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/* $OpenBSD: ssh-ecdsa.c,v 1.4 2010/09/10 01:04:10 djm Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
* Copyright (c) 2010 Damien Miller. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/types.h>
#include <openssl/bn.h>
#include <openssl/ec.h>
#include <openssl/ecdsa.h>
#include <openssl/evp.h>
#include <string.h>
#include "xmalloc.h"
#include "buffer.h"
#include "compat.h"
#include "log.h"
#include "key.h"
int
ssh_ecdsa_sign(const Key *key, u_char **sigp, u_int *lenp,
const u_char *data, u_int datalen)
{
ECDSA_SIG *sig;
const EVP_MD *evp_md;
EVP_MD_CTX md;
u_char digest[EVP_MAX_MD_SIZE];
u_int len, dlen;
Buffer b, bb;
if (key == NULL || key->ecdsa == NULL ||
(key->type != KEY_ECDSA && key->type != KEY_ECDSA_CERT)) {
error("%s: no ECDSA key", __func__);
return -1;
}
evp_md = key_ec_nid_to_evpmd(key->ecdsa_nid);
EVP_DigestInit(&md, evp_md);
EVP_DigestUpdate(&md, data, datalen);
EVP_DigestFinal(&md, digest, &dlen);
sig = ECDSA_do_sign(digest, dlen, key->ecdsa);
memset(digest, 'd', sizeof(digest));
if (sig == NULL) {
error("%s: sign failed", __func__);
return -1;
}
buffer_init(&bb);
buffer_put_bignum2(&bb, sig->r);
buffer_put_bignum2(&bb, sig->s);
ECDSA_SIG_free(sig);
buffer_init(&b);
buffer_put_cstring(&b, key_ssh_name_plain(key));
buffer_put_string(&b, buffer_ptr(&bb), buffer_len(&bb));
buffer_free(&bb);
len = buffer_len(&b);
if (lenp != NULL)
*lenp = len;
if (sigp != NULL) {
*sigp = xmalloc(len);
memcpy(*sigp, buffer_ptr(&b), len);
}
buffer_free(&b);
return 0;
}
int
ssh_ecdsa_verify(const Key *key, const u_char *signature, u_int signaturelen,
const u_char *data, u_int datalen)
{
ECDSA_SIG *sig;
const EVP_MD *evp_md;
EVP_MD_CTX md;
u_char digest[EVP_MAX_MD_SIZE], *sigblob;
u_int len, dlen;
int rlen, ret;
Buffer b, bb;
char *ktype;
if (key == NULL || key->ecdsa == NULL ||
(key->type != KEY_ECDSA && key->type != KEY_ECDSA_CERT)) {
error("%s: no ECDSA key", __func__);
return -1;
}
evp_md = key_ec_nid_to_evpmd(key->ecdsa_nid);
/* fetch signature */
buffer_init(&b);
buffer_append(&b, signature, signaturelen);
ktype = buffer_get_string(&b, NULL);
if (strcmp(key_ssh_name_plain(key), ktype) != 0) {
error("%s: cannot handle type %s", __func__, ktype);
buffer_free(&b);
xfree(ktype);
return -1;
}
xfree(ktype);
sigblob = buffer_get_string(&b, &len);
rlen = buffer_len(&b);
buffer_free(&b);
if (rlen != 0) {
error("%s: remaining bytes in signature %d", __func__, rlen);
xfree(sigblob);
return -1;
}
/* parse signature */
if ((sig = ECDSA_SIG_new()) == NULL)
fatal("%s: ECDSA_SIG_new failed", __func__);
if ((sig->r = BN_new()) == NULL ||
(sig->s = BN_new()) == NULL)
fatal("%s: BN_new failed", __func__);
buffer_init(&bb);
buffer_append(&bb, sigblob, len);
buffer_get_bignum2(&bb, sig->r);
buffer_get_bignum2(&bb, sig->s);
if (buffer_len(&bb) != 0)
fatal("%s: remaining bytes in inner sigblob", __func__);
/* clean up */
memset(sigblob, 0, len);
xfree(sigblob);
/* hash the data */
EVP_DigestInit(&md, evp_md);
EVP_DigestUpdate(&md, data, datalen);
EVP_DigestFinal(&md, digest, &dlen);
ret = ECDSA_do_verify(digest, dlen, sig, key->ecdsa);
memset(digest, 'd', sizeof(digest));
ECDSA_SIG_free(sig);
debug("%s: signature %s", __func__,
ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error");
return ret;
}
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