Annotation of src/usr.bin/ssh/auth2-pubkey.c, Revision 1.9.4.1
1.9.4.1 ! brad 1: /* $OpenBSD: auth2-pubkey.c,v 1.15 2006/08/03 03:34:41 deraadt 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:
26:
1.9.4.1 ! brad 27: #include <sys/types.h>
! 28: #include <sys/stat.h>
! 29:
! 30: #include <pwd.h>
! 31: #include <stdio.h>
! 32: #include <stdarg.h>
! 33:
! 34: #include "xmalloc.h"
1.8 dtucker 35: #include "ssh.h"
1.1 markus 36: #include "ssh2.h"
37: #include "packet.h"
38: #include "buffer.h"
39: #include "log.h"
40: #include "servconf.h"
41: #include "compat.h"
42: #include "key.h"
1.9.4.1 ! brad 43: #include "hostfile.h"
! 44: #include "auth.h"
1.1 markus 45: #include "pathnames.h"
46: #include "uidswap.h"
47: #include "auth-options.h"
48: #include "canohost.h"
1.9.4.1 ! brad 49: #ifdef GSSAPI
! 50: #include "ssh-gss.h"
! 51: #endif
1.1 markus 52: #include "monitor_wrap.h"
1.9 dtucker 53: #include "misc.h"
1.1 markus 54:
55: /* import */
56: extern ServerOptions options;
57: extern u_char *session_id2;
1.4 markus 58: extern u_int session_id2_len;
1.1 markus 59:
1.2 markus 60: static int
1.1 markus 61: userauth_pubkey(Authctxt *authctxt)
62: {
63: Buffer b;
64: Key *key = NULL;
65: char *pkalg;
66: u_char *pkblob, *sig;
67: u_int alen, blen, slen;
68: int have_sig, pktype;
69: int authenticated = 0;
70:
71: if (!authctxt->valid) {
72: debug2("userauth_pubkey: disabled because of invalid user");
73: return 0;
74: }
75: have_sig = packet_get_char();
76: if (datafellows & SSH_BUG_PKAUTH) {
77: debug2("userauth_pubkey: SSH_BUG_PKAUTH");
78: /* no explicit pkalg given */
79: pkblob = packet_get_string(&blen);
80: buffer_init(&b);
81: buffer_append(&b, pkblob, blen);
82: /* so we have to extract the pkalg from the pkblob */
83: pkalg = buffer_get_string(&b, &alen);
84: buffer_free(&b);
85: } else {
86: pkalg = packet_get_string(&alen);
87: pkblob = packet_get_string(&blen);
88: }
89: pktype = key_type_from_name(pkalg);
90: if (pktype == KEY_UNSPEC) {
91: /* this is perfectly legal */
1.3 itojun 92: logit("userauth_pubkey: unsupported public key algorithm: %s",
1.1 markus 93: pkalg);
94: goto done;
95: }
96: key = key_from_blob(pkblob, blen);
97: if (key == NULL) {
98: error("userauth_pubkey: cannot decode key: %s", pkalg);
99: goto done;
100: }
101: if (key->type != pktype) {
102: error("userauth_pubkey: type mismatch for decoded key "
103: "(received %d, expected %d)", key->type, pktype);
104: goto done;
105: }
106: if (have_sig) {
107: sig = packet_get_string(&slen);
108: packet_check_eom();
109: buffer_init(&b);
110: if (datafellows & SSH_OLD_SESSIONID) {
111: buffer_append(&b, session_id2, session_id2_len);
112: } else {
113: buffer_put_string(&b, session_id2, session_id2_len);
114: }
115: /* reconstruct packet */
116: buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
117: buffer_put_cstring(&b, authctxt->user);
118: buffer_put_cstring(&b,
119: datafellows & SSH_BUG_PKSERVICE ?
