Annotation of src/usr.bin/ssh/auth2-pubkey.c, Revision 1.98
1.98 ! dtucker 1: /* $OpenBSD: auth2-pubkey.c,v 1.97 2019/11/25 00:54:23 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:
1.94 djm 30: #include <stdlib.h>
1.31 djm 31: #include <errno.h>
1.16 djm 32: #include <fcntl.h>
1.31 djm 33: #include <paths.h>
1.13 stevesk 34: #include <pwd.h>
1.31 djm 35: #include <signal.h>
1.14 stevesk 36: #include <stdio.h>
1.15 deraadt 37: #include <stdarg.h>
1.20 djm 38: #include <string.h>
39: #include <time.h>
1.17 dtucker 40: #include <unistd.h>
1.44 djm 41: #include <limits.h>
1.1 markus 42:
1.15 deraadt 43: #include "xmalloc.h"
1.8 dtucker 44: #include "ssh.h"
1.1 markus 45: #include "ssh2.h"
46: #include "packet.h"
1.81 markus 47: #include "sshbuf.h"
1.1 markus 48: #include "log.h"
1.41 millert 49: #include "misc.h"
1.1 markus 50: #include "servconf.h"
51: #include "compat.h"
1.64 markus 52: #include "sshkey.h"
1.15 deraadt 53: #include "hostfile.h"
1.1 markus 54: #include "auth.h"
55: #include "pathnames.h"
56: #include "uidswap.h"
57: #include "auth-options.h"
58: #include "canohost.h"
1.15 deraadt 59: #ifdef GSSAPI
60: #include "ssh-gss.h"
61: #endif
1.1 markus 62: #include "monitor_wrap.h"
1.21 djm 63: #include "authfile.h"
1.24 djm 64: #include "match.h"
1.50 djm 65: #include "ssherr.h"
66: #include "channels.h" /* XXX for session.h */
67: #include "session.h" /* XXX for child_set_env(); refactor? */
1.96 djm 68: #include "sk-api.h"
1.1 markus 69:
70: /* import */
71: extern ServerOptions options;
72: extern u_char *session_id2;
1.4 markus 73: extern u_int session_id2_len;
1.1 markus 74:
1.73 djm 75: static char *
76: format_key(const struct sshkey *key)
77: {
78: char *ret, *fp = sshkey_fingerprint(key,
79: options.fingerprint_hash, SSH_FP_DEFAULT);
80:
81: xasprintf(&ret, "%s %s", sshkey_type(key), fp);
82: free(fp);
83: return ret;
84: }
85:
1.2 markus 86: static int
1.65 markus 87: userauth_pubkey(struct ssh *ssh)
1.1 markus 88: {
1.65 markus 89: Authctxt *authctxt = ssh->authctxt;
1.77 djm 90: struct passwd *pw = authctxt->pw;
1.83 djm 91: struct sshbuf *b = NULL;
1.63 markus 92: struct sshkey *key = NULL;
1.83 djm 93: char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL;
94: u_char *pkblob = NULL, *sig = NULL, have_sig;
1.64 markus 95: size_t blen, slen;
96: int r, pktype;
1.96 djm 97: int req_presence = 0, authenticated = 0;
1.77 djm 98: struct sshauthopt *authopts = NULL;
1.95 djm 99: struct sshkey_sig_details *sig_details = NULL;
1.1 markus 100:
1.75 djm 101: if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 ||
102: (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 ||
103: (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0)
104: fatal("%s: parse request failed: %s", __func__, ssh_err(r));
1.87 djm 105:
106: if (log_level_get() >= SYSLOG_LEVEL_DEBUG2) {
107: char *keystring;
108: struct sshbuf *pkbuf;
109:
110: if ((pkbuf = sshbuf_from(pkblob, blen)) == NULL)
111: fatal("%s: sshbuf_from failed", __func__);
1.91 djm 112: if ((keystring = sshbuf_dtob64_string(pkbuf, 0)) == NULL)
1.87 djm 113: fatal("%s: sshbuf_dtob64 failed", __func__);
114: debug2("%s: %s user %s %s public key %s %s", __func__,
115: authctxt->valid ? "valid" : "invalid", authctxt->user,
116: have_sig ? "attempting" : "querying", pkalg, keystring);
117: sshbuf_free(pkbuf);
118: free(keystring);
119: }
120:
1.64 markus 121: pktype = sshkey_type_from_name(pkalg);
1.1 markus 122: if (pktype == KEY_UNSPEC) {
123: /* this is perfectly legal */
1.80 djm 124: verbose("%s: unsupported public key algorithm: %s",
1.55 djm 125: __func__, pkalg);
1.1 markus 126: goto done;
127: }
1.64 markus 128: if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
129: error("%s: could not parse key: %s", __func__, ssh_err(r));
130: goto done;
131: }
1.1 markus 132: if (key == NULL) {
1.55 djm 133: error("%s: cannot decode key: %s", __func__, pkalg);
1.1 markus 134: goto done;
135: }
136: if (key->type != pktype) {
1.55 djm 137: error("%s: type mismatch for decoded key "
138: "(received %d, expected %d)", __func__, key->type, pktype);
1.39 djm 139: goto done;
140: }
1.64 markus 141: if (sshkey_type_plain(key->type) == KEY_RSA &&
142: (ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
1.39 djm 143: logit("Refusing RSA key because client uses unsafe "
144: "signature scheme");
1.1 markus 145: goto done;
146: }
1.68 djm 147: if (auth2_key_already_used(authctxt, key)) {
1.64 markus 148: logit("refusing previously-used %s key", sshkey_type(key));
1.44 djm 149: goto done;
150: }
1.80 djm 151: if (match_pattern_list(pkalg, options.pubkey_key_types, 0) != 1) {
1.45 djm 152: logit("%s: key type %s not in PubkeyAcceptedKeyTypes",
153: __func__, sshkey_ssh_name(key));
154: goto done;
155: }
1.86 djm 156: if ((r = sshkey_check_cert_sigtype(key,
157: options.ca_sign_algorithms)) != 0) {
158: logit("%s: certificate signature algorithm %s: %s", __func__,
159: (key->cert == NULL || key->cert->signature_type == NULL) ?
