Repository Visibility Manipulation via Git Push Options

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

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:

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

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

Step 3 — Make any commit (the push option rides on a real push)

echo "$(date)" >> .gitkeep
git add .gitkeep
git commit -m "routine update"

Step 4 — Execute the exploit push

# 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

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

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:

// 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:

// 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.

References

• GHSA-8p9h-49rc-qgxj
• https://github.com/go-gitea/gitea/releases/tag/v1.27.0