Annotation of src/usr.bin/ssh/auth2-pubkey.c, Revision 1.86
1.86 ! djm 1: /* $OpenBSD: auth2-pubkey.c,v 1.85 2018/08/28 12:25:53 mestre Exp $ */
1.1 markus 2: /*
3: * Copyright (c) 2000 Markus Friedl. All rights reserved.
4: *
5: * Redistribution and use in source and binary forms, with or without
6: * modification, are permitted provided that the following conditions
7: * are met:
8: * 1. Redistributions of source code must retain the above copyright
9: * notice, this list of conditions and the following disclaimer.
10: * 2. Redistributions in binary form must reproduce the above copyright
11: * notice, this list of conditions and the following disclaimer in the
12: * documentation and/or other materials provided with the distribution.
13: *
14: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24: */
25:
1.10 stevesk 26:
27: #include <sys/types.h>
28: #include <sys/stat.h>
1.13 stevesk 29:
1.31 djm 30: #include <errno.h>
1.16 djm 31: #include <fcntl.h>
1.31 djm 32: #include <paths.h>
1.13 stevesk 33: #include <pwd.h>
1.31 djm 34: #include <signal.h>
1.14 stevesk 35: #include <stdio.h>
1.15 deraadt 36: #include <stdarg.h>
1.20 djm 37: #include <string.h>
38: #include <time.h>
1.17 dtucker 39: #include <unistd.h>
1.44 djm 40: #include <limits.h>
1.1 markus 41:
1.15 deraadt 42: #include "xmalloc.h"
1.8 dtucker 43: #include "ssh.h"
1.1 markus 44: #include "ssh2.h"
45: #include "packet.h"
1.81 markus 46: #include "sshbuf.h"
1.1 markus 47: #include "log.h"
1.41 millert 48: #include "misc.h"
1.1 markus 49: #include "servconf.h"
50: #include "compat.h"
1.64 markus 51: #include "sshkey.h"
1.15 deraadt 52: #include "hostfile.h"
1.1 markus 53: #include "auth.h"
54: #include "pathnames.h"
55: #include "uidswap.h"
56: #include "auth-options.h"
57: #include "canohost.h"
1.15 deraadt 58: #ifdef GSSAPI
59: #include "ssh-gss.h"
60: #endif
1.1 markus 61: #include "monitor_wrap.h"
1.21 djm 62: #include "authfile.h"
1.24 djm 63: #include "match.h"
1.50 djm 64: #include "ssherr.h"
65: #include "channels.h" /* XXX for session.h */
66: #include "session.h" /* XXX for child_set_env(); refactor? */
1.1 markus 67:
68: /* import */
69: extern ServerOptions options;
70: extern u_char *session_id2;
1.4 markus 71: extern u_int session_id2_len;
1.1 markus 72:
1.73 djm 73: static char *
74: format_key(const struct sshkey *key)
75: {
76: char *ret, *fp = sshkey_fingerprint(key,
77: options.fingerprint_hash, SSH_FP_DEFAULT);
78:
79: xasprintf(&ret, "%s %s", sshkey_type(key), fp);
80: free(fp);
81: return ret;
82: }
83:
1.2 markus 84: static int
1.65 markus 85: userauth_pubkey(struct ssh *ssh)
1.1 markus 86: {
1.65 markus 87: Authctxt *authctxt = ssh->authctxt;
1.77 djm 88: struct passwd *pw = authctxt->pw;
1.83 djm 89: struct sshbuf *b = NULL;
1.63 markus 90: struct sshkey *key = NULL;
1.83 djm 91: char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL;
92: u_char *pkblob = NULL, *sig = NULL, have_sig;
1.64 markus 93: size_t blen, slen;
94: int r, pktype;
1.1 markus 95: int authenticated = 0;
1.77 djm 96: struct sshauthopt *authopts = NULL;
1.1 markus 97:
1.75 djm 98: if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 ||
99: (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 ||
100: (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0)
101: fatal("%s: parse request failed: %s", __func__, ssh_err(r));
1.64 markus 102: pktype = sshkey_type_from_name(pkalg);
1.1 markus 103: if (pktype == KEY_UNSPEC) {
104: /* this is perfectly legal */
1.80 djm 105: verbose("%s: unsupported public key algorithm: %s",
1.55 djm 106: __func__, pkalg);
1.1 markus 107: goto done;
108: }
1.64 markus 109: if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
110: error("%s: could not parse key: %s", __func__, ssh_err(r));
111: goto done;
112: }
1.1 markus 113: if (key == NULL) {
1.55 djm 114: error("%s: cannot decode key: %s", __func__, pkalg);
1.1 markus 115: goto done;
116: }
117: if (key->type != pktype) {
1.55 djm 118: error("%s: type mismatch for decoded key "
119: "(received %d, expected %d)", __func__, key->type, pktype);
1.39 djm 120: goto done;
121: }
1.64 markus 122: if (sshkey_type_plain(key->type) == KEY_RSA &&
123: (ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
1.39 djm 124: logit("Refusing RSA key because client uses unsafe "
125: "signature scheme");
1.1 markus 126: goto done;
127: }
1.68 djm 128: if (auth2_key_already_used(authctxt, key)) {
1.64 markus 129: logit("refusing previously-used %s key", sshkey_type(key));
1.44 djm 130: goto done;
131: }
1.80 djm 132: if (match_pattern_list(pkalg, options.pubkey_key_types, 0) != 1) {
1.45 djm 133: logit("%s: key type %s not in PubkeyAcceptedKeyTypes",
134: __func__, sshkey_ssh_name(key));
135: goto done;
136: }
1.86 ! djm 137: if ((r = sshkey_check_cert_sigtype(key,
! 138: options.ca_sign_algorithms)) != 0) {
! 139: logit("%s: certificate signature algorithm %s: %s", __func__,
! 140: (key->cert == NULL || key->cert->signature_type == NULL) ?
