Annotation of src/usr.bin/ssh/auth2-pubkey.c, Revision 1.2.6.1
1.1 markus 1: /*
2: * Copyright (c) 2000 Markus Friedl. All rights reserved.
3: *
4: * Redistribution and use in source and binary forms, with or without
5: * modification, are permitted provided that the following conditions
6: * are met:
7: * 1. Redistributions of source code must retain the above copyright
8: * notice, this list of conditions and the following disclaimer.
9: * 2. Redistributions in binary form must reproduce the above copyright
10: * notice, this list of conditions and the following disclaimer in the
11: * documentation and/or other materials provided with the distribution.
12: *
13: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23: */
24:
25: #include "includes.h"
1.2.6.1 ! brad 26: RCSID("$OpenBSD: auth2-pubkey.c,v 1.4 2003/06/24 08:23:46 markus Exp $");
1.1 markus 27:
28: #include "ssh2.h"
29: #include "xmalloc.h"
30: #include "packet.h"
31: #include "buffer.h"
32: #include "log.h"
33: #include "servconf.h"
34: #include "compat.h"
35: #include "bufaux.h"
36: #include "auth.h"
37: #include "key.h"
38: #include "pathnames.h"
39: #include "uidswap.h"
40: #include "auth-options.h"
41: #include "canohost.h"
42: #include "monitor_wrap.h"
43:
44: /* import */
45: extern ServerOptions options;
46: extern u_char *session_id2;
1.2.6.1 ! brad 47: extern u_int session_id2_len;
1.1 markus 48:
1.2 markus 49: static int
1.1 markus 50: userauth_pubkey(Authctxt *authctxt)
51: {
52: Buffer b;
53: Key *key = NULL;
54: char *pkalg;
55: u_char *pkblob, *sig;
56: u_int alen, blen, slen;
57: int have_sig, pktype;
58: int authenticated = 0;
59:
60: if (!authctxt->valid) {
61: debug2("userauth_pubkey: disabled because of invalid user");
62: return 0;
63: }
64: have_sig = packet_get_char();
65: if (datafellows & SSH_BUG_PKAUTH) {
66: debug2("userauth_pubkey: SSH_BUG_PKAUTH");
67: /* no explicit pkalg given */
68: pkblob = packet_get_string(&blen);
69: buffer_init(&b);
70: buffer_append(&b, pkblob, blen);
71: /* so we have to extract the pkalg from the pkblob */
72: pkalg = buffer_get_string(&b, &alen);
73: buffer_free(&b);
74: } else {
75: pkalg = packet_get_string(&alen);
76: pkblob = packet_get_string(&blen);
77: }
78: pktype = key_type_from_name(pkalg);
79: if (pktype == KEY_UNSPEC) {
80: /* this is perfectly legal */
1.2.6.1 ! brad 81: logit("userauth_pubkey: unsupported public key algorithm: %s",
1.1 markus 82: pkalg);
83: goto done;
84: }
85: key = key_from_blob(pkblob, blen);
86: if (key == NULL) {
87: error("userauth_pubkey: cannot decode key: %s", pkalg);
88: goto done;
89: }
90: if (key->type != pktype) {
91: error("userauth_pubkey: type mismatch for decoded key "
92: "(received %d, expected %d)", key->type, pktype);
93: goto done;
94: }
95: if (have_sig) {
96: sig = packet_get_string(&slen);
97: packet_check_eom();
98: buffer_init(&b);
99: if (datafellows & SSH_OLD_SESSIONID) {
100: buffer_append(&b, session_id2, session_id2_len);
101: } else {
102: buffer_put_string(&b, session_id2, session_id2_len);
103: }
104: /* reconstruct packet */
105: buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
106: buffer_put_cstring(&b, authctxt->user);
107: buffer_put_cstring(&b,
108: datafellows & SSH_BUG_PKSERVICE ?
