unixtract/src/formats/mtk_pkg_old.rs

use std::any::Any;
use crate::{InputTarget, AppContext, formats::Format};
pub fn format() -> Format {
    Format { name: "mtk_pkg_old", detector_func: is_mtk_pkg_old_file, extractor_func: extract_mtk_pkg_old }
}

use std::path::Path;
use std::fs::{self, OpenOptions};
use std::io::{Write, Cursor, Seek};
use binrw::{BinRead, BinReaderExt};

use crate::utils::common;
use crate::utils::mtk_crypto::{decrypt};
use crate::utils::lzhs::{decompress_lzhs_fs_file2file_old};

static KEY: u32 = 0x94102909; //09 29 10 94
// first 4 bytes of header and content are additionally XORed, they have different masks although only differ by half a byte
static HEADER_XOR_MASK: u32 = 0x04BE7C75; //75 7C BE 04
static CONTENT_XOR_MASK: u32 = 0x04BE7C72; //72 7C BE 04

use crate::formats::mtk_pkg::{MTK_HEADER_MAGIC, MTK_META_MAGIC, MTK_META_PAD_MAGIC};

#[derive(BinRead)]
struct Header {
    #[br(count = 4)] vendor_magic_bytes: Vec<u8>,
    #[br(count = 8)] _mtk_magic: Vec<u8>, //#DH@FiRm
	#[br(count = 68)] version_bytes: Vec<u8>,
	file_size: u32,
    _flags: u32,
    #[br(count = 32)] product_name_bytes: Vec<u8>,
    #[br(count = 32)] _digest: Vec<u8>,
}
impl Header {
    fn vendor_magic(&self) -> String {
        common::string_from_bytes(&self.vendor_magic_bytes)
    }
    fn version(&self) -> String {
        common::string_from_bytes(&self.version_bytes)
    }
    fn product_name(&self) -> String {
        common::string_from_bytes(&self.product_name_bytes)
    }

}

#[derive(BinRead)]
struct PartEntry {
    #[br(count = 4)] name_bytes: Vec<u8>,
	flags: u32,
    size: u32,
}
impl PartEntry {
    fn name(&self) -> String {
        common::string_from_bytes(&self.name_bytes)
    }
    fn is_encrypted(&self) -> bool {
        (self.flags & 1 << 0) == 1 << 0
    }
    fn is_compressed(&self) -> bool { //lzhs fs
        (self.flags & 1 << 8) != 0
    }
}

static HEADER_SIZE: usize = 0x98;

pub fn is_mtk_pkg_old_file(app_ctx: &AppContext) -> Result<Option<Box<dyn Any>>, Box<dyn std::error::Error>> {
    let mut file = match &app_ctx.input {InputTarget::File(f) => f, InputTarget::Directory(_) => return Ok(None)};

    let encrypted_header = common::read_file(&file, 0, HEADER_SIZE)?;
    let header = decrypt(&encrypted_header, KEY, Some(HEADER_XOR_MASK));
    if &header[4..12] == MTK_HEADER_MAGIC {
        Ok(Some(Box::new(())))
    } else if &header[68..76] == MTK_HEADER_MAGIC {
        //check for 64 byte additional header used in some Sony and Philips firmwares and skip it
        file.seek(std::io::SeekFrom::Start(64))?;
        Ok(Some(Box::new(())))
    } else if &header[132..140] == MTK_HEADER_MAGIC {
        //check for 128 byte additional header used in some Philips firmwares and skip it
        file.seek(std::io::SeekFrom::Start(128))?;
        Ok(Some(Box::new(())))
    } else {
        Ok(None)
    }
}

pub fn extract_mtk_pkg_old(app_ctx: &AppContext, _ctx: Option<Box<dyn Any>>) -> Result<(), Box<dyn std::error::Error>> {
    let mut file = match &app_ctx.input {InputTarget::File(f) => f, InputTarget::Directory(_) => return Err("Extractor expected file, not directory".into())};

    let file_size = file.metadata()?.len();
    let encrypted_header = common::read_exact(&mut file, HEADER_SIZE)?;
    let header = decrypt(&encrypted_header, KEY, Some(HEADER_XOR_MASK));
    let mut hdr_reader = Cursor::new(header); 
    let hdr: Header = hdr_reader.read_le()?;

    println!("File info:\nFile size: {}\nVendor magic: {}\nVersion info: {}\nProduct name: {}" , 
            hdr.file_size, hdr.vendor_magic(), hdr.version(), hdr.product_name());

    let mut part_n = 0;
    while file.stream_position()? < file_size as u64 {
        part_n += 1;
        let part_entry: PartEntry = file.read_le()?;

        println!("\n#{} - {}, Size: {}{} {}", 
                part_n, part_entry.name(), part_entry.size, if part_entry.is_compressed() {" [COMPRESSED]"} else {""}, if part_entry.is_encrypted() {"[ENCRYPTED]"} else {""} );

        let data = common::read_exact(&mut file, part_entry.size as usize)?;
        let out_data; 
        if part_entry.is_encrypted() {
            //decrypt with the vendor magic
            println!("- Decrypting...");
            let vendor_magic_u32 = u32::from_le_bytes(hdr.vendor_magic_bytes.clone().try_into().unwrap());
            out_data = decrypt(&data, vendor_magic_u32, Some(CONTENT_XOR_MASK));
        } else {
            out_data = data;
        }

        //strip iMtK thing and get version
        let extra_header_len = if &out_data[0..4] == MTK_META_MAGIC {
            let imtk_len = u32::from_le_bytes(out_data[4..8].try_into().unwrap());
            if &out_data[8..12] != MTK_META_PAD_MAGIC {
                let version_len = u32::from_le_bytes(out_data[8..12].try_into().unwrap());
                let version = common::string_from_bytes(&out_data[12..12 + version_len as usize]);
                println!("- Version: {}", version);
            }
            imtk_len + 8
        } else {
            0
        };

        //for compressed part create temp file
        let output_path = Path::new(&app_ctx.output_dir).join(part_entry.name() + if part_entry.is_compressed() {".lzhs"} else {".bin"});
        fs::create_dir_all(&app_ctx.output_dir)?;
        let mut out_file = OpenOptions::new().write(true).read(true)/* for lzhs */.create(true).open(&output_path)?;
        out_file.write_all(&out_data[extra_header_len as usize..])?;

        if part_entry.is_compressed() {
            let lzhs_out_path = Path::new(&app_ctx.output_dir).join(part_entry.name() + ".bin");
            match decompress_lzhs_fs_file2file_old(&out_file, lzhs_out_path) {
                Ok(()) => {
                    println!("- Decompressed Successfully!");
                    //after successfull decompression remove the temporary .lzhs file
                    fs::remove_file(&output_path)?;
                },
                Err(e) => {
                    eprintln!("Failed to decompress partition!, Error: {}. Saving compressed data...", e);
                    //if the decompression is not successfull leave out compressed data.
                }
            }   
        }

        println!("-- Saved file!");
    }

    println!("\nExtraction finished!");

    Ok(())
}