// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "net/quic/crypto/aead_base_encrypter.h"

#include <pk11pub.h>

#include "base/memory/scoped_ptr.h"
#include "crypto/scoped_nss_types.h"

using base::StringPiece;

namespace net {

AeadBaseEncrypter::AeadBaseEncrypter(CK_MECHANISM_TYPE aead_mechanism,
                                     PK11_EncryptFunction pk11_encrypt,
                                     size_t key_size,
                                     size_t auth_tag_size,
                                     size_t nonce_prefix_size)
    : aead_mechanism_(aead_mechanism),
      pk11_encrypt_(pk11_encrypt),
      key_size_(key_size),
      auth_tag_size_(auth_tag_size),
      nonce_prefix_size_(nonce_prefix_size) {
  DCHECK_LE(key_size_, sizeof(key_));
  DCHECK_LE(nonce_prefix_size_, sizeof(nonce_prefix_));
}

AeadBaseEncrypter::~AeadBaseEncrypter() {}

bool AeadBaseEncrypter::SetKey(StringPiece key) {
  DCHECK_EQ(key.size(), key_size_);
  if (key.size() != key_size_) {
    return false;
  }
  memcpy(key_, key.data(), key.size());
  return true;
}

bool AeadBaseEncrypter::SetNoncePrefix(StringPiece nonce_prefix) {
  DCHECK_EQ(nonce_prefix.size(), nonce_prefix_size_);
  if (nonce_prefix.size() != nonce_prefix_size_) {
    return false;
  }
  memcpy(nonce_prefix_, nonce_prefix.data(), nonce_prefix.size());
  return true;
}

bool AeadBaseEncrypter::Encrypt(StringPiece nonce,
                                StringPiece associated_data,
                                StringPiece plaintext,
                                unsigned char* output) {
  if (nonce.size() != nonce_prefix_size_ + sizeof(QuicPacketSequenceNumber)) {
    return false;
  }

  size_t ciphertext_size = GetCiphertextSize(plaintext.length());

  // Import key_ into NSS.
  SECItem key_item;
  key_item.type = siBuffer;
  key_item.data = key_;
  key_item.len = key_size_;
  PK11SlotInfo* slot = PK11_GetInternalSlot();

  // TODO(wtc): For an AES-GCM key, the correct value for |key_mechanism| is
  // CKM_AES_GCM, but because of NSS bug
  // https://bugzilla.mozilla.org/show_bug.cgi?id=853285, use CKM_AES_ECB as a
  // workaround. Remove this when we require NSS 3.15.
  CK_MECHANISM_TYPE key_mechanism = aead_mechanism_;
  if (key_mechanism == CKM_AES_GCM) {
    key_mechanism = CKM_AES_ECB;
  }

  // The exact value of the |origin| argument doesn't matter to NSS as long as
  // it's not PK11_OriginFortezzaHack, so we pass PK11_OriginUnwrap as a
  // placeholder.
  crypto::ScopedPK11SymKey aead_key(PK11_ImportSymKey(
      slot, key_mechanism, PK11_OriginUnwrap, CKA_ENCRYPT, &key_item, nullptr));
  PK11_FreeSlot(slot);
  slot = nullptr;
  if (!aead_key) {
    DVLOG(1) << "PK11_ImportSymKey failed";
    return false;
  }

  AeadParams aead_params = {0};
  FillAeadParams(nonce, associated_data, auth_tag_size_, &aead_params);

  SECItem param;
  param.type = siBuffer;
  param.data = reinterpret_cast<unsigned char*>(&aead_params.data);
  param.len = aead_params.len;

  unsigned int output_len;
  if (pk11_encrypt_(aead_key.get(), aead_mechanism_, &param,
                    output, &output_len, ciphertext_size,
                    reinterpret_cast<const unsigned char*>(plaintext.data()),
                    plaintext.size()) != SECSuccess) {
    DVLOG(1) << "pk11_encrypt_ failed";
    return false;
  }

  if (output_len != ciphertext_size) {
    DVLOG(1) << "Wrong output length";
    return false;
  }

  return true;
}

bool AeadBaseEncrypter::EncryptPacket(QuicPacketSequenceNumber sequence_number,
                                      StringPiece associated_data,
                                      StringPiece plaintext,
                                      char* output,
                                      size_t* output_length,
                                      size_t max_output_length) {
  size_t ciphertext_size = GetCiphertextSize(plaintext.length());
  if (max_output_length < ciphertext_size) {
    return false;
  }
  // TODO(ianswett): Introduce a check to ensure that we don't encrypt with the
  // same sequence number twice.
  const size_t nonce_size = nonce_prefix_size_ + sizeof(sequence_number);
  memcpy(output, nonce_prefix_, nonce_prefix_size_);
  memcpy(output + nonce_prefix_size_, &sequence_number,
         sizeof(sequence_number));
  if (!Encrypt(StringPiece(output, nonce_size), associated_data, plaintext,
               reinterpret_cast<unsigned char*>(output))) {
    return false;
  }
  *output_length = ciphertext_size;
  return true;
}

size_t AeadBaseEncrypter::GetKeySize() const { return key_size_; }

size_t AeadBaseEncrypter::GetNoncePrefixSize() const {
  return nonce_prefix_size_;
}

size_t AeadBaseEncrypter::GetMaxPlaintextSize(size_t ciphertext_size) const {
  return ciphertext_size - auth_tag_size_;
}

size_t AeadBaseEncrypter::GetCiphertextSize(size_t plaintext_size) const {
  return plaintext_size + auth_tag_size_;
}

StringPiece AeadBaseEncrypter::GetKey() const {
  return StringPiece(reinterpret_cast<const char*>(key_), key_size_);
}

StringPiece AeadBaseEncrypter::GetNoncePrefix() const {
  if (nonce_prefix_size_ == 0) {
    return StringPiece();
  }
  return StringPiece(reinterpret_cast<const char*>(nonce_prefix_),
                     nonce_prefix_size_);
}

}  // namespace net