/* 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. 
     * TODO(emilia): this could be addressed at the call site,
     * see BoringSSL commit 0aa0767340baf925bda4804882aab0cb974b2d26. 
     */
    if (! good) {
        mlen = -1;
        goto err;
    }

    memcpy(to, em + msg_index, mlen);

 err:
    if (em ! = NULL)
        OPENSSL_free(em);
    if (mlen == -1)
        RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2,
               RSA_R_PKCS_DECODING_ERROR);
    return mlen;
}