! 141: "(null)" : key->cert->signature_type, ssh_err(r));
! 142: goto done;
! 143: }
1.73 djm 144: key_s = format_key(key);
145: if (sshkey_is_cert(key))
146: ca_s = format_key(key->cert->signature_key);
147:
1.1 markus 148: if (have_sig) {
1.73 djm 149: debug3("%s: have %s signature for %s%s%s",
150: __func__, pkalg, key_s,
151: ca_s == NULL ? "" : " CA ",
152: ca_s == NULL ? "" : ca_s);
1.64 markus 153: if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 ||
154: (r = sshpkt_get_end(ssh)) != 0)
155: fatal("%s: %s", __func__, ssh_err(r));
156: if ((b = sshbuf_new()) == NULL)
157: fatal("%s: sshbuf_new failed", __func__);
158: if (ssh->compat & SSH_OLD_SESSIONID) {
159: if ((r = sshbuf_put(b, session_id2,
160: session_id2_len)) != 0)
161: fatal("%s: sshbuf_put session id: %s",
162: __func__, ssh_err(r));
1.1 markus 163: } else {
1.64 markus 164: if ((r = sshbuf_put_string(b, session_id2,
165: session_id2_len)) != 0)
166: fatal("%s: sshbuf_put_string session id: %s",
167: __func__, ssh_err(r));
1.1 markus 168: }
1.83 djm 169: if (!authctxt->valid || authctxt->user == NULL) {
170: debug2("%s: disabled because of invalid user",
171: __func__);
172: goto done;
173: }
1.1 markus 174: /* reconstruct packet */
1.35 djm 175: xasprintf(&userstyle, "%s%s%s", authctxt->user,
176: authctxt->style ? ":" : "",
177: authctxt->style ? authctxt->style : "");
1.64 markus 178: if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
179: (r = sshbuf_put_cstring(b, userstyle)) != 0 ||
1.75 djm 180: (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
181: (r = sshbuf_put_cstring(b, "publickey")) != 0 ||
182: (r = sshbuf_put_u8(b, have_sig)) != 0 ||
1.85 mestre 183: (r = sshbuf_put_cstring(b, pkalg)) != 0 ||
1.75 djm 184: (r = sshbuf_put_string(b, pkblob, blen)) != 0)
1.64 markus 185: fatal("%s: build packet failed: %s",
186: __func__, ssh_err(r));
1.1 markus 187: #ifdef DEBUG_PK
1.64 markus 188: sshbuf_dump(b, stderr);
1.1 markus 189: #endif
190: /* test for correct signature */
191: authenticated = 0;
1.77 djm 192: if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) &&
1.80 djm 193: PRIVSEP(sshkey_verify(key, sig, slen,
194: sshbuf_ptr(b), sshbuf_len(b),
195: (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL,
196: ssh->compat)) == 0) {
1.1 markus 197: authenticated = 1;
1.44 djm 198: }
1.68 djm 199: auth2_record_key(authctxt, authenticated, key);
1.1 markus 200: } else {
1.73 djm 201: debug("%s: test pkalg %s pkblob %s%s%s",
202: __func__, pkalg, key_s,
203: ca_s == NULL ? "" : " CA ",
204: ca_s == NULL ? "" : ca_s);
205:
1.64 markus 206: if ((r = sshpkt_get_end(ssh)) != 0)
207: fatal("%s: %s", __func__, ssh_err(r));
1.1 markus 208:
1.83 djm 209: if (!authctxt->valid || authctxt->user == NULL) {
210: debug2("%s: disabled because of invalid user",
211: __func__);
212: goto done;
213: }
1.1 markus 214: /* XXX fake reply and always send PK_OK ? */
215: /*
216: * XXX this allows testing whether a user is allowed
217: * to login: if you happen to have a valid pubkey this
218: * message is sent. the message is NEVER sent at all
219: * if a user is not allowed to login. is this an
220: * issue? -markus
221: */
1.77 djm 222: if (PRIVSEP(user_key_allowed(ssh, pw, key, 0, NULL))) {
1.64 markus 223: if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK))
224: != 0 ||
225: (r = sshpkt_put_cstring(ssh, pkalg)) != 0 ||
226: (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 ||
1.82 markus 227: (r = sshpkt_send(ssh)) != 0 ||
228: (r = ssh_packet_write_wait(ssh)) != 0)
1.64 markus 229: fatal("%s: %s", __func__, ssh_err(r));
1.1 markus 230: authctxt->postponed = 1;
231: }
232: }
233: done:
1.77 djm 234: if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) {
235: debug("%s: key options inconsistent with existing", __func__);
236: authenticated = 0;
237: }
1.55 djm 238: debug2("%s: authenticated %d pkalg %s", __func__, authenticated, pkalg);
1.77 djm 239:
1.84 djm 240: sshbuf_free(b);
1.77 djm 241: sshauthopt_free(authopts);
1.68 djm 242: sshkey_free(key);
1.64 markus 243: free(userstyle);
1.36 djm 244: free(pkalg);
245: free(pkblob);
1.73 djm 246: free(key_s);
247: free(ca_s);
1.83 djm 248: free(sig);
1.1 markus 249: return authenticated;
250: }
251:
1.24 djm 252: static int
