Annotation of src/usr.bin/ssh/auth2-hostbased.c, Revision 1.30
1.30 ! markus 1: /* $OpenBSD: auth2-hostbased.c,v 1.29 2017/05/30 14:25:42 markus 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:
1.9 stevesk 26:
27: #include <sys/types.h>
28:
29: #include <pwd.h>
1.10 stevesk 30: #include <string.h>
1.11 deraadt 31: #include <stdarg.h>
1.1 markus 32:
1.11 deraadt 33: #include "xmalloc.h"
1.1 markus 34: #include "ssh2.h"
35: #include "packet.h"
36: #include "buffer.h"
37: #include "log.h"
1.18 millert 38: #include "misc.h"
1.1 markus 39: #include "servconf.h"
40: #include "compat.h"
1.29 markus 41: #include "sshkey.h"
1.11 deraadt 42: #include "hostfile.h"
1.1 markus 43: #include "auth.h"
44: #include "canohost.h"
1.11 deraadt 45: #ifdef GSSAPI
46: #include "ssh-gss.h"
47: #endif
1.1 markus 48: #include "monitor_wrap.h"
49: #include "pathnames.h"
1.29 markus 50: #include "ssherr.h"
1.22 djm 51: #include "match.h"
1.1 markus 52:
53: /* import */
54: extern ServerOptions options;
55: extern u_char *session_id2;
1.5 markus 56: extern u_int session_id2_len;
1.1 markus 57:
1.2 markus 58: static int
1.30 ! markus 59: userauth_hostbased(struct ssh *ssh)
1.1 markus 60: {
1.30 ! markus 61: Authctxt *authctxt = ssh->authctxt;
1.29 markus 62: struct sshbuf *b;
1.27 markus 63: struct sshkey *key = NULL;
1.1 markus 64: char *pkalg, *cuser, *chost, *service;
65: u_char *pkblob, *sig;
1.29 markus 66: size_t alen, blen, slen;
67: int r, pktype, authenticated = 0;
1.1 markus 68:
69: if (!authctxt->valid) {
1.29 markus 70: debug2("%s: disabled because of invalid user", __func__);
1.1 markus 71: return 0;
72: }
1.29 markus 73: /* XXX use sshkey_froms() */
74: if ((r = sshpkt_get_cstring(ssh, &pkalg, &alen)) != 0 ||
75: (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0 ||
76: (r = sshpkt_get_cstring(ssh, &chost, NULL)) != 0 ||
77: (r = sshpkt_get_cstring(ssh, &cuser, NULL)) != 0 ||
78: (r = sshpkt_get_string(ssh, &sig, &slen)) != 0)
79: fatal("%s: packet parsing: %s", __func__, ssh_err(r));
1.1 markus 80:
1.29 markus 81: debug("%s: cuser %s chost %s pkalg %s slen %zu", __func__,
1.1 markus 82: cuser, chost, pkalg, slen);
83: #ifdef DEBUG_PK
84: debug("signature:");
1.29 markus 85: sshbuf_dump_data(sig, siglen, stderr);
1.1 markus 86: #endif
1.29 markus 87: pktype = sshkey_type_from_name(pkalg);
1.1 markus 88: if (pktype == KEY_UNSPEC) {
89: /* this is perfectly legal */
1.29 markus 90: logit("%s: unsupported public key algorithm: %s",
91: __func__, pkalg);
92: goto done;
93: }
94: if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
95: error("%s: key_from_blob: %s", __func__, ssh_err(r));
1.1 markus 96: goto done;
97: }
98: if (key == NULL) {
1.29 markus 99: error("%s: cannot decode key: %s", __func__, pkalg);
1.1 markus 100: goto done;
101: }
102: if (key->type != pktype) {
1.29 markus 103: error("%s: type mismatch for decoded key "
104: "(received %d, expected %d)", __func__, key->type, pktype);
1.17 djm 105: goto done;
106: }
1.29 markus 107: if (sshkey_type_plain(key->type) == KEY_RSA &&
108: (ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
1.17 djm 109: error("Refusing RSA key because peer uses unsafe "
110: "signature format");
1.1 markus 111: goto done;
112: }
1.22 djm 113: if (match_pattern_list(sshkey_ssh_name(key),
1.25 djm 114: options.hostbased_key_types, 0) != 1) {
1.22 djm 115: logit("%s: key type %s not in HostbasedAcceptedKeyTypes",
116: __func__, sshkey_type(key));
117: goto done;
118: }
119:
1.29 markus 120: service = ssh->compat & SSH_BUG_HBSERVICE ? "ssh-userauth" :
1.1 markus 121: authctxt->service;
1.29 markus 122: if ((b = sshbuf_new()) == NULL)
123: fatal("%s: sshbuf_new failed", __func__);
1.1 markus 124: /* reconstruct packet */
1.29 markus 125: if ((r = sshbuf_put_string(b, session_id2, session_id2_len)) != 0 ||
126: (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
127: (r = sshbuf_put_cstring(b, authctxt->user)) != 0 ||
128: (r = sshbuf_put_cstring(b, service)) != 0 ||
129: (r = sshbuf_put_cstring(b, "hostbased")) != 0 ||
130: (r = sshbuf_put_string(b, pkalg, alen)) != 0 ||
131: (r = sshbuf_put_string(b, pkblob, blen)) != 0 ||
132: (r = sshbuf_put_cstring(b, chost)) != 0 ||
133: (r = sshbuf_put_cstring(b, cuser)) != 0)
134: fatal("%s: buffer error: %s", __func__, ssh_err(r));
1.1 markus 135: #ifdef DEBUG_PK
1.29 markus 136: sshbuf_dump(b, stderr);
