feat: Initial padding oracle working. Pending check for special case.

The initial padding oracle attack is working. More tests need to be
added and there needs to be a check for the special case of the 02 01,
02 02 padding case

src/tasks/tasks01/pad_oracle.rs

@@ -0,0 +1,136 @@
+use anyhow::Result;
+use base64::prelude::*;
+use serde_json::Value;
+use std::io::prelude::*;
+use std::net::TcpStream;
+use std::time::Duration;
+use std::{thread, usize};
+
+pub fn padding_oracle(args: &Value) -> Result<Vec<u8>> {
+    let hostname: String = serde_json::from_value(args["hostname"].clone())?;
+
+    let port_val: Value = serde_json::from_value(args["port"].clone())?;
+    let port: u64 = port_val.as_u64().expect("Failure in parsing port number");
+
+    let iv_string: String = serde_json::from_value(args["iv"].clone())?;
+    let iv: Vec<u8> = BASE64_STANDARD.decode(iv_string)?;
+
+    let cipher_text: String = serde_json::from_value(args["ciphertext"].clone())?;
+    let ciphertext: Vec<u8> = BASE64_STANDARD.decode(cipher_text)?;
+
+    // Initialise tracker to adapt correct byte
+    let byte_counter = 15;
+    eprintln!("byte_counter is: {}", byte_counter);
+
+    let mut plaintext: Vec<u8> = vec![];
+    eprintln!("Ciphertext: {:002X?}", ciphertext);
+
+    let cipher_chunks: Vec<&[u8]> = ciphertext.chunks(16).rev().collect();
+    let mut chunk_counter = 0;
+
+    for chunk in &cipher_chunks {
+        let mut stream = TcpStream::connect(format!("{}:{}", hostname, port))?;
+        stream.set_nonblocking(false)?;
+
+        // Track value sent to server
+        let mut attack_counter: Vec<u8> = vec![0; 16];
+
+        // Amount of q blocks to send to server.
+        // TODO:: May be increased via function
+        let q_block_count: u16 = 255;
+
+        //Send the first ciphertext chunk
+        eprintln!("Sending Ciphertext chunk: {:002X?}", chunk);
+        stream.flush()?;
+        stream.write_all(&chunk)?;
+        stream.flush()?;
+
+        for i in (0..=15).rev() {
+            // Craft length message
+            // FIXME: Assignment is redundant for now
+            // TODO: Goal is to maybe add speed increase in the future
+            let l_msg: [u8; 2] = q_block_count.to_le_bytes();
+            //eprintln!("Sending l_msg: {:02X?}", l_msg);
+            stream.write_all(&l_msg)?;
+            stream.flush()?;
+            //eprintln!("L_msg sent");
+
+            // Generate attack blocks
+            for j in 0..q_block_count {
+                // Next byte
+                //eprintln!("Sending attack block: {:02X?}", attack_counter);
+
+                //thread::sleep(Duration::from_millis(1000));
+                stream.write_all(&attack_counter)?;
+                stream.flush()?;
+                attack_counter[i as usize] += 1;
+            }
+
+            // Read server response
+            let mut buf = [0u8; 0xFF];
+            stream.read_exact(&mut buf)?;
+            //eprintln!("{:02X?}", buf);
+
+            // extract valid position
+            let valid_val = buf.iter().position(|&r| r == 0x01).expect("No valid found") as u8;
+            //eprintln!("Valid value found: {:02X?}", valid_val);
+
+            // Craft next attack vector padding; 0x01, 0x02, ...
+            attack_counter[i as usize] = valid_val;
+
+            if chunk_counter + 1 < cipher_chunks.len() {
+                eprintln!("XOR Next Ciph block");
+                plaintext.push(
+                    cipher_chunks[chunk_counter + 1][i]
+                        ^ (attack_counter[i as usize] ^ (15 - i as u8 + 1)),
+                );
+            } else {
+                eprintln!("XOR IV");
+
+                plaintext.push(iv[i] ^ (attack_counter[i as usize] ^ (15 - i as u8 + 1)));
+            }
+            //eprintln!("Attack counter after set: {:02X?}", attack_counter);
+            for pos in i..=15 {
+                //eprintln!("i is: {:02X?}", i);
+                //eprintln!("i + 1 is: {:02X?}", ((16 - i) as u8).to_le());
+                /*
+                eprintln!(
+                    "attack_counter[pos as usize]: {:02X?}",
+                    attack_counter[pos as usize]
+                );
+                eprintln!(
+                    "attack_counter[pos as usize] ^ 0x02 {:02X?}",
+                    attack_counter[pos as usize] ^ (15 - i as u8 + 1)
+                );
+                */
+                let intermediate = attack_counter[pos as usize] ^ (15 - i as u8 + 1);
+
+                attack_counter[pos as usize] = intermediate ^ ((15 - i as u8 + 1) + 1);
+            }
+            stream.flush()?;
+
+            // Write plaintext
+            //eprintln!("{:02X?}", plaintext);
+        }
+        chunk_counter += 1;
+        stream.flush()?;
+        // break;
+        drop(stream);
+    }
+
+    plaintext.reverse();
+
+    eprintln!("{:02X?}", BASE64_STANDARD.encode(&plaintext));
+    Ok(plaintext)
+} // the stream is closed here
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use serde_json::json;
+
+    #[test]
+    fn test_connection() -> Result<()> {
+        Ok(())
+    }
+}