ObjFW  Check-in [c55c5dff51]

/*!
 * @class OFHMAC OFHMAC.h ObjFW/OFHMAC.h
 *
 * @brief A class which provides methods to calculate an HMAC.
 */
@interface OFHMAC: OFObject
{
	Class <OFCryptoHash> _hashClass;
	id <OFCryptoHash> _outerHash, _innerHash;
	id <OFCryptoHash> _outerHashCopy, _innerHashCopy;
	bool _keySet, _calculated;
	bool _calculated;
}

/*! The class for the cryptographic hash used by the HMAC. */
@property (assign, readonly) Class <OFCryptoHash> hashClass;

/*!
 * @brief Returns a new OFHMAC with the specified hashing algorithm.
 *
 * @param class The class of the hashing algorithm
 * @return A new, autoreleased OFHMAC
 */

 * @return An initialized OFHMAC
 */
- initWithHashClass: (Class <OFCryptoHash>)class;

/*!
 * @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 Returns the size of the digest.
 *
 * @return The size of the digest.
 */
- (size_t)digestSize;

/*!
 * @brief Resets all state so that a new HMAC can be calculated.
 * @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;
@end

OF_ASSUME_NONNULL_END

#import "OFHMAC.h"

#import "OFHashAlreadyCalculatedException.h"
#import "OFInvalidArgumentException.h"

@implementation OFHMAC
@synthesize hashClass = _hashClass;

+ (instancetype)HMACWithHashClass: (Class <OFCryptoHash>)class
{
	return [[[self alloc] initWithHashClass: class] autorelease];
}

- initWithHashClass: (id <OFCryptoHash>)class
- initWithHashClass: (Class <OFCryptoHash>)class
{
	self = [super init];

	@try {
		void *pool = objc_autoreleasePoolPush();

	_hashClass = class;
		_outerHash = [[class cryptoHash] retain];
		_innerHash = [[class cryptoHash] retain];

		objc_autoreleasePoolPop(pool);
	} @catch (id e) {
		[self release];
		@throw e;
	}

	return self;
}

- (void)dealloc
{
	[_outerHash release];
	[_innerHash release];
	[_outerHashCopy release];
	[_innerHashCopy release];

	[super dealloc];
}

- (void)setKey: (const void*)key
	length: (size_t)length
{
	void *pool = objc_autoreleasePoolPush();
	size_t blockSize = [[_outerHash class] blockSize];
	size_t blockSize = [_hashClass blockSize];
	uint8_t outerKeyPad[blockSize], innerKeyPad[blockSize];

	[_outerHash release];
	[_innerHash release];
	[_outerHashCopy release];
	[_innerHashCopy release];
	_outerHash = _innerHash = _outerHashCopy = _innerHashCopy = nil;

	if (length > blockSize) {
		void *pool = objc_autoreleasePoolPush();
		id <OFCryptoHash> hash = [[_outerHash class] cryptoHash];
		id <OFCryptoHash> hash = [_hashClass cryptoHash];

		[hash updateWithBuffer: key
				length: length];

		length = [[hash class] digestSize];
		length = [_hashClass digestSize];
		if OF_UNLIKELY (length > blockSize)
			length = blockSize;

		memcpy(outerKeyPad, [hash digest], length);
		memcpy(innerKeyPad, [hash digest], length);

		objc_autoreleasePoolPop(pool);
	} else {
		memcpy(outerKeyPad, key, length);
		memcpy(innerKeyPad, key, length);
	}

	memset(outerKeyPad + length, 0, blockSize - length);
	memset(innerKeyPad + length, 0, blockSize - length);

	for (size_t i = 0; i < blockSize; i++) {
		outerKeyPad[i] ^= 0x5C;
		innerKeyPad[i] ^= 0x36;
	}

	_outerHash = [[_hashClass cryptoHash] retain];
	_innerHash = [[_hashClass cryptoHash] retain];

	[_outerHash updateWithBuffer: outerKeyPad
			      length: blockSize];
	[_innerHash updateWithBuffer: innerKeyPad
			      length: blockSize];

	objc_autoreleasePoolPop(pool);
	_keySet = true;

	_outerHashCopy = [_outerHash copy];
	_innerHashCopy = [_innerHash copy];

	_calculated = false;
}

- (void)updateWithBuffer: (const void*)buffer
		  length: (size_t)length
{
	if (!_keySet)
	if (_innerHash == nil)
		@throw [OFInvalidArgumentException exception];

	if (_calculated)
		@throw [OFHashAlreadyCalculatedException
		    exceptionWithObject: self];

	[_innerHash updateWithBuffer: buffer
			      length: length];
}

- (const unsigned char*)digest
{
	if (_outerHash == nil || _innerHash == nil)
		@throw [OFInvalidArgumentException exception];

	if (_calculated)
		return [_outerHash digest];

	[_outerHash updateWithBuffer: [_innerHash digest]
			      length: [[_innerHash class] digestSize]];
			      length: [_hashClass digestSize]];
	_calculated = true;

	return [_outerHash digest];
}

- (size_t)digestSize
{
	return [[_outerHash class] digestSize];
	return [_hashClass digestSize];
}

- (void)reset
{
	[_outerHash reset];
	[_innerHash reset];
	[_outerHash release];
	[_innerHash release];
	_outerHash = _innerHash = nil;

	_outerHash = [_outerHashCopy copy];
	_innerHash = [_innerHashCopy copy];
	_keySet = false;

	_calculated = false;
}
@end