size! */
1.64 markus 323: int remote_major, remote_minor, i, mismatch;
1.38 markus 324: int connection_in = packet_get_connection_in();
325: int connection_out = packet_get_connection_out();
326:
327: /* Read other side\'s version identification. */
328: for (i = 0; i < sizeof(buf) - 1; i++) {
1.56 markus 329: int len = read(connection_in, &buf[i], 1);
330: if (len < 0)
1.38 markus 331: fatal("ssh_exchange_identification: read: %.100s", strerror(errno));
1.56 markus 332: if (len != 1)
333: fatal("ssh_exchange_identification: Connection closed by remote host");
1.38 markus 334: if (buf[i] == '\r') {
335: buf[i] = '\n';
336: buf[i + 1] = 0;
1.59 markus 337: continue; /**XXX wait for \n */
1.38 markus 338: }
339: if (buf[i] == '\n') {
340: buf[i + 1] = 0;
341: break;
342: }
343: }
344: buf[sizeof(buf) - 1] = 0;
1.59 markus 345: server_version_string = xstrdup(buf);
1.38 markus 346:
1.40 markus 347: /*
348: * Check that the versions match. In future this might accept
349: * several versions and set appropriate flags to handle them.
350: */
1.59 markus 351: if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
352: &remote_major, &remote_minor, remote_version) != 3)
1.38 markus 353: fatal("Bad remote protocol version identification: '%.100s'", buf);
354: debug("Remote protocol version %d.%d, remote software version %.100s",
355: remote_major, remote_minor, remote_version);
356:
1.59 markus 357: compat_datafellows(remote_version);
1.64 markus 358: mismatch = 0;
1.59 markus 359:
1.64 markus 360: switch(remote_major) {
361: case 1:
362: if (remote_minor == 99 &&
363: (options.protocol & SSH_PROTO_2) &&
364: !(options.protocol & SSH_PROTO_1_PREFERRED)) {
365: enable_compat20();
366: break;
367: }
368: if (!(options.protocol & SSH_PROTO_1)) {
369: mismatch = 1;
370: break;
371: }
372: if (remote_minor < 3) {
373: fatal("Remote machine has too old SSH software version.");
374: } else if (remote_minor == 3) {
375: /* We speak 1.3, too. */
376: enable_compat13();
377: if (options.forward_agent) {
378: log("Agent forwarding disabled for protocol 1.3");
379: options.forward_agent = 0;
380: }
381: }
382: break;
383: case 2:
384: if (options.protocol & SSH_PROTO_2) {
385: enable_compat20();
386: break;
1.38 markus 387: }
1.64 markus 388: /* FALLTHROUGH */
1.68 markus 389: default:
1.64 markus 390: mismatch = 1;
391: break;
1.38 markus 392: }
1.64 markus 393: if (mismatch)
1.38 markus 394: fatal("Protocol major versions differ: %d vs. %d",
1.64 markus 395: (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
396: remote_major);
1.70 markus 397: if (compat20)
398: packet_set_ssh2_format();
1.38 markus 399: /* Send our own protocol version identification. */
400: snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
1.64 markus 401: compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
1.65 markus 402: compat20 ? PROTOCOL_MINOR_2 : PROTOCOL_MINOR_1,
1.59 markus 403: SSH_VERSION);
1.45 deraadt 404: if (atomicio(write, connection_out, buf, strlen(buf)) != strlen(buf))
1.38 markus 405: fatal("write: %.100s", strerror(errno));
1.59 markus 406: client_version_string = xstrdup(buf);
407: chop(client_version_string);
408: chop(server_version_string);
409: debug("Local version string %.100s", client_version_string);
1.1 deraadt 410: }
411:
1.38 markus 412: int
