Revert removal of synchronized

Author: echo-branch

Sources/BranchSDK/BNCKeyChain.m

@@ -149,35 +149,37 @@ + (NSError*) removeValuesForService:(NSString *)service key:(NSString *)key {
 
 // The security access group string is prefixed with the Apple Developer Team ID
 + (NSString * _Nullable)securityAccessGroup {
-    static NSString *_securityAccessGroup = nil;
-    if (_securityAccessGroup) return _securityAccessGroup;
-    
-    // The keychain cannot be empty prior to requesting the security access group string. Add a tmp variable.
-    NSError *error = [self storeDate:[NSDate date] forService:@"BranchKeychainService" key:@"Temp" cloudAccessGroup:nil];
-    if (error) {
-        [[BranchLogger shared] logWarning:@"Failed to store temp value" error:error];
-    }
-    
-    NSDictionary* dictionary = @{
-        (__bridge id)kSecClass:                 (__bridge id)kSecClassGenericPassword,
-        (__bridge id)kSecAttrService:           @"BranchKeychainService",
-        (__bridge id)kSecReturnAttributes:      (__bridge id)kCFBooleanTrue,
-        (__bridge id)kSecAttrSynchronizable:    (__bridge id)kSecAttrSynchronizableAny,
-        (__bridge id)kSecMatchLimit:            (__bridge id)kSecMatchLimitOne
-    };
-    CFDictionaryRef resultDictionary = NULL;
-    OSStatus status = SecItemCopyMatching((__bridge CFDictionaryRef)dictionary, (CFTypeRef*)&resultDictionary);
-    if (status == errSecItemNotFound) return nil;
-    if (status != errSecSuccess) {
-        [[BranchLogger shared] logWarning:[NSString stringWithFormat:@"Failed to retrieve security access group"] error:[self errorWithKey:nil OSStatus:status]];
-        return nil;
-    }
-    NSString *group = [(__bridge NSDictionary *)resultDictionary objectForKey:(__bridge NSString *)kSecAttrAccessGroup];
-    if (group.length > 0) {
-        _securityAccessGroup = [group copy];
+    @synchronized(self) {
+        static NSString *_securityAccessGroup = nil;
+        if (_securityAccessGroup) return _securityAccessGroup;
+        
+        // The keychain cannot be empty prior to requesting the security access group string. Add a tmp variable.
+        NSError *error = [self storeDate:[NSDate date] forService:@"BranchKeychainService" key:@"Temp" cloudAccessGroup:nil];
+        if (error) {
+            [[BranchLogger shared] logWarning:@"Failed to store temp value" error:error];
+        }
+        
+        NSDictionary* dictionary = @{
+            (__bridge id)kSecClass:                 (__bridge id)kSecClassGenericPassword,
+            (__bridge id)kSecAttrService:           @"BranchKeychainService",
+            (__bridge id)kSecReturnAttributes:      (__bridge id)kCFBooleanTrue,
+            (__bridge id)kSecAttrSynchronizable:    (__bridge id)kSecAttrSynchronizableAny,
+            (__bridge id)kSecMatchLimit:            (__bridge id)kSecMatchLimitOne
+        };
+        CFDictionaryRef resultDictionary = NULL;
+        OSStatus status = SecItemCopyMatching((__bridge CFDictionaryRef)dictionary, (CFTypeRef*)&resultDictionary);
+        if (status == errSecItemNotFound) return nil;
+        if (status != errSecSuccess) {
+            [[BranchLogger shared] logWarning:[NSString stringWithFormat:@"Failed to retrieve security access group"] error:[self errorWithKey:nil OSStatus:status]];
+            return nil;
+        }
+        NSString *group = [(__bridge NSDictionary *)resultDictionary objectForKey:(__bridge NSString *)kSecAttrAccessGroup];
+        if (group.length > 0) {
+            _securityAccessGroup = [group copy];
+        }
+        CFRelease(resultDictionary);
+        return _securityAccessGroup;
     }
-    CFRelease(resultDictionary);
-    return _securityAccessGroup;
 }
 
 @end