Annotation of src/usr.bin/ssh/auth2-pubkey.c, Revision 1.78
1.78 ! djm 1: /* $OpenBSD: auth2-pubkey.c,v 1.77 2018/03/03 03:15:51 djm 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"
46: #include "buffer.h"
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;
1.64 markus 89: struct sshbuf *b;
1.63 markus 90: struct sshkey *key = NULL;
1.73 djm 91: char *pkalg, *userstyle = NULL, *key_s = NULL, *ca_s = NULL;
1.64 markus 92: u_char *pkblob, *sig, have_sig;
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:
98: if (!authctxt->valid) {
1.55 djm 99: debug2("%s: disabled because of invalid user", __func__);
1.1 markus 100: return 0;
101: }
1.75 djm 102: if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 ||
103: (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 ||
104: (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0)
105: fatal("%s: parse request failed: %s", __func__, ssh_err(r));
1.64 markus 106: pktype = sshkey_type_from_name(pkalg);
1.1 markus 107: if (pktype == KEY_UNSPEC) {
108: /* this is perfectly legal */
1.55 djm 109: logit("%s: unsupported public key algorithm: %s",
110: __func__, pkalg);
1.1 markus 111: goto done;
112: }
1.64 markus 113: if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
114: error("%s: could not parse key: %s", __func__, ssh_err(r));
115: goto done;
116: }
1.1 markus 117: if (key == NULL) {
1.55 djm 118: error("%s: cannot decode key: %s", __func__, pkalg);
1.1 markus 119: goto done;
120: }
121: if (key->type != pktype) {
1.55 djm 122: error("%s: type mismatch for decoded key "
123: "(received %d, expected %d)", __func__, key->type, pktype);
1.39 djm 124: goto done;
125: }
1.64 markus 126: if (sshkey_type_plain(key->type) == KEY_RSA &&
127: (ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
1.39 djm 128: logit("Refusing RSA key because client uses unsafe "
129: "signature scheme");
1.1 markus 130: goto done;
131: }
1.68 djm 132: if (auth2_key_already_used(authctxt, key)) {
1.64 markus 133: logit("refusing previously-used %s key", sshkey_type(key));
1.44 djm 134: goto done;
135: }
1.49 djm 136: if (match_pattern_list(sshkey_ssh_name(key),
137: options.pubkey_key_types, 0) != 1) {
1.45 djm 138: logit("%s: key type %s not in PubkeyAcceptedKeyTypes",
139: __func__, sshkey_ssh_name(key));
140: goto done;
141: }
142:
1.73 djm 143: key_s = format_key(key);
144: if (sshkey_is_cert(key))
145: ca_s = format_key(key->cert->signature_key);
146:
1.1 markus 147: if (have_sig) {
1.73 djm 148: debug3("%s: have %s signature for %s%s%s",
149: __func__, pkalg, key_s,
150: ca_s == NULL ? "" : " CA ",
151: ca_s == NULL ? "" : ca_s);
1.64 markus 152: if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 ||
153: (r = sshpkt_get_end(ssh)) != 0)
154: fatal("%s: %s", __func__, ssh_err(r));
155: if ((b = sshbuf_new()) == NULL)
156: fatal("%s: sshbuf_new failed", __func__);
157: if (ssh->compat & SSH_OLD_SESSIONID) {
158: if ((r = sshbuf_put(b, session_id2,
159: session_id2_len)) != 0)
160: fatal("%s: sshbuf_put session id: %s",
161: __func__, ssh_err(r));
1.1 markus 162: } else {
1.64 markus 163: if ((r = sshbuf_put_string(b, session_id2,
164: session_id2_len)) != 0)
165: fatal("%s: sshbuf_put_string session id: %s",
166: __func__, ssh_err(r));
1.1 markus 167: }
168: /* reconstruct packet */
1.35 djm 169: xasprintf(&userstyle, "%s%s%s", authctxt->user,
170: authctxt->style ? ":" : "",
171: authctxt->style ? authctxt->style : "");
1.64 markus 172: if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
173: (r = sshbuf_put_cstring(b, userstyle)) != 0 ||
1.75 djm 174: (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
175: (r = sshbuf_put_cstring(b, "publickey")) != 0 ||
176: (r = sshbuf_put_u8(b, have_sig)) != 0 ||
