Annotation of src/usr.bin/ssh/auth2-pubkey.c, Revision 1.19
1.19 ! otto 1: /* $OpenBSD: auth2-pubkey.c,v 1.18 2008/07/02 12:03:51 dtucker 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>
1.17 dtucker 34: #include <unistd.h>
1.1 markus 35:
1.15 deraadt 36: #include "xmalloc.h"
1.8 dtucker 37: #include "ssh.h"
1.1 markus 38: #include "ssh2.h"
39: #include "packet.h"
40: #include "buffer.h"
41: #include "log.h"
42: #include "servconf.h"
43: #include "compat.h"
1.15 deraadt 44: #include "key.h"
45: #include "hostfile.h"
1.1 markus 46: #include "auth.h"
47: #include "pathnames.h"
48: #include "uidswap.h"
49: #include "auth-options.h"
50: #include "canohost.h"
1.15 deraadt 51: #ifdef GSSAPI
52: #include "ssh-gss.h"
53: #endif
1.1 markus 54: #include "monitor_wrap.h"
1.9 dtucker 55: #include "misc.h"
1.1 markus 56:
57: /* import */
58: extern ServerOptions options;
59: extern u_char *session_id2;
1.4 markus 60: extern u_int session_id2_len;
1.1 markus 61:
1.2 markus 62: static int
1.1 markus 63: userauth_pubkey(Authctxt *authctxt)
64: {
65: Buffer b;
66: Key *key = NULL;
67: char *pkalg;
68: u_char *pkblob, *sig;
69: u_int alen, blen, slen;
70: int have_sig, pktype;
71: int authenticated = 0;
72:
73: if (!authctxt->valid) {
74: debug2("userauth_pubkey: disabled because of invalid user");
75: return 0;
76: }
77: have_sig = packet_get_char();
78: if (datafellows & SSH_BUG_PKAUTH) {
79: debug2("userauth_pubkey: SSH_BUG_PKAUTH");
80: /* no explicit pkalg given */
81: pkblob = packet_get_string(&blen);
82: buffer_init(&b);
83: buffer_append(&b, pkblob, blen);
84: /* so we have to extract the pkalg from the pkblob */
85: pkalg = buffer_get_string(&b, &alen);
86: buffer_free(&b);
87: } else {
88: pkalg = packet_get_string(&alen);
89: pkblob = packet_get_string(&blen);
90: }
91: pktype = key_type_from_name(pkalg);
92: if (pktype == KEY_UNSPEC) {
93: /* this is perfectly legal */
1.3 itojun 94: logit("userauth_pubkey: unsupported public key algorithm: %s",
1.1 markus 95: pkalg);
96: goto done;
97: }
98: key = key_from_blob(pkblob, blen);
99: if (key == NULL) {
100: error("userauth_pubkey: cannot decode key: %s", pkalg);
101: goto done;
102: }
103: if (key->type != pktype) {
104: error("userauth_pubkey: type mismatch for decoded key "
105: "(received %d, expected %d)", key->type, pktype);
106: goto done;
107: }
108: if (have_sig) {
109: sig = packet_get_string(&slen);
110: packet_check_eom();
111: buffer_init(&b);
112: if (datafellows & SSH_OLD_SESSIONID) {
113: buffer_append(&b, session_id2, session_id2_len);
114: } else {
115: buffer_put_string(&b, session_id2, session_id2_len);
116: }
117: /* reconstruct packet */
118: buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
119: buffer_put_cstring(&b, authctxt->user);
120: buffer_put_cstring(&b,
121: datafellows & SSH_BUG_PKSERVICE ?
