Annotation of src/usr.bin/ssh/auth2-pubkey.c, Revision 1.110
1.110 ! djm 1: /* $OpenBSD: auth2-pubkey.c,v 1.109 2021/07/23 03:37:52 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;
1.110 ! djm 376: u_long linenum = 0, nonblank = 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:
1.110 ! djm 397: nonblank++;
1.77 djm 398: snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
399: if (check_principals_line(ssh, cp, cert, loc, authoptsp) == 0)
400: found_principal = 1;
1.24 djm 401: }
1.110 ! djm 402: debug2_f("%s: processed %lu/%lu lines", file, nonblank, linenum);
1.79 markus 403: free(line);
1.62 djm 404: return found_principal;
1.51 djm 405: }
406:
1.77 djm 407: /* XXX remove pw args here and elsewhere once ssh->authctxt is guaranteed */
408:
1.51 djm 409: static int
1.77 djm 410: match_principals_file(struct ssh *ssh, struct passwd *pw, char *file,
411: struct sshkey_cert *cert, struct sshauthopt **authoptsp)
1.51 djm 412: {
413: FILE *f;
414: int success;
415:
1.77 djm 416: if (authoptsp != NULL)
417: *authoptsp = NULL;
418:
1.51 djm 419: temporarily_use_uid(pw);
420: debug("trying authorized principals file %s", file);
421: if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
422: restore_uid();
423: return 0;
424: }
1.77 djm 425: success = process_principals(ssh, f, file, cert, authoptsp);
1.24 djm 426: fclose(f);
427: restore_uid();
1.51 djm 428: return success;
1.31 djm 429: }
1.24 djm 430:
1.31 djm 431: /*
1.51 djm 432: * Checks whether principal is allowed in output of command.
433: * returns 1 if the principal is allowed or 0 otherwise.
434: */
435: static int
1.77 djm 436: match_principals_command(struct ssh *ssh, struct passwd *user_pw,
437: const struct sshkey *key, struct sshauthopt **authoptsp)
1.51 djm 438: {
1.77 djm 439: struct passwd *runas_pw = NULL;
1.56 djm 440: const struct sshkey_cert *cert = key->cert;
1.51 djm 441: FILE *f = NULL;
1.56 djm 442: int r, ok, found_principal = 0;
1.51 djm 443: int i, ac = 0, uid_swapped = 0;
444: pid_t pid;
445: char *tmp, *username = NULL, *command = NULL, **av = NULL;
1.56 djm 446: char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL;
1.88 djm 447: char serial_s[32], uidstr[32];
1.51 djm 448: void (*osigchld)(int);
449:
1.77 djm 450: if (authoptsp != NULL)
451: *authoptsp = NULL;
1.51 djm 452: if (options.authorized_principals_command == NULL)
453: return 0;
454: if (options.authorized_principals_command_user == NULL) {
455: error("No user for AuthorizedPrincipalsCommand specified, "
456: "skipping");
457: return 0;
458: }
459:
460: /*
461: * NB. all returns later this function should go via "out" to
462: * ensure the original SIGCHLD handler is restored properly.
