Aws-sdk-ios: Crash in AWSAuthCore *** -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[0]

[soxjke]

Describe the bug
App crashes within AWSAuthCore intermittently, presumably at AWSIdentityManager.m:80 while trying to create a dictionary.

An exception message is:

Fatal Exception: NSInvalidArgumentException
*** -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[0]

To Reproduce
Crash is intermittent, I grab it from users' crash logs, an example stack trace:

Fatal Exception: NSInvalidArgumentException
0  CoreFoundation                 0x23ba68ec4 __exceptionPreprocess
1  libobjc.A.dylib                0x23ac39a50 objc_exception_throw
2  CoreFoundation                 0x23b9e0494 _CFArgv
3  CoreFoundation                 0x23b966980 -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]
4  CoreFoundation                 0x23b9574c4 +[NSDictionary dictionaryWithObjects:forKeys:count:]
5  AWSAuthCore                    0x1049a3b40 (Missing)
6  AWSCore                        0x104eb36e8 (Missing)
7  AWSCore                        0x104eb3058 (Missing)
8  AWSCore                        0x104e804ac (Missing)
9  AWSCore                        0x104e80a18 (Missing)
10 AWSCore                        0x104eb2c50 (Missing)
11 AWSCore                        0x104eb2788 (Missing)
12 AWSCore                        0x104eb3dd4 (Missing)
13 AWSCore                        0x104eb312c (Missing)
14 Foundation                     0x23c4f88bc __NSBLOCKOPERATION_IS_CALLING_OUT_TO_A_BLOCK__
15 Foundation                     0x23c400ab8 -[NSBlockOperation main]
16 Foundation                     0x23c3fff8c -[__NSOperationInternal _start:]
17 Foundation                     0x23c4fa790 __NSOQSchedule_f
18 libdispatch.dylib              0x23b4a16c8 _dispatch_call_block_and_release
19 libdispatch.dylib              0x23b4a2484 _dispatch_client_callout
20 libdispatch.dylib              0x23b44582c _dispatch_continuation_pop$VARIANT$mp
21 libdispatch.dylib              0x23b444ef4 _dispatch_async_redirect_invoke
22 libdispatch.dylib              0x23b451a18 _dispatch_root_queue_drain
23 libdispatch.dylib              0x23b4522c0 _dispatch_worker_thread2
24 libsystem_pthread.dylib        0x23b68517c _pthread_wqthread
25 libsystem_pthread.dylib        0x23b687cec start_wqthread

Which AWS service(s) are affected?
AWSAuthCore

Expected behavior
No crash

Screenshots
No screenhots

Environment(please complete the following information):

• SDK Version: 2.8.2
• Dependency Manager: Cocoapods
• Swift Version : 4.0

Device Information (please complete the following information):

• Device: various, iPhone 7, iPhone XS Max, iPhone XS etc.
• iOS Version: mostly iOS 12.1.2

Additional context

It always happens on a background thread. There's also always the same operation on a main thread at the time of the crash:

com.apple.main-thread
0  libsystem_kernel.dylib         0x20df93ea4 mach_msg_trap + 8
1  libsystem_kernel.dylib         0x20df9337c mach_msg + 72
2  libdispatch.dylib              0x20ddf82d0 _dispatch_mach_send_and_wait_for_reply + 500
3  libdispatch.dylib              0x20ddf8764 dispatch_mach_send_with_result_and_wait_for_reply$VARIANT$mp + 56
4  libxpc.dylib                   0x20e05beb4 xpc_connection_send_message_with_reply_sync + 204
5  Security                       0x20f0adaac securityd_message_with_reply_sync + 96
6  Security                       0x20f0ae070 securityd_send_sync_and_do + 80
7  Security                       0x20f107a84 __SecItemCopyMatching_block_invoke_2 + 240
8  Security                       0x20f1068c4 __SecItemAuthDoQuery_block_invoke + 312
9  Security                       0x20f105314 SecItemAuthDo + 108
10 Security                       0x20f105bac SecItemAuthDoQuery + 512
11 Security                       0x20f10796c __SecItemCopyMatching_block_invoke + 120
12 Security                       0x20f103920 SecOSStatusWith + 52
13 Security                       0x20f105fa0 SecItemCopyMatching + 332
14 AWSCore                        0x1033e7604 -[AWSUICKeyChainStore dataForKey:error:] + 208
15 AWSCore                        0x1033e6ed8 -[AWSUICKeyChainStore stringForKey:error:] + 40
16 AWSCore                        0x10338f18c -[AWSCognitoCredentialsProvider internalCredentials] + 116
17 AWSCore                        0x10338ddb4 -[AWSCognitoCredentialsProvider credentials] + 52
18 AWSAuthCore                    0x102ea0734 -[AWSSignInManager completeLogin] + 244
19 AWSGoogleSignIn                0x103039450 -[AWSGoogleSignInProvider completeLoginWithToken] + 56
20 AWSGoogleSignIn                0x103039734 -[AWSGoogleSignInProvider signIn:didSignInForUser:withError:] + 576
21 MyApp                          0x102d3fb7c __31-[GIDSignIn signInWithOptions:]_block_invoke + 4332698492
22 MyApp                          0x102d36548 -[GIDAuthentication getTokensWithHandler:] + 4332660040
23 MyApp                          0x102d3faa8 -[GIDSignIn signInWithOptions:] + 4332698280
24 MyApp                          0x102d3c0a8 -[GIDSignIn signInSilently] + 4332683432
25 AWSGoogleSignIn                0x103039338 __32-[AWSGoogleSignInProvider token]_block_invoke_2 + 52
26 libdispatch.dylib              0x20de416c8 _dispatch_call_block_and_release + 24
27 libdispatch.dylib              0x20de42484 _dispatch_client_callout + 16
28 libdispatch.dylib              0x20ddee9a4 _dispatch_main_queue_callback_4CF$VARIANT$mp + 1068
29 CoreFoundation                 0x20e398df4 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 12
30 CoreFoundation                 0x20e393cbc __CFRunLoopRun + 1964
31 CoreFoundation                 0x20e3931f0 CFRunLoopRunSpecific + 436
32 GraphicsServices               0x21060c584 GSEventRunModal + 100
33 UIKitCore                      0x23b6ead40 UIApplicationMain + 212
34 MyApp                          0x102c4dc8c main (AppDelegate.swift:25)
35 libdyld.dylib                  0x20de52bb4 start + 4

I derive that this is some multithreading issue, when task.result is nil in continueWithSuccessBlock: within [AWSIdentityManager logins] at line 79 and further it crashes while creating dictionary at line 80.

P.S. I studied other issues before opening this, https://github.com/aws-amplify/aws-sdk-ios/issues/1060 is similar, but not related. Please don't refer to it as a possible duplicate.

[rohandubal]

Hello @soxjke

Thanks for reporting this. I agree with your analysis that it is likely due to task.result which has the auth token is nil.

Could you please describe what API/ functionality in auth core you are using? This will help me start tracking the code path for this crash. A simple fix would be a null check, but I want to be sure to identify a root cause and fix it.

Thanks,
Rohan

[soxjke]

Hi @rohandubal

The list functionality used by the app:

• AWSIdentityManager.default().logins()
• AWSIdentityManager.default().identityId
• AWSSignInManager.sharedInstance().resumeSession
• AWSSignInManager.sharedInstance().logout
• AWSSignInManager.sharedInstance().interceptApplication
-

        AWSFacebookSignInProvider.sharedInstance().setPermissions(["public_profile"])
        AWSSignInManager.sharedInstance().register(signInProvider: AWSFacebookSignInProvider.sharedInstance())
        AWSGoogleSignInProvider.sharedInstance().setScopes(["profile", "openid"])
        AWSSignInManager.sharedInstance().register(signInProvider: AWSGoogleSignInProvider.sharedInstance())

        AWSSignInManager.sharedInstance().register(signInProvider: AWSCognitoUserPoolsSignInProvider.sharedInstance())

However, I'd try to focus on following tips:

1. There's always -[GIDSignIn signInSilently] call at AWSGoogleSignInProvider.m:156 on the main thread, while the background thread is crashed on a mentioned stacktrace.
2. I suspect that setting result at AWSGoogleSignInProvider.m:156 triggers the success block in AWSIdentityManager, so the crash comes from GoogleSignIn, where token is returned nil from Google lib in -signIn:didSignInForUser:withError:while error is also nil

[soulchain]

I am facing the same problem now. Any suggestion to fix this?

[pablogeek]

Same problem here. Have anyone been able to fix this?

[soxjke]

The main idea of fix is basically to to add check for nil at AWSIdentityManager.m:78

You can fork and do a fix or use runtime to apply workaround. My choice for now is runtime - here's gist

https://gist.github.com/soxjke/4c79e923ec549e8d7e4e0ef219f12bd5

@soulchain @pablogeek