1.40 djm 253: match_principals_option(const char *principal_list, struct sshkey_cert *cert)
1.24 djm 254: {
255: char *result;
256: u_int i;
257:
258: /* XXX percent_expand() sequences for authorized_principals? */
259:
260: for (i = 0; i < cert->nprincipals; i++) {
261: if ((result = match_list(cert->principals[i],
262: principal_list, NULL)) != NULL) {
263: debug3("matched principal from key options \"%.100s\"",
264: result);
1.36 djm 265: free(result);
1.24 djm 266: return 1;
267: }
268: }
269: return 0;
270: }
271:
1.77 djm 272: /*
273: * Process a single authorized_principals format line. Returns 0 and sets
274: * authoptsp is principal is authorised, -1 otherwise. "loc" is used as a
275: * log preamble for file/line information.
276: */
1.24 djm 277: static int
1.77 djm 278: check_principals_line(struct ssh *ssh, char *cp, const struct sshkey_cert *cert,
279: const char *loc, struct sshauthopt **authoptsp)
1.24 djm 280: {
1.77 djm 281: u_int i, found = 0;
282: char *ep, *line_opts;
283: const char *reason = NULL;
284: struct sshauthopt *opts = NULL;
285:
286: if (authoptsp != NULL)
287: *authoptsp = NULL;
288:
289: /* Trim trailing whitespace. */
290: ep = cp + strlen(cp) - 1;
291: while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t'))
292: *ep-- = '\0';
293:
294: /*
295: * If the line has internal whitespace then assume it has
296: * key options.
297: */
298: line_opts = NULL;
299: if ((ep = strrchr(cp, ' ')) != NULL ||
300: (ep = strrchr(cp, '\t')) != NULL) {
301: for (; *ep == ' ' || *ep == '\t'; ep++)
302: ;
303: line_opts = cp;
304: cp = ep;
305: }
306: if ((opts = sshauthopt_parse(line_opts, &reason)) == NULL) {
307: debug("%s: bad principals options: %s", loc, reason);
308: auth_debug_add("%s: bad principals options: %s", loc, reason);
309: return -1;
310: }
311: /* Check principals in cert against those on line */
312: for (i = 0; i < cert->nprincipals; i++) {
313: if (strcmp(cp, cert->principals[i]) != 0)
314: continue;
315: debug3("%s: matched principal \"%.100s\"",
316: loc, cert->principals[i]);
317: found = 1;
318: }
319: if (found && authoptsp != NULL) {
320: *authoptsp = opts;
321: opts = NULL;
322: }
323: sshauthopt_free(opts);
324: return found ? 0 : -1;
325: }
326:
327: static int
328: process_principals(struct ssh *ssh, FILE *f, const char *file,
329: const struct sshkey_cert *cert, struct sshauthopt **authoptsp)
330: {
1.79 markus 331: char loc[256], *line = NULL, *cp, *ep;
332: size_t linesize = 0;
1.24 djm 333: u_long linenum = 0;
1.77 djm 334: u_int found_principal = 0;
335:
336: if (authoptsp != NULL)
337: *authoptsp = NULL;
1.24 djm 338:
1.79 markus 339: while (getline(&line, &linesize, f) != -1) {
340: linenum++;
1.62 djm 341: /* Always consume entire input */
342: if (found_principal)
343: continue;
1.77 djm 344:
1.26 djm 345: /* Skip leading whitespace. */
1.24 djm 346: for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
347: ;
1.26 djm 348: /* Skip blank and comment lines. */
349: if ((ep = strchr(cp, '#')) != NULL)
350: *ep = '\0';
351: if (!*cp || *cp == '\n')
1.24 djm 352: continue;
1.77 djm 353:
354: snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
355: if (check_principals_line(ssh, cp, cert, loc, authoptsp) == 0)
356: found_principal = 1;
1.24 djm 357: }
1.79 markus 358: free(line);
1.62 djm 359: return found_principal;
1.51 djm 360: }
361:
1.77 djm 362: /* XXX remove pw args here and elsewhere once ssh->authctxt is guaranteed */
363:
1.51 djm 364: static int
1.77 djm 365: match_principals_file(struct ssh *ssh, struct passwd *pw, char *file,
366: struct sshkey_cert *cert, struct sshauthopt **authoptsp)
1.51 djm 367: {
368: FILE *f;
369: int success;
370:
1.77 djm 371: if (authoptsp != NULL)
372: *authoptsp = NULL;
373:
1.51 djm 374: temporarily_use_uid(pw);
375: debug("trying authorized principals file %s", file);
376: if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
377: restore_uid();
378: return 0;
379: }
1.77 djm 380: success = process_principals(ssh, f, file, cert, authoptsp);
1.24 djm 381: fclose(f);
382: restore_uid();
1.51 djm 383: return success;
1.31 djm 384: }
1.24 djm 385:
1.31 djm 386: /*
1.51 djm 387: * Checks whether principal is allowed in output of command.
