crypto/openssh/ssh-dss.c

   1 /* $OpenBSD: ssh-dss.c,v 1.35 2016/04/21 06:08:02 djm Exp $ */
   2 /*
   3  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  17  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "includes.h"
  27
  28 #ifdef WITH_OPENSSL
  29
  30 #include <sys/types.h>
  31
  32 #include <openssl/bn.h>
  33 #include <openssl/dsa.h>
  34 #include <openssl/evp.h>
  35
  36 #include <stdarg.h>
  37 #include <string.h>
  38
  39 #include "sshbuf.h"
  40 #include "compat.h"
  41 #include "ssherr.h"
  42 #include "digest.h"
  43 #define SSHKEY_INTERNAL
  44 #include "sshkey.h"
  45
  46 #define INTBLOB_LEN     20
  47 #define SIGBLOB_LEN     (2*INTBLOB_LEN)
  48
  49 int
  50 ssh_dss_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
  51     const u_char *data, size_t datalen, u_int compat)
  52 {
  53         DSA_SIG *sig = NULL;
  54         u_char digest[SSH_DIGEST_MAX_LENGTH], sigblob[SIGBLOB_LEN];
  55         size_t rlen, slen, len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1);
  56         struct sshbuf *b = NULL;
  57         int ret = SSH_ERR_INVALID_ARGUMENT;
  58
  59         if (lenp != NULL)
  60                 *lenp = 0;
  61         if (sigp != NULL)
  62                 *sigp = NULL;
  63
  64         if (key == NULL || key->dsa == NULL ||
  65             sshkey_type_plain(key->type) != KEY_DSA)
  66                 return SSH_ERR_INVALID_ARGUMENT;
  67         if (dlen == 0)
  68                 return SSH_ERR_INTERNAL_ERROR;
  69
  70         if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen,
  71             digest, sizeof(digest))) != 0)
  72                 goto out;
  73
  74         if ((sig = DSA_do_sign(digest, dlen, key->dsa)) == NULL) {
  75                 ret = SSH_ERR_LIBCRYPTO_ERROR;
  76                 goto out;
  77         }
  78
  79         rlen = BN_num_bytes(sig->r);
  80         slen = BN_num_bytes(sig->s);
  81         if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
  82                 ret = SSH_ERR_INTERNAL_ERROR;
  83                 goto out;
  84         }
  85         explicit_bzero(sigblob, SIGBLOB_LEN);
  86         BN_bn2bin(sig->r, sigblob + SIGBLOB_LEN - INTBLOB_LEN - rlen);
  87         BN_bn2bin(sig->s, sigblob + SIGBLOB_LEN - slen);
  88
  89         if (compat & SSH_BUG_SIGBLOB) {
  90                 if (sigp != NULL) {
  91                         if ((*sigp = malloc(SIGBLOB_LEN)) == NULL) {
  92                                 ret = SSH_ERR_ALLOC_FAIL;
  93                                 goto out;
  94                         }
  95                         memcpy(*sigp, sigblob, SIGBLOB_LEN);
  96                 }
  97                 if (lenp != NULL)
  98                         *lenp = SIGBLOB_LEN;
  99                 ret = 0;
 100         } else {
 101                 /* ietf-drafts */
 102                 if ((b = sshbuf_new()) == NULL) {
 103                         ret = SSH_ERR_ALLOC_FAIL;
 104                         goto out;
 105                 }
 106                 if ((ret = sshbuf_put_cstring(b, "ssh-dss")) != 0 ||
 107                     (ret = sshbuf_put_string(b, sigblob, SIGBLOB_LEN)) != 0)
 108                         goto out;
 109                 len = sshbuf_len(b);
 110                 if (sigp != NULL) {
 111                         if ((*sigp = malloc(len)) == NULL) {
 112                                 ret = SSH_ERR_ALLOC_FAIL;
 113                                 goto out;
 114                         }
 115                         memcpy(*sigp, sshbuf_ptr(b), len);
 116                 }
 117                 if (lenp != NULL)
 118                         *lenp = len;
 119                 ret = 0;
 120         }
 121  out:
 122         explicit_bzero(digest, sizeof(digest));
 123         if (sig != NULL)
 124                 DSA_SIG_free(sig);
 125         sshbuf_free(b);
 126         return ret;
 127 }
 128
 129 int
 130 ssh_dss_verify(const struct sshkey *key,
 131     const u_char *signature, size_t signaturelen,
 132     const u_char *data, size_t datalen, u_int compat)
 133 {
 134         DSA_SIG *sig = NULL;
 135         u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob = NULL;
 136         size_t len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1);
 137         int ret = SSH_ERR_INTERNAL_ERROR;
 138         struct sshbuf *b = NULL;
 139         char *ktype = NULL;
 140
 141         if (key == NULL || key->dsa == NULL ||
 142             sshkey_type_plain(key->type) != KEY_DSA ||
 143             signature == NULL || signaturelen == 0)
 144                 return SSH_ERR_INVALID_ARGUMENT;
 145         if (dlen == 0)
 146                 return SSH_ERR_INTERNAL_ERROR;
 147
 148         /* fetch signature */
 149         if (compat & SSH_BUG_SIGBLOB) {
 150                 if ((sigblob = malloc(signaturelen)) == NULL)
 151                         return SSH_ERR_ALLOC_FAIL;
 152                 memcpy(sigblob, signature, signaturelen);
 153                 len = signaturelen;
 154         } else {
 155                 /* ietf-drafts */
 156                 if ((b = sshbuf_from(signature, signaturelen)) == NULL)
 157                         return SSH_ERR_ALLOC_FAIL;
 158                 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 ||
 159                     sshbuf_get_string(b, &sigblob, &len) != 0) {
 160                         ret = SSH_ERR_INVALID_FORMAT;
 161                         goto out;
 162                 }
 163                 if (strcmp("ssh-dss", ktype) != 0) {
 164                         ret = SSH_ERR_KEY_TYPE_MISMATCH;
 165                         goto out;
 166                 }
 167                 if (sshbuf_len(b) != 0) {
 168                         ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
 169                         goto out;
 170                 }
 171         }
 172
 173         if (len != SIGBLOB_LEN) {
 174                 ret = SSH_ERR_INVALID_FORMAT;
 175                 goto out;
 176         }
 177
 178         /* parse signature */
 179         if ((sig = DSA_SIG_new()) == NULL ||
 180             (sig->r = BN_new()) == NULL ||
 181             (sig->s = BN_new()) == NULL) {
 182                 ret = SSH_ERR_ALLOC_FAIL;
 183                 goto out;
 184         }
 185         if ((BN_bin2bn(sigblob, INTBLOB_LEN, sig->r) == NULL) ||
 186             (BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s) == NULL)) {
 187                 ret = SSH_ERR_LIBCRYPTO_ERROR;
 188                 goto out;
 189         }
 190
 191         /* sha1 the data */
 192         if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen,
 193             digest, sizeof(digest))) != 0)
 194                 goto out;
 195
 196         switch (DSA_do_verify(digest, dlen, sig, key->dsa)) {
 197         case 1:
 198                 ret = 0;
 199                 break;
 200         case 0:
 201                 ret = SSH_ERR_SIGNATURE_INVALID;
 202                 goto out;
 203         default:
 204                 ret = SSH_ERR_LIBCRYPTO_ERROR;
 205                 goto out;
 206         }
 207
 208  out:
 209         explicit_bzero(digest, sizeof(digest));
 210         if (sig != NULL)
 211                 DSA_SIG_free(sig);
 212         sshbuf_free(b);
 213         free(ktype);
 214         if (sigblob != NULL) {
 215                 explicit_bzero(sigblob, len);
 216                 free(sigblob);
 217         }
 218         return ret;
 219 }
 220 #endif /* WITH_OPENSSL */