Annotation of src/usr.bin/ssh/auth2-pubkey.c, Revision 1.106
1.106 ! djm 1: /* $OpenBSD: auth2-pubkey.c,v 1.105 2021/01/26 00:49:30 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"
1.106 ! djm 47: #include "kex.h"
1.81 markus 48: #include "sshbuf.h"
1.1 markus 49: #include "log.h"
1.41 millert 50: #include "misc.h"
1.1 markus 51: #include "servconf.h"
52: #include "compat.h"
1.64 markus 53: #include "sshkey.h"
1.15 deraadt 54: #include "hostfile.h"
1.1 markus 55: #include "auth.h"
56: #include "pathnames.h"
57: #include "uidswap.h"
58: #include "auth-options.h"
59: #include "canohost.h"
1.15 deraadt 60: #ifdef GSSAPI
61: #include "ssh-gss.h"
62: #endif
1.1 markus 63: #include "monitor_wrap.h"
1.21 djm 64: #include "authfile.h"
1.24 djm 65: #include "match.h"
1.50 djm 66: #include "ssherr.h"
67: #include "channels.h" /* XXX for session.h */
68: #include "session.h" /* XXX for child_set_env(); refactor? */
1.96 djm 69: #include "sk-api.h"
1.1 markus 70:
71: /* import */
72: extern ServerOptions options;
73:
1.73 djm 74: static char *
75: format_key(const struct sshkey *key)
76: {
77: char *ret, *fp = sshkey_fingerprint(key,
78: options.fingerprint_hash, SSH_FP_DEFAULT);
79:
80: xasprintf(&ret, "%s %s", sshkey_type(key), fp);
81: free(fp);
82: return ret;
83: }
84:
1.2 markus 85: static int
1.65 markus 86: userauth_pubkey(struct ssh *ssh)
1.1 markus 87: {
1.65 markus 88: Authctxt *authctxt = ssh->authctxt;
1.77 djm 89: struct passwd *pw = authctxt->pw;
1.83 djm 90: struct sshbuf *b = NULL;
1.63 markus 91: struct sshkey *key = NULL;
1.83 djm 92: char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL;
93: u_char *pkblob = NULL, *sig = NULL, have_sig;
1.64 markus 94: size_t blen, slen;
95: int r, pktype;
1.100 djm 96: int req_presence = 0, req_verify = 0, authenticated = 0;
1.77 djm 97: struct sshauthopt *authopts = NULL;
1.95 djm 98: struct sshkey_sig_details *sig_details = NULL;
1.1 markus 99:
1.75 djm 100: if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 ||
101: (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 ||
102: (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0)
1.101 djm 103: fatal_fr(r, "parse packet");
1.87 djm 104:
105: if (log_level_get() >= SYSLOG_LEVEL_DEBUG2) {
106: char *keystring;
107: struct sshbuf *pkbuf;
108:
109: if ((pkbuf = sshbuf_from(pkblob, blen)) == NULL)
1.101 djm 110: fatal_f("sshbuf_from failed");
1.91 djm 111: if ((keystring = sshbuf_dtob64_string(pkbuf, 0)) == NULL)
1.101 djm 112: fatal_f("sshbuf_dtob64 failed");
113: debug2_f("%s user %s %s public key %s %s",
1.87 djm 114: authctxt->valid ? "valid" : "invalid", authctxt->user,
115: have_sig ? "attempting" : "querying", pkalg, keystring);
116: sshbuf_free(pkbuf);
117: free(keystring);
118: }
119:
1.64 markus 120: pktype = sshkey_type_from_name(pkalg);
1.1 markus 121: if (pktype == KEY_UNSPEC) {
122: /* this is perfectly legal */
1.101 djm 123: verbose_f("unsupported public key algorithm: %s", pkalg);
1.1 markus 124: goto done;
125: }
1.64 markus 126: if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
1.101 djm 127: error_fr(r, "parse key");
1.64 markus 128: goto done;
129: }
1.1 markus 130: if (key == NULL) {
1.101 djm 131: error_f("cannot decode key: %s", pkalg);
1.1 markus 132: goto done;
133: }
134: if (key->type != pktype) {
1.101 djm 135: error_f("type mismatch for decoded key "
136: "(received %d, expected %d)", key->type, pktype);
1.39 djm 137: goto done;
138: }
1.64 markus 139: if (sshkey_type_plain(key->type) == KEY_RSA &&
140: (ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
1.39 djm 141: logit("Refusing RSA key because client uses unsafe "
142: "signature scheme");
1.1 markus 143: goto done;
144: }
1.68 djm 145: if (auth2_key_already_used(authctxt, key)) {
1.64 markus 146: logit("refusing previously-used %s key", sshkey_type(key));
1.44 djm 147: goto done;
148: }
1.104 dtucker 149: if (match_pattern_list(pkalg, options.pubkey_accepted_algos, 0) != 1) {
150: logit_f("key type %s not in PubkeyAcceptedAlgorithms",
1.101 djm 151: sshkey_ssh_name(key));
1.45 djm 152: goto done;
153: }
1.86 djm 154: if ((r = sshkey_check_cert_sigtype(key,
155: options.ca_sign_algorithms)) != 0) {
1.101 djm 156: logit_fr(r, "certificate signature algorithm %s",
1.86 djm 157: (key->cert == NULL || key->cert->signature_type == NULL) ?
