Expose HMAC digestLength where available

TunnelKit/Sources/Core/CryptoAEAD.m

@@ -97,6 +97,11 @@ const NSInteger CryptoAEADTagLength     = 16;
     self.cipher = NULL;
 }
 
+- (int)digestLength
+{
+    return 0;
+}
+
 #pragma mark Encrypter
 
 - (void)configureEncryptionWithCipherKey:(ZeroingData *)cipherKey hmacKey:(ZeroingData *)hmacKey

TunnelKit/Sources/Core/CryptoBox.h

@@ -68,4 +68,6 @@
 - (nonnull id<Encrypter>)encrypter;
 - (nonnull id<Decrypter>)decrypter;
 
+- (NSInteger)digestLength;
+
 @end

TunnelKit/Sources/Core/CryptoBox.m

@@ -50,6 +50,7 @@
 
 @property (nonatomic, strong) NSString *cipherAlgorithm;
 @property (nonatomic, strong) NSString *digestAlgorithm;
+@property (nonatomic, assign) NSInteger digestLength;
 
 @property (nonatomic, strong) id<Encrypter> encrypter;
 @property (nonatomic, strong) id<Decrypter> decrypter;
@@ -131,6 +132,9 @@
     [self.encrypter configureEncryptionWithCipherKey:cipherEncKey hmacKey:hmacEncKey];
     [self.decrypter configureDecryptionWithCipherKey:cipherDecKey hmacKey:hmacDecKey];
 
+    NSAssert(self.encrypter.digestLength == self.decrypter.digestLength, @"Digest length mismatch in encrypter/decrypter");
+    self.digestLength = self.encrypter.digestLength;
+
     return YES;
 }
 

TunnelKit/Sources/Core/Encryption.h

@@ -45,6 +45,7 @@
 @protocol Encrypter
 
 - (void)configureEncryptionWithCipherKey:(nonnull ZeroingData *)cipherKey hmacKey:(nonnull ZeroingData *)hmacKey;
+- (int)digestLength;
 - (int)overheadLength;
 - (int)extraLength;
 
@@ -59,6 +60,7 @@
 @protocol Decrypter
 
 - (void)configureDecryptionWithCipherKey:(nonnull ZeroingData *)cipherKey hmacKey:(nonnull ZeroingData *)hmacKey;
+- (int)digestLength;
 - (int)overheadLength;
 - (int)extraLength;