X-Git-Url: http://git.euphorik.ch/?p=crypto_lab1.git;a=blobdiff_plain;f=lab1_rust%2Fsrc%2Foracle_machine.rs;h=3d72ddf4375e0c8b74363e19df4bc0a693765df7;hp=2feb31b4f1c3f98b532763273073e8d6dd5b4237;hb=d3d8743586e533af4f32c1edfcff6377161d7cf4;hpb=ed4d8f3e7e028bf645089edb775af84e6c3f7bd4

diff --git a/lab1_rust/src/oracle_machine.rs b/lab1_rust/src/oracle_machine.rs
index 2feb31b..3d72ddf 100644
--- a/lab1_rust/src/oracle_machine.rs
+++ b/lab1_rust/src/oracle_machine.rs
@@ -1,14 +1,14 @@
 use std::io;
-use std::io::{ TcpStream };
-use std::iter::{ range_inclusive };
+use std::io::TcpStream;
+use std::iter::range_inclusive;
 use std::slice::bytes::copy_memory;
 use packet;
 use packet::{ Packet, Error };
 use end_point::EndPoint;
 
-/// Try to decypher a cyphered data block by using the previous xor operand and an oracle on the provided address and port.
-/// May prints some message on the stdout.
-pub fn decypher(address: &str, port: u16, original_xor_operand: &[u8, ..16], cypherblock: &[u8, ..16], variant: packet::Variant) -> Option<Vec<u8>> {
+/// Try to decipher a ciphered data block by using the previous XOR operand and an oracle on the provided address and port.
+/// May print some message on stdout.
+pub fn decipher(address: &str, port: u16, original_xor_operand: &[u8, ..16], cipherblock: &[u8, ..16], variant: packet::Variant) -> Option<Vec<u8>> {
    let mut end_point = EndPoint::new(
       match TcpStream::connect(address, port) {
          Ok(s) => s,
@@ -20,12 +20,13 @@ pub fn decypher(address: &str, port: u16, original_xor_operand: &[u8, ..16], cyp
       variant,
    );
 
+   // See 'packet::Packet' documentation for a complete description about the binary packet structure.
    let mut final_packet = [0u8, ..2 + 1 + 8 + 32 + 10];
-   final_packet[1] = 1 + 8 + 32 + 10; // Data length.
-   copy_memory(final_packet.slice_mut(2 + 1 + 8 + 16, 2 + 1 + 8 + 32), cypherblock);
+   final_packet[1] = (final_packet.len() as u8) - 2; // Data length.
+   copy_memory(final_packet.slice_mut(2 + 1 + 8 + 16, 2 + 1 + 8 + 32), cipherblock);
 
-   let mut decypher_block = [0u8, ..16]; // The result.
-   let mut x_prime_block = [0u8, ..16]; // The cypher block ('cypherblock') after AES and before XOR.
+   let mut decipher_block = [0u8, ..16]; // The result.
+   let mut x_prime_block = [0u8, ..16]; // The cipher block ('cipherblock') after AES and before XOR.
    let mut current_timestamp = 0u64;
    let mut first_byte = 0u8; // Used to save the first byte for the first iteration.
 
@@ -49,7 +50,8 @@ pub fn decypher(address: &str, port: u16, original_xor_operand: &[u8, ..16], cyp
          forged_xor_operand(&mut final_packet)[byte] = v;
 
          match end_point.send_raw_with_result(final_packet) {
-            Ok(Ok(Packet { t: Error(packet::AuthError), .. })) => {
+            Ok(Ok(p @ Packet { t: Error(packet::AuthError), .. })) => {
+               println!("We received a MAC Error: {}", p);
 
                // If we already got a MAC mismatch for the first byte then the second byte is incremented and the loop is replayed.
                if byte == 15 && get_mac_mismatch_error {
@@ -61,14 +63,15 @@ pub fn decypher(address: &str, port: u16, original_xor_operand: &[u8, ..16], cyp
 
                let padding_value = 16 - byte;
                x_prime_block[byte] = v ^ (padding_value as u8);
-               decypher_block[byte] = x_prime_block[byte] ^ original_xor_operand[byte];
+               decipher_block[byte] = x_prime_block[byte] ^ original_xor_operand[byte];
 
-               // We set the processed bytes of the forged XOR operand to have the next padding value.
+               // We set the processed bytes of the forged XOR operand to have the next padding value (2, 3, 4, etc..).
                for i in range(16 - padding_value, 16) {
                   forged_xor_operand(&mut final_packet)[i] = x_prime_block[i] ^ ((padding_value as u8) + 1);
                }
 
-               // Special case for the first byte: we have to test all the values.
+               // Special case for the first byte: we have to test all the values to avoid a valid padding
+               // which is not [.., 0x01], for instance [.., 0x02, 0x02]. It's a very rare case but not impossible.
                if byte == 15 {
                   first_byte = forged_xor_operand(&mut final_packet)[15];
                } else {
@@ -93,5 +96,5 @@ pub fn decypher(address: &str, port: u16, original_xor_operand: &[u8, ..16], cyp
       byte -= 1;
    }
 
-   Some(decypher_block.to_vec())
+   Some(decipher_block.to_vec())
 }
\ No newline at end of file