463: */
1.98 dtucker 464: osigchld = ssh_signal(SIGCHLD, SIG_DFL);
1.51 djm 465:
466: /* Prepare and verify the user for the command */
467: username = percent_expand(options.authorized_principals_command_user,
468: "u", user_pw->pw_name, (char *)NULL);
1.77 djm 469: runas_pw = getpwnam(username);
470: if (runas_pw == NULL) {
1.51 djm 471: error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s",
472: username, strerror(errno));
473: goto out;
474: }
475:
476: /* Turn the command into an argument vector */
1.108 djm 477: if (argv_split(options.authorized_principals_command,
478: &ac, &av, 0) != 0) {
1.51 djm 479: error("AuthorizedPrincipalsCommand \"%s\" contains "
1.90 djm 480: "invalid quotes", options.authorized_principals_command);
1.51 djm 481: goto out;
482: }
483: if (ac == 0) {
484: error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
1.90 djm 485: options.authorized_principals_command);
1.51 djm 486: goto out;
487: }
1.56 djm 488: if ((ca_fp = sshkey_fingerprint(cert->signature_key,
489: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1.101 djm 490: error_f("sshkey_fingerprint failed");
1.56 djm 491: goto out;
492: }
1.57 djm 493: if ((key_fp = sshkey_fingerprint(key,
1.56 djm 494: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1.101 djm 495: error_f("sshkey_fingerprint failed");
1.56 djm 496: goto out;
497: }
498: if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) {
1.101 djm 499: error_fr(r, "sshkey_to_base64 failed");
1.56 djm 500: goto out;
501: }
502: if ((r = sshkey_to_base64(key, &keytext)) != 0) {
1.101 djm 503: error_fr(r, "sshkey_to_base64 failed");
1.56 djm 504: goto out;
505: }
1.59 djm 506: snprintf(serial_s, sizeof(serial_s), "%llu",
507: (unsigned long long)cert->serial);
1.78 djm 508: snprintf(uidstr, sizeof(uidstr), "%llu",
509: (unsigned long long)user_pw->pw_uid);
1.51 djm 510: for (i = 1; i < ac; i++) {
511: tmp = percent_expand(av[i],
1.78 djm 512: "U", uidstr,
1.51 djm 513: "u", user_pw->pw_name,
514: "h", user_pw->pw_dir,
1.56 djm 515: "t", sshkey_ssh_name(key),
516: "T", sshkey_ssh_name(cert->signature_key),
517: "f", key_fp,
518: "F", ca_fp,
519: "k", keytext,
520: "K", catext,
1.58 djm 521: "i", cert->key_id,
522: "s", serial_s,
1.51 djm 523: (char *)NULL);
524: if (tmp == NULL)
1.101 djm 525: fatal_f("percent_expand failed");
1.51 djm 526: free(av[i]);
527: av[i] = tmp;
528: }
529: /* Prepare a printable command for logs, etc. */
1.69 djm 530: command = argv_assemble(ac, av);
1.51 djm 531:
1.103 djm 532: if ((pid = subprocess("AuthorizedPrincipalsCommand", command,
1.69 djm 533: ac, av, &f,
1.103 djm 534: SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD,
535: runas_pw, temporarily_use_uid, restore_uid)) == 0)
1.51 djm 536: goto out;
537:
538: uid_swapped = 1;
1.77 djm 539: temporarily_use_uid(runas_pw);
1.51 djm 540:
1.77 djm 541: ok = process_principals(ssh, f, "(command)", cert, authoptsp);
1.51 djm 542:
1.61 djm 543: fclose(f);
544: f = NULL;
545:
1.70 djm 546: if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0)
1.51 djm 547: goto out;
548:
549: /* Read completed successfully */
550: found_principal = ok;
551: out:
552: if (f != NULL)
553: fclose(f);
1.98 dtucker 554: ssh_signal(SIGCHLD, osigchld);
1.51 djm 555: for (i = 0; i < ac; i++)
556: free(av[i]);
557: free(av);
558: if (uid_swapped)
559: restore_uid();
560: free(command);
561: free(username);
1.56 djm 562: free(ca_fp);
563: free(key_fp);
564: free(catext);
565: free(keytext);
1.51 djm 566: return found_principal;
1.77 djm 567: }
568:
569: /*
570: * Check a single line of an authorized_keys-format file. Returns 0 if key
571: * matches, -1 otherwise. Will return key/cert options via *authoptsp
572: * on success. "loc" is used as file/line location in log messages.
