1 /* $OpenBSD: ssh-ecdsa.c,v 1.11 2014/06/24 01:13:21 djm Exp $ */ 2 /* 3 * Copyright (c) 2000 Markus Friedl. All rights reserved. 4 * Copyright (c) 2010 Damien Miller. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include <sys/types.h> 28 29 #include <openssl/bn.h> 30 #include <openssl/ec.h> 31 #include <openssl/ecdsa.h> 32 #include <openssl/evp.h> 33 34 #include <string.h> 35 36 #include "sshbuf.h" 37 #include "ssherr.h" 38 #include "digest.h" 39 #define SSHKEY_INTERNAL 40 #include "sshkey.h" 41 42 /* ARGSUSED */ 43 int 44 ssh_ecdsa_sign(const struct sshkey *key, u_char **sigp, size_t *lenp, 45 const u_char *data, size_t datalen, u_int compat) 46 { 47 ECDSA_SIG *sig = NULL; 48 int hash_alg; 49 u_char digest[SSH_DIGEST_MAX_LENGTH]; 50 size_t len, dlen; 51 struct sshbuf *b = NULL, *bb = NULL; 52 int ret = SSH_ERR_INTERNAL_ERROR; 53 54 if (lenp != NULL) 55 *lenp = 0; 56 if (sigp != NULL) 57 *sigp = NULL; 58 59 if (key == NULL || key->ecdsa == NULL || 60 sshkey_type_plain(key->type) != KEY_ECDSA) 61 return SSH_ERR_INVALID_ARGUMENT; 62 63 if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 || 64 (dlen = ssh_digest_bytes(hash_alg)) == 0) 65 return SSH_ERR_INTERNAL_ERROR; 66 if ((ret = ssh_digest_memory(hash_alg, data, datalen, 67 digest, sizeof(digest))) != 0) 68 goto out; 69 70 if ((sig = ECDSA_do_sign(digest, dlen, key->ecdsa)) == NULL) { 71 ret = SSH_ERR_LIBCRYPTO_ERROR; 72 goto out; 73 } 74 75 if ((bb = sshbuf_new()) == NULL || (b = sshbuf_new()) == NULL) { 76 ret = SSH_ERR_ALLOC_FAIL; 77 goto out; 78 } 79 if ((ret = sshbuf_put_bignum2(bb, sig->r)) != 0 || 80 (ret = sshbuf_put_bignum2(bb, sig->s)) != 0) 81 goto out; 82 if ((ret = sshbuf_put_cstring(b, sshkey_ssh_name_plain(key))) != 0 || 83 (ret = sshbuf_put_stringb(b, bb)) != 0) 84 goto out; 85 len = sshbuf_len(b); 86 if (sigp != NULL) { 87 if ((*sigp = malloc(len)) == NULL) { 88 ret = SSH_ERR_ALLOC_FAIL; 89 goto out; 90 } 91 memcpy(*sigp, sshbuf_ptr(b), len); 92 } 93 if (lenp != NULL) 94 *lenp = len; 95 ret = 0; 96 out: 97 explicit_bzero(digest, sizeof(digest)); 98 if (b != NULL) 99 sshbuf_free(b); 100 if (bb != NULL) 101 sshbuf_free(bb); 102 if (sig != NULL) 103 ECDSA_SIG_free(sig); 104 return ret; 105 } 106 107 /* ARGSUSED */ 108 int 109 ssh_ecdsa_verify(const struct sshkey *key, 110 const u_char *signature, size_t signaturelen, 111 const u_char *data, size_t datalen, u_int compat) 112 { 113 ECDSA_SIG *sig = NULL; 114 int hash_alg; 115 u_char digest[SSH_DIGEST_MAX_LENGTH]; 116 size_t dlen; 117 int ret = SSH_ERR_INTERNAL_ERROR; 118 struct sshbuf *b = NULL, *sigbuf = NULL; 119 char *ktype = NULL; 120 121 if (key == NULL || key->ecdsa == NULL || 122 sshkey_type_plain(key->type) != KEY_ECDSA) 123 return SSH_ERR_INVALID_ARGUMENT; 124 125 if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 || 126 (dlen = ssh_digest_bytes(hash_alg)) == 0) 127 return SSH_ERR_INTERNAL_ERROR; 128 129 /* fetch signature */ 130 if ((b = sshbuf_from(signature, signaturelen)) == NULL) 131 return SSH_ERR_ALLOC_FAIL; 132 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 || 133 sshbuf_froms(b, &sigbuf) != 0) { 134 ret = SSH_ERR_INVALID_FORMAT; 135 goto out; 136 } 137 if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) { 138 ret = SSH_ERR_KEY_TYPE_MISMATCH; 139 goto out; 140 } 141 if (sshbuf_len(b) != 0) { 142 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; 143 goto out; 144 } 145 146 /* parse signature */ 147 if ((sig = ECDSA_SIG_new()) == NULL) { 148 ret = SSH_ERR_ALLOC_FAIL; 149 goto out; 150 } 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 (sshbuf_len(sigbuf) != 0) { 157 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; 158 goto out; 159 } 160 if ((ret = ssh_digest_memory(hash_alg, data, datalen, 161 digest, sizeof(digest))) != 0) 162 goto out; 163 164 switch (ECDSA_do_verify(digest, dlen, sig, key->ecdsa)) { 165 case 1: 166 ret = 0; 167 break; 168 case 0: 169 ret = SSH_ERR_SIGNATURE_INVALID; 170 goto out; 171 default: 172 ret = SSH_ERR_LIBCRYPTO_ERROR; 173 goto out; 174 } 175 176 out: 177 explicit_bzero(digest, sizeof(digest)); 178 if (sigbuf != NULL) 179 sshbuf_free(sigbuf); 180 if (b != NULL) 181 sshbuf_free(b); 182 if (sig != NULL) 183 ECDSA_SIG_free(sig); 184 free(ktype); 185 return ret; 186 } 187