177: (r = sshbuf_put_cstring(b, pkalg) != 0) ||
178: (r = sshbuf_put_string(b, pkblob, blen)) != 0)
1.64 markus 179: fatal("%s: build packet failed: %s",
180: __func__, ssh_err(r));
1.1 markus 181: #ifdef DEBUG_PK
1.64 markus 182: sshbuf_dump(b, stderr);
1.1 markus 183: #endif
1.37 djm 184:
1.1 markus 185: /* test for correct signature */
186: authenticated = 0;
1.77 djm 187: if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) &&
1.64 markus 188: PRIVSEP(sshkey_verify(key, sig, slen, sshbuf_ptr(b),
1.74 djm 189: sshbuf_len(b), NULL, ssh->compat)) == 0) {
1.1 markus 190: authenticated = 1;
1.44 djm 191: }
1.64 markus 192: sshbuf_free(b);
1.36 djm 193: free(sig);
1.68 djm 194: auth2_record_key(authctxt, authenticated, key);
1.1 markus 195: } else {
1.73 djm 196: debug("%s: test pkalg %s pkblob %s%s%s",
197: __func__, pkalg, key_s,
198: ca_s == NULL ? "" : " CA ",
199: ca_s == NULL ? "" : ca_s);
200:
1.64 markus 201: if ((r = sshpkt_get_end(ssh)) != 0)
202: fatal("%s: %s", __func__, ssh_err(r));
1.1 markus 203:
204: /* XXX fake reply and always send PK_OK ? */
205: /*
206: * XXX this allows testing whether a user is allowed
207: * to login: if you happen to have a valid pubkey this
208: * message is sent. the message is NEVER sent at all
209: * if a user is not allowed to login. is this an
210: * issue? -markus
211: */
1.77 djm 212: if (PRIVSEP(user_key_allowed(ssh, pw, key, 0, NULL))) {
1.64 markus 213: if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK))
214: != 0 ||
215: (r = sshpkt_put_cstring(ssh, pkalg)) != 0 ||
216: (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 ||
217: (r = sshpkt_send(ssh)) != 0)
218: fatal("%s: %s", __func__, ssh_err(r));
219: ssh_packet_write_wait(ssh);
1.1 markus 220: authctxt->postponed = 1;
221: }
222: }
223: done:
1.77 djm 224: if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) {
225: debug("%s: key options inconsistent with existing", __func__);
226: authenticated = 0;
227: }
1.55 djm 228: debug2("%s: authenticated %d pkalg %s", __func__, authenticated, pkalg);
1.77 djm 229:
230: sshauthopt_free(authopts);
1.68 djm 231: sshkey_free(key);
1.64 markus 232: free(userstyle);
1.36 djm 233: free(pkalg);
234: free(pkblob);
1.73 djm 235: free(key_s);
236: free(ca_s);
1.1 markus 237: return authenticated;
238: }
239:
1.24 djm 240: static int
1.40 djm 241: match_principals_option(const char *principal_list, struct sshkey_cert *cert)
1.24 djm 242: {
243: char *result;
244: u_int i;
245:
246: /* XXX percent_expand() sequences for authorized_principals? */
247:
248: for (i = 0; i < cert->nprincipals; i++) {
249: if ((result = match_list(cert->principals[i],
250: principal_list, NULL)) != NULL) {
251: debug3("matched principal from key options \"%.100s\"",
252: result);
1.36 djm 253: free(result);
1.24 djm 254: return 1;
255: }
256: }
257: return 0;
258: }
259:
1.77 djm 260: /*
261: * Process a single authorized_principals format line. Returns 0 and sets
262: * authoptsp is principal is authorised, -1 otherwise. "loc" is used as a
263: * log preamble for file/line information.
264: */
1.24 djm 265: static int
1.77 djm 266: check_principals_line(struct ssh *ssh, char *cp, const struct sshkey_cert *cert,
267: const char *loc, struct sshauthopt **authoptsp)
1.24 djm 268: {
1.77 djm 269: u_int i, found = 0;
270: char *ep, *line_opts;
271: const char *reason = NULL;
272: struct sshauthopt *opts = NULL;
273:
274: if (authoptsp != NULL)
275: *authoptsp = NULL;
276:
277: /* Trim trailing whitespace. */
278: ep = cp + strlen(cp) - 1;
279: while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t'))
280: *ep-- = '\0';
281:
282: /*
283: * If the line has internal whitespace then assume it has
284: * key options.
