/*
* Copyright (c) 2008-2024 Jonathan Schleifer <js@nil.im>
*
* All rights reserved.
*
* This program is free software: you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License version 3.0 only,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* version 3.0 for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* version 3.0 along with this program. If not, see
* <https://www.gnu.org/licenses/>.
*/
#import "OFObject.h"
#import "OFCryptographicHash.h"
OF_ASSUME_NONNULL_BEGIN
/**
* @class OFHMAC OFHMAC.h ObjFW/OFHMAC.h
*
* @brief A class which provides methods to calculate an HMAC.
*/
OF_SUBCLASSING_RESTRICTED
@interface OFHMAC: OFObject
{
Class <OFCryptographicHash> _hashClass;
bool _allowsSwappableMemory;
id <OFCryptographicHash> _Nullable _outerHash, _innerHash;
id <OFCryptographicHash> _Nullable _outerHashCopy, _innerHashCopy;
bool _calculated;
}
/**
* @brief The class for the cryptographic hash used by the HMAC.
*/
@property (readonly, nonatomic) Class <OFCryptographicHash> hashClass;
/**
* @brief Whether data may be stored in swappable memory.
*/
@property (readonly, nonatomic) bool allowsSwappableMemory;
/**
* @brief A buffer containing the HMAC.
*
* The size of the buffer depends on the hash used. The buffer is part of the
* receiver's memory pool.
*
* @throw OFHashNotCalculatedException The HMAC hasn't been calculated yet
*/
@property (readonly, nonatomic) const unsigned char *digest
OF_RETURNS_INNER_POINTER;
/**
* @brief The size of the digest.
*/
@property (readonly, nonatomic) size_t digestSize;
/**
* @brief Returns a new OFHMAC with the specified hashing algorithm.
*
* @param hashClass The class of the hashing algorithm
* @param allowsSwappableMemory Whether data may be stored in swappable memory
* @return A new, autoreleased OFHMAC
*/
+ (instancetype)HMACWithHashClass: (Class <OFCryptographicHash>)hashClass
allowsSwappableMemory: (bool)allowsSwappableMemory;
- (instancetype)init OF_UNAVAILABLE;
/**
* @brief Initialized an already allocated OFHMAC with the specified hashing
* algorithm.
*
* @param hashClass The class of the hashing algorithm
* @param allowsSwappableMemory Whether data may be stored in swappable memory
* @return An initialized OFHMAC
*/
- (instancetype)initWithHashClass: (Class <OFCryptographicHash>)hashClass
allowsSwappableMemory: (bool)allowsSwappableMemory
OF_DESIGNATED_INITIALIZER;
/**
* @brief Sets the key for the HMAC.
*
* @note This resets the HMAC!
*
* @warning This invalidates any pointer previously returned by @ref digest. If
* you are still interested in the previous digest, you need to memcpy
* it yourself before calling @ref setKey:length:!
*
* @param key The key for the HMAC
* @param length The length of the key for the HMAC
*/
- (void)setKey: (const void *)key length: (size_t)length;
/**
* @brief Adds a buffer to the HMAC to be calculated.
*
* @param buffer The buffer which should be included into the calculation
* @param length The length of the buffer
* @throw OFHashAlreadyCalculatedException The HMAC has already been calculated
*/
- (void)updateWithBuffer: (const void *)buffer length: (size_t)length;
/**
* @brief Performs the final calculation of the HMAC.
*
* @throw OFHashAlreadyCalculatedException The HMAC has already been calculated
*/
- (void)calculate;
/**
* @brief Resets the HMAC so that it can be calculated for a new message.
*
* @note This does not reset the key so that a new HMAC with the same key can
* be calculated efficiently. If you want to reset both, use
* @ref setKey:length:.
*
* @warning This invalidates any pointer previously returned by @ref digest. If
* you are still interested in the previous digest, you need to memcpy
* it yourself before calling @ref reset!
*/
- (void)reset;
/**
* @brief This is like @ref reset, but also zeroes the hashed key and all state.
*
* @warning After calling this, you *must* set a new key before reusing the
* HMAC!
*/
- (void)zero;
@end
OF_ASSUME_NONNULL_END