fix: correct webhook signature verification to RSA-PKCS1v15+SHA-256
GHL's x-wh-signature uses RSA-PKCS1v15 + SHA-256, not Ed25519. The previous implementation parsed the wrong key type and would reject all incoming webhooks in production. Changes: - webhook.go: switch x-wh-signature verification to RSA-PKCS1v15+SHA-256 - webhook.go: add optional Ed25519 path for X-GHL-Signature (July 2026+) - config.go: add optional GHL_WEBHOOK_ED25519_KEY for future migration - main.go: pass ed25519 key to NewWebhookHandler - webhook_test.go: update test helpers to use RSA keys Co-Authored-By: SideKx <sidekx.ai@sds.dev>
This commit is contained in:
Head of Product & Engineering
parent
221cd94999
commit
a3b14f8a2a
@ -54,7 +54,7 @@ func run() error {
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ghlAPI := ghl.NewAPIClient()
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oauthHandler := ghl.NewOAuthHandler(cfg.GHLClientID, cfg.GHLClientSecret, cfg.BaseURL, cfg.GHLConversationProviderID, s)
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webhookHandler, err := ghl.NewWebhookHandler(cfg.GHLWebhookPublicKey, castClient, ghlAPI, oauthHandler, s)
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webhookHandler, err := ghl.NewWebhookHandler(cfg.GHLWebhookPublicKey, cfg.GHLWebhookEd25519Key, castClient, ghlAPI, oauthHandler, s)
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if err != nil {
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return fmt.Errorf("webhook handler: %w", err)
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}
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@ -14,6 +14,9 @@ type Config struct {
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GHLClientSecret string
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GHLWebhookPublicKey string
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GHLConversationProviderID string
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// GHLWebhookEd25519Key is the PEM-encoded Ed25519 public key for X-GHL-Signature verification.
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// Optional until GHL activates this header (expected July 2026).
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GHLWebhookEd25519Key string
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CastAPIKey string
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CastAPIURL string
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CastSenderID string
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@ -33,6 +36,7 @@ func Load() (*Config, error) {
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GHLClientSecret: os.Getenv("GHL_CLIENT_SECRET"),
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GHLWebhookPublicKey: os.Getenv("GHL_WEBHOOK_PUBLIC_KEY"),
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GHLConversationProviderID: os.Getenv("GHL_CONVERSATION_PROVIDER_ID"),
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GHLWebhookEd25519Key: os.Getenv("GHL_WEBHOOK_ED25519_KEY"),
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CastAPIKey: os.Getenv("CAST_API_KEY"),
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CastAPIURL: getEnvDefault("CAST_API_URL", "https://api.cast.ph"),
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CastSenderID: os.Getenv("CAST_SENDER_ID"),
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@ -2,7 +2,10 @@ package ghl
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import (
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"context"
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"crypto"
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"crypto/ed25519"
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"crypto/rsa"
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"crypto/sha256"
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"crypto/x509"
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"encoding/base64"
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"encoding/json"
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@ -28,13 +31,14 @@ type seenEntry struct {
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// WebhookHandler handles inbound GHL webhook deliveries.
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//
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// Signature verification supports two GHL schemes:
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// - x-wh-signature: Ed25519 (current GHL scheme, key from Marketplace app settings)
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// - X-GHL-Signature: Ed25519 (GHL next-gen header name, active from July 2026)
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// - x-wh-signature: RSA-PKCS1v15 + SHA-256 (current scheme; static key from GHL docs)
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// - X-GHL-Signature: Ed25519 (GHL next-gen header, active July 2026; optional key)
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//
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// Both headers use the same Ed25519 public key configured via GHL_WEBHOOK_PUBLIC_KEY.
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// The handler checks X-GHL-Signature first; if absent it falls back to x-wh-signature.
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// The handler checks X-GHL-Signature first (if an Ed25519 key is configured),
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// then falls back to x-wh-signature (RSA).
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type WebhookHandler struct {
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webhookKey ed25519.PublicKey // Ed25519 key for both x-wh-signature and X-GHL-Signature
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rsaKey *rsa.PublicKey // RSA key for x-wh-signature (current GHL scheme)
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ed25519Key ed25519.PublicKey // Ed25519 key for X-GHL-Signature (July 2026+), nil if not configured
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castClient *castclient.Client
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ghlAPI *APIClient
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oauthHandler *OAuthHandler
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@ -43,14 +47,26 @@ type WebhookHandler struct {
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seenMessages map[string]seenEntry
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}
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// NewWebhookHandler parses pubKeyPEM (Ed25519 PKIX) and wires all dependencies.
