Annotation of src/usr.bin/ssh/auth2-hostbased.c, Revision 1.39
1.39 ! djm 1: /* $OpenBSD: auth2-hostbased.c,v 1.38 2018/09/20 03:28:06 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:
1.9 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"
1.35 markus 36: #include "sshbuf.h"
1.1 markus 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"
1.39 ! djm 52:
! 53: extern struct ssh *active_state; /* XXX */
1.1 markus 54:
55: /* import */
56: extern ServerOptions options;
57: extern u_char *session_id2;
1.5 markus 58: extern u_int session_id2_len;
1.1 markus 59:
1.2 markus 60: static int
1.30 markus 61: userauth_hostbased(struct ssh *ssh)
1.1 markus 62: {
1.30 markus 63: Authctxt *authctxt = ssh->authctxt;
1.29 markus 64: struct sshbuf *b;
1.27 markus 65: struct sshkey *key = NULL;
1.33 djm 66: char *pkalg, *cuser, *chost;
1.1 markus 67: u_char *pkblob, *sig;
1.29 markus 68: size_t alen, blen, slen;
69: int r, pktype, authenticated = 0;
1.1 markus 70:
1.29 markus 71: /* XXX use sshkey_froms() */
72: if ((r = sshpkt_get_cstring(ssh, &pkalg, &alen)) != 0 ||
73: (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0 ||
74: (r = sshpkt_get_cstring(ssh, &chost, NULL)) != 0 ||
75: (r = sshpkt_get_cstring(ssh, &cuser, NULL)) != 0 ||
76: (r = sshpkt_get_string(ssh, &sig, &slen)) != 0)
77: fatal("%s: packet parsing: %s", __func__, ssh_err(r));
1.1 markus 78:
1.29 markus 79: debug("%s: cuser %s chost %s pkalg %s slen %zu", __func__,
1.1 markus 80: cuser, chost, pkalg, slen);
81: #ifdef DEBUG_PK
82: debug("signature:");
1.37 mestre 83: sshbuf_dump_data(sig, slen, stderr);
1.1 markus 84: #endif
1.29 markus 85: pktype = sshkey_type_from_name(pkalg);
1.1 markus 86: if (pktype == KEY_UNSPEC) {
87: /* this is perfectly legal */
1.29 markus 88: logit("%s: unsupported public key algorithm: %s",
89: __func__, pkalg);
90: goto done;
91: }
92: if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
93: error("%s: key_from_blob: %s", __func__, ssh_err(r));
1.1 markus 94: goto done;
95: }
96: if (key == NULL) {
1.29 markus 97: error("%s: cannot decode key: %s", __func__, pkalg);
1.1 markus 98: goto done;
99: }
100: if (key->type != pktype) {
1.29 markus 101: error("%s: type mismatch for decoded key "
102: "(received %d, expected %d)", __func__, key->type, pktype);
1.17 djm 103: goto done;
104: }
1.29 markus 105: if (sshkey_type_plain(key->type) == KEY_RSA &&
106: (ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
1.17 djm 107: error("Refusing RSA key because peer uses unsafe "
108: "signature format");
1.1 markus 109: goto done;
110: }
1.34 djm 111: if (match_pattern_list(pkalg, options.hostbased_key_types, 0) != 1) {
1.22 djm 112: logit("%s: key type %s not in HostbasedAcceptedKeyTypes",
113: __func__, sshkey_type(key));
1.38 djm 114: goto done;
115: }
116: if ((r = sshkey_check_cert_sigtype(key,
117: options.ca_sign_algorithms)) != 0) {
118: logit("%s: certificate signature algorithm %s: %s", __func__,
119: (key->cert == NULL || key->cert->signature_type == NULL) ?
