Annotation of src/usr.bin/ssh/auth2-pubkey.c, Revision 1.25
1.25 ! djm 1: /* $OpenBSD: auth2-pubkey.c,v 1.24 2010/05/07 11:30:29 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
200: match_principals_file(const char *file, struct passwd *pw, struct KeyCert *cert)
201: {
202: FILE *f;
203: char line[SSH_MAX_PUBKEY_BYTES], *cp;
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) {
214: /* Skip leading whitespace, empty and comment lines. */
215: for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
216: ;
217: if (!*cp || *cp == '\n' || *cp == '#')
218: continue;
219: line[strcspn(line, "\n")] = '\0';
220:
221: for (i = 0; i < cert->nprincipals; i++) {
222: if (strcmp(cp, cert->principals[i]) == 0) {
223: debug3("matched principal from file \"%.100s\"",
224: cert->principals[i]);
225: fclose(f);
226: restore_uid();
227: return 1;
228: }
229: }
230: }
231: fclose(f);
232: restore_uid();
233: return 0;
234: }
235:
1.1 markus 236: /* return 1 if user allows given key */
237: static int
238: user_key_allowed2(struct passwd *pw, Key *key, char *file)
239: {
1.8 dtucker 240: char line[SSH_MAX_PUBKEY_BYTES];
1.20 djm 241: const char *reason;
1.18 dtucker 242: int found_key = 0;
1.1 markus 243: FILE *f;
244: u_long linenum = 0;
245: Key *found;
246: char *fp;
247:
248: /* Temporarily use the user's uid. */
249: temporarily_use_uid(pw);
250:
251: debug("trying public key file %s", file);
1.18 dtucker 252: f = auth_openkeyfile(file, pw, options.strict_modes);
1.1 markus 253:
1.18 dtucker 254: if (!f) {
1.1 markus 255: restore_uid();
256: return 0;
257: }
258:
259: found_key = 0;
1.20 djm 260: found = key_new(key_is_cert(key) ? KEY_UNSPEC : key->type);
1.1 markus 261:
1.8 dtucker 262: while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
1.7 avsm 263: char *cp, *key_options = NULL;
1.8 dtucker 264:
1.20 djm 265: auth_clear_options();
266:
1.1 markus 267: /* Skip leading whitespace, empty and comment lines. */
268: for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
269: ;
270: if (!*cp || *cp == '\n' || *cp == '#')
271: continue;
272:
273: if (key_read(found, &cp) != 1) {
274: /* no key? check if there are options for this key */
275: int quoted = 0;
276: debug2("user_key_allowed: check options: '%s'", cp);
1.7 avsm 277: key_options = cp;
1.1 markus 278: for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
279: if (*cp == '\\' && cp[1] == '"')
280: cp++; /* Skip both */
281: else if (*cp == '"')
282: quoted = !quoted;
283: }
284: /* Skip remaining whitespace. */
285: for (; *cp == ' ' || *cp == '\t'; cp++)
286: ;
287: if (key_read(found, &cp) != 1) {
288: debug2("user_key_allowed: advance: '%s'", cp);
289: /* still no key? advance to next line*/
290: continue;
291: }
292: }
1.23 djm 293: if (key_is_cert(key)) {
1.25 ! djm 294: if (!key_equal(found, key->cert->signature_key))
! 295: continue;
! 296: if (auth_parse_options(pw, key_options, file,
! 297: linenum) != 1)
! 298: continue;
1.20 djm 299: if (!key_is_cert_authority)
300: continue;
301: fp = key_fingerprint(found, SSH_FP_MD5,
302: SSH_FP_HEX);
1.22 djm 303: debug("matching CA found: file %s, line %lu, %s %s",
304: file, linenum, key_type(found), fp);
1.24 djm 305: /*
306: * If the user has specified a list of principals as
307: * a key option, then prefer that list to matching
308: * their username in the certificate principals list.
