fix(security): restrict core-ref to existing tags only#48
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fix(security): restrict core-ref to existing tags only#48DeepDiver1975 wants to merge 1 commit intomainfrom
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Replace the loose character-allowlist validation from the earlier fix with a two-stage check that: 1. Strips an optional refs/tags/ prefix then rejects any remaining slash, blocking branch refs (refs/heads/...) and PR head refs (refs/pull/N/head) which pass character-only validation but point at mutable or attacker-controlled code. 2. Uses git ls-remote --tags to confirm the value resolves to an actual annotated or lightweight tag in owncloud/core, so a caller cannot silently supply a non-existent or branch-shaped ref. Also updates input descriptions to document the tag-only constraint.
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Summary
Supersedes #45, which added a character-allowlist check that is insufficient on its own.
The root problem:
core-refis passed directly toactions/checkout'sref:parameter, thenmakeruns against the checked-out code. An attacker who can influence thecore-refvalue can point the checkout at code they control, getting arbitrary execution via the Makefile.Why #45's regex is not enough:
A character-allowlist (
[a-zA-Z0-9._/=-]+) blocks obviously malformed values but still permits:main(mutable — can change under you)refs/pull/9999/head— this is the main attack vector: an attacker opens a PR againstowncloud/corewith a maliciousMakefile, then pointscore-refatrefs/pull/9999/head. GitHub creates this ref automatically for every open PR, no merge required.This PR's fix — two-stage validation:
Slash check after prefix stripping — strips the optional
refs/tags/prefix then rejects any remaining/. This blocksrefs/pull/N/head,refs/heads/branch, and any other full ref path while still accepting short tag names (v10.14.0) and the explicitrefs/tags/v10.14.0form.git ls-remote --tagsexistence check — confirms the value resolves to an actual tag inowncloud/core. This prevents:main) — these have no matchingrefs/tags/mainentry and will failWhat callers need to do
No change for callers already using tag names like
v10.14.0. Callers using branch names or omittingcore-refentirely (defaults to'', which skips validation) are unaffected.Test plan
core-ref: v10.14.0— passes (existing tag, no slash)core-ref: refs/tags/v10.14.0— passes (prefix stripped, tag verified)core-ref: refs/pull/9999/head— rejected at slash checkcore-ref: main— rejected atgit ls-remotecheck (norefs/tags/mainin owncloud/core)core-ref: v99.99.99— rejected atgit ls-remotecheck (tag does not exist)core-ref: ''(default) — validation step skipped entirely🤖 Generated with Claude Code