Release notes are available at https://www.openssh.com/txt/release-9.2 OpenSSH 9.2 contains fixes for two security problems and a memory safety problem. The memory safety problem is not believed to be exploitable. These fixes have already been committed to OpenSSH 9.1 in FreeBSD. Some other notable items from the release notes: * ssh(1): add a new EnableEscapeCommandline ssh_config(5) option that controls whether the client-side ~C escape sequence that provides a command-line is available. Among other things, the ~C command-line could be used to add additional port-forwards at runtime. * sshd(8): add support for channel inactivity timeouts via a new sshd_config(5) ChannelTimeout directive. This allows channels that have not seen traffic in a configurable interval to be automatically closed. Different timeouts may be applied to session, X11, agent and TCP forwarding channels. * sshd(8): add a sshd_config UnusedConnectionTimeout option to terminate client connections that have no open channels for a length of time. This complements the ChannelTimeout option above. * sshd(8): add a -V (version) option to sshd like the ssh client has. * scp(1), sftp(1): add a -X option to both scp(1) and sftp(1) to allow control over some SFTP protocol parameters: the copy buffer length and the number of in-flight requests, both of which are used during upload/download. Previously these could be controlled in sftp(1) only. This makes them available in both SFTP protocol clients using the same option character sequence. * ssh-keyscan(1): allow scanning of complete CIDR address ranges, e.g. "ssh-keyscan 192.168.0.0/24". If a CIDR range is passed, then it will be expanded to all possible addresses in the range including the all-0s and all-1s addresses. bz#976 * ssh(1): support dynamic remote port forwarding in escape command-line's -R processing. bz#3499 MFC after: 1 week Sponsored by: The FreeBSD Foundation
469 lines
14 KiB
C
469 lines
14 KiB
C
/* $OpenBSD: ssh-ecdsa-sk.c,v 1.17 2022/10/28 00:44:44 djm Exp $ */
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/*
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* Copyright (c) 2000 Markus Friedl. All rights reserved.
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* Copyright (c) 2010 Damien Miller. All rights reserved.
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* Copyright (c) 2019 Google Inc. 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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/* #define DEBUG_SK 1 */
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#include "includes.h"
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#include <sys/types.h>
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#ifdef WITH_OPENSSL
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#include <openssl/bn.h>
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#include <openssl/ec.h>
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#include <openssl/ecdsa.h>
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#include <openssl/evp.h>
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#endif
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#include <string.h>
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#include <stdio.h> /* needed for DEBUG_SK only */
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#include "openbsd-compat/openssl-compat.h"
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#include "sshbuf.h"
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#include "ssherr.h"
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#include "digest.h"
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#define SSHKEY_INTERNAL
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#include "sshkey.h"
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#ifndef OPENSSL_HAS_ECC
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/* ARGSUSED */
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int
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ssh_ecdsa_sk_verify(const struct sshkey *key,
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const u_char *signature, size_t signaturelen,
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const u_char *data, size_t datalen, u_int compat,
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struct sshkey_sig_details **detailsp)
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{
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return SSH_ERR_FEATURE_UNSUPPORTED;
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}
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#else /* OPENSSL_HAS_ECC */
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/* Reuse some ECDSA internals */
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extern struct sshkey_impl_funcs sshkey_ecdsa_funcs;
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static void
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ssh_ecdsa_sk_cleanup(struct sshkey *k)
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{
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sshkey_sk_cleanup(k);
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sshkey_ecdsa_funcs.cleanup(k);
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}
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static int
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ssh_ecdsa_sk_equal(const struct sshkey *a, const struct sshkey *b)
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{
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if (!sshkey_sk_fields_equal(a, b))
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return 0;
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if (!sshkey_ecdsa_funcs.equal(a, b))
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return 0;
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return 1;
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}
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static int
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ssh_ecdsa_sk_serialize_public(const struct sshkey *key, struct sshbuf *b,
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enum sshkey_serialize_rep opts)
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{
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int r;
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if ((r = sshkey_ecdsa_funcs.serialize_public(key, b, opts)) != 0)
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return r;
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if ((r = sshkey_serialize_sk(key, b)) != 0)
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return r;
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return 0;
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}
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static int
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ssh_ecdsa_sk_serialize_private(const struct sshkey *key, struct sshbuf *b,
