Add test for zero-length padding

square · Aug 18, 2015 · 070d78c · 070d78c
1 parent 0edc31a
commit 070d78c
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Showing 2 changed files with 9 additions and 1 deletion.
diff --git a/cipher/cbc_hmac.go b/cipher/cbc_hmac.go
@@ -183,7 +183,7 @@ func unpadBuffer(buffer []byte, blockSize int) ([]byte, error) {
 	last := buffer[len(buffer)-1]
 	count := int(last)
 
-	if count > blockSize || count > len(buffer) {
+	if count == 0 || count > blockSize || count > len(buffer) {
 		return nil, errors.New("square/go-jose: invalid padding")
 	}
 

diff --git a/cipher/cbc_hmac_test.go b/cipher/cbc_hmac_test.go
@@ -357,6 +357,14 @@ func TestInvalidPadding(t *testing.T) {
 	}
 }
 
+func TestZeroLengthPadding(t *testing.T) {
+	data := make([]byte, 16)
+	data, err := unpadBuffer(data, 16)
+	if err == nil {
+		t.Error("padding with 0x00 should never be valid")
+	}
+}
+
 func benchEncryptCBCHMAC(b *testing.B, keySize, chunkSize int) {
 	key := make([]byte, keySize*2)
 	nonce := make([]byte, 16)