1 /* $NetBSD: ssh-ecdsa.c,v 1.14 2019/04/20 17:16:40 christos Exp $ */ 2 /* $OpenBSD: ssh-ecdsa.c,v 1.16 2019/01/21 09:54:11 djm Exp $ */ 3 /* 4 * Copyright (c) 2000 Markus Friedl. All rights reserved. 5 * Copyright (c) 2010 Damien Miller. 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 #include "includes.h" 29 __RCSID("$NetBSD: ssh-ecdsa.c,v 1.14 2019/04/20 17:16:40 christos Exp $"); 30 #include <sys/types.h> 31 32 #include <openssl/bn.h> 33 #include <openssl/ec.h> 34 #include <openssl/ecdsa.h> 35 #include <openssl/evp.h> 36 37 #include <string.h> 38 39 #include "sshbuf.h" 40 #include "ssherr.h" 41 #include "digest.h" 42 #define SSHKEY_INTERNAL 43 #include "sshkey.h" 44 45 /* ARGSUSED */ 46 int 47 ssh_ecdsa_sign(const struct sshkey *key, u_char **sigp, size_t *lenp, 48 const u_char *data, size_t datalen, u_int compat) 49 { 50 ECDSA_SIG *sig = NULL; 51 const BIGNUM *sig_r, *sig_s; 52 int hash_alg; 53 u_char digest[SSH_DIGEST_MAX_LENGTH]; 54 size_t len, dlen; 55 struct sshbuf *b = NULL, *bb = NULL; 56 int ret = SSH_ERR_INTERNAL_ERROR; 57 58 if (lenp != NULL) 59 *lenp = 0; 60 if (sigp != NULL) 61 *sigp = NULL; 62 63 if (key == NULL || key->ecdsa == NULL || 64 sshkey_type_plain(key->type) != KEY_ECDSA) 65 return SSH_ERR_INVALID_ARGUMENT; 66 67 if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 || 68 (dlen = ssh_digest_bytes(hash_alg)) == 0) 69 return SSH_ERR_INTERNAL_ERROR; 70 if ((ret = ssh_digest_memory(hash_alg, data, datalen, 71 digest, sizeof(digest))) != 0) 72 goto out; 73 74 if ((sig = ECDSA_do_sign(digest, dlen, key->ecdsa)) == NULL) { 75 ret = SSH_ERR_LIBCRYPTO_ERROR; 76 goto out; 77 } 78 79 if ((bb = sshbuf_new()) == NULL || (b = sshbuf_new()) == NULL) { 80 ret = SSH_ERR_ALLOC_FAIL; 81 goto out; 82 } 83 ECDSA_SIG_get0(sig, &sig_r, &sig_s); 84 if ((ret = sshbuf_put_bignum2(bb, sig_r)) != 0 || 85 (ret = sshbuf_put_bignum2(bb, sig_s)) != 0) 86 goto out; 87 if ((ret = sshbuf_put_cstring(b, sshkey_ssh_name_plain(key))) != 0 || 88 (ret = sshbuf_put_stringb(b, bb)) != 0) 89 goto out; 90 len = sshbuf_len(b); 91 if (sigp != NULL) { 92 if ((*sigp = malloc(len)) == NULL) { 93 ret = SSH_ERR_ALLOC_FAIL; 94 goto out; 95 } 96 memcpy(*sigp, sshbuf_ptr(b), len); 97 } 98 if (lenp != NULL) 99 *lenp = len; 100 ret = 0; 101 out: 102 explicit_bzero(digest, sizeof(digest)); 103 sshbuf_free(b); 104 sshbuf_free(bb); 105 ECDSA_SIG_free(sig); 106 return ret; 107 } 108 109 /* ARGSUSED */ 110 int 111 ssh_ecdsa_verify(const struct sshkey *key, 112 const u_char *signature, size_t signaturelen, 113 const u_char *data, size_t datalen, u_int compat) 114 { 115 ECDSA_SIG *sig = NULL; 116 BIGNUM *sig_r = NULL, *sig_s = NULL; 117 int hash_alg; 118 u_char digest[SSH_DIGEST_MAX_LENGTH]; 119 size_t dlen; 120 int ret = SSH_ERR_INTERNAL_ERROR; 121 struct sshbuf *b = NULL, *sigbuf = NULL; 122 char *ktype = NULL; 123 124 if (key == NULL || key->ecdsa == NULL || 125 sshkey_type_plain(key->type) != KEY_ECDSA || 126 signature == NULL || signaturelen == 0) 127 return SSH_ERR_INVALID_ARGUMENT; 128 129 if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 || 130 (dlen = ssh_digest_bytes(hash_alg)) == 0) 131 return SSH_ERR_INTERNAL_ERROR; 132 133 /* fetch signature */ 134 if ((b = sshbuf_from(signature, signaturelen)) == NULL) 135 return SSH_ERR_ALLOC_FAIL; 136 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 || 137 sshbuf_froms(b, &sigbuf) != 0) { 138 ret = SSH_ERR_INVALID_FORMAT; 139 goto out; 140 } 141 if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) { 142 ret = SSH_ERR_KEY_TYPE_MISMATCH; 143 goto out; 144 } 145 if (sshbuf_len(b) != 0) { 146 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; 147 goto out; 148 } 149 150 /* parse signature */ 151 if (sshbuf_get_bignum2(sigbuf, &sig_r) != 0 || 152 sshbuf_get_bignum2(sigbuf, &sig_s) != 0) { 153 ret = SSH_ERR_INVALID_FORMAT; 154 goto out; 155 } 156 if ((sig = ECDSA_SIG_new()) == NULL) { 157 ret = SSH_ERR_ALLOC_FAIL; 158 goto out; 159 } 160 if (!ECDSA_SIG_set0(sig, sig_r, sig_s)) { 161 ret = SSH_ERR_LIBCRYPTO_ERROR; 162 goto out; 163 } 164 sig_r = sig_s = NULL; /* transferred */ 165 166 if (sshbuf_len(sigbuf) != 0) { 167 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; 168 goto out; 169 } 170 if ((ret = ssh_digest_memory(hash_alg, data, datalen, 171 digest, sizeof(digest))) != 0) 172 goto out; 173 174 switch (ECDSA_do_verify(digest, dlen, 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 } 185 186 out: 187 explicit_bzero(digest, sizeof(digest)); 188 sshbuf_free(sigbuf); 189 sshbuf_free(b); 190 ECDSA_SIG_free(sig); 191 BN_clear_free(sig_r); 192 BN_clear_free(sig_s); 193 free(ktype); 194 return ret; 195 } 196