120: "ssh-userauth" :
121: authctxt->service);
122: if (datafellows & SSH_BUG_PKAUTH) {
123: buffer_put_char(&b, have_sig);
124: } else {
125: buffer_put_cstring(&b, "publickey");
126: buffer_put_char(&b, have_sig);
127: buffer_put_cstring(&b, pkalg);
128: }
129: buffer_put_string(&b, pkblob, blen);
130: #ifdef DEBUG_PK
131: buffer_dump(&b);
132: #endif
133: /* test for correct signature */
134: authenticated = 0;
135: if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
136: PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
1.6 markus 137: buffer_len(&b))) == 1)
1.1 markus 138: authenticated = 1;
1.6 markus 139: buffer_free(&b);
1.1 markus 140: xfree(sig);
141: } else {
142: debug("test whether pkalg/pkblob are acceptable");
143: packet_check_eom();
144:
145: /* XXX fake reply and always send PK_OK ? */
146: /*
147: * XXX this allows testing whether a user is allowed
148: * to login: if you happen to have a valid pubkey this
149: * message is sent. the message is NEVER sent at all
150: * if a user is not allowed to login. is this an
151: * issue? -markus
152: */
153: if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
154: packet_start(SSH2_MSG_USERAUTH_PK_OK);
155: packet_put_string(pkalg, alen);
156: packet_put_string(pkblob, blen);
157: packet_send();
158: packet_write_wait();
159: authctxt->postponed = 1;
160: }
161: }
162: if (authenticated != 1)
163: auth_clear_options();
164: done:
165: debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
166: if (key != NULL)
167: key_free(key);
168: xfree(pkalg);
169: xfree(pkblob);
170: return authenticated;
171: }
172:
173: /* return 1 if user allows given key */
174: static int
175: user_key_allowed2(struct passwd *pw, Key *key, char *file)
176: {
1.8 dtucker 177: char line[SSH_MAX_PUBKEY_BYTES];
1.1 markus 178: int found_key = 0;
179: FILE *f;
180: u_long linenum = 0;
181: struct stat st;
182: Key *found;
183: char *fp;
184:
185: /* Temporarily use the user's uid. */
186: temporarily_use_uid(pw);
187:
188: debug("trying public key file %s", file);
189:
190: /* Fail quietly if file does not exist */
191: if (stat(file, &st) < 0) {
192: /* Restore the privileged uid. */
193: restore_uid();
194: return 0;
195: }
196: /* Open the file containing the authorized keys. */
197: f = fopen(file, "r");
198: if (!f) {
199: /* Restore the privileged uid. */
200: restore_uid();
201: return 0;
202: }
203: if (options.strict_modes &&
204: secure_filename(f, file, pw, line, sizeof(line)) != 0) {
205: fclose(f);
1.3 itojun 206: logit("Authentication refused: %s", line);
1.1 markus 207: restore_uid();
208: return 0;
209: }
210:
211: found_key = 0;
212: found = key_new(key->type);
213:
1.8 dtucker 214: while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
1.7 avsm 215: char *cp, *key_options = NULL;
1.8 dtucker 216:
1.1 markus 217: /* Skip leading whitespace, empty and comment lines. */
218: for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
219: ;
220: if (!*cp || *cp == '\n' || *cp == '#')
221: continue;
222:
223: if (key_read(found, &cp) != 1) {
224: /* no key? check if there are options for this key */
225: int quoted = 0;
226: debug2("user_key_allowed: check options: '%s'", cp);
1.7 avsm 227: key_options = cp;
1.1 markus 228: for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
229: if (*cp == '\\' && cp[1] == '"')
230: cp++; /* Skip both */
231: else if (*cp == '"')
232: quoted = !quoted;
233: }
234: /* Skip remaining whitespace. */
235: for (; *cp == ' ' || *cp == '\t'; cp++)
236: ;
237: if (key_read(found, &cp) != 1) {
238: debug2("user_key_allowed: advance: '%s'", cp);
239: /* still no key? advance to next line*/
240: continue;
241: }
242: }
243: if (key_equal(found, key) &&
1.7 avsm 244: auth_parse_options(pw, key_options, file, linenum) == 1) {
1.1 markus 245: found_key = 1;
246: debug("matching key found: file %s, line %lu",
247: file, linenum);
248: fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
249: verbose("Found matching %s key: %s",
250: key_type(found), fp);
251: xfree(fp);
252: break;
253: }
254: }
255: restore_uid();
256: fclose(f);
257: key_free(found);
258: if (!found_key)
259: debug2("key not found");
260: return found_key;
261: }
262:
263: /* check whether given key is in .ssh/authorized_keys* */
264: int
265: user_key_allowed(struct passwd *pw, Key *key)
266: {
267: int success;
268: char *file;
269:
270: file = authorized_keys_file(pw);
271: success = user_key_allowed2(pw, key, file);
272: xfree(file);
273: if (success)
274: return success;
275:
276: /* try suffix "2" for backward compat, too */
277: file = authorized_keys_file2(pw);
278: success = user_key_allowed2(pw, key, file);
279: xfree(file);
280: return success;
281: }
1.2 markus 282:
283: Authmethod method_pubkey = {
284: "publickey",
285: userauth_pubkey,
286: &options.pubkey_authentication
287: };
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