/* $OpenBSD: rsa_pss.c,v 1.20 2025/05/10 05:54:38 tb Exp $ */
/* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
 * project 2005.
 */
/* ====================================================================
 * Copyright (c) 2005 The OpenSSL Project.  All rights reserved.
 *
 * 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 above 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 acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    licensing@OpenSSL.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED 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 OpenSSL PROJECT OR
 * ITS 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.
 * ====================================================================
 *
 * This product includes cryptographic software written by Eric Young
 * (eay@cryptsoft.com).  This product includes software written by Tim
 * Hudson (tjh@cryptsoft.com).
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <openssl/bn.h>
#include <openssl/evp.h>
#include <openssl/rsa.h>
#include <openssl/sha.h>

#include "err_local.h"
#include "evp_local.h"
#include "rsa_local.h"

static const unsigned char zeroes[] = { 0, 0, 0, 0, 0, 0, 0, 0 };

int
RSA_verify_PKCS1_PSS(RSA *rsa, const unsigned char *mHash, const EVP_MD *Hash,
    const unsigned char *EM, int sLen)
{
        return RSA_verify_PKCS1_PSS_mgf1(rsa, mHash, Hash, NULL, EM, sLen);
}
LCRYPTO_ALIAS(RSA_verify_PKCS1_PSS);

int
RSA_verify_PKCS1_PSS_mgf1(RSA *rsa, const unsigned char *mHash,
    const EVP_MD *Hash, const EVP_MD *mgf1Hash, const unsigned char *EM,
    int sLen)
{
        int i;
        int ret = 0;
        int hLen, maskedDBLen, MSBits, emLen;
        const unsigned char *H;
        unsigned char *DB = NULL;
        EVP_MD_CTX *md_ctx;
        unsigned char H_[EVP_MAX_MD_SIZE];

        if ((md_ctx = EVP_MD_CTX_new()) == NULL)
                goto err;

        if (mgf1Hash == NULL)
                mgf1Hash = Hash;

        hLen = EVP_MD_size(Hash);
        if (hLen < 0)
                goto err;
        /*
         * Negative sLen has special meanings:
         *      -1      sLen == hLen
         *      -2      salt length is autorecovered from signature
         *      -N      reserved
         */
        if (sLen == -1)
                sLen = hLen;
        else if (sLen == -2)
                sLen = -2;
        else if (sLen < -2) {
                RSAerror(RSA_R_SLEN_CHECK_FAILED);
                goto err;
        }

        MSBits = (BN_num_bits(rsa->n) - 1) & 0x7;
        emLen = RSA_size(rsa);
        if (EM[0] & (0xFF << MSBits)) {
                RSAerror(RSA_R_FIRST_OCTET_INVALID);
                goto err;
        }
        if (MSBits == 0) {
                EM++;
                emLen--;
        }
        if (emLen < (hLen + sLen + 2)) {
                /* sLen can be small negative */
                RSAerror(RSA_R_DATA_TOO_LARGE);
                goto err;
        }
        if (EM[emLen - 1] != 0xbc) {
                RSAerror(RSA_R_LAST_OCTET_INVALID);
                goto err;
        }
        maskedDBLen = emLen - hLen - 1;
        H = EM + maskedDBLen;
        DB = malloc(maskedDBLen);
        if (!DB) {
                RSAerror(ERR_R_MALLOC_FAILURE);
                goto err;
        }
        if (PKCS1_MGF1(DB, maskedDBLen, H, hLen, mgf1Hash) < 0)
                goto err;
        for (i = 0; i < maskedDBLen; i++)
                DB[i] ^= EM[i];
        if (MSBits)
                DB[0] &= 0xFF >> (8 - MSBits);
        for (i = 0; DB[i] == 0 && i < (maskedDBLen - 1); i++)
                ;
        if (DB[i++] != 0x1) {
                RSAerror(RSA_R_SLEN_RECOVERY_FAILED);
                goto err;
        }
        if (sLen >= 0 && (maskedDBLen - i) != sLen) {
                RSAerror(RSA_R_SLEN_CHECK_FAILED);
                goto err;
        }
        if (!EVP_DigestInit_ex(md_ctx, Hash, NULL) ||
            !EVP_DigestUpdate(md_ctx, zeroes, sizeof zeroes) ||
            !EVP_DigestUpdate(md_ctx, mHash, hLen))
                goto err;
        if (maskedDBLen - i) {
                if (!EVP_DigestUpdate(md_ctx, DB + i, maskedDBLen - i))
                        goto err;
        }
        if (!EVP_DigestFinal_ex(md_ctx, H_, NULL))
                goto err;
        if (timingsafe_bcmp(H_, H, hLen)) {
                RSAerror(RSA_R_BAD_SIGNATURE);
                ret = 0;
        } else {
                ret = 1;
        }

