/*
* Copyright (C) 2003 - 2006 Tomasz Kojm <tkojm@clamav.net>
* RSASSA-PSS code (C) Sensory Networks, Inc.
* Written by Tomasz Kojm
*
* Number encoding rutines are based on yyyRSA by Erik Thiele
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02110-1301, USA.
*/
#if HAVE_CONFIG_H
#include "clamav-config.h"
#endif
#ifdef HAVE_GMP
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include <gmp.h>
#include "clamav.h"
#include "others.h"
#include "dsig.h"
#include "str.h"
#include "sha256.h"
#define CLI_NSTR "118640995551645342603070001658453189751527774412027743746599405743243142607464144767361060640655844749760788890022283424922762488917565551002467771109669598189410434699034532232228621591089508178591428456220796841621637175567590476666928698770143328137383952820383197532047771780196576957695822641224262693037"
#define CLI_ESTR "100001027"
#define CLI_NSTRPSS "14783905874077467090262228516557917570254599638376203532031989214105552847269687489771975792123442185817287694951949800908791527542017115600501303394778618535864845235700041590056318230102449612217458549016089313306591388590790796515819654102320725712300822356348724011232654837503241736177907784198700834440681124727060540035754699658105895050096576226753008596881698828185652424901921668758326578462003247906470982092298106789657211905488986281078346361469524484829559560886227198091995498440676639639830463593211386055065360288422394053998134458623712540683294034953818412458362198117811990006021989844180721010947"
#define CLI_ESTRPSS "100002053"
#define PSS_NBITS 2048
#define PSS_DIGEST_LENGTH 32
static char cli_ndecode(char value)
{
int i;
char ncodec[] = {
'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l',
'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
'y', 'z',
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L',
'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
'Y', 'Z',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'+', '/'
};
for(i = 0; i < 64; i++)
if(ncodec[i] == value)
return i;
cli_errmsg("cli_ndecode: value out of range\n");
return -1;
}
static unsigned char *cli_decodesig(const char *sig, int plainlen, mpz_t e, mpz_t n)
{
int i, siglen = strlen(sig), dec;
unsigned char *decoded;
mpz_t r, p, c;
mpz_init(r);
mpz_init(c);
for(i = 0; i < siglen; i++) {
if((dec = cli_ndecode(sig[i])) < 0) {
mpz_clear(r);
mpz_clear(c);
return NULL;
}
mpz_set_ui(r, dec);
mpz_mul_2exp(r, r, 6 * i);
mpz_add(c, c, r);
}
decoded = (unsigned char *) cli_calloc(plainlen + 1, sizeof(unsigned char));
if(!decoded) {
cli_errmsg("cli_decodesig: Can't allocate memory\n");
mpz_clear(r);
mpz_clear(c);
return NULL;
}
mpz_init(p);
mpz_powm(p, c, e, n); /* plain = cipher^e mod n */
mpz_clear(c);
for(i = plainlen - 1; i >= 0; i--) { /* reverse */
mpz_tdiv_qr_ui(p, r, p, 256);
decoded[i] = mpz_get_ui(r);
}
mpz_clear(p);
mpz_clear(r);
return decoded;
}
static void cli_mgf(unsigned char *in, unsigned int inlen, unsigned char *out, unsigned int outlen)
{
SHA256_CTX ctx;
unsigned int i, laps;