160: "(null)" : key->cert->signature_type, ssh_err(r));
161: goto done;
162: }
1.73 djm 163: key_s = format_key(key);
164: if (sshkey_is_cert(key))
165: ca_s = format_key(key->cert->signature_key);
166:
1.1 markus 167: if (have_sig) {
1.73 djm 168: debug3("%s: have %s signature for %s%s%s",
169: __func__, pkalg, key_s,
170: ca_s == NULL ? "" : " CA ",
171: ca_s == NULL ? "" : ca_s);
1.64 markus 172: if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 ||
173: (r = sshpkt_get_end(ssh)) != 0)
174: fatal("%s: %s", __func__, ssh_err(r));
175: if ((b = sshbuf_new()) == NULL)
176: fatal("%s: sshbuf_new failed", __func__);
177: if (ssh->compat & SSH_OLD_SESSIONID) {
178: if ((r = sshbuf_put(b, session_id2,
179: session_id2_len)) != 0)
180: fatal("%s: sshbuf_put session id: %s",
181: __func__, ssh_err(r));
1.1 markus 182: } else {
1.64 markus 183: if ((r = sshbuf_put_string(b, session_id2,
184: session_id2_len)) != 0)
185: fatal("%s: sshbuf_put_string session id: %s",
186: __func__, ssh_err(r));
1.1 markus 187: }
1.83 djm 188: if (!authctxt->valid || authctxt->user == NULL) {
189: debug2("%s: disabled because of invalid user",
190: __func__);
191: goto done;
192: }
1.1 markus 193: /* reconstruct packet */
1.35 djm 194: xasprintf(&userstyle, "%s%s%s", authctxt->user,
195: authctxt->style ? ":" : "",
196: authctxt->style ? authctxt->style : "");
1.64 markus 197: if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
198: (r = sshbuf_put_cstring(b, userstyle)) != 0 ||
1.75 djm 199: (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
200: (r = sshbuf_put_cstring(b, "publickey")) != 0 ||
201: (r = sshbuf_put_u8(b, have_sig)) != 0 ||
1.85 mestre 202: (r = sshbuf_put_cstring(b, pkalg)) != 0 ||
1.75 djm 203: (r = sshbuf_put_string(b, pkblob, blen)) != 0)
1.64 markus 204: fatal("%s: build packet failed: %s",
205: __func__, ssh_err(r));
1.1 markus 206: #ifdef DEBUG_PK
1.64 markus 207: sshbuf_dump(b, stderr);
1.1 markus 208: #endif
209: /* test for correct signature */
210: authenticated = 0;
1.77 djm 211: if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) &&
1.80 djm 212: PRIVSEP(sshkey_verify(key, sig, slen,
213: sshbuf_ptr(b), sshbuf_len(b),
214: (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL,
1.95 djm 215: ssh->compat, &sig_details)) == 0) {
1.1 markus 216: authenticated = 1;
1.44 djm 217: }
1.96 djm 218: if (authenticated == 1 && sig_details != NULL) {
219: auth2_record_info(authctxt, "signature count = %u",
220: sig_details->sk_counter);
1.95 djm 221: debug("%s: sk_counter = %u, sk_flags = 0x%02x",
222: __func__, sig_details->sk_counter,
223: sig_details->sk_flags);
1.96 djm 224: req_presence = (options.pubkey_auth_options &
1.97 djm 225: PUBKEYAUTH_TOUCH_REQUIRED) ||
226: !authopts->no_require_user_presence;
1.96 djm 227: if (req_presence && (sig_details->sk_flags &
228: SSH_SK_USER_PRESENCE_REQD) == 0) {
229: error("public key %s signature for %s%s from "
230: "%.128s port %d rejected: user presence "
231: "(key touch) requirement not met ", key_s,
232: authctxt->valid ? "" : "invalid user ",
233: authctxt->user, ssh_remote_ipaddr(ssh),
234: ssh_remote_port(ssh));
235: authenticated = 0;
236: goto done;
237: }
1.95 djm 238: }
1.68 djm 239: auth2_record_key(authctxt, authenticated, key);
1.1 markus 240: } else {
1.73 djm 241: debug("%s: test pkalg %s pkblob %s%s%s",
242: __func__, pkalg, key_s,
243: ca_s == NULL ? "" : " CA ",
244: ca_s == NULL ? "" : ca_s);
245:
1.64 markus 246: if ((r = sshpkt_get_end(ssh)) != 0)
247: fatal("%s: %s", __func__, ssh_err(r));
1.1 markus 248:
1.83 djm 249: if (!authctxt->valid || authctxt->user == NULL) {
250: debug2("%s: disabled because of invalid user",
251: __func__);
252: goto done;
253: }
1.1 markus 254: /* XXX fake reply and always send PK_OK ? */
255: /*
256: * XXX this allows testing whether a user is allowed
257: * to login: if you happen to have a valid pubkey this
258: * message is sent. the message is NEVER sent at all
259: * if a user is not allowed to login. is this an
260: * issue? -markus
261: */
1.77 djm 262: if (PRIVSEP(user_key_allowed(ssh, pw, key, 0, NULL))) {
1.64 markus 263: if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK))
264: != 0 ||
265: (r = sshpkt_put_cstring(ssh, pkalg)) != 0 ||
266: (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 ||
1.82 markus 267: (r = sshpkt_send(ssh)) != 0 ||
268: (r = ssh_packet_write_wait(ssh)) != 0)
