Implement challenge 9 pkcs 7 padding.

src/bytes.rs

@@ -67,6 +67,14 @@ impl Bytes {
         r
     }
 
+    pub fn pad_pkcs7(&mut self, block_size: usize) -> () {
+        let Bytes(v) = self;
+        let padding_value = (block_size - v.len() % block_size) as u8;
+        for _ in 0..padding_value {
+            v.push(padding_value);
+        }
+    }
+
     pub fn xor(Bytes(a): &Bytes, Bytes(b): &Bytes) -> Bytes {
         Bytes(
             Iterator::zip(a.iter(), b.iter())

src/main.rs

@@ -1,6 +1,7 @@
 mod bytes;
 mod bytes_base64;
 mod set1;
+mod set2;
 
 fn main() {
     set1::challenge1();
@@ -11,4 +12,6 @@ fn main() {
     set1::challenge6();
     set1::challenge7();
     set1::challenge8();
+    set2::challenge9();
+    set2::challenge10();
 }

src/set2.rs

@@ -0,0 +1,11 @@
+use crate::bytes::Bytes;
+
+pub fn challenge9() {
+    let mut bytes = Bytes::from_utf8("YELLOW SUBMARINE");
+    bytes.pad_pkcs7(20);
+    println!("[okay] Challenge 9: {:?}", bytes.to_utf8());
+}
+
+pub fn challenge10() {
+    println!("[TBD] Challenge 10: TBD");
+}