413: read_yes_or_no(const char *prompt, int defval)
1.1 deraadt 414: {
1.38 markus 415: char buf[1024];
416: FILE *f;
417: int retval = -1;
418:
419: if (isatty(0))
420: f = stdin;
421: else
422: f = fopen("/dev/tty", "rw");
423:
424: if (f == NULL)
425: return 0;
426:
427: fflush(stdout);
428:
429: while (1) {
430: fprintf(stderr, "%s", prompt);
431: if (fgets(buf, sizeof(buf), f) == NULL) {
432: /* Print a newline (the prompt probably didn\'t have one). */
433: fprintf(stderr, "\n");
434: strlcpy(buf, "no", sizeof buf);
435: }
436: /* Remove newline from response. */
437: if (strchr(buf, '\n'))
438: *strchr(buf, '\n') = 0;
439:
440: if (buf[0] == 0)
441: retval = defval;
442: if (strcmp(buf, "yes") == 0)
443: retval = 1;
444: if (strcmp(buf, "no") == 0)
445: retval = 0;
446:
447: if (retval != -1) {
448: if (f != stdin)
449: fclose(f);
450: return retval;
451: }
1.1 deraadt 452: }
453: }
454:
1.39 deraadt 455: /*
1.46 markus 456: * check whether the supplied host key is valid, return only if ok.
1.39 deraadt 457: */
1.46 markus 458:
1.38 markus 459: void
1.70 markus 460: check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key,
461: const char *user_hostfile, const char *system_hostfile)
1.1 deraadt 462: {
1.58 markus 463: Key *file_key;
1.72 ! markus 464: char *type = key_type(host_key);
1.46 markus 465: char *ip = NULL;
1.38 markus 466: char hostline[1000], *hostp;
467: HostStatus host_status;
468: HostStatus ip_status;
1.49 markus 469: int local = 0, host_ip_differ = 0;
470: char ntop[NI_MAXHOST];
471:
472: /*
473: * Force accepting of the host key for loopback/localhost. The
474: * problem is that if the home directory is NFS-mounted to multiple
475: * machines, localhost will refer to a different machine in each of
476: * them, and the user will get bogus HOST_CHANGED warnings. This
477: * essentially disables host authentication for localhost; however,
478: * this is probably not a real problem.
479: */
1.70 markus 480: /** hostaddr == 0! */
1.49 markus 481: switch (hostaddr->sa_family) {
482: case AF_INET:
483: local = (ntohl(((struct sockaddr_in *)hostaddr)->sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
484: break;
485: case AF_INET6:
486: local = IN6_IS_ADDR_LOOPBACK(&(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
487: break;
488: default:
489: local = 0;
490: break;
491: }
492: if (local) {
493: debug("Forcing accepting of host key for loopback/localhost.");
494: return;
495: }
1.42 markus 496:
497: /*
1.44 markus 498: * Turn off check_host_ip for proxy connects, since
1.42 markus 499: * we don't have the remote ip-address
500: */
501: if (options.proxy_command != NULL && options.check_host_ip)
502: options.check_host_ip = 0;
1.38 markus 503:
1.49 markus 504: if (options.check_host_ip) {
505: if (getnameinfo(hostaddr, hostaddr->sa_len, ntop, sizeof(ntop),
506: NULL, 0, NI_NUMERICHOST) != 0)
507: fatal("check_host_key: getnameinfo failed");
508: ip = xstrdup(ntop);
509: }
1.38 markus 510:
1.46 markus 511: /*
512: * Store the host key from the known host file in here so that we can
513: * compare it with the key for the IP address.
514: */
1.58 markus 515: file_key = key_new(host_key->type);
1.38 markus 516:
1.40 markus 517: /*
518: * Check if the host key is present in the user\'s list of known
519: * hosts or in the systemwide list.
