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// OpenVPN -- An application to securely tunnel IP networks
// over a single port, with support for SSL/TLS-based
// session authentication and key exchange,
// packet encryption, packet authentication, and
// packet compression.
//
// Copyright (C) 2012- OpenVPN Inc.
//
// SPDX-License-Identifier: MPL-2.0 OR AGPL-3.0-only WITH openvpn3-openssl-exception
//
// Wrap the mbed TLS AEAD API.
#pragma once
#include <string>
#include <mbedtls/gcm.h>
#include <openvpn/common/size.hpp>
#include <openvpn/common/exception.hpp>
#include <openvpn/common/likely.hpp>
#include <openvpn/crypto/static_key.hpp>
#include <openvpn/crypto/cryptoalgs.hpp>
#include <openvpn/crypto/aead_usage_limit.hpp>
#include <openvpn/mbedtls/crypto/cipher.hpp>
namespace openvpn::MbedTLSCrypto {
class CipherContextAEAD : public CipherContextCommon
{
public:
OPENVPN_EXCEPTION(mbedtls_aead_error);
// mbed TLS cipher constants
enum
{
IV_LEN = 12,
AUTH_TAG_LEN = 16
};
#if 0
// mbed TLS encrypt/decrypt return values
enum {
GCM_AUTH_FAILED = MBEDTLS_ERR_GCM_AUTH_FAILED,
SUCCESS = 0,
};
#endif
CipherContextAEAD() = default;
~CipherContextAEAD()
{
erase();
}
CipherContextAEAD(CipherContextAEAD &&other) noexcept
: CipherContextCommon(std::move(other)), aead_usage_limit_(other.aead_usage_limit_)
{
}
CipherContextAEAD &operator=(CipherContextAEAD &&other)
{
CipherContextAEAD temp(std::move(other));
ctx = temp.ctx;
initialized = temp.initialized;
temp.ctx = {};
temp.initialized = false;
aead_usage_limit_ = temp.aead_usage_limit_;
return *this;
}
void init(SSLLib::Ctx libctx,
const CryptoAlgs::Type alg,
const unsigned char *key,
const unsigned int keysize,
const int mode)
{
erase();
check_mode(mode);
// get cipher type
unsigned int ckeysz = 0;
const mbedtls_cipher_type_t cid = cipher_type(alg, ckeysz);
if (cid == MBEDTLS_CIPHER_NONE)
OPENVPN_THROW(mbedtls_aead_error, CryptoAlgs::name(alg) << ": not usable");
if (ckeysz > keysize)
throw mbedtls_aead_error("insufficient key material");
auto *ci = mbedtls_cipher_info_from_type(cid);
// initialize cipher context with cipher type
if (mbedtls_cipher_setup(&ctx, ci) < 0)
throw mbedtls_aead_error("mbedtls_cipher_setup");
if (mbedtls_cipher_setkey(&ctx, key, ckeysz * 8, (mbedtls_operation_t)mode) < 0)
throw mbedtls_aead_error("mbedtls_cipher_setkey");
aead_usage_limit_ = {alg};
initialized = true;
}
void encrypt(const unsigned char *input,
unsigned char *output,
size_t length,
const unsigned char *iv,
unsigned char *tag,
const unsigned char *ad,
size_t ad_len)
{
check_initialized();
const int status = mbedtls_cipher_auth_encrypt_ext(&ctx,
iv,
IV_LEN,
ad,
ad_len,
input,
length,
output,
length + AUTH_TAG_LEN,
&length,
AUTH_TAG_LEN);
if (unlikely(status))
OPENVPN_THROW(mbedtls_aead_error, "mbedtls_cipher_auth_encrypt failed with status=" << status);
aead_usage_limit_.update(length + ad_len);
}
/** Returns the AEAD usage limit associated with this AEAD cipher instance to check the limits */
[[nodiscard]] const Crypto::AEADUsageLimit &get_usage_limit()
{
return aead_usage_limit_;
}
/**
* Decrypts AEAD encrypted data. Note that this method ignores the tag parameter
* and the tag is assumed to be part of input and at the end of the input.
*
* @param input Input data to decrypt
* @param output Where decrypted data will be written to
* @param iv IV of the encrypted data.
* @param length length the of the data, this includes the tag at the end.
* @param ad start of the additional data
* @param ad_len length of the additional data
* @param tag ignored by the mbed TLS variant of the method. (see OpenSSL variant of the method for more details).
*
* input and output may NOT be equal
*/
bool decrypt(const unsigned char *input,
unsigned char *output,
size_t length,
const unsigned char *iv,
const unsigned char *tag,
const unsigned char *ad,
size_t ad_len)
{
check_initialized();
if (unlikely(tag != nullptr))
{
/* If we are called with a non-null tag, the function is not going to be able to decrypt */
throw mbedtls_aead_error("tag must be null for aead decrypt");
}
size_t olen;
const int status = mbedtls_cipher_auth_decrypt_ext(&ctx,
iv,
IV_LEN,
ad,
ad_len,
input,
length,
output,
length - AUTH_TAG_LEN,
&olen,
AUTH_TAG_LEN);
return (olen == length - AUTH_TAG_LEN) && (status == 0);
}
bool is_initialized() const
{
return initialized;
}
static bool is_supported(void *libctx, const CryptoAlgs::Type alg)
{
unsigned int keysize;
return (cipher_type(alg, keysize) != MBEDTLS_CIPHER_NONE);
}
private:
Crypto::AEADUsageLimit aead_usage_limit_ = {};
static mbedtls_cipher_type_t cipher_type(const CryptoAlgs::Type alg, unsigned int &keysize)
{
switch (alg)
{
case CryptoAlgs::AES_128_GCM:
keysize = 16;
return MBEDTLS_CIPHER_AES_128_GCM;
case CryptoAlgs::AES_192_GCM:
keysize = 24;
return MBEDTLS_CIPHER_AES_192_GCM;
case CryptoAlgs::AES_256_GCM:
keysize = 32;
return MBEDTLS_CIPHER_AES_256_GCM;
#ifdef MBEDTLS_CHACHAPOLY_C
case CryptoAlgs::CHACHA20_POLY1305:
keysize = 32;
return MBEDTLS_CIPHER_CHACHA20_POLY1305;
#endif
default:
keysize = 0;
return MBEDTLS_CIPHER_NONE;
}
}
};
} // namespace openvpn::MbedTLSCrypto
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