crypto/openssh/ssh-ecdsa.c

   1 /* $OpenBSD: ssh-ecdsa.c,v 1.4 2010/09/10 01:04:10 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 #ifdef 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 "xmalloc.h"
  41 #include "buffer.h"
  42 #include "compat.h"
  43 #include "log.h"
  44 #include "key.h"
  45
  46 int
  47 ssh_ecdsa_sign(const Key *key, u_char **sigp, u_int *lenp,
  48     const u_char *data, u_int datalen)
  49 {
  50         ECDSA_SIG *sig;
  51         const EVP_MD *evp_md;
  52         EVP_MD_CTX md;
  53         u_char digest[EVP_MAX_MD_SIZE];
  54         u_int len, dlen;
  55         Buffer b, bb;
  56
  57         if (key == NULL || key->ecdsa == NULL ||
  58             (key->type != KEY_ECDSA && key->type != KEY_ECDSA_CERT)) {
  59                 error("%s: no ECDSA key", __func__);
  60                 return -1;
  61         }
  62         evp_md = key_ec_nid_to_evpmd(key->ecdsa_nid);
  63         EVP_DigestInit(&md, evp_md);
  64         EVP_DigestUpdate(&md, data, datalen);
  65         EVP_DigestFinal(&md, digest, &dlen);
  66
  67         sig = ECDSA_do_sign(digest, dlen, key->ecdsa);
  68         memset(digest, 'd', sizeof(digest));
  69
  70         if (sig == NULL) {
  71                 error("%s: sign failed", __func__);
  72                 return -1;
  73         }
  74
  75         buffer_init(&bb);
  76         buffer_put_bignum2(&bb, sig->r);
  77         buffer_put_bignum2(&bb, sig->s);
  78         ECDSA_SIG_free(sig);
  79
  80         buffer_init(&b);
  81         buffer_put_cstring(&b, key_ssh_name_plain(key));
  82         buffer_put_string(&b, buffer_ptr(&bb), buffer_len(&bb));
  83         buffer_free(&bb);
  84         len = buffer_len(&b);
  85         if (lenp != NULL)
  86                 *lenp = len;
  87         if (sigp != NULL) {
  88                 *sigp = xmalloc(len);
  89                 memcpy(*sigp, buffer_ptr(&b), len);
  90         }
  91         buffer_free(&b);
  92
  93         return 0;
  94 }
  95 int
  96 ssh_ecdsa_verify(const Key *key, const u_char *signature, u_int signaturelen,
  97     const u_char *data, u_int datalen)
  98 {
  99         ECDSA_SIG *sig;
 100         const EVP_MD *evp_md;
 101         EVP_MD_CTX md;
 102         u_char digest[EVP_MAX_MD_SIZE], *sigblob;
 103         u_int len, dlen;
 104         int rlen, ret;
 105         Buffer b, bb;
 106         char *ktype;
 107
 108         if (key == NULL || key->ecdsa == NULL ||
 109             (key->type != KEY_ECDSA && key->type != KEY_ECDSA_CERT)) {
 110                 error("%s: no ECDSA key", __func__);
 111                 return -1;
 112         }
 113         evp_md = key_ec_nid_to_evpmd(key->ecdsa_nid);
 114
 115         /* fetch signature */
 116         buffer_init(&b);
 117         buffer_append(&b, signature, signaturelen);
 118         ktype = buffer_get_string(&b, NULL);
 119         if (strcmp(key_ssh_name_plain(key), ktype) != 0) {
 120                 error("%s: cannot handle type %s", __func__, ktype);
 121                 buffer_free(&b);
 122                 xfree(ktype);
 123                 return -1;
 124         }
 125         xfree(ktype);
 126         sigblob = buffer_get_string(&b, &len);
 127         rlen = buffer_len(&b);
 128         buffer_free(&b);
 129         if (rlen != 0) {
 130                 error("%s: remaining bytes in signature %d", __func__, rlen);
 131                 xfree(sigblob);
 132                 return -1;
 133         }
 134
 135         /* parse signature */
 136         if ((sig = ECDSA_SIG_new()) == NULL)
 137                 fatal("%s: ECDSA_SIG_new failed", __func__);
 138         if ((sig->r = BN_new()) == NULL ||
 139             (sig->s = BN_new()) == NULL)
 140                 fatal("%s: BN_new failed", __func__);
 141
 142         buffer_init(&bb);
 143         buffer_append(&bb, sigblob, len);
 144         buffer_get_bignum2(&bb, sig->r);
 145         buffer_get_bignum2(&bb, sig->s);
 146         if (buffer_len(&bb) != 0)
 147                 fatal("%s: remaining bytes in inner sigblob", __func__);
 148
 149         /* clean up */
 150         memset(sigblob, 0, len);
 151         xfree(sigblob);
 152
 153         /* hash the data */
 154         EVP_DigestInit(&md, evp_md);
 155         EVP_DigestUpdate(&md, data, datalen);
 156         EVP_DigestFinal(&md, digest, &dlen);
 157
 158         ret = ECDSA_do_verify(digest, dlen, sig, key->ecdsa);
 159         memset(digest, 'd', sizeof(digest));
 160
 161         ECDSA_SIG_free(sig);
 162
 163         debug("%s: signature %s", __func__,
 164             ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error");
 165         return ret;
 166 }
 167
 168 #endif /* OPENSSL_HAS_ECC */