Crash in [APMMeasurement fetchRemoteConfig]

[eparis-bit]

Description

App crash at first startup after fresh install, after a few seconds. The stack trace indicate a crash when APMMeasurement calls [NSString(Bit) isBitEnabledAtIndex:]:

Fatal Exception: NSInvalidArgumentException
-[__NSCFConstantString characterAtIndex:]: Range or index out of bounds

0 CoreFoundation 0xec678 (Missing UUID 5a6c1f41bf7032f6a1d65b894dd21362)
1 libobjc.A.dylib 0x2bc80 objc_exception_throw
2 CoreFoundation 0x1b4cbc (Missing UUID 5a6c1f41bf7032f6a1d65b894dd21362)
3 CoreFoundation 0x1b4cf4 (Missing UUID 5a6c1f41bf7032f6a1d65b894dd21362)
4 CoreFoundation 0x381b4 (Missing UUID 5a6c1f41bf7032f6a1d65b894dd21362)
5 Bandsintown Concerts 0x18fdb90 -[NSString(Bit) isBitEnabledAtIndex:]
6 Bandsintown Concerts 0x18f9c94 -[APMTCFClient stringRepresentationFromTCFData]
7 Bandsintown Concerts 0x18f9ea0 -[APMTCFClient persistedValuesEqualCurrentData]
8 Bandsintown Concerts 0x18f974c -[APMTCFClient setConsentFromTCFData]
9 Bandsintown Concerts 0x18a1f68 -[APMMeasurement tcfClientSetConsentFromData]
10 Bandsintown Concerts 0x1899dd0 -[APMMeasurement uploadData]
11 Bandsintown Concerts 0x18a0d30 -[APMMeasurement networkRemoteConfigFetchCompletionHandler:data:error:]
12 Bandsintown Concerts 0x18a0668 __35-[APMMeasurement fetchRemoteConfig]_block_invoke
13 libdispatch.dylib 0x26a8 (Missing UUID c49a5fc2c87339139603004f5d0175e7)
14 libdispatch.dylib 0x4300 (Missing UUID c49a5fc2c87339139603004f5d0175e7)
...

Reproducing the issue

No response

Firebase SDK Version

10.23.0

Xcode Version

15.2

Installation Method

Swift Package Manager

Firebase Product(s)

Analytics

Targeted Platforms

iOS

Relevant Log Output

No response

If using Swift Package Manager, the project's Package.resolved

Expand Package.resolved snippet

    {
      "identity" : "firebase-ios-sdk",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/firebase/firebase-ios-sdk",
      "state" : {
        "revision" : "fcf5ced6dae2d43fced2581e673cc3b59bdb8ffa",
        "version" : "10.23.0"
      }
    }

If using CocoaPods, the project's Podfile.lock

Expand Podfile.lock snippet

Replace this line with the contents of your Podfile.lock!

[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.

[CWftw]

Seeing this as well after updating Firebase pods to 10.23.0

[rizafran]

Thanks for reporting. I tried to reproduce the issue but I'm unable to get the same error. Is it possible for you to provide a reproducible example?

[eparis-bit]

I tried a different things that could help fix the issue.

First I tried downgrading to Firebase 10.22.1 / GoogleAppMeasurement 10.22.1 => no crash

Then I updated back to Firebase 10.23.0 / GoogleAppMeasurement 10.23.0 => crash on first app launch

Second, I swizzled the method [NSString isBitEnabledAtIndex:] to intercept the calls to this method and to inspect the arguments: that method is call with self = empty string @"" and index = 754. It raised an exception and crash the app.
Curiously at the second run, it also raised an exception but it's catched and that line is output in the console:

10.23.0 - [FirebaseAnalytics][I-ACS030000] Exception on worker queue. Block ID=APMMeasurement:1771. Exception: 0x00000001039e7590 -[APMTCFClient: -[__NSCFConstantString characterAtIndex:]: Range or index out of bounds

It looks like that method is called when parsing the protobuf response of that http request:

https://app-analytics-services.com/config/app/1:826312950607:ios:18cdd083d09049a7?platform=ios&runtime_version=0&gmp_version=102300

Maybe I have some usual configs in my app on Firebase.

My workaround to prevent the crash:

// Woraround bug in GoogleAppMeasurement framework 10.23.0
// see: https://github.com/firebase/firebase-ios-sdk/issues/12614

@interface NSString (Bit)

- (BOOL)isBitEnabledAtIndex:(NSInteger)index;

@end

@implementation NSString (Swizzled)

- (BOOL)swizzleIsBitEnabledAtIndex:(NSInteger)index
{
    if ([self length] < index) {
        return NO;
    }
    return [self swizzleIsBitEnabledAtIndex:index];
}

@end

...
    MethodSwizzle([NSString class], @selector(isBitEnabledAtIndex:), @selector(swizzleIsBitEnabledAtIndex:));
...

[pcfba]

Thanks for the report. We have a fix for this crash that will go out in the next release.

[pcfba]

Internal tracking bug b/331256683.