1 /* $OpenBSD: ssh-ecdsa.c,v 1.16 2019/01/21 09:54:11 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 "includes.h" 28 29 #if defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) 30 31 #include <sys/types.h> 32 33 #include <openssl/bn.h> 34 #include <openssl/ec.h> 35 #include <openssl/ecdsa.h> 36 #include <openssl/evp.h> 37 38 #include <string.h> 39 40 #include "sshbuf.h" 41 #include "ssherr.h" 42 #include "digest.h" 43 #define SSHKEY_INTERNAL 44 #include "sshkey.h" 45 46 #include "openbsd-compat/openssl-compat.h" 47 48 /* ARGSUSED */ 49 int 50 ssh_ecdsa_sign(const struct sshkey *key, u_char **sigp, size_t *lenp, 51 const u_char *data, size_t datalen, u_int compat) 52 { 53 ECDSA_SIG *sig = NULL; 54 const BIGNUM *sig_r, *sig_s; 55 int hash_alg; 56 u_char digest[SSH_DIGEST_MAX_LENGTH]; 57 size_t len, dlen; 58 struct sshbuf *b = NULL, *bb = NULL; 59 int ret = SSH_ERR_INTERNAL_ERROR; 60 61 if (lenp != NULL) 62 *lenp = 0; 63 if (sigp != NULL) 64 *sigp = NULL; 65 66 if (key == NULL || key->ecdsa == NULL || 67 sshkey_type_plain(key->type) != KEY_ECDSA) 68 return SSH_ERR_INVALID_ARGUMENT; 69 70 if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 || 71 (dlen = ssh_digest_bytes(hash_alg)) == 0) 72 return SSH_ERR_INTERNAL_ERROR; 73 if ((ret = ssh_digest_memory(hash_alg, data, datalen, 74 digest, sizeof(digest))) != 0) 75 goto out; 76 77 if ((sig = ECDSA_do_sign(digest, dlen, key->ecdsa)) == NULL) { 78 ret = SSH_ERR_LIBCRYPTO_ERROR; 79 goto out; 80 } 81 82 if ((bb = sshbuf_new()) == NULL || (b = sshbuf_new()) == NULL) { 83 ret = SSH_ERR_ALLOC_FAIL; 84 goto out; 85 } 86 ECDSA_SIG_get0(sig, &sig_r, &sig_s); 87 if ((ret = sshbuf_put_bignum2(bb, sig_r)) != 0 || 88 (ret = sshbuf_put_bignum2(bb, sig_s)) != 0) 89 goto out; 90 if ((ret = sshbuf_put_cstring(b, sshkey_ssh_name_plain(key))) != 0 || 91 (ret = sshbuf_put_stringb(b, bb)) != 0) 92 goto out; 93 len = sshbuf_len(b); 94 if (sigp != NULL) { 95 if ((*sigp = malloc(len)) == NULL) { 96 ret = SSH_ERR_ALLOC_FAIL; 97 goto out; 98 } 99 memcpy(*sigp, sshbuf_ptr(b), len); 100 } 101 if (lenp != NULL) 102 *lenp = len; 103 ret = 0; 104 out: 105 explicit_bzero(digest, sizeof(digest)); 106 sshbuf_free(b); 107 sshbuf_free(bb); 108 ECDSA_SIG_free(sig); 109 return ret; 110 } 111 112 /* ARGSUSED */ 113 int 114 ssh_ecdsa_verify(const struct sshkey *key, 115 const u_char *signature, size_t signaturelen, 116 const u_char *data, size_t datalen, u_int compat) 117 { 118 ECDSA_SIG *sig = NULL; 119 BIGNUM *sig_r = NULL, *sig_s = NULL; 120 int hash_alg; 121 u_char digest[SSH_DIGEST_MAX_LENGTH]; 122 size_t dlen; 123 int ret = SSH_ERR_INTERNAL_ERROR; 124 struct sshbuf *b = NULL, *sigbuf = NULL; 125 char *ktype = NULL; 126 127 if (key == NULL || key->ecdsa == NULL || 128 sshkey_type_plain(key->type) != KEY_ECDSA || 129 signature == NULL || signaturelen == 0) 130 return SSH_ERR_INVALID_ARGUMENT; 131 132 if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 || 133 (dlen = ssh_digest_bytes(hash_alg)) == 0) 134 return SSH_ERR_INTERNAL_ERROR; 135 136 /* fetch signature */ 137 if ((b = sshbuf_from(signature, signaturelen)) == NULL) 138 return SSH_ERR_ALLOC_FAIL; 139 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 || 140 sshbuf_froms(b, &sigbuf) != 0) { 141 ret = SSH_ERR_INVALID_FORMAT; 142 goto out; 143 } 144 if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) { 145 ret = SSH_ERR_KEY_TYPE_MISMATCH; 146 goto out; 147 } 148 if (sshbuf_len(b) != 0) { 149 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; 150 goto out; 151 } 152 153 /* parse signature */ 154 if (sshbuf_get_bignum2(sigbuf, &sig_r) != 0 || 155 sshbuf_get_bignum2(sigbuf, &sig_s) != 0) { 156 ret = SSH_ERR_INVALID_FORMAT; 157 goto out; 158 } 159 if ((sig = ECDSA_SIG_new()) == NULL) { 160 ret = SSH_ERR_ALLOC_FAIL; 161 goto out; 162 } 163 if (!ECDSA_SIG_set0(sig, sig_r, sig_s)) { 164 ret = SSH_ERR_LIBCRYPTO_ERROR; 165 goto out; 166 } 167 sig_r = sig_s = NULL; /* transferred */ 168 169 if (sshbuf_len(sigbuf) != 0) { 170 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; 171 goto out; 172 } 173 if ((ret = ssh_digest_memory(hash_alg, data, datalen, 174 digest, sizeof(digest))) != 0) 175 goto out; 176 177 switch (ECDSA_do_verify(digest, dlen, sig, key->ecdsa)) { 178 case 1: 179 ret = 0; 180 break; 181 case 0: 182 ret = SSH_ERR_SIGNATURE_INVALID; 183 goto out; 184 default: 185 ret = SSH_ERR_LIBCRYPTO_ERROR; 186 goto out; 187 } 188 189 out: 190 explicit_bzero(digest, sizeof(digest)); 191 sshbuf_free(sigbuf); 192 sshbuf_free(b); 193 ECDSA_SIG_free(sig); 194 BN_clear_free(sig_r); 195 BN_clear_free(sig_s); 196 free(ktype); 197 return ret; 198 } 199 200 #endif /* WITH_OPENSSL && OPENSSL_HAS_ECC */ 201