fix: prevent path traversal in DownloadActionOutputs and validate symlink targets#650
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…ownloadOutputs Two path traversal variants were found in the download path: 1. DownloadActionOutputs passes dir.Path from the ActionResult proto directly to os.RemoveAll via filepath.Join, without validating it through getAbsPath. A malicious remote server could set dir.Path to "../../important_data" to delete arbitrary directories on the client. 2. DownloadOutputs creates symlinks without validating that the symlink target stays within the output directory. A malicious remote server could set SymlinkTarget to "/etc/shadow" or "../../../../etc/passwd" to create symlinks pointing outside the output directory, enabling arbitrary file read/write through symlink following. Both fixes use the same getAbsPath validation introduced in the previous path traversal fix, ensuring all server-controlled paths are validated before use.
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Summary
Two additional path traversal vectors were found in the download code path, both variants of the issue previously fixed in
getAbsPath:1.
DownloadActionOutputs:os.RemoveAllwith unvalidateddir.PathDownloadActionOutputspassesdir.Pathfrom theActionResultproto directly toos.RemoveAllviafilepath.Join, bypassinggetAbsPathvalidation. A malicious remote execution server could setOutputDirectories[].Pathto../../important_datato delete arbitrary directories on the client filesystem.The deletion happens at line 525 before
DownloadOutputs(which validates paths viagetAbsPath) is called at line 529.2.
DownloadOutputs: Symlink target not validated for containmentWhen creating symlinks from remote server output, the symlink placement path (
out.Path) is validated viagetAbsPath, but the symlink target (out.SymlinkTarget) is used directly from the proto without any validation. A malicious server can setSymlinkTargetto/etc/shadowor../../../../etc/passwd, creating symlinks inside the output directory that point to arbitrary locations on the filesystem.Fixes
getAbsPathvalidation inDownloadActionOutputsbeforeos.RemoveAllDownloadOutputsusing the same separator-aware prefix check asgetAbsPath