Annotation of src/usr.bin/ssh/auth2-pubkey.c, Revision 1.96
1.96 ! djm 1: /* $OpenBSD: auth2-pubkey.c,v 1.95 2019/11/25 00:51:37 djm Exp $ */
1.1 markus 2: /*
3: * Copyright (c) 2000 Markus Friedl. All rights reserved.
4: *
5: * Redistribution and use in source and binary forms, with or without
6: * modification, are permitted provided that the following conditions
7: * are met:
8: * 1. Redistributions of source code must retain the above copyright
9: * notice, this list of conditions and the following disclaimer.
10: * 2. Redistributions in binary form must reproduce the above copyright
11: * notice, this list of conditions and the following disclaimer in the
12: * documentation and/or other materials provided with the distribution.
13: *
14: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24: */
25:
1.10 stevesk 26:
27: #include <sys/types.h>
28: #include <sys/stat.h>
1.13 stevesk 29:
1.94 djm 30: #include <stdlib.h>
1.31 djm 31: #include <errno.h>
1.16 djm 32: #include <fcntl.h>
1.31 djm 33: #include <paths.h>
1.13 stevesk 34: #include <pwd.h>
1.31 djm 35: #include <signal.h>
1.14 stevesk 36: #include <stdio.h>
1.15 deraadt 37: #include <stdarg.h>
1.20 djm 38: #include <string.h>
39: #include <time.h>
1.17 dtucker 40: #include <unistd.h>
1.44 djm 41: #include <limits.h>
1.1 markus 42:
1.15 deraadt 43: #include "xmalloc.h"
1.8 dtucker 44: #include "ssh.h"
1.1 markus 45: #include "ssh2.h"
46: #include "packet.h"
1.81 markus 47: #include "sshbuf.h"
1.1 markus 48: #include "log.h"
1.41 millert 49: #include "misc.h"
1.1 markus 50: #include "servconf.h"
51: #include "compat.h"
1.64 markus 52: #include "sshkey.h"
1.15 deraadt 53: #include "hostfile.h"
1.1 markus 54: #include "auth.h"
55: #include "pathnames.h"
56: #include "uidswap.h"
57: #include "auth-options.h"
58: #include "canohost.h"
1.15 deraadt 59: #ifdef GSSAPI
60: #include "ssh-gss.h"
61: #endif
1.1 markus 62: #include "monitor_wrap.h"
1.21 djm 63: #include "authfile.h"
1.24 djm 64: #include "match.h"
1.50 djm 65: #include "ssherr.h"
66: #include "channels.h" /* XXX for session.h */
67: #include "session.h" /* XXX for child_set_env(); refactor? */
1.96 ! djm 68: #include "sk-api.h"
1.1 markus 69:
70: /* import */
71: extern ServerOptions options;
72: extern u_char *session_id2;
1.4 markus 73: extern u_int session_id2_len;
1.1 markus 74:
1.73 djm 75: static char *
76: format_key(const struct sshkey *key)
77: {
78: char *ret, *fp = sshkey_fingerprint(key,
79: options.fingerprint_hash, SSH_FP_DEFAULT);
80:
81: xasprintf(&ret, "%s %s", sshkey_type(key), fp);
82: free(fp);
83: return ret;
84: }
85:
1.2 markus 86: static int
1.65 markus 87: userauth_pubkey(struct ssh *ssh)
1.1 markus 88: {
1.65 markus 89: Authctxt *authctxt = ssh->authctxt;
1.77 djm 90: struct passwd *pw = authctxt->pw;
1.83 djm 91: struct sshbuf *b = NULL;
1.63 markus 92: struct sshkey *key = NULL;
1.83 djm 93: char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL;
94: u_char *pkblob = NULL, *sig = NULL, have_sig;
1.64 markus 95: size_t blen, slen;
96: int r, pktype;
1.96 ! djm 97: int req_presence = 0, authenticated = 0;
1.77 djm 98: struct sshauthopt *authopts = NULL;
1.95 djm 99: struct sshkey_sig_details *sig_details = NULL;
1.1 markus 100:
1.75 djm 101: if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 ||
102: (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 ||
103: (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0)
104: fatal("%s: parse request failed: %s", __func__, ssh_err(r));
1.87 djm 105:
106: if (log_level_get() >= SYSLOG_LEVEL_DEBUG2) {
107: char *keystring;
108: struct sshbuf *pkbuf;
109:
110: if ((pkbuf = sshbuf_from(pkblob, blen)) == NULL)
111: fatal("%s: sshbuf_from failed", __func__);
1.91 djm 112: if ((keystring = sshbuf_dtob64_string(pkbuf, 0)) == NULL)
1.87 djm 113: fatal("%s: sshbuf_dtob64 failed", __func__);
114: debug2("%s: %s user %s %s public key %s %s", __func__,
115: authctxt->valid ? "valid" : "invalid", authctxt->user,
116: have_sig ? "attempting" : "querying", pkalg, keystring);
117: sshbuf_free(pkbuf);
118: free(keystring);
119: }
120:
1.64 markus 121: pktype = sshkey_type_from_name(pkalg);
1.1 markus 122: if (pktype == KEY_UNSPEC) {
123: /* this is perfectly legal */
1.80 djm 124: verbose("%s: unsupported public key algorithm: %s",
1.55 djm 125: __func__, pkalg);
1.1 markus 126: goto done;
127: }
1.64 markus 128: if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
129: error("%s: could not parse key: %s", __func__, ssh_err(r));
130: goto done;
131: }
1.1 markus 132: if (key == NULL) {
1.55 djm 133: error("%s: cannot decode key: %s", __func__, pkalg);
1.1 markus 134: goto done;
135: }
136: if (key->type != pktype) {
1.55 djm 137: error("%s: type mismatch for decoded key "
138: "(received %d, expected %d)", __func__, key->type, pktype);
1.39 djm 139: goto done;
140: }
1.64 markus 141: if (sshkey_type_plain(key->type) == KEY_RSA &&
142: (ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
1.39 djm 143: logit("Refusing RSA key because client uses unsafe "
144: "signature scheme");
1.1 markus 145: goto done;
146: }
1.68 djm 147: if (auth2_key_already_used(authctxt, key)) {
1.64 markus 148: logit("refusing previously-used %s key", sshkey_type(key));
1.44 djm 149: goto done;
150: }
1.80 djm 151: if (match_pattern_list(pkalg, options.pubkey_key_types, 0) != 1) {
1.45 djm 152: logit("%s: key type %s not in PubkeyAcceptedKeyTypes",
153: __func__, sshkey_ssh_name(key));
154: goto done;
155: }
1.86 djm 156: if ((r = sshkey_check_cert_sigtype(key,
157: options.ca_sign_algorithms)) != 0) {
158: logit("%s: certificate signature algorithm %s: %s", __func__,
159: (key->cert == NULL || key->cert->signature_type == NULL) ?