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enum sshkey_serialize_rep opts)
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{
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int r;
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if (!sshkey_is_cert(key)) {
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if ((r = sshkey_ecdsa_funcs.serialize_public(key,
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b, opts)) != 0)
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return r;
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}
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if ((r = sshkey_serialize_private_sk(key, b)) != 0)
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return r;
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return 0;
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}
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static int
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ssh_ecdsa_sk_copy_public(const struct sshkey *from, struct sshkey *to)
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{
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int r;
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if ((r = sshkey_ecdsa_funcs.copy_public(from, to)) != 0)
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return r;
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if ((r = sshkey_copy_public_sk(from, to)) != 0)
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return r;
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return 0;
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}
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static int
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ssh_ecdsa_sk_deserialize_public(const char *ktype, struct sshbuf *b,
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struct sshkey *key)
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{
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int r;
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if ((r = sshkey_ecdsa_funcs.deserialize_public(ktype, b, key)) != 0)
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return r;
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if ((r = sshkey_deserialize_sk(b, key)) != 0)
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return r;
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return 0;
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}
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static int
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ssh_ecdsa_sk_deserialize_private(const char *ktype, struct sshbuf *b,
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struct sshkey *key)
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{
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int r;
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if (!sshkey_is_cert(key)) {
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if ((r = sshkey_ecdsa_funcs.deserialize_public(ktype,
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b, key)) != 0)
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return r;
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}
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if ((r = sshkey_private_deserialize_sk(b, key)) != 0)
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return r;
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return 0;
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}
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/*
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* Check FIDO/W3C webauthn signatures clientData field against the expected
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* format and prepare a hash of it for use in signature verification.
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*
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* webauthn signatures do not sign the hash of the message directly, but
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* instead sign a JSON-like "clientData" wrapper structure that contains the
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* message hash along with a other information.
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*
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* Fortunately this structure has a fixed format so it is possible to verify
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* that the hash of the signed message is present within the clientData
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* structure without needing to implement any JSON parsing.
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*/
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static int
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webauthn_check_prepare_hash(const u_char *data, size_t datalen,
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const char *origin, const struct sshbuf *wrapper,
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uint8_t flags, const struct sshbuf *extensions,
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u_char *msghash, size_t msghashlen)
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{
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int r = SSH_ERR_INTERNAL_ERROR;
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struct sshbuf *chall = NULL, *m = NULL;
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if ((m = sshbuf_new()) == NULL ||
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(chall = sshbuf_from(data, datalen)) == NULL) {
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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/*
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* Ensure origin contains no quote character and that the flags are
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* consistent with what we received
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*/
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if (strchr(origin, '\"') != NULL ||
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(flags & 0x40) != 0 /* AD */ ||
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((flags & 0x80) == 0 /* ED */) != (sshbuf_len(extensions) == 0)) {
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r = SSH_ERR_INVALID_FORMAT;
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goto out;
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}
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/*
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* Prepare the preamble to clientData that we expect, poking the
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* challenge and origin into their canonical positions in the
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* structure. The crossOrigin flag and any additional extension
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* fields present are ignored.
