1 unstable release
Uses old Rust 2015
0.1.4 | Mar 18, 2018 |
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#2720 in Parser implementations
97KB
2.5K
SLoC
JBcRs-basic
JBcRs is a Library, written in rust, to support reading and writing of java class files.
This library is not close from being finished, but certain features have already been implemented:
- Basic parsing:
A class file is parsed rather primitive:
- You have access to the constant pool.
Names, Descriptors and more are represented as
u16
, Indexing into the pool must be done manually. No validation of indices when parsing will be done. - Access Flags are decoded using the bitflags crate to provide a better experience.
- Attributes are always parsed. This might be changed since it allows attackers to craft invalid Debug Attributes, which don't play a serious role in executing the code, Parsing the entire class file then might not work, since an error will be returned.
- You have access to the constant pool.
Names, Descriptors and more are represented as
- Basic writing: A class file is written as it was parsed.
Getting Started:
First, add this library as a dependency to your Cargo.toml
[dependencies]
jbcrs_basic = "0.1.4"
We want to parse a class from a byte array and print its version, access flags and name. Of course you could use std::fs::File or a zip library, but showing this is not the purpose of this tutorial.
extern crate jbcrs_basic;
use jbcrs_basic::*;
// You got the bytes from any possible source.
let bytes: &[u8] = [0xCA, 0xFE, 0xBA, 0xBE];
// After parsing the class file,
// you will get the constant pool
// and the class itself.
// You don't have to annotate the types here.
let (constant_pool, class): (Pool, Class) = parse(bytes)
.expect("could not parse class file");
// Print its major and minor version:
println!("version: {}.{}", class.major_version, class.minor_version);
// Access Flags can be printed human readable
println!("access: {:?}", class.access_flags);
// Printing the name requires us to use the constant pool.
println!("name: {}", constant_pool.get_class_name(class.name).expect("could not get class name"));
Resources
Dependencies
~2MB
~45K SLoC