Annotation of src/usr.bin/ssh/auth2-pubkey.c, Revision 1.108
1.108 ! djm 1: /* $OpenBSD: auth2-pubkey.c,v 1.107 2021/04/03 06:18:40 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 */
1.108 ! djm 475: if (argv_split(options.authorized_principals_command,
! 476: &ac, &av, 0) != 0) {
1.51 djm 477: error("AuthorizedPrincipalsCommand \"%s\" contains "
1.90 djm 478: "invalid quotes", options.authorized_principals_command);
1.51 djm 479: goto out;
480: }
481: if (ac == 0) {
482: error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
1.90 djm 483: options.authorized_principals_command);
1.51 djm 484: goto out;
485: }
1.56 djm 486: if ((ca_fp = sshkey_fingerprint(cert->signature_key,
487: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1.101 djm 488: error_f("sshkey_fingerprint failed");
1.56 djm 489: goto out;
490: }
1.57 djm 491: if ((key_fp = sshkey_fingerprint(key,
1.56 djm 492: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1.101 djm 493: error_f("sshkey_fingerprint failed");
1.56 djm 494: goto out;
495: }
496: if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) {
1.101 djm 497: error_fr(r, "sshkey_to_base64 failed");
1.56 djm 498: goto out;
499: }
500: if ((r = sshkey_to_base64(key, &keytext)) != 0) {
1.101 djm 501: error_fr(r, "sshkey_to_base64 failed");
1.56 djm 502: goto out;
503: }
1.59 djm 504: snprintf(serial_s, sizeof(serial_s), "%llu",
505: (unsigned long long)cert->serial);
1.78 djm 506: snprintf(uidstr, sizeof(uidstr), "%llu",
507: (unsigned long long)user_pw->pw_uid);
1.51 djm 508: for (i = 1; i < ac; i++) {
509: tmp = percent_expand(av[i],
1.78 djm 510: "U", uidstr,
1.51 djm 511: "u", user_pw->pw_name,
512: "h", user_pw->pw_dir,
1.56 djm 513: "t", sshkey_ssh_name(key),
514: "T", sshkey_ssh_name(cert->signature_key),
515: "f", key_fp,
516: "F", ca_fp,
517: "k", keytext,
518: "K", catext,
1.58 djm 519: "i", cert->key_id,
520: "s", serial_s,
1.51 djm 521: (char *)NULL);
522: if (tmp == NULL)
1.101 djm 523: fatal_f("percent_expand failed");
1.51 djm 524: free(av[i]);
525: av[i] = tmp;
526: }
527: /* Prepare a printable command for logs, etc. */
1.69 djm 528: command = argv_assemble(ac, av);
1.51 djm 529:
1.103 djm 530: if ((pid = subprocess("AuthorizedPrincipalsCommand", command,
1.69 djm 531: ac, av, &f,
1.103 djm 532: SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD,
533: runas_pw, temporarily_use_uid, restore_uid)) == 0)
1.51 djm 534: goto out;
535:
536: uid_swapped = 1;
1.77 djm 537: temporarily_use_uid(runas_pw);
1.51 djm 538:
1.77 djm 539: ok = process_principals(ssh, f, "(command)", cert, authoptsp);
1.51 djm 540:
1.61 djm 541: fclose(f);
542: f = NULL;
543:
1.70 djm 544: if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0)
1.51 djm 545: goto out;
546:
547: /* Read completed successfully */
548: found_principal = ok;
549: out:
550: if (f != NULL)
551: fclose(f);
1.98 dtucker 552: ssh_signal(SIGCHLD, osigchld);
1.51 djm 553: for (i = 0; i < ac; i++)
554: free(av[i]);
555: free(av);
556: if (uid_swapped)
557: restore_uid();
558: free(command);
559: free(username);
1.56 djm 560: free(ca_fp);
561: free(key_fp);
562: free(catext);
563: free(keytext);
1.51 djm 564: return found_principal;
1.77 djm 565: }
566:
567: /*
568: * Check a single line of an authorized_keys-format file. Returns 0 if key
569: * matches, -1 otherwise. Will return key/cert options via *authoptsp
570: * on success. "loc" is used as file/line location in log messages.
