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288fd0218d
This is identical to the standard "publickey" method, but it also includes the initial server hostkey in the message signed by the client. feedback / ok markus@ OpenBSD-Commit-ID: 7ea01bb7238a560c1bfb426fda0c10a8aac07862
1095 lines
31 KiB
C
1095 lines
31 KiB
C
/* $OpenBSD: auth2-pubkey.c,v 1.112 2021/12/19 22:12:30 djm Exp $ */
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/*
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* Copyright (c) 2000 Markus Friedl. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "includes.h"
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <fcntl.h>
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#ifdef HAVE_PATHS_H
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# include <paths.h>
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#endif
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#include <pwd.h>
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#include <signal.h>
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#include <stdio.h>
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#include <stdarg.h>
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#include <string.h>
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#include <time.h>
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#include <unistd.h>
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#include <limits.h>
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#include "xmalloc.h"
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#include "ssh.h"
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#include "ssh2.h"
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#include "packet.h"
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#include "kex.h"
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#include "sshbuf.h"
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#include "log.h"
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#include "misc.h"
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#include "servconf.h"
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#include "compat.h"
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#include "sshkey.h"
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#include "hostfile.h"
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#include "auth.h"
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#include "pathnames.h"
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#include "uidswap.h"
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#include "auth-options.h"
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#include "canohost.h"
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#ifdef GSSAPI
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#include "ssh-gss.h"
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#endif
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#include "monitor_wrap.h"
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#include "authfile.h"
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#include "match.h"
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#include "ssherr.h"
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#include "kex.h"
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#include "channels.h" /* XXX for session.h */
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#include "session.h" /* XXX for child_set_env(); refactor? */
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#include "sk-api.h"
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/* import */
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extern ServerOptions options;
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static char *
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format_key(const struct sshkey *key)
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{
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char *ret, *fp = sshkey_fingerprint(key,
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options.fingerprint_hash, SSH_FP_DEFAULT);
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xasprintf(&ret, "%s %s", sshkey_type(key), fp);
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free(fp);
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return ret;
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}
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static int
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userauth_pubkey(struct ssh *ssh, const char *method)
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{
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Authctxt *authctxt = ssh->authctxt;
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struct passwd *pw = authctxt->pw;
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struct sshbuf *b = NULL;
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struct sshkey *key = NULL, *hostkey = NULL;
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char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL;
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u_char *pkblob = NULL, *sig = NULL, have_sig;
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size_t blen, slen;
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int hostbound, r, pktype;
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int req_presence = 0, req_verify = 0, authenticated = 0;
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struct sshauthopt *authopts = NULL;
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struct sshkey_sig_details *sig_details = NULL;
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hostbound = strcmp(method, "publickey-hostbound-v00@openssh.com") == 0;
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if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 ||
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(r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 ||
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(r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0)
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fatal_fr(r, "parse %s packet", method);
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/* hostbound auth includes the hostkey offered at initial KEX */
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if (hostbound) {
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if ((r = sshpkt_getb_froms(ssh, &b)) != 0 ||
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(r = sshkey_fromb(b, &hostkey)) != 0)
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fatal_fr(r, "parse %s hostkey", method);
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if (ssh->kex->initial_hostkey == NULL)
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fatal_f("internal error: initial hostkey not recorded");
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if (!sshkey_equal(hostkey, ssh->kex->initial_hostkey))
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fatal_f("%s packet contained wrong host key", method);
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sshbuf_free(b);
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b = NULL;
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}
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if (log_level_get() >= SYSLOG_LEVEL_DEBUG2) {
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char *keystring;
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struct sshbuf *pkbuf;
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if ((pkbuf = sshbuf_from(pkblob, blen)) == NULL)
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fatal_f("sshbuf_from failed");
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if ((keystring = sshbuf_dtob64_string(pkbuf, 0)) == NULL)
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fatal_f("sshbuf_dtob64 failed");
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debug2_f("%s user %s %s public key %s %s",
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authctxt->valid ? "valid" : "invalid", authctxt->user,
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have_sig ? "attempting" : "querying", pkalg, keystring);
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sshbuf_free(pkbuf);
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free(keystring);
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}
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pktype = sshkey_type_from_name(pkalg);
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if (pktype == KEY_UNSPEC) {
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/* this is perfectly legal */
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verbose_f("unsupported public key algorithm: %s", pkalg);
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goto done;
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}
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if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
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error_fr(r, "parse key");
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goto done;
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}
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if (key == NULL) {
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error_f("cannot decode key: %s", pkalg);
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goto done;
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}
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if (key->type != pktype) {
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error_f("type mismatch for decoded key "
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"(received %d, expected %d)", key->type, pktype);
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goto done;
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}
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if (sshkey_type_plain(key->type) == KEY_RSA &&
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(ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
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logit("Refusing RSA key because client uses unsafe "
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"signature scheme");
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goto done;
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}
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if (auth2_key_already_used(authctxt, key)) {
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logit("refusing previously-used %s key", sshkey_type(key));
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goto done;
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}
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if (match_pattern_list(pkalg, options.pubkey_accepted_algos, 0) != 1) {
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logit_f("key type %s not in PubkeyAcceptedAlgorithms",
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sshkey_ssh_name(key));
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goto done;
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}
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if ((r = sshkey_check_cert_sigtype(key,
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options.ca_sign_algorithms)) != 0) {
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logit_fr(r, "certificate signature algorithm %s",
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(key->cert == NULL || key->cert->signature_type == NULL) ?
