xref: /openbsd-src/lib/libcrypto/rsa/rsa_pss.c (revision c4bb5f4255b8a6682499631a2086d1d0b9e934ee)

/* $OpenBSD: rsa_pss.c,v 1.19 2024/03/26 05:26:27 joshua 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/err.h>
#include <openssl/evp.h>
#include <openssl/rsa.h>
#include <openssl/sha.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);