Method decrypt_impl

src/dpp/dave/decryptor.cpp:142–180

}

bool decryptor::decrypt_impl(aead_cipher_manager& cipher_manager, media_type this_media_type, inbound_frame_processor& encrypted_frame, array_view<uint8_t> frame)
{
	auto tag = encrypted_frame.get_tag();
	auto truncated_nonce = encrypted_frame.get_truncated_nonce();
	auto authenticated_data = encrypted_frame.get_authenticated_data();
	auto ciphertext_buffer = encrypted_frame.get_ciphertext();
	auto plaintext = encrypted_frame.get_plaintext();

	// expand the truncated nonce to the full sized one needed for decryption
	auto nonce_buffer = std::array<uint8_t, AES_GCM_128_NONCE_BYTES>();
	memcpy(nonce_buffer.data() + AES_GCM_128_TRUNCATED_SYNC_NONCE_OFFSET, &truncated_nonce, AES_GCM_128_TRUNCATED_SYNC_NONCE_BYTES);

	auto nonce_buffer_view = make_array_view<const uint8_t>(nonce_buffer.data(), nonce_buffer.size());

	auto generation = cipher_manager.compute_wrapped_generation(truncated_nonce >> RATCHET_GENERATION_SHIFT_BITS);

	if (!cipher_manager.can_process_nonce(generation, truncated_nonce)) {
		creator.log(dpp::ll_trace, "decrypt failed, cannot process nonce");
		return false;
	}

	// Get the cryptor for this generation
	cipher_interface* cipher = cipher_manager.get_cipher(generation);

	if (cipher == nullptr) {
		creator.log(dpp::ll_warning, "decrypt failed, no cryptor found for generation: " + std::to_string(generation));
		return false;
	}

	// perform the decryption
	bool success = cipher->decrypt(plaintext, ciphertext_buffer, tag, nonce_buffer_view, authenticated_data);
	stats[this_media_type].decrypt_attempts++;

	if (success) {
		cipher_manager.report_cipher_success(generation, truncated_nonce);
	}

	return success;
}

size_t decryptor::get_max_plaintext_byte_size(media_type this_media_type, size_t encrypted_frame_size)
{