160: "(null)" : key->cert->signature_type, ssh_err(r));
161: goto done;
162: }
1.73 djm 163: key_s = format_key(key);
164: if (sshkey_is_cert(key))
165: ca_s = format_key(key->cert->signature_key);
166:
1.1 markus 167: if (have_sig) {
1.73 djm 168: debug3("%s: have %s signature for %s%s%s",
169: __func__, pkalg, key_s,
170: ca_s == NULL ? "" : " CA ",
171: ca_s == NULL ? "" : ca_s);
1.64 markus 172: if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 ||
173: (r = sshpkt_get_end(ssh)) != 0)
174: fatal("%s: %s", __func__, ssh_err(r));
175: if ((b = sshbuf_new()) == NULL)
176: fatal("%s: sshbuf_new failed", __func__);
177: if (ssh->compat & SSH_OLD_SESSIONID) {
178: if ((r = sshbuf_put(b, session_id2,
179: session_id2_len)) != 0)
180: fatal("%s: sshbuf_put session id: %s",
181: __func__, ssh_err(r));
1.1 markus 182: } else {
1.64 markus 183: if ((r = sshbuf_put_string(b, session_id2,
184: session_id2_len)) != 0)
185: fatal("%s: sshbuf_put_string session id: %s",
186: __func__, ssh_err(r));
1.1 markus 187: }
1.83 djm 188: if (!authctxt->valid || authctxt->user == NULL) {
189: debug2("%s: disabled because of invalid user",
190: __func__);
191: goto done;
192: }
1.1 markus 193: /* reconstruct packet */
1.35 djm 194: xasprintf(&userstyle, "%s%s%s", authctxt->user,
195: authctxt->style ? ":" : "",
196: authctxt->style ? authctxt->style : "");
1.64 markus 197: if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
198: (r = sshbuf_put_cstring(b, userstyle)) != 0 ||
1.75 djm 199: (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
200: (r = sshbuf_put_cstring(b, "publickey")) != 0 ||
201: (r = sshbuf_put_u8(b, have_sig)) != 0 ||
1.85 mestre 202: (r = sshbuf_put_cstring(b, pkalg)) != 0 ||
1.75 djm 203: (r = sshbuf_put_string(b, pkblob, blen)) != 0)
1.64 markus 204: fatal("%s: build packet failed: %s",
205: __func__, ssh_err(r));
1.1 markus 206: #ifdef DEBUG_PK
1.64 markus 207: sshbuf_dump(b, stderr);
1.1 markus 208: #endif
209: /* test for correct signature */
210: authenticated = 0;
1.77 djm 211: if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) &&
1.80 djm 212: PRIVSEP(sshkey_verify(key, sig, slen,
213: sshbuf_ptr(b), sshbuf_len(b),
214: (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL,
1.95 djm 215: ssh->compat, &sig_details)) == 0) {
1.1 markus 216: authenticated = 1;
1.44 djm 217: }
1.96 ! djm 218: if (authenticated == 1 && sig_details != NULL) {
! 219: auth2_record_info(authctxt, "signature count = %u",
! 220: sig_details->sk_counter);
1.95 djm 221: debug("%s: sk_counter = %u, sk_flags = 0x%02x",
222: __func__, sig_details->sk_counter,
223: sig_details->sk_flags);
1.96 ! djm 224: req_presence = (options.pubkey_auth_options &
! 225: PUBKEYAUTH_TOUCH_REQUIRED);
! 226: if (req_presence && (sig_details->sk_flags &
! 227: SSH_SK_USER_PRESENCE_REQD) == 0) {
! 228: error("public key %s signature for %s%s from "
! 229: "%.128s port %d rejected: user presence "
! 230: "(key touch) requirement not met ", key_s,
! 231: authctxt->valid ? "" : "invalid user ",
! 232: authctxt->user, ssh_remote_ipaddr(ssh),
! 233: ssh_remote_port(ssh));
! 234: authenticated = 0;
! 235: goto done;
! 236: }
1.95 djm 237: }
1.68 djm 238: auth2_record_key(authctxt, authenticated, key);
1.1 markus 239: } else {