571: */
572: static int
573: check_authkey_line(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
574: char *cp, const char *loc, struct sshauthopt **authoptsp)
575: {
576: int want_keytype = sshkey_is_cert(key) ? KEY_UNSPEC : key->type;
577: struct sshkey *found = NULL;
578: struct sshauthopt *keyopts = NULL, *certopts = NULL, *finalopts = NULL;
579: char *key_options = NULL, *fp = NULL;
580: const char *reason = NULL;
581: int ret = -1;
582:
583: if (authoptsp != NULL)
584: *authoptsp = NULL;
585:
586: if ((found = sshkey_new(want_keytype)) == NULL) {
1.101 djm 587: debug3_f("keytype %d failed", want_keytype);
1.77 djm 588: goto out;
589: }
590:
591: /* XXX djm: peek at key type in line and skip if unwanted */
592:
593: if (sshkey_read(found, &cp) != 0) {
594: /* no key? check for options */
595: debug2("%s: check options: '%s'", loc, cp);
596: key_options = cp;
1.93 djm 597: if (sshkey_advance_past_options(&cp) != 0) {
1.77 djm 598: reason = "invalid key option string";
599: goto fail_reason;
600: }
601: skip_space(&cp);
602: if (sshkey_read(found, &cp) != 0) {
603: /* still no key? advance to next line*/
604: debug2("%s: advance: '%s'", loc, cp);
605: goto out;
606: }
607: }
608: /* Parse key options now; we need to know if this is a CA key */
609: if ((keyopts = sshauthopt_parse(key_options, &reason)) == NULL) {
610: debug("%s: bad key options: %s", loc, reason);
611: auth_debug_add("%s: bad key options: %s", loc, reason);
612: goto out;
613: }
614: /* Ignore keys that don't match or incorrectly marked as CAs */
615: if (sshkey_is_cert(key)) {
616: /* Certificate; check signature key against CA */
617: if (!sshkey_equal(found, key->cert->signature_key) ||
618: !keyopts->cert_authority)
619: goto out;
620: } else {
621: /* Plain key: check it against key found in file */
622: if (!sshkey_equal(found, key) || keyopts->cert_authority)
623: goto out;
624: }
625:
626: /* We have a candidate key, perform authorisation checks */
627: if ((fp = sshkey_fingerprint(found,
628: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
1.101 djm 629: fatal_f("fingerprint failed");
1.77 djm 630:
631: debug("%s: matching %s found: %s %s", loc,
632: sshkey_is_cert(key) ? "CA" : "key", sshkey_type(found), fp);
633:
634: if (auth_authorise_keyopts(ssh, pw, keyopts,
635: sshkey_is_cert(key), loc) != 0) {
636: reason = "Refused by key options";
637: goto fail_reason;
638: }
639: /* That's all we need for plain keys. */
640: if (!sshkey_is_cert(key)) {
641: verbose("Accepted key %s %s found at %s",
642: sshkey_type(found), fp, loc);
643: finalopts = keyopts;
644: keyopts = NULL;
645: goto success;
646: }
647:
648: /*
649: * Additional authorisation for certificates.
650: */
651:
652: /* Parse and check options present in certificate */
653: if ((certopts = sshauthopt_from_cert(key)) == NULL) {
654: reason = "Invalid certificate options";
655: goto fail_reason;
656: }
657: if (auth_authorise_keyopts(ssh, pw, certopts, 0, loc) != 0) {
658: reason = "Refused by certificate options";
659: goto fail_reason;
660: }
661: if ((finalopts = sshauthopt_merge(keyopts, certopts, &reason)) == NULL)
662: goto fail_reason;
663:
664: /*
665: * If the user has specified a list of principals as
666: * a key option, then prefer that list to matching
667: * their username in the certificate principals list.
