completed set2. challenge 15

wait this is not the given order. Whaaats upp? Carzy guy!

1 files changed, 28 insertions, 0 deletions

diff --git a/lib/lib2.c b/lib/lib2.c
index fe65bb8..49f7363 100644
--- a/lib/lib2.c
+++ b/lib/lib2.c
@@ -24,6 +24,34 @@ char *pkcs7_padding(char *string, int length_string, int blocksize)
 }
 
 /**
+ * unpadd a string
+ * @param in string which should be unpadded
+ * @param length_in length of paramter length_in
+ * @param unpadded place where the unpadded text should be stored
+ * @param blocksize size of the block to which should be padded
+ */
+int valid_pkcs7_padding(const char *in, int length_in, char *unpadded, int blocksize)
+{
+	int i, padding_length;
+	// look how many equal bytes are at the end
+	// ignore last byte \0
+	for(i=length_in-1;i>0;i--) {
+		if(in[i] != in[i-1])
+			break;
+	}
+	
+	padding_length = length_in - i;
+	if ((length_in % padding_length) != 0)
+		return 0;
+
+	if(in[length_in-1] != padding_length)
+		return 0;
+
+	memcpy(unpadded, in, (length_in-padding_length));
+	return 1;
+}
+
+/**
  * decrypts content which is encrypted in AES CBC mode
  * @param in input content
  * @param length_in length of parametere in