DEXrs

DEXrs is a Rust library and CLI tool for parsing, inspecting, and modifying Android DEX files. It covers a zero-copy parser, a Dalvik disassembler, a full-featured terminal UI, a DEX modification API, and Python bindings via PyO3.

What this project covers

• Zero-copy, lazy DEX file parser (fuzzing-hardened)
• Dalvik bytecode disassembler
• dexrs CLI — 12 subcommands for inspection and modification
• Interactive TUI (dexrs inspect) via ratatui/crossterm
• DEX modification API — in-place patching and structural editing
• Python extension via PyO3 (parser + editor)
• Benchmarks (WIP)
• Smali disassembler / decompiler

Installation

# CLI binary
cargo install --git https://github.com/MatrixEditor/dexrs dexrs
# with TUI
cargo install --git https://github.com/MatrixEditor/dexrs -F tui dexrs

# Python package
pip install -v git+https://github.com/MatrixEditor/dexrs@dev/v2-rewrite

CLI — dexrs

dexrs [--no-color] [--no-verify] [--json] <COMMAND> <FILE> [OPTIONS]

Inspection

Command	Description
info	File header, integrity hashes, section counts
map	Map list — all section types and their offsets
classes	All class definitions with access flags
class --class <NAME>	Single class (fields + methods)
methods	All methods across all classes
fields	All fields across all classes
disasm --class <C> --method <M>	Disassemble one method
strings	Full string pool
types	All type descriptors
inspect	Interactive TUI (see below)

dexrs info    classes.dex
dexrs classes classes.dex --no-color
dexrs class   classes.dex --class LMain;
dexrs disasm  classes.dex --class LMain; --method main --json

Modification

patch — in-place (overwrites source file)

# Set class access flags
dexrs patch flags <FILE> --class <CLASS> --flags <HEX>

# Overwrite a single instruction word
dexrs patch insn <FILE> --offset <HEX_OFFSET> --pc <CODE_UNIT> --word <HEX>

dexrs patch flags classes.dex --class LMain; --flags 0x11   # public final

edit — structural (writes to --output)

dexrs edit rename-class    <FILE> <OLD> <NEW>            --output <OUT>
dexrs edit set-flags       <FILE> --class <C> --flags <F> --output <OUT>
dexrs edit set-method-flags <FILE> --class <C> --method <M> --flags <F> --output <OUT>
dexrs edit clear-hiddenapi <FILE>                        --output <OUT>

dexrs edit rename-class classes.dex LMain; LRenamedMain; --output out.dex
dexrs edit set-flags    classes.dex --class LMain; --flags 0x21 --output out.dex

Rust API

Parsing

use dexrs::file::{verifier::VerifyPreset, DexFile, DexFileContainer, DexLocation};

// From a file with verification
let file = std::fs::File::open("classes.dex")?;
let dex = DexFileContainer::new(&file)
    .verify(true)
    .verify_checksum(true)
    .open()?;

// From memory
let dex = DexFile::open(data, DexLocation::InMemory, VerifyPreset::None)?;

See examples/parse_dex_file.rs and examples/dex_basic_ops.rs for full usage.

DEX modification — DexEditor

DexEditor owns the DEX bytes and exposes named mutations. Finalise with build() -> Vec<u8> or write_to(path) — both recalculate the Adler32 checksum.

use std::path::Path;
use dexrs::file::DexEditor;

let mut editor = DexEditor::from_file(Path::new("classes.dex"))?;
// or: DexEditor::from_bytes(bytes)?

// Accepts dotted ("com.example.Foo"), slash, or descriptor ("Lcom/example/Foo;") form
editor.set_class_access_flags("LMain;", 0x0011 /* public final */)?;
editor.rename_class("LMain;", "LRenamedMain;")?;
editor.set_method_access_flags("LMain;", "main", 0x0009 /* public static */)?;
editor.clear_hiddenapi_flags().ok(); // no-op if section absent

// Finalise
let bytes: Vec<u8> = editor.build()?;
// or:
editor.write_to(Path::new("out.dex"))?;

Low-level checksum

use dexrs::file::patch::update_checksum;

let mut raw = std::fs::read("classes.dex")?;
// ... raw byte mutations ...
update_checksum(&mut raw);  // recalculate Adler32 in-place

See examples/dex_edit.rs for a complete runnable example.

Python API

Parsing

from dexrs import DexFile, VerifyPreset, FileDexContainer

container = FileDexContainer("classes.dex")
dex = DexFile.from_container(container, verify=VerifyPreset.All)

for cls in dex.get_class_defs():
    print(cls)

DEX modification — DexEditor

from dexrs import DexEditor

editor = DexEditor.from_file("classes.dex")
# or: DexEditor.from_bytes(open("classes.dex","rb").read())

editor.set_class_access_flags("LMain;", 0x0001)          # public
editor.rename_class("LMain;", "LRenamedMain;")           # rebuild string pool
editor.set_method_access_flags("LMain;", "main", 0x0009) # public static
editor.clear_hiddenapi_flags()                           # strip hidden-API metadata

# Get bytes
data = editor.build()
open("out.dex", "wb").write(data)

# Or write directly (editor is consumed)
editor.write_to("out.dex")

Common access flag values

Value	Meaning
0x0001	public
0x0002	private
0x0004	protected
0x0008	static
0x0010	final
0x0100	native
0x0400	abstract
0x1000	synthetic

License

This project is licensed under the MIT license.