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Defensive access to MIMEType #15318

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Defensive access to MIMEType #15318

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Defensive access to MIMEType
JesusRojass Sep 11, 2025
898e575
Update FirebasePerformance/Sources/Instrumentation/FPRNetworkTrace.m
JesusRojass Sep 11, 2025
4594fa2
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JesusRojass Sep 11, 2025
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13 changes: 11 additions & 2 deletions FirebasePerformance/Sources/Instrumentation/FPRNetworkTrace.m
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Original file line number Diff line number Diff line change
Expand Up @@ -251,8 +251,17 @@ - (void)didCompleteRequestWithResponse:(NSURLResponse *)response error:(NSError
self.responseCode = (int32_t)HTTPResponse.statusCode;
}
self.responseError = error;
// Safely copy MIMEType to prevent use after free
NSString *mime = [response.MIMEType copy];
// Defensive access to MIMEType
NSString *mime = nil;
@try {
// Safely copy MIMEType to prevent use after free
mime = [response.MIMEType copy];
} @catch (NSException *exception) {
FPRLogWarning(@"MIMETypeException",
@"Exception while accessing MIMEType for URL %@: %@. Trace will continue "
@"without MIMEType.",
self.URLRequest.URL, exception);
}
Comment on lines +254 to +264
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I don't believe a crash like this can be handled. Only NSExceptions can be handled and there isn't one being raised here. This crash is coming at a lower level.

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Would wrapping the 2 lines I already contributed in a if (response) for example would be a better solution? (of course keeping tabs if the crash ever shows up again)

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No, because in order for the getMIMEType method to appear in the stack trace, the response is non-nil. Because if the response was nil, the MIMEType call would be a no-op.

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Ok got it, I'm a bit out of ideas maybe I can do a bit more research and try a better solution for this

Thanks Nick

self.responseContentType = (mime.length ? mime : nil);
[self checkpointState:FPRNetworkTraceCheckpointStateResponseCompleted];

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