3 files changed, 63 insertions, 1 deletions

diff --git a/xcode/OLMKit/OLMSAS.h b/xcode/OLMKit/OLMSAS.h
index 454c8e0..3785b03 100644
--- a/xcode/OLMKit/OLMSAS.h
+++ b/xcode/OLMKit/OLMSAS.h
@@ -52,7 +52,18 @@ NS_ASSUME_NONNULL_BEGIN
  @param error the error if any.
  @return the MAC.
  */
-- (NSString *)calculateMac:(NSString*)input info:(NSString*)info error:(NSError* _Nullable *)error; // TODO: NSError?
+- (NSString *)calculateMac:(NSString*)input info:(NSString*)info error:(NSError* _Nullable *)error;
+
+/**
+ Generate a message authentication code (MAC) based on the shared secret.
+ For compatibility with an old version of olm.js.
+
+ @param input the message to produce the authentication code for.
+ @param info extra information to mix in when generating the MAC, as per the Matrix spec.
+ @param error the error if any.
+ @return the MAC.
+ */
+- (NSString *)calculateMacLongKdf:(NSString*)input info:(NSString*)info error:(NSError* _Nullable *)error;
 
 @end
 
diff --git a/xcode/OLMKit/OLMSAS.m b/xcode/OLMKit/OLMSAS.m
index d95f948..fed370b 100644
--- a/xcode/OLMKit/OLMSAS.m
+++ b/xcode/OLMKit/OLMSAS.m
@@ -137,4 +137,38 @@
     return mac;
 }
 
+- (NSString *)calculateMacLongKdf:(NSString *)input info:(NSString *)info error:(NSError *__autoreleasing  _Nullable *)error {
+    NSMutableData *inputData = [input dataUsingEncoding:NSUTF8StringEncoding].mutableCopy;
+    NSData *infoData = [info dataUsingEncoding:NSUTF8StringEncoding];
+
+    size_t macLength = olm_sas_mac_length(olmSAS);
+    NSMutableData *macData = [NSMutableData dataWithLength:macLength];
+    if (!macData) {
+        return nil;
+    }
+
+    size_t result = olm_sas_calculate_mac_long_kdf(olmSAS,
+                                                   inputData.mutableBytes, inputData.length,
+                                                   infoData.bytes, infoData.length,
+                                                   macData.mutableBytes, macLength);
+    if (result == olm_error()) {
+        const char *olm_error = olm_sas_last_error(olmSAS);
+        NSLog(@"[OLMSAS] calculateMacLongKdf: olm_sas_calculate_mac error: %s", olm_error);
+
+        NSString *errorString = [NSString stringWithUTF8String:olm_error];
+        if (error && olm_error && errorString) {
+            *error = [NSError errorWithDomain:OLMErrorDomain
+                                         code:0
+                                     userInfo:@{
+                                                NSLocalizedDescriptionKey: errorString,
+                                                NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:@"olm_sas_calculate_mac_long_kdf error: %@", errorString]
+                                                }];
+        }
+        return nil;
+    }
+
+    NSString *mac = [[NSString alloc] initWithData:macData encoding:NSUTF8StringEncoding];
+    return mac;
+}
+
 @end
diff --git a/xcode/OLMKitTests/OLMKitSASTests.m b/xcode/OLMKitTests/OLMKitSASTests.m
index 08a2490..e250a67 100644
--- a/xcode/OLMKitTests/OLMKitSASTests.m
+++ b/xcode/OLMKitTests/OLMKitSASTests.m
@@ -66,4 +66,21 @@
     XCTAssertNil(bobError);
 }
 
+- (void)testMACLongKdfsMatch {
+    [alice setTheirPublicKey:bob.publicKey];
+    [bob setTheirPublicKey:alice.publicKey];
+
+    NSString *string = @"test";
+    NSString *info = @"MAC";
+
+    NSError *aliceError, *bobError;
+    XCTAssertEqualObjects([alice calculateMacLongKdf:string info:info error:&aliceError],
+                          [bob calculateMacLongKdf:string info:info error:&bobError]);
+    XCTAssertNotEqualObjects([alice calculateMacLongKdf:string info:info error:&aliceError],
+                             [bob calculateMac:string info:info error:&bobError]);
+    XCTAssertNil(aliceError);
+    XCTAssertNil(bobError);
+}
+
+
 @end