1.101 djm 158: "(null)" : key->cert->signature_type);
1.86 djm 159: goto done;
160: }
1.73 djm 161: key_s = format_key(key);
162: if (sshkey_is_cert(key))
163: ca_s = format_key(key->cert->signature_key);
164:
1.1 markus 165: if (have_sig) {
1.101 djm 166: debug3_f("have %s signature for %s%s%s", pkalg, key_s,
167: ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s);
1.64 markus 168: if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 ||
169: (r = sshpkt_get_end(ssh)) != 0)
1.101 djm 170: fatal_fr(r, "parse signature packet");
1.64 markus 171: if ((b = sshbuf_new()) == NULL)
1.101 djm 172: fatal_f("sshbuf_new failed");
1.64 markus 173: if (ssh->compat & SSH_OLD_SESSIONID) {
1.106 ! djm 174: if ((r = sshbuf_putb(b, ssh->kex->session_id)) != 0)
1.101 djm 175: fatal_fr(r, "put old session id");
1.1 markus 176: } else {
1.106 ! djm 177: if ((r = sshbuf_put_stringb(b,
! 178: ssh->kex->session_id)) != 0)
1.101 djm 179: fatal_fr(r, "put session id");
1.1 markus 180: }
1.83 djm 181: if (!authctxt->valid || authctxt->user == NULL) {
1.101 djm 182: debug2_f("disabled because of invalid user");
1.83 djm 183: goto done;
184: }
1.1 markus 185: /* reconstruct packet */
1.35 djm 186: xasprintf(&userstyle, "%s%s%s", authctxt->user,
187: authctxt->style ? ":" : "",
188: authctxt->style ? authctxt->style : "");
1.64 markus 189: if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
190: (r = sshbuf_put_cstring(b, userstyle)) != 0 ||
1.75 djm 191: (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
192: (r = sshbuf_put_cstring(b, "publickey")) != 0 ||
193: (r = sshbuf_put_u8(b, have_sig)) != 0 ||
1.85 mestre 194: (r = sshbuf_put_cstring(b, pkalg)) != 0 ||
1.75 djm 195: (r = sshbuf_put_string(b, pkblob, blen)) != 0)
1.101 djm 196: fatal_fr(r, "reconstruct packet");
1.1 markus 197: #ifdef DEBUG_PK
1.64 markus 198: sshbuf_dump(b, stderr);
1.1 markus 199: #endif
200: /* test for correct signature */
201: authenticated = 0;
1.77 djm 202: if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) &&
1.80 djm 203: PRIVSEP(sshkey_verify(key, sig, slen,
204: sshbuf_ptr(b), sshbuf_len(b),
205: (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL,
1.95 djm 206: ssh->compat, &sig_details)) == 0) {
1.1 markus 207: authenticated = 1;
1.44 djm 208: }
1.96 djm 209: if (authenticated == 1 && sig_details != NULL) {
210: auth2_record_info(authctxt, "signature count = %u",
211: sig_details->sk_counter);
1.101 djm 212: debug_f("sk_counter = %u, sk_flags = 0x%02x",
213: sig_details->sk_counter, sig_details->sk_flags);
1.96 djm 214: req_presence = (options.pubkey_auth_options &
1.97 djm 215: PUBKEYAUTH_TOUCH_REQUIRED) ||
216: !authopts->no_require_user_presence;
1.96 djm 217: if (req_presence && (sig_details->sk_flags &
218: SSH_SK_USER_PRESENCE_REQD) == 0) {
219: error("public key %s signature for %s%s from "
220: "%.128s port %d rejected: user presence "
1.99 naddy 221: "(authenticator touch) requirement "
222: "not met ", key_s,
1.100 djm 223: authctxt->valid ? "" : "invalid user ",
224: authctxt->user, ssh_remote_ipaddr(ssh),
225: ssh_remote_port(ssh));
226: authenticated = 0;
227: goto done;
228: }
229: req_verify = (options.pubkey_auth_options &
230: PUBKEYAUTH_VERIFY_REQUIRED) ||
231: authopts->require_verify;
232: if (req_verify && (sig_details->sk_flags &
233: SSH_SK_USER_VERIFICATION_REQD) == 0) {
234: error("public key %s signature for %s%s from "
235: "%.128s port %d rejected: user "
236: "verification requirement not met ", key_s,
1.96 djm 237: authctxt->valid ? "" : "invalid user ",
238: authctxt->user, ssh_remote_ipaddr(ssh),
239: ssh_remote_port(ssh));
240: authenticated = 0;
241: goto done;
242: }
1.95 djm 243: }
1.68 djm 244: auth2_record_key(authctxt, authenticated, key);
1.1 markus 245: } else {
1.101 djm 246: debug_f("test pkalg %s pkblob %s%s%s", pkalg, key_s,
247: ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s);
1.73 djm 248:
1.64 markus 249: if ((r = sshpkt_get_end(ssh)) != 0)
1.101 djm 250: fatal_fr(r, "parse packet");
1.1 markus 251:
1.83 djm 252: if (!authctxt->valid || authctxt->user == NULL) {
1.101 djm 253: debug2_f("disabled because of invalid user");
1.83 djm 254: goto done;
255: }
1.1 markus 256: /* XXX fake reply and always send PK_OK ? */
257: /*
258: * XXX this allows testing whether a user is allowed
259: * to login: if you happen to have a valid pubkey this
260: * message is sent. the message is NEVER sent at all
261: * if a user is not allowed to login. is this an
262: * issue? -markus
263: */
1.77 djm 264: if (PRIVSEP(user_key_allowed(ssh, pw, key, 0, NULL))) {
1.64 markus 265: if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK))
266: != 0 ||
267: (r = sshpkt_put_cstring(ssh, pkalg)) != 0 ||
268: (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 ||
1.82 markus 269: (r = sshpkt_send(ssh)) != 0 ||
270: (r = ssh_packet_write_wait(ssh)) != 0)
1.101 djm 271: fatal_fr(r, "send packet");
