fix: detect real Flutter snapshot hash in elff() - #387
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The old elff() opened the binary in text mode with errors='ignore', which dropped non-UTF8 bytes and concatenated printable segments that were separated by binary bytes. This produced fake 32-hex strings that are not real snapshot hashes, causing 'This engine is currently not supported' even when the real hash exists in enginehash.csv. Read the file as binary and collect contiguous 32-hex ASCII runs, preferring candidates that appear in enginehash.csv.
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August 28, 2026 08:06
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Why
elff()currently opens the target binary in text mode (errors="ignore"), which silently drops non-UTF8 bytes and then concatenates printable segments that were originally separated by binary bytes. When those concatenated segments happen to form a 32-character hex string, it is returned as the engine snapshot hash — even though it is not a real hash.This makes reFlutter report
This engine is currently not supported.for apps whose real snapshot hash is present inenginehash.csv. Any app whose binary layout triggers this false-positive string is wrongly rejected.What Changed
elff()now reads the file as binary and collects only contiguous 32-hex ASCII runs.enginehash.csv(cached module-wide) so the real snapshot hash wins even when other 32-hex runs appear earlier in the file.Verification
Reproduced on an iOS app (Flutter 3.24.0 engine):
elff)release.RE.ipaproducedThe fix was independently confirmed by scanning both
App.framework/AppandFlutter.framework/Flutterfor contiguous 32-hex runs, and matching the result againstenginehash.csv.