285: */
286: line_opts = NULL;
287: if ((ep = strrchr(cp, ' ')) != NULL ||
288: (ep = strrchr(cp, '\t')) != NULL) {
289: for (; *ep == ' ' || *ep == '\t'; ep++)
290: ;
291: line_opts = cp;
292: cp = ep;
293: }
294: if ((opts = sshauthopt_parse(line_opts, &reason)) == NULL) {
295: debug("%s: bad principals options: %s", loc, reason);
296: auth_debug_add("%s: bad principals options: %s", loc, reason);
297: return -1;
298: }
299: /* Check principals in cert against those on line */
300: for (i = 0; i < cert->nprincipals; i++) {
301: if (strcmp(cp, cert->principals[i]) != 0)
302: continue;
303: debug3("%s: matched principal \"%.100s\"",
304: loc, cert->principals[i]);
305: found = 1;
306: }
307: if (found && authoptsp != NULL) {
308: *authoptsp = opts;
309: opts = NULL;
310: }
311: sshauthopt_free(opts);
312: return found ? 0 : -1;
313: }
314:
315: static int
316: process_principals(struct ssh *ssh, FILE *f, const char *file,
317: const struct sshkey_cert *cert, struct sshauthopt **authoptsp)
318: {
319: char loc[256], line[SSH_MAX_PUBKEY_BYTES], *cp, *ep;
1.24 djm 320: u_long linenum = 0;
1.77 djm 321: u_int found_principal = 0;
322:
323: if (authoptsp != NULL)
324: *authoptsp = NULL;
1.24 djm 325:
326: while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
1.62 djm 327: /* Always consume entire input */
328: if (found_principal)
329: continue;
1.77 djm 330:
1.26 djm 331: /* Skip leading whitespace. */
1.24 djm 332: for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
333: ;
1.26 djm 334: /* Skip blank and comment lines. */
335: if ((ep = strchr(cp, '#')) != NULL)
336: *ep = '\0';
337: if (!*cp || *cp == '\n')
1.24 djm 338: continue;
1.77 djm 339:
340: snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
341: if (check_principals_line(ssh, cp, cert, loc, authoptsp) == 0)
342: found_principal = 1;
1.24 djm 343: }
1.62 djm 344: return found_principal;
1.51 djm 345: }
346:
1.77 djm 347: /* XXX remove pw args here and elsewhere once ssh->authctxt is guaranteed */
348:
1.51 djm 349: static int
1.77 djm 350: match_principals_file(struct ssh *ssh, struct passwd *pw, char *file,
351: struct sshkey_cert *cert, struct sshauthopt **authoptsp)
1.51 djm 352: {
353: FILE *f;
354: int success;
355:
1.77 djm 356: if (authoptsp != NULL)
357: *authoptsp = NULL;
358:
1.51 djm 359: temporarily_use_uid(pw);
360: debug("trying authorized principals file %s", file);
361: if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
362: restore_uid();
363: return 0;
364: }
1.77 djm 365: success = process_principals(ssh, f, file, cert, authoptsp);
1.24 djm 366: fclose(f);
367: restore_uid();
1.51 djm 368: return success;
1.31 djm 369: }
1.24 djm 370:
1.31 djm 371: /*
1.51 djm 372: * Checks whether principal is allowed in output of command.
373: * returns 1 if the principal is allowed or 0 otherwise.
374: */
375: static int
1.77 djm 376: match_principals_command(struct ssh *ssh, struct passwd *user_pw,
377: const struct sshkey *key, struct sshauthopt **authoptsp)
1.51 djm 378: {
1.77 djm 379: struct passwd *runas_pw = NULL;
1.56 djm 380: const struct sshkey_cert *cert = key->cert;
1.51 djm 381: FILE *f = NULL;
1.56 djm 382: int r, ok, found_principal = 0;
1.51 djm 383: int i, ac = 0, uid_swapped = 0;
384: pid_t pid;
385: char *tmp, *username = NULL, *command = NULL, **av = NULL;
1.56 djm 386: char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL;
1.78 ! djm 387: char serial_s[16], uidstr[32];
1.51 djm 388: void (*osigchld)(int);
389:
1.77 djm 390: if (authoptsp != NULL)
391: *authoptsp = NULL;
1.51 djm 392: if (options.authorized_principals_command == NULL)
393: return 0;
394: if (options.authorized_principals_command_user == NULL) {
395: error("No user for AuthorizedPrincipalsCommand specified, "
396: "skipping");
397: return 0;
398: }
399:
400: /*
401: * NB. all returns later this function should go via "out" to
402: * ensure the original SIGCHLD handler is restored properly.