1.1 markus 272: authctxt->postponed = 1;
273: }
274: }
275: done:
1.77 djm 276: if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) {
1.101 djm 277: debug_f("key options inconsistent with existing");
1.77 djm 278: authenticated = 0;
279: }
1.101 djm 280: debug2_f("authenticated %d pkalg %s", authenticated, pkalg);
1.77 djm 281:
1.84 djm 282: sshbuf_free(b);
1.77 djm 283: sshauthopt_free(authopts);
1.68 djm 284: sshkey_free(key);
1.64 markus 285: free(userstyle);
1.36 djm 286: free(pkalg);
287: free(pkblob);
1.73 djm 288: free(key_s);
289: free(ca_s);
1.83 djm 290: free(sig);
1.95 djm 291: sshkey_sig_details_free(sig_details);
1.1 markus 292: return authenticated;
293: }
294:
1.24 djm 295: static int
1.40 djm 296: match_principals_option(const char *principal_list, struct sshkey_cert *cert)
1.24 djm 297: {
298: char *result;
299: u_int i;
300:
301: /* XXX percent_expand() sequences for authorized_principals? */
302:
303: for (i = 0; i < cert->nprincipals; i++) {
304: if ((result = match_list(cert->principals[i],
305: principal_list, NULL)) != NULL) {
306: debug3("matched principal from key options \"%.100s\"",
307: result);
1.36 djm 308: free(result);
1.24 djm 309: return 1;
310: }
311: }
312: return 0;
313: }
314:
1.77 djm 315: /*
316: * Process a single authorized_principals format line. Returns 0 and sets
317: * authoptsp is principal is authorised, -1 otherwise. "loc" is used as a
318: * log preamble for file/line information.
319: */
1.24 djm 320: static int
1.77 djm 321: check_principals_line(struct ssh *ssh, char *cp, const struct sshkey_cert *cert,
322: const char *loc, struct sshauthopt **authoptsp)
1.24 djm 323: {
1.77 djm 324: u_int i, found = 0;
325: char *ep, *line_opts;
326: const char *reason = NULL;
327: struct sshauthopt *opts = NULL;
328:
329: if (authoptsp != NULL)
330: *authoptsp = NULL;
331:
332: /* Trim trailing whitespace. */
333: ep = cp + strlen(cp) - 1;
334: while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t'))
335: *ep-- = '\0';
336:
337: /*
338: * If the line has internal whitespace then assume it has
339: * key options.
340: */
341: line_opts = NULL;
342: if ((ep = strrchr(cp, ' ')) != NULL ||
343: (ep = strrchr(cp, '\t')) != NULL) {
344: for (; *ep == ' ' || *ep == '\t'; ep++)
345: ;
346: line_opts = cp;
347: cp = ep;
348: }
349: if ((opts = sshauthopt_parse(line_opts, &reason)) == NULL) {
350: debug("%s: bad principals options: %s", loc, reason);
351: auth_debug_add("%s: bad principals options: %s", loc, reason);
352: return -1;
353: }
354: /* Check principals in cert against those on line */
355: for (i = 0; i < cert->nprincipals; i++) {
356: if (strcmp(cp, cert->principals[i]) != 0)
357: continue;
358: debug3("%s: matched principal \"%.100s\"",
359: loc, cert->principals[i]);
360: found = 1;
361: }
362: if (found && authoptsp != NULL) {
363: *authoptsp = opts;
364: opts = NULL;
365: }
366: sshauthopt_free(opts);
367: return found ? 0 : -1;
368: }
369:
370: static int
371: process_principals(struct ssh *ssh, FILE *f, const char *file,
372: const struct sshkey_cert *cert, struct sshauthopt **authoptsp)
373: {
1.79 markus 374: char loc[256], *line = NULL, *cp, *ep;
375: size_t linesize = 0;
1.24 djm 376: u_long linenum = 0;
1.77 djm 377: u_int found_principal = 0;
378:
379: if (authoptsp != NULL)
380: *authoptsp = NULL;
1.24 djm 381:
1.79 markus 382: while (getline(&line, &linesize, f) != -1) {
383: linenum++;
1.62 djm 384: /* Always consume entire input */
385: if (found_principal)
386: continue;
1.77 djm 387:
1.26 djm 388: /* Skip leading whitespace. */
1.24 djm 389: for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
390: ;
1.26 djm 391: /* Skip blank and comment lines. */
392: if ((ep = strchr(cp, '#')) != NULL)
393: *ep = '\0';
394: if (!*cp || *cp == '\n')
1.24 djm 395: continue;
1.77 djm 396:
397: snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
398: if (check_principals_line(ssh, cp, cert, loc, authoptsp) == 0)
399: found_principal = 1;
1.24 djm 400: }
1.79 markus 401: free(line);
1.62 djm 402: return found_principal;
1.51 djm 403: }
404:
1.77 djm 405: /* XXX remove pw args here and elsewhere once ssh->authctxt is guaranteed */
406:
1.51 djm 407: static int
1.77 djm 408: match_principals_file(struct ssh *ssh, struct passwd *pw, char *file,
409: struct sshkey_cert *cert, struct sshauthopt **authoptsp)
1.51 djm 410: {
411: FILE *f;
412: int success;
413:
1.77 djm 414: if (authoptsp != NULL)
415: *authoptsp = NULL;
416:
1.51 djm 417: temporarily_use_uid(pw);
418: debug("trying authorized principals file %s", file);
419: if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
420: restore_uid();
421: return 0;
422: }
1.77 djm 423: success = process_principals(ssh, f, file, cert, authoptsp);
1.24 djm 424: fclose(f);
425: restore_uid();
1.51 djm 426: return success;
1.31 djm 427: }
1.24 djm 428:
1.31 djm 429: /*
1.51 djm 430: * Checks whether principal is allowed in output of command.