1.64 markus 269: fatal("%s: %s", __func__, ssh_err(r));
1.1 markus 270: authctxt->postponed = 1;
271: }
272: }
273: done:
1.77 djm 274: if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) {
275: debug("%s: key options inconsistent with existing", __func__);
276: authenticated = 0;
277: }
1.55 djm 278: debug2("%s: authenticated %d pkalg %s", __func__, authenticated, pkalg);
1.77 djm 279:
1.84 djm 280: sshbuf_free(b);
1.77 djm 281: sshauthopt_free(authopts);
1.68 djm 282: sshkey_free(key);
1.64 markus 283: free(userstyle);
1.36 djm 284: free(pkalg);
285: free(pkblob);
1.73 djm 286: free(key_s);
287: free(ca_s);
1.83 djm 288: free(sig);
1.95 djm 289: sshkey_sig_details_free(sig_details);
1.1 markus 290: return authenticated;
291: }
292:
1.24 djm 293: static int
1.40 djm 294: match_principals_option(const char *principal_list, struct sshkey_cert *cert)
1.24 djm 295: {
296: char *result;
297: u_int i;
298:
299: /* XXX percent_expand() sequences for authorized_principals? */
300:
301: for (i = 0; i < cert->nprincipals; i++) {
302: if ((result = match_list(cert->principals[i],
303: principal_list, NULL)) != NULL) {
304: debug3("matched principal from key options \"%.100s\"",
305: result);
1.36 djm 306: free(result);
1.24 djm 307: return 1;
308: }
309: }
310: return 0;
311: }
312:
1.77 djm 313: /*
314: * Process a single authorized_principals format line. Returns 0 and sets
315: * authoptsp is principal is authorised, -1 otherwise. "loc" is used as a
316: * log preamble for file/line information.
317: */
1.24 djm 318: static int
1.77 djm 319: check_principals_line(struct ssh *ssh, char *cp, const struct sshkey_cert *cert,
320: const char *loc, struct sshauthopt **authoptsp)
1.24 djm 321: {
1.77 djm 322: u_int i, found = 0;
323: char *ep, *line_opts;
324: const char *reason = NULL;
325: struct sshauthopt *opts = NULL;
326:
327: if (authoptsp != NULL)
328: *authoptsp = NULL;
329:
330: /* Trim trailing whitespace. */
331: ep = cp + strlen(cp) - 1;
332: while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t'))
333: *ep-- = '\0';
334:
335: /*
336: * If the line has internal whitespace then assume it has
337: * key options.
338: */
339: line_opts = NULL;
340: if ((ep = strrchr(cp, ' ')) != NULL ||
341: (ep = strrchr(cp, '\t')) != NULL) {
342: for (; *ep == ' ' || *ep == '\t'; ep++)
343: ;
344: line_opts = cp;
345: cp = ep;
346: }
347: if ((opts = sshauthopt_parse(line_opts, &reason)) == NULL) {
348: debug("%s: bad principals options: %s", loc, reason);
349: auth_debug_add("%s: bad principals options: %s", loc, reason);
350: return -1;
351: }
352: /* Check principals in cert against those on line */
353: for (i = 0; i < cert->nprincipals; i++) {
354: if (strcmp(cp, cert->principals[i]) != 0)
355: continue;
356: debug3("%s: matched principal \"%.100s\"",
357: loc, cert->principals[i]);
358: found = 1;
359: }
360: if (found && authoptsp != NULL) {
361: *authoptsp = opts;
362: opts = NULL;
363: }
364: sshauthopt_free(opts);
365: return found ? 0 : -1;
366: }
367:
368: static int
369: process_principals(struct ssh *ssh, FILE *f, const char *file,
370: const struct sshkey_cert *cert, struct sshauthopt **authoptsp)
371: {
1.79 markus 372: char loc[256], *line = NULL, *cp, *ep;
373: size_t linesize = 0;
1.24 djm 374: u_long linenum = 0;
1.77 djm 375: u_int found_principal = 0;
376:
377: if (authoptsp != NULL)
378: *authoptsp = NULL;
1.24 djm 379:
1.79 markus 380: while (getline(&line, &linesize, f) != -1) {
381: linenum++;
1.62 djm 382: /* Always consume entire input */
383: if (found_principal)
384: continue;
1.77 djm 385:
1.26 djm 386: /* Skip leading whitespace. */
1.24 djm 387: for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
388: ;
1.26 djm 389: /* Skip blank and comment lines. */
390: if ((ep = strchr(cp, '#')) != NULL)
391: *ep = '\0';
392: if (!*cp || *cp == '\n')
1.24 djm 393: continue;
1.77 djm 394:
395: snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
396: if (check_principals_line(ssh, cp, cert, loc, authoptsp) == 0)
397: found_principal = 1;
1.24 djm 398: }
1.79 markus 399: free(line);
1.62 djm 400: return found_principal;
1.51 djm 401: }
402:
1.77 djm 403: /* XXX remove pw args here and elsewhere once ssh->authctxt is guaranteed */
404:
1.51 djm 405: static int
1.77 djm 406: match_principals_file(struct ssh *ssh, struct passwd *pw, char *file,
407: struct sshkey_cert *cert, struct sshauthopt **authoptsp)
