fix: bounds check prefixes index in convert_to_unicode#289
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After setting index from enc->bytemap[], validate that it is less than enc->prefixes_size before using it to access enc->prefixes[] on the next loop iteration. A corrupt or malicious .enc file could contain a bytemap entry pointing beyond the prefixes array, causing an out-of-bounds read. The fix mirrors the validation pattern already used during loading in XML_LoadEncoding and safely breaks out of the conversion loop when an invalid index is encountered (returning -1 for unmappable character). Adds test exercising the code path with a crafted encoding file whose bytemap contains an index beyond prefixes_size. Fixes #284 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #289 +/- ##
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+ Coverage 76.40% 76.68% +0.27%
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Files 1 1
Lines 1102 1115 +13
Branches 346 352 +6
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+ Hits 842 855 +13
+ Misses 52 51 -1
- Partials 208 209 +1
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Summary
Adds a missing bounds check in
convert_to_unicode()where theindexvariable (set fromenc->bytemap[]) is used to accessenc->prefixes[index]without validating thatindex < enc->prefixes_size. A corrupt or malicious.encfile could trigger an out-of-bounds read.Fixes #284
Changes
if (index >= enc->prefixes_size) break;after bytemap lookup inconvert_to_unicode()(Expat/Expat.xs:1145)Test plan
make testpasses (728 tests, all successful)prefixes_sizeconvert_to_unicodesafely returns -1Generated by Kōan /fix
Quality Report
Changes: 2 files changed, 84 insertions(+), 1 deletion(-)
Code scan: clean
Tests: passed (OK)
Branch hygiene: clean
Generated by Kōan post-mission quality pipeline