/* $OpenBSD: auth2-hostbased.c,v 1.16 2013/06/21 00:34:49 djm Exp $ */ /* * Copyright (c) 2000 Markus Friedl. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include #include #include #include #include "xmalloc.h" #include "ssh2.h" #include "packet.h" #include "buffer.h" #include "log.h" #include "servconf.h" #include "compat.h" #include "key.h" #include "hostfile.h" #include "auth.h" #include "canohost.h" #ifdef GSSAPI #include "ssh-gss.h" #endif #include "monitor_wrap.h" #include "pathnames.h" /* import */ extern ServerOptions options; extern u_char *session_id2; extern u_int session_id2_len; static int userauth_hostbased(Authctxt *authctxt) { Buffer b; Key *key = NULL; char *pkalg, *cuser, *chost, *service; u_char *pkblob, *sig; u_int alen, blen, slen; int pktype; int authenticated = 0; if (!authctxt->valid) { debug2("userauth_hostbased: disabled because of invalid user"); return 0; } pkalg = packet_get_string(&alen); pkblob = packet_get_string(&blen); chost = packet_get_string(NULL); cuser = packet_get_string(NULL); sig = packet_get_string(&slen); debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d", cuser, chost, pkalg, slen); #ifdef DEBUG_PK debug("signature:"); buffer_init(&b); buffer_append(&b, sig, slen); buffer_dump(&b); buffer_free(&b); #endif pktype = key_type_from_name(pkalg); if (pktype == KEY_UNSPEC) { /* this is perfectly legal */ logit("userauth_hostbased: unsupported " "public key algorithm: %s", pkalg); goto done; } key = key_from_blob(pkblob, blen); if (key == NULL) { error("userauth_hostbased: cannot decode key: %s", pkalg); goto done; } if (key->type != pktype) { error("userauth_hostbased: type mismatch for decoded key " "(received %d, expected %d)", key->type, pktype); goto done; } service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" : authctxt->service; buffer_init(&b); buffer_put_string(&b, session_id2, session_id2_len); /* reconstruct packet */ buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST); buffer_put_cstring(&b, authctxt->user); buffer_put_cstring(&b, service); buffer_put_cstring(&b, "hostbased"); buffer_put_string(&b, pkalg, alen); buffer_put_string(&b, pkblob, blen); buffer_put_cstring(&b, chost); buffer_put_cstring(&b, cuser); #ifdef DEBUG_PK buffer_dump(&b); #endif pubkey_auth_info(authctxt, key, "client user \"%.100s\", client host \"%.100s\"", cuser, chost); /* test for allowed key and correct signature */ authenticated = 0; if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) && PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b), buffer_len(&b))) == 1) authenticated = 1; buffer_free(&b); done: debug2("userauth_hostbased: authenticated %d", authenticated); if (key != NULL) key_free(key); free(pkalg); free(pkblob); free(cuser); free(chost); free(sig); return authenticated; } /* return 1 if given hostkey is allowed */ int hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost, Key *key) { const char *resolvedname, *ipaddr, *lookup, *reason; HostStatus host_status; int len; char *fp; if (auth_key_is_revoked(key)) return 0; resolvedname = get_canonical_hostname(options.use_dns); ipaddr = get_remote_ipaddr(); debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s", chost, resolvedname, ipaddr); if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') { debug2("stripping trailing dot from chost %s", chost); chost[len - 1] = '\0'; } if (options.hostbased_uses_name_from_packet_only) { if (auth_rhosts2(pw, cuser, chost, chost) == 0) return 0; lookup = chost; } else { if (strcasecmp(resolvedname, chost) != 0) logit("userauth_hostbased mismatch: " "client sends %s, but we resolve %s to %s", chost, ipaddr, resolvedname); if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0) return 0; lookup = resolvedname; } debug2("userauth_hostbased: access allowed by auth_rhosts2"); if (key_is_cert(key) && key_cert_check_authority(key, 1, 0, lookup, &reason)) { error("%s", reason); auth_debug_add("%s", reason); return 0; } host_status = check_key_in_hostfiles(pw, key, lookup, _PATH_SSH_SYSTEM_HOSTFILE, options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE); /* backward compat if no key has been found. */ if (host_status == HOST_NEW) { host_status = check_key_in_hostfiles(pw, key, lookup, _PATH_SSH_SYSTEM_HOSTFILE2, options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE2); } if (host_status == HOST_OK) { if (key_is_cert(key)) { fp = key_fingerprint(key->cert->signature_key, SSH_FP_MD5, SSH_FP_HEX); verbose("Accepted certificate ID \"%s\" signed by " "%s CA %s from %s@%s", key->cert->key_id, key_type(key->cert->signature_key), fp, cuser, lookup); } else { fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX); verbose("Accepted %s public key %s from %s@%s", key_type(key), fp, cuser, lookup); } free(fp); } return (host_status == HOST_OK); } Authmethod method_hostbased = { "hostbased", userauth_hostbased, &options.hostbased_authentication };