djm@openbsd.org | e0d38ae | 2019-11-26 03:04:27 +0000 | [diff] [blame] | 1 | /* $OpenBSD: ssh-ecdsa-sk.c,v 1.5 2019/11/26 03:04:27 djm Exp $ */ |
djm@openbsd.org | 02bb076 | 2019-10-31 21:15:14 +0000 | [diff] [blame] | 2 | /* |
| 3 | * Copyright (c) 2000 Markus Friedl. All rights reserved. |
| 4 | * Copyright (c) 2010 Damien Miller. All rights reserved. |
| 5 | * Copyright (c) 2019 Google Inc. All rights reserved. |
| 6 | * |
| 7 | * Redistribution and use in source and binary forms, with or without |
| 8 | * modification, are permitted provided that the following conditions |
| 9 | * are met: |
| 10 | * 1. Redistributions of source code must retain the above copyright |
| 11 | * notice, this list of conditions and the following disclaimer. |
| 12 | * 2. Redistributions in binary form must reproduce the above copyright |
| 13 | * notice, this list of conditions and the following disclaimer in the |
| 14 | * documentation and/or other materials provided with the distribution. |
| 15 | * |
| 16 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| 17 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| 18 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| 19 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| 20 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| 21 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 22 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 23 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 24 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| 25 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 26 | */ |
| 27 | |
| 28 | /* #define DEBUG_SK 1 */ |
| 29 | |
| 30 | #include "includes.h" |
| 31 | |
Damien Miller | 764d51e | 2019-11-01 13:34:49 +1100 | [diff] [blame] | 32 | #ifdef ENABLE_SK |
| 33 | |
djm@openbsd.org | 02bb076 | 2019-10-31 21:15:14 +0000 | [diff] [blame] | 34 | #include <sys/types.h> |
| 35 | |
| 36 | #include <openssl/bn.h> |
| 37 | #include <openssl/ec.h> |
| 38 | #include <openssl/ecdsa.h> |
| 39 | #include <openssl/evp.h> |
| 40 | |
| 41 | #include <string.h> |
| 42 | #include <stdio.h> /* needed for DEBUG_SK only */ |
| 43 | |
Darren Tucker | 2f95d43 | 2019-11-20 16:34:11 +1100 | [diff] [blame] | 44 | #include "openbsd-compat/openssl-compat.h" |
| 45 | |
djm@openbsd.org | 02bb076 | 2019-10-31 21:15:14 +0000 | [diff] [blame] | 46 | #include "sshbuf.h" |
| 47 | #include "ssherr.h" |
| 48 | #include "digest.h" |
| 49 | #define SSHKEY_INTERNAL |
| 50 | #include "sshkey.h" |
| 51 | |
| 52 | /* ARGSUSED */ |
| 53 | int |
| 54 | ssh_ecdsa_sk_verify(const struct sshkey *key, |
| 55 | const u_char *signature, size_t signaturelen, |
djm@openbsd.org | b7e74ea | 2019-11-25 00:51:37 +0000 | [diff] [blame] | 56 | const u_char *data, size_t datalen, u_int compat, |
| 57 | struct sshkey_sig_details **detailsp) |
djm@openbsd.org | 02bb076 | 2019-10-31 21:15:14 +0000 | [diff] [blame] | 58 | { |
| 59 | ECDSA_SIG *sig = NULL; |
| 60 | BIGNUM *sig_r = NULL, *sig_s = NULL; |
| 61 | u_char sig_flags; |
| 62 | u_char msghash[32], apphash[32], sighash[32]; |
| 63 | u_int sig_counter; |
| 64 | int ret = SSH_ERR_INTERNAL_ERROR; |
| 65 | struct sshbuf *b = NULL, *sigbuf = NULL, *original_signed = NULL; |
| 66 | char *ktype = NULL; |
djm@openbsd.org | b7e74ea | 2019-11-25 00:51:37 +0000 | [diff] [blame] | 67 | struct sshkey_sig_details *details = NULL; |
