problem 25

5 files changed, 142 insertions, 0 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 2fb4b94..bbbd731 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -15,6 +15,10 @@ path = "tests/set2.rs"
 name = "set3"
 path = "tests/set3.rs"
 
+[[test]]
+name = "set4"
+path = "tests/set4.rs"
+
 [dependencies]
 rustc-serialize = "0.3"
 openssl = "0.5"
diff --git a/data/25.txt b/data/25.txt
new file mode 100644
index 0000000..14283df
--- /dev/null
+++ b/data/25.txt
@@ -0,0 +1,79 @@
+I'm back and I'm ringin' the bell 
+A rockin' on the mike while the fly girls yell 
+In ecstasy in the back of me 
+Well that's my DJ Deshay cuttin' all them Z's 
+Hittin' hard and the girlies goin' crazy 
+Vanilla's on the mike, man I'm not lazy. 
+
+I'm lettin' my drug kick in 
+It controls my mouth and I begin 
+To just let it flow, let my concepts go 
+My posse's to the side yellin', Go Vanilla Go! 
+
+Smooth 'cause that's the way I will be 
+And if you don't give a damn, then 
+Why you starin' at me 
+So get off 'cause I control the stage 
+There's no dissin' allowed 
+I'm in my own phase 
+The girlies sa y they love me and that is ok 
+And I can dance better than any kid n' play 
+
+Stage 2 -- Yea the one ya' wanna listen to 
+It's off my head so let the beat play through 
+So I can funk it up and make it sound good 
+1-2-3 Yo -- Knock on some wood 
+For good luck, I like my rhymes atrocious 
+Supercalafragilisticexpialidocious 
+I'm an effect and that you can bet 
+I can take a fly girl and make her wet. 
+
+I'm like Samson -- Samson to Delilah 
+There's no denyin', You can try to hang 
+But you'll keep tryin' to get my style 
+Over and over, practice makes perfect 
+But not if you're a loafer. 
+
+You'll get nowhere, no place, no time, no girls 
+Soon -- Oh my God, homebody, you probably eat 
+Spaghetti with a spoon! Come on and say it! 
+
+VIP. Vanilla Ice yep, yep, I'm comin' hard like a rhino 
+Intoxicating so you stagger like a wino 
+So punks stop trying and girl stop cryin' 
+Vanilla Ice is sellin' and you people are buyin' 
+'Cause why the freaks are jockin' like Crazy Glue 
+Movin' and groovin' trying to sing along 
+All through the ghetto groovin' this here song 
+Now you're amazed by the VIP posse. 
+
+Steppin' so hard like a German Nazi 
+Startled by the bases hittin' ground 
+There's no trippin' on mine, I'm just gettin' down 
+Sparkamatic, I'm hangin' tight like a fanatic 
+You trapped me once and I thought that 
+You might have it 
+So step down and lend me your ear 
+'89 in my time! You, '90 is my year. 
+
+You're weakenin' fast, YO! and I can tell it 
+Your body's gettin' hot, so, so I can smell it 
+So don't be mad and don't be sad 
+'Cause the lyrics belong to ICE, You can call me Dad 
+You're pitchin' a fit, so step back and endure 
+Let the witch doctor, Ice, do the dance to cure 
+So come up close and don't be square 
+You wanna battle me -- Anytime, anywhere 
+
+You thought that I was weak, Boy, you're dead wrong 
+So come on, everybody and sing this song 
+
+Say -- Play that funky music Say, go white boy, go white boy go 
+play that funky music Go white boy, go white boy, go 
+Lay down and boogie and play that funky music till you die. 
+
+Play that funky music Come on, Come on, let me hear 
+Play that funky music white boy you say it, say it 
+Play that funky music A little louder now 
+Play that funky music, white boy Come on, Come on, Come on 
+Play that funky music 
diff --git a/src/crack.rs b/src/crack.rs
index 39a8e1a..abfd84a 100644
--- a/src/crack.rs
+++ b/src/crack.rs
@@ -427,6 +427,14 @@ pub fn recover_mt19937_key_from_time (token: &[u8]) -> Option<u32> {
     return None;
 }
 
+pub fn crack_aes_128_ctr_random_access<F> (ciphertext: &[u8], edit: F) -> Vec<u8> where F: Fn(&[u8], usize, &[u8]) -> Vec<u8> {
+    let empty_plaintext: Vec<u8> = ::std::iter::repeat(b'\x00')
+        .take(ciphertext.len())
+        .collect();
+    let keystream = edit(ciphertext, 0, &empty_plaintext[..]);
+    return fixed_xor(&keystream[..], ciphertext);
+}
+
 fn crack_single_byte_xor_with_confidence (input: &[u8]) -> (u8, f64) {
     let mut min_diff = 100.0;
     let mut best_key = 0;
diff --git a/src/lib.rs b/src/lib.rs
index 2d6ebeb..6cfb2d3 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -42,3 +42,4 @@ pub use crack::recover_mersenne_twister_seed_from_time;
 pub use crack::clone_mersenne_twister_from_output;
 pub use crack::recover_16_bit_mt19937_key;
 pub use crack::recover_mt19937_key_from_time;
+pub use crack::crack_aes_128_ctr_random_access;
diff --git a/tests/set4.rs b/tests/set4.rs
new file mode 100644
index 0000000..3967f85
--- /dev/null
+++ b/tests/set4.rs
@@ -0,0 +1,50 @@
+extern crate matasano;
+extern crate rand;
+
+use rand::Rng;
+
+mod util;
+
+#[test]
+fn problem_25 () {
+    let key = util::random_aes_128_key();
+    let nonce: u64 = rand::thread_rng().gen();
+    let plaintext = util::read("data/25.txt");
+
+    let ciphertext = matasano::aes_128_ctr(&plaintext[..], &key[..], nonce);
+    let edit = |ciphertext: &[u8], offset: usize, newtext: &[u8]| {
+        let block_start_number = offset / 16;
+        let block_start = block_start_number * 16;
+        let block_end_number = (offset + newtext.len() - 1) / 16;
+        let block_end = std::cmp::min(
+            (block_end_number + 1) * 16,
+            ciphertext.len()
+        );
+        let mut plaintext = matasano::aes_128_ctr_with_counter(
+            &ciphertext[block_start..block_end],
+            &key[..],
+            nonce,
+            (offset / 16) as u64
+        );
+        for i in 0..newtext.len() {
+            plaintext[offset - block_start + i] = newtext[i];
+        }
+        let new_ciphertext = matasano::aes_128_ctr_with_counter(
+            &plaintext[..],
+            &key[..],
+            nonce,
+            (offset / 16) as u64
+        );
+
+        return ciphertext
+            .iter()
+            .take(block_start)
+            .chain(new_ciphertext.iter())
+            .chain(ciphertext.iter().skip(block_end))
+            .map(|x| *x)
+            .collect();
+    };
+
+    let got = matasano::crack_aes_128_ctr_random_access(&ciphertext[..], edit);
+    assert_eq!(&got[..], &plaintext[..]);
+}