add overriding of ARI response (#501)

Fixes #486

This moves the GetCertificateBySerial call earlier, which means that
call needs to succeed even for revoked certificates. So this also
follows up on #252 by keeping revoked certs in the primary
certificatesByID map (while still adding them to the
revokedCertificatesByID map).

core/types.go

@@ -149,6 +149,8 @@ type Certificate struct {
 	DER          []byte
 	IssuerChains [][]*Certificate
 	AccountID    string
+	// When non-empty, this is the ARI response sent for this certificate.
+	ARIResponse string
 }
 
 func (c Certificate) PEM() []byte {

db/memorystore.go

@@ -413,7 +413,6 @@ func (m *MemoryStore) RevokeCertificate(cert *core.RevokedCertificate) {
 	m.Lock()
 	defer m.Unlock()
 	m.revokedCertificatesByID[cert.Certificate.ID] = cert
-	delete(m.certificatesByID, cert.Certificate.ID)
 }
 
 /*
@@ -549,3 +548,19 @@ func (m *MemoryStore) IsDomainBlocked(name string) bool {
 
 	return false
 }
+
+// SetARIResponse looks up a certificate by serial number and sets its ARI response field
+func (m *MemoryStore) SetARIResponse(serial *big.Int, ariResponse string) error {
+	m.Lock()
+	defer m.Unlock()
+
+	for _, cert := range m.certificatesByID {
+		if cert.Cert.SerialNumber.Cmp(serial) == 0 {
+			cert.ARIResponse = ariResponse
+			return nil
+		}
+	}
+
+	// Certificate not found
+	return fmt.Errorf("certificate with serial number %s not found", serial.String())
+}

wfe/wfe.go

@@ -57,7 +57,7 @@ const (
 	// Draft or likely-to-change paths
 	renewalInfoPath = "/draft-ietf-acme-ari-03/renewalInfo/"
 
-	// Theses entrypoints are not a part of the standard ACME endpoints,
+	// These entrypoints are not a part of the standard ACME endpoints,
 	// and are exposed by Pebble as an integration test tool. We export
 	// RootCertPath so that the pebble binary can reference it.
 	RootCertPath         = "/roots/"
@@ -65,6 +65,10 @@ const (
 	intermediateCertPath = "/intermediates/"
 	intermediateKeyPath  = "/intermediate-keys/"
 	certStatusBySerial   = "/cert-status-by-serial/"
+	// Post certificate PEM and desired literal response for renewal info
+	// (the renewal info response is not validated so may be intentionally
+	// malformed).
+	setRenewalInfoPath = "/set-renewal-info/"
 
 	// How long do pending authorizations last before expiring?
 	pendingAuthzExpire = time.Hour
@@ -542,6 +546,9 @@ func (wfe *WebFrontEndImpl) ManagementHandler() http.Handler {
 	wfe.HandleManagementFunc(m, intermediateCertPath, wfe.handleCert(wfe.ca.GetIntermediateCert, intermediateCertPath))
 	wfe.HandleManagementFunc(m, intermediateKeyPath, wfe.handleKey(wfe.ca.GetIntermediateKey, intermediateKeyPath))
 	wfe.HandleManagementFunc(m, certStatusBySerial, wfe.handleCertStatusBySerial)
+
+	// POST only handlers
+	wfe.HandleFunc(m, setRenewalInfoPath, wfe.SetRenewalInfo, http.MethodPost)
 	return m
 }
 
@@ -1903,7 +1910,18 @@ func (wfe *WebFrontEndImpl) RenewalInfo(_ context.Context, response http.Respons
 		return
 	}
 
-	renewalInfo, err := wfe.determineARIWindow(certID)
+	cert := wfe.db.GetCertificateBySerial(certID.SerialNumber)
+	if cert == nil {
+		wfe.sendError(acme.NotFoundProblem("failed to retrieve existing certificate serial"), response)
+		return
+	}
+
+	if cert.ARIResponse != "" {
+		_, _ = response.Write([]byte(cert.ARIResponse))
+		return
+	}
+
+	renewalInfo, err := wfe.determineARIWindow(certID, cert)
 	if err != nil {
 		wfe.sendError(acme.InternalErrorProblem(fmt.Sprintf("Error determining renewal window: %s", err)), response)
 		return
@@ -1917,7 +1935,47 @@ func (wfe *WebFrontEndImpl) RenewalInfo(_ context.Context, response http.Respons
 	}
 }
 
-func (wfe *WebFrontEndImpl) determineARIWindow(id *core.CertID) (*core.RenewalInfo, error) {
+// SetRenewalInfo overrides the default ARI response for a certificate.
+func (wfe *WebFrontEndImpl) SetRenewalInfo(_ context.Context, response http.ResponseWriter, request *http.Request) {
+	body, err := io.ReadAll(request.Body)
+	if err != nil {
+		wfe.sendError(acme.InternalErrorProblem("Error reading body"), response)
+	}
+
+	var reqJSON struct {
+		Certificate string // in PEM form
+		ARIResponse string // can be anything, even malformed JSON, so that users can test client response to malformed data
+	}
+	err = json.Unmarshal(body, &reqJSON)
+	if err != nil {
+		wfe.sendError(acme.MalformedProblem("Error unmarshaling request body"), response)
+		return
+	}
+
+	// Decode and parse the PEM certificate
+	block, _ := pem.Decode([]byte(reqJSON.Certificate))
+	if block == nil || block.Type != "CERTIFICATE" {
+		wfe.sendError(acme.MalformedProblem("Error decoding certificate PEM"), response)
+		return
+	}
+
+	cert, err := x509.ParseCertificate(block.Bytes)
+	if err != nil {
+		wfe.sendError(acme.MalformedProblem("Error parsing certificate"), response)
+		return
+	}
+
+	// Look up certificate by serial number and update response
+	err = wfe.db.SetARIResponse(cert.SerialNumber, reqJSON.ARIResponse)
+	if err != nil {
+		wfe.sendError(acme.NotFoundProblem(err.Error()), response)
+		return
+	}
+
+	response.WriteHeader(http.StatusOK)
+}
+
+func (wfe *WebFrontEndImpl) determineARIWindow(id *core.CertID, cert *core.Certificate) (*core.RenewalInfo, error) {
 	if id == nil {
 		return nil, errors.New("CertID was nil")
 	}
@@ -1928,11 +1986,6 @@ func (wfe *WebFrontEndImpl) determineARIWindow(id *core.CertID) (*core.RenewalIn
 		return core.RenewalInfoImmediate(time.Now().In(time.UTC)), nil
 	}
 
-	cert := wfe.db.GetCertificateBySerial(id.SerialNumber)
-	if cert == nil {
-		return nil, errors.New("failed to retrieve existing certificate serial")
-	}
-
 	return core.RenewalInfoSimple(cert.Cert.NotBefore, cert.Cert.NotAfter), nil
 }