403: */
404: osigchld = signal(SIGCHLD, SIG_DFL);
405:
406: /* Prepare and verify the user for the command */
407: username = percent_expand(options.authorized_principals_command_user,
408: "u", user_pw->pw_name, (char *)NULL);
1.77 djm 409: runas_pw = getpwnam(username);
410: if (runas_pw == NULL) {
1.51 djm 411: error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s",
412: username, strerror(errno));
413: goto out;
414: }
415:
416: /* Turn the command into an argument vector */
1.69 djm 417: if (argv_split(options.authorized_principals_command, &ac, &av) != 0) {
1.51 djm 418: error("AuthorizedPrincipalsCommand \"%s\" contains "
419: "invalid quotes", command);
420: goto out;
421: }
422: if (ac == 0) {
423: error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
424: command);
425: goto out;
426: }
1.56 djm 427: if ((ca_fp = sshkey_fingerprint(cert->signature_key,
428: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
429: error("%s: sshkey_fingerprint failed", __func__);
430: goto out;
431: }
1.57 djm 432: if ((key_fp = sshkey_fingerprint(key,
1.56 djm 433: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
434: error("%s: sshkey_fingerprint failed", __func__);
435: goto out;
436: }
437: if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) {
438: error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
439: goto out;
440: }
441: if ((r = sshkey_to_base64(key, &keytext)) != 0) {
442: error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
443: goto out;
444: }
1.59 djm 445: snprintf(serial_s, sizeof(serial_s), "%llu",
446: (unsigned long long)cert->serial);
1.78 ! djm 447: snprintf(uidstr, sizeof(uidstr), "%llu",
! 448: (unsigned long long)user_pw->pw_uid);
1.51 djm 449: for (i = 1; i < ac; i++) {
450: tmp = percent_expand(av[i],
1.78 ! djm 451: "U", uidstr,
1.51 djm 452: "u", user_pw->pw_name,
453: "h", user_pw->pw_dir,
1.56 djm 454: "t", sshkey_ssh_name(key),
455: "T", sshkey_ssh_name(cert->signature_key),
456: "f", key_fp,
457: "F", ca_fp,
458: "k", keytext,
459: "K", catext,
1.58 djm 460: "i", cert->key_id,
461: "s", serial_s,
1.51 djm 462: (char *)NULL);
463: if (tmp == NULL)
464: fatal("%s: percent_expand failed", __func__);
465: free(av[i]);
466: av[i] = tmp;
467: }
468: /* Prepare a printable command for logs, etc. */
1.69 djm 469: command = argv_assemble(ac, av);
1.51 djm 470:
1.77 djm 471: if ((pid = subprocess("AuthorizedPrincipalsCommand", runas_pw, command,
1.69 djm 472: ac, av, &f,
473: SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
1.51 djm 474: goto out;
475:
476: uid_swapped = 1;
1.77 djm 477: temporarily_use_uid(runas_pw);
1.51 djm 478:
1.77 djm 479: ok = process_principals(ssh, f, "(command)", cert, authoptsp);
1.51 djm 480:
1.61 djm 481: fclose(f);
482: f = NULL;
483:
1.70 djm 484: if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0)
1.51 djm 485: goto out;
486:
487: /* Read completed successfully */
488: found_principal = ok;
489: out:
490: if (f != NULL)
491: fclose(f);
492: signal(SIGCHLD, osigchld);
493: for (i = 0; i < ac; i++)
494: free(av[i]);
495: free(av);
496: if (uid_swapped)
497: restore_uid();
498: free(command);
499: free(username);
1.56 djm 500: free(ca_fp);
501: free(key_fp);
502: free(catext);
503: free(keytext);
1.51 djm 504: return found_principal;
505: }
1.77 djm 506:
507: static void
508: skip_space(char **cpp)
509: {
510: char *cp;
511:
512: for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
513: ;
514: *cpp = cp;
515: }
516:
517: /*
518: * Advanced *cpp past the end of key options, defined as the first unquoted
519: * whitespace character. Returns 0 on success or -1 on failure (e.g.
520: * unterminated quotes).
521: */
522: static int
523: advance_past_options(char **cpp)
524: {
525: char *cp = *cpp;
526: int quoted = 0;
527:
528: for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
529: if (*cp == '\\' && cp[1] == '"')
530: cp++; /* Skip both */
531: else if (*cp == '"')
532: quoted = !quoted;
533: }
534: *cpp = cp;
535: /* return failure for unterminated quotes */
536: return (*cp == '\0' && quoted) ? -1 : 0;
537: }
538:
539: /*
540: * Check a single line of an authorized_keys-format file. Returns 0 if key
541: * matches, -1 otherwise. Will return key/cert options via *authoptsp
542: * on success. "loc" is used as file/line location in log messages.