431: * returns 1 if the principal is allowed or 0 otherwise.
432: */
433: static int
1.77 djm 434: match_principals_command(struct ssh *ssh, struct passwd *user_pw,
435: const struct sshkey *key, struct sshauthopt **authoptsp)
1.51 djm 436: {
1.77 djm 437: struct passwd *runas_pw = NULL;
1.56 djm 438: const struct sshkey_cert *cert = key->cert;
1.51 djm 439: FILE *f = NULL;
1.56 djm 440: int r, ok, found_principal = 0;
1.51 djm 441: int i, ac = 0, uid_swapped = 0;
442: pid_t pid;
443: char *tmp, *username = NULL, *command = NULL, **av = NULL;
1.56 djm 444: char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL;
1.88 djm 445: char serial_s[32], uidstr[32];
1.51 djm 446: void (*osigchld)(int);
447:
1.77 djm 448: if (authoptsp != NULL)
449: *authoptsp = NULL;
1.51 djm 450: if (options.authorized_principals_command == NULL)
451: return 0;
452: if (options.authorized_principals_command_user == NULL) {
453: error("No user for AuthorizedPrincipalsCommand specified, "
454: "skipping");
455: return 0;
456: }
457:
458: /*
459: * NB. all returns later this function should go via "out" to
460: * ensure the original SIGCHLD handler is restored properly.
461: */
1.98 dtucker 462: osigchld = ssh_signal(SIGCHLD, SIG_DFL);
1.51 djm 463:
464: /* Prepare and verify the user for the command */
465: username = percent_expand(options.authorized_principals_command_user,
466: "u", user_pw->pw_name, (char *)NULL);
1.77 djm 467: runas_pw = getpwnam(username);
468: if (runas_pw == NULL) {
1.51 djm 469: error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s",
470: username, strerror(errno));
471: goto out;
472: }
473:
474: /* Turn the command into an argument vector */
1.69 djm 475: if (argv_split(options.authorized_principals_command, &ac, &av) != 0) {
1.51 djm 476: error("AuthorizedPrincipalsCommand \"%s\" contains "
1.90 djm 477: "invalid quotes", options.authorized_principals_command);
1.51 djm 478: goto out;
479: }
480: if (ac == 0) {
481: error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
1.90 djm 482: options.authorized_principals_command);
1.51 djm 483: goto out;
484: }
1.56 djm 485: if ((ca_fp = sshkey_fingerprint(cert->signature_key,
486: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1.101 djm 487: error_f("sshkey_fingerprint failed");
1.56 djm 488: goto out;
489: }
1.57 djm 490: if ((key_fp = sshkey_fingerprint(key,
1.56 djm 491: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1.101 djm 492: error_f("sshkey_fingerprint failed");
1.56 djm 493: goto out;
494: }
495: if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) {
1.101 djm 496: error_fr(r, "sshkey_to_base64 failed");
1.56 djm 497: goto out;
498: }
499: if ((r = sshkey_to_base64(key, &keytext)) != 0) {
1.101 djm 500: error_fr(r, "sshkey_to_base64 failed");
1.56 djm 501: goto out;
502: }
1.59 djm 503: snprintf(serial_s, sizeof(serial_s), "%llu",
504: (unsigned long long)cert->serial);
1.78 djm 505: snprintf(uidstr, sizeof(uidstr), "%llu",
506: (unsigned long long)user_pw->pw_uid);
1.51 djm 507: for (i = 1; i < ac; i++) {
508: tmp = percent_expand(av[i],
1.78 djm 509: "U", uidstr,
1.51 djm 510: "u", user_pw->pw_name,
511: "h", user_pw->pw_dir,
1.56 djm 512: "t", sshkey_ssh_name(key),
513: "T", sshkey_ssh_name(cert->signature_key),
514: "f", key_fp,
515: "F", ca_fp,
516: "k", keytext,
517: "K", catext,
1.58 djm 518: "i", cert->key_id,
519: "s", serial_s,
1.51 djm 520: (char *)NULL);
521: if (tmp == NULL)
1.101 djm 522: fatal_f("percent_expand failed");
1.51 djm 523: free(av[i]);
524: av[i] = tmp;
525: }
526: /* Prepare a printable command for logs, etc. */
1.69 djm 527: command = argv_assemble(ac, av);
1.51 djm 528:
1.103 djm 529: if ((pid = subprocess("AuthorizedPrincipalsCommand", command,
1.69 djm 530: ac, av, &f,
1.103 djm 531: SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD,
532: runas_pw, temporarily_use_uid, restore_uid)) == 0)
1.51 djm 533: goto out;
534:
535: uid_swapped = 1;
1.77 djm 536: temporarily_use_uid(runas_pw);
1.51 djm 537:
1.77 djm 538: ok = process_principals(ssh, f, "(command)", cert, authoptsp);
1.51 djm 539:
1.61 djm 540: fclose(f);
541: f = NULL;
542:
1.70 djm 543: if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0)
1.51 djm 544: goto out;
545:
546: /* Read completed successfully */
547: found_principal = ok;
548: out:
549: if (f != NULL)
550: fclose(f);
1.98 dtucker 551: ssh_signal(SIGCHLD, osigchld);
1.51 djm 552: for (i = 0; i < ac; i++)
553: free(av[i]);
554: free(av);
555: if (uid_swapped)
556: restore_uid();
557: free(command);
558: free(username);
1.56 djm 559: free(ca_fp);
560: free(key_fp);
561: free(catext);
562: free(keytext);
1.51 djm 563: return found_principal;
1.77 djm 564: }
565:
566: /*
567: * Check a single line of an authorized_keys-format file. Returns 0 if key
568: * matches, -1 otherwise. Will return key/cert options via *authoptsp
569: * on success. "loc" is used as file/line location in log messages.
