Annotation of src/usr.bin/ssh/auth2-pubkey.c, Revision 1.29
1.29 ! djm 1: /* $OpenBSD: auth2-pubkey.c,v 1.28 2011/05/11 04:47:06 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:
1.16 djm 30: #include <fcntl.h>
1.13 stevesk 31: #include <pwd.h>
1.14 stevesk 32: #include <stdio.h>
1.15 deraadt 33: #include <stdarg.h>
1.20 djm 34: #include <string.h>
35: #include <time.h>
1.17 dtucker 36: #include <unistd.h>
1.1 markus 37:
1.15 deraadt 38: #include "xmalloc.h"
1.8 dtucker 39: #include "ssh.h"
1.1 markus 40: #include "ssh2.h"
41: #include "packet.h"
42: #include "buffer.h"
43: #include "log.h"
44: #include "servconf.h"
45: #include "compat.h"
1.15 deraadt 46: #include "key.h"
47: #include "hostfile.h"
1.1 markus 48: #include "auth.h"
49: #include "pathnames.h"
50: #include "uidswap.h"
51: #include "auth-options.h"
52: #include "canohost.h"
1.15 deraadt 53: #ifdef GSSAPI
54: #include "ssh-gss.h"
55: #endif
1.1 markus 56: #include "monitor_wrap.h"
1.9 dtucker 57: #include "misc.h"
1.21 djm 58: #include "authfile.h"
1.24 djm 59: #include "match.h"
1.1 markus 60:
61: /* import */
62: extern ServerOptions options;
63: extern u_char *session_id2;
1.4 markus 64: extern u_int session_id2_len;
1.1 markus 65:
1.2 markus 66: static int
1.1 markus 67: userauth_pubkey(Authctxt *authctxt)
68: {
69: Buffer b;
70: Key *key = NULL;
71: char *pkalg;
72: u_char *pkblob, *sig;
73: u_int alen, blen, slen;
74: int have_sig, pktype;
75: int authenticated = 0;
76:
77: if (!authctxt->valid) {
78: debug2("userauth_pubkey: disabled because of invalid user");
79: return 0;
80: }
81: have_sig = packet_get_char();
82: if (datafellows & SSH_BUG_PKAUTH) {
83: debug2("userauth_pubkey: SSH_BUG_PKAUTH");
84: /* no explicit pkalg given */
85: pkblob = packet_get_string(&blen);
86: buffer_init(&b);
87: buffer_append(&b, pkblob, blen);
88: /* so we have to extract the pkalg from the pkblob */
89: pkalg = buffer_get_string(&b, &alen);
90: buffer_free(&b);
91: } else {
92: pkalg = packet_get_string(&alen);
93: pkblob = packet_get_string(&blen);
94: }
95: pktype = key_type_from_name(pkalg);
96: if (pktype == KEY_UNSPEC) {
97: /* this is perfectly legal */
1.3 itojun 98: logit("userauth_pubkey: unsupported public key algorithm: %s",
1.1 markus 99: pkalg);
100: goto done;
101: }
102: key = key_from_blob(pkblob, blen);
103: if (key == NULL) {
104: error("userauth_pubkey: cannot decode key: %s", pkalg);
105: goto done;
106: }
107: if (key->type != pktype) {
108: error("userauth_pubkey: type mismatch for decoded key "
109: "(received %d, expected %d)", key->type, pktype);
110: goto done;
111: }
112: if (have_sig) {
113: sig = packet_get_string(&slen);
114: packet_check_eom();
115: buffer_init(&b);
116: if (datafellows & SSH_OLD_SESSIONID) {
117: buffer_append(&b, session_id2, session_id2_len);
118: } else {
119: buffer_put_string(&b, session_id2, session_id2_len);
120: }
121: /* reconstruct packet */
122: buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
123: buffer_put_cstring(&b, authctxt->user);
124: buffer_put_cstring(&b,
125: datafellows & SSH_BUG_PKSERVICE ?