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*/
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#define WEBAUTHN_0 "{\"type\":\"webauthn.get\",\"challenge\":\""
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#define WEBAUTHN_1 "\",\"origin\":\""
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#define WEBAUTHN_2 "\""
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if ((r = sshbuf_put(m, WEBAUTHN_0, sizeof(WEBAUTHN_0) - 1)) != 0 ||
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(r = sshbuf_dtourlb64(chall, m, 0)) != 0 ||
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(r = sshbuf_put(m, WEBAUTHN_1, sizeof(WEBAUTHN_1) - 1)) != 0 ||
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(r = sshbuf_put(m, origin, strlen(origin))) != 0 ||
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(r = sshbuf_put(m, WEBAUTHN_2, sizeof(WEBAUTHN_2) - 1)) != 0)
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goto out;
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#ifdef DEBUG_SK
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fprintf(stderr, "%s: received origin: %s\n", __func__, origin);
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fprintf(stderr, "%s: received clientData:\n", __func__);
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sshbuf_dump(wrapper, stderr);
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fprintf(stderr, "%s: expected clientData premable:\n", __func__);
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sshbuf_dump(m, stderr);
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#endif
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/* Check that the supplied clientData has the preamble we expect */
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if ((r = sshbuf_cmp(wrapper, 0, sshbuf_ptr(m), sshbuf_len(m))) != 0)
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goto out;
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/* Prepare hash of clientData */
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if ((r = ssh_digest_buffer(SSH_DIGEST_SHA256, wrapper,
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msghash, msghashlen)) != 0)
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goto out;
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/* success */
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r = 0;
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out:
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sshbuf_free(chall);
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sshbuf_free(m);
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return r;
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}
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/* ARGSUSED */
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static int
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ssh_ecdsa_sk_verify(const struct sshkey *key,
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const u_char *sig, size_t siglen,
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const u_char *data, size_t dlen, const char *alg, u_int compat,
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struct sshkey_sig_details **detailsp)
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{
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ECDSA_SIG *esig = NULL;
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BIGNUM *sig_r = NULL, *sig_s = NULL;
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u_char sig_flags;
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u_char msghash[32], apphash[32], sighash[32];
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u_int sig_counter;
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int is_webauthn = 0, ret = SSH_ERR_INTERNAL_ERROR;
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struct sshbuf *b = NULL, *sigbuf = NULL, *original_signed = NULL;
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struct sshbuf *webauthn_wrapper = NULL, *webauthn_exts = NULL;
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char *ktype = NULL, *webauthn_origin = NULL;
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struct sshkey_sig_details *details = NULL;
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#ifdef DEBUG_SK
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char *tmp = NULL;
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#endif
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if (detailsp != NULL)
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*detailsp = NULL;
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if (key == NULL || key->ecdsa == NULL ||
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sshkey_type_plain(key->type) != KEY_ECDSA_SK ||
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sig == NULL || siglen == 0)
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return SSH_ERR_INVALID_ARGUMENT;
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if (key->ecdsa_nid != NID_X9_62_prime256v1)
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return SSH_ERR_INTERNAL_ERROR;
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/* fetch signature */
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if ((b = sshbuf_from(sig, siglen)) == NULL)
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return SSH_ERR_ALLOC_FAIL;
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if ((details = calloc(1, sizeof(*details))) == NULL) {
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ret = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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if (sshbuf_get_cstring(b, &ktype, NULL) != 0) {
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ret = SSH_ERR_INVALID_FORMAT;
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goto out;
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}
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if (strcmp(ktype, "webauthn-sk-ecdsa-sha2-nistp256@openssh.com") == 0)
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is_webauthn = 1;
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else if (strcmp(ktype, "sk-ecdsa-sha2-nistp256@openssh.com") != 0) {
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ret = SSH_ERR_INVALID_FORMAT;
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goto out;
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}
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if (sshbuf_froms(b, &sigbuf) != 0 ||
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sshbuf_get_u8(b, &sig_flags) != 0 ||
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sshbuf_get_u32(b, &sig_counter) != 0) {
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ret = SSH_ERR_INVALID_FORMAT;
