Annotation of src/usr.bin/ssh/auth2-hostbased.c, Revision 1.49
1.49 ! djm 1: /* $OpenBSD: auth2-hostbased.c,v 1.48 2021/12/19 22:12:07 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:
1.41 djm 29: #include <stdlib.h>
1.9 stevesk 30: #include <pwd.h>
1.10 stevesk 31: #include <string.h>
1.11 deraadt 32: #include <stdarg.h>
1.1 markus 33:
1.11 deraadt 34: #include "xmalloc.h"
1.1 markus 35: #include "ssh2.h"
36: #include "packet.h"
1.46 djm 37: #include "kex.h"
1.35 markus 38: #include "sshbuf.h"
1.1 markus 39: #include "log.h"
1.18 millert 40: #include "misc.h"
1.1 markus 41: #include "servconf.h"
42: #include "compat.h"
1.29 markus 43: #include "sshkey.h"
1.11 deraadt 44: #include "hostfile.h"
1.1 markus 45: #include "auth.h"
46: #include "canohost.h"
1.11 deraadt 47: #ifdef GSSAPI
48: #include "ssh-gss.h"
49: #endif
1.1 markus 50: #include "monitor_wrap.h"
51: #include "pathnames.h"
1.29 markus 52: #include "ssherr.h"
1.22 djm 53: #include "match.h"
1.39 djm 54:
1.1 markus 55: /* import */
56: extern ServerOptions options;
57:
1.2 markus 58: static int
1.48 djm 59: userauth_hostbased(struct ssh *ssh, const char *method)
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)
1.43 djm 75: fatal_fr(r, "parse packet");
1.1 markus 76:
1.43 djm 77: debug_f("cuser %s chost %s pkalg %s slen %zu",
1.1 markus 78: cuser, chost, pkalg, slen);
79: #ifdef DEBUG_PK
80: debug("signature:");
1.37 mestre 81: sshbuf_dump_data(sig, slen, 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 */
1.43 djm 86: logit_f("unsupported public key algorithm: %s",
87: pkalg);
1.29 markus 88: goto done;
89: }
90: if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
1.43 djm 91: error_fr(r, "key_from_blob");
1.1 markus 92: goto done;
93: }
94: if (key == NULL) {
1.43 djm 95: error_f("cannot decode key: %s", pkalg);
1.1 markus 96: goto done;
97: }
98: if (key->type != pktype) {
1.43 djm 99: error_f("type mismatch for decoded key "
100: "(received %d, expected %d)", 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: }
1.45 dtucker 109: if (match_pattern_list(pkalg, options.hostbased_accepted_algos, 0) != 1) {
1.49 ! djm 110: logit_f("signature algorithm %s not in "
! 111: "HostbasedAcceptedAlgorithms", pkalg);
1.38 djm 112: goto done;
113: }
114: if ((r = sshkey_check_cert_sigtype(key,
115: options.ca_sign_algorithms)) != 0) {
1.43 djm 116: logit_fr(r, "certificate signature algorithm %s",
1.38 djm 117: (key->cert == NULL || key->cert->signature_type == NULL) ?
1.43 djm 118: "(null)" : key->cert->signature_type);
1.36 djm 119: goto done;
120: }
121:
122: if (!authctxt->valid || authctxt->user == NULL) {
1.43 djm 123: debug2_f("disabled because of invalid user");
1.22 djm 124: goto done;
125: }
126:
1.29 markus 127: if ((b = sshbuf_new()) == NULL)
1.43 djm 128: fatal_f("sshbuf_new failed");
1.1 markus 129: /* reconstruct packet */
1.46 djm 130: if ((r = sshbuf_put_stringb(b, ssh->kex->session_id)) != 0 ||
1.29 markus 131: (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
132: (r = sshbuf_put_cstring(b, authctxt->user)) != 0 ||
1.33 djm 133: (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
1.48 djm 134: (r = sshbuf_put_cstring(b, method)) != 0 ||
1.29 markus 135: (r = sshbuf_put_string(b, pkalg, alen)) != 0 ||
136: (r = sshbuf_put_string(b, pkblob, blen)) != 0 ||
137: (r = sshbuf_put_cstring(b, chost)) != 0 ||
138: (r = sshbuf_put_cstring(b, cuser)) != 0)
1.43 djm 139: fatal_fr(r, "reconstruct packet");
1.1 markus 140: #ifdef DEBUG_PK
1.29 markus 141: sshbuf_dump(b, stderr);
1.1 markus 142: #endif
1.16 djm 143:
1.31 djm 144: auth2_record_info(authctxt,
1.16 djm 145: "client user \"%.100s\", client host \"%.100s\"", cuser, chost);
146:
1.1 markus 147: /* test for allowed key and correct signature */
148: authenticated = 0;
1.40 djm 149: if (PRIVSEP(hostbased_key_allowed(ssh, authctxt->pw, cuser,
150: chost, key)) &&
1.29 markus 151: PRIVSEP(sshkey_verify(key, sig, slen,
1.42 djm 152: sshbuf_ptr(b), sshbuf_len(b), pkalg, ssh->compat, NULL)) == 0)