309: */
310: if (authorized_principals != NULL &&
311: !match_principals_option(authorized_principals,
312: key->cert)) {
313: reason = "Certificate does not contain an "
314: "authorized principal";
315: fail_reason:
1.22 djm 316: xfree(fp);
1.20 djm 317: error("%s", reason);
318: auth_debug_add("%s", reason);
319: continue;
320: }
1.24 djm 321: if (key_cert_check_authority(key, 0, 0,
322: authorized_principals == NULL ? pw->pw_name : NULL,
323: &reason) != 0)
324: goto fail_reason;
1.23 djm 325: if (auth_cert_options(key, pw) != 0) {
1.22 djm 326: xfree(fp);
1.20 djm 327: continue;
1.22 djm 328: }
329: verbose("Accepted certificate ID \"%s\" "
330: "signed by %s CA %s via %s", key->cert->key_id,
331: key_type(found), fp, file);
332: xfree(fp);
1.20 djm 333: found_key = 1;
334: break;
1.25 ! djm 335: } else if (key_equal(found, key)) {
! 336: if (auth_parse_options(pw, key_options, file,
! 337: linenum) != 1)
! 338: continue;
! 339: if (key_is_cert_authority)
! 340: continue;
1.1 markus 341: found_key = 1;
342: debug("matching key found: file %s, line %lu",
343: file, linenum);
344: fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
345: verbose("Found matching %s key: %s",
346: key_type(found), fp);
347: xfree(fp);
348: break;
349: }
350: }
351: restore_uid();
352: fclose(f);
353: key_free(found);
354: if (!found_key)
355: debug2("key not found");
356: return found_key;
357: }
358:
1.21 djm 359: /* Authenticate a certificate key against TrustedUserCAKeys */
360: static int
361: user_cert_trusted_ca(struct passwd *pw, Key *key)
362: {
1.24 djm 363: char *ca_fp, *principals_file = NULL;
1.21 djm 364: const char *reason;
365: int ret = 0;
366:
367: if (!key_is_cert(key) || options.trusted_user_ca_keys == NULL)
368: return 0;
369:
1.22 djm 370: ca_fp = key_fingerprint(key->cert->signature_key,
371: SSH_FP_MD5, SSH_FP_HEX);
1.21 djm 372:
373: if (key_in_file(key->cert->signature_key,
374: options.trusted_user_ca_keys, 1) != 1) {
375: debug2("%s: CA %s %s is not listed in %s", __func__,
376: key_type(key->cert->signature_key), ca_fp,
377: options.trusted_user_ca_keys);
378: goto out;
379: }
1.24 djm 380: /*
381: * If AuthorizedPrincipals is in use, then compare the certificate
382: * principals against the names in that file rather than matching
383: * against the username.
384: */
385: if ((principals_file = authorized_principals_file(pw)) != NULL) {
386: if (!match_principals_file(principals_file, pw, key->cert)) {
387: reason = "Certificate does not contain an "
388: "authorized principal";
389: fail_reason:
390: error("%s", reason);
391: auth_debug_add("%s", reason);
392: goto out;
393: }
1.21 djm 394: }
1.24 djm 395: if (key_cert_check_authority(key, 0, 1,
396: principals_file == NULL ? pw->pw_name : NULL, &reason) != 0)
397: goto fail_reason;
1.23 djm 398: if (auth_cert_options(key, pw) != 0)
1.21 djm 399: goto out;
400:
1.22 djm 401: verbose("Accepted certificate ID \"%s\" signed by %s CA %s via %s",
402: key->cert->key_id, key_type(key->cert->signature_key), ca_fp,
403: options.trusted_user_ca_keys);
1.21 djm 404: ret = 1;
405:
406: out:
1.24 djm 407: if (principals_file != NULL)
408: xfree(principals_file);
1.21 djm 409: if (ca_fp != NULL)
410: xfree(ca_fp);
411: return ret;
412: }
413:
1.1 markus 414: /* check whether given key is in .ssh/authorized_keys* */
415: int
416: user_key_allowed(struct passwd *pw, Key *key)
417: {
418: int success;
419: char *file;
1.21 djm 420:
421: if (auth_key_is_revoked(key))
422: return 0;
423: if (key_is_cert(key) && auth_key_is_revoked(key->cert->signature_key))
424: return 0;
425:
426: success = user_cert_trusted_ca(pw, key);
427: if (success)
428: return success;
1.1 markus 429:
430: file = authorized_keys_file(pw);
431: success = user_key_allowed2(pw, key, file);
432: xfree(file);
433: if (success)
434: return success;
435:
436: /* try suffix "2" for backward compat, too */
437: file = authorized_keys_file2(pw);
438: success = user_key_allowed2(pw, key, file);
439: xfree(file);
440: return success;
441: }
1.2 markus 442:
443: Authmethod method_pubkey = {
444: "publickey",
445: userauth_pubkey,
446: &options.pubkey_authentication
447: };
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