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goto out;
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}
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if (is_webauthn) {
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if (sshbuf_get_cstring(b, &webauthn_origin, NULL) != 0 ||
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sshbuf_froms(b, &webauthn_wrapper) != 0 ||
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sshbuf_froms(b, &webauthn_exts) != 0) {
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ret = SSH_ERR_INVALID_FORMAT;
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goto out;
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}
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}
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if (sshbuf_len(b) != 0) {
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ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
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goto out;
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}
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/* parse signature */
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if (sshbuf_get_bignum2(sigbuf, &sig_r) != 0 ||
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sshbuf_get_bignum2(sigbuf, &sig_s) != 0) {
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ret = SSH_ERR_INVALID_FORMAT;
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goto out;
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}
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if (sshbuf_len(sigbuf) != 0) {
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ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
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goto out;
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}
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#ifdef DEBUG_SK
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fprintf(stderr, "%s: data: (len %zu)\n", __func__, datalen);
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/* sshbuf_dump_data(data, datalen, stderr); */
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fprintf(stderr, "%s: sig_r: %s\n", __func__, (tmp = BN_bn2hex(sig_r)));
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free(tmp);
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fprintf(stderr, "%s: sig_s: %s\n", __func__, (tmp = BN_bn2hex(sig_s)));
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free(tmp);
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fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n",
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__func__, sig_flags, sig_counter);
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if (is_webauthn) {
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fprintf(stderr, "%s: webauthn origin: %s\n", __func__,
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webauthn_origin);
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fprintf(stderr, "%s: webauthn_wrapper:\n", __func__);
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sshbuf_dump(webauthn_wrapper, stderr);
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}
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#endif
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if ((esig = ECDSA_SIG_new()) == NULL) {
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ret = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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if (!ECDSA_SIG_set0(esig, sig_r, sig_s)) {
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ret = SSH_ERR_LIBCRYPTO_ERROR;
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goto out;
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}
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sig_r = sig_s = NULL; /* transferred */
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/* Reconstruct data that was supposedly signed */
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if ((original_signed = sshbuf_new()) == NULL) {
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ret = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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if (is_webauthn) {
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if ((ret = webauthn_check_prepare_hash(data, dlen,
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webauthn_origin, webauthn_wrapper, sig_flags, webauthn_exts,
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msghash, sizeof(msghash))) != 0)
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goto out;
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} else if ((ret = ssh_digest_memory(SSH_DIGEST_SHA256, data, dlen,
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msghash, sizeof(msghash))) != 0)
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goto out;
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/* Application value is hashed before signature */
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if ((ret = ssh_digest_memory(SSH_DIGEST_SHA256, key->sk_application,
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strlen(key->sk_application), apphash, sizeof(apphash))) != 0)
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goto out;
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#ifdef DEBUG_SK
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fprintf(stderr, "%s: hashed application:\n", __func__);
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sshbuf_dump_data(apphash, sizeof(apphash), stderr);
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fprintf(stderr, "%s: hashed message:\n", __func__);
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sshbuf_dump_data(msghash, sizeof(msghash), stderr);
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#endif
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if ((ret = sshbuf_put(original_signed,
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apphash, sizeof(apphash))) != 0 ||
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(ret = sshbuf_put_u8(original_signed, sig_flags)) != 0 ||
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(ret = sshbuf_put_u32(original_signed, sig_counter)) != 0 ||
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(ret = sshbuf_putb(original_signed, webauthn_exts)) != 0 ||
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(ret = sshbuf_put(original_signed, msghash, sizeof(msghash))) != 0)
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goto out;
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/* Signature is over H(original_signed) */
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if ((ret = ssh_digest_buffer(SSH_DIGEST_SHA256, original_signed,