570: */
571: static int
572: check_authkey_line(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
573: char *cp, const char *loc, struct sshauthopt **authoptsp)
574: {
575: int want_keytype = sshkey_is_cert(key) ? KEY_UNSPEC : key->type;
576: struct sshkey *found = NULL;
577: struct sshauthopt *keyopts = NULL, *certopts = NULL, *finalopts = NULL;
578: char *key_options = NULL, *fp = NULL;
579: const char *reason = NULL;
580: int ret = -1;
581:
582: if (authoptsp != NULL)
583: *authoptsp = NULL;
584:
585: if ((found = sshkey_new(want_keytype)) == NULL) {
1.101 djm 586: debug3_f("keytype %d failed", want_keytype);
1.77 djm 587: goto out;
588: }
589:
590: /* XXX djm: peek at key type in line and skip if unwanted */
591:
592: if (sshkey_read(found, &cp) != 0) {
593: /* no key? check for options */
594: debug2("%s: check options: '%s'", loc, cp);
595: key_options = cp;
1.93 djm 596: if (sshkey_advance_past_options(&cp) != 0) {
1.77 djm 597: reason = "invalid key option string";
598: goto fail_reason;
599: }
600: skip_space(&cp);
601: if (sshkey_read(found, &cp) != 0) {
602: /* still no key? advance to next line*/
603: debug2("%s: advance: '%s'", loc, cp);
604: goto out;
605: }
606: }
607: /* Parse key options now; we need to know if this is a CA key */
608: if ((keyopts = sshauthopt_parse(key_options, &reason)) == NULL) {
609: debug("%s: bad key options: %s", loc, reason);
610: auth_debug_add("%s: bad key options: %s", loc, reason);
611: goto out;
612: }
613: /* Ignore keys that don't match or incorrectly marked as CAs */
614: if (sshkey_is_cert(key)) {
615: /* Certificate; check signature key against CA */
616: if (!sshkey_equal(found, key->cert->signature_key) ||
617: !keyopts->cert_authority)
618: goto out;
619: } else {
620: /* Plain key: check it against key found in file */
621: if (!sshkey_equal(found, key) || keyopts->cert_authority)
622: goto out;
623: }
624:
625: /* We have a candidate key, perform authorisation checks */
626: if ((fp = sshkey_fingerprint(found,
627: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
1.101 djm 628: fatal_f("fingerprint failed");
1.77 djm 629:
630: debug("%s: matching %s found: %s %s", loc,
631: sshkey_is_cert(key) ? "CA" : "key", sshkey_type(found), fp);
632:
633: if (auth_authorise_keyopts(ssh, pw, keyopts,
634: sshkey_is_cert(key), loc) != 0) {
635: reason = "Refused by key options";
636: goto fail_reason;
637: }
638: /* That's all we need for plain keys. */
639: if (!sshkey_is_cert(key)) {
640: verbose("Accepted key %s %s found at %s",
641: sshkey_type(found), fp, loc);
642: finalopts = keyopts;
643: keyopts = NULL;
644: goto success;
645: }
646:
647: /*
648: * Additional authorisation for certificates.
649: */
650:
651: /* Parse and check options present in certificate */
652: if ((certopts = sshauthopt_from_cert(key)) == NULL) {
653: reason = "Invalid certificate options";
654: goto fail_reason;
655: }
656: if (auth_authorise_keyopts(ssh, pw, certopts, 0, loc) != 0) {
657: reason = "Refused by certificate options";
658: goto fail_reason;
659: }
660: if ((finalopts = sshauthopt_merge(keyopts, certopts, &reason)) == NULL)
661: goto fail_reason;
662:
663: /*
664: * If the user has specified a list of principals as
665: * a key option, then prefer that list to matching
666: * their username in the certificate principals list.
