Annotation of src/usr.bin/ssh/auth2-hostbased.c, Revision 1.36
1.36 ! djm 1: /* $OpenBSD: auth2-hostbased.c,v 1.35 2018/07/09 21:35:50 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"
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"
1.1 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;
1.33 djm 64: char *pkalg, *cuser, *chost;
1.1 markus 65: u_char *pkblob, *sig;
1.29 markus 66: size_t alen, blen, slen;
67: int r, pktype, authenticated = 0;
1.1 markus 68:
1.29 markus 69: /* XXX use sshkey_froms() */
70: if ((r = sshpkt_get_cstring(ssh, &pkalg, &alen)) != 0 ||
71: (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0 ||
72: (r = sshpkt_get_cstring(ssh, &chost, NULL)) != 0 ||
73: (r = sshpkt_get_cstring(ssh, &cuser, NULL)) != 0 ||
74: (r = sshpkt_get_string(ssh, &sig, &slen)) != 0)
75: fatal("%s: packet parsing: %s", __func__, ssh_err(r));
1.1 markus 76:
1.29 markus 77: debug("%s: cuser %s chost %s pkalg %s slen %zu", __func__,
1.1 markus 78: cuser, chost, pkalg, slen);
79: #ifdef DEBUG_PK
80: debug("signature:");
1.29 markus 81: sshbuf_dump_data(sig, siglen, stderr);
1.1 markus 82: #endif
1.29 markus 83: pktype = sshkey_type_from_name(pkalg);
1.1 markus 84: if (pktype == KEY_UNSPEC) {
85: /* this is perfectly legal */
1.29 markus 86: logit("%s: unsupported public key algorithm: %s",
87: __func__, pkalg);
88: goto done;
89: }
90: if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
91: error("%s: key_from_blob: %s", __func__, ssh_err(r));
1.1 markus 92: goto done;
93: }
94: if (key == NULL) {
1.29 markus 95: error("%s: cannot decode key: %s", __func__, pkalg);
1.1 markus 96: goto done;
97: }
98: if (key->type != pktype) {
1.29 markus 99: error("%s: type mismatch for decoded key "
100: "(received %d, expected %d)", __func__, key->type, pktype);
1.17 djm 101: goto done;
102: }
1.29 markus 103: if (sshkey_type_plain(key->type) == KEY_RSA &&
104: (ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
1.17 djm 105: error("Refusing RSA key because peer uses unsafe "
106: "signature format");
1.1 markus 107: goto done;
108: }
1.34 djm 109: if (match_pattern_list(pkalg, options.hostbased_key_types, 0) != 1) {
1.22 djm 110: logit("%s: key type %s not in HostbasedAcceptedKeyTypes",
111: __func__, sshkey_type(key));
1.36 ! djm 112: goto done;
! 113: }
! 114:
! 115: if (!authctxt->valid || authctxt->user == NULL) {
! 116: debug2("%s: disabled because of invalid user", __func__);
1.22 djm 117: goto done;
118: }
119:
1.29 markus 120: if ((b = sshbuf_new()) == NULL)
121: fatal("%s: sshbuf_new failed", __func__);
1.1 markus 122: /* reconstruct packet */
1.29 markus 123: if ((r = sshbuf_put_string(b, session_id2, session_id2_len)) != 0 ||
124: (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
125: (r = sshbuf_put_cstring(b, authctxt->user)) != 0 ||
1.33 djm 126: (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
1.29 markus 127: (r = sshbuf_put_cstring(b, "hostbased")) != 0 ||
128: (r = sshbuf_put_string(b, pkalg, alen)) != 0 ||
129: (r = sshbuf_put_string(b, pkblob, blen)) != 0 ||
130: (r = sshbuf_put_cstring(b, chost)) != 0 ||
131: (r = sshbuf_put_cstring(b, cuser)) != 0)
132: fatal("%s: buffer error: %s", __func__, ssh_err(r));
1.1 markus 133: #ifdef DEBUG_PK
1.29 markus 134: sshbuf_dump(b, stderr);
1.1 markus 135: #endif
1.16 djm 136:
1.31 djm 137: auth2_record_info(authctxt,
1.16 djm 138: "client user \"%.100s\", client host \"%.100s\"", cuser, chost);
139:
1.1 markus 140: /* test for allowed key and correct signature */
141: authenticated = 0;
142: if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) &&
1.29 markus 143: PRIVSEP(sshkey_verify(key, sig, slen,
1.32 djm 144: sshbuf_ptr(b), sshbuf_len(b), pkalg, ssh->compat)) == 0)
1.1 markus 145: authenticated = 1;
146:
1.31 djm 147: auth2_record_key(authctxt, authenticated, key);
1.29 markus 148: sshbuf_free(b);