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sighash, sizeof(sighash))) != 0)
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goto out;
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details->sk_counter = sig_counter;
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details->sk_flags = sig_flags;
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#ifdef DEBUG_SK
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fprintf(stderr, "%s: signed buf:\n", __func__);
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sshbuf_dump(original_signed, stderr);
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fprintf(stderr, "%s: signed hash:\n", __func__);
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sshbuf_dump_data(sighash, sizeof(sighash), stderr);
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#endif
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/* Verify it */
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switch (ECDSA_do_verify(sighash, sizeof(sighash), esig, key->ecdsa)) {
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case 1:
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ret = 0;
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break;
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case 0:
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ret = SSH_ERR_SIGNATURE_INVALID;
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goto out;
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default:
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ret = SSH_ERR_LIBCRYPTO_ERROR;
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goto out;
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}
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/* success */
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if (detailsp != NULL) {
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*detailsp = details;
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details = NULL;
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}
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out:
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explicit_bzero(&sig_flags, sizeof(sig_flags));
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explicit_bzero(&sig_counter, sizeof(sig_counter));
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explicit_bzero(msghash, sizeof(msghash));
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explicit_bzero(sighash, sizeof(msghash));
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explicit_bzero(apphash, sizeof(apphash));
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sshkey_sig_details_free(details);
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sshbuf_free(webauthn_wrapper);
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sshbuf_free(webauthn_exts);
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free(webauthn_origin);
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sshbuf_free(original_signed);
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sshbuf_free(sigbuf);
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sshbuf_free(b);
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ECDSA_SIG_free(esig);
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BN_clear_free(sig_r);
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BN_clear_free(sig_s);
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free(ktype);
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return ret;
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}
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|
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static const struct sshkey_impl_funcs sshkey_ecdsa_sk_funcs = {
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/* .size = */ NULL,
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/* .alloc = */ NULL,
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/* .cleanup = */ ssh_ecdsa_sk_cleanup,
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/* .equal = */ ssh_ecdsa_sk_equal,
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/* .ssh_serialize_public = */ ssh_ecdsa_sk_serialize_public,
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/* .ssh_deserialize_public = */ ssh_ecdsa_sk_deserialize_public,
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|
/* .ssh_serialize_private = */ ssh_ecdsa_sk_serialize_private,
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/* .ssh_deserialize_private = */ ssh_ecdsa_sk_deserialize_private,
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/* .generate = */ NULL,
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|
/* .copy_public = */ ssh_ecdsa_sk_copy_public,
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/* .sign = */ NULL,
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/* .verify = */ ssh_ecdsa_sk_verify,
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};
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|
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const struct sshkey_impl sshkey_ecdsa_sk_impl = {
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/* .name = */ "sk-ecdsa-sha2-nistp256@openssh.com",
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/* .shortname = */ "ECDSA-SK",
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/* .sigalg = */ NULL,
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/* .type = */ KEY_ECDSA_SK,
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/* .nid = */ NID_X9_62_prime256v1,
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/* .cert = */ 0,
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/* .sigonly = */ 0,
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|
/* .keybits = */ 256,
|
|
/* .funcs = */ &sshkey_ecdsa_sk_funcs,
|
|
};
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|
|
|
const struct sshkey_impl sshkey_ecdsa_sk_cert_impl = {
|
|
/* .name = */ "sk-ecdsa-sha2-nistp256-cert-v01@openssh.com",
|
|
/* .shortname = */ "ECDSA-SK-CERT",
|
|
/* .sigalg = */ NULL,
|
|
/* .type = */ KEY_ECDSA_SK_CERT,
|
|
/* .nid = */ NID_X9_62_prime256v1,
|
|
/* .cert = */ 1,
|
|
/* .sigonly = */ 0,
|
|
/* .keybits = */ 256,
|
|
/* .funcs = */ &sshkey_ecdsa_sk_funcs,
|
|
};
|
|
|
|
const struct sshkey_impl sshkey_ecdsa_sk_webauthn_impl = {
|
|
/* .name = */ "webauthn-sk-ecdsa-sha2-nistp256@openssh.com",
|
|
/* .shortname = */ "ECDSA-SK",
|
|
/* .sigalg = */ NULL,
|
|
/* .type = */ KEY_ECDSA_SK,
|
|
/* .nid = */ NID_X9_62_prime256v1,
|
|
/* .cert = */ 0,
|
|
/* .sigonly = */ 1,
|
|
/* .keybits = */ 256,
|
|
/* .funcs = */ &sshkey_ecdsa_sk_funcs,
|
|
};
|
|
|
|
#endif /* OPENSSL_HAS_ECC */
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