1 /* $NetBSD: ssh-ecdsa.c,v 1.10 2017/04/18 18:41:46 christos Exp $ */ 2 /* $OpenBSD: ssh-ecdsa.c,v 1.13 2016/04/21 06:08:02 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 1.10 2017/04/18 18:41:46 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 int hash_alg; 52 u_char digest[SSH_DIGEST_MAX_LENGTH]; 53 size_t len, dlen; 54 struct sshbuf *b = NULL, *bb = NULL; 55 int ret = SSH_ERR_INTERNAL_ERROR; 56 57 if (lenp != NULL) 58 *lenp = 0; 59 if (sigp != NULL) 60 *sigp = NULL; 61 62 if (key == NULL || key->ecdsa == NULL || 63 sshkey_type_plain(key->type) != KEY_ECDSA) 64 return SSH_ERR_INVALID_ARGUMENT; 65 66 if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 || 67 (dlen = ssh_digest_bytes(hash_alg)) == 0) 68 return SSH_ERR_INTERNAL_ERROR; 69 if ((ret = ssh_digest_memory(hash_alg, data, datalen, 70 digest, sizeof(digest))) != 0) 71 goto out; 72 73 if ((sig = ECDSA_do_sign(digest, dlen, key->ecdsa)) == NULL) { 74 ret = SSH_ERR_LIBCRYPTO_ERROR; 75 goto out; 76 } 77 78 if ((bb = sshbuf_new()) == NULL || (b = sshbuf_new()) == NULL) { 79 ret = SSH_ERR_ALLOC_FAIL; 80 goto out; 81 } 82 if ((ret = sshbuf_put_bignum2(bb, sig->r)) != 0 || 83 (ret = sshbuf_put_bignum2(bb, sig->s)) != 0) 84 goto out; 85 if ((ret = sshbuf_put_cstring(b, sshkey_ssh_name_plain(key))) != 0 || 86 (ret = sshbuf_put_stringb(b, bb)) != 0) 87 goto out; 88 len = sshbuf_len(b); 89 if (sigp != NULL) { 90 if ((*sigp = malloc(len)) == NULL) { 91 ret = SSH_ERR_ALLOC_FAIL; 92 goto out; 93 } 94 memcpy(*sigp, sshbuf_ptr(b), len); 95 } 96 if (lenp != NULL) 97 *lenp = len; 98 ret = 0; 99 out: 100 explicit_bzero(digest, sizeof(digest)); 101 sshbuf_free(b); 102 sshbuf_free(bb); 103 if (sig != NULL) 104 ECDSA_SIG_free(sig); 105 return ret; 106 } 107 108 /* ARGSUSED */ 109 int 110 ssh_ecdsa_verify(const struct sshkey *key, 111 const u_char *signature, size_t signaturelen, 112 const u_char *data, size_t datalen, u_int compat) 113 { 114 ECDSA_SIG *sig = NULL; 115 int hash_alg; 116 u_char digest[SSH_DIGEST_MAX_LENGTH]; 117 size_t dlen; 118 int ret = SSH_ERR_INTERNAL_ERROR; 119 struct sshbuf *b = NULL, *sigbuf = NULL; 120 char *ktype = NULL; 121 122 if (key == NULL || key->ecdsa == NULL || 123 sshkey_type_plain(key->type) != KEY_ECDSA || 124 signature == NULL || signaturelen == 0) 125 return SSH_ERR_INVALID_ARGUMENT; 126 127 if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 || 128 (dlen = ssh_digest_bytes(hash_alg)) == 0) 129 return SSH_ERR_INTERNAL_ERROR; 130 131 /* fetch signature */ 132 if ((b = sshbuf_from(signature, signaturelen)) == NULL) 133 return SSH_ERR_ALLOC_FAIL; 134 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 || 135 sshbuf_froms(b, &sigbuf) != 0) { 136 ret = SSH_ERR_INVALID_FORMAT; 137 goto out; 138 } 139 if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) { 140 ret = SSH_ERR_KEY_TYPE_MISMATCH; 141 goto out; 142 } 143 if (sshbuf_len(b) != 0) { 144 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; 145 goto out; 146 } 147 148 /* parse signature */ 149 if ((sig = ECDSA_SIG_new()) == NULL) { 150 ret = SSH_ERR_ALLOC_FAIL; 151 goto out; 152 } 153 if (sshbuf_get_bignum2(sigbuf, sig->r) != 0 || 154 sshbuf_get_bignum2(sigbuf, sig->s) != 0) { 155 ret = SSH_ERR_INVALID_FORMAT; 156 goto out; 157 } 158 if (sshbuf_len(sigbuf) != 0) { 159 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; 160 goto out; 161 } 162 if ((ret = ssh_digest_memory(hash_alg, data, datalen, 163 digest, sizeof(digest))) != 0) 164 goto out; 165 166 switch (ECDSA_do_verify(digest, dlen, sig, key->ecdsa)) { 167 case 1: 168 ret = 0; 169 break; 170 case 0: 171 ret = SSH_ERR_SIGNATURE_INVALID; 172 goto out; 173 default: 174 ret = SSH_ERR_LIBCRYPTO_ERROR; 175 goto out; 176 } 177 178 out: 179 explicit_bzero(digest, sizeof(digest)); 180 sshbuf_free(sigbuf); 181 sshbuf_free(b); 182 if (sig != NULL) 183 ECDSA_SIG_free(sig); 184 free(ktype); 185 return ret; 186 } 187