session-ios/tests/CryptographyTests.mm

//
//  CryptographyTests.m
//  TextSecureiOS
//
//  Created by Christine Corbett Moran on 12/19/13.
//  Copyright (c) 2013 Open Whisper Systems. All rights reserved.
//

#import <XCTest/XCTest.h>
#import "Cryptography.h"
#import "NSData+Base64.h"

@interface CryptographyTests : XCTestCase

@end


@interface Cryptography (Test)
+ (NSData *)truncatedSHA256HMAC:(NSData *)dataToHMAC withHMACKey:(NSData *)HMACKey truncation:(int)bytes;
+ (NSData *)encryptCBCMode:(NSData *)dataToEncrypt
                   withKey:(NSData *)key
                    withIV:(NSData *)iv
               withVersion:(NSData *)version
               withHMACKey:(NSData *)hmacKey
              withHMACType:(TSMACType)hmacType
              computedHMAC:(NSData **)hmac;

+ (NSData *)decryptCBCMode:(NSData *)dataToDecrypt
                       key:(NSData *)key
                        IV:(NSData *)iv
                   version:(NSData *)version
                   HMACKey:(NSData *)hmacKey
                  HMACType:(TSMACType)hmacType
              matchingHMAC:(NSData *)hmac;
@end

@implementation CryptographyTests


- (void)testLocalDecryption {
    NSString *originalMessage    = @"Hawaii is awesome";
    NSString *signalingKeyString = @"VJuRzZcwuY/6VjGw+QSPy5ROzHo8xE36mKwHNvkfyZ+mSPaDlSDcenUqavIX1Vwn\nRRIdrg==";
    NSData *signalingKey         = [NSData dataFromBase64String:signalingKeyString];
    XCTAssertTrue([signalingKey length] == 52,
                  @"signaling key is not 52 bytes but %llu",
                  (unsigned long long)[signalingKey length]);
    NSData *signalingKeyAESKeyMaterial  = [signalingKey subdataWithRange:NSMakeRange(0, 32)];
    NSData *signalingKeyHMACKeyMaterial = [signalingKey subdataWithRange:NSMakeRange(32, 20)];
    NSData *iv                          = [Cryptography generateRandomBytes:16];
    NSData *version                     = [Cryptography generateRandomBytes:1];
    NSData *mac;

    NSData *encryption = [Cryptography encryptCBCMode:[originalMessage dataUsingEncoding:NSUTF8StringEncoding]
                                              withKey:signalingKeyAESKeyMaterial
                                               withIV:iv
                                          withVersion:version
                                          withHMACKey:signalingKeyHMACKeyMaterial
                                         withHMACType:TSHMACSHA1Truncated10Bytes
                                         computedHMAC:&mac]; // Encrypt

    NSMutableData *dataToHmac = [NSMutableData data];
    [dataToHmac appendData:version];
    [dataToHmac appendData:iv];
    [dataToHmac appendData:encryption];


    NSData *expectedHmac =
        [Cryptography truncatedSHA1HMAC:dataToHmac withHMACKey:signalingKeyHMACKeyMaterial truncation:10];

    XCTAssertTrue([mac isEqualToData:expectedHmac],
                  @"Hmac of encrypted data %@,  not equal to expected hmac %@",
                  [mac base64EncodedString],
                  [expectedHmac base64EncodedString]);

    NSData *decryption = [Cryptography decryptCBCMode:encryption
                                                  key:signalingKeyAESKeyMaterial
                                                   IV:iv
                                              version:version
                                              HMACKey:signalingKeyHMACKeyMaterial
                                             HMACType:TSHMACSHA1Truncated10Bytes
                                         matchingHMAC:mac];

    NSString *decryptedMessage = [[NSString alloc] initWithData:decryption encoding:NSUTF8StringEncoding];
    XCTAssertTrue([decryptedMessage isEqualToString:originalMessage],
                  @"Decrypted message: %@ is not equal to original: %@",
                  decryptedMessage,
                  originalMessage);
}

@end