543: */
544: static int
545: check_authkey_line(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
546: char *cp, const char *loc, struct sshauthopt **authoptsp)
547: {
548: int want_keytype = sshkey_is_cert(key) ? KEY_UNSPEC : key->type;
549: struct sshkey *found = NULL;
550: struct sshauthopt *keyopts = NULL, *certopts = NULL, *finalopts = NULL;
551: char *key_options = NULL, *fp = NULL;
552: const char *reason = NULL;
553: int ret = -1;
554:
555: if (authoptsp != NULL)
556: *authoptsp = NULL;
557:
558: if ((found = sshkey_new(want_keytype)) == NULL) {
559: debug3("%s: keytype %d failed", __func__, want_keytype);
560: goto out;
561: }
562:
563: /* XXX djm: peek at key type in line and skip if unwanted */
564:
565: if (sshkey_read(found, &cp) != 0) {
566: /* no key? check for options */
567: debug2("%s: check options: '%s'", loc, cp);
568: key_options = cp;
569: if (advance_past_options(&cp) != 0) {
570: reason = "invalid key option string";
571: goto fail_reason;
572: }
573: skip_space(&cp);
574: if (sshkey_read(found, &cp) != 0) {
575: /* still no key? advance to next line*/
576: debug2("%s: advance: '%s'", loc, cp);
577: goto out;
578: }
579: }
580: /* Parse key options now; we need to know if this is a CA key */
581: if ((keyopts = sshauthopt_parse(key_options, &reason)) == NULL) {
582: debug("%s: bad key options: %s", loc, reason);
583: auth_debug_add("%s: bad key options: %s", loc, reason);
584: goto out;
585: }
586: /* Ignore keys that don't match or incorrectly marked as CAs */
587: if (sshkey_is_cert(key)) {
588: /* Certificate; check signature key against CA */
589: if (!sshkey_equal(found, key->cert->signature_key) ||
590: !keyopts->cert_authority)
591: goto out;
592: } else {
593: /* Plain key: check it against key found in file */
594: if (!sshkey_equal(found, key) || keyopts->cert_authority)
595: goto out;
596: }
597:
598: /* We have a candidate key, perform authorisation checks */
599: if ((fp = sshkey_fingerprint(found,
600: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
601: fatal("%s: fingerprint failed", __func__);
602:
603: debug("%s: matching %s found: %s %s", loc,
604: sshkey_is_cert(key) ? "CA" : "key", sshkey_type(found), fp);
605:
606: if (auth_authorise_keyopts(ssh, pw, keyopts,
607: sshkey_is_cert(key), loc) != 0) {
608: reason = "Refused by key options";
609: goto fail_reason;
610: }
611: /* That's all we need for plain keys. */
612: if (!sshkey_is_cert(key)) {
613: verbose("Accepted key %s %s found at %s",
614: sshkey_type(found), fp, loc);
615: finalopts = keyopts;
616: keyopts = NULL;
617: goto success;
618: }
619:
620: /*
621: * Additional authorisation for certificates.
622: */
623:
624: /* Parse and check options present in certificate */
625: if ((certopts = sshauthopt_from_cert(key)) == NULL) {
626: reason = "Invalid certificate options";
627: goto fail_reason;
628: }
629: if (auth_authorise_keyopts(ssh, pw, certopts, 0, loc) != 0) {
630: reason = "Refused by certificate options";
631: goto fail_reason;
632: }
633: if ((finalopts = sshauthopt_merge(keyopts, certopts, &reason)) == NULL)
634: goto fail_reason;
635:
636: /*
637: * If the user has specified a list of principals as
638: * a key option, then prefer that list to matching
639: * their username in the certificate principals list.
640: */
641: if (keyopts->cert_principals != NULL &&
642: !match_principals_option(keyopts->cert_principals, key->cert)) {
643: reason = "Certificate does not contain an authorized principal";
644: goto fail_reason;
645: }
646: if (sshkey_cert_check_authority(key, 0, 0,
647: keyopts->cert_principals == NULL ? pw->pw_name : NULL, &reason) != 0)
648: goto fail_reason;
649:
650: verbose("Accepted certificate ID \"%s\" (serial %llu) "
651: "signed by CA %s %s found at %s",
652: key->cert->key_id,
653: (unsigned long long)key->cert->serial,
654: sshkey_type(found), fp, loc);
655:
656: success:
657: if (finalopts == NULL)
658: fatal("%s: internal error: missing options", __func__);
659: if (authoptsp != NULL) {
660: *authoptsp = finalopts;
661: finalopts = NULL;
662: }
663: /* success */
664: ret = 0;
665: goto out;
666:
667: fail_reason:
668: error("%s", reason);
669: auth_debug_add("%s", reason);
670: out:
671: free(fp);
672: sshauthopt_free(keyopts);
673: sshauthopt_free(certopts);
674: sshauthopt_free(finalopts);
675: sshkey_free(found);
676: return ret;
677: }
678:
1.51 djm 679: /*
1.31 djm 680: * Checks whether key is allowed in authorized_keys-format file,
681: * returns 1 if the key is allowed or 0 otherwise.