djm@openbsd.org | 02bb076 | 2019-10-31 21:15:14 +0000 | [diff] [blame] | 68 | #ifdef DEBUG_SK |
| 69 | char *tmp = NULL; |
| 70 | #endif |
| 71 | |
djm@openbsd.org | b7e74ea | 2019-11-25 00:51:37 +0000 | [diff] [blame] | 72 | if (detailsp != NULL) |
| 73 | *detailsp = NULL; |
djm@openbsd.org | 02bb076 | 2019-10-31 21:15:14 +0000 | [diff] [blame] | 74 | if (key == NULL || key->ecdsa == NULL || |
| 75 | sshkey_type_plain(key->type) != KEY_ECDSA_SK || |
| 76 | signature == NULL || signaturelen == 0) |
| 77 | return SSH_ERR_INVALID_ARGUMENT; |
| 78 | |
| 79 | if (key->ecdsa_nid != NID_X9_62_prime256v1) |
| 80 | return SSH_ERR_INTERNAL_ERROR; |
| 81 | |
| 82 | /* fetch signature */ |
| 83 | if ((b = sshbuf_from(signature, signaturelen)) == NULL) |
| 84 | return SSH_ERR_ALLOC_FAIL; |
| 85 | if (sshbuf_get_cstring(b, &ktype, NULL) != 0 || |
djm@openbsd.org | a70d92f | 2019-11-19 22:23:19 +0000 | [diff] [blame] | 86 | sshbuf_froms(b, &sigbuf) != 0 || |
| 87 | sshbuf_get_u8(b, &sig_flags) != 0 || |
| 88 | sshbuf_get_u32(b, &sig_counter) != 0) { |
djm@openbsd.org | 02bb076 | 2019-10-31 21:15:14 +0000 | [diff] [blame] | 89 | ret = SSH_ERR_INVALID_FORMAT; |
| 90 | goto out; |
| 91 | } |
| 92 | if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) { |
| 93 | ret = SSH_ERR_KEY_TYPE_MISMATCH; |
| 94 | goto out; |
| 95 | } |
| 96 | if (sshbuf_len(b) != 0) { |
| 97 | ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; |
| 98 | goto out; |
| 99 | } |
| 100 | |
| 101 | /* parse signature */ |
| 102 | if (sshbuf_get_bignum2(sigbuf, &sig_r) != 0 || |
djm@openbsd.org | a70d92f | 2019-11-19 22:23:19 +0000 | [diff] [blame] | 103 | sshbuf_get_bignum2(sigbuf, &sig_s) != 0) { |
djm@openbsd.org | 02bb076 | 2019-10-31 21:15:14 +0000 | [diff] [blame] | 104 | ret = SSH_ERR_INVALID_FORMAT; |
| 105 | goto out; |
| 106 | } |
| 107 | if ((sig = ECDSA_SIG_new()) == NULL) { |
| 108 | ret = SSH_ERR_ALLOC_FAIL; |
| 109 | goto out; |
| 110 | } |
| 111 | if (!ECDSA_SIG_set0(sig, sig_r, sig_s)) { |
| 112 | ret = SSH_ERR_LIBCRYPTO_ERROR; |
| 113 | goto out; |
| 114 | } |
| 115 | #ifdef DEBUG_SK |
djm@openbsd.org | e0d38ae | 2019-11-26 03:04:27 +0000 | [diff] [blame] | 116 | fprintf(stderr, "%s: data: (len %zu)\n", __func__, datalen); |
| 117 | /* sshbuf_dump_data(data, datalen, stderr); */ |
djm@openbsd.org | 02bb076 | 2019-10-31 21:15:14 +0000 | [diff] [blame] | 118 | fprintf(stderr, "%s: sig_r: %s\n", __func__, (tmp = BN_bn2hex(sig_r))); |
| 119 | free(tmp); |
| 120 | fprintf(stderr, "%s: sig_s: %s\n", __func__, (tmp = BN_bn2hex(sig_s))); |
| 121 | free(tmp); |
| 122 | fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n", |
| 123 | __func__, sig_flags, sig_counter); |
| 124 | #endif |
| 125 | sig_r = sig_s = NULL; /* transferred */ |
| 126 | |
| 127 | if (sshbuf_len(sigbuf) != 0) { |
| 128 | ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; |
| 129 | goto out; |
| 130 | } |
| 131 | |
| 132 | /* Reconstruct data that was supposedly signed */ |
djm@openbsd.org | d2b0f88 | 2019-11-25 00:38:17 +0000 | [diff] [blame] | 133 | if ((original_signed = sshbuf_new()) == NULL) { |
| 134 | ret = SSH_ERR_ALLOC_FAIL; |
| 135 | goto out; |
| 136 | } |
djm@openbsd.org | 02bb076 | 2019-10-31 21:15:14 +0000 | [diff] [blame] | 137 | if ((ret = ssh_digest_memory(SSH_DIGEST_SHA256, data, datalen, |