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"(null)" : key->cert->signature_type);
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goto done;
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}
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key_s = format_key(key);
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if (sshkey_is_cert(key))
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ca_s = format_key(key->cert->signature_key);
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if (have_sig) {
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debug3_f("%s have %s signature for %s%s%s",
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method, pkalg, key_s,
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ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s);
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if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 ||
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(r = sshpkt_get_end(ssh)) != 0)
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fatal_fr(r, "parse signature packet");
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if ((b = sshbuf_new()) == NULL)
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fatal_f("sshbuf_new failed");
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if (ssh->compat & SSH_OLD_SESSIONID) {
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if ((r = sshbuf_putb(b, ssh->kex->session_id)) != 0)
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fatal_fr(r, "put old session id");
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} else {
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if ((r = sshbuf_put_stringb(b,
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ssh->kex->session_id)) != 0)
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fatal_fr(r, "put session id");
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}
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if (!authctxt->valid || authctxt->user == NULL) {
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debug2_f("disabled because of invalid user");
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goto done;
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}
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/* reconstruct packet */
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xasprintf(&userstyle, "%s%s%s", authctxt->user,
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authctxt->style ? ":" : "",
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authctxt->style ? authctxt->style : "");
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if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
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(r = sshbuf_put_cstring(b, userstyle)) != 0 ||
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(r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
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(r = sshbuf_put_cstring(b, method)) != 0 ||
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(r = sshbuf_put_u8(b, have_sig)) != 0 ||
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(r = sshbuf_put_cstring(b, pkalg)) != 0 ||
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(r = sshbuf_put_string(b, pkblob, blen)) != 0)
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fatal_fr(r, "reconstruct %s packet", method);
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if (hostbound &&
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(r = sshkey_puts(ssh->kex->initial_hostkey, b)) != 0)
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fatal_fr(r, "reconstruct %s packet", method);
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#ifdef DEBUG_PK
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sshbuf_dump(b, stderr);
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#endif
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/* test for correct signature */
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authenticated = 0;
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if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) &&
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PRIVSEP(sshkey_verify(key, sig, slen,
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sshbuf_ptr(b), sshbuf_len(b),
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(ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL,
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ssh->compat, &sig_details)) == 0) {
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authenticated = 1;
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}
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if (authenticated == 1 && sig_details != NULL) {
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auth2_record_info(authctxt, "signature count = %u",
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sig_details->sk_counter);
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debug_f("sk_counter = %u, sk_flags = 0x%02x",
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sig_details->sk_counter, sig_details->sk_flags);
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req_presence = (options.pubkey_auth_options &
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PUBKEYAUTH_TOUCH_REQUIRED) ||
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!authopts->no_require_user_presence;
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if (req_presence && (sig_details->sk_flags &
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SSH_SK_USER_PRESENCE_REQD) == 0) {
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error("public key %s signature for %s%s from "
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"%.128s port %d rejected: user presence "
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"(authenticator touch) requirement "
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"not met ", key_s,
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authctxt->valid ? "" : "invalid user ",
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authctxt->user, ssh_remote_ipaddr(ssh),
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ssh_remote_port(ssh));
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authenticated = 0;
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goto done;
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}
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req_verify = (options.pubkey_auth_options &
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PUBKEYAUTH_VERIFY_REQUIRED) ||
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authopts->require_verify;
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if (req_verify && (sig_details->sk_flags &
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SSH_SK_USER_VERIFICATION_REQD) == 0) {
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error("public key %s signature for %s%s from "
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"%.128s port %d rejected: user "
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"verification requirement not met ", key_s,
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authctxt->valid ? "" : "invalid user ",
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authctxt->user, ssh_remote_ipaddr(ssh),
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ssh_remote_port(ssh));
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authenticated = 0;
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goto done;
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}
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}
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auth2_record_key(authctxt, authenticated, key);
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} else {
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debug_f("%s test pkalg %s pkblob %s%s%s", method, pkalg, key_s,
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ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s);
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if ((r = sshpkt_get_end(ssh)) != 0)
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fatal_fr(r, "parse packet");
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if (!authctxt->valid || authctxt->user == NULL) {
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debug2_f("disabled because of invalid user");
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goto done;
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}
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/* XXX fake reply and always send PK_OK ? */
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/*
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* XXX this allows testing whether a user is allowed
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* to login: if you happen to have a valid pubkey this
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* message is sent. the message is NEVER sent at all
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* if a user is not allowed to login. is this an
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* issue? -markus
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*/
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if (PRIVSEP(user_key_allowed(ssh, pw, key, 0, NULL))) {
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if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK))
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!= 0 ||
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(r = sshpkt_put_cstring(ssh, pkalg)) != 0 ||
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(r = sshpkt_put_string(ssh, pkblob, blen)) != 0 ||
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(r = sshpkt_send(ssh)) != 0 ||
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(r = ssh_packet_write_wait(ssh)) != 0)
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fatal_fr(r, "send packet");
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authctxt->postponed = 1;
