diff --git a/acme/rfc8555.go b/acme/rfc8555.go index 073cee58b7..f9d3011ffc 100644 --- a/acme/rfc8555.go +++ b/acme/rfc8555.go @@ -410,3 +410,29 @@ func isAlreadyRevoked(err error) bool { e, ok := err.(*Error) return ok && e.ProblemType == "urn:ietf:params:acme:error:alreadyRevoked" } + +// ListCertAlternates retrieves any alternate certificate chain URLs for the +// given certificate chain URL. These alternate URLs can be passed to FetchCert +// in order to retrieve the alternate certificate chains. +// +// If there are no alternate issuer certificate chains, a nil slice will be +// returned. +func (c *Client) ListCertAlternates(ctx context.Context, url string) ([]string, error) { + if _, err := c.Discover(ctx); err != nil { // required by c.accountKID + return nil, err + } + + res, err := c.postAsGet(ctx, url, wantStatus(http.StatusOK)) + if err != nil { + return nil, err + } + defer res.Body.Close() + + // We don't need the body but we need to discard it so we don't end up + // preventing keep-alive + if _, err := io.Copy(ioutil.Discard, res.Body); err != nil { + return nil, fmt.Errorf("acme: cert alternates response stream: %v", err) + } + alts := linkHeader(res.Header, "alternate") + return alts, nil +} diff --git a/acme/rfc8555_test.go b/acme/rfc8555_test.go index c35118e2d1..07e2f29db2 100644 --- a/acme/rfc8555_test.go +++ b/acme/rfc8555_test.go @@ -882,3 +882,35 @@ func TestRFC_AlreadyRevokedCert(t *testing.T) { t.Fatalf("RevokeCert: %v", err) } } + +func TestRFC_ListCertAlternates(t *testing.T) { + s := newACMEServer() + s.handle("/crt", func(w http.ResponseWriter, r *http.Request) { + w.Header().Set("Content-Type", "application/pem-certificate-chain") + w.Header().Add("Link", `;rel="alternate"`) + w.Header().Add("Link", `; rel="alternate"`) + w.Header().Add("Link", `; rel="index"`) + }) + s.handle("/crt2", func(w http.ResponseWriter, r *http.Request) { + w.Header().Set("Content-Type", "application/pem-certificate-chain") + }) + s.start() + defer s.close() + + cl := &Client{Key: testKeyEC, DirectoryURL: s.url("/")} + crts, err := cl.ListCertAlternates(context.Background(), s.url("/crt")) + if err != nil { + t.Fatalf("ListCertAlternates: %v", err) + } + want := []string{"https://example.com/crt/2", "https://example.com/crt/3"} + if !reflect.DeepEqual(crts, want) { + t.Errorf("ListCertAlternates(/crt): %v; want %v", crts, want) + } + crts, err = cl.ListCertAlternates(context.Background(), s.url("/crt2")) + if err != nil { + t.Fatalf("ListCertAlternates: %v", err) + } + if crts != nil { + t.Errorf("ListCertAlternates(/crt2): %v; want nil", crts) + } +}