388: * returns 1 if the principal is allowed or 0 otherwise.
389: */
390: static int
1.77 djm 391: match_principals_command(struct ssh *ssh, struct passwd *user_pw,
392: const struct sshkey *key, struct sshauthopt **authoptsp)
1.51 djm 393: {
1.77 djm 394: struct passwd *runas_pw = NULL;
1.56 djm 395: const struct sshkey_cert *cert = key->cert;
1.51 djm 396: FILE *f = NULL;
1.56 djm 397: int r, ok, found_principal = 0;
1.51 djm 398: int i, ac = 0, uid_swapped = 0;
399: pid_t pid;
400: char *tmp, *username = NULL, *command = NULL, **av = NULL;
1.56 djm 401: char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL;
1.78 djm 402: char serial_s[16], uidstr[32];
1.51 djm 403: void (*osigchld)(int);
404:
1.77 djm 405: if (authoptsp != NULL)
406: *authoptsp = NULL;
1.51 djm 407: if (options.authorized_principals_command == NULL)
408: return 0;
409: if (options.authorized_principals_command_user == NULL) {
410: error("No user for AuthorizedPrincipalsCommand specified, "
411: "skipping");
412: return 0;
413: }
414:
415: /*
416: * NB. all returns later this function should go via "out" to
417: * ensure the original SIGCHLD handler is restored properly.
418: */
419: osigchld = signal(SIGCHLD, SIG_DFL);
420:
421: /* Prepare and verify the user for the command */
422: username = percent_expand(options.authorized_principals_command_user,
423: "u", user_pw->pw_name, (char *)NULL);
1.77 djm 424: runas_pw = getpwnam(username);
425: if (runas_pw == NULL) {
1.51 djm 426: error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s",
427: username, strerror(errno));
428: goto out;
429: }
430:
431: /* Turn the command into an argument vector */
1.69 djm 432: if (argv_split(options.authorized_principals_command, &ac, &av) != 0) {
1.51 djm 433: error("AuthorizedPrincipalsCommand \"%s\" contains "
434: "invalid quotes", command);
435: goto out;
436: }
437: if (ac == 0) {
438: error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
439: command);
440: goto out;
441: }
1.56 djm 442: if ((ca_fp = sshkey_fingerprint(cert->signature_key,
443: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
444: error("%s: sshkey_fingerprint failed", __func__);
445: goto out;
446: }
1.57 djm 447: if ((key_fp = sshkey_fingerprint(key,
1.56 djm 448: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
449: error("%s: sshkey_fingerprint failed", __func__);
450: goto out;
451: }
452: if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) {
453: error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
454: goto out;
455: }
456: if ((r = sshkey_to_base64(key, &keytext)) != 0) {
457: error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
458: goto out;
459: }
1.59 djm 460: snprintf(serial_s, sizeof(serial_s), "%llu",
461: (unsigned long long)cert->serial);
1.78 djm 462: snprintf(uidstr, sizeof(uidstr), "%llu",
463: (unsigned long long)user_pw->pw_uid);
1.51 djm 464: for (i = 1; i < ac; i++) {
465: tmp = percent_expand(av[i],
1.78 djm 466: "U", uidstr,
1.51 djm 467: "u", user_pw->pw_name,
468: "h", user_pw->pw_dir,
1.56 djm 469: "t", sshkey_ssh_name(key),
470: "T", sshkey_ssh_name(cert->signature_key),
471: "f", key_fp,
472: "F", ca_fp,
473: "k", keytext,
474: "K", catext,
1.58 djm 475: "i", cert->key_id,
476: "s", serial_s,
1.51 djm 477: (char *)NULL);
478: if (tmp == NULL)
479: fatal("%s: percent_expand failed", __func__);
480: free(av[i]);
481: av[i] = tmp;
482: }
483: /* Prepare a printable command for logs, etc. */
1.69 djm 484: command = argv_assemble(ac, av);
1.51 djm 485:
1.77 djm 486: if ((pid = subprocess("AuthorizedPrincipalsCommand", runas_pw, command,
1.69 djm 487: ac, av, &f,
488: SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
1.51 djm 489: goto out;
490:
491: uid_swapped = 1;
1.77 djm 492: temporarily_use_uid(runas_pw);
1.51 djm 493:
1.77 djm 494: ok = process_principals(ssh, f, "(command)", cert, authoptsp);
1.51 djm 495:
1.61 djm 496: fclose(f);
497: f = NULL;
498:
1.70 djm 499: if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0)
1.51 djm 500: goto out;
501:
502: /* Read completed successfully */
503: found_principal = ok;
504: out:
505: if (f != NULL)
506: fclose(f);
507: signal(SIGCHLD, osigchld);
508: for (i = 0; i < ac; i++)
509: free(av[i]);
510: free(av);
511: if (uid_swapped)
512: restore_uid();
513: free(command);
514: free(username);
1.56 djm 515: free(ca_fp);
516: free(key_fp);
517: free(catext);
518: free(keytext);
1.51 djm 519: return found_principal;
520: }
1.77 djm 521:
522: static void
523: skip_space(char **cpp)
524: {
525: char *cp;
526:
527: for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
528: ;
529: *cpp = cp;
530: }
531:
532: /*
533: * Advanced *cpp past the end of key options, defined as the first unquoted
534: * whitespace character. Returns 0 on success or -1 on failure (e.g.