126: "ssh-userauth" :
127: authctxt->service);
128: if (datafellows & SSH_BUG_PKAUTH) {
129: buffer_put_char(&b, have_sig);
130: } else {
131: buffer_put_cstring(&b, "publickey");
132: buffer_put_char(&b, have_sig);
133: buffer_put_cstring(&b, pkalg);
134: }
135: buffer_put_string(&b, pkblob, blen);
136: #ifdef DEBUG_PK
137: buffer_dump(&b);
138: #endif
139: /* test for correct signature */
140: authenticated = 0;
141: if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
142: PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
1.6 markus 143: buffer_len(&b))) == 1)
1.1 markus 144: authenticated = 1;
1.6 markus 145: buffer_free(&b);
1.1 markus 146: xfree(sig);
147: } else {
148: debug("test whether pkalg/pkblob are acceptable");
149: packet_check_eom();
150:
151: /* XXX fake reply and always send PK_OK ? */
152: /*
153: * XXX this allows testing whether a user is allowed
154: * to login: if you happen to have a valid pubkey this
155: * message is sent. the message is NEVER sent at all
156: * if a user is not allowed to login. is this an
157: * issue? -markus
158: */
159: if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
160: packet_start(SSH2_MSG_USERAUTH_PK_OK);
161: packet_put_string(pkalg, alen);
162: packet_put_string(pkblob, blen);
163: packet_send();
164: packet_write_wait();
165: authctxt->postponed = 1;
166: }
167: }
168: if (authenticated != 1)
169: auth_clear_options();
170: done:
171: debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
172: if (key != NULL)
173: key_free(key);
174: xfree(pkalg);
175: xfree(pkblob);
176: return authenticated;
177: }
178:
1.24 djm 179: static int
180: match_principals_option(const char *principal_list, struct KeyCert *cert)
181: {
182: char *result;
183: u_int i;
184:
185: /* XXX percent_expand() sequences for authorized_principals? */
186:
187: for (i = 0; i < cert->nprincipals; i++) {
188: if ((result = match_list(cert->principals[i],
189: principal_list, NULL)) != NULL) {
190: debug3("matched principal from key options \"%.100s\"",
191: result);
192: xfree(result);
193: return 1;
194: }
195: }
196: return 0;
197: }
198:
199: static int
1.26 djm 200: match_principals_file(char *file, struct passwd *pw, struct KeyCert *cert)
1.24 djm 201: {
202: FILE *f;
1.26 djm 203: char line[SSH_MAX_PUBKEY_BYTES], *cp, *ep, *line_opts;
1.24 djm 204: u_long linenum = 0;
205: u_int i;
206:
207: temporarily_use_uid(pw);
208: debug("trying authorized principals file %s", file);
209: if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
210: restore_uid();
211: return 0;
212: }
213: while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
1.26 djm 214: /* Skip leading whitespace. */
1.24 djm 215: for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
216: ;
1.26 djm 217: /* Skip blank and comment lines. */
218: if ((ep = strchr(cp, '#')) != NULL)
219: *ep = '\0';
220: if (!*cp || *cp == '\n')
1.24 djm 221: continue;
1.26 djm 222: /* Trim trailing whitespace. */
223: ep = cp + strlen(cp) - 1;
224: while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t'))
225: *ep-- = '\0';
226: /*
227: * If the line has internal whitespace then assume it has
228: * key options.
