Annotation of src/usr.bin/ssh/auth2-pubkey.c, Revision 1.22
1.22 ! djm 1: /* $OpenBSD: auth2-pubkey.c,v 1.21 2010/03/04 10:36:03 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"
1.1 markus 59:
60: /* import */
61: extern ServerOptions options;
62: extern u_char *session_id2;
1.4 markus 63: extern u_int session_id2_len;
1.1 markus 64:
1.2 markus 65: static int
1.1 markus 66: userauth_pubkey(Authctxt *authctxt)
67: {
68: Buffer b;
69: Key *key = NULL;
70: char *pkalg;
71: u_char *pkblob, *sig;
72: u_int alen, blen, slen;
73: int have_sig, pktype;
74: int authenticated = 0;
75:
76: if (!authctxt->valid) {
77: debug2("userauth_pubkey: disabled because of invalid user");
78: return 0;
79: }
80: have_sig = packet_get_char();
81: if (datafellows & SSH_BUG_PKAUTH) {
82: debug2("userauth_pubkey: SSH_BUG_PKAUTH");
83: /* no explicit pkalg given */
84: pkblob = packet_get_string(&blen);
85: buffer_init(&b);
86: buffer_append(&b, pkblob, blen);
87: /* so we have to extract the pkalg from the pkblob */
88: pkalg = buffer_get_string(&b, &alen);
89: buffer_free(&b);
90: } else {
91: pkalg = packet_get_string(&alen);
92: pkblob = packet_get_string(&blen);
93: }
94: pktype = key_type_from_name(pkalg);
95: if (pktype == KEY_UNSPEC) {
96: /* this is perfectly legal */
1.3 itojun 97: logit("userauth_pubkey: unsupported public key algorithm: %s",
1.1 markus 98: pkalg);
99: goto done;
100: }
101: key = key_from_blob(pkblob, blen);
102: if (key == NULL) {
103: error("userauth_pubkey: cannot decode key: %s", pkalg);
104: goto done;
105: }
106: if (key->type != pktype) {
107: error("userauth_pubkey: type mismatch for decoded key "
108: "(received %d, expected %d)", key->type, pktype);
109: goto done;
110: }
111: if (have_sig) {
112: sig = packet_get_string(&slen);
113: packet_check_eom();
114: buffer_init(&b);
115: if (datafellows & SSH_OLD_SESSIONID) {
116: buffer_append(&b, session_id2, session_id2_len);
117: } else {
118: buffer_put_string(&b, session_id2, session_id2_len);
119: }
120: /* reconstruct packet */
121: buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
122: buffer_put_cstring(&b, authctxt->user);
123: buffer_put_cstring(&b,
124: datafellows & SSH_BUG_PKSERVICE ?
125: "ssh-userauth" :
126: authctxt->service);
127: if (datafellows & SSH_BUG_PKAUTH) {
128: buffer_put_char(&b, have_sig);
129: } else {
130: buffer_put_cstring(&b, "publickey");
131: buffer_put_char(&b, have_sig);
132: buffer_put_cstring(&b, pkalg);
133: }
134: buffer_put_string(&b, pkblob, blen);
135: #ifdef DEBUG_PK
136: buffer_dump(&b);
137: #endif
138: /* test for correct signature */
139: authenticated = 0;
140: if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
141: PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
1.6 markus 142: buffer_len(&b))) == 1)
1.1 markus 143: authenticated = 1;
1.6 markus 144: buffer_free(&b);
1.1 markus 145: xfree(sig);
146: } else {
147: debug("test whether pkalg/pkblob are acceptable");
148: packet_check_eom();
149:
150: /* XXX fake reply and always send PK_OK ? */
151: /*
152: * XXX this allows testing whether a user is allowed
153: * to login: if you happen to have a valid pubkey this
154: * message is sent. the message is NEVER sent at all
155: * if a user is not allowed to login. is this an
156: * issue? -markus
157: */
158: if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
159: packet_start(SSH2_MSG_USERAUTH_PK_OK);
160: packet_put_string(pkalg, alen);
161: packet_put_string(pkblob, blen);
162: packet_send();
163: packet_write_wait();
164: authctxt->postponed = 1;
165: }
166: }
167: if (authenticated != 1)
168: auth_clear_options();
169: done:
170: debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
171: if (key != NULL)
172: key_free(key);
173: xfree(pkalg);
174: xfree(pkblob);
175: return authenticated;
176: }
177:
178: /* return 1 if user allows given key */
179: static int
180: user_key_allowed2(struct passwd *pw, Key *key, char *file)
181: {
1.8 dtucker 182: char line[SSH_MAX_PUBKEY_BYTES];
1.20 djm 183: const char *reason;
1.18 dtucker 184: int found_key = 0;
1.1 markus 185: FILE *f;
186: u_long linenum = 0;
187: Key *found;
188: char *fp;
189:
190: /* Temporarily use the user's uid. */
191: temporarily_use_uid(pw);
192:
193: debug("trying public key file %s", file);
1.18 dtucker 194: f = auth_openkeyfile(file, pw, options.strict_modes);
1.1 markus 195:
1.18 dtucker 196: if (!f) {
1.1 markus 197: restore_uid();
198: return 0;
199: }
200:
201: found_key = 0;
1.20 djm 202: found = key_new(key_is_cert(key) ? KEY_UNSPEC : key->type);
1.1 markus 203:
1.8 dtucker 204: while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
