1 /* $OpenBSD: ssh-ecdsa.c,v 1.15 2018/09/13 02:08:33 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 const BIGNUM *sig_r, *sig_s; 49 int hash_alg; 50 u_char digest[SSH_DIGEST_MAX_LENGTH]; 51 size_t len, dlen; 52 struct sshbuf *b = NULL, *bb = NULL; 53 int ret = SSH_ERR_INTERNAL_ERROR; 54 55 if (lenp != NULL) 56 *lenp = 0; 57 if (sigp != NULL) 58 *sigp = NULL; 59 60 if (key == NULL || key->ecdsa == NULL || 61 sshkey_type_plain(key->type) != KEY_ECDSA) 62 return SSH_ERR_INVALID_ARGUMENT; 63 64 if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 || 65 (dlen = ssh_digest_bytes(hash_alg)) == 0) 66 return SSH_ERR_INTERNAL_ERROR; 67 if ((ret = ssh_digest_memory(hash_alg, data, datalen, 68 digest, sizeof(digest))) != 0) 69 goto out; 70 71 if ((sig = ECDSA_do_sign(digest, dlen, key->ecdsa)) == NULL) { 72 ret = SSH_ERR_LIBCRYPTO_ERROR; 73 goto out; 74 } 75 76 if ((bb = sshbuf_new()) == NULL || (b = sshbuf_new()) == NULL) { 77 ret = SSH_ERR_ALLOC_FAIL; 78 goto out; 79 } 80 ECDSA_SIG_get0(sig, &sig_r, &sig_s); 81 if ((ret = sshbuf_put_bignum2(bb, sig_r)) != 0 || 82 (ret = sshbuf_put_bignum2(bb, sig_s)) != 0) 83 goto out; 84 if ((ret = sshbuf_put_cstring(b, sshkey_ssh_name_plain(key))) != 0 || 85 (ret = sshbuf_put_stringb(b, bb)) != 0) 86 goto out; 87 len = sshbuf_len(b); 88 if (sigp != NULL) { 89 if ((*sigp = malloc(len)) == NULL) { 90 ret = SSH_ERR_ALLOC_FAIL; 91 goto out; 92 } 93 memcpy(*sigp, sshbuf_ptr(b), len); 94 } 95 if (lenp != NULL) 96 *lenp = len; 97 ret = 0; 98 out: 99 explicit_bzero(digest, sizeof(digest)); 100 sshbuf_free(b); 101 sshbuf_free(bb); 102 ECDSA_SIG_free(sig); 103 return ret; 104 } 105 106 /* ARGSUSED */ 107 int 108 ssh_ecdsa_verify(const struct sshkey *key, 109 const u_char *signature, size_t signaturelen, 110 const u_char *data, size_t datalen, u_int compat) 111 { 112 ECDSA_SIG *sig = NULL; 113 BIGNUM *sig_r = NULL, *sig_s = 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 signature == NULL || signaturelen == 0) 124 return SSH_ERR_INVALID_ARGUMENT; 125 126 if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 || 127 (dlen = ssh_digest_bytes(hash_alg)) == 0) 128 return SSH_ERR_INTERNAL_ERROR; 129 130 /* fetch signature */ 131 if ((b = sshbuf_from(signature, signaturelen)) == NULL) 132 return SSH_ERR_ALLOC_FAIL; 133 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 || 134 sshbuf_froms(b, &sigbuf) != 0) { 135 ret = SSH_ERR_INVALID_FORMAT; 136 goto out; 137 } 138 if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) { 139 ret = SSH_ERR_KEY_TYPE_MISMATCH; 140 goto out; 141 } 142 if (sshbuf_len(b) != 0) { 143 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; 144 goto out; 145 } 146 147 /* parse signature */ 148 if ((sig = ECDSA_SIG_new()) == NULL || 149 (sig_r = BN_new()) == NULL || 150 (sig_s = BN_new()) == NULL) { 151 ret = SSH_ERR_ALLOC_FAIL; 152 goto out; 153 } 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 (!ECDSA_SIG_set0(sig, sig_r, sig_s)) { 160 ret = SSH_ERR_LIBCRYPTO_ERROR; 161 goto out; 162 } 163 sig_r = sig_s = NULL; /* transferred */ 164 165 if (sshbuf_len(sigbuf) != 0) { 166 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; 167 goto out; 168 } 169 if ((ret = ssh_digest_memory(hash_alg, data, datalen, 170 digest, sizeof(digest))) != 0) 171 goto out; 172 173 switch (ECDSA_do_verify(digest, dlen, sig, key->ecdsa)) { 174 case 1: 175 ret = 0; 176 break; 177 case 0: 178 ret = SSH_ERR_SIGNATURE_INVALID; 179 goto out; 180 default: 181 ret = SSH_ERR_LIBCRYPTO_ERROR; 182 goto out; 183 } 184 185 out: 186 explicit_bzero(digest, sizeof(digest)); 187 sshbuf_free(sigbuf); 188 sshbuf_free(b); 189 ECDSA_SIG_free(sig); 190 BN_clear_free(sig_r); 191 BN_clear_free(sig_s); 192 free(ktype); 193 return ret; 194 } 195