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func NewWebhookHandler(pubKeyPEM string, castClient *castclient.Client, ghlAPI *APIClient, oauth *OAuthHandler, store TokenStore) (*WebhookHandler, error) {
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key, err := parseEd25519PublicKey(pubKeyPEM)
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// NewWebhookHandler parses rsaKeyPEM (RSA PKIX) and wires all dependencies.
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// ed25519KeyPEM is optional (empty string = not configured); provide it when
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// GHL activates X-GHL-Signature (expected July 2026).
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func NewWebhookHandler(rsaKeyPEM string, ed25519KeyPEM string, castClient *castclient.Client, ghlAPI *APIClient, oauth *OAuthHandler, store TokenStore) (*WebhookHandler, error) {
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rsaKey, err := parseRSAPublicKey(rsaKeyPEM)
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if err != nil {
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return nil, fmt.Errorf("failed to parse webhook public key: %w", err)
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return nil, fmt.Errorf("failed to parse webhook RSA public key: %w", err)
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}
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var ed25519Key ed25519.PublicKey
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if ed25519KeyPEM != "" {
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ed25519Key, err = parseEd25519PublicKey(ed25519KeyPEM)
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if err != nil {
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return nil, fmt.Errorf("failed to parse webhook Ed25519 public key: %w", err)
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}
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}
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return &WebhookHandler{
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webhookKey: key,
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rsaKey: rsaKey,
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ed25519Key: ed25519Key,
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castClient: castClient,
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ghlAPI: ghlAPI,
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oauthHandler: oauth,
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@ -171,13 +187,26 @@ func (h *WebhookHandler) updateStatus(ctx context.Context, webhook OutboundMessa
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slog.Info("webhook: message status updated", "message_id", webhook.MessageID, "status", status)
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}
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// verifyIncomingSignature checks X-GHL-Signature first, then x-wh-signature.
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// Both use the same Ed25519 key from GHL Marketplace app settings.
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// verifyIncomingSignature checks X-GHL-Signature (Ed25519) first when configured,
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// then falls back to x-wh-signature (RSA-PKCS1v15 + SHA-256).
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func (h *WebhookHandler) verifyIncomingSignature(r *http.Request, body []byte) bool {
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if sig := r.Header.Get("X-GHL-Signature"); sig != "" {
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if sig := r.Header.Get("X-GHL-Signature"); sig != "" && h.ed25519Key != nil {
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return h.verifyEd25519(body, sig)
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}
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return h.verifyEd25519(body, r.Header.Get("x-wh-signature"))
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return h.verifyRSA(body, r.Header.Get("x-wh-signature"))
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}
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// verifyRSA verifies a base64-encoded RSA-PKCS1v15 + SHA-256 signature over body.
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func (h *WebhookHandler) verifyRSA(body []byte, signatureB64 string) bool {
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if signatureB64 == "" {
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return false
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}
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sigBytes, err := base64.StdEncoding.DecodeString(signatureB64)
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if err != nil {
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return false
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}
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hash := sha256.Sum256(body)
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return rsa.VerifyPKCS1v15(h.rsaKey, crypto.SHA256, hash[:], sigBytes) == nil
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}
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// verifyEd25519 verifies a raw Ed25519 signature (base64-encoded) over body.
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@ -189,7 +218,7 @@ func (h *WebhookHandler) verifyEd25519(body []byte, signatureB64 string) bool {
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if err != nil {
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return false
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}
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return ed25519.Verify(h.webhookKey, body, sigBytes)
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return ed25519.Verify(h.ed25519Key, body, sigBytes)
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}
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func (h *WebhookHandler) HandleUninstall(w http.ResponseWriter, r *http.Request) {
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@ -230,9 +259,28 @@ func (h *WebhookHandler) HandleUninstall(w http.ResponseWriter, r *http.Request)
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w.WriteHeader(http.StatusOK)
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}
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// parseEd25519PublicKey decodes a PEM-encoded PKIX Ed25519 public key.
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// parseRSAPublicKey decodes a PEM-encoded PKIX RSA public key.
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// Tolerates literal \n sequences in the input (common when stored as a single
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// line in a .env file).
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func parseRSAPublicKey(pemStr string) (*rsa.PublicKey, error) {
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pemStr = strings.ReplaceAll(pemStr, `\n`, "\n")
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block, _ := pem.Decode([]byte(pemStr))
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if block == nil {
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return nil, fmt.Errorf("failed to decode PEM block")
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}
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pub, err := x509.ParsePKIXPublicKey(block.Bytes)
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if err != nil {
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return nil, fmt.Errorf("failed to parse public key: %w", err)
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}
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rsaPub, ok := pub.(*rsa.PublicKey)
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if !ok {
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return nil, fmt.Errorf("key is not RSA (got %T)", pub)
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}
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return rsaPub, nil
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}
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// parseEd25519PublicKey decodes a PEM-encoded PKIX Ed25519 public key.