120: "(null)" : key->cert->signature_type, ssh_err(r));
1.36 djm 121: goto done;
122: }
123:
124: if (!authctxt->valid || authctxt->user == NULL) {
125: debug2("%s: disabled because of invalid user", __func__);
1.22 djm 126: goto done;
127: }
128:
1.29 markus 129: if ((b = sshbuf_new()) == NULL)
130: fatal("%s: sshbuf_new failed", __func__);
1.1 markus 131: /* reconstruct packet */
1.29 markus 132: if ((r = sshbuf_put_string(b, session_id2, session_id2_len)) != 0 ||
133: (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
134: (r = sshbuf_put_cstring(b, authctxt->user)) != 0 ||
1.33 djm 135: (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
1.29 markus 136: (r = sshbuf_put_cstring(b, "hostbased")) != 0 ||
137: (r = sshbuf_put_string(b, pkalg, alen)) != 0 ||
138: (r = sshbuf_put_string(b, pkblob, blen)) != 0 ||
139: (r = sshbuf_put_cstring(b, chost)) != 0 ||
140: (r = sshbuf_put_cstring(b, cuser)) != 0)
141: fatal("%s: buffer error: %s", __func__, ssh_err(r));
1.1 markus 142: #ifdef DEBUG_PK
1.29 markus 143: sshbuf_dump(b, stderr);
1.1 markus 144: #endif
1.16 djm 145:
1.31 djm 146: auth2_record_info(authctxt,
1.16 djm 147: "client user \"%.100s\", client host \"%.100s\"", cuser, chost);
148:
1.1 markus 149: /* test for allowed key and correct signature */
150: authenticated = 0;
151: if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) &&
1.29 markus 152: PRIVSEP(sshkey_verify(key, sig, slen,
1.32 djm 153: sshbuf_ptr(b), sshbuf_len(b), pkalg, ssh->compat)) == 0)
1.1 markus 154: authenticated = 1;
155:
1.31 djm 156: auth2_record_key(authctxt, authenticated, key);
1.29 markus 157: sshbuf_free(b);
1.1 markus 158: done:
1.29 markus 159: debug2("%s: authenticated %d", __func__, authenticated);
1.31 djm 160: sshkey_free(key);
1.15 djm 161: free(pkalg);
162: free(pkblob);
163: free(cuser);
164: free(chost);
165: free(sig);
1.1 markus 166: return authenticated;
167: }
168:
169: /* return 1 if given hostkey is allowed */
170: int
171: hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost,
1.27 markus 172: struct sshkey *key)
1.1 markus 173: {
1.26 djm 174: struct ssh *ssh = active_state; /* XXX */
1.14 djm 175: const char *resolvedname, *ipaddr, *lookup, *reason;
1.1 markus 176: HostStatus host_status;
177: int len;
1.14 djm 178: char *fp;
1.13 djm 179:
180: if (auth_key_is_revoked(key))
181: return 0;
1.1 markus 182:
1.26 djm 183: resolvedname = auth_get_canonical_hostname(ssh, options.use_dns);
184: ipaddr = ssh_remote_ipaddr(ssh);
1.1 markus 185:
1.20 djm 186: debug2("%s: chost %s resolvedname %s ipaddr %s", __func__,
1.1 markus 187: chost, resolvedname, ipaddr);
188:
1.12 djm 189: if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
190: debug2("stripping trailing dot from chost %s", chost);
191: chost[len - 1] = '\0';
192: }
193:
1.1 markus 194: if (options.hostbased_uses_name_from_packet_only) {
1.20 djm 195: if (auth_rhosts2(pw, cuser, chost, chost) == 0) {
196: debug2("%s: auth_rhosts2 refused "
197: "user \"%.100s\" host \"%.100s\" (from packet)",
198: __func__, cuser, chost);
1.1 markus 199: return 0;
1.20 djm 200: }
1.1 markus 201: lookup = chost;
202: } else {
203: if (strcasecmp(resolvedname, chost) != 0)
1.3 itojun 204: logit("userauth_hostbased mismatch: "
1.1 markus 205: "client sends %s, but we resolve %s to %s",
206: chost, ipaddr, resolvedname);
1.20 djm 207: if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0) {
208: debug2("%s: auth_rhosts2 refused "
209: "user \"%.100s\" host \"%.100s\" addr \"%.100s\"",
210: __func__, cuser, resolvedname, ipaddr);
1.1 markus 211: return 0;
1.20 djm 212: }
1.1 markus 213: lookup = resolvedname;
214: }
1.20 djm 215: debug2("%s: access allowed by auth_rhosts2", __func__);
1.1 markus 216:
1.29 markus 217: if (sshkey_is_cert(key) &&
218: sshkey_cert_check_authority(key, 1, 0, lookup, &reason)) {
1.14 djm 219: error("%s", reason);
220: auth_debug_add("%s", reason);
221: return 0;
222: }
223:
1.1 markus 224: host_status = check_key_in_hostfiles(pw, key, lookup,
225: _PATH_SSH_SYSTEM_HOSTFILE,
226: options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
227:
228: /* backward compat if no key has been found. */
1.14 djm 229: if (host_status == HOST_NEW) {
1.1 markus 230: host_status = check_key_in_hostfiles(pw, key, lookup,
231: _PATH_SSH_SYSTEM_HOSTFILE2,
232: options.ignore_user_known_hosts ? NULL :
233: _PATH_SSH_USER_HOSTFILE2);
1.14 djm 234: }
235:
236: if (host_status == HOST_OK) {
1.29 markus 237: if (sshkey_is_cert(key)) {
1.24 djm 238: if ((fp = sshkey_fingerprint(key->cert->signature_key,
239: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
240: fatal("%s: sshkey_fingerprint fail", __func__);
1.14 djm 241: verbose("Accepted certificate ID \"%s\" signed by "
242: "%s CA %s from %s@%s", key->cert->key_id,
1.29 markus 243: sshkey_type(key->cert->signature_key), fp,
1.14 djm 244: cuser, lookup);
245: } else {
1.24 djm 246: if ((fp = sshkey_fingerprint(key,
247: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
248: fatal("%s: sshkey_fingerprint fail", __func__);
1.14 djm 249: verbose("Accepted %s public key %s from %s@%s",
1.29 markus 250: sshkey_type(key), fp, cuser, lookup);
1.14 djm 251: }
1.15 djm 252: free(fp);
1.14 djm 253: }
1.1 markus 254:
255: return (host_status == HOST_OK);
256: }
1.2 markus 257:
258: Authmethod method_hostbased = {
259: "hostbased",
260: userauth_hostbased,
261: &options.hostbased_authentication
262: };