1.73 djm 240: debug("%s: test pkalg %s pkblob %s%s%s",
241: __func__, pkalg, key_s,
242: ca_s == NULL ? "" : " CA ",
243: ca_s == NULL ? "" : ca_s);
244:
1.64 markus 245: if ((r = sshpkt_get_end(ssh)) != 0)
246: fatal("%s: %s", __func__, ssh_err(r));
1.1 markus 247:
1.83 djm 248: if (!authctxt->valid || authctxt->user == NULL) {
249: debug2("%s: disabled because of invalid user",
250: __func__);
251: goto done;
252: }
1.1 markus 253: /* XXX fake reply and always send PK_OK ? */
254: /*
255: * XXX this allows testing whether a user is allowed
256: * to login: if you happen to have a valid pubkey this
257: * message is sent. the message is NEVER sent at all
258: * if a user is not allowed to login. is this an
259: * issue? -markus
260: */
1.77 djm 261: if (PRIVSEP(user_key_allowed(ssh, pw, key, 0, NULL))) {
1.64 markus 262: if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK))
263: != 0 ||
264: (r = sshpkt_put_cstring(ssh, pkalg)) != 0 ||
265: (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 ||
1.82 markus 266: (r = sshpkt_send(ssh)) != 0 ||
267: (r = ssh_packet_write_wait(ssh)) != 0)
1.64 markus 268: fatal("%s: %s", __func__, ssh_err(r));
1.1 markus 269: authctxt->postponed = 1;
270: }
271: }
272: done:
1.77 djm 273: if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) {
274: debug("%s: key options inconsistent with existing", __func__);
275: authenticated = 0;
276: }
1.55 djm 277: debug2("%s: authenticated %d pkalg %s", __func__, authenticated, pkalg);
1.77 djm 278:
1.84 djm 279: sshbuf_free(b);
1.77 djm 280: sshauthopt_free(authopts);
1.68 djm 281: sshkey_free(key);
1.64 markus 282: free(userstyle);
1.36 djm 283: free(pkalg);
284: free(pkblob);
1.73 djm 285: free(key_s);
286: free(ca_s);
1.83 djm 287: free(sig);
1.95 djm 288: sshkey_sig_details_free(sig_details);
1.1 markus 289: return authenticated;
290: }
291:
1.24 djm 292: static int
1.40 djm 293: match_principals_option(const char *principal_list, struct sshkey_cert *cert)
1.24 djm 294: {
295: char *result;
296: u_int i;
297:
298: /* XXX percent_expand() sequences for authorized_principals? */
299:
300: for (i = 0; i < cert->nprincipals; i++) {
301: if ((result = match_list(cert->principals[i],
302: principal_list, NULL)) != NULL) {
303: debug3("matched principal from key options \"%.100s\"",
304: result);
1.36 djm 305: free(result);
1.24 djm 306: return 1;
307: }
308: }
309: return 0;
310: }
311:
1.77 djm 312: /*
313: * Process a single authorized_principals format line. Returns 0 and sets
314: * authoptsp is principal is authorised, -1 otherwise. "loc" is used as a
315: * log preamble for file/line information.
316: */
1.24 djm 317: static int
1.77 djm 318: check_principals_line(struct ssh *ssh, char *cp, const struct sshkey_cert *cert,
319: const char *loc, struct sshauthopt **authoptsp)
1.24 djm 320: {
1.77 djm 321: u_int i, found = 0;
322: char *ep, *line_opts;
323: const char *reason = NULL;
324: struct sshauthopt *opts = NULL;
325:
326: if (authoptsp != NULL)
327: *authoptsp = NULL;
328:
329: /* Trim trailing whitespace. */
330: ep = cp + strlen(cp) - 1;
331: while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t'))
332: *ep-- = '\0';
333:
334: /*
335: * If the line has internal whitespace then assume it has
336: * key options.
