From 6954638864781ed4277c800d017119c5c100d3f2 Mon Sep 17 00:00:00 2001
From: Cedric Staub <css@css.bio>
Date: Tue, 26 Jun 2018 11:43:49 -0700
Subject: [PATCH] Fix panic on null (but present) header key

---
 jwe_test.go | 6 ++++++
 shared.go   | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/jwe_test.go b/jwe_test.go
index dc772af..1ada725 100644
--- a/jwe_test.go
+++ b/jwe_test.go
@@ -541,3 +541,9 @@ func TestSampleJose4jJWEMessagesECDH(t *testing.T) {
 		}
 	}
 }
+
+func TestJWEWithNullAlg(t *testing.T) {
+	// {"alg":null,"enc":"A128GCM"}
+	serialized := `{"protected":"eyJhbGciOm51bGwsImVuYyI6IkExMjhHQ00ifQ"}`
+	ParseEncrypted(serialized)
+}
diff --git a/shared.go b/shared.go
index e6ab91d..bbce43f 100644
--- a/shared.go
+++ b/shared.go
@@ -206,7 +206,7 @@ func (parsed rawHeader) set(k HeaderKey, v interface{}) error {
 // getString gets a string from the raw JSON, defaulting to "".
 func (parsed rawHeader) getString(k HeaderKey) string {
 	v, ok := parsed[k]
-	if !ok {
+	if !ok || v == nil {
 		return ""
 	}
 	var s string