1.1 markus 149: done:
1.29 markus 150: debug2("%s: authenticated %d", __func__, authenticated);
1.31 djm 151: sshkey_free(key);
1.15 djm 152: free(pkalg);
153: free(pkblob);
154: free(cuser);
155: free(chost);
156: free(sig);
1.1 markus 157: return authenticated;
158: }
159:
160: /* return 1 if given hostkey is allowed */
161: int
162: hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost,
1.27 markus 163: struct sshkey *key)
1.1 markus 164: {
1.26 djm 165: struct ssh *ssh = active_state; /* XXX */
1.14 djm 166: const char *resolvedname, *ipaddr, *lookup, *reason;
1.1 markus 167: HostStatus host_status;
168: int len;
1.14 djm 169: char *fp;
1.13 djm 170:
171: if (auth_key_is_revoked(key))
172: return 0;
1.1 markus 173:
1.26 djm 174: resolvedname = auth_get_canonical_hostname(ssh, options.use_dns);
175: ipaddr = ssh_remote_ipaddr(ssh);
1.1 markus 176:
1.20 djm 177: debug2("%s: chost %s resolvedname %s ipaddr %s", __func__,
1.1 markus 178: chost, resolvedname, ipaddr);
179:
1.12 djm 180: if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
181: debug2("stripping trailing dot from chost %s", chost);
182: chost[len - 1] = '\0';
183: }
184:
1.1 markus 185: if (options.hostbased_uses_name_from_packet_only) {
1.20 djm 186: if (auth_rhosts2(pw, cuser, chost, chost) == 0) {
187: debug2("%s: auth_rhosts2 refused "
188: "user \"%.100s\" host \"%.100s\" (from packet)",
189: __func__, cuser, chost);
1.1 markus 190: return 0;
1.20 djm 191: }
1.1 markus 192: lookup = chost;
193: } else {
194: if (strcasecmp(resolvedname, chost) != 0)
1.3 itojun 195: logit("userauth_hostbased mismatch: "
1.1 markus 196: "client sends %s, but we resolve %s to %s",
197: chost, ipaddr, resolvedname);
1.20 djm 198: if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0) {
199: debug2("%s: auth_rhosts2 refused "
200: "user \"%.100s\" host \"%.100s\" addr \"%.100s\"",
201: __func__, cuser, resolvedname, ipaddr);
1.1 markus 202: return 0;
1.20 djm 203: }
1.1 markus 204: lookup = resolvedname;
205: }
1.20 djm 206: debug2("%s: access allowed by auth_rhosts2", __func__);
1.1 markus 207:
1.29 markus 208: if (sshkey_is_cert(key) &&
209: sshkey_cert_check_authority(key, 1, 0, lookup, &reason)) {
1.14 djm 210: error("%s", reason);
211: auth_debug_add("%s", reason);
212: return 0;
213: }
214:
1.1 markus 215: host_status = check_key_in_hostfiles(pw, key, lookup,
216: _PATH_SSH_SYSTEM_HOSTFILE,
217: options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
218:
219: /* backward compat if no key has been found. */
1.14 djm 220: if (host_status == HOST_NEW) {
1.1 markus 221: host_status = check_key_in_hostfiles(pw, key, lookup,
222: _PATH_SSH_SYSTEM_HOSTFILE2,
223: options.ignore_user_known_hosts ? NULL :
224: _PATH_SSH_USER_HOSTFILE2);
1.14 djm 225: }
226:
227: if (host_status == HOST_OK) {
1.29 markus 228: if (sshkey_is_cert(key)) {
1.24 djm 229: if ((fp = sshkey_fingerprint(key->cert->signature_key,
230: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
231: fatal("%s: sshkey_fingerprint fail", __func__);
1.14 djm 232: verbose("Accepted certificate ID \"%s\" signed by "
233: "%s CA %s from %s@%s", key->cert->key_id,
1.29 markus 234: sshkey_type(key->cert->signature_key), fp,
1.14 djm 235: cuser, lookup);
236: } else {
1.24 djm 237: if ((fp = sshkey_fingerprint(key,
238: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
239: fatal("%s: sshkey_fingerprint fail", __func__);
1.14 djm 240: verbose("Accepted %s public key %s from %s@%s",
1.29 markus 241: sshkey_type(key), fp, cuser, lookup);
1.14 djm 242: }
1.15 djm 243: free(fp);
1.14 djm 244: }
1.1 markus 245:
246: return (host_status == HOST_OK);
247: }
1.2 markus 248:
249: Authmethod method_hostbased = {
250: "hostbased",
251: userauth_hostbased,
252: &options.hostbased_authentication
253: };
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