1.51 djm 408: {
409: FILE *f;
410: int success;
411:
1.77 djm 412: if (authoptsp != NULL)
413: *authoptsp = NULL;
414:
1.51 djm 415: temporarily_use_uid(pw);
416: debug("trying authorized principals file %s", file);
417: if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
418: restore_uid();
419: return 0;
420: }
1.77 djm 421: success = process_principals(ssh, f, file, cert, authoptsp);
1.24 djm 422: fclose(f);
423: restore_uid();
1.51 djm 424: return success;
1.31 djm 425: }
1.24 djm 426:
1.31 djm 427: /*
1.51 djm 428: * Checks whether principal is allowed in output of command.
429: * returns 1 if the principal is allowed or 0 otherwise.
430: */
431: static int
1.77 djm 432: match_principals_command(struct ssh *ssh, struct passwd *user_pw,
433: const struct sshkey *key, struct sshauthopt **authoptsp)
1.51 djm 434: {
1.77 djm 435: struct passwd *runas_pw = NULL;
1.56 djm 436: const struct sshkey_cert *cert = key->cert;
1.51 djm 437: FILE *f = NULL;
1.56 djm 438: int r, ok, found_principal = 0;
1.51 djm 439: int i, ac = 0, uid_swapped = 0;
440: pid_t pid;
441: char *tmp, *username = NULL, *command = NULL, **av = NULL;
1.56 djm 442: char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL;
1.88 djm 443: char serial_s[32], uidstr[32];
1.51 djm 444: void (*osigchld)(int);
445:
1.77 djm 446: if (authoptsp != NULL)
447: *authoptsp = NULL;
1.51 djm 448: if (options.authorized_principals_command == NULL)
449: return 0;
450: if (options.authorized_principals_command_user == NULL) {
451: error("No user for AuthorizedPrincipalsCommand specified, "
452: "skipping");
453: return 0;
454: }
455:
456: /*
457: * NB. all returns later this function should go via "out" to
458: * ensure the original SIGCHLD handler is restored properly.
459: */
1.98 ! dtucker 460: osigchld = ssh_signal(SIGCHLD, SIG_DFL);
1.51 djm 461:
462: /* Prepare and verify the user for the command */
463: username = percent_expand(options.authorized_principals_command_user,
464: "u", user_pw->pw_name, (char *)NULL);
1.77 djm 465: runas_pw = getpwnam(username);
466: if (runas_pw == NULL) {
1.51 djm 467: error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s",
468: username, strerror(errno));
469: goto out;
470: }
471:
472: /* Turn the command into an argument vector */
1.69 djm 473: if (argv_split(options.authorized_principals_command, &ac, &av) != 0) {
1.51 djm 474: error("AuthorizedPrincipalsCommand \"%s\" contains "
1.90 djm 475: "invalid quotes", options.authorized_principals_command);
1.51 djm 476: goto out;
477: }
478: if (ac == 0) {
479: error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
1.90 djm 480: options.authorized_principals_command);
1.51 djm 481: goto out;
482: }
1.56 djm 483: if ((ca_fp = sshkey_fingerprint(cert->signature_key,
484: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
485: error("%s: sshkey_fingerprint failed", __func__);
486: goto out;
487: }
1.57 djm 488: if ((key_fp = sshkey_fingerprint(key,
1.56 djm 489: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
490: error("%s: sshkey_fingerprint failed", __func__);
491: goto out;
492: }
493: if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) {
494: error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
495: goto out;
496: }
497: if ((r = sshkey_to_base64(key, &keytext)) != 0) {
498: error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
499: goto out;
500: }
1.59 djm 501: snprintf(serial_s, sizeof(serial_s), "%llu",
502: (unsigned long long)cert->serial);
1.78 djm 503: snprintf(uidstr, sizeof(uidstr), "%llu",
504: (unsigned long long)user_pw->pw_uid);
1.51 djm 505: for (i = 1; i < ac; i++) {
506: tmp = percent_expand(av[i],
1.78 djm 507: "U", uidstr,
1.51 djm 508: "u", user_pw->pw_name,
509: "h", user_pw->pw_dir,
1.56 djm 510: "t", sshkey_ssh_name(key),
511: "T", sshkey_ssh_name(cert->signature_key),
512: "f", key_fp,
513: "F", ca_fp,
514: "k", keytext,
515: "K", catext,
1.58 djm 516: "i", cert->key_id,
517: "s", serial_s,
1.51 djm 518: (char *)NULL);
519: if (tmp == NULL)
520: fatal("%s: percent_expand failed", __func__);
521: free(av[i]);
522: av[i] = tmp;
523: }
524: /* Prepare a printable command for logs, etc. */
1.69 djm 525: command = argv_assemble(ac, av);
1.51 djm 526:
1.77 djm 527: if ((pid = subprocess("AuthorizedPrincipalsCommand", runas_pw, command,
1.69 djm 528: ac, av, &f,
529: SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