109: "ssh-userauth" :
110: authctxt->service);
111: if (datafellows & SSH_BUG_PKAUTH) {
112: buffer_put_char(&b, have_sig);
113: } else {
114: buffer_put_cstring(&b, "publickey");
115: buffer_put_char(&b, have_sig);
116: buffer_put_cstring(&b, pkalg);
117: }
118: buffer_put_string(&b, pkblob, blen);
119: #ifdef DEBUG_PK
120: buffer_dump(&b);
121: #endif
122: /* test for correct signature */
123: authenticated = 0;
124: if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
125: PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
126: buffer_len(&b))) == 1)
127: authenticated = 1;
128: buffer_clear(&b);
129: xfree(sig);
130: } else {
131: debug("test whether pkalg/pkblob are acceptable");
132: packet_check_eom();
133:
134: /* XXX fake reply and always send PK_OK ? */
135: /*
136: * XXX this allows testing whether a user is allowed
137: * to login: if you happen to have a valid pubkey this
138: * message is sent. the message is NEVER sent at all
139: * if a user is not allowed to login. is this an
140: * issue? -markus
141: */
142: if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
143: packet_start(SSH2_MSG_USERAUTH_PK_OK);
144: packet_put_string(pkalg, alen);
145: packet_put_string(pkblob, blen);
146: packet_send();
147: packet_write_wait();
148: authctxt->postponed = 1;
149: }
150: }
151: if (authenticated != 1)
152: auth_clear_options();
153: done:
154: debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
155: if (key != NULL)
156: key_free(key);
157: xfree(pkalg);
158: xfree(pkblob);
159: return authenticated;
160: }
161:
162: /* return 1 if user allows given key */
163: static int
164: user_key_allowed2(struct passwd *pw, Key *key, char *file)
165: {
166: char line[8192];
167: int found_key = 0;
168: FILE *f;
169: u_long linenum = 0;
170: struct stat st;
171: Key *found;
172: char *fp;
173:
174: if (pw == NULL)
175: return 0;
176:
177: /* Temporarily use the user's uid. */
178: temporarily_use_uid(pw);
179:
180: debug("trying public key file %s", file);
181:
182: /* Fail quietly if file does not exist */
183: if (stat(file, &st) < 0) {
184: /* Restore the privileged uid. */
185: restore_uid();
186: return 0;
187: }
188: /* Open the file containing the authorized keys. */
189: f = fopen(file, "r");
190: if (!f) {
191: /* Restore the privileged uid. */
192: restore_uid();
193: return 0;
194: }
195: if (options.strict_modes &&
196: secure_filename(f, file, pw, line, sizeof(line)) != 0) {
197: fclose(f);
1.2.6.1 ! brad 198: logit("Authentication refused: %s", line);
1.1 markus 199: restore_uid();
200: return 0;
201: }
202:
203: found_key = 0;
204: found = key_new(key->type);
205:
206: while (fgets(line, sizeof(line), f)) {
207: char *cp, *options = NULL;
208: linenum++;
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);
219: options = cp;
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: }
235: if (key_equal(found, key) &&
236: auth_parse_options(pw, options, file, linenum) == 1) {
237: found_key = 1;
238: debug("matching key found: file %s, line %lu",
239: file, linenum);
240: fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
241: verbose("Found matching %s key: %s",
242: key_type(found), fp);
243: xfree(fp);
244: break;
245: }
246: }
247: restore_uid();
248: fclose(f);
249: key_free(found);
250: if (!found_key)
251: debug2("key not found");
252: return found_key;
253: }
254:
255: /* check whether given key is in .ssh/authorized_keys* */
256: int
257: user_key_allowed(struct passwd *pw, Key *key)
258: {
259: int success;
260: char *file;
261:
262: file = authorized_keys_file(pw);
263: success = user_key_allowed2(pw, key, file);
264: xfree(file);
265: if (success)
266: return success;
267:
268: /* try suffix "2" for backward compat, too */
269: file = authorized_keys_file2(pw);
270: success = user_key_allowed2(pw, key, file);
271: xfree(file);
272: return success;
273: }
1.2 markus 274:
275: Authmethod method_pubkey = {
276: "publickey",
277: userauth_pubkey,
278: &options.pubkey_authentication
279: };
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