GHSA-p4mj-98mv-xq26

Описание

Description

Gitea implements a special behavior for requests containing the ?go-get=1 query parameter. This parameter is sent by the Go toolchain (go get, go install) to discover VCS metadata for module imports. When Gitea detects this parameter in the HTTP request path for a repository, it bypasses the normal authentication and authorization stack and returns an HTTP 200 response containing <meta name="go-import"> and <meta name="go-source"> tags — regardless of whether:

• The repository is private
• The requesting user is authenticated
• The requesting user has any permission on the repository

The entry point is routers/web/repo/githttp.go:63–66:

The EarlyResponseForGoGetMeta function (services/context/repo.go:379–396) is called unconditionally, and the function's own docstring documents the intended behavior:

The function also appears at services/context/repo.go:444, 516, 571 — all repository-scoped route handlers that check ?go-get=1 and call EarlyResponseForGoGetMeta before performing any permission verification.

The metadata returned includes:

1. The full repository name and owner — confirming the repository exists
2. The HTTP clone URL — a fully-formed URL pointing to the repository
3. The source browsing URL templates — which may reveal the default branch name

This allows an unauthenticated attacker to:

1. Confirm existence of any private repository by name
2. Enumerate private repository names through brute-force without triggering authentication failures
3. Harvest clone URLs and default branch names of private repositories

Proof of Concept

Step 1 — Identify a private repository

Any private repository works. For this demonstration, admin/classified-internal is set to private:

Step 2 — Confirm access is denied without authentication

Standard requests to a private repository correctly return 404 for unauthenticated users.

Step 3 — Bypass using go-get parameter

Actual response (HTTP 200):

The response:

• Returns HTTP 200 (not 404) — confirming the repository exists
• Reveals the full clone URL: http://localhost:3000/admin/classified-internal.git
• Reveals the default branch name: main
• Reveals the owner username: admin

This same response is returned whether or not the repository exists — the comment in EarlyResponseForGoGetMeta states it responds identically for both — however in practice, the clone URL generated will be functionally different (a real clone attempt against a non-existent repo fails, while one against a private repo fails only at authentication). An attacker can differentiate using response timing or by attempting git ls-remote.

Step 4 — Enumerate private repositories at scale

Step 5 — Verify the same applies to the main web router

The vulnerability also exists via the standard web router for repository pages:

All return HTTP 200 with the metadata.

Impact Analysis

Direct impact:

Root Cause Analysis

The bypass was introduced intentionally as a workaround for the Go toolchain's limitation of not reading .netrc credentials before deciding whether a module is accessible. The Go go get command probes the VCS endpoint without credentials first; if it gets a 404, it treats the module as non-existent and fails immediately without prompting for credentials.

The workaround — returning metadata unconditionally — was the path of least resistance for enabling private module imports. The unintended consequence is that it creates an unauthenticated information disclosure endpoint for every repository in the instance.

Recommended Fix

The fix requires differentiating between requests that carry authentication credentials and those that do not, before calling EarlyResponseForGoGetMeta.

This approach preserves the go-get functionality for public repositories while protecting private ones. The Go toolchain will fall back to prompting for credentials when it receives a 404, which is the correct behavior for private module imports.