229: */
230: line_opts = NULL;
231: if ((ep = strrchr(cp, ' ')) != NULL ||
232: (ep = strrchr(cp, '\t')) != NULL) {
233: for (; *ep == ' ' || *ep == '\t'; ep++)
1.27 deraadt 234: ;
1.26 djm 235: line_opts = cp;
236: cp = ep;
237: }
1.24 djm 238: for (i = 0; i < cert->nprincipals; i++) {
239: if (strcmp(cp, cert->principals[i]) == 0) {
240: debug3("matched principal from file \"%.100s\"",
241: cert->principals[i]);
1.26 djm 242: if (auth_parse_options(pw, line_opts,
243: file, linenum) != 1)
244: continue;
1.24 djm 245: fclose(f);
246: restore_uid();
247: return 1;
248: }
249: }
250: }
251: fclose(f);
252: restore_uid();
253: return 0;
254: }
255:
1.1 markus 256: /* return 1 if user allows given key */
257: static int
258: user_key_allowed2(struct passwd *pw, Key *key, char *file)
259: {
1.8 dtucker 260: char line[SSH_MAX_PUBKEY_BYTES];
1.20 djm 261: const char *reason;
1.18 dtucker 262: int found_key = 0;
1.1 markus 263: FILE *f;
264: u_long linenum = 0;
265: Key *found;
266: char *fp;
267:
268: /* Temporarily use the user's uid. */
269: temporarily_use_uid(pw);
270:
271: debug("trying public key file %s", file);
1.18 dtucker 272: f = auth_openkeyfile(file, pw, options.strict_modes);
1.1 markus 273:
1.18 dtucker 274: if (!f) {
1.1 markus 275: restore_uid();
276: return 0;
277: }
278:
279: found_key = 0;
1.20 djm 280: found = key_new(key_is_cert(key) ? KEY_UNSPEC : key->type);
1.1 markus 281:
1.8 dtucker 282: while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
1.7 avsm 283: char *cp, *key_options = NULL;
1.8 dtucker 284:
1.20 djm 285: auth_clear_options();
286:
1.1 markus 287: /* Skip leading whitespace, empty and comment lines. */
288: for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
289: ;
290: if (!*cp || *cp == '\n' || *cp == '#')
291: continue;
292:
293: if (key_read(found, &cp) != 1) {
294: /* no key? check if there are options for this key */
295: int quoted = 0;
296: debug2("user_key_allowed: check options: '%s'", cp);
1.7 avsm 297: key_options = cp;
1.1 markus 298: for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
299: if (*cp == '\\' && cp[1] == '"')
300: cp++; /* Skip both */
301: else if (*cp == '"')
302: quoted = !quoted;
303: }
304: /* Skip remaining whitespace. */
305: for (; *cp == ' ' || *cp == '\t'; cp++)
306: ;
307: if (key_read(found, &cp) != 1) {
308: debug2("user_key_allowed: advance: '%s'", cp);
309: /* still no key? advance to next line*/
310: continue;
311: }
312: }
1.23 djm 313: if (key_is_cert(key)) {
1.25 djm 314: if (!key_equal(found, key->cert->signature_key))
315: continue;
316: if (auth_parse_options(pw, key_options, file,
317: linenum) != 1)
318: continue;
1.20 djm 319: if (!key_is_cert_authority)
320: continue;
321: fp = key_fingerprint(found, SSH_FP_MD5,
322: SSH_FP_HEX);
1.22 djm 323: debug("matching CA found: file %s, line %lu, %s %s",
324: file, linenum, key_type(found), fp);
1.24 djm 325: /*
326: * If the user has specified a list of principals as
327: * a key option, then prefer that list to matching
328: * their username in the certificate principals list.