337: */
338: line_opts = NULL;
339: if ((ep = strrchr(cp, ' ')) != NULL ||
340: (ep = strrchr(cp, '\t')) != NULL) {
341: for (; *ep == ' ' || *ep == '\t'; ep++)
342: ;
343: line_opts = cp;
344: cp = ep;
345: }
346: if ((opts = sshauthopt_parse(line_opts, &reason)) == NULL) {
347: debug("%s: bad principals options: %s", loc, reason);
348: auth_debug_add("%s: bad principals options: %s", loc, reason);
349: return -1;
350: }
351: /* Check principals in cert against those on line */
352: for (i = 0; i < cert->nprincipals; i++) {
353: if (strcmp(cp, cert->principals[i]) != 0)
354: continue;
355: debug3("%s: matched principal \"%.100s\"",
356: loc, cert->principals[i]);
357: found = 1;
358: }
359: if (found && authoptsp != NULL) {
360: *authoptsp = opts;
361: opts = NULL;
362: }
363: sshauthopt_free(opts);
364: return found ? 0 : -1;
365: }
366:
367: static int
368: process_principals(struct ssh *ssh, FILE *f, const char *file,
369: const struct sshkey_cert *cert, struct sshauthopt **authoptsp)
370: {
1.79 markus 371: char loc[256], *line = NULL, *cp, *ep;
372: size_t linesize = 0;
1.24 djm 373: u_long linenum = 0;
1.77 djm 374: u_int found_principal = 0;
375:
376: if (authoptsp != NULL)
377: *authoptsp = NULL;
1.24 djm 378:
1.79 markus 379: while (getline(&line, &linesize, f) != -1) {
380: linenum++;
1.62 djm 381: /* Always consume entire input */
382: if (found_principal)
383: continue;
1.77 djm 384:
1.26 djm 385: /* Skip leading whitespace. */
1.24 djm 386: for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
387: ;
1.26 djm 388: /* Skip blank and comment lines. */
389: if ((ep = strchr(cp, '#')) != NULL)
390: *ep = '\0';
391: if (!*cp || *cp == '\n')
1.24 djm 392: continue;
1.77 djm 393:
394: snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
395: if (check_principals_line(ssh, cp, cert, loc, authoptsp) == 0)
396: found_principal = 1;
1.24 djm 397: }
1.79 markus 398: free(line);
1.62 djm 399: return found_principal;
1.51 djm 400: }
401:
1.77 djm 402: /* XXX remove pw args here and elsewhere once ssh->authctxt is guaranteed */
403:
1.51 djm 404: static int
1.77 djm 405: match_principals_file(struct ssh *ssh, struct passwd *pw, char *file,
406: struct sshkey_cert *cert, struct sshauthopt **authoptsp)
1.51 djm 407: {
408: FILE *f;
409: int success;
410:
1.77 djm 411: if (authoptsp != NULL)
412: *authoptsp = NULL;
413:
1.51 djm 414: temporarily_use_uid(pw);
415: debug("trying authorized principals file %s", file);
416: if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
417: restore_uid();
418: return 0;
419: }
1.77 djm 420: success = process_principals(ssh, f, file, cert, authoptsp);
1.24 djm 421: fclose(f);
422: restore_uid();
1.51 djm 423: return success;
1.31 djm 424: }
1.24 djm 425:
1.31 djm 426: /*
1.51 djm 427: * Checks whether principal is allowed in output of command.
428: * returns 1 if the principal is allowed or 0 otherwise.
429: */
430: static int
1.77 djm 431: match_principals_command(struct ssh *ssh, struct passwd *user_pw,
432: const struct sshkey *key, struct sshauthopt **authoptsp)
1.51 djm 433: {
1.77 djm 434: struct passwd *runas_pw = NULL;
1.56 djm 435: const struct sshkey_cert *cert = key->cert;
1.51 djm 436: FILE *f = NULL;
1.56 djm 437: int r, ok, found_principal = 0;
1.51 djm 438: int i, ac = 0, uid_swapped = 0;
439: pid_t pid;
440: char *tmp, *username = NULL, *command = NULL, **av = NULL;
1.56 djm 441: char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL;
1.88 djm 442: char serial_s[32], uidstr[32];
1.51 djm 443: void (*osigchld)(int);
444:
1.77 djm 445: if (authoptsp != NULL)
446: *authoptsp = NULL;
1.51 djm 447: if (options.authorized_principals_command == NULL)
448: return 0;
449: if (options.authorized_principals_command_user == NULL) {
450: error("No user for AuthorizedPrincipalsCommand specified, "
451: "skipping");
452: return 0;
453: }
454:
455: /*
456: * NB. all returns later this function should go via "out" to
457: * ensure the original SIGCHLD handler is restored properly.
458: */
459: osigchld = signal(SIGCHLD, SIG_DFL);
460:
461: /* Prepare and verify the user for the command */
462: username = percent_expand(options.authorized_principals_command_user,
463: "u", user_pw->pw_name, (char *)NULL);
1.77 djm 464: runas_pw = getpwnam(username);
465: if (runas_pw == NULL) {
1.51 djm 466: error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s",
467: username, strerror(errno));
468: goto out;
469: }
470:
471: /* Turn the command into an argument vector */
1.69 djm 472: if (argv_split(options.authorized_principals_command, &ac, &av) != 0) {
1.51 djm 473: error("AuthorizedPrincipalsCommand \"%s\" contains "
1.90 djm 474: "invalid quotes", options.authorized_principals_command);
1.51 djm 475: goto out;
476: }
477: if (ac == 0) {
478: error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
1.90 djm 479: options.authorized_principals_command);
1.51 djm 480: goto out;
481: }
1.56 djm 482: if ((ca_fp = sshkey_fingerprint(cert->signature_key,
483: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
484: error("%s: sshkey_fingerprint failed", __func__);
485: goto out;
486: }
1.57 djm 487: if ((key_fp = sshkey_fingerprint(key,