667: */
668: if (keyopts->cert_principals != NULL &&
669: !match_principals_option(keyopts->cert_principals, key->cert)) {
670: reason = "Certificate does not contain an authorized principal";
671: goto fail_reason;
672: }
1.105 djm 673: if (sshkey_cert_check_authority(key, 0, 0, 0,
1.77 djm 674: keyopts->cert_principals == NULL ? pw->pw_name : NULL, &reason) != 0)
675: goto fail_reason;
676:
677: verbose("Accepted certificate ID \"%s\" (serial %llu) "
678: "signed by CA %s %s found at %s",
679: key->cert->key_id,
680: (unsigned long long)key->cert->serial,
681: sshkey_type(found), fp, loc);
682:
683: success:
684: if (finalopts == NULL)
1.101 djm 685: fatal_f("internal error: missing options");
1.77 djm 686: if (authoptsp != NULL) {
687: *authoptsp = finalopts;
688: finalopts = NULL;
689: }
690: /* success */
691: ret = 0;
692: goto out;
693:
694: fail_reason:
695: error("%s", reason);
696: auth_debug_add("%s", reason);
697: out:
698: free(fp);
699: sshauthopt_free(keyopts);
700: sshauthopt_free(certopts);
701: sshauthopt_free(finalopts);
702: sshkey_free(found);
703: return ret;
704: }
705:
1.51 djm 706: /*
1.31 djm 707: * Checks whether key is allowed in authorized_keys-format file,
708: * returns 1 if the key is allowed or 0 otherwise.
709: */
1.1 markus 710: static int
1.77 djm 711: check_authkeys_file(struct ssh *ssh, struct passwd *pw, FILE *f,
712: char *file, struct sshkey *key, struct sshauthopt **authoptsp)
1.1 markus 713: {
1.79 markus 714: char *cp, *line = NULL, loc[256];
715: size_t linesize = 0;
1.18 dtucker 716: int found_key = 0;
1.1 markus 717: u_long linenum = 0;
1.77 djm 718:
719: if (authoptsp != NULL)
720: *authoptsp = NULL;
1.1 markus 721:
1.79 markus 722: while (getline(&line, &linesize, f) != -1) {
723: linenum++;
1.71 djm 724: /* Always consume entire file */
1.62 djm 725: if (found_key)
726: continue;
1.20 djm 727:
1.1 markus 728: /* Skip leading whitespace, empty and comment lines. */
1.77 djm 729: cp = line;
730: skip_space(&cp);
1.1 markus 731: if (!*cp || *cp == '\n' || *cp == '#')
732: continue;
1.77 djm 733: snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
734: if (check_authkey_line(ssh, pw, key, cp, loc, authoptsp) == 0)
1.20 djm 735: found_key = 1;
1.1 markus 736: }
1.79 markus 737: free(line);
1.1 markus 738: return found_key;
739: }
740:
1.21 djm 741: /* Authenticate a certificate key against TrustedUserCAKeys */
742: static int
1.77 djm 743: user_cert_trusted_ca(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
744: struct sshauthopt **authoptsp)
1.21 djm 745: {
1.24 djm 746: char *ca_fp, *principals_file = NULL;
1.21 djm 747: const char *reason;
1.77 djm 748: struct sshauthopt *principals_opts = NULL, *cert_opts = NULL;
749: struct sshauthopt *final_opts = NULL;
1.64 markus 750: int r, ret = 0, found_principal = 0, use_authorized_principals;
1.21 djm 751:
1.77 djm 752: if (authoptsp != NULL)
753: *authoptsp = NULL;
754:
1.64 markus 755: if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL)
1.21 djm 756: return 0;
757:
1.46 djm 758: if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
759: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
760: return 0;
1.21 djm 761:
1.64 markus 762: if ((r = sshkey_in_file(key->cert->signature_key,
763: options.trusted_user_ca_keys, 1, 0)) != 0) {
1.101 djm 764: debug2_fr(r, "CA %s %s is not listed in %s",
1.64 markus 765: sshkey_type(key->cert->signature_key), ca_fp,
1.101 djm 766: options.trusted_user_ca_keys);
1.21 djm 767: goto out;
768: }
1.24 djm 769: /*
770: * If AuthorizedPrincipals is in use, then compare the certificate
771: * principals against the names in that file rather than matching
772: * against the username.
