Harden BLP mip bounds and palette regression coverage

[draxxris]

Pull Request

Summary

Some valid BLP2 files contain zero-sized trailing mipmap slots. The parser should stop at those slots instead of reporting false out-of-bounds errors.

Checked offset arithmetic also prevents malformed headers from causing integer overflow or invalid buffer slicing.

The RAW1 test protects the existing palette channel-order behavior.

From: https://forum.warmane.com/showthread.php?t=464195

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing
  functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test improvements
• Build system/dependency changes
• Security fix

Changes Made

• Add checked arithmetic for BLP mipmap offsets and sizes.
• Reject mip payloads that exceed the source buffer.
• Treat zero-sized trailing mipmap slots as valid terminators.
• Add a RAW1 palette regression test for BGRX-to-RGBA conversion.
• Valid BLP mipmaps retain their existing behavior.
• Malformed offsets return parsing errors.
• Zero-sized trailing mipmaps are accepted as terminators.
• No production RAW1 decoding behavior changes.

Testing

Test Cases Added/Modified

• Unit tests
• Integration tests
• Compliance tests (StormLib compatibility)
• Performance benchmarks
• Manual testing

Test Results

$ cargo test -p wow-blp
   Compiling wow-blp v0.7.0 (/home/gordon/workspace/felix/vendor/warcraft-rs/file-formats/graphics/wow-blp)
    Finished `test` profile [unoptimized + debuginfo] target(s) in 3.85s
     Running unittests src/lib.rs (target/debug/deps/wow_blp-c7457cb23b442109)

running 18 tests
test convert::jpeg::tests::test_fetch_common_header ... ok
test convert::raw1::tests::bgrx_palette_decodes_to_rgba ... ok
test path::tests::test_blp0_path ... ok
test parser::bounds::tests::test_size_out_of_bounds ... ok
test parser::direct::blp2::tests::zero_sized_trailing_mipmaps_are_ignored ... ok
test encode::tests::test_sorting ... ok
test types::header::tests::test_alpha_type_conversion ... ok
test types::header::tests::test_alpha_type_wow_version_support ... ok
test encode::primitives::tests::test_push_le_u32 ... ok
test parser::bounds::tests::test_get_bounded_slice ... ok
test parser::bounds::tests::test_offset_out_of_bounds ... ok
test convert::dxtn::tests::test_dxt1_valid_buffer_succeeds ... ok
test convert::dxtn::tests::test_empty_buffer_produces_blank_image ... ok
test convert::dxtn::tests::test_dxt5_undersized_buffer_succeeds_with_padding ... ok
test convert::dxtn::tests::test_dxt3_undersized_buffer_succeeds_with_padding ... ok
test types::header::tests::test_mipmap_count ... ok
test parser::bounds::tests::test_valid_bounds ... ok
test types::version::tests::known_magics ... ok

test result: ok. 18 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

   Doc-tests wow_blp

running 6 tests
test file-formats/graphics/wow-blp/src/lib.rs - (line 109) - compile ... ok
test file-formats/graphics/wow-blp/src/lib.rs - (line 125) - compile ... ok
test file-formats/graphics/wow-blp/src/lib.rs - (line 176) - compile ... ok
test file-formats/graphics/wow-blp/src/lib.rs - (line 25) - compile ... ok
test file-formats/graphics/wow-blp/src/lib.rs - (line 35) - compile ... ok
test file-formats/graphics/wow-blp/src/lib.rs - (line 153) ... ok

test result: ok. 6 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

all doctests ran in 1.31s; merged doctests compilation took 1.29s
...

Tested On

• Linux
• macOS
• Windows
• Cross-compilation targets

WoW Versions Tested

• 1.12.1 (Vanilla)
• 2.4.3 (TBC)
• 3.3.5a (WotLK)
• 4.3.4 (Cataclysm)
• 5.4.8 (MoP)
• Other: Custom game engine