1.56 djm 488: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
489: error("%s: sshkey_fingerprint failed", __func__);
490: goto out;
491: }
492: if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) {
493: error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
494: goto out;
495: }
496: if ((r = sshkey_to_base64(key, &keytext)) != 0) {
497: error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
498: goto out;
499: }
1.59 djm 500: snprintf(serial_s, sizeof(serial_s), "%llu",
501: (unsigned long long)cert->serial);
1.78 djm 502: snprintf(uidstr, sizeof(uidstr), "%llu",
503: (unsigned long long)user_pw->pw_uid);
1.51 djm 504: for (i = 1; i < ac; i++) {
505: tmp = percent_expand(av[i],
1.78 djm 506: "U", uidstr,
1.51 djm 507: "u", user_pw->pw_name,
508: "h", user_pw->pw_dir,
1.56 djm 509: "t", sshkey_ssh_name(key),
510: "T", sshkey_ssh_name(cert->signature_key),
511: "f", key_fp,
512: "F", ca_fp,
513: "k", keytext,
514: "K", catext,
1.58 djm 515: "i", cert->key_id,
516: "s", serial_s,
1.51 djm 517: (char *)NULL);
518: if (tmp == NULL)
519: fatal("%s: percent_expand failed", __func__);
520: free(av[i]);
521: av[i] = tmp;
522: }
523: /* Prepare a printable command for logs, etc. */
1.69 djm 524: command = argv_assemble(ac, av);
1.51 djm 525:
1.77 djm 526: if ((pid = subprocess("AuthorizedPrincipalsCommand", runas_pw, command,
1.69 djm 527: ac, av, &f,
528: SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
1.51 djm 529: goto out;
530:
531: uid_swapped = 1;
1.77 djm 532: temporarily_use_uid(runas_pw);
1.51 djm 533:
1.77 djm 534: ok = process_principals(ssh, f, "(command)", cert, authoptsp);
1.51 djm 535:
1.61 djm 536: fclose(f);
537: f = NULL;
538:
1.70 djm 539: if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0)
1.51 djm 540: goto out;
541:
542: /* Read completed successfully */
543: found_principal = ok;
544: out:
545: if (f != NULL)
546: fclose(f);
547: signal(SIGCHLD, osigchld);
548: for (i = 0; i < ac; i++)
549: free(av[i]);
550: free(av);
551: if (uid_swapped)
552: restore_uid();
553: free(command);
554: free(username);
1.56 djm 555: free(ca_fp);
556: free(key_fp);
557: free(catext);
558: free(keytext);
1.51 djm 559: return found_principal;
1.77 djm 560: }
561:
562: /*
563: * Check a single line of an authorized_keys-format file. Returns 0 if key
564: * matches, -1 otherwise. Will return key/cert options via *authoptsp
565: * on success. "loc" is used as file/line location in log messages.
566: */
567: static int
568: check_authkey_line(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
569: char *cp, const char *loc, struct sshauthopt **authoptsp)
570: {
571: int want_keytype = sshkey_is_cert(key) ? KEY_UNSPEC : key->type;
572: struct sshkey *found = NULL;
573: struct sshauthopt *keyopts = NULL, *certopts = NULL, *finalopts = NULL;
574: char *key_options = NULL, *fp = NULL;
575: const char *reason = NULL;
576: int ret = -1;
577:
578: if (authoptsp != NULL)
579: *authoptsp = NULL;
580:
581: if ((found = sshkey_new(want_keytype)) == NULL) {
582: debug3("%s: keytype %d failed", __func__, want_keytype);
583: goto out;
584: }
585:
586: /* XXX djm: peek at key type in line and skip if unwanted */
587:
588: if (sshkey_read(found, &cp) != 0) {
589: /* no key? check for options */
590: debug2("%s: check options: '%s'", loc, cp);
591: key_options = cp;
1.93 djm 592: if (sshkey_advance_past_options(&cp) != 0) {
1.77 djm 593: reason = "invalid key option string";
594: goto fail_reason;
595: }
596: skip_space(&cp);
597: if (sshkey_read(found, &cp) != 0) {
598: /* still no key? advance to next line*/
599: debug2("%s: advance: '%s'", loc, cp);
600: goto out;
601: }
602: }
603: /* Parse key options now; we need to know if this is a CA key */
604: if ((keyopts = sshauthopt_parse(key_options, &reason)) == NULL) {
605: debug("%s: bad key options: %s", loc, reason);
606: auth_debug_add("%s: bad key options: %s", loc, reason);
607: goto out;
608: }
609: /* Ignore keys that don't match or incorrectly marked as CAs */
610: if (sshkey_is_cert(key)) {
611: /* Certificate; check signature key against CA */
612: if (!sshkey_equal(found, key->cert->signature_key) ||
613: !keyopts->cert_authority)
614: goto out;
615: } else {
616: /* Plain key: check it against key found in file */
617: if (!sshkey_equal(found, key) || keyopts->cert_authority)
618: goto out;
619: }
620:
621: /* We have a candidate key, perform authorisation checks */
622: if ((fp = sshkey_fingerprint(found,
623: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
624: fatal("%s: fingerprint failed", __func__);
625:
626: debug("%s: matching %s found: %s %s", loc,
627: sshkey_is_cert(key) ? "CA" : "key", sshkey_type(found), fp);
628:
629: if (auth_authorise_keyopts(ssh, pw, keyopts,
630: sshkey_is_cert(key), loc) != 0) {
631: reason = "Refused by key options";
632: goto fail_reason;
633: }
634: /* That's all we need for plain keys. */
635: if (!sshkey_is_cert(key)) {
636: verbose("Accepted key %s %s found at %s",
637: sshkey_type(found), fp, loc);
638: finalopts = keyopts;
639: keyopts = NULL;
640: goto success;
641: }
642:
643: /*
644: * Additional authorisation for certificates.
