lib: update Pkcs7PaddingUndo, AESDecryptCBC

Add error as the second return value to Pkcs7PaddingUndo and
AESDecryptCBC.

2 files changed, 7 insertions, 7 deletions

diff --git a/lib/aes.go b/lib/aes.go
index 396ee5c..8c4dd26 100644
--- a/lib/aes.go
+++ b/lib/aes.go
@@ -23,7 +23,7 @@ func AESEncryptCBC(plain, key, iv []byte) []byte {
 	return output
 }
 
-func AESDecryptCBC(cipher, key, iv []byte) []byte {
+func AESDecryptCBC(cipher, key, iv []byte) ([]byte, error) {
 	iter := len(cipher) / 16
 
 	lc := iv
@@ -38,9 +38,9 @@ func AESDecryptCBC(cipher, key, iv []byte) []byte {
 	}
 
 	// Undo padding
-	output = Pkcs7PaddingUndo(output)
+	output, err := Pkcs7PaddingUndo(output)
 
-	return output
+	return output, err
 }
 
 func AESEncryptECB(plain, key []byte) []byte {
@@ -72,7 +72,7 @@ func AESDecryptECB(cipher, key []byte) []byte {
 	}
 
 	// Undo padding
-	output = Pkcs7PaddingUndo(output)
+	output, _ = Pkcs7PaddingUndo(output)
 
 	return output
 }
diff --git a/lib/blocks.go b/lib/blocks.go
index 9b184d1..c4d8be1 100644
--- a/lib/blocks.go
+++ b/lib/blocks.go
@@ -112,15 +112,15 @@ func Pkcs7Padding(in []byte, k int) []byte {
 }
 
 // Removes PKCS#7 Padding from input `in`
-func Pkcs7PaddingUndo(in []byte) []byte {
+func Pkcs7PaddingUndo(in []byte) ([]byte, error) {
 	pd := in[len(in)-1] // padding character
 	pl := int(pd)       // padding length
 
 	// Validate
 	for i := len(in) - 1; i >= len(in)-pl; i-- {
 		if in[i] != pd {
-			panic("input is not pkcs#7 padded!")
+			return []byte{}, CPError{"input is not pkcs#7 padded"}
 		}
 	}
-	return in[0:(len(in) - pl)]
+	return in[0:(len(in) - pl)], nil
 }