773: */
774: if ((principals_file = authorized_principals_file(pw)) != NULL) {
1.77 djm 775: if (match_principals_file(ssh, pw, principals_file,
776: key->cert, &principals_opts))
1.51 djm 777: found_principal = 1;
778: }
779: /* Try querying command if specified */
1.77 djm 780: if (!found_principal && match_principals_command(ssh, pw, key,
781: &principals_opts))
1.51 djm 782: found_principal = 1;
1.53 jsing 783: /* If principals file or command is specified, then require a match */
784: use_authorized_principals = principals_file != NULL ||
785: options.authorized_principals_command != NULL;
786: if (!found_principal && use_authorized_principals) {
1.51 djm 787: reason = "Certificate does not contain an authorized principal";
1.77 djm 788: goto fail_reason;
1.21 djm 789: }
1.77 djm 790: if (use_authorized_principals && principals_opts == NULL)
1.101 djm 791: fatal_f("internal error: missing principals_opts");
1.105 djm 792: if (sshkey_cert_check_authority(key, 0, 1, 0,
1.53 jsing 793: use_authorized_principals ? NULL : pw->pw_name, &reason) != 0)
1.24 djm 794: goto fail_reason;
1.77 djm 795:
796: /* Check authority from options in key and from principals file/cmd */
797: if ((cert_opts = sshauthopt_from_cert(key)) == NULL) {
798: reason = "Invalid certificate options";
799: goto fail_reason;
800: }
801: if (auth_authorise_keyopts(ssh, pw, cert_opts, 0, "cert") != 0) {
802: reason = "Refused by certificate options";
1.60 djm 803: goto fail_reason;
1.77 djm 804: }
805: if (principals_opts == NULL) {
806: final_opts = cert_opts;
807: cert_opts = NULL;
808: } else {
809: if (auth_authorise_keyopts(ssh, pw, principals_opts, 0,
810: "principals") != 0) {
811: reason = "Refused by certificate principals options";
812: goto fail_reason;
813: }
814: if ((final_opts = sshauthopt_merge(principals_opts,
815: cert_opts, &reason)) == NULL) {
816: fail_reason:
817: error("%s", reason);
818: auth_debug_add("%s", reason);
819: goto out;
820: }
821: }
1.21 djm 822:
1.77 djm 823: /* Success */
1.54 djm 824: verbose("Accepted certificate ID \"%s\" (serial %llu) signed by "
825: "%s CA %s via %s", key->cert->key_id,
826: (unsigned long long)key->cert->serial,
1.64 markus 827: sshkey_type(key->cert->signature_key), ca_fp,
1.22 djm 828: options.trusted_user_ca_keys);
1.77 djm 829: if (authoptsp != NULL) {
830: *authoptsp = final_opts;
831: final_opts = NULL;
832: }
1.21 djm 833: ret = 1;
834: out:
1.77 djm 835: sshauthopt_free(principals_opts);
836: sshauthopt_free(cert_opts);
837: sshauthopt_free(final_opts);
1.36 djm 838: free(principals_file);
839: free(ca_fp);
1.21 djm 840: return ret;
841: }
842:
1.31 djm 843: /*
844: * Checks whether key is allowed in file.
845: * returns 1 if the key is allowed or 0 otherwise.
846: */
847: static int
1.77 djm 848: user_key_allowed2(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
849: char *file, struct sshauthopt **authoptsp)
1.31 djm 850: {
851: FILE *f;
852: int found_key = 0;
853:
1.77 djm 854: if (authoptsp != NULL)
855: *authoptsp = NULL;
856:
1.31 djm 857: /* Temporarily use the user's uid. */
858: temporarily_use_uid(pw);
859:
860: debug("trying public key file %s", file);
861: if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
1.77 djm 862: found_key = check_authkeys_file(ssh, pw, f, file,
863: key, authoptsp);
1.31 djm 864: fclose(f);
865: }
866:
867: restore_uid();
868: return found_key;
869: }
870:
871: /*
872: * Checks whether key is allowed in output of command.
873: * returns 1 if the key is allowed or 0 otherwise.
874: */
875: static int
1.77 djm 876: user_key_command_allowed2(struct ssh *ssh, struct passwd *user_pw,
877: struct sshkey *key, struct sshauthopt **authoptsp)
1.31 djm 878: {
1.77 djm 879: struct passwd *runas_pw = NULL;
1.50 djm 880: FILE *f = NULL;
881: int r, ok, found_key = 0;
882: int i, uid_swapped = 0, ac = 0;
1.31 djm 883: pid_t pid;
1.50 djm 884: char *username = NULL, *key_fp = NULL, *keytext = NULL;
1.78 djm 885: char uidstr[32], *tmp, *command = NULL, **av = NULL;
1.50 djm 886: void (*osigchld)(int);
1.31 djm 887:
1.77 djm 888: if (authoptsp != NULL)
889: *authoptsp = NULL;
1.50 djm 890: if (options.authorized_keys_command == NULL)
1.31 djm 891: return 0;
1.32 djm 892: if (options.authorized_keys_command_user == NULL) {
893: error("No user for AuthorizedKeysCommand specified, skipping");
894: return 0;
895: }
896:
1.50 djm 897: /*
898: * NB. all returns later this function should go via "out" to
899: * ensure the original SIGCHLD handler is restored properly.
