Annotation of src/usr.bin/ssh/auth2-pubkey.c, Revision 1.24
1.24 ! djm 1: /* $OpenBSD: auth2-pubkey.c,v 1.23 2010/04/16 01:47:26 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: }
1.20 djm 293: if (auth_parse_options(pw, key_options, file, linenum) != 1)
294: continue;
1.23 djm 295: if (key_is_cert(key)) {
1.20 djm 296: if (!key_is_cert_authority)
297: continue;
298: if (!key_equal(found, key->cert->signature_key))
299: continue;
300: fp = key_fingerprint(found, SSH_FP_MD5,
301: SSH_FP_HEX);
1.22 djm 302: debug("matching CA found: file %s, line %lu, %s %s",
303: file, linenum, key_type(found), fp);
1.24 ! djm 304: /*
! 305: * If the user has specified a list of principals as
! 306: * a key option, then prefer that list to matching
! 307: * their username in the certificate principals list.
! 308: */
! 309: if (authorized_principals != NULL &&
! 310: !match_principals_option(authorized_principals,
! 311: key->cert)) {
! 312: reason = "Certificate does not contain an "
! 313: "authorized principal";
! 314: fail_reason:
1.22 djm 315: xfree(fp);
1.20 djm 316: error("%s", reason);
317: auth_debug_add("%s", reason);
318: continue;
319: }
1.24 ! djm 320: if (key_cert_check_authority(key, 0, 0,
! 321: authorized_principals == NULL ? pw->pw_name : NULL,
! 322: &reason) != 0)
! 323: goto fail_reason;
1.23 djm 324: if (auth_cert_options(key, pw) != 0) {
1.22 djm 325: xfree(fp);
1.20 djm 326: continue;
1.22 djm 327: }
328: verbose("Accepted certificate ID \"%s\" "
329: "signed by %s CA %s via %s", key->cert->key_id,
330: key_type(found), fp, file);
331: xfree(fp);
1.20 djm 332: found_key = 1;
333: break;
334: } else if (!key_is_cert_authority && key_equal(found, key)) {
1.1 markus 335: found_key = 1;
336: debug("matching key found: file %s, line %lu",
337: file, linenum);
338: fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
339: verbose("Found matching %s key: %s",
340: key_type(found), fp);
341: xfree(fp);
342: break;
343: }
344: }
345: restore_uid();
346: fclose(f);
347: key_free(found);
348: if (!found_key)
349: debug2("key not found");
350: return found_key;
351: }
352:
1.21 djm 353: /* Authenticate a certificate key against TrustedUserCAKeys */
354: static int
355: user_cert_trusted_ca(struct passwd *pw, Key *key)
356: {
1.24 ! djm 357: char *ca_fp, *principals_file = NULL;
1.21 djm 358: const char *reason;
359: int ret = 0;
360:
361: if (!key_is_cert(key) || options.trusted_user_ca_keys == NULL)
362: return 0;
363:
1.22 djm 364: ca_fp = key_fingerprint(key->cert->signature_key,
365: SSH_FP_MD5, SSH_FP_HEX);
1.21 djm 366:
367: if (key_in_file(key->cert->signature_key,
368: options.trusted_user_ca_keys, 1) != 1) {
369: debug2("%s: CA %s %s is not listed in %s", __func__,
370: key_type(key->cert->signature_key), ca_fp,
371: options.trusted_user_ca_keys);
372: goto out;
373: }
1.24 ! djm 374: /*
! 375: * If AuthorizedPrincipals is in use, then compare the certificate
! 376: * principals against the names in that file rather than matching
! 377: * against the username.
! 378: */
! 379: if ((principals_file = authorized_principals_file(pw)) != NULL) {
! 380: if (!match_principals_file(principals_file, pw, key->cert)) {
! 381: reason = "Certificate does not contain an "
! 382: "authorized principal";
! 383: fail_reason:
! 384: error("%s", reason);
! 385: auth_debug_add("%s", reason);
! 386: goto out;
! 387: }
1.21 djm 388: }
1.24 ! djm 389: if (key_cert_check_authority(key, 0, 1,
! 390: principals_file == NULL ? pw->pw_name : NULL, &reason) != 0)
! 391: goto fail_reason;
1.23 djm 392: if (auth_cert_options(key, pw) != 0)
1.21 djm 393: goto out;
394:
1.22 djm 395: verbose("Accepted certificate ID \"%s\" signed by %s CA %s via %s",
396: key->cert->key_id, key_type(key->cert->signature_key), ca_fp,
397: options.trusted_user_ca_keys);
1.21 djm 398: ret = 1;
399:
400: out:
1.24 ! djm 401: if (principals_file != NULL)
! 402: xfree(principals_file);
1.21 djm 403: if (ca_fp != NULL)
404: xfree(ca_fp);
405: return ret;
406: }
407:
1.1 markus 408: /* check whether given key is in .ssh/authorized_keys* */
409: int
410: user_key_allowed(struct passwd *pw, Key *key)
411: {
412: int success;
413: char *file;
1.21 djm 414:
415: if (auth_key_is_revoked(key))
416: return 0;
417: if (key_is_cert(key) && auth_key_is_revoked(key->cert->signature_key))
418: return 0;
419:
420: success = user_cert_trusted_ca(pw, key);
421: if (success)
422: return success;
1.1 markus 423:
424: file = authorized_keys_file(pw);
425: success = user_key_allowed2(pw, key, file);
426: xfree(file);
427: if (success)
428: return success;
429:
430: /* try suffix "2" for backward compat, too */
431: file = authorized_keys_file2(pw);
432: success = user_key_allowed2(pw, key, file);
433: xfree(file);
434: return success;
435: }
1.2 markus 436:
437: Authmethod method_pubkey = {
438: "publickey",
439: userauth_pubkey,
440: &options.pubkey_authentication
441: };
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