1.51 djm 530: goto out;
531:
532: uid_swapped = 1;
1.77 djm 533: temporarily_use_uid(runas_pw);
1.51 djm 534:
1.77 djm 535: ok = process_principals(ssh, f, "(command)", cert, authoptsp);
1.51 djm 536:
1.61 djm 537: fclose(f);
538: f = NULL;
539:
1.70 djm 540: if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0)
1.51 djm 541: goto out;
542:
543: /* Read completed successfully */
544: found_principal = ok;
545: out:
546: if (f != NULL)
547: fclose(f);
1.98 ! dtucker 548: ssh_signal(SIGCHLD, osigchld);
1.51 djm 549: for (i = 0; i < ac; i++)
550: free(av[i]);
551: free(av);
552: if (uid_swapped)
553: restore_uid();
554: free(command);
555: free(username);
1.56 djm 556: free(ca_fp);
557: free(key_fp);
558: free(catext);
559: free(keytext);
1.51 djm 560: return found_principal;
1.77 djm 561: }
562:
563: /*
564: * Check a single line of an authorized_keys-format file. Returns 0 if key
565: * matches, -1 otherwise. Will return key/cert options via *authoptsp
566: * on success. "loc" is used as file/line location in log messages.
567: */
568: static int
569: check_authkey_line(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
570: char *cp, const char *loc, struct sshauthopt **authoptsp)
571: {
572: int want_keytype = sshkey_is_cert(key) ? KEY_UNSPEC : key->type;
573: struct sshkey *found = NULL;
574: struct sshauthopt *keyopts = NULL, *certopts = NULL, *finalopts = NULL;
575: char *key_options = NULL, *fp = NULL;
576: const char *reason = NULL;
577: int ret = -1;
578:
579: if (authoptsp != NULL)
580: *authoptsp = NULL;
581:
582: if ((found = sshkey_new(want_keytype)) == NULL) {
583: debug3("%s: keytype %d failed", __func__, want_keytype);
584: goto out;
585: }
586:
587: /* XXX djm: peek at key type in line and skip if unwanted */
588:
589: if (sshkey_read(found, &cp) != 0) {
590: /* no key? check for options */
591: debug2("%s: check options: '%s'", loc, cp);
592: key_options = cp;
1.93 djm 593: if (sshkey_advance_past_options(&cp) != 0) {
1.77 djm 594: reason = "invalid key option string";
595: goto fail_reason;
596: }
597: skip_space(&cp);
598: if (sshkey_read(found, &cp) != 0) {
599: /* still no key? advance to next line*/
600: debug2("%s: advance: '%s'", loc, cp);
601: goto out;
602: }
603: }
604: /* Parse key options now; we need to know if this is a CA key */
605: if ((keyopts = sshauthopt_parse(key_options, &reason)) == NULL) {
606: debug("%s: bad key options: %s", loc, reason);
607: auth_debug_add("%s: bad key options: %s", loc, reason);
608: goto out;
609: }
610: /* Ignore keys that don't match or incorrectly marked as CAs */
611: if (sshkey_is_cert(key)) {
612: /* Certificate; check signature key against CA */
613: if (!sshkey_equal(found, key->cert->signature_key) ||
614: !keyopts->cert_authority)
615: goto out;
616: } else {
617: /* Plain key: check it against key found in file */
618: if (!sshkey_equal(found, key) || keyopts->cert_authority)
619: goto out;
620: }
621:
622: /* We have a candidate key, perform authorisation checks */
623: if ((fp = sshkey_fingerprint(found,
624: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
625: fatal("%s: fingerprint failed", __func__);
626:
627: debug("%s: matching %s found: %s %s", loc,
628: sshkey_is_cert(key) ? "CA" : "key", sshkey_type(found), fp);
629:
630: if (auth_authorise_keyopts(ssh, pw, keyopts,
631: sshkey_is_cert(key), loc) != 0) {
632: reason = "Refused by key options";
633: goto fail_reason;
634: }
635: /* That's all we need for plain keys. */
636: if (!sshkey_is_cert(key)) {
637: verbose("Accepted key %s %s found at %s",
638: sshkey_type(found), fp, loc);
639: finalopts = keyopts;
640: keyopts = NULL;
641: goto success;
642: }
643:
644: /*
645: * Additional authorisation for certificates.
646: */
647:
648: /* Parse and check options present in certificate */
649: if ((certopts = sshauthopt_from_cert(key)) == NULL) {
650: reason = "Invalid certificate options";
651: goto fail_reason;
652: }
653: if (auth_authorise_keyopts(ssh, pw, certopts, 0, loc) != 0) {
654: reason = "Refused by certificate options";
655: goto fail_reason;
656: }
657: if ((finalopts = sshauthopt_merge(keyopts, certopts, &reason)) == NULL)
658: goto fail_reason;
659:
660: /*
661: * If the user has specified a list of principals as
662: * a key option, then prefer that list to matching
663: * their username in the certificate principals list.
