// Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//     https://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

#include <openssl/base.h>

#include <limits.h>

#include <openssl/bn.h>

#include <openssl/err.h>

#include <openssl/evp.h>

#include <openssl/mem.h>

#include <openssl/rand.h>

#include <openssl/rsa.h>

#include "../fipsmodule/bn/internal.h"

#include "../fipsmodule/rsa/internal.h"

#include "../internal.h"

#include "internal.h"

static void rand_nonzero(uint8_t *out, size_t len) {

  RAND_bytes(out, len);

  for (size_t i = 0; i < len; i++) {

    // Zero values are replaced, and the distribution of zero and non-zero bytes

    // is public, so leaking this is safe.

    while (constant_time_declassify_int(out[i] == 0)) {

      RAND_bytes(out + i, 1);

    }

  }

}

int RSA_padding_add_PKCS1_OAEP_mgf1(uint8_t *to, size_t to_len,

                                    const uint8_t *from, size_t from_len,

                                    const uint8_t *param, size_t param_len,

                                    const EVP_MD *md, const EVP_MD *mgf1md) {

  if (md == NULL) {

    md = EVP_sha1();

  }

  if (mgf1md == NULL) {

    mgf1md = md;

  }

  size_t mdlen = EVP_MD_size(md);

  if (to_len < 2 * mdlen + 2) {

    OPENSSL_PUT_ERROR(RSA, RSA_R_KEY_SIZE_TOO_SMALL);

    return 0;

  }

  size_t emlen = to_len - 1;

  if (from_len > emlen - 2 * mdlen - 1) {

    OPENSSL_PUT_ERROR(RSA, RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);

    return 0;

  }

  if (emlen < 2 * mdlen + 1) {

    OPENSSL_PUT_ERROR(RSA, RSA_R_KEY_SIZE_TOO_SMALL);

    return 0;

  }

  to[0] = 0;

  uint8_t *seed = to + 1;

  uint8_t *db = to + mdlen + 1;

  uint8_t *dbmask = NULL;

  int ret = 0;

  if (!EVP_Digest(param, param_len, db, NULL, md, NULL)) {

    goto out;

  }

  OPENSSL_memset(db + mdlen, 0, emlen - from_len - 2 * mdlen - 1);

  db[emlen - from_len - mdlen - 1] = 0x01;

  OPENSSL_memcpy(db + emlen - from_len - mdlen, from, from_len);

  if (!RAND_bytes(seed, mdlen)) {

    goto out;

  }

  dbmask = reinterpret_cast<uint8_t *>(OPENSSL_malloc(emlen - mdlen));

  if (dbmask == NULL) {

    goto out;

  }

  if (!PKCS1_MGF1(dbmask, emlen - mdlen, seed, mdlen, mgf1md)) {

    goto out;

  }

  for (size_t i = 0; i < emlen - mdlen; i++) {

    db[i] ^= dbmask[i];

  }

  uint8_t seedmask[EVP_MAX_MD_SIZE];

  if (!PKCS1_MGF1(seedmask, mdlen, db, emlen - mdlen, mgf1md)) {

    goto out;

  }

  for (size_t i = 0; i < mdlen; i++) {

    seed[i] ^= seedmask[i];

  }

  ret = 1;

out:

  OPENSSL_free(dbmask);

  return ret;

}

int RSA_padding_check_PKCS1_OAEP_mgf1(uint8_t *out, size_t *out_len,

                                      size_t max_out, const uint8_t *from,

                                      size_t from_len, const uint8_t *param,

                                      size_t param_len, const EVP_MD *md,

                                      const EVP_MD *mgf1md) {

  uint8_t *db = NULL;

  {

    if (md == NULL) {

      md = EVP_sha1();

    }

    if (mgf1md == NULL) {

      mgf1md = md;

    }

    size_t mdlen = EVP_MD_size(md);

    // The encoded message is one byte smaller than the modulus to ensure that

    // it doesn't end up greater than the modulus. Thus there's an extra "+1"

    // here compared to https://tools.ietf.org/html/rfc2437#section-9.1.1.2.

    if (from_len < 1 + 2 * mdlen + 1) {

      // 'from_len' is the length of the modulus, i.e. does not depend on the

      // particular ciphertext.

      goto decoding_err;

    }

    size_t dblen = from_len - mdlen - 1;

    db = reinterpret_cast<uint8_t *>(OPENSSL_malloc(dblen));

    if (db == NULL) {

      goto err;

    }

    const uint8_t *maskedseed = from + 1;

    const uint8_t *maskeddb = from + 1 + mdlen;

    uint8_t seed[EVP_MAX_MD_SIZE];

    if (!PKCS1_MGF1(seed, mdlen, maskeddb, dblen, mgf1md)) {

      goto err;