535: * unterminated quotes).
536: */
537: static int
538: advance_past_options(char **cpp)
539: {
540: char *cp = *cpp;
541: int quoted = 0;
542:
543: for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
544: if (*cp == '\\' && cp[1] == '"')
545: cp++; /* Skip both */
546: else if (*cp == '"')
547: quoted = !quoted;
548: }
549: *cpp = cp;
550: /* return failure for unterminated quotes */
551: return (*cp == '\0' && quoted) ? -1 : 0;
552: }
553:
554: /*
555: * Check a single line of an authorized_keys-format file. Returns 0 if key
556: * matches, -1 otherwise. Will return key/cert options via *authoptsp
557: * on success. "loc" is used as file/line location in log messages.
558: */
559: static int
560: check_authkey_line(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
561: char *cp, const char *loc, struct sshauthopt **authoptsp)
562: {
563: int want_keytype = sshkey_is_cert(key) ? KEY_UNSPEC : key->type;
564: struct sshkey *found = NULL;
565: struct sshauthopt *keyopts = NULL, *certopts = NULL, *finalopts = NULL;
566: char *key_options = NULL, *fp = NULL;
567: const char *reason = NULL;
568: int ret = -1;
569:
570: if (authoptsp != NULL)
571: *authoptsp = NULL;
572:
573: if ((found = sshkey_new(want_keytype)) == NULL) {
574: debug3("%s: keytype %d failed", __func__, want_keytype);
575: goto out;
576: }
577:
578: /* XXX djm: peek at key type in line and skip if unwanted */
579:
580: if (sshkey_read(found, &cp) != 0) {
581: /* no key? check for options */
582: debug2("%s: check options: '%s'", loc, cp);
583: key_options = cp;
584: if (advance_past_options(&cp) != 0) {
585: reason = "invalid key option string";
586: goto fail_reason;
587: }
588: skip_space(&cp);
589: if (sshkey_read(found, &cp) != 0) {
590: /* still no key? advance to next line*/
591: debug2("%s: advance: '%s'", loc, cp);
592: goto out;
593: }
594: }
595: /* Parse key options now; we need to know if this is a CA key */
596: if ((keyopts = sshauthopt_parse(key_options, &reason)) == NULL) {
597: debug("%s: bad key options: %s", loc, reason);
598: auth_debug_add("%s: bad key options: %s", loc, reason);
599: goto out;
600: }
601: /* Ignore keys that don't match or incorrectly marked as CAs */
602: if (sshkey_is_cert(key)) {
603: /* Certificate; check signature key against CA */
604: if (!sshkey_equal(found, key->cert->signature_key) ||
605: !keyopts->cert_authority)
606: goto out;
607: } else {
608: /* Plain key: check it against key found in file */
609: if (!sshkey_equal(found, key) || keyopts->cert_authority)
610: goto out;
611: }
612:
613: /* We have a candidate key, perform authorisation checks */
614: if ((fp = sshkey_fingerprint(found,
615: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
616: fatal("%s: fingerprint failed", __func__);
617:
618: debug("%s: matching %s found: %s %s", loc,
619: sshkey_is_cert(key) ? "CA" : "key", sshkey_type(found), fp);
620:
621: if (auth_authorise_keyopts(ssh, pw, keyopts,
622: sshkey_is_cert(key), loc) != 0) {
623: reason = "Refused by key options";
624: goto fail_reason;
625: }
626: /* That's all we need for plain keys. */
627: if (!sshkey_is_cert(key)) {
628: verbose("Accepted key %s %s found at %s",
629: sshkey_type(found), fp, loc);
630: finalopts = keyopts;
631: keyopts = NULL;
632: goto success;
633: }
634:
635: /*
636: * Additional authorisation for certificates.
637: */
638:
639: /* Parse and check options present in certificate */
640: if ((certopts = sshauthopt_from_cert(key)) == NULL) {
641: reason = "Invalid certificate options";
642: goto fail_reason;
643: }
644: if (auth_authorise_keyopts(ssh, pw, certopts, 0, loc) != 0) {
645: reason = "Refused by certificate options";
646: goto fail_reason;
647: }
648: if ((finalopts = sshauthopt_merge(keyopts, certopts, &reason)) == NULL)
649: goto fail_reason;
650:
651: /*
652: * If the user has specified a list of principals as
653: * a key option, then prefer that list to matching
654: * their username in the certificate principals list.
