Added receipt validation check

Author: nsingh-branch

BranchSDK/BNCAppleReceipt.h

@@ -21,6 +21,7 @@ NS_ASSUME_NONNULL_BEGIN
 // this is only available on builds from Apple
 - (nullable NSString *)installReceipt;
 - (BOOL)isTestFlight;
++ (BOOL)isReceiptValid;
 
 @end
 

BranchSDK/BNCAppleReceipt.m

@@ -7,6 +7,7 @@
 //
 
 #import "BNCAppleReceipt.h"
+#import <CommonCrypto/CommonDigest.h>
 
 @interface BNCAppleReceipt()
 
@@ -63,4 +64,30 @@ - (BOOL)isTestFlight {
     return self.isSandboxReceipt;
 }
 
++ (BOOL)isReceiptValid {
+    NSURL *receiptURL = [[NSBundle mainBundle] appStoreReceiptURL];
+    NSData *receiptData = [NSData dataWithContentsOfURL:receiptURL];
+
+    if (!receiptData) {
+        return NO;
+    }
+
+    NSString *receiptHash = [self sha256HashForData:receiptData];
+    if (receiptHash) {
+        return YES;
+    }
+
+    return NO;
+}
+
++ (NSString *)sha256HashForData:(NSData *)data {
+    uint8_t digest[CC_SHA256_DIGEST_LENGTH];
+    CC_SHA256(data.bytes, (CC_LONG)data.length, digest);
+    NSMutableString *output = [NSMutableString stringWithCapacity:CC_SHA256_DIGEST_LENGTH * 2];
+    for (int i = 0; i < CC_SHA256_DIGEST_LENGTH; i++) {
+        [output appendFormat:@"%02x", digest[i]];
+    }
+    return output;
+}
+
 @end

BranchSDK/BranchEvent.m

@@ -16,6 +16,7 @@
 #import "BNCPartnerParameters.h"
 #import "BNCPreferenceHelper.h"
 #import "BNCEventUtils.h"
+#import "BNCAppleReceipt.h"
 
 #pragma mark BranchStandardEvents
 
@@ -372,16 +373,19 @@ - (NSString*_Nonnull) description {
 #pragma mark - IAP Methods
 
 - (void) logEventWithTransaction:(SKPaymentTransaction *)transaction {
-    
-    self.transactionID = transaction.transactionIdentifier;
-    [[BNCEventUtils shared] storeEvent:self];
-
-    NSString *productId = transaction.payment.productIdentifier;
-    SKProductsRequest *productsRequest = [[SKProductsRequest alloc] initWithProductIdentifiers:[NSSet setWithObject:productId]];
-    
-    _request = productsRequest;
-    productsRequest.delegate = self;
-    [productsRequest start];
+    if ([BNCAppleReceipt isReceiptValid]) {
+        self.transactionID = transaction.transactionIdentifier;
+        [[BNCEventUtils shared] storeEvent:self];
+        
+        NSString *productId = transaction.payment.productIdentifier;
+        SKProductsRequest *productsRequest = [[SKProductsRequest alloc] initWithProductIdentifiers:[NSSet setWithObject:productId]];
+        
+        _request = productsRequest;
+        productsRequest.delegate = self;
+        [productsRequest start];
+    } else {
+        BNCLogDebug(@"Invalid receipt. Branch Event was not logged.");
+    }
 }
 
 - (void)productsRequest:(SKProductsRequest *)request didReceiveResponse:(SKProductsResponse *)response {