645: */
646:
647: /* Parse and check options present in certificate */
648: if ((certopts = sshauthopt_from_cert(key)) == NULL) {
649: reason = "Invalid certificate options";
650: goto fail_reason;
651: }
652: if (auth_authorise_keyopts(ssh, pw, certopts, 0, loc) != 0) {
653: reason = "Refused by certificate options";
654: goto fail_reason;
655: }
656: if ((finalopts = sshauthopt_merge(keyopts, certopts, &reason)) == NULL)
657: goto fail_reason;
658:
659: /*
660: * If the user has specified a list of principals as
661: * a key option, then prefer that list to matching
662: * their username in the certificate principals list.
663: */
664: if (keyopts->cert_principals != NULL &&
665: !match_principals_option(keyopts->cert_principals, key->cert)) {
666: reason = "Certificate does not contain an authorized principal";
667: goto fail_reason;
668: }
669: if (sshkey_cert_check_authority(key, 0, 0,
670: keyopts->cert_principals == NULL ? pw->pw_name : NULL, &reason) != 0)
671: goto fail_reason;
672:
673: verbose("Accepted certificate ID \"%s\" (serial %llu) "
674: "signed by CA %s %s found at %s",
675: key->cert->key_id,
676: (unsigned long long)key->cert->serial,
677: sshkey_type(found), fp, loc);
678:
679: success:
680: if (finalopts == NULL)
681: fatal("%s: internal error: missing options", __func__);
682: if (authoptsp != NULL) {
683: *authoptsp = finalopts;
684: finalopts = NULL;
685: }
686: /* success */
687: ret = 0;
688: goto out;
689:
690: fail_reason:
691: error("%s", reason);
692: auth_debug_add("%s", reason);
693: out:
694: free(fp);
695: sshauthopt_free(keyopts);
696: sshauthopt_free(certopts);
697: sshauthopt_free(finalopts);
698: sshkey_free(found);
699: return ret;
700: }
701:
1.51 djm 702: /*
1.31 djm 703: * Checks whether key is allowed in authorized_keys-format file,
704: * returns 1 if the key is allowed or 0 otherwise.
705: */
1.1 markus 706: static int
1.77 djm 707: check_authkeys_file(struct ssh *ssh, struct passwd *pw, FILE *f,
708: char *file, struct sshkey *key, struct sshauthopt **authoptsp)
1.1 markus 709: {
1.79 markus 710: char *cp, *line = NULL, loc[256];
711: size_t linesize = 0;
1.18 dtucker 712: int found_key = 0;
1.1 markus 713: u_long linenum = 0;
1.77 djm 714:
715: if (authoptsp != NULL)
716: *authoptsp = NULL;
1.1 markus 717:
1.79 markus 718: while (getline(&line, &linesize, f) != -1) {
719: linenum++;
1.71 djm 720: /* Always consume entire file */
1.62 djm 721: if (found_key)
722: continue;
1.20 djm 723:
1.1 markus 724: /* Skip leading whitespace, empty and comment lines. */
1.77 djm 725: cp = line;
726: skip_space(&cp);
1.1 markus 727: if (!*cp || *cp == '\n' || *cp == '#')
728: continue;
1.77 djm 729: snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
730: if (check_authkey_line(ssh, pw, key, cp, loc, authoptsp) == 0)
1.20 djm 731: found_key = 1;
1.1 markus 732: }
1.79 markus 733: free(line);
1.1 markus 734: return found_key;
735: }
736:
1.21 djm 737: /* Authenticate a certificate key against TrustedUserCAKeys */
738: static int
1.77 djm 739: user_cert_trusted_ca(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
740: struct sshauthopt **authoptsp)
1.21 djm 741: {
1.24 djm 742: char *ca_fp, *principals_file = NULL;
1.21 djm 743: const char *reason;
1.77 djm 744: struct sshauthopt *principals_opts = NULL, *cert_opts = NULL;
745: struct sshauthopt *final_opts = NULL;
1.64 markus 746: int r, ret = 0, found_principal = 0, use_authorized_principals;
1.21 djm 747:
1.77 djm 748: if (authoptsp != NULL)
749: *authoptsp = NULL;
750:
1.64 markus 751: if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL)
1.21 djm 752: return 0;
753:
1.46 djm 754: if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
755: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
756: return 0;
1.21 djm 757:
1.64 markus 758: if ((r = sshkey_in_file(key->cert->signature_key,
759: options.trusted_user_ca_keys, 1, 0)) != 0) {
760: debug2("%s: CA %s %s is not listed in %s: %s", __func__,
761: sshkey_type(key->cert->signature_key), ca_fp,
762: options.trusted_user_ca_keys, ssh_err(r));
1.21 djm 763: goto out;
764: }
1.24 djm 765: /*
766: * If AuthorizedPrincipals is in use, then compare the certificate
767: * principals against the names in that file rather than matching
768: * against the username.