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}
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}
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done:
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if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) {
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debug_f("key options inconsistent with existing");
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authenticated = 0;
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}
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debug2_f("authenticated %d pkalg %s", authenticated, pkalg);
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sshbuf_free(b);
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sshauthopt_free(authopts);
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sshkey_free(key);
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sshkey_free(hostkey);
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free(userstyle);
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free(pkalg);
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free(pkblob);
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free(key_s);
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free(ca_s);
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free(sig);
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sshkey_sig_details_free(sig_details);
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return authenticated;
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}
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static int
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match_principals_option(const char *principal_list, struct sshkey_cert *cert)
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{
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char *result;
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u_int i;
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/* XXX percent_expand() sequences for authorized_principals? */
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for (i = 0; i < cert->nprincipals; i++) {
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if ((result = match_list(cert->principals[i],
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principal_list, NULL)) != NULL) {
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debug3("matched principal from key options \"%.100s\"",
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result);
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free(result);
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return 1;
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}
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}
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return 0;
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}
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/*
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* Process a single authorized_principals format line. Returns 0 and sets
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* authoptsp is principal is authorised, -1 otherwise. "loc" is used as a
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* log preamble for file/line information.
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*/
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static int
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check_principals_line(struct ssh *ssh, char *cp, const struct sshkey_cert *cert,
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const char *loc, struct sshauthopt **authoptsp)
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{
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u_int i, found = 0;
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char *ep, *line_opts;
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const char *reason = NULL;
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struct sshauthopt *opts = NULL;
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if (authoptsp != NULL)
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*authoptsp = NULL;
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/* Trim trailing whitespace. */
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ep = cp + strlen(cp) - 1;
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while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t'))
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*ep-- = '\0';
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/*
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* If the line has internal whitespace then assume it has
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* key options.
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*/
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line_opts = NULL;
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if ((ep = strrchr(cp, ' ')) != NULL ||
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(ep = strrchr(cp, '\t')) != NULL) {
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for (; *ep == ' ' || *ep == '\t'; ep++)
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;
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line_opts = cp;
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cp = ep;
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}
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if ((opts = sshauthopt_parse(line_opts, &reason)) == NULL) {
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debug("%s: bad principals options: %s", loc, reason);
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auth_debug_add("%s: bad principals options: %s", loc, reason);
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return -1;
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}
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/* Check principals in cert against those on line */
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for (i = 0; i < cert->nprincipals; i++) {
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if (strcmp(cp, cert->principals[i]) != 0)
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continue;
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debug3("%s: matched principal \"%.100s\"",
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loc, cert->principals[i]);
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found = 1;
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}
|
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if (found && authoptsp != NULL) {
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*authoptsp = opts;
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opts = NULL;
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}
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sshauthopt_free(opts);
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return found ? 0 : -1;
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}
|
|
|
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static int
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process_principals(struct ssh *ssh, FILE *f, const char *file,
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const struct sshkey_cert *cert, struct sshauthopt **authoptsp)
|
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{
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char loc[256], *line = NULL, *cp, *ep;
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size_t linesize = 0;
|
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u_long linenum = 0, nonblank = 0;
|
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u_int found_principal = 0;
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|
|
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if (authoptsp != NULL)
|
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*authoptsp = NULL;
|
|
|
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while (getline(&line, &linesize, f) != -1) {
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linenum++;
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/* Always consume entire input */
|
|
if (found_principal)
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continue;
|
|
|
|
/* Skip leading whitespace. */
|
|
for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
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;
|
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/* Skip blank and comment lines. */
|
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if ((ep = strchr(cp, '#')) != NULL)
|
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*ep = '\0';
|
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if (!*cp || *cp == '\n')
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continue;
|
|
|
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nonblank++;
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snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
|
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if (check_principals_line(ssh, cp, cert, loc, authoptsp) == 0)
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found_principal = 1;
|
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}
|
|
debug2_f("%s: processed %lu/%lu lines", file, nonblank, linenum);
|
|
free(line);
|
|
return found_principal;
|
|
}
|
|
|
|
/* XXX remove pw args here and elsewhere once ssh->authctxt is guaranteed */
|
|
|
|
static int
|
|
match_principals_file(struct ssh *ssh, struct passwd *pw, char *file,
|
|
struct sshkey_cert *cert, struct sshauthopt **authoptsp)
|
|
{
|
|
FILE *f;
|
|
int success;
|
|
|
|
if (authoptsp != NULL)
|
|
*authoptsp = NULL;
|
|
|
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temporarily_use_uid(pw);
|
|
debug("trying authorized principals file %s", file);
|
|
if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
|
|
restore_uid();
|
|
return 0;
|
|
}
|
|
success = process_principals(ssh, f, file, cert, authoptsp);
|
|
fclose(f);
|
|
restore_uid();
|
|
return success;
|
|
}
|
|
|
|
/*
|
|
* Checks whether principal is allowed in output of command.
