Implement encryption oracle for challenge 11.

src/set2.rs

@@ -1,7 +1,8 @@
-#![allow(dead_code)]
 use crate::bytes::Bytes;
 use crate::bytes_base64::BytesBase64;
 use crate::cbs;
+use crate::ecb;
+use rand::Rng;
 
 pub fn challenge9() {
     let mut bytes = Bytes::from_utf8("YELLOW SUBMARINE");
@@ -31,5 +32,36 @@ pub fn challenge10() {
 }
 
 pub fn challenge11() {
-    println!("[tbd] Challenge 11: TBD!");
+    enum EncryptionType {
+        CBS,
+        ECB,
+    }
+    fn random_bytes(count: usize) -> Vec<u8> {
+        (0..count)
+            .map(|_| rand::thread_rng().gen_range(0..255))
+            .collect()
+    }
+
+    fn pad_data(mut v: Vec<u8>) -> Bytes {
+        let pre_count: usize = rand::thread_rng().gen_range(5..10);
+        let post_count: usize = rand::thread_rng().gen_range(5..10);
+        let mut pre_pad = random_bytes(pre_count);
+        let mut post_pad = random_bytes(post_count);
+        pre_pad.append(&mut v);
+        pre_pad.append(&mut post_pad);
+        Bytes(pre_pad)
+    }
+
+    fn encryption_oracle(Bytes(data): &Bytes) -> (Bytes, EncryptionType) {
+        let zero_or_one: u32 = rand::thread_rng().gen_range(0..2);
+        let padded_data = pad_data(data.to_vec());
+        let key = Bytes(random_bytes(16));
+        let (data, encryption_type) = if zero_or_one == 1 {
+            (ecb::encrypt(&key, &padded_data), EncryptionType::ECB)
+        } else {
+            let iv = Bytes(random_bytes(16));
+            (cbs::encrypt(&key, &iv, &padded_data), EncryptionType::CBS)
+        };
+        (data, encryption_type)
+    }
 }