Function decrypt

libcppcryptfs/crypt/crypt.cpp:143–205

}

int decrypt(const unsigned char *ciphertext, int ciphertext_len, unsigned char *aad,
	int aad_len, unsigned char *tag, const unsigned char *key, const unsigned char *iv, 
	unsigned char *plaintext, EVP_CIPHER_CTX* ctx)
{	

	if (!ctx)
		return -1;

	int len;
	int plaintext_len;
	int ret;

	

	try {

		
		/* Initialise Key and IV */
		if (!EVP_DecryptInit_ex(ctx, NULL, NULL, key, iv)) handleErrors();

		/* Provide any AAD data. This can be called zero or more times as
		* required
		*/
		if (!EVP_DecryptUpdate(ctx, NULL, &len, aad, aad_len))
			handleErrors();

		/* Provide the message to be decrypted, and obtain the plaintext output.
		* EVP_DecryptUpdate can be called multiple times if necessary
		*/
		if (!EVP_DecryptUpdate(ctx, plaintext, &len, ciphertext, ciphertext_len))
			handleErrors();
		plaintext_len = len;

		/* Set expected tag value. Works in OpenSSL 1.0.1d and later */
		if (tag) {
			if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, 16, tag))
				handleErrors();
		}

		/* Finalise the decryption. A positive return value indicates success,
		* anything else is a failure - the plaintext is not trustworthy.
		*/
		ret = EVP_DecryptFinal_ex(ctx, plaintext + len, &len);

	}
	catch (int) {
		ret = -1;
	}

	

	if (ret > 0)
	{
		/* Success */
		plaintext_len += len;
		return plaintext_len;
	}
	else