668: */
669: if (keyopts->cert_principals != NULL &&
670: !match_principals_option(keyopts->cert_principals, key->cert)) {
671: reason = "Certificate does not contain an authorized principal";
672: goto fail_reason;
673: }
1.105 djm 674: if (sshkey_cert_check_authority(key, 0, 0, 0,
1.107 djm 675: keyopts->cert_principals == NULL ? pw->pw_name : NULL,
676: &reason) != 0)
1.77 djm 677: goto fail_reason;
678:
679: verbose("Accepted certificate ID \"%s\" (serial %llu) "
680: "signed by CA %s %s found at %s",
681: key->cert->key_id,
682: (unsigned long long)key->cert->serial,
683: sshkey_type(found), fp, loc);
684:
685: success:
686: if (finalopts == NULL)
1.101 djm 687: fatal_f("internal error: missing options");
1.77 djm 688: if (authoptsp != NULL) {
689: *authoptsp = finalopts;
690: finalopts = NULL;
691: }
692: /* success */
693: ret = 0;
694: goto out;
695:
696: fail_reason:
697: error("%s", reason);
698: auth_debug_add("%s", reason);
699: out:
700: free(fp);
701: sshauthopt_free(keyopts);
702: sshauthopt_free(certopts);
703: sshauthopt_free(finalopts);
704: sshkey_free(found);
705: return ret;
706: }
707:
1.51 djm 708: /*
1.31 djm 709: * Checks whether key is allowed in authorized_keys-format file,
710: * returns 1 if the key is allowed or 0 otherwise.
711: */
1.1 markus 712: static int
1.77 djm 713: check_authkeys_file(struct ssh *ssh, struct passwd *pw, FILE *f,
714: char *file, struct sshkey *key, struct sshauthopt **authoptsp)
1.1 markus 715: {
1.79 markus 716: char *cp, *line = NULL, loc[256];
717: size_t linesize = 0;
1.18 dtucker 718: int found_key = 0;
1.1 markus 719: u_long linenum = 0;
1.77 djm 720:
721: if (authoptsp != NULL)
722: *authoptsp = NULL;
1.1 markus 723:
1.79 markus 724: while (getline(&line, &linesize, f) != -1) {
725: linenum++;
1.71 djm 726: /* Always consume entire file */
1.62 djm 727: if (found_key)
728: continue;
1.20 djm 729:
1.1 markus 730: /* Skip leading whitespace, empty and comment lines. */
1.77 djm 731: cp = line;
732: skip_space(&cp);
1.1 markus 733: if (!*cp || *cp == '\n' || *cp == '#')
734: continue;
1.77 djm 735: snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
736: if (check_authkey_line(ssh, pw, key, cp, loc, authoptsp) == 0)
1.20 djm 737: found_key = 1;
1.1 markus 738: }
1.79 markus 739: free(line);
1.1 markus 740: return found_key;
741: }
742:
1.21 djm 743: /* Authenticate a certificate key against TrustedUserCAKeys */
744: static int
1.77 djm 745: user_cert_trusted_ca(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
746: struct sshauthopt **authoptsp)
1.21 djm 747: {
1.24 djm 748: char *ca_fp, *principals_file = NULL;
1.21 djm 749: const char *reason;
1.77 djm 750: struct sshauthopt *principals_opts = NULL, *cert_opts = NULL;
751: struct sshauthopt *final_opts = NULL;
1.64 markus 752: int r, ret = 0, found_principal = 0, use_authorized_principals;
1.21 djm 753:
1.77 djm 754: if (authoptsp != NULL)
755: *authoptsp = NULL;
756:
1.64 markus 757: if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL)
1.21 djm 758: return 0;
759:
1.46 djm 760: if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
761: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
762: return 0;
1.21 djm 763:
1.64 markus 764: if ((r = sshkey_in_file(key->cert->signature_key,
765: options.trusted_user_ca_keys, 1, 0)) != 0) {
1.101 djm 766: debug2_fr(r, "CA %s %s is not listed in %s",
1.64 markus 767: sshkey_type(key->cert->signature_key), ca_fp,
1.101 djm 768: options.trusted_user_ca_keys);
1.21 djm 769: goto out;
770: }
1.24 djm 771: /*
772: * If AuthorizedPrincipals is in use, then compare the certificate
773: * principals against the names in that file rather than matching
774: * against the username.