|
|
* returns 1 if the principal is allowed or 0 otherwise.
|
|
*/
|
|
static int
|
|
match_principals_command(struct ssh *ssh, struct passwd *user_pw,
|
|
const struct sshkey *key, struct sshauthopt **authoptsp)
|
|
{
|
|
struct passwd *runas_pw = NULL;
|
|
const struct sshkey_cert *cert = key->cert;
|
|
FILE *f = NULL;
|
|
int r, ok, found_principal = 0;
|
|
int i, ac = 0, uid_swapped = 0;
|
|
pid_t pid;
|
|
char *tmp, *username = NULL, *command = NULL, **av = NULL;
|
|
char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL;
|
|
char serial_s[32], uidstr[32];
|
|
void (*osigchld)(int);
|
|
|
|
if (authoptsp != NULL)
|
|
*authoptsp = NULL;
|
|
if (options.authorized_principals_command == NULL)
|
|
return 0;
|
|
if (options.authorized_principals_command_user == NULL) {
|
|
error("No user for AuthorizedPrincipalsCommand specified, "
|
|
"skipping");
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* NB. all returns later this function should go via "out" to
|
|
* ensure the original SIGCHLD handler is restored properly.
|
|
*/
|
|
osigchld = ssh_signal(SIGCHLD, SIG_DFL);
|
|
|
|
/* Prepare and verify the user for the command */
|
|
username = percent_expand(options.authorized_principals_command_user,
|
|
"u", user_pw->pw_name, (char *)NULL);
|
|
runas_pw = getpwnam(username);
|
|
if (runas_pw == NULL) {
|
|
error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s",
|
|
username, strerror(errno));
|
|
goto out;
|
|
}
|
|
|
|
/* Turn the command into an argument vector */
|
|
if (argv_split(options.authorized_principals_command,
|
|
&ac, &av, 0) != 0) {
|
|
error("AuthorizedPrincipalsCommand \"%s\" contains "
|
|
"invalid quotes", options.authorized_principals_command);
|
|
goto out;
|
|
}
|
|
if (ac == 0) {
|
|
error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
|
|
options.authorized_principals_command);
|
|
goto out;
|
|
}
|
|
if ((ca_fp = sshkey_fingerprint(cert->signature_key,
|
|
options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
|
|
error_f("sshkey_fingerprint failed");
|
|
goto out;
|
|
}
|
|
if ((key_fp = sshkey_fingerprint(key,
|
|
options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
|
|
error_f("sshkey_fingerprint failed");
|
|
goto out;
|
|
}
|
|
if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) {
|
|
error_fr(r, "sshkey_to_base64 failed");
|
|
goto out;
|
|
}
|
|
if ((r = sshkey_to_base64(key, &keytext)) != 0) {
|
|
error_fr(r, "sshkey_to_base64 failed");
|
|
goto out;
|
|
}
|
|
snprintf(serial_s, sizeof(serial_s), "%llu",
|
|
(unsigned long long)cert->serial);
|
|
snprintf(uidstr, sizeof(uidstr), "%llu",
|
|
(unsigned long long)user_pw->pw_uid);
|
|
for (i = 1; i < ac; i++) {
|
|
tmp = percent_expand(av[i],
|
|
"U", uidstr,
|
|
"u", user_pw->pw_name,
|
|
"h", user_pw->pw_dir,
|
|
"t", sshkey_ssh_name(key),
|
|
"T", sshkey_ssh_name(cert->signature_key),
|
|
"f", key_fp,
|
|
"F", ca_fp,
|
|
"k", keytext,
|
|
"K", catext,
|
|
"i", cert->key_id,
|
|
"s", serial_s,
|
|
(char *)NULL);
|
|
if (tmp == NULL)
|
|
fatal_f("percent_expand failed");
|
|
free(av[i]);
|
|
av[i] = tmp;
|
|
}
|
|
/* Prepare a printable command for logs, etc. */
|
|
command = argv_assemble(ac, av);
|
|
|
|
if ((pid = subprocess("AuthorizedPrincipalsCommand", command,
|
|
ac, av, &f,
|
|
SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD,
|
|
runas_pw, temporarily_use_uid, restore_uid)) == 0)
|
|
goto out;
|
|
|
|
uid_swapped = 1;
|
|
temporarily_use_uid(runas_pw);
|
|
|
|
ok = process_principals(ssh, f, "(command)", cert, authoptsp);
|
|
|
|
fclose(f);
|
|
f = NULL;
|
|
|
|
if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0)
|
|
goto out;
|
|
|
|
/* Read completed successfully */
|
|
found_principal = ok;
|
|
out:
|
|
if (f != NULL)
|
|
fclose(f);
|
|
ssh_signal(SIGCHLD, osigchld);
|
|
for (i = 0; i < ac; i++)
|
|
free(av[i]);
|
|
free(av);
|
|
if (uid_swapped)
|
|
restore_uid();
|
|
free(command);
|
|
free(username);
|
|
free(ca_fp);
|
|
free(key_fp);
|
|
free(catext);
|
|
free(keytext);
|
|
return found_principal;
|
|
}
|
|
|
|
/*
|
|
* Check a single line of an authorized_keys-format file. Returns 0 if key
|
|
* matches, -1 otherwise. Will return key/cert options via *authoptsp
|
|
* on success. "loc" is used as file/line location in log messages.
