problem 10

1 files changed, 27 insertions, 0 deletions

diff --git a/src/aes.rs b/src/aes.rs
index f38bb6a..1774f02 100644
--- a/src/aes.rs
+++ b/src/aes.rs
@@ -1,6 +1,8 @@
 use openssl;
 use std::collections::HashSet;
 
+use primitives::fixed_xor;
+
 pub fn decrypt_aes_128_ecb (bytes: &[u8], key: &[u8]) -> Vec<u8> {
     return openssl::crypto::symm::decrypt(
         openssl::crypto::symm::Type::AES_128_ECB,
@@ -10,6 +12,31 @@ pub fn decrypt_aes_128_ecb (bytes: &[u8], key: &[u8]) -> Vec<u8> {
     )
 }
 
+pub fn decrypt_aes_128_cbc (bytes: &[u8], key: &[u8], iv: &[u8]) -> Vec<u8> {
+    let mut prev = iv.clone();
+    let mut plaintext = vec![];
+    for block in bytes.chunks(16) {
+        // XXX not sure what's going on here - decrypt_aes_128_ecb doesn't
+        // decrypt the last block?
+        let double_block: Vec<u8> = block
+            .iter()
+            .chain(block.iter()).map(|x| *x)
+            .collect();
+        let plaintext_block = fixed_xor(
+            &decrypt_aes_128_ecb(&double_block[..], key)[..],
+            prev
+        );
+        for &c in &plaintext_block[..16] {
+            plaintext.push(c);
+        }
+        prev = block.clone();
+    }
+    let padding = plaintext[plaintext.len() - 1];
+    let new_len = plaintext.len() - padding as usize;
+    plaintext.truncate(new_len);
+    return plaintext;
+}
+
 pub fn find_aes_128_ecb_encrypted_string (inputs: &[Vec<u8>]) -> Vec<u8> {
     let mut max_dups = 0;
     let mut found = vec![];