# Smali Crate

A pure rust implementation of a parser, writer and set of types for the smali file format.

Smali is used in the Android reversing community to examine and modify Android APK files. It's a human readable text format that represents the complete structure of a Dex VM class including all of its instructions. 

With this crate you can use it in conjunction with [apktool](https://ibotpeaches.github.io/Apktool/) to perform analysis and/or patches to Android applications. 

There is a simple example in examples/main.rs that illustrates this. The example, will invoke apktool to expand any application and then parse all the smali files looking for [RootBeer](https://github.com/scottyab/rootbeer) (an open source root detection framework), it will then patch RootBeer's methods to always return false so that the app can be run on a rooted device.
Finally, it calls apktool again to repackage the app.

Here's the simple example :-

```rust
/* Expand the APK and patch RootBeer */
fn process_apk(apk_file: &str) -> Result<(), Box<dyn Error>>
{
   // Call apktool to unpack the APK
   execute_command("apktool", &["decode", "-f", apk_file, "-o", "out"])?;

   // Load all the smali classes
   let mut p = PathBuf::from_str("out")?;
   p.push("smali");
   let mut classes = find_smali_files(&p)?;
   println!("{:} smali classes loaded.", classes.len());

   // Search for the RootBeer class
   for c in classes.iter_mut()
   {
       if is_rootbeer_class(&c)
       {
           // Patch all the methods returning a boolean
           for m in c.methods.iter_mut()
           {
               if m.signature.return_type == TypeSignature::Bool && m.signature.args.len() == 0
               {
                   let mut new_instructions = vec![];
                   new_instructions.push(Instruction("const/4 v0, 0x0".to_string())); // Set v0 to false
                   new_instructions.push(Instruction("return v0".to_string()));       // return v0
                   m.instructions = new_instructions;
                   m.locals = 1;
                   println!("{} method {} successfully patched.", c.name.as_java_type(), &m.name);
               }
           }
       }
       // Save all classes, even unmodified so we can thoroughly test parser and writer
       c.save()?;
   }

   // Repack the APK
   execute_command("apktool", &["build", "out", "-o", "out.apk"])?;

   Ok(())
}
```