664: */
665: if (keyopts->cert_principals != NULL &&
666: !match_principals_option(keyopts->cert_principals, key->cert)) {
667: reason = "Certificate does not contain an authorized principal";
668: goto fail_reason;
669: }
670: if (sshkey_cert_check_authority(key, 0, 0,
671: keyopts->cert_principals == NULL ? pw->pw_name : NULL, &reason) != 0)
672: goto fail_reason;
673:
674: verbose("Accepted certificate ID \"%s\" (serial %llu) "
675: "signed by CA %s %s found at %s",
676: key->cert->key_id,
677: (unsigned long long)key->cert->serial,
678: sshkey_type(found), fp, loc);
679:
680: success:
681: if (finalopts == NULL)
682: fatal("%s: internal error: missing options", __func__);
683: if (authoptsp != NULL) {
684: *authoptsp = finalopts;
685: finalopts = NULL;
686: }
687: /* success */
688: ret = 0;
689: goto out;
690:
691: fail_reason:
692: error("%s", reason);
693: auth_debug_add("%s", reason);
694: out:
695: free(fp);
696: sshauthopt_free(keyopts);
697: sshauthopt_free(certopts);
698: sshauthopt_free(finalopts);
699: sshkey_free(found);
700: return ret;
701: }
702:
1.51 djm 703: /*
1.31 djm 704: * Checks whether key is allowed in authorized_keys-format file,
705: * returns 1 if the key is allowed or 0 otherwise.
706: */
1.1 markus 707: static int
1.77 djm 708: check_authkeys_file(struct ssh *ssh, struct passwd *pw, FILE *f,
709: char *file, struct sshkey *key, struct sshauthopt **authoptsp)
1.1 markus 710: {
1.79 markus 711: char *cp, *line = NULL, loc[256];
712: size_t linesize = 0;
1.18 dtucker 713: int found_key = 0;
1.1 markus 714: u_long linenum = 0;
1.77 djm 715:
716: if (authoptsp != NULL)
717: *authoptsp = NULL;
1.1 markus 718:
1.79 markus 719: while (getline(&line, &linesize, f) != -1) {
720: linenum++;
1.71 djm 721: /* Always consume entire file */
1.62 djm 722: if (found_key)
723: continue;
1.20 djm 724:
1.1 markus 725: /* Skip leading whitespace, empty and comment lines. */
1.77 djm 726: cp = line;
727: skip_space(&cp);
1.1 markus 728: if (!*cp || *cp == '\n' || *cp == '#')
729: continue;
1.77 djm 730: snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
731: if (check_authkey_line(ssh, pw, key, cp, loc, authoptsp) == 0)
1.20 djm 732: found_key = 1;
1.1 markus 733: }
1.79 markus 734: free(line);
1.1 markus 735: return found_key;
736: }
737:
1.21 djm 738: /* Authenticate a certificate key against TrustedUserCAKeys */
739: static int
1.77 djm 740: user_cert_trusted_ca(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
741: struct sshauthopt **authoptsp)
1.21 djm 742: {
1.24 djm 743: char *ca_fp, *principals_file = NULL;
1.21 djm 744: const char *reason;
1.77 djm 745: struct sshauthopt *principals_opts = NULL, *cert_opts = NULL;
746: struct sshauthopt *final_opts = NULL;
1.64 markus 747: int r, ret = 0, found_principal = 0, use_authorized_principals;
1.21 djm 748:
1.77 djm 749: if (authoptsp != NULL)
750: *authoptsp = NULL;
751:
1.64 markus 752: if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL)
1.21 djm 753: return 0;
754:
1.46 djm 755: if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
756: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
757: return 0;
1.21 djm 758:
1.64 markus 759: if ((r = sshkey_in_file(key->cert->signature_key,
760: options.trusted_user_ca_keys, 1, 0)) != 0) {
761: debug2("%s: CA %s %s is not listed in %s: %s", __func__,
762: sshkey_type(key->cert->signature_key), ca_fp,
763: options.trusted_user_ca_keys, ssh_err(r));
1.21 djm 764: goto out;
765: }
1.24 djm 766: /*
767: * If AuthorizedPrincipals is in use, then compare the certificate
768: * principals against the names in that file rather than matching
769: * against the username.