520: */
1.70 markus 521: host_status = check_host_in_hostfile(user_hostfile, host, host_key, file_key);
1.38 markus 522: if (host_status == HOST_NEW)
1.70 markus 523: host_status = check_host_in_hostfile(system_hostfile, host, host_key, file_key);
1.40 markus 524: /*
525: * Also perform check for the ip address, skip the check if we are
526: * localhost or the hostname was an ip address to begin with
527: */
1.38 markus 528: if (options.check_host_ip && !local && strcmp(host, ip)) {
1.58 markus 529: Key *ip_key = key_new(host_key->type);
1.70 markus 530: ip_status = check_host_in_hostfile(user_hostfile, ip, host_key, ip_key);
1.38 markus 531:
532: if (ip_status == HOST_NEW)
1.70 markus 533: ip_status = check_host_in_hostfile(system_hostfile, ip, host_key, ip_key);
1.38 markus 534: if (host_status == HOST_CHANGED &&
1.58 markus 535: (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
1.38 markus 536: host_ip_differ = 1;
537:
1.58 markus 538: key_free(ip_key);
1.38 markus 539: } else
540: ip_status = host_status;
541:
1.58 markus 542: key_free(file_key);
1.38 markus 543:
544: switch (host_status) {
545: case HOST_OK:
546: /* The host is known and the key matches. */
1.72 ! markus 547: debug("Host '%.200s' is known and matches the %s host key.",
! 548: host, type);
1.38 markus 549: if (options.check_host_ip) {
550: if (ip_status == HOST_NEW) {
1.70 markus 551: if (!add_host_to_hostfile(user_hostfile, ip, host_key))
1.72 ! markus 552: log("Failed to add the %s host key for IP address '%.30s' to the list of known hosts (%.30s).",
! 553: type, ip, user_hostfile);
1.38 markus 554: else
1.72 ! markus 555: log("Warning: Permanently added the %s host key for IP address '%.30s' to the list of known hosts.",
! 556: type, ip);
1.38 markus 557: } else if (ip_status != HOST_OK)
1.72 ! markus 558: log("Warning: the %s host key for '%.200s' differs from the key for the IP address '%.30s'",
! 559: type, host, ip);
1.38 markus 560: }
561: break;
562: case HOST_NEW:
563: /* The host is new. */
564: if (options.strict_host_key_checking == 1) {
565: /* User has requested strict host key checking. We will not add the host key
566: automatically. The only alternative left is to abort. */
1.72 ! markus 567: fatal("No %s host key is known for %.200s and you have requested strict checking.", type, host);
1.38 markus 568: } else if (options.strict_host_key_checking == 2) {
569: /* The default */
570: char prompt[1024];
1.58 markus 571: char *fp = key_fingerprint(host_key);
1.38 markus 572: snprintf(prompt, sizeof(prompt),
1.45 deraadt 573: "The authenticity of host '%.200s' can't be established.\n"
1.72 ! markus 574: "%s key fingerprint is %s.\n"
1.45 deraadt 575: "Are you sure you want to continue connecting (yes/no)? ",
1.72 ! markus 576: host, type, fp);
1.38 markus 577: if (!read_yes_or_no(prompt, -1))
578: fatal("Aborted by user!\n");
579: }
580: if (options.check_host_ip && ip_status == HOST_NEW && strcmp(host, ip)) {
581: snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
582: hostp = hostline;
583: } else
584: hostp = host;
585:
586: /* If not in strict mode, add the key automatically to the local known_hosts file. */
1.70 markus 587: if (!add_host_to_hostfile(user_hostfile, hostp, host_key))
1.38 markus 588: log("Failed to add the host to the list of known hosts (%.500s).",
1.70 markus 589: user_hostfile);
1.38 markus 590: else
1.72 ! markus 591: log("Warning: Permanently added '%.200s' (%s) to the list of known hosts.",
! 592: hostp, type);
1.38 markus 593: break;
594: case HOST_CHANGED:
595: if (options.check_host_ip && host_ip_differ) {
596: char *msg;
597: if (ip_status == HOST_NEW)
598: msg = "is unknown";
599: else if (ip_status == HOST_OK)
600: msg = "is unchanged";
601: else
602: msg = "has a different value";
603: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
604: error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
605: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1.72 ! markus 606: error("The %s host key for %s has changed,", type, host);
1.38 markus 607: error("and the key for the according IP address %s", ip);
608: error("%s. This could either mean that", msg);
609: error("DNS SPOOFING is happening or the IP address for the host");
610: error("and its host key have changed at the same time");
611: }
612: /* The host key has changed. */
613: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1.47 markus 614: error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1.38 markus 615: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
616: error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
617: error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1.72 ! markus 618: error("It is also possible that the %s host key has just been changed.", type);
1.38 markus 619: error("Please contact your system administrator.");
620: error("Add correct host key in %.100s to get rid of this message.",
1.70 markus 621: user_hostfile);
1.38 markus 622:
1.40 markus 623: /*
624: * If strict host key checking is in use, the user will have
625: * to edit the key manually and we can only abort.