573: */
574: static int
575: check_authkey_line(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
576: char *cp, const char *loc, struct sshauthopt **authoptsp)
577: {
578: int want_keytype = sshkey_is_cert(key) ? KEY_UNSPEC : key->type;
579: struct sshkey *found = NULL;
580: struct sshauthopt *keyopts = NULL, *certopts = NULL, *finalopts = NULL;
581: char *key_options = NULL, *fp = NULL;
582: const char *reason = NULL;
583: int ret = -1;
584:
585: if (authoptsp != NULL)
586: *authoptsp = NULL;
587:
588: if ((found = sshkey_new(want_keytype)) == NULL) {
1.101 djm 589: debug3_f("keytype %d failed", want_keytype);
1.77 djm 590: goto out;
591: }
592:
593: /* XXX djm: peek at key type in line and skip if unwanted */
594:
595: if (sshkey_read(found, &cp) != 0) {
596: /* no key? check for options */
597: debug2("%s: check options: '%s'", loc, cp);
598: key_options = cp;
1.93 djm 599: if (sshkey_advance_past_options(&cp) != 0) {
1.77 djm 600: reason = "invalid key option string";
601: goto fail_reason;
602: }
603: skip_space(&cp);
604: if (sshkey_read(found, &cp) != 0) {
605: /* still no key? advance to next line*/
606: debug2("%s: advance: '%s'", loc, cp);
607: goto out;
608: }
609: }
610: /* Parse key options now; we need to know if this is a CA key */
611: if ((keyopts = sshauthopt_parse(key_options, &reason)) == NULL) {
612: debug("%s: bad key options: %s", loc, reason);
613: auth_debug_add("%s: bad key options: %s", loc, reason);
614: goto out;
615: }
616: /* Ignore keys that don't match or incorrectly marked as CAs */
617: if (sshkey_is_cert(key)) {
618: /* Certificate; check signature key against CA */
619: if (!sshkey_equal(found, key->cert->signature_key) ||
620: !keyopts->cert_authority)
621: goto out;
622: } else {
623: /* Plain key: check it against key found in file */
624: if (!sshkey_equal(found, key) || keyopts->cert_authority)
625: goto out;
626: }
627:
628: /* We have a candidate key, perform authorisation checks */
629: if ((fp = sshkey_fingerprint(found,
630: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
1.101 djm 631: fatal_f("fingerprint failed");
1.77 djm 632:
633: debug("%s: matching %s found: %s %s", loc,
634: sshkey_is_cert(key) ? "CA" : "key", sshkey_type(found), fp);
635:
636: if (auth_authorise_keyopts(ssh, pw, keyopts,
637: sshkey_is_cert(key), loc) != 0) {
638: reason = "Refused by key options";
639: goto fail_reason;
640: }
641: /* That's all we need for plain keys. */
642: if (!sshkey_is_cert(key)) {
643: verbose("Accepted key %s %s found at %s",
644: sshkey_type(found), fp, loc);
645: finalopts = keyopts;
646: keyopts = NULL;
647: goto success;
648: }
649:
650: /*
651: * Additional authorisation for certificates.
652: */
653:
654: /* Parse and check options present in certificate */
655: if ((certopts = sshauthopt_from_cert(key)) == NULL) {
656: reason = "Invalid certificate options";
657: goto fail_reason;
658: }
659: if (auth_authorise_keyopts(ssh, pw, certopts, 0, loc) != 0) {
660: reason = "Refused by certificate options";
661: goto fail_reason;
662: }
663: if ((finalopts = sshauthopt_merge(keyopts, certopts, &reason)) == NULL)
664: goto fail_reason;
665:
666: /*
667: * If the user has specified a list of principals as
668: * a key option, then prefer that list to matching
669: * their username in the certificate principals list.