1.7 avsm 205: char *cp, *key_options = NULL;
1.8 dtucker 206:
1.20 djm 207: auth_clear_options();
208:
1.1 markus 209: /* Skip leading whitespace, empty and comment lines. */
210: for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
211: ;
212: if (!*cp || *cp == '\n' || *cp == '#')
213: continue;
214:
215: if (key_read(found, &cp) != 1) {
216: /* no key? check if there are options for this key */
217: int quoted = 0;
218: debug2("user_key_allowed: check options: '%s'", cp);
1.7 avsm 219: key_options = cp;
1.1 markus 220: for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
221: if (*cp == '\\' && cp[1] == '"')
222: cp++; /* Skip both */
223: else if (*cp == '"')
224: quoted = !quoted;
225: }
226: /* Skip remaining whitespace. */
227: for (; *cp == ' ' || *cp == '\t'; cp++)
228: ;
229: if (key_read(found, &cp) != 1) {
230: debug2("user_key_allowed: advance: '%s'", cp);
231: /* still no key? advance to next line*/
232: continue;
233: }
234: }
1.20 djm 235: if (auth_parse_options(pw, key_options, file, linenum) != 1)
236: continue;
237: if (key->type == KEY_RSA_CERT || key->type == KEY_DSA_CERT) {
238: if (!key_is_cert_authority)
239: continue;
240: if (!key_equal(found, key->cert->signature_key))
241: continue;
242: fp = key_fingerprint(found, SSH_FP_MD5,
243: SSH_FP_HEX);
1.22 ! djm 244: debug("matching CA found: file %s, line %lu, %s %s",
! 245: file, linenum, key_type(found), fp);
1.20 djm 246: if (key_cert_check_authority(key, 0, 0, pw->pw_name,
247: &reason) != 0) {
1.22 ! djm 248: xfree(fp);
1.20 djm 249: error("%s", reason);
250: auth_debug_add("%s", reason);
251: continue;
252: }
253: if (auth_cert_constraints(&key->cert->constraints,
1.22 ! djm 254: pw) != 0) {
! 255: xfree(fp);
1.20 djm 256: continue;
1.22 ! djm 257: }
! 258: verbose("Accepted certificate ID \"%s\" "
! 259: "signed by %s CA %s via %s", key->cert->key_id,
! 260: key_type(found), fp, file);
! 261: xfree(fp);
1.20 djm 262: found_key = 1;
263: break;
264: } else if (!key_is_cert_authority && key_equal(found, key)) {
1.1 markus 265: found_key = 1;
266: debug("matching key found: file %s, line %lu",
267: file, linenum);
268: fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
269: verbose("Found matching %s key: %s",
270: key_type(found), fp);
271: xfree(fp);
272: break;
273: }
274: }
275: restore_uid();
276: fclose(f);
277: key_free(found);
278: if (!found_key)
279: debug2("key not found");
280: return found_key;
281: }
282:
1.21 djm 283: /* Authenticate a certificate key against TrustedUserCAKeys */
284: static int
285: user_cert_trusted_ca(struct passwd *pw, Key *key)
286: {
1.22 ! djm 287: char *ca_fp;
1.21 djm 288: const char *reason;
289: int ret = 0;
290:
291: if (!key_is_cert(key) || options.trusted_user_ca_keys == NULL)
292: return 0;
293:
1.22 ! djm 294: ca_fp = key_fingerprint(key->cert->signature_key,
! 295: SSH_FP_MD5, SSH_FP_HEX);
1.21 djm 296:
297: if (key_in_file(key->cert->signature_key,
298: options.trusted_user_ca_keys, 1) != 1) {
299: debug2("%s: CA %s %s is not listed in %s", __func__,
300: key_type(key->cert->signature_key), ca_fp,
301: options.trusted_user_ca_keys);
302: goto out;
303: }
304: if (key_cert_check_authority(key, 0, 1, pw->pw_name, &reason) != 0) {
305: error("%s", reason);
306: auth_debug_add("%s", reason);
307: goto out;
308: }
309: if (auth_cert_constraints(&key->cert->constraints, pw) != 0)
310: goto out;
311:
1.22 ! djm 312: verbose("Accepted certificate ID \"%s\" signed by %s CA %s via %s",
! 313: key->cert->key_id, key_type(key->cert->signature_key), ca_fp,
! 314: options.trusted_user_ca_keys);
1.21 djm 315: ret = 1;
316:
317: out:
318: if (ca_fp != NULL)
319: xfree(ca_fp);
320: return ret;
321: }
322:
1.1 markus 323: /* check whether given key is in .ssh/authorized_keys* */
324: int
325: user_key_allowed(struct passwd *pw, Key *key)
326: {
327: int success;
328: char *file;
1.21 djm 329:
330: if (auth_key_is_revoked(key))
331: return 0;
332: if (key_is_cert(key) && auth_key_is_revoked(key->cert->signature_key))
333: return 0;
334:
335: success = user_cert_trusted_ca(pw, key);
336: if (success)
337: return success;
1.1 markus 338:
339: file = authorized_keys_file(pw);
340: success = user_key_allowed2(pw, key, file);
341: xfree(file);
342: if (success)
343: return success;
344:
345: /* try suffix "2" for backward compat, too */
346: file = authorized_keys_file2(pw);
347: success = user_key_allowed2(pw, key, file);
348: xfree(file);
349: return success;
350: }
1.2 markus 351:
352: Authmethod method_pubkey = {
353: "publickey",
354: userauth_pubkey,
355: &options.pubkey_authentication
356: };
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