682: */
1.1 markus 683: static int
1.77 djm 684: check_authkeys_file(struct ssh *ssh, struct passwd *pw, FILE *f,
685: char *file, struct sshkey *key, struct sshauthopt **authoptsp)
1.1 markus 686: {
1.77 djm 687: char *cp, line[SSH_MAX_PUBKEY_BYTES], loc[256];
1.18 dtucker 688: int found_key = 0;
1.1 markus 689: u_long linenum = 0;
1.77 djm 690:
691: if (authoptsp != NULL)
692: *authoptsp = NULL;
1.1 markus 693:
1.8 dtucker 694: while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
1.71 djm 695: /* Always consume entire file */
1.62 djm 696: if (found_key)
697: continue;
1.20 djm 698:
1.1 markus 699: /* Skip leading whitespace, empty and comment lines. */
1.77 djm 700: cp = line;
701: skip_space(&cp);
1.1 markus 702: if (!*cp || *cp == '\n' || *cp == '#')
703: continue;
1.77 djm 704: snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
705: if (check_authkey_line(ssh, pw, key, cp, loc, authoptsp) == 0)
1.20 djm 706: found_key = 1;
1.1 markus 707: }
708: return found_key;
709: }
710:
1.21 djm 711: /* Authenticate a certificate key against TrustedUserCAKeys */
712: static int
1.77 djm 713: user_cert_trusted_ca(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
714: struct sshauthopt **authoptsp)
1.21 djm 715: {
1.24 djm 716: char *ca_fp, *principals_file = NULL;
1.21 djm 717: const char *reason;
1.77 djm 718: struct sshauthopt *principals_opts = NULL, *cert_opts = NULL;
719: struct sshauthopt *final_opts = NULL;
1.64 markus 720: int r, ret = 0, found_principal = 0, use_authorized_principals;
1.21 djm 721:
1.77 djm 722: if (authoptsp != NULL)
723: *authoptsp = NULL;
724:
1.64 markus 725: if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL)
1.21 djm 726: return 0;
727:
1.46 djm 728: if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
729: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
730: return 0;
1.21 djm 731:
1.64 markus 732: if ((r = sshkey_in_file(key->cert->signature_key,
733: options.trusted_user_ca_keys, 1, 0)) != 0) {
734: debug2("%s: CA %s %s is not listed in %s: %s", __func__,
735: sshkey_type(key->cert->signature_key), ca_fp,
736: options.trusted_user_ca_keys, ssh_err(r));
1.21 djm 737: goto out;
738: }
1.24 djm 739: /*
740: * If AuthorizedPrincipals is in use, then compare the certificate
741: * principals against the names in that file rather than matching
742: * against the username.
743: */
744: if ((principals_file = authorized_principals_file(pw)) != NULL) {
1.77 djm 745: if (match_principals_file(ssh, pw, principals_file,
746: key->cert, &principals_opts))
1.51 djm 747: found_principal = 1;
748: }
749: /* Try querying command if specified */
1.77 djm 750: if (!found_principal && match_principals_command(ssh, pw, key,
751: &principals_opts))
1.51 djm 752: found_principal = 1;
1.53 jsing 753: /* If principals file or command is specified, then require a match */
754: use_authorized_principals = principals_file != NULL ||
755: options.authorized_principals_command != NULL;
756: if (!found_principal && use_authorized_principals) {
1.51 djm 757: reason = "Certificate does not contain an authorized principal";
1.77 djm 758: goto fail_reason;
1.21 djm 759: }
1.77 djm 760: if (use_authorized_principals && principals_opts == NULL)
761: fatal("%s: internal error: missing principals_opts", __func__);
1.64 markus 762: if (sshkey_cert_check_authority(key, 0, 1,
1.53 jsing 763: use_authorized_principals ? NULL : pw->pw_name, &reason) != 0)
1.24 djm 764: goto fail_reason;
1.77 djm 765:
766: /* Check authority from options in key and from principals file/cmd */
767: if ((cert_opts = sshauthopt_from_cert(key)) == NULL) {
768: reason = "Invalid certificate options";
769: goto fail_reason;
770: }
771: if (auth_authorise_keyopts(ssh, pw, cert_opts, 0, "cert") != 0) {
772: reason = "Refused by certificate options";
1.60 djm 773: goto fail_reason;
1.77 djm 774: }
775: if (principals_opts == NULL) {
776: final_opts = cert_opts;
777: cert_opts = NULL;
778: } else {
779: if (auth_authorise_keyopts(ssh, pw, principals_opts, 0,
780: "principals") != 0) {
781: reason = "Refused by certificate principals options";
782: goto fail_reason;
783: }
784: if ((final_opts = sshauthopt_merge(principals_opts,
785: cert_opts, &reason)) == NULL) {
786: fail_reason:
787: error("%s", reason);
788: auth_debug_add("%s", reason);
789: goto out;
790: }
791: }
1.21 djm 792:
1.77 djm 793: /* Success */
1.54 djm 794: verbose("Accepted certificate ID \"%s\" (serial %llu) signed by "
795: "%s CA %s via %s", key->cert->key_id,
796: (unsigned long long)key->cert->serial,
1.64 markus 797: sshkey_type(key->cert->signature_key), ca_fp,
1.22 djm 798: options.trusted_user_ca_keys);
1.77 djm 799: if (authoptsp != NULL) {
800: *authoptsp = final_opts;
801: final_opts = NULL;
802: }
1.21 djm 803: ret = 1;
804: out:
1.77 djm 805: sshauthopt_free(principals_opts);
806: sshauthopt_free(cert_opts);
807: sshauthopt_free(final_opts);
1.36 djm 808: free(principals_file);
809: free(ca_fp);
1.21 djm 810: return ret;
811: }
812:
1.31 djm 813: /*
814: * Checks whether key is allowed in file.