670: */
671: if (keyopts->cert_principals != NULL &&
672: !match_principals_option(keyopts->cert_principals, key->cert)) {
673: reason = "Certificate does not contain an authorized principal";
674: goto fail_reason;
675: }
1.109 djm 676: if (sshkey_cert_check_authority_now(key, 0, 0, 0,
1.107 djm 677: keyopts->cert_principals == NULL ? pw->pw_name : NULL,
678: &reason) != 0)
1.77 djm 679: goto fail_reason;
680:
681: verbose("Accepted certificate ID \"%s\" (serial %llu) "
682: "signed by CA %s %s found at %s",
683: key->cert->key_id,
684: (unsigned long long)key->cert->serial,
685: sshkey_type(found), fp, loc);
686:
687: success:
688: if (finalopts == NULL)
1.101 djm 689: fatal_f("internal error: missing options");
1.77 djm 690: if (authoptsp != NULL) {
691: *authoptsp = finalopts;
692: finalopts = NULL;
693: }
694: /* success */
695: ret = 0;
696: goto out;
697:
698: fail_reason:
699: error("%s", reason);
700: auth_debug_add("%s", reason);
701: out:
702: free(fp);
703: sshauthopt_free(keyopts);
704: sshauthopt_free(certopts);
705: sshauthopt_free(finalopts);
706: sshkey_free(found);
707: return ret;
708: }
709:
1.51 djm 710: /*
1.31 djm 711: * Checks whether key is allowed in authorized_keys-format file,
712: * returns 1 if the key is allowed or 0 otherwise.
713: */
1.1 markus 714: static int
1.77 djm 715: check_authkeys_file(struct ssh *ssh, struct passwd *pw, FILE *f,
716: char *file, struct sshkey *key, struct sshauthopt **authoptsp)
1.1 markus 717: {
1.79 markus 718: char *cp, *line = NULL, loc[256];
719: size_t linesize = 0;
1.18 dtucker 720: int found_key = 0;
1.110 ! djm 721: u_long linenum = 0, nonblank = 0;
1.77 djm 722:
723: if (authoptsp != NULL)
724: *authoptsp = NULL;
1.1 markus 725:
1.79 markus 726: while (getline(&line, &linesize, f) != -1) {
727: linenum++;
1.71 djm 728: /* Always consume entire file */
1.62 djm 729: if (found_key)
730: continue;
1.20 djm 731:
1.1 markus 732: /* Skip leading whitespace, empty and comment lines. */
1.77 djm 733: cp = line;
734: skip_space(&cp);
1.1 markus 735: if (!*cp || *cp == '\n' || *cp == '#')
736: continue;
1.110 ! djm 737:
! 738: nonblank++;
1.77 djm 739: snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
740: if (check_authkey_line(ssh, pw, key, cp, loc, authoptsp) == 0)
1.20 djm 741: found_key = 1;
1.1 markus 742: }
1.79 markus 743: free(line);
1.110 ! djm 744: debug2_f("%s: processed %lu/%lu lines", file, nonblank, linenum);
1.1 markus 745: return found_key;
746: }
747:
1.21 djm 748: /* Authenticate a certificate key against TrustedUserCAKeys */
749: static int
1.77 djm 750: user_cert_trusted_ca(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
751: struct sshauthopt **authoptsp)
1.21 djm 752: {
1.24 djm 753: char *ca_fp, *principals_file = NULL;
1.21 djm 754: const char *reason;
1.77 djm 755: struct sshauthopt *principals_opts = NULL, *cert_opts = NULL;
756: struct sshauthopt *final_opts = NULL;
1.64 markus 757: int r, ret = 0, found_principal = 0, use_authorized_principals;
1.21 djm 758:
1.77 djm 759: if (authoptsp != NULL)
760: *authoptsp = NULL;
761:
1.64 markus 762: if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL)
1.21 djm 763: return 0;
764:
1.46 djm 765: if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
766: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
767: return 0;
1.21 djm 768:
1.64 markus 769: if ((r = sshkey_in_file(key->cert->signature_key,
770: options.trusted_user_ca_keys, 1, 0)) != 0) {
1.101 djm 771: debug2_fr(r, "CA %s %s is not listed in %s",
1.64 markus 772: sshkey_type(key->cert->signature_key), ca_fp,
1.101 djm 773: options.trusted_user_ca_keys);
1.21 djm 774: goto out;
775: }
1.24 djm 776: /*
777: * If AuthorizedPrincipals is in use, then compare the certificate
778: * principals against the names in that file rather than matching
779: * against the username.