626: */
1.38 markus 627: if (options.strict_host_key_checking)
1.72 ! markus 628: fatal("%s host key for %.200s has changed and you have requested strict checking.", type, host);
1.38 markus 629:
1.40 markus 630: /*
631: * If strict host key checking has not been requested, allow
632: * the connection but without password authentication or
633: * agent forwarding.
634: */
1.38 markus 635: if (options.password_authentication) {
636: error("Password authentication is disabled to avoid trojan horses.");
637: options.password_authentication = 0;
638: }
639: if (options.forward_agent) {
640: error("Agent forwarding is disabled to avoid trojan horses.");
641: options.forward_agent = 0;
642: }
1.40 markus 643: /*
644: * XXX Should permit the user to change to use the new id.
645: * This could be done by converting the host key to an
646: * identifying sentence, tell that the host identifies itself
647: * by that sentence, and ask the user if he/she whishes to
648: * accept the authentication.
649: */
1.38 markus 650: break;
651: }
652: if (options.check_host_ip)
653: xfree(ip);
1.51 markus 654: }
1.70 markus 655:
1.51 markus 656: /*
657: * Starts a dialog with the server, and authenticates the current user on the
658: * server. This does not need any extra privileges. The basic connection
659: * to the server must already have been established before this is called.
660: * If login fails, this function prints an error and never returns.
661: * This function does not require super-user privileges.
662: */
663: void
664: ssh_login(int host_key_valid, RSA *own_host_key, const char *orighost,
665: struct sockaddr *hostaddr, uid_t original_real_uid)
666: {
1.70 markus 667: struct passwd *pw;
1.51 markus 668: char *host, *cp;
1.70 markus 669: char *server_user, *local_user;
670:
671: /* Get local user name. Use it as server user if no user name was given. */
672: pw = getpwuid(original_real_uid);
673: if (!pw)
674: fatal("User id %d not found from user database.", original_real_uid);
675: local_user = xstrdup(pw->pw_name);
676: server_user = options.user ? options.user : local_user;
1.51 markus 677:
678: /* Convert the user-supplied hostname into all lowercase. */
679: host = xstrdup(orighost);
680: for (cp = host; *cp; cp++)
681: if (isupper(*cp))
682: *cp = tolower(*cp);
683:
684: /* Exchange protocol version identification strings with the server. */
685: ssh_exchange_identification();
686:
687: /* Put the connection into non-blocking mode. */
688: packet_set_nonblocking();
689:
690: /* key exchange */
691: /* authenticate user */
1.59 markus 692: if (compat20) {
693: ssh_kex2(host, hostaddr);
1.70 markus 694: ssh_userauth2(server_user, host);
1.59 markus 695: } else {
696: ssh_kex(host, hostaddr);
1.70 markus 697: ssh_userauth(local_user, server_user, host, host_key_valid, own_host_key);
1.59 markus 698: }
1.1 deraadt 699: }