Annotation of src/usr.bin/ssh/auth2-hostbased.c, Revision 1.52
1.52 ! dtucker 1: /* $OpenBSD: auth2-hostbased.c,v 1.51 2023/02/17 04:22:50 dtucker 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"
1.29 markus 42: #include "sshkey.h"
1.11 deraadt 43: #include "hostfile.h"
1.1 markus 44: #include "auth.h"
45: #include "canohost.h"
1.11 deraadt 46: #ifdef GSSAPI
47: #include "ssh-gss.h"
48: #endif
1.1 markus 49: #include "monitor_wrap.h"
50: #include "pathnames.h"
1.29 markus 51: #include "ssherr.h"
1.22 djm 52: #include "match.h"
1.39 djm 53:
1.1 markus 54: /* import */
55: extern ServerOptions options;
56:
1.2 markus 57: static int
1.48 djm 58: userauth_hostbased(struct ssh *ssh, const char *method)
1.1 markus 59: {
1.30 markus 60: Authctxt *authctxt = ssh->authctxt;
1.29 markus 61: struct sshbuf *b;
1.27 markus 62: struct sshkey *key = NULL;
1.33 djm 63: char *pkalg, *cuser, *chost;
1.1 markus 64: u_char *pkblob, *sig;
1.29 markus 65: size_t alen, blen, slen;
66: int r, pktype, authenticated = 0;
1.1 markus 67:
1.29 markus 68: /* XXX use sshkey_froms() */
69: if ((r = sshpkt_get_cstring(ssh, &pkalg, &alen)) != 0 ||
70: (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0 ||
71: (r = sshpkt_get_cstring(ssh, &chost, NULL)) != 0 ||
72: (r = sshpkt_get_cstring(ssh, &cuser, NULL)) != 0 ||
73: (r = sshpkt_get_string(ssh, &sig, &slen)) != 0)
1.43 djm 74: fatal_fr(r, "parse packet");
1.1 markus 75:
1.43 djm 76: debug_f("cuser %s chost %s pkalg %s slen %zu",
1.1 markus 77: cuser, chost, pkalg, slen);
78: #ifdef DEBUG_PK
79: debug("signature:");
1.37 mestre 80: sshbuf_dump_data(sig, slen, stderr);
1.1 markus 81: #endif
1.29 markus 82: pktype = sshkey_type_from_name(pkalg);
1.1 markus 83: if (pktype == KEY_UNSPEC) {
84: /* this is perfectly legal */
1.43 djm 85: logit_f("unsupported public key algorithm: %s",
86: pkalg);
1.29 markus 87: goto done;
88: }
89: if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
1.43 djm 90: error_fr(r, "key_from_blob");
1.1 markus 91: goto done;
92: }
93: if (key == NULL) {
1.43 djm 94: error_f("cannot decode key: %s", pkalg);
1.1 markus 95: goto done;
96: }
97: if (key->type != pktype) {
1.43 djm 98: error_f("type mismatch for decoded key "
99: "(received %d, expected %d)", key->type, pktype);
1.1 markus 100: goto done;
101: }
1.45 dtucker 102: if (match_pattern_list(pkalg, options.hostbased_accepted_algos, 0) != 1) {
1.49 djm 103: logit_f("signature algorithm %s not in "
104: "HostbasedAcceptedAlgorithms", pkalg);
1.38 djm 105: goto done;
106: }
107: if ((r = sshkey_check_cert_sigtype(key,
108: options.ca_sign_algorithms)) != 0) {
1.43 djm 109: logit_fr(r, "certificate signature algorithm %s",
1.38 djm 110: (key->cert == NULL || key->cert->signature_type == NULL) ?
1.43 djm 111: "(null)" : key->cert->signature_type);
1.50 djm 112: goto done;
113: }
114: if ((r = sshkey_check_rsa_length(key,
115: options.required_rsa_size)) != 0) {
116: logit_r(r, "refusing %s key", sshkey_type(key));
1.36 djm 117: goto done;
118: }
119:
120: if (!authctxt->valid || authctxt->user == NULL) {
1.43 djm 121: debug2_f("disabled because of invalid user");
1.22 djm 122: goto done;
123: }
124:
1.29 markus 125: if ((b = sshbuf_new()) == NULL)
1.43 djm 126: fatal_f("sshbuf_new failed");
1.1 markus 127: /* reconstruct packet */
1.46 djm 128: if ((r = sshbuf_put_stringb(b, ssh->kex->session_id)) != 0 ||
1.29 markus 129: (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
130: (r = sshbuf_put_cstring(b, authctxt->user)) != 0 ||
1.33 djm 131: (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
1.48 djm 132: (r = sshbuf_put_cstring(b, method)) != 0 ||
1.29 markus 133: (r = sshbuf_put_string(b, pkalg, alen)) != 0 ||
134: (r = sshbuf_put_string(b, pkblob, blen)) != 0 ||
135: (r = sshbuf_put_cstring(b, chost)) != 0 ||
136: (r = sshbuf_put_cstring(b, cuser)) != 0)
1.43 djm 137: fatal_fr(r, "reconstruct packet");
1.1 markus 138: #ifdef DEBUG_PK
1.29 markus 139: sshbuf_dump(b, stderr);
1.1 markus 140: #endif
1.16 djm 141:
1.31 djm 142: auth2_record_info(authctxt,
1.16 djm 143: "client user \"%.100s\", client host \"%.100s\"", cuser, chost);
144:
1.1 markus 145: /* test for allowed key and correct signature */