769: */
770: if ((principals_file = authorized_principals_file(pw)) != NULL) {
1.77 djm 771: if (match_principals_file(ssh, pw, principals_file,
772: key->cert, &principals_opts))
1.51 djm 773: found_principal = 1;
774: }
775: /* Try querying command if specified */
1.77 djm 776: if (!found_principal && match_principals_command(ssh, pw, key,
777: &principals_opts))
1.51 djm 778: found_principal = 1;
1.53 jsing 779: /* If principals file or command is specified, then require a match */
780: use_authorized_principals = principals_file != NULL ||
781: options.authorized_principals_command != NULL;
782: if (!found_principal && use_authorized_principals) {
1.51 djm 783: reason = "Certificate does not contain an authorized principal";
1.77 djm 784: goto fail_reason;
1.21 djm 785: }
1.77 djm 786: if (use_authorized_principals && principals_opts == NULL)
787: fatal("%s: internal error: missing principals_opts", __func__);
1.64 markus 788: if (sshkey_cert_check_authority(key, 0, 1,
1.53 jsing 789: use_authorized_principals ? NULL : pw->pw_name, &reason) != 0)
1.24 djm 790: goto fail_reason;
1.77 djm 791:
792: /* Check authority from options in key and from principals file/cmd */
793: if ((cert_opts = sshauthopt_from_cert(key)) == NULL) {
794: reason = "Invalid certificate options";
795: goto fail_reason;
796: }
797: if (auth_authorise_keyopts(ssh, pw, cert_opts, 0, "cert") != 0) {
798: reason = "Refused by certificate options";
1.60 djm 799: goto fail_reason;
1.77 djm 800: }
801: if (principals_opts == NULL) {
802: final_opts = cert_opts;
803: cert_opts = NULL;
804: } else {
805: if (auth_authorise_keyopts(ssh, pw, principals_opts, 0,
806: "principals") != 0) {
807: reason = "Refused by certificate principals options";
808: goto fail_reason;
809: }
810: if ((final_opts = sshauthopt_merge(principals_opts,
811: cert_opts, &reason)) == NULL) {
812: fail_reason:
813: error("%s", reason);
814: auth_debug_add("%s", reason);
815: goto out;
816: }
817: }
1.21 djm 818:
1.77 djm 819: /* Success */
1.54 djm 820: verbose("Accepted certificate ID \"%s\" (serial %llu) signed by "
821: "%s CA %s via %s", key->cert->key_id,
822: (unsigned long long)key->cert->serial,
1.64 markus 823: sshkey_type(key->cert->signature_key), ca_fp,
1.22 djm 824: options.trusted_user_ca_keys);
1.77 djm 825: if (authoptsp != NULL) {
826: *authoptsp = final_opts;
827: final_opts = NULL;
828: }
1.21 djm 829: ret = 1;
830: out:
1.77 djm 831: sshauthopt_free(principals_opts);
832: sshauthopt_free(cert_opts);
833: sshauthopt_free(final_opts);
1.36 djm 834: free(principals_file);
835: free(ca_fp);
1.21 djm 836: return ret;
837: }
838:
1.31 djm 839: /*
840: * Checks whether key is allowed in file.
841: * returns 1 if the key is allowed or 0 otherwise.
842: */
843: static int
1.77 djm 844: user_key_allowed2(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
845: char *file, struct sshauthopt **authoptsp)
1.31 djm 846: {
847: FILE *f;
848: int found_key = 0;
849:
1.77 djm 850: if (authoptsp != NULL)
851: *authoptsp = NULL;
852:
1.31 djm 853: /* Temporarily use the user's uid. */
854: temporarily_use_uid(pw);
855:
856: debug("trying public key file %s", file);
857: if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
1.77 djm 858: found_key = check_authkeys_file(ssh, pw, f, file,
859: key, authoptsp);
1.31 djm 860: fclose(f);
861: }
862:
863: restore_uid();
864: return found_key;
865: }
866:
867: /*
868: * Checks whether key is allowed in output of command.
869: * returns 1 if the key is allowed or 0 otherwise.
870: */
871: static int
1.77 djm 872: user_key_command_allowed2(struct ssh *ssh, struct passwd *user_pw,
873: struct sshkey *key, struct sshauthopt **authoptsp)
1.31 djm 874: {
1.77 djm 875: struct passwd *runas_pw = NULL;
1.50 djm 876: FILE *f = NULL;
877: int r, ok, found_key = 0;
878: int i, uid_swapped = 0, ac = 0;
1.31 djm 879: pid_t pid;
1.50 djm 880: char *username = NULL, *key_fp = NULL, *keytext = NULL;
1.78 djm 881: char uidstr[32], *tmp, *command = NULL, **av = NULL;
1.50 djm 882: void (*osigchld)(int);
1.31 djm 883:
1.77 djm 884: if (authoptsp != NULL)
885: *authoptsp = NULL;
1.50 djm 886: if (options.authorized_keys_command == NULL)
1.31 djm 887: return 0;
1.32 djm 888: if (options.authorized_keys_command_user == NULL) {
889: error("No user for AuthorizedKeysCommand specified, skipping");
890: return 0;
891: }
892:
1.50 djm 893: /*
894: * NB. all returns later this function should go via "out" to
895: * ensure the original SIGCHLD handler is restored properly.
