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Decode Hex and Base64 from a copy when the source overlaps the destination [patch] - #167
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…ation [patch] TryEncode copies an overlapping source to a pooled buffer first (#138), but TryDecode did not. With the destination starting after the source in the same buffer, Hex overwrote encoded pairs before reading them and Base64.DecodeFromUtf8, which does not support overlap, corrupted or rejected valid input. Both returned true with corrupted output in most cases, and the Hex and Base64 obfuscators' TryDeobfuscate forward to these decoders. TryDecode now does what TryEncode does: when the spans overlap, it decodes from a pooled copy and clears the copy before returning it. Decode-direction overlap tests sit next to the encode ones and cover every IEncodingProvider and IObfuscationProvider at offsets (0,0), (0,3) and (3,0). Fixes #166 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_017vfJW6XNeWiDxG4BVzYTra
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Fixes #166
Problem
#138 made
TryEncode/TryObfuscatesafe for overlapping buffers, butTryDecodewas not. The problem appears when the destination starts after the source in the same buffer:Base64.DecodeFromUtf8directly, which does not support overlapping buffers.In most cases both returned
truewith corrupted output. The Hex and Base64 obfuscators'TryDeobfuscateforward to these decoders, so they were affected too.Change
HexEncodingProvider.TryDecodeandBase64EncodingProvider.TryDecodenow do whatTryEncodealready does. WhenencodedData.Overlaps(destination), they decode from anArrayPoolcopy and clear the copy before returning it to the pool. Each class's remarks now say that both directions copy on overlap.Tests
EncodingProviderTests.Decoding_OverlappingBuffers_MatchesOutOfPlacecovers everyIEncodingProvider, next to the existing encode overlap test.ObfuscationProviderTests.Deobfuscation_OverlappingBuffers_MatchesOutOfPlacecovers everyIObfuscationProvider, next to the existing obfuscate overlap test.Generated by Claude Code