    }

    for (size_t i = 0; i < mdlen; i++) {

      seed[i] ^= maskedseed[i];

    }

    if (!PKCS1_MGF1(db, dblen, seed, mdlen, mgf1md)) {

      goto err;

    }

    for (size_t i = 0; i < dblen; i++) {

      db[i] ^= maskeddb[i];

    }

    uint8_t phash[EVP_MAX_MD_SIZE];

    if (!EVP_Digest(param, param_len, phash, NULL, md, NULL)) {

      goto err;

    }

    crypto_word_t bad =

        ~constant_time_is_zero_w(CRYPTO_memcmp(db, phash, mdlen));

    bad |= ~constant_time_is_zero_w(from[0]);

    crypto_word_t looking_for_one_byte = CONSTTIME_TRUE_W;

    size_t one_index = 0;

    for (size_t i = mdlen; i < dblen; i++) {

      crypto_word_t equals1 = constant_time_eq_w(db[i], 1);

      crypto_word_t equals0 = constant_time_eq_w(db[i], 0);

      one_index =

          constant_time_select_w(looking_for_one_byte & equals1, i, one_index);

      looking_for_one_byte =

          constant_time_select_w(equals1, 0, looking_for_one_byte);

      bad |= looking_for_one_byte & ~equals0;

    }

    bad |= looking_for_one_byte;

    // Whether the overall padding was valid or not in OAEP is public.

    if (constant_time_declassify_w(bad)) {

      goto decoding_err;

    }

    // Once the padding is known to be valid, the output length is also public.

    static_assert(sizeof(size_t) <= sizeof(crypto_word_t),

                  "size_t does not fit in crypto_word_t");

    one_index = constant_time_declassify_w(one_index);

    one_index++;

    size_t mlen = dblen - one_index;

    if (max_out < mlen) {

      OPENSSL_PUT_ERROR(RSA, RSA_R_DATA_TOO_LARGE);

      goto err;

    }

    OPENSSL_memcpy(out, db + one_index, mlen);

    *out_len = mlen;

    OPENSSL_free(db);

    return 1;

  }

decoding_err:

  // To avoid chosen ciphertext attacks, the error message should not reveal

  // which kind of decoding error happened.

  OPENSSL_PUT_ERROR(RSA, RSA_R_OAEP_DECODING_ERROR);

err:

  OPENSSL_free(db);

  return 0;

}

static int rsa_padding_add_PKCS1_type_2(uint8_t *to, size_t to_len,

                                        const uint8_t *from, size_t from_len) {

  // See RFC 8017, section 7.2.1.

  if (to_len < RSA_PKCS1_PADDING_SIZE) {

    OPENSSL_PUT_ERROR(RSA, RSA_R_KEY_SIZE_TOO_SMALL);

    return 0;

  }

  if (from_len > to_len - RSA_PKCS1_PADDING_SIZE) {

    OPENSSL_PUT_ERROR(RSA, RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);

    return 0;

  }

  to[0] = 0;

  to[1] = 2;

  size_t padding_len = to_len - 3 - from_len;

  rand_nonzero(to + 2, padding_len);

  to[2 + padding_len] = 0;

  OPENSSL_memcpy(to + to_len - from_len, from, from_len);

  return 1;

}

static int rsa_padding_check_PKCS1_type_2(uint8_t *out, size_t *out_len,

                                          size_t max_out, const uint8_t *from,

                                          size_t from_len) {

  if (from_len == 0) {

    OPENSSL_PUT_ERROR(RSA, RSA_R_EMPTY_PUBLIC_KEY);

    return 0;

  }

  // PKCS#1 v1.5 decryption. See "PKCS #1 v2.2: RSA Cryptography

  // Standard", section 7.2.2.

  if (from_len < RSA_PKCS1_PADDING_SIZE) {

    // |from| is zero-padded to the size of the RSA modulus, a public value, so

    // this can be rejected in non-constant time.