815: * returns 1 if the key is allowed or 0 otherwise.
816: */
817: static int
1.77 djm 818: user_key_allowed2(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
819: char *file, struct sshauthopt **authoptsp)
1.31 djm 820: {
821: FILE *f;
822: int found_key = 0;
823:
1.77 djm 824: if (authoptsp != NULL)
825: *authoptsp = NULL;
826:
1.31 djm 827: /* Temporarily use the user's uid. */
828: temporarily_use_uid(pw);
829:
830: debug("trying public key file %s", file);
831: if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
1.77 djm 832: found_key = check_authkeys_file(ssh, pw, f, file,
833: key, authoptsp);
1.31 djm 834: fclose(f);
835: }
836:
837: restore_uid();
838: return found_key;
839: }
840:
841: /*
842: * Checks whether key is allowed in output of command.
843: * returns 1 if the key is allowed or 0 otherwise.
844: */
845: static int
1.77 djm 846: user_key_command_allowed2(struct ssh *ssh, struct passwd *user_pw,
847: struct sshkey *key, struct sshauthopt **authoptsp)
1.31 djm 848: {
1.77 djm 849: struct passwd *runas_pw = NULL;
1.50 djm 850: FILE *f = NULL;
851: int r, ok, found_key = 0;
852: int i, uid_swapped = 0, ac = 0;
1.31 djm 853: pid_t pid;
1.50 djm 854: char *username = NULL, *key_fp = NULL, *keytext = NULL;
1.78 ! djm 855: char uidstr[32], *tmp, *command = NULL, **av = NULL;
1.50 djm 856: void (*osigchld)(int);
1.31 djm 857:
1.77 djm 858: if (authoptsp != NULL)
859: *authoptsp = NULL;
1.50 djm 860: if (options.authorized_keys_command == NULL)
1.31 djm 861: return 0;
1.32 djm 862: if (options.authorized_keys_command_user == NULL) {
863: error("No user for AuthorizedKeysCommand specified, skipping");
864: return 0;
865: }
866:
1.50 djm 867: /*
868: * NB. all returns later this function should go via "out" to
869: * ensure the original SIGCHLD handler is restored properly.
870: */
871: osigchld = signal(SIGCHLD, SIG_DFL);
872:
873: /* Prepare and verify the user for the command */
1.32 djm 874: username = percent_expand(options.authorized_keys_command_user,
875: "u", user_pw->pw_name, (char *)NULL);
1.77 djm 876: runas_pw = getpwnam(username);
877: if (runas_pw == NULL) {
1.34 djm 878: error("AuthorizedKeysCommandUser \"%s\" not found: %s",
879: username, strerror(errno));
1.50 djm 880: goto out;
1.31 djm 881: }
882:
1.50 djm 883: /* Prepare AuthorizedKeysCommand */
884: if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash,
885: SSH_FP_DEFAULT)) == NULL) {
886: error("%s: sshkey_fingerprint failed", __func__);
1.31 djm 887: goto out;
888: }
1.50 djm 889: if ((r = sshkey_to_base64(key, &keytext)) != 0) {
890: error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
1.31 djm 891: goto out;
892: }
893:
1.50 djm 894: /* Turn the command into an argument vector */
1.69 djm 895: if (argv_split(options.authorized_keys_command, &ac, &av) != 0) {
1.50 djm 896: error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
897: command);
898: goto out;
899: }
900: if (ac == 0) {
901: error("AuthorizedKeysCommand \"%s\" yielded no arguments",
902: command);
1.31 djm 903: goto out;
904: }
1.78 ! djm 905: snprintf(uidstr, sizeof(uidstr), "%llu",
! 906: (unsigned long long)user_pw->pw_uid);
1.50 djm 907: for (i = 1; i < ac; i++) {
908: tmp = percent_expand(av[i],
1.78 ! djm 909: "U", uidstr,
1.50 djm 910: "u", user_pw->pw_name,
911: "h", user_pw->pw_dir,
912: "t", sshkey_ssh_name(key),
913: "f", key_fp,
914: "k", keytext,
915: (char *)NULL);
916: if (tmp == NULL)
917: fatal("%s: percent_expand failed", __func__);
918: free(av[i]);
919: av[i] = tmp;
920: }
921: /* Prepare a printable command for logs, etc. */
1.69 djm 922: command = argv_assemble(ac, av);
1.31 djm 923:
924: /*
1.50 djm 925: * If AuthorizedKeysCommand was run without arguments
926: * then fall back to the old behaviour of passing the
927: * target username as a single argument.