655: */
656: if (keyopts->cert_principals != NULL &&
657: !match_principals_option(keyopts->cert_principals, key->cert)) {
658: reason = "Certificate does not contain an authorized principal";
659: goto fail_reason;
660: }
661: if (sshkey_cert_check_authority(key, 0, 0,
662: keyopts->cert_principals == NULL ? pw->pw_name : NULL, &reason) != 0)
663: goto fail_reason;
664:
665: verbose("Accepted certificate ID \"%s\" (serial %llu) "
666: "signed by CA %s %s found at %s",
667: key->cert->key_id,
668: (unsigned long long)key->cert->serial,
669: sshkey_type(found), fp, loc);
670:
671: success:
672: if (finalopts == NULL)
673: fatal("%s: internal error: missing options", __func__);
674: if (authoptsp != NULL) {
675: *authoptsp = finalopts;
676: finalopts = NULL;
677: }
678: /* success */
679: ret = 0;
680: goto out;
681:
682: fail_reason:
683: error("%s", reason);
684: auth_debug_add("%s", reason);
685: out:
686: free(fp);
687: sshauthopt_free(keyopts);
688: sshauthopt_free(certopts);
689: sshauthopt_free(finalopts);
690: sshkey_free(found);
691: return ret;
692: }
693:
1.51 djm 694: /*
1.31 djm 695: * Checks whether key is allowed in authorized_keys-format file,
696: * returns 1 if the key is allowed or 0 otherwise.
697: */
1.1 markus 698: static int
1.77 djm 699: check_authkeys_file(struct ssh *ssh, struct passwd *pw, FILE *f,
700: char *file, struct sshkey *key, struct sshauthopt **authoptsp)
1.1 markus 701: {
1.79 markus 702: char *cp, *line = NULL, loc[256];
703: size_t linesize = 0;
1.18 dtucker 704: int found_key = 0;
1.1 markus 705: u_long linenum = 0;
1.77 djm 706:
707: if (authoptsp != NULL)
708: *authoptsp = NULL;
1.1 markus 709:
1.79 markus 710: while (getline(&line, &linesize, f) != -1) {
711: linenum++;
1.71 djm 712: /* Always consume entire file */
1.62 djm 713: if (found_key)
714: continue;
1.20 djm 715:
1.1 markus 716: /* Skip leading whitespace, empty and comment lines. */
1.77 djm 717: cp = line;
718: skip_space(&cp);
1.1 markus 719: if (!*cp || *cp == '\n' || *cp == '#')
720: continue;
1.77 djm 721: snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
722: if (check_authkey_line(ssh, pw, key, cp, loc, authoptsp) == 0)
1.20 djm 723: found_key = 1;
1.1 markus 724: }
1.79 markus 725: free(line);
1.1 markus 726: return found_key;
727: }
728:
1.21 djm 729: /* Authenticate a certificate key against TrustedUserCAKeys */
730: static int
1.77 djm 731: user_cert_trusted_ca(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
732: struct sshauthopt **authoptsp)
1.21 djm 733: {
1.24 djm 734: char *ca_fp, *principals_file = NULL;
1.21 djm 735: const char *reason;
1.77 djm 736: struct sshauthopt *principals_opts = NULL, *cert_opts = NULL;
737: struct sshauthopt *final_opts = NULL;
1.64 markus 738: int r, ret = 0, found_principal = 0, use_authorized_principals;
1.21 djm 739:
1.77 djm 740: if (authoptsp != NULL)
741: *authoptsp = NULL;
742:
1.64 markus 743: if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL)
1.21 djm 744: return 0;
745:
1.46 djm 746: if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
747: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
748: return 0;
1.21 djm 749:
1.64 markus 750: if ((r = sshkey_in_file(key->cert->signature_key,
751: options.trusted_user_ca_keys, 1, 0)) != 0) {
752: debug2("%s: CA %s %s is not listed in %s: %s", __func__,
753: sshkey_type(key->cert->signature_key), ca_fp,
754: options.trusted_user_ca_keys, ssh_err(r));
1.21 djm 755: goto out;
756: }
1.24 djm 757: /*
758: * If AuthorizedPrincipals is in use, then compare the certificate
759: * principals against the names in that file rather than matching
760: * against the username.