 err:
        free(DB);
        EVP_MD_CTX_free(md_ctx);

        return ret;
}
LCRYPTO_ALIAS(RSA_verify_PKCS1_PSS_mgf1);

int
RSA_padding_add_PKCS1_PSS(RSA *rsa, unsigned char *EM,
    const unsigned char *mHash, const EVP_MD *Hash, int sLen)
{
        return RSA_padding_add_PKCS1_PSS_mgf1(rsa, EM, mHash, Hash, NULL, sLen);
}
LCRYPTO_ALIAS(RSA_padding_add_PKCS1_PSS);

int
RSA_padding_add_PKCS1_PSS_mgf1(RSA *rsa, unsigned char *EM,
    const unsigned char *mHash, const EVP_MD *Hash, const EVP_MD *mgf1Hash,
    int sLen)
{
        int i;
        int ret = 0;
        int hLen, maskedDBLen, MSBits, emLen;
        unsigned char *H, *salt = NULL, *p;
        EVP_MD_CTX *md_ctx;

        if ((md_ctx = EVP_MD_CTX_new()) == NULL)
                goto err;

        if (mgf1Hash == NULL)
                mgf1Hash = Hash;

        hLen = EVP_MD_size(Hash);
        if (hLen < 0)
                goto err;
        /*
         * Negative sLen has special meanings:
         *      -1      sLen == hLen
         *      -2      salt length is maximized
         *      -N      reserved
         */
        if (sLen == -1)
                sLen = hLen;
        else if (sLen == -2)
                sLen = -2;
        else if (sLen < -2) {
                RSAerror(RSA_R_SLEN_CHECK_FAILED);
                goto err;
        }

        MSBits = (BN_num_bits(rsa->n) - 1) & 0x7;
        emLen = RSA_size(rsa);
        if (MSBits == 0) {
                *EM++ = 0;
                emLen--;
        }
        if (sLen == -2)
                sLen = emLen - hLen - 2;
        else if (emLen < (hLen + sLen + 2)) {
                RSAerror(RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
                goto err;
        }
        if (sLen > 0) {
                salt = malloc(sLen);
                if (!salt) {
                        RSAerror(ERR_R_MALLOC_FAILURE);
                        goto err;
                }
                arc4random_buf(salt, sLen);
        }
        maskedDBLen = emLen - hLen - 1;
        H = EM + maskedDBLen;
        if (!EVP_DigestInit_ex(md_ctx, Hash, NULL) ||
            !EVP_DigestUpdate(md_ctx, zeroes, sizeof zeroes) ||
            !EVP_DigestUpdate(md_ctx, mHash, hLen))
                goto err;
        if (sLen && !EVP_DigestUpdate(md_ctx, salt, sLen))
                goto err;
        if (!EVP_DigestFinal_ex(md_ctx, H, NULL))
                goto err;

        /* Generate dbMask in place then perform XOR on it */
        if (PKCS1_MGF1(EM, maskedDBLen, H, hLen, mgf1Hash))
                goto err;

        p = EM;

        /*
         * Initial PS XORs with all zeroes which is a NOP so just update
         * pointer. Note from a test above this value is guaranteed to
         * be non-negative.
         */
        p += emLen - sLen - hLen - 2;
        *p++ ^= 0x1;
        if (sLen > 0) {
                for (i = 0; i < sLen; i++)
                        *p++ ^= salt[i];
        }
        if (MSBits)
                EM[0] &= 0xFF >> (8 - MSBits);

        /* H is already in place so just set final 0xbc */
        EM[emLen - 1] = 0xbc;

        ret = 1;

err:
        free(salt);
        EVP_MD_CTX_free(md_ctx);

        return ret;
}
LCRYPTO_ALIAS(RSA_padding_add_PKCS1_PSS_mgf1);