Check input size to avoid a panic (#3521)

builtin/logical/transit/backend_test.go

@@ -1091,3 +1091,38 @@ func testPolicyFuzzingCommon(t *testing.T, be *backend) {
 	// Wait for them all to finish
 	wg.Wait()
 }
+
+func TestBadInput(t *testing.T) {
+	var b *backend
+	sysView := logical.TestSystemView()
+	storage := &logical.InmemStorage{}
+
+	b = Backend(&logical.BackendConfig{
+		StorageView: storage,
+		System:      sysView,
+	})
+
+	req := &logical.Request{
+		Storage:   storage,
+		Operation: logical.UpdateOperation,
+		Path:      "keys/test",
+	}
+
+	resp, err := b.HandleRequest(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if resp != nil {
+		t.Fatal("expected nil response")
+	}
+
+	req.Path = "decrypt/test"
+	req.Data = map[string]interface{}{
+		"ciphertext": "vault:v1:abcd",
+	}
+
+	_, err = b.HandleRequest(req)
+	if err == nil {
+		t.Fatal("expected error")
+	}
+}

helper/keysutil/policy.go

@@ -675,6 +675,10 @@ func (p *Policy) Decrypt(context, nonce []byte, value string) (string, error) {
 		return "", errutil.InternalError{Err: err.Error()}
 	}
 
+	if len(decoded) < gcm.NonceSize() {
+		return "", errutil.UserError{Err: "invalid ciphertext length"}
+	}
+
 	// Extract the nonce and ciphertext
 	var ciphertext []byte
 	if p.ConvergentEncryption && p.ConvergentVersion < 2 {