|
|
*/
|
|
static int
|
|
check_authkey_line(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
|
|
char *cp, const char *loc, struct sshauthopt **authoptsp)
|
|
{
|
|
int want_keytype = sshkey_is_cert(key) ? KEY_UNSPEC : key->type;
|
|
struct sshkey *found = NULL;
|
|
struct sshauthopt *keyopts = NULL, *certopts = NULL, *finalopts = NULL;
|
|
char *key_options = NULL, *fp = NULL;
|
|
const char *reason = NULL;
|
|
int ret = -1;
|
|
|
|
if (authoptsp != NULL)
|
|
*authoptsp = NULL;
|
|
|
|
if ((found = sshkey_new(want_keytype)) == NULL) {
|
|
debug3_f("keytype %d failed", want_keytype);
|
|
goto out;
|
|
}
|
|
|
|
/* XXX djm: peek at key type in line and skip if unwanted */
|
|
|
|
if (sshkey_read(found, &cp) != 0) {
|
|
/* no key? check for options */
|
|
debug2("%s: check options: '%s'", loc, cp);
|
|
key_options = cp;
|
|
if (sshkey_advance_past_options(&cp) != 0) {
|
|
reason = "invalid key option string";
|
|
goto fail_reason;
|
|
}
|
|
skip_space(&cp);
|
|
if (sshkey_read(found, &cp) != 0) {
|
|
/* still no key? advance to next line*/
|
|
debug2("%s: advance: '%s'", loc, cp);
|
|
goto out;
|
|
}
|
|
}
|
|
/* Parse key options now; we need to know if this is a CA key */
|
|
if ((keyopts = sshauthopt_parse(key_options, &reason)) == NULL) {
|
|
debug("%s: bad key options: %s", loc, reason);
|
|
auth_debug_add("%s: bad key options: %s", loc, reason);
|
|
goto out;
|
|
}
|
|
/* Ignore keys that don't match or incorrectly marked as CAs */
|
|
if (sshkey_is_cert(key)) {
|
|
/* Certificate; check signature key against CA */
|
|
if (!sshkey_equal(found, key->cert->signature_key) ||
|
|
!keyopts->cert_authority)
|
|
goto out;
|
|
} else {
|
|
/* Plain key: check it against key found in file */
|
|
if (!sshkey_equal(found, key) || keyopts->cert_authority)
|
|
goto out;
|
|
}
|
|
|
|
/* We have a candidate key, perform authorisation checks */
|
|
if ((fp = sshkey_fingerprint(found,
|
|
options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
|
|
fatal_f("fingerprint failed");
|
|
|
|
debug("%s: matching %s found: %s %s", loc,
|
|
sshkey_is_cert(key) ? "CA" : "key", sshkey_type(found), fp);
|
|
|
|
if (auth_authorise_keyopts(ssh, pw, keyopts,
|
|
sshkey_is_cert(key), loc) != 0) {
|
|
reason = "Refused by key options";
|
|
goto fail_reason;
|
|
}
|
|
/* That's all we need for plain keys. */
|
|
if (!sshkey_is_cert(key)) {
|
|
verbose("Accepted key %s %s found at %s",
|
|
sshkey_type(found), fp, loc);
|
|
finalopts = keyopts;
|
|
keyopts = NULL;
|
|
goto success;
|
|
}
|
|
|
|
/*
|
|
* Additional authorisation for certificates.
|
|
*/
|
|
|
|
/* Parse and check options present in certificate */
|
|
if ((certopts = sshauthopt_from_cert(key)) == NULL) {
|
|
reason = "Invalid certificate options";
|
|
goto fail_reason;
|
|
}
|
|
if (auth_authorise_keyopts(ssh, pw, certopts, 0, loc) != 0) {
|
|
reason = "Refused by certificate options";
|
|
goto fail_reason;
|
|
}
|
|
if ((finalopts = sshauthopt_merge(keyopts, certopts, &reason)) == NULL)
|
|
goto fail_reason;
|
|
|
|
/*
|
|
* If the user has specified a list of principals as
|
|
* a key option, then prefer that list to matching
|
|
* their username in the certificate principals list.