    OPENSSL_PUT_ERROR(RSA, RSA_R_KEY_SIZE_TOO_SMALL);

    return 0;

  }

  crypto_word_t first_byte_is_zero = constant_time_eq_w(from[0], 0);

  crypto_word_t second_byte_is_two = constant_time_eq_w(from[1], 2);

  crypto_word_t zero_index = 0, looking_for_index = CONSTTIME_TRUE_W;

  for (size_t i = 2; i < from_len; i++) {

    crypto_word_t equals0 = constant_time_is_zero_w(from[i]);

    zero_index =

        constant_time_select_w(looking_for_index & equals0, i, zero_index);

    looking_for_index = constant_time_select_w(equals0, 0, looking_for_index);

  }

  // The input must begin with 00 02.

  crypto_word_t valid_index = first_byte_is_zero;

  valid_index &= second_byte_is_two;

  // We must have found the end of PS.

  valid_index &= ~looking_for_index;

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

  valid_index &= constant_time_ge_w(zero_index, 2 + 8);

  // Skip the zero byte.

  zero_index++;

  // NOTE: Although this logic attempts to be constant time, the API contracts

  // of this function and |RSA_decrypt| with |RSA_PKCS1_PADDING| make it

  // impossible to completely avoid Bleichenbacher's attack. Consumers should

  // use |RSA_PADDING_NONE| and perform the padding check in constant-time

  // combined with a swap to a random session key or other mitigation.

  CONSTTIME_DECLASSIFY(&valid_index, sizeof(valid_index));

  CONSTTIME_DECLASSIFY(&zero_index, sizeof(zero_index));

  if (!valid_index) {

    OPENSSL_PUT_ERROR(RSA, RSA_R_PKCS_DECODING_ERROR);

    return 0;

  }

  const size_t msg_len = from_len - zero_index;

  if (msg_len > max_out) {

    // This shouldn't happen because this function is always called with

    // |max_out| as the key size and |from_len| is bounded by the key size.

    OPENSSL_PUT_ERROR(RSA, RSA_R_PKCS_DECODING_ERROR);

    return 0;

  }

  OPENSSL_memcpy(out, &from[zero_index], msg_len);

  *out_len = msg_len;

  return 1;

}

int RSA_public_encrypt(size_t flen, const uint8_t *from, uint8_t *to, RSA *rsa,

                       int padding) {

  size_t out_len;

  if (!RSA_encrypt(rsa, &out_len, to, RSA_size(rsa), from, flen, padding)) {

    return -1;

  }

  if (out_len > INT_MAX) {

    OPENSSL_PUT_ERROR(RSA, ERR_R_OVERFLOW);

    return -1;

  }

  return (int)out_len;

}

int RSA_private_encrypt(size_t flen, const uint8_t *from, uint8_t *to, RSA *rsa,

                        int padding) {

  size_t out_len;

  if (!RSA_sign_raw(rsa, &out_len, to, RSA_size(rsa), from, flen, padding)) {

    return -1;

  }

  if (out_len > INT_MAX) {

    OPENSSL_PUT_ERROR(RSA, ERR_R_OVERFLOW);

    return -1;

  }

  return (int)out_len;

}

int RSA_encrypt(RSA *rsa, size_t *out_len, uint8_t *out, size_t max_out,

                const uint8_t *in, size_t in_len, int padding) {

  if (rsa->n == NULL || rsa->e == NULL) {

    OPENSSL_PUT_ERROR(RSA, RSA_R_VALUE_MISSING);

    return 0;

  }

  if (!rsa_check_public_key(rsa)) {

    return 0;

  }

  const unsigned rsa_size = RSA_size(rsa);

  if (max_out < rsa_size) {

    OPENSSL_PUT_ERROR(RSA, RSA_R_OUTPUT_BUFFER_TOO_SMALL);

    return 0;

  }

  bssl::UniquePtr<BN_CTX> ctx(BN_CTX_new());

  if (ctx == nullptr) {

    return 0;

  }

  bssl::BN_CTXScope scope(ctx.get());

  BIGNUM *f = BN_CTX_get(ctx.get());

  BIGNUM *result = BN_CTX_get(ctx.get());

  uint8_t *buf = reinterpret_cast<uint8_t *>(OPENSSL_malloc(rsa_size));

  int i, ret = 0;

  if (!f || !result || !buf) {

    goto err;

  }

  switch (padding) {

    case RSA_PKCS1_PADDING:

      i = rsa_padding_add_PKCS1_type_2(buf, rsa_size, in, in_len);

      break;

    case RSA_PKCS1_OAEP_PADDING:

      // Use the default parameters: SHA-1 for both hashes and no label.

      i = RSA_padding_add_PKCS1_OAEP_mgf1(buf, rsa_size, in, in_len, nullptr, 0,

                                          nullptr, nullptr);

      break;

    case RSA_NO_PADDING:

      i = RSA_padding_add_none(buf, rsa_size, in, in_len);

      break;

    default:

      OPENSSL_PUT_ERROR(RSA, RSA_R_UNKNOWN_PADDING_TYPE);

      goto err;

  }

  if (i <= 0) {

    goto err;

