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/*
* The RSA public-key cryptosystem
*
* Copyright (C) 2006-2011, Brainspark B.V.
*
* This file is part of PolarSSL (http://www.polarssl.org)
* Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
*
* All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* 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.
*/
/*
* RSA was designed by Ron Rivest, Adi Shamir and Len Adleman.
*
* http://theory.lcs.mit.edu/~rivest/rsapaper.pdf
* http://www.cacr.math.uwaterloo.ca/hac/about/chap8.pdf
*/
#include "tcg.h"
#include "polarssl/sha1.h"
#include <stdlib.h>
#include <stdio.h>
#include "tpmrsa.h"
#define HASH_LEN 20
void tpmrsa_set_pubkey(tpmrsa_context* ctx,
const unsigned char* key,
int keylen,
const unsigned char* exponent,
int explen) {
tpmrsa_free(ctx);
if(explen == 0) { //Default e= 2^16+1
mpi_lset(&ctx->E, 65537);
} else {
mpi_read_binary(&ctx->E, exponent, explen);
}
mpi_read_binary(&ctx->N, key, keylen);
ctx->len = ( mpi_msb(&ctx->N) + 7) >> 3;
}
static TPM_RESULT tpmrsa_public( tpmrsa_context *ctx,
const unsigned char *input,
unsigned char *output )
{
int ret;
size_t olen;
mpi T;
mpi_init( &T );
MPI_CHK( mpi_read_binary( &T, input, ctx->len ) );
if( mpi_cmp_mpi( &T, &ctx->N ) >= 0 )
{
mpi_free( &T );
return TPM_ENCRYPT_ERROR;
}
olen = ctx->len;
MPI_CHK( mpi_exp_mod( &T, &T, &ctx->E, &ctx->N, &ctx->RN ) );
MPI_CHK( mpi_write_binary( &T, output, olen ) );
cleanup:
mpi_free( &T );
if( ret != 0 )
return TPM_ENCRYPT_ERROR;
return TPM_SUCCESS;
}
static void mgf_mask( unsigned char *dst, int dlen, unsigned char *src, int slen)
{
unsigned char mask[HASH_LEN];
unsigned char counter[4] = {0, 0, 0, 0};
int i;
sha1_context mctx;
//We always hash the src with the counter, so save the partial hash
sha1_starts(&mctx);
sha1_update(&mctx, src, slen);
// Generate and apply dbMask
while(dlen > 0) {
//Copy the sha1 context
sha1_context ctx = mctx;
//compute hash for input || counter
sha1_update(&ctx, counter, sizeof(counter));
sha1_finish(&ctx, mask);
//Apply the mask
for(i = 0; i < (dlen < HASH_LEN ? dlen : HASH_LEN); ++i) {
*(dst++) ^= mask[i];
}
//Increment counter
++counter[3];
dlen -= HASH_LEN;
}
}
/*
* Add the message padding, then do an RSA operation
*/
TPM_RESULT tpmrsa_pub_encrypt_oaep( tpmrsa_context *ctx,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng,
size_t ilen,
const unsigned char *input,
unsigned char *output )
{
int ret;
int olen;
unsigned char* seed = output + 1;
unsigned char* db = output + HASH_LEN +1;
olen = ctx->len-1;
if( f_rng == NULL )
return TPM_ENCRYPT_ERROR;
if( ilen > olen - 2 * HASH_LEN - 1)
return TPM_ENCRYPT_ERROR;
output[0] = 0;
//Encoding parameter p
sha1((unsigned char*)"TCPA", 4, db);
//PS
memset(db + HASH_LEN, 0,
olen - ilen - 2 * HASH_LEN - 1);
//constant 1 byte
db[olen - ilen - HASH_LEN -1] = 0x01;
//input string
memcpy(db + olen - ilen - HASH_LEN,
input, ilen);
//Generate random seed
if( ( ret = f_rng( p_rng, seed, HASH_LEN ) ) != 0 )
return TPM_ENCRYPT_ERROR;
// maskedDB: Apply dbMask to DB
mgf_mask( db, olen - HASH_LEN, seed, HASH_LEN);
// maskedSeed: Apply seedMask to seed
mgf_mask( seed, HASH_LEN, db, olen - HASH_LEN);
// Do the crypto op
return tpmrsa_public(ctx, output, output);
}
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