761: */
762: if ((principals_file = authorized_principals_file(pw)) != NULL) {
1.77 djm 763: if (match_principals_file(ssh, pw, principals_file,
764: key->cert, &principals_opts))
1.51 djm 765: found_principal = 1;
766: }
767: /* Try querying command if specified */
1.77 djm 768: if (!found_principal && match_principals_command(ssh, pw, key,
769: &principals_opts))
1.51 djm 770: found_principal = 1;
1.53 jsing 771: /* If principals file or command is specified, then require a match */
772: use_authorized_principals = principals_file != NULL ||
773: options.authorized_principals_command != NULL;
774: if (!found_principal && use_authorized_principals) {
1.51 djm 775: reason = "Certificate does not contain an authorized principal";
1.77 djm 776: goto fail_reason;
1.21 djm 777: }
1.77 djm 778: if (use_authorized_principals && principals_opts == NULL)
779: fatal("%s: internal error: missing principals_opts", __func__);
1.64 markus 780: if (sshkey_cert_check_authority(key, 0, 1,
1.53 jsing 781: use_authorized_principals ? NULL : pw->pw_name, &reason) != 0)
1.24 djm 782: goto fail_reason;
1.77 djm 783:
784: /* Check authority from options in key and from principals file/cmd */
785: if ((cert_opts = sshauthopt_from_cert(key)) == NULL) {
786: reason = "Invalid certificate options";
787: goto fail_reason;
788: }
789: if (auth_authorise_keyopts(ssh, pw, cert_opts, 0, "cert") != 0) {
790: reason = "Refused by certificate options";
1.60 djm 791: goto fail_reason;
1.77 djm 792: }
793: if (principals_opts == NULL) {
794: final_opts = cert_opts;
795: cert_opts = NULL;
796: } else {
797: if (auth_authorise_keyopts(ssh, pw, principals_opts, 0,
798: "principals") != 0) {
799: reason = "Refused by certificate principals options";
800: goto fail_reason;
801: }
802: if ((final_opts = sshauthopt_merge(principals_opts,
803: cert_opts, &reason)) == NULL) {
804: fail_reason:
805: error("%s", reason);
806: auth_debug_add("%s", reason);
807: goto out;
808: }
809: }
1.21 djm 810:
1.77 djm 811: /* Success */
1.54 djm 812: verbose("Accepted certificate ID \"%s\" (serial %llu) signed by "
813: "%s CA %s via %s", key->cert->key_id,
814: (unsigned long long)key->cert->serial,
1.64 markus 815: sshkey_type(key->cert->signature_key), ca_fp,
1.22 djm 816: options.trusted_user_ca_keys);
1.77 djm 817: if (authoptsp != NULL) {
818: *authoptsp = final_opts;
819: final_opts = NULL;
820: }
1.21 djm 821: ret = 1;
822: out:
1.77 djm 823: sshauthopt_free(principals_opts);
824: sshauthopt_free(cert_opts);
825: sshauthopt_free(final_opts);
1.36 djm 826: free(principals_file);
827: free(ca_fp);
1.21 djm 828: return ret;
829: }
830:
1.31 djm 831: /*
832: * Checks whether key is allowed in file.
833: * returns 1 if the key is allowed or 0 otherwise.
834: */
835: static int
1.77 djm 836: user_key_allowed2(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
837: char *file, struct sshauthopt **authoptsp)
1.31 djm 838: {
839: FILE *f;
840: int found_key = 0;
841:
1.77 djm 842: if (authoptsp != NULL)
843: *authoptsp = NULL;
844:
1.31 djm 845: /* Temporarily use the user's uid. */
846: temporarily_use_uid(pw);
847:
848: debug("trying public key file %s", file);
849: if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
1.77 djm 850: found_key = check_authkeys_file(ssh, pw, f, file,
851: key, authoptsp);
1.31 djm 852: fclose(f);
853: }
854:
855: restore_uid();
856: return found_key;
857: }
858:
859: /*
860: * Checks whether key is allowed in output of command.
861: * returns 1 if the key is allowed or 0 otherwise.
862: */
863: static int
1.77 djm 864: user_key_command_allowed2(struct ssh *ssh, struct passwd *user_pw,
865: struct sshkey *key, struct sshauthopt **authoptsp)
1.31 djm 866: {
1.77 djm 867: struct passwd *runas_pw = NULL;
1.50 djm 868: FILE *f = NULL;
869: int r, ok, found_key = 0;
870: int i, uid_swapped = 0, ac = 0;
1.31 djm 871: pid_t pid;
1.50 djm 872: char *username = NULL, *key_fp = NULL, *keytext = NULL;
1.78 djm 873: char uidstr[32], *tmp, *command = NULL, **av = NULL;
1.50 djm 874: void (*osigchld)(int);
1.31 djm 875:
1.77 djm 876: if (authoptsp != NULL)
877: *authoptsp = NULL;
1.50 djm 878: if (options.authorized_keys_command == NULL)
1.31 djm 879: return 0;
1.32 djm 880: if (options.authorized_keys_command_user == NULL) {
881: error("No user for AuthorizedKeysCommand specified, skipping");
882: return 0;
883: }
884:
1.50 djm 885: /*
886: * NB. all returns later this function should go via "out" to
887: * ensure the original SIGCHLD handler is restored properly.