| 138 | msghash, sizeof(msghash))) != 0) |
| 139 | goto out; |
| 140 | /* Application value is hashed before signature */ |
| 141 | if ((ret = ssh_digest_memory(SSH_DIGEST_SHA256, key->sk_application, |
| 142 | strlen(key->sk_application), apphash, sizeof(apphash))) != 0) |
| 143 | goto out; |
| 144 | #ifdef DEBUG_SK |
djm@openbsd.org | e0d38ae | 2019-11-26 03:04:27 +0000 | [diff] [blame] | 145 | fprintf(stderr, "%s: hashed application:\n", __func__); |
| 146 | sshbuf_dump_data(apphash, sizeof(apphash), stderr); |
djm@openbsd.org | 02bb076 | 2019-10-31 21:15:14 +0000 | [diff] [blame] | 147 | fprintf(stderr, "%s: hashed message:\n", __func__); |
| 148 | sshbuf_dump_data(msghash, sizeof(msghash), stderr); |
| 149 | #endif |
| 150 | if ((ret = sshbuf_put(original_signed, |
| 151 | apphash, sizeof(apphash))) != 0 || |
| 152 | (ret = sshbuf_put_u8(original_signed, sig_flags)) != 0 || |
| 153 | (ret = sshbuf_put_u32(original_signed, sig_counter)) != 0 || |
| 154 | (ret = sshbuf_put(original_signed, msghash, sizeof(msghash))) != 0) |
| 155 | goto out; |
| 156 | /* Signature is over H(original_signed) */ |
| 157 | if ((ret = ssh_digest_buffer(SSH_DIGEST_SHA256, original_signed, |
| 158 | sighash, sizeof(sighash))) != 0) |
| 159 | goto out; |
djm@openbsd.org | b7e74ea | 2019-11-25 00:51:37 +0000 | [diff] [blame] | 160 | if ((details = calloc(1, sizeof(*details))) == NULL) { |
| 161 | ret = SSH_ERR_ALLOC_FAIL; |
| 162 | goto out; |
| 163 | } |
| 164 | details->sk_counter = sig_counter; |
| 165 | details->sk_flags = sig_flags; |
djm@openbsd.org | 02bb076 | 2019-10-31 21:15:14 +0000 | [diff] [blame] | 166 | #ifdef DEBUG_SK |
| 167 | fprintf(stderr, "%s: signed buf:\n", __func__); |
| 168 | sshbuf_dump(original_signed, stderr); |
| 169 | fprintf(stderr, "%s: signed hash:\n", __func__); |
| 170 | sshbuf_dump_data(sighash, sizeof(sighash), stderr); |
| 171 | #endif |
| 172 | |
| 173 | /* Verify it */ |
| 174 | switch (ECDSA_do_verify(sighash, sizeof(sighash), sig, key->ecdsa)) { |
| 175 | case 1: |
| 176 | ret = 0; |
| 177 | break; |
| 178 | case 0: |
| 179 | ret = SSH_ERR_SIGNATURE_INVALID; |
| 180 | goto out; |
| 181 | default: |
| 182 | ret = SSH_ERR_LIBCRYPTO_ERROR; |
| 183 | goto out; |
| 184 | } |
djm@openbsd.org | b7e74ea | 2019-11-25 00:51:37 +0000 | [diff] [blame] | 185 | /* success */ |
| 186 | if (detailsp != NULL) { |
| 187 | *detailsp = details; |
| 188 | details = NULL; |
| 189 | } |
djm@openbsd.org | 02bb076 | 2019-10-31 21:15:14 +0000 | [diff] [blame] | 190 | out: |
| 191 | explicit_bzero(&sig_flags, sizeof(sig_flags)); |
| 192 | explicit_bzero(&sig_counter, sizeof(sig_counter)); |
| 193 | explicit_bzero(msghash, sizeof(msghash)); |
| 194 | explicit_bzero(sighash, sizeof(msghash)); |
| 195 | explicit_bzero(apphash, sizeof(apphash)); |
djm@openbsd.org | b7e74ea | 2019-11-25 00:51:37 +0000 | [diff] [blame] | 196 | sshkey_sig_details_free(details); |
djm@openbsd.org | 02bb076 | 2019-10-31 21:15:14 +0000 | [diff] [blame] | 197 | sshbuf_free(original_signed); |
| 198 | sshbuf_free(sigbuf); |
| 199 | sshbuf_free(b); |
| 200 | ECDSA_SIG_free(sig); |
| 201 | BN_clear_free(sig_r); |
| 202 | BN_clear_free(sig_s); |
| 203 | free(ktype); |
| 204 | return ret; |
| 205 | } |
Damien Miller | 764d51e | 2019-11-01 13:34:49 +1100 | [diff] [blame] | 206 | #endif /* ENABLE_SK */ |