linux-imx

// SPDX-License-Identifier: GPL-2.0-only

/*

 * Copyright (C) 2011 Nokia Corporation

 * Copyright (C) 2011 Intel Corporation

 *

 * Author:

 * Dmitry Kasatkin <dmitry.kasatkin@nokia.com>

 *                 <dmitry.kasatkin@intel.com>

 *

 * File: sign.c

 *  implements signature (RSA) verification

 *  pkcs decoding is based on LibTomCrypt code

 */

​

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

​

#include <linux/err.h>

#include <linux/module.h>

#include <linux/slab.h>

#include <linux/key.h>

#include <linux/crypto.h>

#include <crypto/hash.h>

#include <crypto/sha.h>

#include <keys/user-type.h>

#include <linux/mpi.h>

#include <linux/digsig.h>

​

static struct crypto_shash *shash;

​

static const char *pkcs_1_v1_5_decode_emsa(const unsigned char *msg,

                        unsigned long  msglen,

                        unsigned long  modulus_bitlen,

                        unsigned long *outlen)

{

    unsigned long modulus_len, ps_len, i;

​

    modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);

​

    /* test message size */

    if ((msglen > modulus_len) || (modulus_len < 11))

        return NULL;

​

    /* separate encoded message */

    if (msg[0] != 0x00 || msg[1] != 0x01)

        return NULL;

​

    for (i = 2; i < modulus_len - 1; i++)

        if (msg[i] != 0xFF)

            break;

​

    /* separator check */

    if (msg[i] != 0)

        /* There was no octet with hexadecimal value 0x00

        to separate ps from m. */

        return NULL;

​

    ps_len = i - 2;

​

    *outlen = (msglen - (2 + ps_len + 1));

​

    return msg + 2 + ps_len + 1;

}

​