780: */
781: if ((principals_file = authorized_principals_file(pw)) != NULL) {
1.77 djm 782: if (match_principals_file(ssh, pw, principals_file,
783: key->cert, &principals_opts))
1.51 djm 784: found_principal = 1;
785: }
786: /* Try querying command if specified */
1.77 djm 787: if (!found_principal && match_principals_command(ssh, pw, key,
788: &principals_opts))
1.51 djm 789: found_principal = 1;
1.53 jsing 790: /* If principals file or command is specified, then require a match */
791: use_authorized_principals = principals_file != NULL ||
1.107 djm 792: options.authorized_principals_command != NULL;
1.53 jsing 793: if (!found_principal && use_authorized_principals) {
1.51 djm 794: reason = "Certificate does not contain an authorized principal";
1.77 djm 795: goto fail_reason;
1.21 djm 796: }
1.77 djm 797: if (use_authorized_principals && principals_opts == NULL)
1.101 djm 798: fatal_f("internal error: missing principals_opts");
1.109 djm 799: if (sshkey_cert_check_authority_now(key, 0, 1, 0,
1.53 jsing 800: use_authorized_principals ? NULL : pw->pw_name, &reason) != 0)
1.24 djm 801: goto fail_reason;
1.77 djm 802:
803: /* Check authority from options in key and from principals file/cmd */
804: if ((cert_opts = sshauthopt_from_cert(key)) == NULL) {
805: reason = "Invalid certificate options";
806: goto fail_reason;
807: }
808: if (auth_authorise_keyopts(ssh, pw, cert_opts, 0, "cert") != 0) {
809: reason = "Refused by certificate options";
1.60 djm 810: goto fail_reason;
1.77 djm 811: }
812: if (principals_opts == NULL) {
813: final_opts = cert_opts;
814: cert_opts = NULL;
815: } else {
816: if (auth_authorise_keyopts(ssh, pw, principals_opts, 0,
817: "principals") != 0) {
818: reason = "Refused by certificate principals options";
819: goto fail_reason;
820: }
821: if ((final_opts = sshauthopt_merge(principals_opts,
822: cert_opts, &reason)) == NULL) {
823: fail_reason:
824: error("%s", reason);
825: auth_debug_add("%s", reason);
826: goto out;
827: }
828: }
1.21 djm 829:
1.77 djm 830: /* Success */
1.54 djm 831: verbose("Accepted certificate ID \"%s\" (serial %llu) signed by "
832: "%s CA %s via %s", key->cert->key_id,
833: (unsigned long long)key->cert->serial,
1.64 markus 834: sshkey_type(key->cert->signature_key), ca_fp,
1.22 djm 835: options.trusted_user_ca_keys);
1.77 djm 836: if (authoptsp != NULL) {
837: *authoptsp = final_opts;
838: final_opts = NULL;
839: }
1.21 djm 840: ret = 1;
841: out:
1.77 djm 842: sshauthopt_free(principals_opts);
843: sshauthopt_free(cert_opts);
844: sshauthopt_free(final_opts);
1.36 djm 845: free(principals_file);
846: free(ca_fp);
1.21 djm 847: return ret;
848: }
849:
1.31 djm 850: /*
851: * Checks whether key is allowed in file.
852: * returns 1 if the key is allowed or 0 otherwise.
853: */
854: static int
1.77 djm 855: user_key_allowed2(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
856: char *file, struct sshauthopt **authoptsp)
1.31 djm 857: {
858: FILE *f;
859: int found_key = 0;
860:
1.77 djm 861: if (authoptsp != NULL)
862: *authoptsp = NULL;
863:
1.31 djm 864: /* Temporarily use the user's uid. */
865: temporarily_use_uid(pw);
866:
867: debug("trying public key file %s", file);
868: if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
1.77 djm 869: found_key = check_authkeys_file(ssh, pw, f, file,
870: key, authoptsp);
1.31 djm 871: fclose(f);
872: }
873:
874: restore_uid();
875: return found_key;
876: }
877:
878: /*
879: * Checks whether key is allowed in output of command.