unsigned char cnt[4], digest[PSS_DIGEST_LENGTH];
laps = (outlen + PSS_DIGEST_LENGTH - 1) / PSS_DIGEST_LENGTH;
for(i = 0; i < laps; i++) {
cnt[0] = (unsigned char) 0;
cnt[1] = (unsigned char) 0;
cnt[2] = (unsigned char) (i / 256);
cnt[3] = (unsigned char) i;
sha256_init(&ctx);
sha256_update(&ctx, in, inlen);
sha256_update(&ctx, cnt, sizeof(cnt));
sha256_final(&ctx);
sha256_digest(&ctx, digest);
if(i != laps - 1)
memcpy(&out[i * PSS_DIGEST_LENGTH], digest, PSS_DIGEST_LENGTH);
else
memcpy(&out[i * PSS_DIGEST_LENGTH], digest, outlen - i * PSS_DIGEST_LENGTH);
}
}
int cli_versigpss(const unsigned char *sha256, const char *dsig)
{
mpz_t n, e;
SHA256_CTX ctx;
unsigned char *pt, digest1[PSS_DIGEST_LENGTH], digest2[PSS_DIGEST_LENGTH], *salt;
unsigned int plen = PSS_NBITS / 8, hlen, slen, i;
unsigned char dblock[PSS_NBITS / 8 - PSS_DIGEST_LENGTH - 1];
unsigned char mblock[PSS_NBITS / 8 - PSS_DIGEST_LENGTH - 1];
unsigned char fblock[8 + 2 * PSS_DIGEST_LENGTH];
hlen = slen = PSS_DIGEST_LENGTH;
mpz_init_set_str(n, CLI_NSTRPSS, 10);
mpz_init_set_str(e, CLI_ESTRPSS, 10);
if(!(pt = cli_decodesig(dsig, plen, e, n))) {
mpz_clear(n);
mpz_clear(e);
return CL_EDSIG;
}
mpz_clear(n);
mpz_clear(e);
if(pt[plen - 1] != 0xbc) {
cli_dbgmsg("cli_versigpss: Incorrect signature syntax (0xbc)\n");
free(pt);
return CL_EDSIG;
}
memcpy(mblock, pt, plen - hlen - 1);
memcpy(digest2, &pt[plen - hlen - 1], hlen);
free(pt);
cli_mgf(digest2, hlen, dblock, plen - hlen - 1);
for(i = 0; i < plen - hlen - 1; i++)
dblock[i] ^= mblock[i];
dblock[0] &= (0xff >> 1);
salt = memchr(dblock, 0x01, sizeof(dblock));
if(!salt) {
cli_dbgmsg("cli_versigpss: Can't find salt\n");
return CL_EDSIG;
}
salt++;
if((unsigned int) (dblock + sizeof(dblock) - salt) != slen) {
cli_dbgmsg("cli_versigpss: Bad salt size\n");
return CL_EDSIG;
}
memset(fblock, 0, 8);
memcpy(&fblock[8], sha256, hlen);
memcpy(&fblock[8 + hlen], salt, slen);
sha256_init(&ctx);
sha256_update(&ctx, fblock, sizeof(fblock));
sha256_final(&ctx);
sha256_digest(&ctx, digest1);
if(memcmp(digest1, digest2, hlen)) {
cli_dbgmsg("cli_versigpss: Signature doesn't match.\n");
return CL_EDSIG;
}
cli_dbgmsg("cli_versigpss: Digital signature is correct.\n");
return CL_SUCCESS;
}
int cli_versig(const char *md5, const char *dsig)
{
mpz_t n, e;
char *pt, *pt2;
if(strlen(md5) != 32 || !isalnum(md5[0])) {
/* someone is trying to fool us with empty/malformed MD5 ? */
cli_errmsg("SECURITY WARNING: MD5 basic test failure.\n");
return CL_EMD5;
}
mpz_init_set_str(n, CLI_NSTR, 10);
mpz_init_set_str(e, CLI_ESTR, 10);
if(!(pt = (char *) cli_decodesig(dsig, 16, e, n))) {
mpz_clear(n);
mpz_clear(e);
return CL_EDSIG;
}
pt2 = cli_str2hex(pt, 16);
free(pt);
cli_dbgmsg("cli_versig: Decoded signature: %s\n", pt2);
if(strncmp(md5, pt2, 32)) {
cli_dbgmsg("cli_versig: Signature doesn't match.\n");
free(pt2);
mpz_clear(n);
mpz_clear(e);
return CL_EDSIG;
}
free(pt2);
mpz_clear(n);
mpz_clear(e);
cli_dbgmsg("cli_versig: Digital signature is correct.\n");
return CL_SUCCESS;
}
#endif