|
|
*/
|
|
if (keyopts->cert_principals != NULL &&
|
|
!match_principals_option(keyopts->cert_principals, key->cert)) {
|
|
reason = "Certificate does not contain an authorized principal";
|
|
goto fail_reason;
|
|
}
|
|
if (sshkey_cert_check_authority_now(key, 0, 0, 0,
|
|
keyopts->cert_principals == NULL ? pw->pw_name : NULL,
|
|
&reason) != 0)
|
|
goto fail_reason;
|
|
|
|
verbose("Accepted certificate ID \"%s\" (serial %llu) "
|
|
"signed by CA %s %s found at %s",
|
|
key->cert->key_id,
|
|
(unsigned long long)key->cert->serial,
|
|
sshkey_type(found), fp, loc);
|
|
|
|
success:
|
|
if (finalopts == NULL)
|
|
fatal_f("internal error: missing options");
|
|
if (authoptsp != NULL) {
|
|
*authoptsp = finalopts;
|
|
finalopts = NULL;
|
|
}
|
|
/* success */
|
|
ret = 0;
|
|
goto out;
|
|
|
|
fail_reason:
|
|
error("%s", reason);
|
|
auth_debug_add("%s", reason);
|
|
out:
|
|
free(fp);
|
|
sshauthopt_free(keyopts);
|
|
sshauthopt_free(certopts);
|
|
sshauthopt_free(finalopts);
|
|
sshkey_free(found);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Checks whether key is allowed in authorized_keys-format file,
|
|
* returns 1 if the key is allowed or 0 otherwise.
|
|
*/
|
|
static int
|
|
check_authkeys_file(struct ssh *ssh, struct passwd *pw, FILE *f,
|
|
char *file, struct sshkey *key, struct sshauthopt **authoptsp)
|
|
{
|
|
char *cp, *line = NULL, loc[256];
|
|
size_t linesize = 0;
|
|
int found_key = 0;
|
|
u_long linenum = 0, nonblank = 0;
|
|
|
|
if (authoptsp != NULL)
|
|
*authoptsp = NULL;
|
|
|
|
while (getline(&line, &linesize, f) != -1) {
|
|
linenum++;
|
|
/* Always consume entire file */
|
|
if (found_key)
|
|
continue;
|
|
|
|
/* Skip leading whitespace, empty and comment lines. */
|
|
cp = line;
|
|
skip_space(&cp);
|
|
if (!*cp || *cp == '\n' || *cp == '#')
|
|
continue;
|
|
|
|
nonblank++;
|
|
snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
|
|
if (check_authkey_line(ssh, pw, key, cp, loc, authoptsp) == 0)
|
|
found_key = 1;
|
|
}
|
|
free(line);
|
|
debug2_f("%s: processed %lu/%lu lines", file, nonblank, linenum);
|
|
return found_key;
|
|
}
|
|
|
|
/* Authenticate a certificate key against TrustedUserCAKeys */
|
|
static int
|
|
user_cert_trusted_ca(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
|
|
struct sshauthopt **authoptsp)
|
|
{
|
|
char *ca_fp, *principals_file = NULL;
|
|
const char *reason;
|
|
struct sshauthopt *principals_opts = NULL, *cert_opts = NULL;
|
|
struct sshauthopt *final_opts = NULL;
|
|
int r, ret = 0, found_principal = 0, use_authorized_principals;
|
|
|
|
if (authoptsp != NULL)
|
|
*authoptsp = NULL;
|
|
|
|
if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL)
|
|
return 0;
|
|
|
|
if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
|
|
options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
|
|
return 0;
|
|
|
|
if ((r = sshkey_in_file(key->cert->signature_key,
|
|
options.trusted_user_ca_keys, 1, 0)) != 0) {
|
|
debug2_fr(r, "CA %s %s is not listed in %s",
|
|
sshkey_type(key->cert->signature_key), ca_fp,
|
|
options.trusted_user_ca_keys);
|
|
goto out;
|
|
}
|
|
/*
|
|
* If AuthorizedPrincipals is in use, then compare the certificate
|
|
* principals against the names in that file rather than matching
|
|
* against the username.
|
|
*/
|
|
if ((principals_file = authorized_principals_file(pw)) != NULL) {
|
|
if (match_principals_file(ssh, pw, principals_file,
|
|
key->cert, &principals_opts))
|
|
found_principal = 1;
|
|
}
|
|
/* Try querying command if specified */
|
|
if (!found_principal && match_principals_command(ssh, pw, key,
|
|
&principals_opts))
|
|
found_principal = 1;
|
|
/* If principals file or command is specified, then require a match */
|
|
use_authorized_principals = principals_file != NULL ||
|
|
options.authorized_principals_command != NULL;
|
|
if (!found_principal && use_authorized_principals) {
|
|
reason = "Certificate does not contain an authorized principal";
|
|
goto fail_reason;
|
|
}
|
|
if (use_authorized_principals && principals_opts == NULL)
|
|
fatal_f("internal error: missing principals_opts");
|
|
if (sshkey_cert_check_authority_now(key, 0, 1, 0,
|
|
use_authorized_principals ? NULL : pw->pw_name, &reason) != 0)
|
|
goto fail_reason;
|
|
|
|
/* Check authority from options in key and from principals file/cmd */
|
|
if ((cert_opts = sshauthopt_from_cert(key)) == NULL) {
|
|
reason = "Invalid certificate options";
|
|
goto fail_reason;
|
|
}
|
|
if (auth_authorise_keyopts(ssh, pw, cert_opts, 0, "cert") != 0) {
|
|
reason = "Refused by certificate options";
|
|
goto fail_reason;
|
|
}
|
|
if (principals_opts == NULL) {
|
|
final_opts = cert_opts;
|
|
cert_opts = NULL;
|
|
} else {
|
|
if (auth_authorise_keyopts(ssh, pw, principals_opts, 0,
|
|
"principals") != 0) {
|
|
reason = "Refused by certificate principals options";
|
|
goto fail_reason;
|
|
}
|
|
if ((final_opts = sshauthopt_merge(principals_opts,
|
|
cert_opts, &reason)) == NULL) {
|
|
fail_reason:
|
|
error("%s", reason);
|
|
auth_debug_add("%s", reason);
|
|
goto out;
|
|
}
|
|
}
|
|
|
|
/* Success */
|
|
verbose("Accepted certificate ID \"%s\" (serial %llu) signed by "
|
|
"%s CA %s via %s", key->cert->key_id,
|
|
(unsigned long long)key->cert->serial,
|
|
sshkey_type(key->cert->signature_key), ca_fp,
|
|
options.trusted_user_ca_keys);
|
|
if (authoptsp != NULL) {
|
|
*authoptsp = final_opts;
|
|
final_opts = NULL;
|
|
}
|
|
ret = 1;
|
|
out:
|
|
sshauthopt_free(principals_opts);
|
|
sshauthopt_free(cert_opts);
|
|
sshauthopt_free(final_opts);
|
|
free(principals_file);
|
|
free(ca_fp);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Checks whether key is allowed in file.
|
|
* returns 1 if the key is allowed or 0 otherwise.
|
|
*/
|
|
static int
|
|
user_key_allowed2(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
|
|
char *file, struct sshauthopt **authoptsp)
|
|
{
|
|
FILE *f;
|
|
int found_key = 0;
|
|
|
|
if (authoptsp != NULL)
|
|
*authoptsp = NULL;
|
|
|
|
/* Temporarily use the user's uid. */
|
|
temporarily_use_uid(pw);
|
|
|
|
debug("trying public key file %s", file);
|
|
if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
|
|
found_key = check_authkeys_file(ssh, pw, f, file,
|
|
key, authoptsp);
|
|
fclose(f);
|
|
}
|
|
|
|
restore_uid();
|
|
return found_key;
|
|
}
|
|
|
|
/*
|
|
* Checks whether key is allowed in output of command.
|
|
* returns 1 if the key is allowed or 0 otherwise.
|
|
*/
|
|
static int
|
|
user_key_command_allowed2(struct ssh *ssh, struct passwd *user_pw,
|
|
struct sshkey *key, struct sshauthopt **authoptsp)
|
|
{
|
|
struct passwd *runas_pw = NULL;
|
|
FILE *f = NULL;
|
|
int r, ok, found_key = 0;
|
|
int i, uid_swapped = 0, ac = 0;
|
|
pid_t pid;
|
|
char *username = NULL, *key_fp = NULL, *keytext = NULL;
|
|
char uidstr[32], *tmp, *command = NULL, **av = NULL;
|
|
void (*osigchld)(int);
|
|
|
|
if (authoptsp != NULL)
|
|
*authoptsp = NULL;
|
|
if (options.authorized_keys_command == NULL)
|
|
return 0;
|
|
if (options.authorized_keys_command_user == NULL) {
|
|
error("No user for AuthorizedKeysCommand specified, skipping");
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* NB. all returns later this function should go via "out" to
|
|
* ensure the original SIGCHLD handler is restored properly.
