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openssh-portable/dsa.c

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/*
* Copyright (c) 2000 Markus Friedl. 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Markus Friedl.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* 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 "includes.h"
RCSID("$OpenBSD: dsa.c,v 1.9 2000/06/20 01:39:41 markus Exp $");
#include "ssh.h"
#include "xmalloc.h"
#include "buffer.h"
#include "bufaux.h"
#include "compat.h"
#include <openssl/bn.h>
#include <openssl/dh.h>
#include <openssl/rsa.h>
#include <openssl/dsa.h>
#include <openssl/evp.h>
#include <openssl/bio.h>
#include <openssl/pem.h>
#include <openssl/hmac.h>
#include "kex.h"
#include "key.h"
#include "uuencode.h"
#define INTBLOB_LEN 20
#define SIGBLOB_LEN (2*INTBLOB_LEN)
Key *
dsa_key_from_blob(
char *blob, int blen)
{
Buffer b;
char *ktype;
int rlen;
DSA *dsa;
Key *key;
#ifdef DEBUG_DSS
dump_base64(stderr, blob, blen);
#endif
/* fetch & parse DSA/DSS pubkey */
key = key_new(KEY_DSA);
dsa = key->dsa;
buffer_init(&b);
buffer_append(&b, blob, blen);
ktype = buffer_get_string(&b, NULL);
if (strcmp(KEX_DSS, ktype) != 0) {
error("dsa_key_from_blob: cannot handle type %s", ktype);
key_free(key);
return NULL;
}
buffer_get_bignum2(&b, dsa->p);
buffer_get_bignum2(&b, dsa->q);
buffer_get_bignum2(&b, dsa->g);
buffer_get_bignum2(&b, dsa->pub_key);
rlen = buffer_len(&b);
if(rlen != 0)
error("dsa_key_from_blob: remaining bytes in key blob %d", rlen);
buffer_free(&b);
debug("keytype %s", ktype);
#ifdef DEBUG_DSS
DSA_print_fp(stderr, dsa, 8);
#endif
return key;
}
int
dsa_make_key_blob(Key *key, unsigned char **blobp, unsigned int *lenp)
{
Buffer b;
int len;
unsigned char *buf;
if (key == NULL || key->type != KEY_DSA)
return 0;
buffer_init(&b);
buffer_put_cstring(&b, KEX_DSS);
buffer_put_bignum2(&b, key->dsa->p);
buffer_put_bignum2(&b, key->dsa->q);
buffer_put_bignum2(&b, key->dsa->g);
buffer_put_bignum2(&b, key->dsa->pub_key);
len = buffer_len(&b);
buf = xmalloc(len);
memcpy(buf, buffer_ptr(&b), len);
memset(buffer_ptr(&b), 0, len);
buffer_free(&b);
if (lenp != NULL)
*lenp = len;
if (blobp != NULL)
*blobp = buf;
return len;
}
int
dsa_sign(
Key *key,
unsigned char **sigp, int *lenp,
unsigned char *data, int datalen)
{
unsigned char *digest;
unsigned char *ret;
DSA_SIG *sig;
EVP_MD *evp_md = EVP_sha1();
EVP_MD_CTX md;
unsigned int rlen;
unsigned int slen;
unsigned int len;
unsigned char sigblob[SIGBLOB_LEN];
Buffer b;
if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
error("dsa_sign: no DSA key");
return -1;
}
digest = xmalloc(evp_md->md_size);
EVP_DigestInit(&md, evp_md);
EVP_DigestUpdate(&md, data, datalen);
EVP_DigestFinal(&md, digest, NULL);
sig = DSA_do_sign(digest, evp_md->md_size, key->dsa);
if (sig == NULL) {
fatal("dsa_sign: cannot sign");
}
rlen = BN_num_bytes(sig->r);
slen = BN_num_bytes(sig->s);
if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
error("bad sig size %d %d", rlen, slen);
DSA_SIG_free(sig);
return -1;
}
debug("sig size %d %d", rlen, slen);
memset(sigblob, 0, SIGBLOB_LEN);
BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen);
BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen);
DSA_SIG_free(sig);
if (datafellows & SSH_BUG_SIGBLOB) {
debug("datafellows");
ret = xmalloc(SIGBLOB_LEN);
memcpy(ret, sigblob, SIGBLOB_LEN);
if (lenp != NULL)
*lenp = SIGBLOB_LEN;
if (sigp != NULL)
*sigp = ret;
} else {
/* ietf-drafts */
buffer_init(&b);
buffer_put_cstring(&b, KEX_DSS);
buffer_put_string(&b, sigblob, SIGBLOB_LEN);
len = buffer_len(&b);
ret = xmalloc(len);
memcpy(ret, buffer_ptr(&b), len);
buffer_free(&b);
if (lenp != NULL)
*lenp = len;
if (sigp != NULL)
*sigp = ret;
}
return 0;
}
int
dsa_verify(
Key *key,
unsigned char *signature, int signaturelen,
unsigned char *data, int datalen)
{
Buffer b;
unsigned char *digest;
DSA_SIG *sig;
EVP_MD *evp_md = EVP_sha1();
EVP_MD_CTX md;
unsigned char *sigblob;
char *txt;
unsigned int len;
int rlen;
int ret;
if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
error("dsa_verify: no DSA key");
return -1;
}
if (!(datafellows & SSH_BUG_SIGBLOB) &&
signaturelen == SIGBLOB_LEN) {
datafellows |= ~SSH_BUG_SIGBLOB;
log("autodetect SSH_BUG_SIGBLOB");
} else if ((datafellows & SSH_BUG_SIGBLOB) &&
signaturelen != SIGBLOB_LEN) {
log("autoremove SSH_BUG_SIGBLOB");
datafellows &= ~SSH_BUG_SIGBLOB;
}
debug("len %d datafellows %d", signaturelen, datafellows);
/* fetch signature */
if (datafellows & SSH_BUG_SIGBLOB) {
sigblob = signature;
len = signaturelen;
} else {
/* ietf-drafts */
char *ktype;
buffer_init(&b);
buffer_append(&b, (char *) signature, signaturelen);
ktype = buffer_get_string(&b, NULL);
if (strcmp(KEX_DSS, ktype) != 0) {
error("dsa_verify: cannot handle type %s", ktype);
buffer_free(&b);
return -1;
}
sigblob = (unsigned char *)buffer_get_string(&b, &len);
rlen = buffer_len(&b);
if(rlen != 0) {
error("remaining bytes in signature %d", rlen);
buffer_free(&b);
return -1;
}
buffer_free(&b);
xfree(ktype);
}
if (len != SIGBLOB_LEN) {
fatal("bad sigbloblen %d != SIGBLOB_LEN", len);
}
/* parse signature */
sig = DSA_SIG_new();
sig->r = BN_new();
sig->s = BN_new();
BN_bin2bn(sigblob, INTBLOB_LEN, sig->r);
BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s);
if (!(datafellows & SSH_BUG_SIGBLOB)) {
memset(sigblob, 0, len);
xfree(sigblob);
}
/* sha1 the data */
digest = xmalloc(evp_md->md_size);
EVP_DigestInit(&md, evp_md);
EVP_DigestUpdate(&md, data, datalen);
EVP_DigestFinal(&md, digest, NULL);
ret = DSA_do_verify(digest, evp_md->md_size, sig, key->dsa);
memset(digest, 0, evp_md->md_size);
xfree(digest);
DSA_SIG_free(sig);
switch (ret) {
case 1:
txt = "correct";
break;
case 0:
txt = "incorrect";
break;
case -1:
default:
txt = "error";
break;
}
debug("dsa_verify: signature %s", txt);
return ret;
}
Key *
dsa_generate_key(unsigned int bits)
{
DSA *dsa = DSA_generate_parameters(bits, NULL, 0, NULL, NULL, NULL, NULL);
Key *k;
if (dsa == NULL) {
fatal("DSA_generate_parameters failed");
}
if (!DSA_generate_key(dsa)) {
fatal("DSA_generate_keys failed");
}
k = key_new(KEY_EMPTY);
k->type = KEY_DSA;
k->dsa = dsa;
return k;
}
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