880: * returns 1 if the key is allowed or 0 otherwise.
881: */
882: static int
1.77 djm 883: user_key_command_allowed2(struct ssh *ssh, struct passwd *user_pw,
884: struct sshkey *key, struct sshauthopt **authoptsp)
1.31 djm 885: {
1.77 djm 886: struct passwd *runas_pw = NULL;
1.50 djm 887: FILE *f = NULL;
888: int r, ok, found_key = 0;
889: int i, uid_swapped = 0, ac = 0;
1.31 djm 890: pid_t pid;
1.50 djm 891: char *username = NULL, *key_fp = NULL, *keytext = NULL;
1.78 djm 892: char uidstr[32], *tmp, *command = NULL, **av = NULL;
1.50 djm 893: void (*osigchld)(int);
1.31 djm 894:
1.77 djm 895: if (authoptsp != NULL)
896: *authoptsp = NULL;
1.50 djm 897: if (options.authorized_keys_command == NULL)
1.31 djm 898: return 0;
1.32 djm 899: if (options.authorized_keys_command_user == NULL) {
900: error("No user for AuthorizedKeysCommand specified, skipping");
901: return 0;
902: }
903:
1.50 djm 904: /*
905: * NB. all returns later this function should go via "out" to
906: * ensure the original SIGCHLD handler is restored properly.
907: */
1.98 dtucker 908: osigchld = ssh_signal(SIGCHLD, SIG_DFL);
1.50 djm 909:
910: /* Prepare and verify the user for the command */
1.32 djm 911: username = percent_expand(options.authorized_keys_command_user,
912: "u", user_pw->pw_name, (char *)NULL);
1.77 djm 913: runas_pw = getpwnam(username);
914: if (runas_pw == NULL) {
1.34 djm 915: error("AuthorizedKeysCommandUser \"%s\" not found: %s",
916: username, strerror(errno));
1.50 djm 917: goto out;
1.31 djm 918: }
919:
1.50 djm 920: /* Prepare AuthorizedKeysCommand */
921: if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash,
922: SSH_FP_DEFAULT)) == NULL) {
1.101 djm 923: error_f("sshkey_fingerprint failed");
1.31 djm 924: goto out;
925: }
1.50 djm 926: if ((r = sshkey_to_base64(key, &keytext)) != 0) {
1.101 djm 927: error_fr(r, "sshkey_to_base64 failed");
1.31 djm 928: goto out;
929: }
930:
1.50 djm 931: /* Turn the command into an argument vector */
1.108 djm 932: if (argv_split(options.authorized_keys_command, &ac, &av, 0) != 0) {
1.50 djm 933: error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
1.102 djm 934: options.authorized_keys_command);
1.50 djm 935: goto out;
936: }
937: if (ac == 0) {
938: error("AuthorizedKeysCommand \"%s\" yielded no arguments",
1.102 djm 939: options.authorized_keys_command);
1.31 djm 940: goto out;
941: }
1.78 djm 942: snprintf(uidstr, sizeof(uidstr), "%llu",
943: (unsigned long long)user_pw->pw_uid);
1.50 djm 944: for (i = 1; i < ac; i++) {
945: tmp = percent_expand(av[i],
1.78 djm 946: "U", uidstr,
1.50 djm 947: "u", user_pw->pw_name,
948: "h", user_pw->pw_dir,
949: "t", sshkey_ssh_name(key),
950: "f", key_fp,
951: "k", keytext,
952: (char *)NULL);
953: if (tmp == NULL)
1.101 djm 954: fatal_f("percent_expand failed");
1.50 djm 955: free(av[i]);
956: av[i] = tmp;
957: }
958: /* Prepare a printable command for logs, etc. */
1.69 djm 959: command = argv_assemble(ac, av);
1.31 djm 960:
961: /*
1.50 djm 962: * If AuthorizedKeysCommand was run without arguments
963: * then fall back to the old behaviour of passing the
964: * target username as a single argument.