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// Tolerates literal \n sequences in the input.
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func parseEd25519PublicKey(pemStr string) (ed25519.PublicKey, error) {
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pemStr = strings.ReplaceAll(pemStr, `\n`, "\n")
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block, _ := pem.Decode([]byte(pemStr))
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@ -1,8 +1,10 @@
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package ghl
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import (
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"crypto/ed25519"
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"crypto"
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"crypto/rand"
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"crypto/rsa"
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"crypto/sha256"
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"crypto/x509"
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"encoding/base64"
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"encoding/pem"
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@ -15,13 +17,13 @@ import (
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"git.sds.dev/CAST/cast-ghl-plugin/internal/store"
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)
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func generateTestKeyPair(t *testing.T) (ed25519.PrivateKey, string) {
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func generateTestKeyPair(t *testing.T) (*rsa.PrivateKey, string) {
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t.Helper()
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pubKey, privKey, err := ed25519.GenerateKey(rand.Reader)
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privKey, err := rsa.GenerateKey(rand.Reader, 2048)
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if err != nil {
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t.Fatalf("failed to generate Ed25519 key: %v", err)
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t.Fatalf("failed to generate RSA key: %v", err)
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}
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pubBytes, err := x509.MarshalPKIXPublicKey(pubKey)
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pubBytes, err := x509.MarshalPKIXPublicKey(&privKey.PublicKey)
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if err != nil {
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t.Fatalf("failed to marshal public key: %v", err)
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}
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@ -29,9 +31,13 @@ func generateTestKeyPair(t *testing.T) (ed25519.PrivateKey, string) {
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return privKey, string(pemBlock)
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}
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func signPayload(t *testing.T, privKey ed25519.PrivateKey, body []byte) string {
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func signPayload(t *testing.T, privKey *rsa.PrivateKey, body []byte) string {
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t.Helper()
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sig := ed25519.Sign(privKey, body)
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hash := sha256.Sum256(body)
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sig, err := rsa.SignPKCS1v15(rand.Reader, privKey, crypto.SHA256, hash[:])
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if err != nil {
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t.Fatalf("failed to sign payload: %v", err)
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}
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return base64.StdEncoding.EncodeToString(sig)
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}
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@ -39,7 +45,7 @@ func newTestHandler(t *testing.T, pubPEM string) *WebhookHandler {
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t.Helper()
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ms := &inMemStore{}
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oauth := NewOAuthHandler("c", "s", "http://x", "p", ms)
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handler, err := NewWebhookHandler(pubPEM, castclient.NewClient("http://localhost:1", "k", ""), NewAPIClient(), oauth, ms)
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handler, err := NewWebhookHandler(pubPEM, "", castclient.NewClient("http://localhost:1", "k", ""), NewAPIClient(), oauth, ms)
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if err != nil {
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t.Fatalf("failed to create handler: %v", err)
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}
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@ -161,7 +167,7 @@ func TestHandleUninstall_ValidSignature(t *testing.T) {
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token: &store.TokenRecord{LocationID: "loc-uninstall"},
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}
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oauth := NewOAuthHandler("c", "s", "http://x", "p", ms)
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handler, err := NewWebhookHandler(pubPEM, castclient.NewClient("http://localhost:1", "k", ""), NewAPIClient(), oauth, ms)
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handler, err := NewWebhookHandler(pubPEM, "", castclient.NewClient("http://localhost:1", "k", ""), NewAPIClient(), oauth, ms)
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if err != nil {
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t.Fatalf("failed to create handler: %v", err)
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}
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@ -188,7 +194,7 @@ func TestHandleUninstall_InvalidSignature(t *testing.T) {
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_, pubPEM := generateTestKeyPair(t)
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ms := &inMemStore{}
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oauth := NewOAuthHandler("c", "s", "http://x", "p", ms)
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handler, err := NewWebhookHandler(pubPEM, castclient.NewClient("http://localhost:1", "k", ""), NewAPIClient(), oauth, ms)
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handler, err := NewWebhookHandler(pubPEM, "", castclient.NewClient("http://localhost:1", "k", ""), NewAPIClient(), oauth, ms)
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if err != nil {
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t.Fatalf("failed to create handler: %v", err)
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}
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