900: */
1.98 dtucker 901: osigchld = ssh_signal(SIGCHLD, SIG_DFL);
1.50 djm 902:
903: /* Prepare and verify the user for the command */
1.32 djm 904: username = percent_expand(options.authorized_keys_command_user,
905: "u", user_pw->pw_name, (char *)NULL);
1.77 djm 906: runas_pw = getpwnam(username);
907: if (runas_pw == NULL) {
1.34 djm 908: error("AuthorizedKeysCommandUser \"%s\" not found: %s",
909: username, strerror(errno));
1.50 djm 910: goto out;
1.31 djm 911: }
912:
1.50 djm 913: /* Prepare AuthorizedKeysCommand */
914: if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash,
915: SSH_FP_DEFAULT)) == NULL) {
1.101 djm 916: error_f("sshkey_fingerprint failed");
1.31 djm 917: goto out;
918: }
1.50 djm 919: if ((r = sshkey_to_base64(key, &keytext)) != 0) {
1.101 djm 920: error_fr(r, "sshkey_to_base64 failed");
1.31 djm 921: goto out;
922: }
923:
1.50 djm 924: /* Turn the command into an argument vector */
1.69 djm 925: if (argv_split(options.authorized_keys_command, &ac, &av) != 0) {
1.50 djm 926: error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
1.102 djm 927: options.authorized_keys_command);
1.50 djm 928: goto out;
929: }
930: if (ac == 0) {
931: error("AuthorizedKeysCommand \"%s\" yielded no arguments",
1.102 djm 932: options.authorized_keys_command);
1.31 djm 933: goto out;
934: }
1.78 djm 935: snprintf(uidstr, sizeof(uidstr), "%llu",
936: (unsigned long long)user_pw->pw_uid);
1.50 djm 937: for (i = 1; i < ac; i++) {
938: tmp = percent_expand(av[i],
1.78 djm 939: "U", uidstr,
1.50 djm 940: "u", user_pw->pw_name,
941: "h", user_pw->pw_dir,
942: "t", sshkey_ssh_name(key),
943: "f", key_fp,
944: "k", keytext,
945: (char *)NULL);
946: if (tmp == NULL)
1.101 djm 947: fatal_f("percent_expand failed");
1.50 djm 948: free(av[i]);
949: av[i] = tmp;
950: }
951: /* Prepare a printable command for logs, etc. */
1.69 djm 952: command = argv_assemble(ac, av);
1.31 djm 953:
954: /*
1.50 djm 955: * If AuthorizedKeysCommand was run without arguments
956: * then fall back to the old behaviour of passing the
957: * target username as a single argument.
1.31 djm 958: */
1.50 djm 959: if (ac == 1) {
960: av = xreallocarray(av, ac + 2, sizeof(*av));
961: av[1] = xstrdup(user_pw->pw_name);
962: av[2] = NULL;
963: /* Fix up command too, since it is used in log messages */
964: free(command);
965: xasprintf(&command, "%s %s", av[0], av[1]);
966: }
1.31 djm 967:
1.103 djm 968: if ((pid = subprocess("AuthorizedKeysCommand", command,
1.69 djm 969: ac, av, &f,
1.103 djm 970: SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD,
971: runas_pw, temporarily_use_uid, restore_uid)) == 0)
1.50 djm 972: goto out;
1.31 djm 973:
1.50 djm 974: uid_swapped = 1;
1.77 djm 975: temporarily_use_uid(runas_pw);
1.31 djm 976:
1.77 djm 977: ok = check_authkeys_file(ssh, user_pw, f,
978: options.authorized_keys_command, key, authoptsp);
1.61 djm 979:
980: fclose(f);
981: f = NULL;
1.31 djm 982:
1.70 djm 983: if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0)
1.31 djm 984: goto out;
1.50 djm 985:
986: /* Read completed successfully */
1.31 djm 987: found_key = ok;
988: out:
1.50 djm 989: if (f != NULL)
990: fclose(f);
1.98 dtucker 991: ssh_signal(SIGCHLD, osigchld);
1.50 djm 992: for (i = 0; i < ac; i++)
993: free(av[i]);
994: free(av);
995: if (uid_swapped)
996: restore_uid();
997: free(command);
998: free(username);
999: free(key_fp);
1000: free(keytext);
1.31 djm 1001: return found_key;
1002: }
1003:
1004: /*
1005: * Check whether key authenticates and authorises the user.
1006: */
1.1 markus 1007: int
1.77 djm 1008: user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
1009: int auth_attempt, struct sshauthopt **authoptsp)
1.1 markus 1010: {
1.89 djm 1011: u_int success = 0, i;
1.1 markus 1012: char *file;
1.77 djm 1013: struct sshauthopt *opts = NULL;
1.89 djm 1014:
1.77 djm 1015: if (authoptsp != NULL)
1016: *authoptsp = NULL;
1.21 djm 1017:
1018: if (auth_key_is_revoked(key))
1019: return 0;
1.64 markus 1020: if (sshkey_is_cert(key) &&
1021: auth_key_is_revoked(key->cert->signature_key))
1.21 djm 1022: return 0;
1023:
1.89 djm 1024: for (i = 0; !success && i < options.num_authkeys_files; i++) {
1025: if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
1026: continue;
1027: file = expand_authorized_keys(
1028: options.authorized_keys_files[i], pw);
1029: success = user_key_allowed2(ssh, pw, key, file, &opts);
1030: free(file);
1031: if (!success) {
1032: sshauthopt_free(opts);
1033: opts = NULL;
1034: }
1035: }
1036: if (success)
1037: goto out;
1038:
1.77 djm 1039: if ((success = user_cert_trusted_ca(ssh, pw, key, &opts)) != 0)
1040: goto out;
1041: sshauthopt_free(opts);
1042: opts = NULL;
1043:
1044: if ((success = user_key_command_allowed2(ssh, pw, key, &opts)) != 0)
1045: goto out;
1046: sshauthopt_free(opts);
1047: opts = NULL;
1.1 markus 1048:
1.77 djm 1049: out:
1050: if (success && authoptsp != NULL) {
1051: *authoptsp = opts;
1052: opts = NULL;
1053: }
1054: sshauthopt_free(opts);
1.1 markus 1055: return success;
1056: }
1.2 markus 1057:
1058: Authmethod method_pubkey = {
1059: "publickey",
1060: userauth_pubkey,
1061: &options.pubkey_authentication
1062: };