770: */
771: if ((principals_file = authorized_principals_file(pw)) != NULL) {
1.77 djm 772: if (match_principals_file(ssh, pw, principals_file,
773: key->cert, &principals_opts))
1.51 djm 774: found_principal = 1;
775: }
776: /* Try querying command if specified */
1.77 djm 777: if (!found_principal && match_principals_command(ssh, pw, key,
778: &principals_opts))
1.51 djm 779: found_principal = 1;
1.53 jsing 780: /* If principals file or command is specified, then require a match */
781: use_authorized_principals = principals_file != NULL ||
782: options.authorized_principals_command != NULL;
783: if (!found_principal && use_authorized_principals) {
1.51 djm 784: reason = "Certificate does not contain an authorized principal";
1.77 djm 785: goto fail_reason;
1.21 djm 786: }
1.77 djm 787: if (use_authorized_principals && principals_opts == NULL)
788: fatal("%s: internal error: missing principals_opts", __func__);
1.64 markus 789: if (sshkey_cert_check_authority(key, 0, 1,
1.53 jsing 790: use_authorized_principals ? NULL : pw->pw_name, &reason) != 0)
1.24 djm 791: goto fail_reason;
1.77 djm 792:
793: /* Check authority from options in key and from principals file/cmd */
794: if ((cert_opts = sshauthopt_from_cert(key)) == NULL) {
795: reason = "Invalid certificate options";
796: goto fail_reason;
797: }
798: if (auth_authorise_keyopts(ssh, pw, cert_opts, 0, "cert") != 0) {
799: reason = "Refused by certificate options";
1.60 djm 800: goto fail_reason;
1.77 djm 801: }
802: if (principals_opts == NULL) {
803: final_opts = cert_opts;
804: cert_opts = NULL;
805: } else {
806: if (auth_authorise_keyopts(ssh, pw, principals_opts, 0,
807: "principals") != 0) {
808: reason = "Refused by certificate principals options";
809: goto fail_reason;
810: }
811: if ((final_opts = sshauthopt_merge(principals_opts,
812: cert_opts, &reason)) == NULL) {
813: fail_reason:
814: error("%s", reason);
815: auth_debug_add("%s", reason);
816: goto out;
817: }
818: }
1.21 djm 819:
1.77 djm 820: /* Success */
1.54 djm 821: verbose("Accepted certificate ID \"%s\" (serial %llu) signed by "
822: "%s CA %s via %s", key->cert->key_id,
823: (unsigned long long)key->cert->serial,
1.64 markus 824: sshkey_type(key->cert->signature_key), ca_fp,
1.22 djm 825: options.trusted_user_ca_keys);
1.77 djm 826: if (authoptsp != NULL) {
827: *authoptsp = final_opts;
828: final_opts = NULL;
829: }
1.21 djm 830: ret = 1;
831: out:
1.77 djm 832: sshauthopt_free(principals_opts);
833: sshauthopt_free(cert_opts);
834: sshauthopt_free(final_opts);
1.36 djm 835: free(principals_file);
836: free(ca_fp);
1.21 djm 837: return ret;
838: }
839:
1.31 djm 840: /*
841: * Checks whether key is allowed in file.
842: * returns 1 if the key is allowed or 0 otherwise.
843: */
844: static int
1.77 djm 845: user_key_allowed2(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
846: char *file, struct sshauthopt **authoptsp)
1.31 djm 847: {
848: FILE *f;
849: int found_key = 0;
850:
1.77 djm 851: if (authoptsp != NULL)
852: *authoptsp = NULL;
853:
1.31 djm 854: /* Temporarily use the user's uid. */
855: temporarily_use_uid(pw);
856:
857: debug("trying public key file %s", file);
858: if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
1.77 djm 859: found_key = check_authkeys_file(ssh, pw, f, file,
860: key, authoptsp);
1.31 djm 861: fclose(f);
862: }
863:
864: restore_uid();
865: return found_key;
866: }
867:
868: /*
869: * Checks whether key is allowed in output of command.
870: * returns 1 if the key is allowed or 0 otherwise.
871: */
872: static int
1.77 djm 873: user_key_command_allowed2(struct ssh *ssh, struct passwd *user_pw,
874: struct sshkey *key, struct sshauthopt **authoptsp)
1.31 djm 875: {
1.77 djm 876: struct passwd *runas_pw = NULL;
1.50 djm 877: FILE *f = NULL;
878: int r, ok, found_key = 0;
879: int i, uid_swapped = 0, ac = 0;
1.31 djm 880: pid_t pid;
1.50 djm 881: char *username = NULL, *key_fp = NULL, *keytext = NULL;
1.78 djm 882: char uidstr[32], *tmp, *command = NULL, **av = NULL;
1.50 djm 883: void (*osigchld)(int);
1.31 djm 884:
1.77 djm 885: if (authoptsp != NULL)
886: *authoptsp = NULL;
1.50 djm 887: if (options.authorized_keys_command == NULL)
1.31 djm 888: return 0;
1.32 djm 889: if (options.authorized_keys_command_user == NULL) {
890: error("No user for AuthorizedKeysCommand specified, skipping");
891: return 0;
892: }
893:
1.50 djm 894: /*
895: * NB. all returns later this function should go via "out" to
896: * ensure the original SIGCHLD handler is restored properly.
