Crash when bringing app to foreground after regaining internet connection

[eric-melo]

MSAL Version

2.3.0

Description

When I have the app in background without internet connection, receive some notification, gain back internet connection and foreground the app, it hits a deadlock within MSAL and crashes.

Error Details

Exception Type: EXC_CRASH (SIGKILL)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Termination Reason: FRONTBOARD 2343432205
<RBSTerminateContext| domain:10 code:0x8BADF00D explanation:scene-update watchdog transgression: app<com.symphony.intune(AD242FCD-75FD-444D-8AFD-EBD668CDDC2D)>:896 exhausted real (wall clock) time allowance of 30.00 seconds
ProcessVisibility: Foreground
ProcessState: Running
WatchdogEvent: scene-update
WatchdogVisibility: Background
WatchdogCPUStatistics: (
"Elapsed total CPU time (seconds): 50.710 (user 29.310, system 21.400), 28% CPU",
"Elapsed application CPU time (seconds): 30.186, 17% CPU"
)
ThermalInfo: (
"Thermal Level: 0",
"Thermal State: nominal"
) reportType:CrashLog maxTerminationResistance:Interactive>

Triggered by Thread: 0

Thread 0 name: Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0 libsystem_kernel.dylib 0x1e27f1f18 __psynch_mutexwait + 8
1 libsystem_pthread.dylib 0x21bcdeb68 _pthread_mutex_firstfit_lock_wait + 84
2 libsystem_pthread.dylib 0x21bcdec98 _pthread_mutex_firstfit_lock_slow + 220
3 CFNetwork 0x192b8aae0 __CFURLCacheCopyResponseForRequestWithCompletionHandler + 300
4 CFNetwork 0x192c2f860 CFURLCacheCopyResponseForRequest + 168
5 CFNetwork 0x192c4b950 -[NSURLCache cachedResponseForRequest:] + 40
6 SymphonyIntune 0x104984f7c -[MSIDHttpRequest cachedResponse] + 68
7 SymphonyIntune 0x10498438c -[MSIDHttpRequest sendWithBlock:] + 468
8 SymphonyIntune 0x10494fe2c -[MSIDAuthority loadOpenIdMetadataWithContext:completionBlock:] + 492
9 SymphonyIntune 0x104987d20 __69-[MSIDInteractiveAuthorizationCodeRequest getAuthCodeWithCompletion:]_block_invoke + 200
10 SymphonyIntune 0x10494f914 __78-[MSIDAuthority resolveAndValidate:userPrincipalName:context:completionBlock:]_block_invoke + 420
11 SymphonyIntune 0x104931d74 -[MSIDAadAuthorityResolver handleRecord:authority:completionBlock:] + 248
12 SymphonyIntune 0x1049313e0 -[MSIDAadAuthorityResolver resolveAuthority:userPrincipalName:validate:context:completionBlock:] + 184
13 SymphonyIntune 0x10494f720 -[MSIDAuthority resolveAndValidate:userPrincipalName:context:completionBlock:] + 516
14 SymphonyIntune 0x104987c04 -[MSIDInteractiveAuthorizationCodeRequest getAuthCodeWithCompletion:] + 352
15 SymphonyIntune 0x104989530 -[MSIDInteractiveTokenRequest executeRequestWithCompletion:] + 180
16 SymphonyIntune 0x1049a28c0 -[MSIDLocalInteractiveController acquireTokenWithRequest:completionBlock:] + 252
17 SymphonyIntune 0x1049a19c8 -[MSIDLocalInteractiveController acquireToken:] + 372
18 SymphonyIntune 0x104956efc -[MSIDBrokerInteractiveController handleFailedOpenURL:] + 420
19 IntuneMAMSwift 0x1090668c4 0x108ec8000 + 1697988
20 libdispatch.dylib 0x199558aac _dispatch_call_block_and_release + 32
21 libdispatch.dylib 0x199572584 _dispatch_client_callout + 16
22 libdispatch.dylib 0x19958f5a0 _dispatch_main_queue_drain.cold.5 + 812
23 libdispatch.dylib 0x199567d30 _dispatch_main_queue_drain + 180
24 libdispatch.dylib 0x199567c6c _dispatch_main_queue_callback_4CF + 44
25 CoreFoundation 0x191639d90 CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE + 16
26 CoreFoundation 0x1915dd4f4 __CFRunLoopRun + 1980
27 CoreFoundation 0x1915dec3c CFRunLoopRunSpecific + 572
28 GraphicsServices 0x1de7bd454 GSEventRunModal + 168
29 UIKitCore 0x193ff1274 -[UIApplication _run] + 816
30 UIKitCore 0x193fbca28 UIApplicationMain + 336
31 IntuneMAMSwift 0x10919af10 0x108ec8000 + 2961168
32 SymphonyIntune 0x1047e0004 main + 64
33 dyld 0x1b84b3f08 start + 6040

MSAL Logs

I'm not able to capture MSAL logs as described in the documentation because I also embed IntuneMAMSwift and MicrosoftTunnelApi frameworks. It seems like IntuneMAMSwift already sets the logger callback so I can do it myself.

Reproduction Steps

1. Correctly enroll to Intune and sign in to the app
2. Remove internet connection from the phone
3. Send app to background
4. Receive a few messages in the app
5. Restore internet connection and wait for the notifications for the messages above to appear
6. Bring app back to foreground
   At this point the app gets stuck and crashes

Expected Behavior

It must not get stuck on a deadlock and not crash

Regression

No response

Screenshots & Screen Recordings

No response

Additional context

No response

[eric-melo]

Hi, any news on this?

[antonioalwan]

Hi Eric Melo (@eric-melo), It seems that network calls are being executed on the main thread. To improve performance and responsiveness and avoid deadlocks, ensure all calls to NSURLCache and related APIs are done on background threads. Additionally, ensure your app handles lifecycle events by listening for UIApplicationDidEnterBackground and UIApplicationWillEnterForeground notifications.

[eric-melo]

Hi Antonio Alwan (@antonioalwan), I've made a build putting everything I can in a background thread and the crash still happens with identical stacktrace.
The point in the stacktrace that's interesting is that you have the call [MSIDLocalInteractiveController acquireToken:] coming from a _dispatch_call_block_and_release. What this tells me is that inside the Intune or MSAL SDKs, you have a callback putting the execution back in the main thread to acquire a token in an interactive way, but that leads to a network request that is called in the same thread causing the crash.

Could you please have another look on this topic?

[eric-melo]

Hi Antonio Alwan (@antonioalwan), have you had the chance to check my previous message?

[eric-melo]

Hi Antonio Alwan (@antonioalwan), could you please check my comment above? Is there anything else that can be done? Thanks

[eric-melo]

Hi Antonio Alwan (@antonioalwan), could you please check my comment above? Is there anything else that can be done? Thanks

[antonioalwan]

Hi Eric Melo (@eric-melo), let me take a look sorry I missed your updates

[antonioalwan]

Hi Eric Melo (@eric-melo), could you please try implementing the following fix and confirm if it resolves the issue?

- (void)appWillEnterForeground:(NSNotification *)notification {
    // Cancel any pending MSAL requests before app enters foreground
    [msal cancelCurrentWebAuthSession];
}

In the meantime, I will add this issue to our backlog for further tracking.