From 58339b7c778895b29cb567b72be224667b549d01 Mon Sep 17 00:00:00 2001
From: sid-j <7937756+j-sid@users.noreply.github.com>
Date: Wed, 28 Jul 2021 14:51:33 -0700
Subject: [PATCH] Changed Analytics to use SHA256 from MD5 since MD5 has been
 deprecated from iOS 13. Bumped podspec version.

---
 Classes/GTXAnalyticsUtils.h                  |  5 +++
 Classes/GTXAnalyticsUtils.m                  | 42 ++++++++++++--------
 GTXiLib.podspec                              |  6 +--
 Tests/GTXTests/UnitTests/GTXAnalyticsTests.m |  7 ++++
 4 files changed, 40 insertions(+), 20 deletions(-)

diff --git a/Classes/GTXAnalyticsUtils.h b/Classes/GTXAnalyticsUtils.h
index 864318a..7394d07 100644
--- a/Classes/GTXAnalyticsUtils.h
+++ b/Classes/GTXAnalyticsUtils.h
@@ -43,6 +43,11 @@ NS_ASSUME_NONNULL_BEGIN
  */
 + (NSString *)clientID;
 
+/**
+ @return An appropriate clientID for analytics that is based on hash of given @c bundleID.
+ */
++ (NSString *)clientIDForBundleID:(NSString *)bundleID;
+
 @end
 
 NS_ASSUME_NONNULL_END
diff --git a/Classes/GTXAnalyticsUtils.m b/Classes/GTXAnalyticsUtils.m
index cb16b33..84a0d44 100644
--- a/Classes/GTXAnalyticsUtils.m
+++ b/Classes/GTXAnalyticsUtils.m
@@ -15,6 +15,7 @@
 //
 
 #import "GTXAnalyticsUtils.h"
+#import "GTXAssertions.h"
 #import "GTXLogging.h"
 
 #import <CommonCrypto/CommonDigest.h>
@@ -28,30 +29,37 @@
 
 @implementation GTXAnalyticsUtils
 
-/**
- @return The clientID to be used by GTXiLib analytics, this is a hash of App's bundle ID.
- */
++ (NSString *)clientIDForBundleID:(NSString *)bundleID {
+  // Get SHA256 value of the given string.
+  unsigned char sha256Value[CC_SHA256_DIGEST_LENGTH];
+  const char *stringCPtr = [bundleID UTF8String];
+  CC_SHA256(stringCPtr, (CC_LONG)strlen(stringCPtr), sha256Value);
+
+  // Parse SHA256 value into individual hex values. Note that Google Analytics client ID must be
+  // 128bits long, but SHA256 is 256 bits and there is no standard way to compress hashes, in our
+  // case we use bitwise XOR of the two 128 bit hashes inside the 256 bit hash to produce a 128bit
+  // hash.
+  NSMutableString *stringWithHexValues = [[NSMutableString alloc] init];
+  const NSInteger kClientIDSize = 16;
+  GTX_ASSERT(kClientIDSize * 2 == CC_SHA256_DIGEST_LENGTH,
+             @"CC_SHA256_DIGEST_LENGTH must be 32 it was %d", (int)CC_SHA256_DIGEST_LENGTH);
+  for (int i = 0; i < kClientIDSize; i++) {
+    [stringWithHexValues appendFormat:@"%02x", sha256Value[i] ^ sha256Value[kClientIDSize + i]];
+  }
+  return stringWithHexValues;
+}
+
 + (NSString *)clientID {
   static NSString *clientID;
   static dispatch_once_t onceToken;
   dispatch_once(&onceToken, ^{
-    NSString *bundleIDMD5 = [[NSBundle mainBundle] bundleIdentifier];
-    if (!bundleIDMD5) {
+    NSString *bundleID = [[NSBundle mainBundle] bundleIdentifier];
+    if (!bundleID) {
       // If bundle ID is not available we use a placeholder.
-      bundleIDMD5 = @"<Missing Bundle ID>";
+      bundleID = @"<Missing Bundle ID>";
     }
 
-    // Get MD5 value of the given string.
-    unsigned char md5Value[CC_MD5_DIGEST_LENGTH];
-    const char *stringCPtr = [bundleIDMD5 UTF8String];
-    CC_MD5(stringCPtr, (CC_LONG)strlen(stringCPtr), md5Value);
-
-    // Parse MD5 value into individual hex values.
-    NSMutableString *stringWithHexMd5Values = [[NSMutableString alloc] init];
-    for (int i = 0; i < CC_MD5_DIGEST_LENGTH; i++) {
-      [stringWithHexMd5Values appendFormat:@"%02x", md5Value[i]];
-    }
-    clientID = [stringWithHexMd5Values copy];
+    clientID = [self clientIDForBundleID:bundleID];
   });
 
   return clientID;
diff --git a/GTXiLib.podspec b/GTXiLib.podspec
index f30cb28..1442d7e 100644
--- a/GTXiLib.podspec
+++ b/GTXiLib.podspec
@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name         = "GTXiLib"
-  s.version      = "4.4"
+  s.version      = "4.5"
   s.summary      = "iOS Accessibility testing library."
   s.description  = <<-DESC
   iOS Accessibility testing library that works with XCTest based frameworks.
@@ -9,7 +9,7 @@ Pod::Spec.new do |s|
   s.license      = "Apache License 2.0"
   s.author       = "j-sid"
   s.platform     = :ios
-  s.source       = { :git => "https://github.com/google/GTXiLib.git", :tag => "4.4.0" }
+  s.source       = { :git => "https://github.com/google/GTXiLib.git", :tag => "4.5.0" }
   s.source_files = "{Classes,OOPClasses}/**/*.{h,m,swift,mm,cc}"
   s.public_header_files = "Classes/**/*.h"
   s.private_header_files = [
@@ -22,4 +22,4 @@ Pod::Spec.new do |s|
   s.ios.deployment_target = '9.0'
   s.libraries = 'c++'
   s.dependency 'Protobuf-C++'
-end
\ No newline at end of file
+end
diff --git a/Tests/GTXTests/UnitTests/GTXAnalyticsTests.m b/Tests/GTXTests/UnitTests/GTXAnalyticsTests.m
index ea0e4c7..6971d42 100644
--- a/Tests/GTXTests/UnitTests/GTXAnalyticsTests.m
+++ b/Tests/GTXTests/UnitTests/GTXAnalyticsTests.m
@@ -18,6 +18,7 @@
 #import <XCTest/XCTest.h>
 
 #import "GTXAnalytics.h"
+#import "GTXAnalyticsUtils.h"
 #import "GTXToolKit.h"
 #import "GTXBaseTestCase.h"
 
@@ -43,6 +44,12 @@ - (void)tearDown {
   [super tearDown];
 }
 
+- (void)testClientIDIsAccurate {
+  NSString *expectedClientID = @"90940a64d60ad6c98c3fb6c6307e1d36";
+  XCTAssertEqualObjects(expectedClientID,
+                        [GTXAnalyticsUtils clientIDForBundleID:@"com.google.gtx.test"]);
+}
+
 - (void)testCheckElementReportsAnalyticsCorrectly {
   GTXToolKit *toolkit = [GTXToolKit toolkitWithNoChecks];
   __block NSInteger successEventsCount = 0;