diff options
author | djm@openbsd.org <djm@openbsd.org> | 2019-10-31 21:15:14 +0000 |
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committer | Damien Miller <djm@mindrot.org> | 2019-11-01 09:46:08 +1100 |
commit | 02bb0768a937e50bbb236efc2bbdddb1991b1c85 (patch) | |
tree | d0a182540b8034345b20a49a09cbf90b234cad1c /ssh-ecdsa-sk.c | |
parent | 57ecc10628b04c384cbba2fbc87d38b74cd1199d (diff) | |
download | openssh-git-02bb0768a937e50bbb236efc2bbdddb1991b1c85.tar.gz |
upstream: Initial infrastructure for U2F/FIDO support
Key library support: including allocation, marshalling public/private
keys and certificates, signature validation.
feedback & ok markus@
OpenBSD-Commit-ID: a17615ba15e0f7932ac4360cb18fc9a9544e68c7
Diffstat (limited to 'ssh-ecdsa-sk.c')
-rw-r--r-- | ssh-ecdsa-sk.c | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/ssh-ecdsa-sk.c b/ssh-ecdsa-sk.c new file mode 100644 index 00000000..6441cd7f --- /dev/null +++ b/ssh-ecdsa-sk.c @@ -0,0 +1,180 @@ +/* $OpenBSD: ssh-ecdsa-sk.c,v 1.1 2019/10/31 21:15:14 djm Exp $ */ +/* + * Copyright (c) 2000 Markus Friedl. All rights reserved. + * Copyright (c) 2010 Damien Miller. All rights reserved. + * Copyright (c) 2019 Google Inc. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +/* #define DEBUG_SK 1 */ + +#include "includes.h" + +#include <sys/types.h> + +#include <openssl/bn.h> +#include <openssl/ec.h> +#include <openssl/ecdsa.h> +#include <openssl/evp.h> + +#include <string.h> +#include <stdio.h> /* needed for DEBUG_SK only */ + +#include "sshbuf.h" +#include "ssherr.h" +#include "digest.h" +#define SSHKEY_INTERNAL +#include "sshkey.h" + +/* ARGSUSED */ +int +ssh_ecdsa_sk_verify(const struct sshkey *key, + const u_char *signature, size_t signaturelen, + const u_char *data, size_t datalen, u_int compat) +{ + ECDSA_SIG *sig = NULL; + BIGNUM *sig_r = NULL, *sig_s = NULL; + u_char sig_flags; + u_char msghash[32], apphash[32], sighash[32]; + u_int sig_counter; + int ret = SSH_ERR_INTERNAL_ERROR; + struct sshbuf *b = NULL, *sigbuf = NULL, *original_signed = NULL; + char *ktype = NULL; +#ifdef DEBUG_SK + char *tmp = NULL; +#endif + + if (key == NULL || key->ecdsa == NULL || + sshkey_type_plain(key->type) != KEY_ECDSA_SK || + signature == NULL || signaturelen == 0) + return SSH_ERR_INVALID_ARGUMENT; + + if (key->ecdsa_nid != NID_X9_62_prime256v1) + return SSH_ERR_INTERNAL_ERROR; + + /* fetch signature */ + if ((b = sshbuf_from(signature, signaturelen)) == NULL) + return SSH_ERR_ALLOC_FAIL; + if (sshbuf_get_cstring(b, &ktype, NULL) != 0 || + sshbuf_froms(b, &sigbuf) != 0) { + ret = SSH_ERR_INVALID_FORMAT; + goto out; + } + if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) { + ret = SSH_ERR_KEY_TYPE_MISMATCH; + goto out; + } + if (sshbuf_len(b) != 0) { + ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; + goto out; + } + + /* parse signature */ + if (sshbuf_get_bignum2(sigbuf, &sig_r) != 0 || + sshbuf_get_bignum2(sigbuf, &sig_s) != 0 || + sshbuf_get_u8(sigbuf, &sig_flags) != 0 || + sshbuf_get_u32(sigbuf, &sig_counter) != 0) { + ret = SSH_ERR_INVALID_FORMAT; + goto out; + } + if ((sig = ECDSA_SIG_new()) == NULL) { + ret = SSH_ERR_ALLOC_FAIL; + goto out; + } + if (!ECDSA_SIG_set0(sig, sig_r, sig_s)) { + ret = SSH_ERR_LIBCRYPTO_ERROR; + goto out; + } +#ifdef DEBUG_SK + fprintf(stderr, "%s: sig_r: %s\n", __func__, (tmp = BN_bn2hex(sig_r))); + free(tmp); + fprintf(stderr, "%s: sig_s: %s\n", __func__, (tmp = BN_bn2hex(sig_s))); + free(tmp); + fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n", + __func__, sig_flags, sig_counter); +#endif + sig_r = sig_s = NULL; /* transferred */ + + if (sshbuf_len(sigbuf) != 0) { + ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; + goto out; + } + + /* Reconstruct data that was supposedly signed */ + if ((original_signed = sshbuf_new()) == NULL) + return SSH_ERR_ALLOC_FAIL; + if ((ret = ssh_digest_memory(SSH_DIGEST_SHA256, data, datalen, + msghash, sizeof(msghash))) != 0) + goto out; + /* Application value is hashed before signature */ + if ((ret = ssh_digest_memory(SSH_DIGEST_SHA256, key->sk_application, + strlen(key->sk_application), apphash, sizeof(apphash))) != 0) + goto out; +#ifdef DEBUG_SK + fprintf(stderr, "%s: hashed message:\n", __func__); + sshbuf_dump_data(msghash, sizeof(msghash), stderr); +#endif + if ((ret = sshbuf_put(original_signed, + apphash, sizeof(apphash))) != 0 || + (ret = sshbuf_put_u8(original_signed, sig_flags)) != 0 || + (ret = sshbuf_put_u32(original_signed, sig_counter)) != 0 || + (ret = sshbuf_put(original_signed, msghash, sizeof(msghash))) != 0) + goto out; + /* Signature is over H(original_signed) */ + if ((ret = ssh_digest_buffer(SSH_DIGEST_SHA256, original_signed, + sighash, sizeof(sighash))) != 0) + goto out; +#ifdef DEBUG_SK + fprintf(stderr, "%s: signed buf:\n", __func__); + sshbuf_dump(original_signed, stderr); + fprintf(stderr, "%s: signed hash:\n", __func__); + sshbuf_dump_data(sighash, sizeof(sighash), stderr); +#endif + + /* Verify it */ + switch (ECDSA_do_verify(sighash, sizeof(sighash), sig, key->ecdsa)) { + case 1: + ret = 0; + break; + case 0: + ret = SSH_ERR_SIGNATURE_INVALID; + goto out; + default: + ret = SSH_ERR_LIBCRYPTO_ERROR; + goto out; + } + + out: + explicit_bzero(&sig_flags, sizeof(sig_flags)); + explicit_bzero(&sig_counter, sizeof(sig_counter)); + explicit_bzero(msghash, sizeof(msghash)); + explicit_bzero(sighash, sizeof(msghash)); + explicit_bzero(apphash, sizeof(apphash)); + sshbuf_free(original_signed); + sshbuf_free(sigbuf); + sshbuf_free(b); + ECDSA_SIG_free(sig); + BN_clear_free(sig_r); + BN_clear_free(sig_s); + free(ktype); + return ret; +} |