  }

  if (BN_bin2bn(buf, rsa_size, f) == nullptr) {

    goto err;

  }

  if (BN_ucmp(f, rsa->n) >= 0) {

    // usually the padding functions would catch this

    OPENSSL_PUT_ERROR(RSA, RSA_R_DATA_TOO_LARGE_FOR_MODULUS);

    goto err;

  }

  if (!BN_MONT_CTX_set_locked(&rsa->mont_n, &rsa->lock, rsa->n, ctx.get()) ||

      !BN_mod_exp_mont(result, f, rsa->e, &rsa->mont_n->N, ctx.get(),

                       rsa->mont_n)) {

    goto err;

  }

  // put in leading 0 bytes if the number is less than the length of the

  // modulus

  if (!BN_bn2bin_padded(out, rsa_size, result)) {

    OPENSSL_PUT_ERROR(RSA, ERR_R_INTERNAL_ERROR);

    goto err;

  }

  *out_len = rsa_size;

  ret = 1;

err:

  OPENSSL_free(buf);

  return ret;

}

static int rsa_default_decrypt(RSA *rsa, size_t *out_len, uint8_t *out,

                               size_t max_out, const uint8_t *in, size_t in_len,

                               int padding) {

  const unsigned rsa_size = RSA_size(rsa);

  uint8_t *buf = NULL;

  int ret = 0;

  if (max_out < rsa_size) {

    OPENSSL_PUT_ERROR(RSA, RSA_R_OUTPUT_BUFFER_TOO_SMALL);

    return 0;

  }

  if (padding == RSA_NO_PADDING) {

    buf = out;

  } else {

    // Allocate a temporary buffer to hold the padded plaintext.

    buf = reinterpret_cast<uint8_t *>(OPENSSL_malloc(rsa_size));

    if (buf == NULL) {

      goto err;

    }

  }

  if (in_len != rsa_size) {

    OPENSSL_PUT_ERROR(RSA, RSA_R_DATA_LEN_NOT_EQUAL_TO_MOD_LEN);

    goto err;

  }

  if (!rsa_private_transform(rsa, buf, in, rsa_size)) {

    goto err;

  }

  switch (padding) {

    case RSA_PKCS1_PADDING:

      ret =

          rsa_padding_check_PKCS1_type_2(out, out_len, rsa_size, buf, rsa_size);

      break;

    case RSA_PKCS1_OAEP_PADDING:

      // Use the default parameters: SHA-1 for both hashes and no label.

      ret = RSA_padding_check_PKCS1_OAEP_mgf1(out, out_len, rsa_size, buf,

                                              rsa_size, NULL, 0, NULL, NULL);

      break;

    case RSA_NO_PADDING:

      *out_len = rsa_size;

      ret = 1;

      break;

    default:

      OPENSSL_PUT_ERROR(RSA, RSA_R_UNKNOWN_PADDING_TYPE);

      goto err;

  }

  CONSTTIME_DECLASSIFY(&ret, sizeof(ret));

  if (!ret) {

    OPENSSL_PUT_ERROR(RSA, RSA_R_PADDING_CHECK_FAILED);

  } else {

    CONSTTIME_DECLASSIFY(out, *out_len);

  }

err:

  if (padding != RSA_NO_PADDING) {

    OPENSSL_free(buf);

  }

  return ret;

}

int RSA_decrypt(RSA *rsa, size_t *out_len, uint8_t *out, size_t max_out,

                const uint8_t *in, size_t in_len, int padding) {

  if (rsa->meth->decrypt) {

    return rsa->meth->decrypt(rsa, out_len, out, max_out, in, in_len, padding);

  }

  return rsa_default_decrypt(rsa, out_len, out, max_out, in, in_len, padding);

}

int RSA_private_decrypt(size_t flen, const uint8_t *from, uint8_t *to, RSA *rsa,

                        int padding) {

  size_t out_len;

  if (!RSA_decrypt(rsa, &out_len, to, RSA_size(rsa), from, flen, padding)) {

    return -1;

  }

  if (out_len > INT_MAX) {

    OPENSSL_PUT_ERROR(RSA, ERR_R_OVERFLOW);

    return -1;

  }

  return (int)out_len;

}

int RSA_public_decrypt(size_t flen, const uint8_t *from, uint8_t *to, RSA *rsa,

                       int padding) {

  size_t out_len;

  if (!RSA_verify_raw(rsa, &out_len, to, RSA_size(rsa), from, flen, padding)) {

    return -1;

  }

  if (out_len > INT_MAX) {

    OPENSSL_PUT_ERROR(RSA, ERR_R_OVERFLOW);

    return -1;

  }

  return (int)out_len;

}