897: */
1.98 ! dtucker 898: osigchld = ssh_signal(SIGCHLD, SIG_DFL);
1.50 djm 899:
900: /* Prepare and verify the user for the command */
1.32 djm 901: username = percent_expand(options.authorized_keys_command_user,
902: "u", user_pw->pw_name, (char *)NULL);
1.77 djm 903: runas_pw = getpwnam(username);
904: if (runas_pw == NULL) {
1.34 djm 905: error("AuthorizedKeysCommandUser \"%s\" not found: %s",
906: username, strerror(errno));
1.50 djm 907: goto out;
1.31 djm 908: }
909:
1.50 djm 910: /* Prepare AuthorizedKeysCommand */
911: if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash,
912: SSH_FP_DEFAULT)) == NULL) {
913: error("%s: sshkey_fingerprint failed", __func__);
1.31 djm 914: goto out;
915: }
1.50 djm 916: if ((r = sshkey_to_base64(key, &keytext)) != 0) {
917: error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
1.31 djm 918: goto out;
919: }
920:
1.50 djm 921: /* Turn the command into an argument vector */
1.69 djm 922: if (argv_split(options.authorized_keys_command, &ac, &av) != 0) {
1.50 djm 923: error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
924: command);
925: goto out;
926: }
927: if (ac == 0) {
928: error("AuthorizedKeysCommand \"%s\" yielded no arguments",
929: command);
1.31 djm 930: goto out;
931: }
1.78 djm 932: snprintf(uidstr, sizeof(uidstr), "%llu",
933: (unsigned long long)user_pw->pw_uid);
1.50 djm 934: for (i = 1; i < ac; i++) {
935: tmp = percent_expand(av[i],
1.78 djm 936: "U", uidstr,
1.50 djm 937: "u", user_pw->pw_name,
938: "h", user_pw->pw_dir,
939: "t", sshkey_ssh_name(key),
940: "f", key_fp,
941: "k", keytext,
942: (char *)NULL);
943: if (tmp == NULL)
944: fatal("%s: percent_expand failed", __func__);
945: free(av[i]);
946: av[i] = tmp;
947: }
948: /* Prepare a printable command for logs, etc. */
1.69 djm 949: command = argv_assemble(ac, av);
1.31 djm 950:
951: /*
1.50 djm 952: * If AuthorizedKeysCommand was run without arguments
953: * then fall back to the old behaviour of passing the
954: * target username as a single argument.
1.31 djm 955: */
1.50 djm 956: if (ac == 1) {
957: av = xreallocarray(av, ac + 2, sizeof(*av));
958: av[1] = xstrdup(user_pw->pw_name);
959: av[2] = NULL;
960: /* Fix up command too, since it is used in log messages */
961: free(command);
962: xasprintf(&command, "%s %s", av[0], av[1]);
963: }
1.31 djm 964:
1.77 djm 965: if ((pid = subprocess("AuthorizedKeysCommand", runas_pw, command,
1.69 djm 966: ac, av, &f,
967: SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
1.50 djm 968: goto out;
1.31 djm 969:
1.50 djm 970: uid_swapped = 1;
1.77 djm 971: temporarily_use_uid(runas_pw);
1.31 djm 972:
1.77 djm 973: ok = check_authkeys_file(ssh, user_pw, f,
974: options.authorized_keys_command, key, authoptsp);
1.61 djm 975:
976: fclose(f);
977: f = NULL;
1.31 djm 978:
1.70 djm 979: if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0)
1.31 djm 980: goto out;
1.50 djm 981:
982: /* Read completed successfully */
1.31 djm 983: found_key = ok;
984: out:
1.50 djm 985: if (f != NULL)
986: fclose(f);
1.98 ! dtucker 987: ssh_signal(SIGCHLD, osigchld);
1.50 djm 988: for (i = 0; i < ac; i++)
989: free(av[i]);
990: free(av);
991: if (uid_swapped)
992: restore_uid();
993: free(command);
994: free(username);
995: free(key_fp);
996: free(keytext);
1.31 djm 997: return found_key;
998: }
999:
1000: /*
1001: * Check whether key authenticates and authorises the user.
1002: */
1.1 markus 1003: int
1.77 djm 1004: user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
1005: int auth_attempt, struct sshauthopt **authoptsp)
1.1 markus 1006: {
1.89 djm 1007: u_int success = 0, i;
1.1 markus 1008: char *file;
1.77 djm 1009: struct sshauthopt *opts = NULL;
1.89 djm 1010:
1.77 djm 1011: if (authoptsp != NULL)
1012: *authoptsp = NULL;
1.21 djm 1013:
1014: if (auth_key_is_revoked(key))
1015: return 0;
1.64 markus 1016: if (sshkey_is_cert(key) &&
1017: auth_key_is_revoked(key->cert->signature_key))
1.21 djm 1018: return 0;
1019:
1.89 djm 1020: for (i = 0; !success && i < options.num_authkeys_files; i++) {
1021: if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
1022: continue;
1023: file = expand_authorized_keys(
1024: options.authorized_keys_files[i], pw);
1025: success = user_key_allowed2(ssh, pw, key, file, &opts);
1026: free(file);
1027: if (!success) {
1028: sshauthopt_free(opts);
1029: opts = NULL;
1030: }
1031: }
1032: if (success)
1033: goto out;
1034:
1.77 djm 1035: if ((success = user_cert_trusted_ca(ssh, pw, key, &opts)) != 0)
1036: goto out;
1037: sshauthopt_free(opts);
1038: opts = NULL;
1039:
1040: if ((success = user_key_command_allowed2(ssh, pw, key, &opts)) != 0)
1041: goto out;
1042: sshauthopt_free(opts);
1043: opts = NULL;
1.1 markus 1044:
1.77 djm 1045: out:
1046: if (success && authoptsp != NULL) {
1047: *authoptsp = opts;
1048: opts = NULL;
1049: }
1050: sshauthopt_free(opts);
1.1 markus 1051: return success;
1052: }
1.2 markus 1053:
1054: Authmethod method_pubkey = {
1055: "publickey",
1056: userauth_pubkey,
1057: &options.pubkey_authentication
1058: };
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