146: authenticated = 0;
1.40 djm 147: if (PRIVSEP(hostbased_key_allowed(ssh, authctxt->pw, cuser,
148: chost, key)) &&
1.29 markus 149: PRIVSEP(sshkey_verify(key, sig, slen,
1.42 djm 150: sshbuf_ptr(b), sshbuf_len(b), pkalg, ssh->compat, NULL)) == 0)
1.1 markus 151: authenticated = 1;
152:
1.31 djm 153: auth2_record_key(authctxt, authenticated, key);
1.29 markus 154: sshbuf_free(b);
1.1 markus 155: done:
1.43 djm 156: debug2_f("authenticated %d", authenticated);
1.31 djm 157: sshkey_free(key);
1.15 djm 158: free(pkalg);
159: free(pkblob);
160: free(cuser);
161: free(chost);
162: free(sig);
1.1 markus 163: return authenticated;
164: }
165:
166: /* return 1 if given hostkey is allowed */
167: int
1.40 djm 168: hostbased_key_allowed(struct ssh *ssh, struct passwd *pw,
169: const char *cuser, char *chost, struct sshkey *key)
1.1 markus 170: {
1.14 djm 171: const char *resolvedname, *ipaddr, *lookup, *reason;
1.1 markus 172: HostStatus host_status;
173: int len;
1.14 djm 174: char *fp;
1.13 djm 175:
176: if (auth_key_is_revoked(key))
177: return 0;
1.1 markus 178:
1.26 djm 179: resolvedname = auth_get_canonical_hostname(ssh, options.use_dns);
180: ipaddr = ssh_remote_ipaddr(ssh);
1.1 markus 181:
1.43 djm 182: debug2_f("chost %s resolvedname %s ipaddr %s",
1.1 markus 183: chost, resolvedname, ipaddr);
184:
1.12 djm 185: if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
186: debug2("stripping trailing dot from chost %s", chost);
187: chost[len - 1] = '\0';
188: }
189:
1.1 markus 190: if (options.hostbased_uses_name_from_packet_only) {
1.20 djm 191: if (auth_rhosts2(pw, cuser, chost, chost) == 0) {
1.43 djm 192: debug2_f("auth_rhosts2 refused user \"%.100s\" "
193: "host \"%.100s\" (from packet)", cuser, chost);
1.1 markus 194: return 0;
1.20 djm 195: }
1.1 markus 196: lookup = chost;
197: } else {
198: if (strcasecmp(resolvedname, chost) != 0)
1.3 itojun 199: logit("userauth_hostbased mismatch: "
1.1 markus 200: "client sends %s, but we resolve %s to %s",
201: chost, ipaddr, resolvedname);
1.20 djm 202: if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0) {
1.43 djm 203: debug2_f("auth_rhosts2 refused "
1.20 djm 204: "user \"%.100s\" host \"%.100s\" addr \"%.100s\"",
1.43 djm 205: cuser, resolvedname, ipaddr);
1.1 markus 206: return 0;
1.20 djm 207: }
1.1 markus 208: lookup = resolvedname;
209: }
1.43 djm 210: debug2_f("access allowed by auth_rhosts2");
1.1 markus 211:
1.29 markus 212: if (sshkey_is_cert(key) &&
1.47 djm 213: sshkey_cert_check_authority_now(key, 1, 0, 0, lookup, &reason)) {
1.14 djm 214: error("%s", reason);
215: auth_debug_add("%s", reason);
216: return 0;
217: }
218:
1.1 markus 219: host_status = check_key_in_hostfiles(pw, key, lookup,
220: _PATH_SSH_SYSTEM_HOSTFILE,
221: options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
222:
223: /* backward compat if no key has been found. */
1.14 djm 224: if (host_status == HOST_NEW) {
1.1 markus 225: host_status = check_key_in_hostfiles(pw, key, lookup,
226: _PATH_SSH_SYSTEM_HOSTFILE2,
227: options.ignore_user_known_hosts ? NULL :
228: _PATH_SSH_USER_HOSTFILE2);
1.14 djm 229: }
230:
231: if (host_status == HOST_OK) {
1.29 markus 232: if (sshkey_is_cert(key)) {
1.24 djm 233: if ((fp = sshkey_fingerprint(key->cert->signature_key,
234: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
1.43 djm 235: fatal_f("sshkey_fingerprint fail");
1.14 djm 236: verbose("Accepted certificate ID \"%s\" signed by "
237: "%s CA %s from %s@%s", key->cert->key_id,
1.29 markus 238: sshkey_type(key->cert->signature_key), fp,
1.14 djm 239: cuser, lookup);
240: } else {
1.24 djm 241: if ((fp = sshkey_fingerprint(key,
242: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
1.43 djm 243: fatal_f("sshkey_fingerprint fail");
1.14 djm 244: verbose("Accepted %s public key %s from %s@%s",
1.29 markus 245: sshkey_type(key), fp, cuser, lookup);
1.14 djm 246: }
1.15 djm 247: free(fp);
1.14 djm 248: }
1.1 markus 249:
250: return (host_status == HOST_OK);
251: }
1.2 markus 252:
253: Authmethod method_hostbased = {
254: "hostbased",
1.48 djm 255: NULL,
1.2 markus 256: userauth_hostbased,
257: &options.hostbased_authentication
258: };
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