122: "ssh-userauth" :
123: authctxt->service);
124: if (datafellows & SSH_BUG_PKAUTH) {
125: buffer_put_char(&b, have_sig);
126: } else {
127: buffer_put_cstring(&b, "publickey");
128: buffer_put_char(&b, have_sig);
129: buffer_put_cstring(&b, pkalg);
130: }
131: buffer_put_string(&b, pkblob, blen);
132: #ifdef DEBUG_PK
133: buffer_dump(&b);
134: #endif
135: /* test for correct signature */
136: authenticated = 0;
137: if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
138: PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
1.6 markus 139: buffer_len(&b))) == 1)
1.1 markus 140: authenticated = 1;
1.6 markus 141: buffer_free(&b);
1.1 markus 142: xfree(sig);
143: } else {
144: debug("test whether pkalg/pkblob are acceptable");
145: packet_check_eom();
146:
147: /* XXX fake reply and always send PK_OK ? */
148: /*
149: * XXX this allows testing whether a user is allowed
150: * to login: if you happen to have a valid pubkey this
151: * message is sent. the message is NEVER sent at all
152: * if a user is not allowed to login. is this an
153: * issue? -markus
154: */
155: if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
156: packet_start(SSH2_MSG_USERAUTH_PK_OK);
157: packet_put_string(pkalg, alen);
158: packet_put_string(pkblob, blen);
159: packet_send();
160: packet_write_wait();
161: authctxt->postponed = 1;
162: }
163: }
164: if (authenticated != 1)
165: auth_clear_options();
166: done:
167: debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
168: if (key != NULL)
169: key_free(key);
170: xfree(pkalg);
171: xfree(pkblob);
172: return authenticated;
173: }
174:
175: /* return 1 if user allows given key */
176: static int
177: user_key_allowed2(struct passwd *pw, Key *key, char *file)
178: {
1.8 dtucker 179: char line[SSH_MAX_PUBKEY_BYTES];
1.18 dtucker 180: int found_key = 0;
1.1 markus 181: FILE *f;
182: u_long linenum = 0;
183: Key *found;
184: char *fp;
185:
186: /* Temporarily use the user's uid. */
187: temporarily_use_uid(pw);
188:
189: debug("trying public key file %s", file);
1.18 dtucker 190: f = auth_openkeyfile(file, pw, options.strict_modes);
1.1 markus 191:
1.18 dtucker 192: if (!f) {
1.1 markus 193: restore_uid();
194: return 0;
195: }
196:
197: found_key = 0;
198: found = key_new(key->type);
199:
1.8 dtucker 200: while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
1.7 avsm 201: char *cp, *key_options = NULL;
1.8 dtucker 202:
1.1 markus 203: /* Skip leading whitespace, empty and comment lines. */
204: for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
205: ;
206: if (!*cp || *cp == '\n' || *cp == '#')
207: continue;
208:
209: if (key_read(found, &cp) != 1) {
210: /* no key? check if there are options for this key */
211: int quoted = 0;
212: debug2("user_key_allowed: check options: '%s'", cp);
1.7 avsm 213: key_options = cp;
1.1 markus 214: for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
215: if (*cp == '\\' && cp[1] == '"')
216: cp++; /* Skip both */
217: else if (*cp == '"')
218: quoted = !quoted;
219: }
220: /* Skip remaining whitespace. */
221: for (; *cp == ' ' || *cp == '\t'; cp++)
222: ;
223: if (key_read(found, &cp) != 1) {
224: debug2("user_key_allowed: advance: '%s'", cp);
225: /* still no key? advance to next line*/
226: continue;
227: }
228: }
229: if (key_equal(found, key) &&
1.7 avsm 230: auth_parse_options(pw, key_options, file, linenum) == 1) {
1.1 markus 231: found_key = 1;
232: debug("matching key found: file %s, line %lu",
233: file, linenum);
234: fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
235: verbose("Found matching %s key: %s",
236: key_type(found), fp);
237: xfree(fp);
238: break;
239: }
240: }
241: restore_uid();
242: fclose(f);
243: key_free(found);
244: if (!found_key)
245: debug2("key not found");
246: return found_key;
247: }
248:
249: /* check whether given key is in .ssh/authorized_keys* */
250: int
251: user_key_allowed(struct passwd *pw, Key *key)
252: {
253: int success;
254: char *file;
255:
256: file = authorized_keys_file(pw);
257: success = user_key_allowed2(pw, key, file);
258: xfree(file);
259: if (success)
260: return success;
261:
262: /* try suffix "2" for backward compat, too */
263: file = authorized_keys_file2(pw);
264: success = user_key_allowed2(pw, key, file);
265: xfree(file);
266: return success;
267: }
1.2 markus 268:
269: Authmethod method_pubkey = {
270: "publickey",
271: userauth_pubkey,
272: &options.pubkey_authentication
273: };
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