888: */
889: osigchld = signal(SIGCHLD, SIG_DFL);
890:
891: /* Prepare and verify the user for the command */
1.32 djm 892: username = percent_expand(options.authorized_keys_command_user,
893: "u", user_pw->pw_name, (char *)NULL);
1.77 djm 894: runas_pw = getpwnam(username);
895: if (runas_pw == NULL) {
1.34 djm 896: error("AuthorizedKeysCommandUser \"%s\" not found: %s",
897: username, strerror(errno));
1.50 djm 898: goto out;
1.31 djm 899: }
900:
1.50 djm 901: /* Prepare AuthorizedKeysCommand */
902: if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash,
903: SSH_FP_DEFAULT)) == NULL) {
904: error("%s: sshkey_fingerprint failed", __func__);
1.31 djm 905: goto out;
906: }
1.50 djm 907: if ((r = sshkey_to_base64(key, &keytext)) != 0) {
908: error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
1.31 djm 909: goto out;
910: }
911:
1.50 djm 912: /* Turn the command into an argument vector */
1.69 djm 913: if (argv_split(options.authorized_keys_command, &ac, &av) != 0) {
1.50 djm 914: error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
915: command);
916: goto out;
917: }
918: if (ac == 0) {
919: error("AuthorizedKeysCommand \"%s\" yielded no arguments",
920: command);
1.31 djm 921: goto out;
922: }
1.78 djm 923: snprintf(uidstr, sizeof(uidstr), "%llu",
924: (unsigned long long)user_pw->pw_uid);
1.50 djm 925: for (i = 1; i < ac; i++) {
926: tmp = percent_expand(av[i],
1.78 djm 927: "U", uidstr,
1.50 djm 928: "u", user_pw->pw_name,
929: "h", user_pw->pw_dir,
930: "t", sshkey_ssh_name(key),
931: "f", key_fp,
932: "k", keytext,
933: (char *)NULL);
934: if (tmp == NULL)
935: fatal("%s: percent_expand failed", __func__);
936: free(av[i]);
937: av[i] = tmp;
938: }
939: /* Prepare a printable command for logs, etc. */
1.69 djm 940: command = argv_assemble(ac, av);
1.31 djm 941:
942: /*
1.50 djm 943: * If AuthorizedKeysCommand was run without arguments
944: * then fall back to the old behaviour of passing the
945: * target username as a single argument.
1.31 djm 946: */
1.50 djm 947: if (ac == 1) {
948: av = xreallocarray(av, ac + 2, sizeof(*av));
949: av[1] = xstrdup(user_pw->pw_name);
950: av[2] = NULL;
951: /* Fix up command too, since it is used in log messages */
952: free(command);
953: xasprintf(&command, "%s %s", av[0], av[1]);
954: }
1.31 djm 955:
1.77 djm 956: if ((pid = subprocess("AuthorizedKeysCommand", runas_pw, command,
1.69 djm 957: ac, av, &f,
958: SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
1.50 djm 959: goto out;
1.31 djm 960:
1.50 djm 961: uid_swapped = 1;
1.77 djm 962: temporarily_use_uid(runas_pw);
1.31 djm 963:
1.77 djm 964: ok = check_authkeys_file(ssh, user_pw, f,
965: options.authorized_keys_command, key, authoptsp);
1.61 djm 966:
967: fclose(f);
968: f = NULL;
1.31 djm 969:
1.70 djm 970: if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0)
1.31 djm 971: goto out;
1.50 djm 972:
973: /* Read completed successfully */
1.31 djm 974: found_key = ok;
975: out:
1.50 djm 976: if (f != NULL)
977: fclose(f);
978: signal(SIGCHLD, osigchld);
979: for (i = 0; i < ac; i++)
980: free(av[i]);
981: free(av);
982: if (uid_swapped)
983: restore_uid();
984: free(command);
985: free(username);
986: free(key_fp);
987: free(keytext);
1.31 djm 988: return found_key;
989: }
990:
991: /*
992: * Check whether key authenticates and authorises the user.
993: */
1.1 markus 994: int
1.77 djm 995: user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
996: int auth_attempt, struct sshauthopt **authoptsp)
1.1 markus 997: {
1.29 djm 998: u_int success, i;
1.1 markus 999: char *file;
1.77 djm 1000: struct sshauthopt *opts = NULL;
1001: if (authoptsp != NULL)
1002: *authoptsp = NULL;
1.21 djm 1003:
1004: if (auth_key_is_revoked(key))
1005: return 0;
1.64 markus 1006: if (sshkey_is_cert(key) &&
1007: auth_key_is_revoked(key->cert->signature_key))
1.21 djm 1008: return 0;
1009:
1.77 djm 1010: if ((success = user_cert_trusted_ca(ssh, pw, key, &opts)) != 0)
1011: goto out;
1012: sshauthopt_free(opts);
1013: opts = NULL;
1014:
1015: if ((success = user_key_command_allowed2(ssh, pw, key, &opts)) != 0)
1016: goto out;
1017: sshauthopt_free(opts);
1018: opts = NULL;
1.31 djm 1019:
1.29 djm 1020: for (i = 0; !success && i < options.num_authkeys_files; i++) {
1.31 djm 1021: if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
1022: continue;
1.29 djm 1023: file = expand_authorized_keys(
1024: options.authorized_keys_files[i], pw);
1.77 djm 1025: success = user_key_allowed2(ssh, pw, key, file, &opts);
1.36 djm 1026: free(file);
1.29 djm 1027: }
1.1 markus 1028:
1.77 djm 1029: out:
1030: if (success && authoptsp != NULL) {
1031: *authoptsp = opts;
1032: opts = NULL;
1033: }
1034: sshauthopt_free(opts);
1.1 markus 1035: return success;
1036: }
1.2 markus 1037:
1038: Authmethod method_pubkey = {
1039: "publickey",
1040: userauth_pubkey,
1041: &options.pubkey_authentication
1042: };
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