775: */
776: if ((principals_file = authorized_principals_file(pw)) != NULL) {
1.77 djm 777: if (match_principals_file(ssh, pw, principals_file,
778: key->cert, &principals_opts))
1.51 djm 779: found_principal = 1;
780: }
781: /* Try querying command if specified */
1.77 djm 782: if (!found_principal && match_principals_command(ssh, pw, key,
783: &principals_opts))
1.51 djm 784: found_principal = 1;
1.53 jsing 785: /* If principals file or command is specified, then require a match */
786: use_authorized_principals = principals_file != NULL ||
1.107 djm 787: options.authorized_principals_command != NULL;
1.53 jsing 788: if (!found_principal && use_authorized_principals) {
1.51 djm 789: reason = "Certificate does not contain an authorized principal";
1.77 djm 790: goto fail_reason;
1.21 djm 791: }
1.77 djm 792: if (use_authorized_principals && principals_opts == NULL)
1.101 djm 793: fatal_f("internal error: missing principals_opts");
1.105 djm 794: if (sshkey_cert_check_authority(key, 0, 1, 0,
1.53 jsing 795: use_authorized_principals ? NULL : pw->pw_name, &reason) != 0)
1.24 djm 796: goto fail_reason;
1.77 djm 797:
798: /* Check authority from options in key and from principals file/cmd */
799: if ((cert_opts = sshauthopt_from_cert(key)) == NULL) {
800: reason = "Invalid certificate options";
801: goto fail_reason;
802: }
803: if (auth_authorise_keyopts(ssh, pw, cert_opts, 0, "cert") != 0) {
804: reason = "Refused by certificate options";
1.60 djm 805: goto fail_reason;
1.77 djm 806: }
807: if (principals_opts == NULL) {
808: final_opts = cert_opts;
809: cert_opts = NULL;
810: } else {
811: if (auth_authorise_keyopts(ssh, pw, principals_opts, 0,
812: "principals") != 0) {
813: reason = "Refused by certificate principals options";
814: goto fail_reason;
815: }
816: if ((final_opts = sshauthopt_merge(principals_opts,
817: cert_opts, &reason)) == NULL) {
818: fail_reason:
819: error("%s", reason);
820: auth_debug_add("%s", reason);
821: goto out;
822: }
823: }
1.21 djm 824:
1.77 djm 825: /* Success */
1.54 djm 826: verbose("Accepted certificate ID \"%s\" (serial %llu) signed by "
827: "%s CA %s via %s", key->cert->key_id,
828: (unsigned long long)key->cert->serial,
1.64 markus 829: sshkey_type(key->cert->signature_key), ca_fp,
1.22 djm 830: options.trusted_user_ca_keys);
1.77 djm 831: if (authoptsp != NULL) {
832: *authoptsp = final_opts;
833: final_opts = NULL;
834: }
1.21 djm 835: ret = 1;
836: out:
1.77 djm 837: sshauthopt_free(principals_opts);
838: sshauthopt_free(cert_opts);
839: sshauthopt_free(final_opts);
1.36 djm 840: free(principals_file);
841: free(ca_fp);
1.21 djm 842: return ret;
843: }
844:
1.31 djm 845: /*
846: * Checks whether key is allowed in file.
847: * returns 1 if the key is allowed or 0 otherwise.
848: */
849: static int
1.77 djm 850: user_key_allowed2(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
851: char *file, struct sshauthopt **authoptsp)
1.31 djm 852: {
853: FILE *f;
854: int found_key = 0;
855:
1.77 djm 856: if (authoptsp != NULL)
857: *authoptsp = NULL;
858:
1.31 djm 859: /* Temporarily use the user's uid. */
860: temporarily_use_uid(pw);
861:
862: debug("trying public key file %s", file);
863: if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
1.77 djm 864: found_key = check_authkeys_file(ssh, pw, f, file,
865: key, authoptsp);
1.31 djm 866: fclose(f);
867: }
868:
869: restore_uid();
870: return found_key;
871: }
872:
873: /*
874: * Checks whether key is allowed in output of command.
