/* crypto/rsa/rsa_pk1.c */

/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)

 * All rights reserved.

 *

 * This package is an SSL implementation written

 * by Eric Young (eay@cryptsoft.com).

 * The implementation was written so as to conform with Netscapes SSL.

 *

 * This library is free for commercial and non-commercial use as long as

 * the following conditions are aheared to.  The following conditions

 * apply to all code found in this distribution, be it the RC4, RSA,

 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation

 * included with this distribution is covered by the same copyright terms

 * except that the holder is Tim Hudson (tjh@cryptsoft.com).

 *

 * Copyright remains Eric Young's, and as such any Copyright notices in

 * the code are not to be removed.

 * If this package is used in a product, Eric Young should be given attribution

 * as the author of the parts of the library used.

 * This can be in the form of a textual message at program startup or

 * in documentation (online or textual) provided with the package.

 *

 * 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 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 cryptographic software written by

 *     Eric Young (eay@cryptsoft.com)"

 *    The word 'cryptographic' can be left out if the rouines from the library

 *    being used are not cryptographic related :-).

 * 4. If you include any Windows specific code (or a derivative thereof) from

 *    the apps directory (application code) you must include an acknowledgement:

 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"

 *

 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``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 OR CONTRIBUTORS 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.

 *

 * The licence and distribution terms for any publically available version or

 * derivative of this code cannot be changed.  i.e. this code cannot simply be

 * copied and put under another distribution licence

 * [including the GNU Public Licence.]

 */

#include "constant_time_locl.h"

#include <stdio.h>

#include "cryptlib.h"

#include <openssl/bn.h>

#include <openssl/rsa.h>

#include <openssl/rand.h>

int RSA_padding_add_PKCS1_type_1(unsigned char *to, int tlen,

                                 const unsigned char *from, int flen)

{

    int j;

    unsigned char *p;

    if (flen > (tlen - RSA_PKCS1_PADDING_SIZE)) {

        RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_TYPE_1,

               RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);

        return (0);

    }

    p = (unsigned char *)to;

    *(p++) = 0;

    *(p++) = 1;                 /* Private Key BT (Block Type) */

    /* pad out with 0xff data */

    j = tlen - 3 - flen;

    memset(p, 0xff, j);

    p += j;

    *(p++) = '\0';

    memcpy(p, from, (unsigned int)flen);

    return (1);

}

int RSA_padding_check_PKCS1_type_1(unsigned char *to, int tlen,

                                   const unsigned char *from, int flen,

                                   int num)

{

    int i, j;

    const unsigned char *p;

    p = from;

    if ((num != (flen + 1)) || (*(p++) != 01)) {

        RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,

               RSA_R_BLOCK_TYPE_IS_NOT_01);

        return (-1);

    }

    /* scan over padding data */

    j = flen - 1;               /* one for type. */

    for (i = 0; i < j; i++) {

        if (*p != 0xff) {       /* should decrypt to 0xff */

            if (*p == 0) {

                p++;

                break;

            } else {

                RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,

                       RSA_R_BAD_FIXED_HEADER_DECRYPT);

                return (-1);

            }

        }

        p++;

    }

    if (i == j) {

        RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,

               RSA_R_NULL_BEFORE_BLOCK_MISSING);

        return (-1);

    }

    if (i < 8) {

        RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,

               RSA_R_BAD_PAD_BYTE_COUNT);

        return (-1);

    }

    i++;                        /* Skip over the '\0' */

    j -= i;

    if (j > tlen) {

        RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1, RSA_R_DATA_TOO_LARGE);

        return (-1);

    }

    memcpy(to, p, (unsigned int)j);

    return (j);

}

int RSA_padding_add_PKCS1_type_2(unsigned char *to, int tlen,

                                 const unsigned char *from, int flen)

{

    int i, j;

    unsigned char *p;

    if (flen > (tlen - 11)) {

        RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_TYPE_2,

               RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);

        return (0);

    }

    p = (unsigned char *)to;

    *(p++) = 0;

    *(p++) = 2;                 /* Public Key BT (Block Type) */

    /* pad out with non-zero random data */

    j = tlen - 3 - flen;

    if (RAND_bytes(p, j) <= 0)

        return (0);

    for (i = 0; i < j; i++) {

        if (*p == '\0')

            do {

                if (RAND_bytes(p, 1) <= 0)

                    return (0);

            } while (*p == '\0');

        p++;

    }

    *(p++) = '\0';

    memcpy(p, from, (unsigned int)flen);

    return (1);

}

int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen,

                                   const unsigned char *from, int flen,

                                   int num)

{

    int i;

    /* |em| is the encoded message, zero-padded to exactly |num| bytes */

    unsigned char *em = NULL;

    unsigned int good, found_zero_byte;

    int zero_index = 0, msg_index, mlen = -1;

    if (tlen < 0 || flen < 0)

        return -1;

    /*

     * PKCS#1 v1.5 decryption. See "PKCS #1 v2.2: RSA Cryptography Standard",

     * section 7.2.2.

     */

    if (flen > num)

        goto err;

    if (num < 11)

        goto err;

    em = OPENSSL_malloc(num);

    if (em == NULL) {

        RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, ERR_R_MALLOC_FAILURE);

        return -1;

    }

    memset(em, 0, num);

    /*

     * Always do this zero-padding copy (even when num == flen) to avoid

     * leaking that information. The copy still leaks some side-channel

     * information, but it's impossible to have a fixed  memory access

     * pattern since we can't read out of the bounds of |from|.

     *

     * TODO(emilia): Consider porting BN_bn2bin_padded from BoringSSL.

     */

    memcpy(em + num - flen, from, flen);

    good = constant_time_is_zero(em[0]);

    good &= constant_time_eq(em[1], 2);

    found_zero_byte = 0;

    for (i = 2; i < num; i++) {

        unsigned int equals0 = constant_time_is_zero(em[i]);

        zero_index =

            constant_time_select_int(~found_zero_byte & equals0, i,

                                     zero_index);

        found_zero_byte |= equals0;

    }

    /*

     * PS must be at least 8 bytes long, and it starts two bytes into |em|.

     * If we never found a 0-byte, then |zero_index| is 0 and the check

     * also fails.

     */

    good &= constant_time_ge((unsigned int)(zero_index), 2 + 8);

    /*

     * Skip the zero byte. This is incorrect if we never found a zero-byte

     * but in this case we also do not copy the message out.

     */

    msg_index = zero_index + 1;

    mlen = num - msg_index;

    /*

     * For good measure, do this check in constant time as well; it could

     * leak something if |tlen| was assuming valid padding.

     */

    good &= constant_time_ge((unsigned int)(tlen), (unsigned int)(mlen));

    /*

     * We can't continue in constant-time because we need to copy the result

     * and we cannot fake its length. This unavoidably leaks timing

     * information at the API boundary.

     */

    if (!good) {

        mlen = -1;

        goto err;

    }

    memcpy(to, em + msg_index, mlen);

 err:

    if (em != NULL) {

        OPENSSL_cleanse(em, num);

        OPENSSL_free(em);

    }

    if (mlen == -1)

        RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2,

               RSA_R_PKCS_DECODING_ERROR);

    return mlen;

}