GHSA-8p9h-49rc-qgxj

### 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 |

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#### 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

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#### 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" ```

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#### 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.

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#### 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

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**Step 1 — Confirm the target repository is private**

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**Step 2 — Clone the repository**

```bash git clone http://USER:PASSWORD@<gitea-host>/OWNER/REPO.git /tmp/target-repo cd /tmp/target-repo ```

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**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" ```

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**Step 4 — Execute the exploit push**

```bash # Make the repository public git push http://USER:PASSWORD@<gitea-host>/OWNER/REPO.git main \ -o repo.private=false

# The push completes with a normal success message: # remote: Processed 1 references in total # To http://<gitea-host>/OWNER/REPO.git # abc1234..def5678 main -> main ```

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**Step 5 — Verify the repository is now public**

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**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**

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#### 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 |

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#### 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.