1.1 markus 137: #endif
1.16 djm 138:
139: pubkey_auth_info(authctxt, key,
140: "client user \"%.100s\", client host \"%.100s\"", cuser, chost);
141:
1.1 markus 142: /* test for allowed key and correct signature */
143: authenticated = 0;
144: if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) &&
1.29 markus 145: PRIVSEP(sshkey_verify(key, sig, slen,
146: sshbuf_ptr(b), sshbuf_len(b), ssh->compat)) == 0)
1.1 markus 147: authenticated = 1;
148:
1.29 markus 149: sshbuf_free(b);
1.1 markus 150: done:
1.29 markus 151: debug2("%s: authenticated %d", __func__, authenticated);
1.1 markus 152: if (key != NULL)
1.29 markus 153: sshkey_free(key);
1.15 djm 154: free(pkalg);
155: free(pkblob);
156: free(cuser);
157: free(chost);
158: free(sig);
1.1 markus 159: return authenticated;
160: }
161:
162: /* return 1 if given hostkey is allowed */
163: int
164: hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost,
1.27 markus 165: struct sshkey *key)
1.1 markus 166: {
1.26 djm 167: struct ssh *ssh = active_state; /* XXX */
1.14 djm 168: const char *resolvedname, *ipaddr, *lookup, *reason;
1.1 markus 169: HostStatus host_status;
170: int len;
1.14 djm 171: char *fp;
1.13 djm 172:
173: if (auth_key_is_revoked(key))
174: return 0;
1.1 markus 175:
1.26 djm 176: resolvedname = auth_get_canonical_hostname(ssh, options.use_dns);
177: ipaddr = ssh_remote_ipaddr(ssh);
1.1 markus 178:
1.20 djm 179: debug2("%s: chost %s resolvedname %s ipaddr %s", __func__,
1.1 markus 180: chost, resolvedname, ipaddr);
181:
1.12 djm 182: if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
183: debug2("stripping trailing dot from chost %s", chost);
184: chost[len - 1] = '\0';
185: }
186:
1.1 markus 187: if (options.hostbased_uses_name_from_packet_only) {
1.20 djm 188: if (auth_rhosts2(pw, cuser, chost, chost) == 0) {
189: debug2("%s: auth_rhosts2 refused "
190: "user \"%.100s\" host \"%.100s\" (from packet)",
191: __func__, cuser, chost);
1.1 markus 192: return 0;
1.20 djm 193: }
1.1 markus 194: lookup = chost;
195: } else {
196: if (strcasecmp(resolvedname, chost) != 0)
1.3 itojun 197: logit("userauth_hostbased mismatch: "
1.1 markus 198: "client sends %s, but we resolve %s to %s",
199: chost, ipaddr, resolvedname);
1.20 djm 200: if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0) {
201: debug2("%s: auth_rhosts2 refused "
202: "user \"%.100s\" host \"%.100s\" addr \"%.100s\"",
203: __func__, cuser, resolvedname, ipaddr);
1.1 markus 204: return 0;
1.20 djm 205: }
1.1 markus 206: lookup = resolvedname;
207: }
1.20 djm 208: debug2("%s: access allowed by auth_rhosts2", __func__);
1.1 markus 209:
1.29 markus 210: if (sshkey_is_cert(key) &&
211: sshkey_cert_check_authority(key, 1, 0, lookup, &reason)) {
1.14 djm 212: error("%s", reason);
213: auth_debug_add("%s", reason);
214: return 0;
215: }
216:
1.1 markus 217: host_status = check_key_in_hostfiles(pw, key, lookup,
218: _PATH_SSH_SYSTEM_HOSTFILE,
219: options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
220:
221: /* backward compat if no key has been found. */
1.14 djm 222: if (host_status == HOST_NEW) {
1.1 markus 223: host_status = check_key_in_hostfiles(pw, key, lookup,
224: _PATH_SSH_SYSTEM_HOSTFILE2,
225: options.ignore_user_known_hosts ? NULL :
226: _PATH_SSH_USER_HOSTFILE2);
1.14 djm 227: }
228:
229: if (host_status == HOST_OK) {
1.29 markus 230: if (sshkey_is_cert(key)) {
1.24 djm 231: if ((fp = sshkey_fingerprint(key->cert->signature_key,
232: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
233: fatal("%s: sshkey_fingerprint fail", __func__);
1.14 djm 234: verbose("Accepted certificate ID \"%s\" signed by "
235: "%s CA %s from %s@%s", key->cert->key_id,
1.29 markus 236: sshkey_type(key->cert->signature_key), fp,
1.14 djm 237: cuser, lookup);
238: } else {
1.24 djm 239: if ((fp = sshkey_fingerprint(key,
240: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
241: fatal("%s: sshkey_fingerprint fail", __func__);
1.14 djm 242: verbose("Accepted %s public key %s from %s@%s",
1.29 markus 243: sshkey_type(key), fp, cuser, lookup);
1.14 djm 244: }
1.15 djm 245: free(fp);
1.14 djm 246: }
1.1 markus 247:
248: return (host_status == HOST_OK);
249: }
1.2 markus 250:
251: Authmethod method_hostbased = {
252: "hostbased",
253: userauth_hostbased,
254: &options.hostbased_authentication
255: };
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