875: * returns 1 if the key is allowed or 0 otherwise.
876: */
877: static int
1.77 djm 878: user_key_command_allowed2(struct ssh *ssh, struct passwd *user_pw,
879: struct sshkey *key, struct sshauthopt **authoptsp)
1.31 djm 880: {
1.77 djm 881: struct passwd *runas_pw = NULL;
1.50 djm 882: FILE *f = NULL;
883: int r, ok, found_key = 0;
884: int i, uid_swapped = 0, ac = 0;
1.31 djm 885: pid_t pid;
1.50 djm 886: char *username = NULL, *key_fp = NULL, *keytext = NULL;
1.78 djm 887: char uidstr[32], *tmp, *command = NULL, **av = NULL;
1.50 djm 888: void (*osigchld)(int);
1.31 djm 889:
1.77 djm 890: if (authoptsp != NULL)
891: *authoptsp = NULL;
1.50 djm 892: if (options.authorized_keys_command == NULL)
1.31 djm 893: return 0;
1.32 djm 894: if (options.authorized_keys_command_user == NULL) {
895: error("No user for AuthorizedKeysCommand specified, skipping");
896: return 0;
897: }
898:
1.50 djm 899: /*
900: * NB. all returns later this function should go via "out" to
901: * ensure the original SIGCHLD handler is restored properly.
902: */
1.98 dtucker 903: osigchld = ssh_signal(SIGCHLD, SIG_DFL);
1.50 djm 904:
905: /* Prepare and verify the user for the command */
1.32 djm 906: username = percent_expand(options.authorized_keys_command_user,
907: "u", user_pw->pw_name, (char *)NULL);
1.77 djm 908: runas_pw = getpwnam(username);
909: if (runas_pw == NULL) {
1.34 djm 910: error("AuthorizedKeysCommandUser \"%s\" not found: %s",
911: username, strerror(errno));
1.50 djm 912: goto out;
1.31 djm 913: }
914:
1.50 djm 915: /* Prepare AuthorizedKeysCommand */
916: if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash,
917: SSH_FP_DEFAULT)) == NULL) {
1.101 djm 918: error_f("sshkey_fingerprint failed");
1.31 djm 919: goto out;
920: }
1.50 djm 921: if ((r = sshkey_to_base64(key, &keytext)) != 0) {
1.101 djm 922: error_fr(r, "sshkey_to_base64 failed");
1.31 djm 923: goto out;
924: }
925:
1.50 djm 926: /* Turn the command into an argument vector */
1.108 ! djm 927: if (argv_split(options.authorized_keys_command, &ac, &av, 0) != 0) {
1.50 djm 928: error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
1.102 djm 929: options.authorized_keys_command);
1.50 djm 930: goto out;
931: }
932: if (ac == 0) {
933: error("AuthorizedKeysCommand \"%s\" yielded no arguments",
1.102 djm 934: options.authorized_keys_command);
1.31 djm 935: goto out;
936: }
1.78 djm 937: snprintf(uidstr, sizeof(uidstr), "%llu",
938: (unsigned long long)user_pw->pw_uid);
1.50 djm 939: for (i = 1; i < ac; i++) {
940: tmp = percent_expand(av[i],
1.78 djm 941: "U", uidstr,
1.50 djm 942: "u", user_pw->pw_name,
943: "h", user_pw->pw_dir,
944: "t", sshkey_ssh_name(key),
945: "f", key_fp,
946: "k", keytext,
947: (char *)NULL);
948: if (tmp == NULL)
1.101 djm 949: fatal_f("percent_expand failed");
1.50 djm 950: free(av[i]);
951: av[i] = tmp;
952: }
953: /* Prepare a printable command for logs, etc. */
1.69 djm 954: command = argv_assemble(ac, av);
1.31 djm 955:
956: /*
1.50 djm 957: * If AuthorizedKeysCommand was run without arguments
958: * then fall back to the old behaviour of passing the
959: * target username as a single argument.