1.1 markus 153: authenticated = 1;
154:
1.31 djm 155: auth2_record_key(authctxt, authenticated, key);
1.29 markus 156: sshbuf_free(b);
1.1 markus 157: done:
1.43 djm 158: debug2_f("authenticated %d", authenticated);
1.31 djm 159: sshkey_free(key);
1.15 djm 160: free(pkalg);
161: free(pkblob);
162: free(cuser);
163: free(chost);
164: free(sig);
1.1 markus 165: return authenticated;
166: }
167:
168: /* return 1 if given hostkey is allowed */
169: int
1.40 djm 170: hostbased_key_allowed(struct ssh *ssh, struct passwd *pw,
171: const char *cuser, char *chost, struct sshkey *key)
1.1 markus 172: {
1.14 djm 173: const char *resolvedname, *ipaddr, *lookup, *reason;
1.1 markus 174: HostStatus host_status;
175: int len;
1.14 djm 176: char *fp;
1.13 djm 177:
178: if (auth_key_is_revoked(key))
179: return 0;
1.1 markus 180:
1.26 djm 181: resolvedname = auth_get_canonical_hostname(ssh, options.use_dns);
182: ipaddr = ssh_remote_ipaddr(ssh);
1.1 markus 183:
1.43 djm 184: debug2_f("chost %s resolvedname %s ipaddr %s",
1.1 markus 185: chost, resolvedname, ipaddr);
186:
1.12 djm 187: if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
188: debug2("stripping trailing dot from chost %s", chost);
189: chost[len - 1] = '\0';
190: }
191:
1.1 markus 192: if (options.hostbased_uses_name_from_packet_only) {
1.20 djm 193: if (auth_rhosts2(pw, cuser, chost, chost) == 0) {
1.43 djm 194: debug2_f("auth_rhosts2 refused user \"%.100s\" "
195: "host \"%.100s\" (from packet)", cuser, chost);
1.1 markus 196: return 0;
1.20 djm 197: }
1.1 markus 198: lookup = chost;
199: } else {
200: if (strcasecmp(resolvedname, chost) != 0)
1.3 itojun 201: logit("userauth_hostbased mismatch: "
1.1 markus 202: "client sends %s, but we resolve %s to %s",
203: chost, ipaddr, resolvedname);
1.20 djm 204: if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0) {
1.43 djm 205: debug2_f("auth_rhosts2 refused "
1.20 djm 206: "user \"%.100s\" host \"%.100s\" addr \"%.100s\"",
1.43 djm 207: cuser, resolvedname, ipaddr);
1.1 markus 208: return 0;
1.20 djm 209: }
1.1 markus 210: lookup = resolvedname;
211: }
1.43 djm 212: debug2_f("access allowed by auth_rhosts2");
1.1 markus 213:
1.29 markus 214: if (sshkey_is_cert(key) &&
1.47 djm 215: sshkey_cert_check_authority_now(key, 1, 0, 0, lookup, &reason)) {
1.14 djm 216: error("%s", reason);
217: auth_debug_add("%s", reason);
218: return 0;
219: }
220:
1.1 markus 221: host_status = check_key_in_hostfiles(pw, key, lookup,
222: _PATH_SSH_SYSTEM_HOSTFILE,
223: options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
224:
225: /* backward compat if no key has been found. */
1.14 djm 226: if (host_status == HOST_NEW) {
1.1 markus 227: host_status = check_key_in_hostfiles(pw, key, lookup,
228: _PATH_SSH_SYSTEM_HOSTFILE2,
229: options.ignore_user_known_hosts ? NULL :
230: _PATH_SSH_USER_HOSTFILE2);
1.14 djm 231: }
232:
233: if (host_status == HOST_OK) {
1.29 markus 234: if (sshkey_is_cert(key)) {
1.24 djm 235: if ((fp = sshkey_fingerprint(key->cert->signature_key,
236: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
1.43 djm 237: fatal_f("sshkey_fingerprint fail");
1.14 djm 238: verbose("Accepted certificate ID \"%s\" signed by "
239: "%s CA %s from %s@%s", key->cert->key_id,
1.29 markus 240: sshkey_type(key->cert->signature_key), fp,
1.14 djm 241: cuser, lookup);
242: } else {
1.24 djm 243: if ((fp = sshkey_fingerprint(key,
244: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
1.43 djm 245: fatal_f("sshkey_fingerprint fail");
1.14 djm 246: verbose("Accepted %s public key %s from %s@%s",
1.29 markus 247: sshkey_type(key), fp, cuser, lookup);
1.14 djm 248: }
1.15 djm 249: free(fp);
1.14 djm 250: }
1.1 markus 251:
252: return (host_status == HOST_OK);
253: }
1.2 markus 254:
255: Authmethod method_hostbased = {
256: "hostbased",
1.48 djm 257: NULL,
1.2 markus 258: userauth_hostbased,
259: &options.hostbased_authentication
260: };
![[BACK]](/icons/back.gif){kind=icon}
Return to auth2-hostbased.c CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh