This completely removes client-side support for the SSH 1 protocol, which was already disabled in 12 but is still enabled in 11. For that reason, we will not be able to merge 7.6p1 or newer back to 11.
833 lines
23 KiB
C
833 lines
23 KiB
C
/* $OpenBSD: auth2-pubkey.c,v 1.71 2017/09/07 23:48:09 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 <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 "buffer.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 "channels.h" /* XXX for session.h */
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#include "session.h" /* XXX for child_set_env(); refactor? */
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/* import */
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extern ServerOptions options;
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extern u_char *session_id2;
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extern u_int session_id2_len;
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static int
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userauth_pubkey(struct ssh *ssh)
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{
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Authctxt *authctxt = ssh->authctxt;
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struct sshbuf *b;
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struct sshkey *key = NULL;
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char *pkalg, *userstyle = NULL, *fp = NULL;
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u_char *pkblob, *sig, have_sig;
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size_t blen, slen;
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int r, pktype;
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int authenticated = 0;
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if (!authctxt->valid) {
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debug2("%s: disabled because of invalid user", __func__);
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return 0;
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}
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if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0)
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fatal("%s: sshpkt_get_u8 failed: %s", __func__, ssh_err(r));
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if (ssh->compat & SSH_BUG_PKAUTH) {
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debug2("%s: SSH_BUG_PKAUTH", __func__);
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if ((b = sshbuf_new()) == NULL)
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fatal("%s: sshbuf_new failed", __func__);
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/* no explicit pkalg given */
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/* so we have to extract the pkalg from the pkblob */
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/* XXX use sshbuf_from() */
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if ((r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0 ||
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(r = sshbuf_put(b, pkblob, blen)) != 0 ||
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(r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0)
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fatal("%s: failed: %s", __func__, ssh_err(r));
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sshbuf_free(b);
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} else {
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if ((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("%s: sshpkt_get_cstring failed: %s",
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__func__, ssh_err(r));
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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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logit("%s: unsupported public key algorithm: %s",
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__func__, 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("%s: could not parse key: %s", __func__, ssh_err(r));
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goto done;
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}
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if (key == NULL) {
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error("%s: cannot decode key: %s", __func__, pkalg);
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goto done;
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}
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if (key->type != pktype) {
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error("%s: type mismatch for decoded key "
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"(received %d, expected %d)", __func__, 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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fp = sshkey_fingerprint(key, options.fingerprint_hash, SSH_FP_DEFAULT);
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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(sshkey_ssh_name(key),
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options.pubkey_key_types, 0) != 1) {
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logit("%s: key type %s not in PubkeyAcceptedKeyTypes",
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__func__, sshkey_ssh_name(key));
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goto done;
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}
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if (have_sig) {
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debug3("%s: have signature for %s %s",
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__func__, sshkey_type(key), fp);
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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("%s: %s", __func__, ssh_err(r));
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if ((b = sshbuf_new()) == NULL)
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fatal("%s: sshbuf_new failed", __func__);
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if (ssh->compat & SSH_OLD_SESSIONID) {
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if ((r = sshbuf_put(b, session_id2,
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session_id2_len)) != 0)
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fatal("%s: sshbuf_put session id: %s",
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__func__, ssh_err(r));
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} else {
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if ((r = sshbuf_put_string(b, session_id2,
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session_id2_len)) != 0)
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fatal("%s: sshbuf_put_string session id: %s",
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__func__, ssh_err(r));
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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, ssh->compat & SSH_BUG_PKSERVICE ?
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"ssh-userauth" : authctxt->service)) != 0)
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fatal("%s: build packet failed: %s",
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__func__, ssh_err(r));
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if (ssh->compat & SSH_BUG_PKAUTH) {
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if ((r = sshbuf_put_u8(b, have_sig)) != 0)
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fatal("%s: build packet failed: %s",
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__func__, ssh_err(r));
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} else {
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if ((r = sshbuf_put_cstring(b, "publickey")) != 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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fatal("%s: build packet failed: %s",
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__func__, ssh_err(r));
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}
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if ((r = sshbuf_put_string(b, pkblob, blen)) != 0)
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fatal("%s: build packet failed: %s",
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__func__, ssh_err(r));
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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(authctxt->pw, key, 1)) &&
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PRIVSEP(sshkey_verify(key, sig, slen, sshbuf_ptr(b),
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sshbuf_len(b), ssh->compat)) == 0) {
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authenticated = 1;
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}
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sshbuf_free(b);
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free(sig);
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auth2_record_key(authctxt, authenticated, key);
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} else {
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debug("%s: test whether pkalg/pkblob are acceptable for %s %s",
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__func__, sshkey_type(key), fp);
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if ((r = sshpkt_get_end(ssh)) != 0)
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fatal("%s: %s", __func__, ssh_err(r));
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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(authctxt->pw, key, 0))) {
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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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fatal("%s: %s", __func__, ssh_err(r));
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ssh_packet_write_wait(ssh);
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authctxt->postponed = 1;
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}
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}
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if (authenticated != 1)
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auth_clear_options();
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done:
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debug2("%s: authenticated %d pkalg %s", __func__, authenticated, pkalg);
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sshkey_free(key);
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free(userstyle);
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free(pkalg);
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free(pkblob);
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free(fp);
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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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static int
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process_principals(FILE *f, const char *file, struct passwd *pw,
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const struct sshkey_cert *cert)
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{
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char line[SSH_MAX_PUBKEY_BYTES], *cp, *ep, *line_opts;
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u_long linenum = 0;
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u_int i, found_principal = 0;
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while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
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/* Always consume entire input */
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if (found_principal)
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continue;
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/* Skip leading whitespace. */
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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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/* 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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for (i = 0; i < cert->nprincipals; i++) {
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if (strcmp(cp, cert->principals[i]) == 0) {
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debug3("%s:%lu: matched principal \"%.100s\"",
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file, linenum, cert->principals[i]);
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if (auth_parse_options(pw, line_opts,
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file, linenum) != 1)
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continue;
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found_principal = 1;
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continue;
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}
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}
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}
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return found_principal;
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}
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static int
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match_principals_file(char *file, struct passwd *pw, struct sshkey_cert *cert)
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{
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FILE *f;
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int success;
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temporarily_use_uid(pw);
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debug("trying authorized principals file %s", file);
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if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
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restore_uid();
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return 0;
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}
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success = process_principals(f, file, pw, cert);
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fclose(f);
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restore_uid();
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return success;
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}
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/*
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* Checks whether principal is allowed in output of command.
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* returns 1 if the principal is allowed or 0 otherwise.
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*/
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static int
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match_principals_command(struct passwd *user_pw, const struct sshkey *key)
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{
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const struct sshkey_cert *cert = key->cert;
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FILE *f = NULL;
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int r, ok, found_principal = 0;
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struct passwd *pw;
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int i, ac = 0, uid_swapped = 0;
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pid_t pid;
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char *tmp, *username = NULL, *command = NULL, **av = NULL;
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char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL;
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char serial_s[16];
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void (*osigchld)(int);
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if (options.authorized_principals_command == NULL)
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return 0;
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if (options.authorized_principals_command_user == NULL) {
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error("No user for AuthorizedPrincipalsCommand specified, "
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"skipping");
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return 0;
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}
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/*
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* NB. all returns later this function should go via "out" to
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* ensure the original SIGCHLD handler is restored properly.
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*/
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osigchld = signal(SIGCHLD, SIG_DFL);
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/* Prepare and verify the user for the command */
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username = percent_expand(options.authorized_principals_command_user,
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"u", user_pw->pw_name, (char *)NULL);
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pw = getpwnam(username);
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if (pw == NULL) {
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error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s",
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username, strerror(errno));
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goto out;
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}
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/* Turn the command into an argument vector */
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if (argv_split(options.authorized_principals_command, &ac, &av) != 0) {
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error("AuthorizedPrincipalsCommand \"%s\" contains "
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"invalid quotes", command);
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goto out;
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}
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if (ac == 0) {
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error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
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command);
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goto out;
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}
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if ((ca_fp = sshkey_fingerprint(cert->signature_key,
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options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
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error("%s: sshkey_fingerprint failed", __func__);
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goto out;
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}
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if ((key_fp = sshkey_fingerprint(key,
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options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
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error("%s: sshkey_fingerprint failed", __func__);
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goto out;
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}
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if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) {
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error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
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goto out;
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}
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if ((r = sshkey_to_base64(key, &keytext)) != 0) {
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error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
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goto out;
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}
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snprintf(serial_s, sizeof(serial_s), "%llu",
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(unsigned long long)cert->serial);
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for (i = 1; i < ac; i++) {
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tmp = percent_expand(av[i],
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"u", user_pw->pw_name,
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"h", user_pw->pw_dir,
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"t", sshkey_ssh_name(key),
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"T", sshkey_ssh_name(cert->signature_key),
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"f", key_fp,
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"F", ca_fp,
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"k", keytext,
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"K", catext,
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"i", cert->key_id,
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"s", serial_s,
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(char *)NULL);
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if (tmp == NULL)
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fatal("%s: percent_expand failed", __func__);
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free(av[i]);
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av[i] = tmp;
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}
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/* Prepare a printable command for logs, etc. */
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command = argv_assemble(ac, av);
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if ((pid = subprocess("AuthorizedPrincipalsCommand", pw, command,
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ac, av, &f,
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SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
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goto out;
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uid_swapped = 1;
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temporarily_use_uid(pw);
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ok = process_principals(f, "(command)", pw, cert);
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fclose(f);
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f = NULL;
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if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0)
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goto out;
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/* Read completed successfully */
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found_principal = ok;
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out:
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if (f != NULL)
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fclose(f);
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signal(SIGCHLD, osigchld);
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for (i = 0; i < ac; i++)
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free(av[i]);
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free(av);
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if (uid_swapped)
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restore_uid();
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free(command);
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free(username);
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free(ca_fp);
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free(key_fp);
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free(catext);
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free(keytext);
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return found_principal;
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}
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/*
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* Checks whether key is allowed in authorized_keys-format file,
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* returns 1 if the key is allowed or 0 otherwise.
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*/
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static int
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check_authkeys_file(FILE *f, char *file, struct sshkey *key, struct passwd *pw)
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{
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char line[SSH_MAX_PUBKEY_BYTES];
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int found_key = 0;
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u_long linenum = 0;
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struct sshkey *found = NULL;
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|
|
while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
|
|
char *cp, *key_options = NULL, *fp = NULL;
|
|
const char *reason = NULL;
|
|
|
|
/* Always consume entire file */
|
|
if (found_key)
|
|
continue;
|
|
if (found != NULL)
|
|
sshkey_free(found);
|
|
found = sshkey_new(sshkey_is_cert(key) ? KEY_UNSPEC : key->type);
|
|
if (found == NULL)
|
|
goto done;
|
|
auth_clear_options();
|
|
|
|
/* Skip leading whitespace, empty and comment lines. */
|
|
for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
|
|
;
|
|
if (!*cp || *cp == '\n' || *cp == '#')
|
|
continue;
|
|
|
|
if (sshkey_read(found, &cp) != 0) {
|
|
/* no key? check if there are options for this key */
|
|
int quoted = 0;
|
|
debug2("user_key_allowed: check options: '%s'", cp);
|
|
key_options = cp;
|
|
for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
|
|
if (*cp == '\\' && cp[1] == '"')
|
|
cp++; /* Skip both */
|
|
else if (*cp == '"')
|
|
quoted = !quoted;
|
|
}
|
|
/* Skip remaining whitespace. */
|
|
for (; *cp == ' ' || *cp == '\t'; cp++)
|
|
;
|
|
if (sshkey_read(found, &cp) != 0) {
|
|
debug2("user_key_allowed: advance: '%s'", cp);
|
|
/* still no key? advance to next line*/
|
|
continue;
|
|
}
|
|
}
|
|
if (sshkey_is_cert(key)) {
|
|
if (!sshkey_equal(found, key->cert->signature_key))
|
|
continue;
|
|
if (auth_parse_options(pw, key_options, file,
|
|
linenum) != 1)
|
|
continue;
|
|
if (!key_is_cert_authority)
|
|
continue;
|
|
if ((fp = sshkey_fingerprint(found,
|
|
options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
|
|
continue;
|
|
debug("matching CA found: file %s, line %lu, %s %s",
|
|
file, linenum, sshkey_type(found), fp);
|
|
/*
|
|
* 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 (authorized_principals != NULL &&
|
|
!match_principals_option(authorized_principals,
|
|
key->cert)) {
|
|
reason = "Certificate does not contain an "
|
|
"authorized principal";
|
|
fail_reason:
|
|
free(fp);
|
|
error("%s", reason);
|
|
auth_debug_add("%s", reason);
|
|
continue;
|
|
}
|
|
if (sshkey_cert_check_authority(key, 0, 0,
|
|
authorized_principals == NULL ? pw->pw_name : NULL,
|
|
&reason) != 0)
|
|
goto fail_reason;
|
|
if (auth_cert_options(key, pw, &reason) != 0)
|
|
goto fail_reason;
|
|
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(found), fp, file);
|
|
free(fp);
|
|
found_key = 1;
|
|
break;
|
|
} else if (sshkey_equal(found, key)) {
|
|
if (auth_parse_options(pw, key_options, file,
|
|
linenum) != 1)
|
|
continue;
|
|
if (key_is_cert_authority)
|
|
continue;
|
|
if ((fp = sshkey_fingerprint(found,
|
|
options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
|
|
continue;
|
|
debug("matching key found: file %s, line %lu %s %s",
|
|
file, linenum, sshkey_type(found), fp);
|
|
free(fp);
|
|
found_key = 1;
|
|
continue;
|
|
}
|
|
}
|
|
done:
|
|
if (found != NULL)
|
|
sshkey_free(found);
|
|
if (!found_key)
|
|
debug2("key not found");
|
|
return found_key;
|
|
}
|
|
|
|
/* Authenticate a certificate key against TrustedUserCAKeys */
|
|
static int
|
|
user_cert_trusted_ca(struct passwd *pw, struct sshkey *key)
|
|
{
|
|
char *ca_fp, *principals_file = NULL;
|
|
const char *reason;
|
|
int r, ret = 0, found_principal = 0, use_authorized_principals;
|
|
|
|
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("%s: CA %s %s is not listed in %s: %s", __func__,
|
|
sshkey_type(key->cert->signature_key), ca_fp,
|
|
options.trusted_user_ca_keys, ssh_err(r));
|
|
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(principals_file, pw, key->cert))
|
|
found_principal = 1;
|
|
}
|
|
/* Try querying command if specified */
|
|
if (!found_principal && match_principals_command(pw, key))
|
|
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";
|
|
fail_reason:
|
|
error("%s", reason);
|
|
auth_debug_add("%s", reason);
|
|
goto out;
|
|
}
|
|
if (sshkey_cert_check_authority(key, 0, 1,
|
|
use_authorized_principals ? NULL : pw->pw_name, &reason) != 0)
|
|
goto fail_reason;
|
|
if (auth_cert_options(key, pw, &reason) != 0)
|
|
goto fail_reason;
|
|
|
|
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);
|
|
ret = 1;
|
|
|
|
out:
|
|
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 passwd *pw, struct sshkey *key, char *file)
|
|
{
|
|
FILE *f;
|
|
int found_key = 0;
|
|
|
|
/* 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(f, file, key, pw);
|
|
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 passwd *user_pw, struct sshkey *key)
|
|
{
|
|
FILE *f = NULL;
|
|
int r, ok, found_key = 0;
|
|
struct passwd *pw;
|
|
int i, uid_swapped = 0, ac = 0;
|
|
pid_t pid;
|
|
char *username = NULL, *key_fp = NULL, *keytext = NULL;
|
|
char *tmp, *command = NULL, **av = NULL;
|
|
void (*osigchld)(int);
|
|
|
|
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 = 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);
|
|
pw = getpwnam(username);
|
|
if (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("%s: sshkey_fingerprint failed", __func__);
|
|
goto out;
|
|
}
|
|
if ((r = sshkey_to_base64(key, &keytext)) != 0) {
|
|
error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
|
|
goto out;
|
|
}
|
|
|
|
/* Turn the command into an argument vector */
|
|
if (argv_split(options.authorized_keys_command, &ac, &av) != 0) {
|
|
error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
|
|
command);
|
|
goto out;
|
|
}
|
|
if (ac == 0) {
|
|
error("AuthorizedKeysCommand \"%s\" yielded no arguments",
|
|
command);
|
|
goto out;
|
|
}
|
|
for (i = 1; i < ac; i++) {
|
|
tmp = percent_expand(av[i],
|
|
"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("%s: percent_expand failed", __func__);
|
|
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", pw, command,
|
|
ac, av, &f,
|
|
SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
|
|
goto out;
|
|
|
|
uid_swapped = 1;
|
|
temporarily_use_uid(pw);
|
|
|
|
ok = check_authkeys_file(f, options.authorized_keys_command, key, pw);
|
|
|
|
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);
|
|
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 passwd *pw, struct sshkey *key, int auth_attempt)
|
|
{
|
|
u_int success, i;
|
|
char *file;
|
|
|
|
if (auth_key_is_revoked(key))
|
|
return 0;
|
|
if (sshkey_is_cert(key) &&
|
|
auth_key_is_revoked(key->cert->signature_key))
|
|
return 0;
|
|
|
|
success = user_cert_trusted_ca(pw, key);
|
|
if (success)
|
|
return success;
|
|
|
|
success = user_key_command_allowed2(pw, key);
|
|
if (success > 0)
|
|
return success;
|
|
|
|
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(pw, key, file);
|
|
free(file);
|
|
}
|
|
|
|
return success;
|
|
}
|
|
|
|
Authmethod method_pubkey = {
|
|
"publickey",
|
|
userauth_pubkey,
|
|
&options.pubkey_authentication
|
|
};
|