GHSA-6cqf-375w-639g Gitea: RSS/Atom feed handlers bypass API-token scope & public-only confinement (incomplete fix of #37698)

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

Summary Gitea's RSS/Atom feed handlers accept API-token Basic auth but perform no token-scope or public-only enforcement. A personal access token that is correctly blocked (HTTP 403) from a private repository on `/raw`, `/media`, `/archive`, and `/releases/download/...` — because it is marked *public-only* or lacks the `repository` scope category — still returns that repository's private content through the feed routes. This is a token-confinement bypass and appears to be an incomplete fix of #37698, which added that scope enforcement to the download handlers but not to the sibling feed handlers. This is not a cross-user access bug: the requesting account must still legitimately have repo read access (`RepoAssignment` + `reqUnitCodeReader` are enforced). What is bypassed is the guarantee that a *confined* token cannot reach private content — which is exactly the property #37698 was shipped to provide for downloads, and which matters when such a token is handed to a third-party service/CI, leaked, or used in a lower-trust integration. Details 37698 added `context.CheckTokenScopes` / `CheckRepoScopedToken` (`services/context/permission.go`) to the raw / media / archive / attachment download handlers, so a public-only or wrong-scope-category token cannot read private-repo content even when the owning user otherwise has access. The feed handlers are registered with `webAuth.AllowBasic` (so they accept token Basic auth) but call no scope / public-only check. A grep for `CheckTokenScopes` / `CheckRepoScopedToken` / `IsApiToken` across `routers/web/feed/` and the release feed handlers returns nothing. Affected routes (all token-reachable via `webAuth.AllowBasic`, none call the scope check): | Route | Handler | Private data exposed | |---|---|---| | `GET /{owner}/{repo}.rss` / `.atom` | `repo.Home` → `handleRepoHomeFeed` (`view_home.go`) | last-10 commits: SHA, full message, author name + email | | `GET /{owner}/{repo}/rss/branch/*`, `/atom/branch/*` | `feed.RenderBranchFeed*` → `ShowBranchFeed` (`routers/web/feed/branch.go`) | same commit data, any branch | | `GET /{owner}/{repo}/releases.rss` / `.atom` | `ReleasesFeedRSS/Atom` (`routers/web/repo/release.go`) → `ShowReleaseFeed` | private release names, notes, descriptions | | `GET /{owner}/{repo}/tags.rss` / `.atom` | `TagsListFeedRSS/Atom` → `ShowReleaseFeed` | private tag names + messages | | `GET /{user}.rss` / `.atom` | `showUserFeed` (`routers/web/feed/profile.go`), `includePrivate = self \|\| admin` | the token owner's private cross-repo activity stream | Inconsistency that pins this down: the branch-feed routes sit in the same route group as `/raw`, `/media`, `/archive` (all of which call `checkDownloadTokenScope`), and `releases.rss` sits next to `/releases/attachments/{uuid}` and `/releases/download/...` (both go through `ServeAttachment` → scope check). Only the feeds were missed. The API equivalents (`ListReleases` / `ListTags`) are scope-gated via `tokenRequiresScopes`. Two distinct confinement bypasses: 1. Public-only bypass. A token created with the *public-only* option is blocked (403) from a private repo on `/raw`, `/archive`, `/releases/download/...`, but returns private commit / release data via `.../releases.rss`, `.../rss/branch/*`, `/{owner}/{repo}.rss`, and the owner's private activity via `/{user}.rss`. 2. Scope-category bypass. A token scoped to only e.g. `read:issue` (no `read:repository`) is rejected by the download handlers but reads repository commit/release content via the feeds. PoC Verified live against the official `gitea/gitea:1.26.2` Docker image (sqlite, feeds enabled). Setup: non-admin user `alice`; private repo `alice/secret` with a commit `"SECRET-COMMIT-MARKER ..."` (file `secret.txt`) and a release `"Private Release"` / body `"SECRET-RELEASE-MARKER ..."`. Two confined personal access tokens, both sent via HTTP Basic so the auth method is identical across download and feed — only the route differs: • Token A: scopes `["public-only", "read:repository"]` • Token B: scopes `["read:issue"]` ```bash Token A — download is correctly blocked, feeds leak private content: curl -u alice:$TOKEN_A https:///alice/secret/raw/branch/main/secret.txt # => 403 (fix works) curl -u alice:$TOKEN_A https:///alice/secret/rss/branch/main # => 200, SECRET-COMMIT-MARKER ... curl -u alice:$TOKEN_A https:///alice/secret/releases.rss # => 200, SECRET-RELEASE-MARKER ... curl -u alice:$TOKEN_A "https:///alice.rss" # => 200, private activity Token B — wrong scope category, same split: curl -u alice:$TOKEN_B https:///alice/secret/raw/branch/main/secret.txt # => 403 curl -u alice:$TOKEN_B https:///alice/secret/rss/branch/main # => 200, private commit leaked ``` Anonymous baseline returns 404 on the repo feeds (data is genuinely private) and a marker-free 200 on `/alice.rss` (public activity only) — confirming the leak is gated only by the missing token check. Impact Information disclosure of private commit metadata (SHA, message, author name+email), release/tag notes, and the owner's private activity stream, to the holder of a confined token that was specifically configured *not* to reach private content. Not raw file blobs (feeds don't serve file contents). Requires a token belonging to an account that already has repo read access, so the realistic threat is a leaked / shared / lower-trust token rather than an anonymous attacker — which is precisely the threat model #37698 addressed for downloads. Suggested remediation Add a token-scope check at the top of each feed handler, mirroring `checkDownloadTokenScope`: ```go if context.CheckRepoScopedToken(ctx, ctx.Repo.Repository, auth_model.Read); ctx.Written() { return } ``` for `ShowBranchFeed`, `ShowRepoFeed`, `ShowFileFeed`, `ShowReleaseFeed` (repo feeds). For the user feed, gate `includePrivate` behind a non-public-only token (or require the `user` / `repository` scope) so a confined token can't pull private activity.