Close remaining path-validation gaps in install flow#409
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Three gaps in install-time path handling that survived e20a3ed: - mod.id, mod.version, mod.parent, and pkg.folder were concatenated into modPath without validation, BEFORE the existing IsSubPath check. A poisoned id like "..\..\Windows\System32" let every subsequent file.dest pass against the poisoned base. New KnUtils.IsSafePathComponent (rejects separators, "..", null bytes, drive letters, NTFS-stripped trailing dots/spaces); InstallMod and InstallBuild now validate before building modPath. - TryToCopyFilesFromOldVersions called File.Exists, GetFileHash, File.Copy, and HardLink.CreateFileLink on paths built from JSON- supplied oldPkg.folder / package.folder / f.filename with no IsSubPath check. Now guarded on both the read and write sides, with the existing clear-lists-and-break failure pattern. - IsSubPath used OrdinalIgnoreCase unconditionally; on Linux/macOS that let same-name-different-case siblings pass as in-base. Now Ordinal on non-Windows. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
wookieejedi
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May 11, 2026
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Things still seem to work as expected
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Three gaps in install-time path handling that survived e20a3ed:
mod.id, mod.version, mod.parent, and pkg.folder were concatenated into modPath without validation, BEFORE the existing IsSubPath check. A poisoned id like "....\Windows\System32" let every subsequent file.dest pass against the poisoned base. New KnUtils.IsSafePathComponent (rejects separators, "..", null bytes, drive letters, NTFS-stripped trailing dots/spaces); InstallMod and InstallBuild now validate before building modPath.
TryToCopyFilesFromOldVersions called File.Exists, GetFileHash, File.Copy, and HardLink.CreateFileLink on paths built from JSON- supplied oldPkg.folder / package.folder / f.filename with no IsSubPath check. Now guarded on both the read and write sides, with the existing clear-lists-and-break failure pattern.
IsSubPath used OrdinalIgnoreCase unconditionally; on Linux/macOS that let same-name-different-case siblings pass as in-base. Now Ordinal on non-Windows.