|
|
*/
|
|
osigchld = ssh_signal(SIGCHLD, SIG_DFL);
|
|
|
|
/* Prepare and verify the user for the command */
|
|
username = percent_expand(options.authorized_keys_command_user,
|
|
"u", user_pw->pw_name, (char *)NULL);
|
|
runas_pw = getpwnam(username);
|
|
if (runas_pw == NULL) {
|
|
error("AuthorizedKeysCommandUser \"%s\" not found: %s",
|
|
username, strerror(errno));
|
|
goto out;
|
|
}
|
|
|
|
/* Prepare AuthorizedKeysCommand */
|
|
if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash,
|
|
SSH_FP_DEFAULT)) == NULL) {
|
|
error_f("sshkey_fingerprint failed");
|
|
goto out;
|
|
}
|
|
if ((r = sshkey_to_base64(key, &keytext)) != 0) {
|
|
error_fr(r, "sshkey_to_base64 failed");
|
|
goto out;
|
|
}
|
|
|
|
/* Turn the command into an argument vector */
|
|
if (argv_split(options.authorized_keys_command, &ac, &av, 0) != 0) {
|
|
error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
|
|
options.authorized_keys_command);
|
|
goto out;
|
|
}
|
|
if (ac == 0) {
|
|
error("AuthorizedKeysCommand \"%s\" yielded no arguments",
|
|
options.authorized_keys_command);
|
|
goto out;
|
|
}
|
|
snprintf(uidstr, sizeof(uidstr), "%llu",
|
|
(unsigned long long)user_pw->pw_uid);
|
|
for (i = 1; i < ac; i++) {
|
|
tmp = percent_expand(av[i],
|
|
"U", uidstr,
|
|
"u", user_pw->pw_name,
|
|
"h", user_pw->pw_dir,
|
|
"t", sshkey_ssh_name(key),
|
|
"f", key_fp,
|
|
"k", keytext,
|
|
(char *)NULL);
|
|
if (tmp == NULL)
|
|
fatal_f("percent_expand failed");
|
|
free(av[i]);
|
|
av[i] = tmp;
|
|
}
|
|
/* Prepare a printable command for logs, etc. */
|
|
command = argv_assemble(ac, av);
|
|
|
|
/*
|
|
* If AuthorizedKeysCommand was run without arguments
|
|
* then fall back to the old behaviour of passing the
|
|
* target username as a single argument.
|
|
*/
|
|
if (ac == 1) {
|
|
av = xreallocarray(av, ac + 2, sizeof(*av));
|
|
av[1] = xstrdup(user_pw->pw_name);
|
|
av[2] = NULL;
|
|
/* Fix up command too, since it is used in log messages */
|
|
free(command);
|
|
xasprintf(&command, "%s %s", av[0], av[1]);
|
|
}
|
|
|
|
if ((pid = subprocess("AuthorizedKeysCommand", command,
|
|
ac, av, &f,
|
|
SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD,
|
|
runas_pw, temporarily_use_uid, restore_uid)) == 0)
|
|
goto out;
|
|
|
|
uid_swapped = 1;
|
|
temporarily_use_uid(runas_pw);
|
|
|
|
ok = check_authkeys_file(ssh, user_pw, f,
|
|
options.authorized_keys_command, key, authoptsp);
|
|
|
|
fclose(f);
|
|
f = NULL;
|
|
|
|
if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0)
|
|
goto out;
|
|
|
|
/* Read completed successfully */
|
|
found_key = ok;
|
|
out:
|
|
if (f != NULL)
|
|
fclose(f);
|
|
ssh_signal(SIGCHLD, osigchld);
|
|
for (i = 0; i < ac; i++)
|
|
free(av[i]);
|
|
free(av);
|
|
if (uid_swapped)
|
|
restore_uid();
|
|
free(command);
|
|
free(username);
|
|
free(key_fp);
|
|
free(keytext);
|
|
return found_key;
|
|
}
|
|
|
|
/*
|
|
* Check whether key authenticates and authorises the user.
|
|
*/
|
|
int
|
|
user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
|
|
int auth_attempt, struct sshauthopt **authoptsp)
|
|
{
|
|
u_int success = 0, i;
|
|
char *file;
|
|
struct sshauthopt *opts = NULL;
|
|
|
|
if (authoptsp != NULL)
|
|
*authoptsp = NULL;
|
|
|
|
if (auth_key_is_revoked(key))
|
|
return 0;
|
|
if (sshkey_is_cert(key) &&
|
|
auth_key_is_revoked(key->cert->signature_key))
|
|
return 0;
|
|
|
|
for (i = 0; !success && i < options.num_authkeys_files; i++) {
|
|
if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
|
|
continue;
|
|
file = expand_authorized_keys(
|
|
options.authorized_keys_files[i], pw);
|
|
success = user_key_allowed2(ssh, pw, key, file, &opts);
|
|
free(file);
|
|
if (!success) {
|
|
sshauthopt_free(opts);
|
|
opts = NULL;
|
|
}
|
|
}
|
|
if (success)
|
|
goto out;
|
|
|
|
if ((success = user_cert_trusted_ca(ssh, pw, key, &opts)) != 0)
|
|
goto out;
|
|
sshauthopt_free(opts);
|
|
opts = NULL;
|
|
|
|
if ((success = user_key_command_allowed2(ssh, pw, key, &opts)) != 0)
|
|
goto out;
|
|
sshauthopt_free(opts);
|
|
opts = NULL;
|
|
|
|
out:
|
|
if (success && authoptsp != NULL) {
|
|
*authoptsp = opts;
|
|
opts = NULL;
|
|
}
|
|
sshauthopt_free(opts);
|
|
return success;
|
|
}
|
|
|
|
Authmethod method_pubkey = {
|
|
"publickey",
|
|
"publickey-hostbound-v00@openssh.com",
|
|
userauth_pubkey,
|
|
&options.pubkey_authentication
|
|
};
|