1.31 djm 928: */
1.50 djm 929: if (ac == 1) {
930: av = xreallocarray(av, ac + 2, sizeof(*av));
931: av[1] = xstrdup(user_pw->pw_name);
932: av[2] = NULL;
933: /* Fix up command too, since it is used in log messages */
934: free(command);
935: xasprintf(&command, "%s %s", av[0], av[1]);
936: }
1.31 djm 937:
1.77 djm 938: if ((pid = subprocess("AuthorizedKeysCommand", runas_pw, command,
1.69 djm 939: ac, av, &f,
940: SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
1.50 djm 941: goto out;
1.31 djm 942:
1.50 djm 943: uid_swapped = 1;
1.77 djm 944: temporarily_use_uid(runas_pw);
1.31 djm 945:
1.77 djm 946: ok = check_authkeys_file(ssh, user_pw, f,
947: options.authorized_keys_command, key, authoptsp);
1.61 djm 948:
949: fclose(f);
950: f = NULL;
1.31 djm 951:
1.70 djm 952: if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0)
1.31 djm 953: goto out;
1.50 djm 954:
955: /* Read completed successfully */
1.31 djm 956: found_key = ok;
957: out:
1.50 djm 958: if (f != NULL)
959: fclose(f);
960: signal(SIGCHLD, osigchld);
961: for (i = 0; i < ac; i++)
962: free(av[i]);
963: free(av);
964: if (uid_swapped)
965: restore_uid();
966: free(command);
967: free(username);
968: free(key_fp);
969: free(keytext);
1.31 djm 970: return found_key;
971: }
972:
973: /*
974: * Check whether key authenticates and authorises the user.
975: */
1.1 markus 976: int
1.77 djm 977: user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
978: int auth_attempt, struct sshauthopt **authoptsp)
1.1 markus 979: {
1.29 djm 980: u_int success, i;
1.1 markus 981: char *file;
1.77 djm 982: struct sshauthopt *opts = NULL;
983: if (authoptsp != NULL)
984: *authoptsp = NULL;
1.21 djm 985:
986: if (auth_key_is_revoked(key))
987: return 0;
1.64 markus 988: if (sshkey_is_cert(key) &&
989: auth_key_is_revoked(key->cert->signature_key))
1.21 djm 990: return 0;
991:
1.77 djm 992: if ((success = user_cert_trusted_ca(ssh, pw, key, &opts)) != 0)
993: goto out;
994: sshauthopt_free(opts);
995: opts = NULL;
996:
997: if ((success = user_key_command_allowed2(ssh, pw, key, &opts)) != 0)
998: goto out;
999: sshauthopt_free(opts);
1000: opts = NULL;
1.31 djm 1001:
1.29 djm 1002: for (i = 0; !success && i < options.num_authkeys_files; i++) {
1.31 djm 1003: if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
1004: continue;
1.29 djm 1005: file = expand_authorized_keys(
1006: options.authorized_keys_files[i], pw);
1.77 djm 1007: success = user_key_allowed2(ssh, pw, key, file, &opts);
1.36 djm 1008: free(file);
1.29 djm 1009: }
1.1 markus 1010:
1.77 djm 1011: out:
1012: if (success && authoptsp != NULL) {
1013: *authoptsp = opts;
1014: opts = NULL;
1015: }
1016: sshauthopt_free(opts);
1.1 markus 1017: return success;
1018: }
1.2 markus 1019:
1020: Authmethod method_pubkey = {
1021: "publickey",
1022: userauth_pubkey,
1023: &options.pubkey_authentication
1024: };
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