1.31 djm 965: */
1.50 djm 966: if (ac == 1) {
967: av = xreallocarray(av, ac + 2, sizeof(*av));
968: av[1] = xstrdup(user_pw->pw_name);
969: av[2] = NULL;
970: /* Fix up command too, since it is used in log messages */
971: free(command);
972: xasprintf(&command, "%s %s", av[0], av[1]);
973: }
1.31 djm 974:
1.103 djm 975: if ((pid = subprocess("AuthorizedKeysCommand", command,
1.69 djm 976: ac, av, &f,
1.103 djm 977: SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD,
978: runas_pw, temporarily_use_uid, restore_uid)) == 0)
1.50 djm 979: goto out;
1.31 djm 980:
1.50 djm 981: uid_swapped = 1;
1.77 djm 982: temporarily_use_uid(runas_pw);
1.31 djm 983:
1.77 djm 984: ok = check_authkeys_file(ssh, user_pw, f,
985: options.authorized_keys_command, key, authoptsp);
1.61 djm 986:
987: fclose(f);
988: f = NULL;
1.31 djm 989:
1.70 djm 990: if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0)
1.31 djm 991: goto out;
1.50 djm 992:
993: /* Read completed successfully */
1.31 djm 994: found_key = ok;
995: out:
1.50 djm 996: if (f != NULL)
997: fclose(f);
1.98 dtucker 998: ssh_signal(SIGCHLD, osigchld);
1.50 djm 999: for (i = 0; i < ac; i++)
1000: free(av[i]);
1001: free(av);
1002: if (uid_swapped)
1003: restore_uid();
1004: free(command);
1005: free(username);
1006: free(key_fp);
1007: free(keytext);
1.31 djm 1008: return found_key;
1009: }
1010:
1011: /*
1012: * Check whether key authenticates and authorises the user.
1013: */
1.1 markus 1014: int
1.77 djm 1015: user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
1016: int auth_attempt, struct sshauthopt **authoptsp)
1.1 markus 1017: {
1.89 djm 1018: u_int success = 0, i;
1.1 markus 1019: char *file;
1.77 djm 1020: struct sshauthopt *opts = NULL;
1.89 djm 1021:
1.77 djm 1022: if (authoptsp != NULL)
1023: *authoptsp = NULL;
1.21 djm 1024:
1025: if (auth_key_is_revoked(key))
1026: return 0;
1.64 markus 1027: if (sshkey_is_cert(key) &&
1028: auth_key_is_revoked(key->cert->signature_key))
1.21 djm 1029: return 0;
1030:
1.89 djm 1031: for (i = 0; !success && i < options.num_authkeys_files; i++) {
1032: if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
1033: continue;
1034: file = expand_authorized_keys(
1035: options.authorized_keys_files[i], pw);
1036: success = user_key_allowed2(ssh, pw, key, file, &opts);
1037: free(file);
1038: if (!success) {
1039: sshauthopt_free(opts);
1040: opts = NULL;
1041: }
1042: }
1043: if (success)
1044: goto out;
1045:
1.77 djm 1046: if ((success = user_cert_trusted_ca(ssh, pw, key, &opts)) != 0)
1047: goto out;
1048: sshauthopt_free(opts);
1049: opts = NULL;
1050:
1051: if ((success = user_key_command_allowed2(ssh, pw, key, &opts)) != 0)
1052: goto out;
1053: sshauthopt_free(opts);
1054: opts = NULL;
1.1 markus 1055:
1.77 djm 1056: out:
1057: if (success && authoptsp != NULL) {
1058: *authoptsp = opts;
1059: opts = NULL;
1060: }
1061: sshauthopt_free(opts);
1.1 markus 1062: return success;
1063: }
1.2 markus 1064:
1065: Authmethod method_pubkey = {
1066: "publickey",
1067: userauth_pubkey,
1068: &options.pubkey_authentication
1069: };