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97 lines
2.6 KiB
Objective-C
97 lines
2.6 KiB
Objective-C
//
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// Copyright (c) 2018 Open Whisper Systems. All rights reserved.
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//
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#import "ChainKey.h"
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#import "TSDerivedSecrets.h"
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#import <CommonCrypto/CommonCrypto.h>
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#import <Curve25519Kit/Curve25519.h>
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#import <SignalCoreKit/OWSAsserts.h>
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NS_ASSUME_NONNULL_BEGIN
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@implementation ChainKey
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static NSString *const kCoderKey = @"kCoderKey";
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static NSString *const kCoderIndex = @"kCoderIndex";
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#define kTSKeySeedLength 1
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static uint8_t kMessageKeySeed[kTSKeySeedLength] = { 01 };
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static uint8_t kChainKeySeed[kTSKeySeedLength] = { 02 };
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+ (BOOL)supportsSecureCoding
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{
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return YES;
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}
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- (nullable id)initWithCoder:(NSCoder *)aDecoder
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{
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NSData *key = [aDecoder decodeObjectOfClass:[NSData class] forKey:kCoderKey];
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int index = [aDecoder decodeIntForKey:kCoderIndex];
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return [self initWithData:key index:index];
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}
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- (void)encodeWithCoder:(NSCoder *)aCoder
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{
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[aCoder encodeObject:_key forKey:kCoderKey];
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[aCoder encodeInt:_index forKey:kCoderIndex];
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}
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- (instancetype)initWithData:(NSData *)chainKey index:(int)index
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{
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OWSAssert(chainKey.length == 32);
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OWSAssert(index >= 0);
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self = [super init];
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if (self) {
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_key = chainKey;
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_index = index;
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}
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return self;
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}
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- (instancetype)nextChainKey
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{
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NSData *nextCK = [self baseMaterial:[NSData dataWithBytes:kChainKeySeed length:kTSKeySeedLength]];
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OWSAssert(nextCK.length == 32);
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int nextIndex;
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ows_add_overflow(self.index, 1, &nextIndex);
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return [[ChainKey alloc] initWithData:nextCK index:nextIndex];
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}
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- (MessageKeys *)throws_messageKeys
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{
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NSData *inputKeyMaterial = [self baseMaterial:[NSData dataWithBytes:kMessageKeySeed length:kTSKeySeedLength]];
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TSDerivedSecrets *derivedSecrets = [TSDerivedSecrets throws_derivedMessageKeysWithData:inputKeyMaterial];
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return [[MessageKeys alloc] initWithCipherKey:derivedSecrets.cipherKey
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macKey:derivedSecrets.macKey
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iv:derivedSecrets.iv
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index:self.index];
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}
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- (NSData *)baseMaterial:(NSData *)seed
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{
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OWSAssert(self.key);
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OWSAssert(self.key.length == 32);
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OWSAssert(seed);
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OWSAssert(seed.length == kTSKeySeedLength);
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NSMutableData *_Nullable bufferData = [NSMutableData dataWithLength:CC_SHA256_DIGEST_LENGTH];
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OWSAssert(bufferData);
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CCHmacContext ctx;
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CCHmacInit(&ctx, kCCHmacAlgSHA256, [self.key bytes], [self.key length]);
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CCHmacUpdate(&ctx, [seed bytes], [seed length]);
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CCHmacFinal(&ctx, bufferData.mutableBytes);
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return [bufferData copy];
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}
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@end
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NS_ASSUME_NONNULL_END
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