896: */
897: osigchld = signal(SIGCHLD, SIG_DFL);
898:
899: /* Prepare and verify the user for the command */
1.32 djm 900: username = percent_expand(options.authorized_keys_command_user,
901: "u", user_pw->pw_name, (char *)NULL);
1.77 djm 902: runas_pw = getpwnam(username);
903: if (runas_pw == NULL) {
1.34 djm 904: error("AuthorizedKeysCommandUser \"%s\" not found: %s",
905: username, strerror(errno));
1.50 djm 906: goto out;
1.31 djm 907: }
908:
1.50 djm 909: /* Prepare AuthorizedKeysCommand */
910: if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash,
911: SSH_FP_DEFAULT)) == NULL) {
912: error("%s: sshkey_fingerprint failed", __func__);
1.31 djm 913: goto out;
914: }
1.50 djm 915: if ((r = sshkey_to_base64(key, &keytext)) != 0) {
916: error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
1.31 djm 917: goto out;
918: }
919:
1.50 djm 920: /* Turn the command into an argument vector */
1.69 djm 921: if (argv_split(options.authorized_keys_command, &ac, &av) != 0) {
1.50 djm 922: error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
923: command);
924: goto out;
925: }
926: if (ac == 0) {
927: error("AuthorizedKeysCommand \"%s\" yielded no arguments",
928: command);
1.31 djm 929: goto out;
930: }
1.78 djm 931: snprintf(uidstr, sizeof(uidstr), "%llu",
932: (unsigned long long)user_pw->pw_uid);
1.50 djm 933: for (i = 1; i < ac; i++) {
934: tmp = percent_expand(av[i],
1.78 djm 935: "U", uidstr,
1.50 djm 936: "u", user_pw->pw_name,
937: "h", user_pw->pw_dir,
938: "t", sshkey_ssh_name(key),
939: "f", key_fp,
940: "k", keytext,
941: (char *)NULL);
942: if (tmp == NULL)
943: fatal("%s: percent_expand failed", __func__);
944: free(av[i]);
945: av[i] = tmp;
946: }
947: /* Prepare a printable command for logs, etc. */
1.69 djm 948: command = argv_assemble(ac, av);
1.31 djm 949:
950: /*
1.50 djm 951: * If AuthorizedKeysCommand was run without arguments
952: * then fall back to the old behaviour of passing the
953: * target username as a single argument.
1.31 djm 954: */
1.50 djm 955: if (ac == 1) {
956: av = xreallocarray(av, ac + 2, sizeof(*av));
957: av[1] = xstrdup(user_pw->pw_name);
958: av[2] = NULL;
959: /* Fix up command too, since it is used in log messages */
960: free(command);
961: xasprintf(&command, "%s %s", av[0], av[1]);
962: }
1.31 djm 963:
1.77 djm 964: if ((pid = subprocess("AuthorizedKeysCommand", runas_pw, command,
1.69 djm 965: ac, av, &f,
966: SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
1.50 djm 967: goto out;
1.31 djm 968:
1.50 djm 969: uid_swapped = 1;
1.77 djm 970: temporarily_use_uid(runas_pw);
1.31 djm 971:
1.77 djm 972: ok = check_authkeys_file(ssh, user_pw, f,
973: options.authorized_keys_command, key, authoptsp);
1.61 djm 974:
975: fclose(f);
976: f = NULL;
1.31 djm 977:
1.70 djm 978: if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0)
1.31 djm 979: goto out;
1.50 djm 980:
981: /* Read completed successfully */
1.31 djm 982: found_key = ok;
983: out:
1.50 djm 984: if (f != NULL)
985: fclose(f);
986: signal(SIGCHLD, osigchld);
987: for (i = 0; i < ac; i++)
988: free(av[i]);
989: free(av);
990: if (uid_swapped)
991: restore_uid();
992: free(command);
993: free(username);
994: free(key_fp);
995: free(keytext);
1.31 djm 996: return found_key;
997: }
998:
999: /*
1000: * Check whether key authenticates and authorises the user.
1001: */
1.1 markus 1002: int
1.77 djm 1003: user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
1004: int auth_attempt, struct sshauthopt **authoptsp)
1.1 markus 1005: {
1.89 djm 1006: u_int success = 0, i;
1.1 markus 1007: char *file;
1.77 djm 1008: struct sshauthopt *opts = NULL;
1.89 djm 1009:
1.77 djm 1010: if (authoptsp != NULL)
1011: *authoptsp = NULL;
1.21 djm 1012:
1013: if (auth_key_is_revoked(key))
1014: return 0;
1.64 markus 1015: if (sshkey_is_cert(key) &&
1016: auth_key_is_revoked(key->cert->signature_key))
1.21 djm 1017: return 0;
1018:
1.89 djm 1019: for (i = 0; !success && i < options.num_authkeys_files; i++) {
1020: if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
1021: continue;
1022: file = expand_authorized_keys(
1023: options.authorized_keys_files[i], pw);
1024: success = user_key_allowed2(ssh, pw, key, file, &opts);
1025: free(file);
1026: if (!success) {
1027: sshauthopt_free(opts);
1028: opts = NULL;
1029: }
1030: }
1031: if (success)
1032: goto out;
1033:
1.77 djm 1034: if ((success = user_cert_trusted_ca(ssh, pw, key, &opts)) != 0)
1035: goto out;
1036: sshauthopt_free(opts);
1037: opts = NULL;
1038:
1039: if ((success = user_key_command_allowed2(ssh, pw, key, &opts)) != 0)
1040: goto out;
1041: sshauthopt_free(opts);
1042: opts = NULL;
1.1 markus 1043:
1.77 djm 1044: out:
1045: if (success && authoptsp != NULL) {
1046: *authoptsp = opts;
1047: opts = NULL;
1048: }
1049: sshauthopt_free(opts);
1.1 markus 1050: return success;
1051: }
1.2 markus 1052:
1053: Authmethod method_pubkey = {
1054: "publickey",
1055: userauth_pubkey,
1056: &options.pubkey_authentication
1057: };
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