1.31 djm 960: */
1.50 djm 961: if (ac == 1) {
962: av = xreallocarray(av, ac + 2, sizeof(*av));
963: av[1] = xstrdup(user_pw->pw_name);
964: av[2] = NULL;
965: /* Fix up command too, since it is used in log messages */
966: free(command);
967: xasprintf(&command, "%s %s", av[0], av[1]);
968: }
1.31 djm 969:
1.103 djm 970: if ((pid = subprocess("AuthorizedKeysCommand", command,
1.69 djm 971: ac, av, &f,
1.103 djm 972: SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD,
973: runas_pw, temporarily_use_uid, restore_uid)) == 0)
1.50 djm 974: goto out;
1.31 djm 975:
1.50 djm 976: uid_swapped = 1;
1.77 djm 977: temporarily_use_uid(runas_pw);
1.31 djm 978:
1.77 djm 979: ok = check_authkeys_file(ssh, user_pw, f,
980: options.authorized_keys_command, key, authoptsp);
1.61 djm 981:
982: fclose(f);
983: f = NULL;
1.31 djm 984:
1.70 djm 985: if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0)
1.31 djm 986: goto out;
1.50 djm 987:
988: /* Read completed successfully */
1.31 djm 989: found_key = ok;
990: out:
1.50 djm 991: if (f != NULL)
992: fclose(f);
1.98 dtucker 993: ssh_signal(SIGCHLD, osigchld);
1.50 djm 994: for (i = 0; i < ac; i++)
995: free(av[i]);
996: free(av);
997: if (uid_swapped)
998: restore_uid();
999: free(command);
1000: free(username);
1001: free(key_fp);
1002: free(keytext);
1.31 djm 1003: return found_key;
1004: }
1005:
1006: /*
1007: * Check whether key authenticates and authorises the user.
1008: */
1.1 markus 1009: int
1.77 djm 1010: user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
1011: int auth_attempt, struct sshauthopt **authoptsp)
1.1 markus 1012: {
1.89 djm 1013: u_int success = 0, i;
1.1 markus 1014: char *file;
1.77 djm 1015: struct sshauthopt *opts = NULL;
1.89 djm 1016:
1.77 djm 1017: if (authoptsp != NULL)
1018: *authoptsp = NULL;
1.21 djm 1019:
1020: if (auth_key_is_revoked(key))
1021: return 0;
1.64 markus 1022: if (sshkey_is_cert(key) &&
1023: auth_key_is_revoked(key->cert->signature_key))
1.21 djm 1024: return 0;
1025:
1.89 djm 1026: for (i = 0; !success && i < options.num_authkeys_files; i++) {
1027: if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
1028: continue;
1029: file = expand_authorized_keys(
1030: options.authorized_keys_files[i], pw);
1031: success = user_key_allowed2(ssh, pw, key, file, &opts);
1032: free(file);
1033: if (!success) {
1034: sshauthopt_free(opts);
1035: opts = NULL;
1036: }
1037: }
1038: if (success)
1039: goto out;
1040:
1.77 djm 1041: if ((success = user_cert_trusted_ca(ssh, pw, key, &opts)) != 0)
1042: goto out;
1043: sshauthopt_free(opts);
1044: opts = NULL;
1045:
1046: if ((success = user_key_command_allowed2(ssh, pw, key, &opts)) != 0)
1047: goto out;
1048: sshauthopt_free(opts);
1049: opts = NULL;
1.1 markus 1050:
1.77 djm 1051: out:
1052: if (success && authoptsp != NULL) {
1053: *authoptsp = opts;
1054: opts = NULL;
1055: }
1056: sshauthopt_free(opts);
1.1 markus 1057: return success;
1058: }
1.2 markus 1059:
1060: Authmethod method_pubkey = {
1061: "publickey",
1062: userauth_pubkey,
1063: &options.pubkey_authentication
1064: };
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