329: */
330: if (authorized_principals != NULL &&
331: !match_principals_option(authorized_principals,
332: key->cert)) {
333: reason = "Certificate does not contain an "
334: "authorized principal";
335: fail_reason:
1.22 djm 336: xfree(fp);
1.20 djm 337: error("%s", reason);
338: auth_debug_add("%s", reason);
339: continue;
340: }
1.24 djm 341: if (key_cert_check_authority(key, 0, 0,
342: authorized_principals == NULL ? pw->pw_name : NULL,
343: &reason) != 0)
344: goto fail_reason;
1.23 djm 345: if (auth_cert_options(key, pw) != 0) {
1.22 djm 346: xfree(fp);
1.20 djm 347: continue;
1.22 djm 348: }
349: verbose("Accepted certificate ID \"%s\" "
350: "signed by %s CA %s via %s", key->cert->key_id,
351: key_type(found), fp, file);
352: xfree(fp);
1.20 djm 353: found_key = 1;
354: break;
1.25 djm 355: } else if (key_equal(found, key)) {
356: if (auth_parse_options(pw, key_options, file,
357: linenum) != 1)
358: continue;
359: if (key_is_cert_authority)
360: continue;
1.1 markus 361: found_key = 1;
362: debug("matching key found: file %s, line %lu",
363: file, linenum);
364: fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
365: verbose("Found matching %s key: %s",
366: key_type(found), fp);
367: xfree(fp);
368: break;
369: }
370: }
371: restore_uid();
372: fclose(f);
373: key_free(found);
374: if (!found_key)
375: debug2("key not found");
376: return found_key;
377: }
378:
1.21 djm 379: /* Authenticate a certificate key against TrustedUserCAKeys */
380: static int
381: user_cert_trusted_ca(struct passwd *pw, Key *key)
382: {
1.24 djm 383: char *ca_fp, *principals_file = NULL;
1.21 djm 384: const char *reason;
385: int ret = 0;
386:
387: if (!key_is_cert(key) || options.trusted_user_ca_keys == NULL)
388: return 0;
389:
1.22 djm 390: ca_fp = key_fingerprint(key->cert->signature_key,
391: SSH_FP_MD5, SSH_FP_HEX);
1.21 djm 392:
393: if (key_in_file(key->cert->signature_key,
394: options.trusted_user_ca_keys, 1) != 1) {
395: debug2("%s: CA %s %s is not listed in %s", __func__,
396: key_type(key->cert->signature_key), ca_fp,
397: options.trusted_user_ca_keys);
398: goto out;
399: }
1.24 djm 400: /*
401: * If AuthorizedPrincipals is in use, then compare the certificate
402: * principals against the names in that file rather than matching
403: * against the username.
404: */
405: if ((principals_file = authorized_principals_file(pw)) != NULL) {
406: if (!match_principals_file(principals_file, pw, key->cert)) {
407: reason = "Certificate does not contain an "
408: "authorized principal";
409: fail_reason:
410: error("%s", reason);
411: auth_debug_add("%s", reason);
412: goto out;
413: }
1.21 djm 414: }
1.24 djm 415: if (key_cert_check_authority(key, 0, 1,
416: principals_file == NULL ? pw->pw_name : NULL, &reason) != 0)
417: goto fail_reason;
1.23 djm 418: if (auth_cert_options(key, pw) != 0)
1.21 djm 419: goto out;
420:
1.22 djm 421: verbose("Accepted certificate ID \"%s\" signed by %s CA %s via %s",
422: key->cert->key_id, key_type(key->cert->signature_key), ca_fp,
423: options.trusted_user_ca_keys);
1.21 djm 424: ret = 1;
425:
426: out:
1.24 djm 427: if (principals_file != NULL)
428: xfree(principals_file);
1.21 djm 429: if (ca_fp != NULL)
430: xfree(ca_fp);
431: return ret;
432: }
433:
1.1 markus 434: /* check whether given key is in .ssh/authorized_keys* */
435: int
436: user_key_allowed(struct passwd *pw, Key *key)
437: {
1.29 ! djm 438: u_int success, i;
1.1 markus 439: char *file;
1.21 djm 440:
441: if (auth_key_is_revoked(key))
442: return 0;
443: if (key_is_cert(key) && auth_key_is_revoked(key->cert->signature_key))
444: return 0;
445:
446: success = user_cert_trusted_ca(pw, key);
447: if (success)
448: return success;
1.1 markus 449:
1.29 ! djm 450: for (i = 0; !success && i < options.num_authkeys_files; i++) {
! 451: file = expand_authorized_keys(
! 452: options.authorized_keys_files[i], pw);
! 453: success = user_key_allowed2(pw, key, file);
! 454: xfree(file);
! 455: }
1.1 markus 456:
457: return success;
458: }
1.2 markus 459:
460: Authmethod method_pubkey = {
461: "publickey",
462: userauth_pubkey,
463: &options.pubkey_authentication
464: };
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