loader/obj: guard against out-of-range face indices to prevent panic - #322
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ChrisJr404 wants to merge 1 commit into
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loader/obj: guard against out-of-range face indices to prevent panic#322ChrisJr404 wants to merge 1 commit into
ChrisJr404 wants to merge 1 commit into
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A face line whose vertex/uv/normal index points past the decoded arrays (e.g. "f 1 2 999999", or a large negative index) caused NewGeometry to panic with an index-out-of-range while copying vertices, since the indices read straight from the OBJ were passed to ArrayF32.GetVector3/GetVector2 without any bounds check. A malformed or malicious .obj is enough to crash a program that loads it. Validate each index against the corresponding array length before use and return an error instead of panicking. The bounds are checked with the element count (len/stride) rather than stride*index so the check itself cannot overflow. Adds tests covering the out-of-range cases and a valid file.
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Problem
Loading an OBJ file whose face lines reference vertex/UV/normal indices outside the range of the data actually present in the file causes a panic (
index out of range) rather than an error.In
NewGeometry, the indices parsed fromflines are handed straight tomath32.ArrayF32.GetVector3/GetVector2, which do unchecked slice access:Nothing verifies that the index is within the decoded
Vertices/Normals/Uvsarrays. A file such as:panics on the standard load path (
obj.Decode/DecodeReaderfollowed byNewGroup/NewGeometry). Large negative indices (e.g.f -100 -100 -100) hit the same problem via the relative-index math. Since OBJ files are frequently loaded from untrusted or user-supplied sources, a single malformed file can crash the host program.Fix
Bounds-check each vertex/UV/normal index against the corresponding array before dereferencing it, and return an error from
NewGeometryinstead of panicking. The check uses the element count (len/stride) rather thanstride*index, so it can't overflow on 32-bit platforms. Valid files are completely unaffected.Tests
Added
loader/obj/obj_test.gocovering out-of-range vertex/UV/normal indices (including a large negative index) and a well-formed file that must still build geometry without error. The out-of-range tests panic without this change and pass with it.go test ./loader/obj/,go vet, andgofmtare clean.