david942j/gdb-ruby

It's time for Ruby lovers to use Ruby in gdb, and gdb in Ruby!

GDB-Ruby

It's time for Ruby lovers to use Ruby in gdb and gdb in Ruby!

Achieve two things in one gem:

1. Launching Ruby interactive shell (pry) in gdb.
2. gdb Ruby-binding, i.e. communicate with gdb in Ruby scripts.

Use Ruby in gdb

We provide a binary gdb-ruby (a Ruby script actually) with usage exactly the same as a normal gdb, while has two extra commands: ruby and pry!

See examples below:

$ gdb-ruby -q bash
Reading symbols from bash...(no debugging symbols found)...done.
(gdb) help ruby
Evaluate a Ruby command.
There's an instance 'gdb' for you. See examples.

Syntax: ruby <ruby code>

Examples:
    ruby p 'abcd'
    # "abcd"

Use gdb:
    ruby puts gdb.break('main')
    # Breakpoint 1 at 0x41eed0

Method defined will remain in context:
    ruby def a(b); b * b; end
    ruby p a(9)
    # 81
(gdb) help pry
Enter Ruby interactive shell.
Everything works like a charm!

Syntax: pry

Example:
    pry
    # [1] pry(#<GDB::EvalContext>)>

Integrate with other gdb extensions

Completely NO effort if you want to use gdb-ruby with other gdb extensions.

For example, I usually use the plugin gef with gdb. Everything works as usual when integrated with gdb-ruby:

Launching with $ gdb-ruby -q bash

Use gdb in Ruby

Communicate with gdb in your Ruby script.

Useful methods

Basic usage is use execute to do anything you want to execute inside gdb, while gdb-ruby provides some useful methods listed as following:

• break: Set break points. Alias: b
• run: Run. Alias: r
• register: Get value by register's name. Alias: reg
• text_base: Get current running program's text base, useful for a PIE binary.
• pid: Get the process id of running process.
• read_memory: Read process's memory, with friendly type casting. Alias: readm
• write_memory: Write process's memory, useful for dynamic analysis. Alias: writem
• interact: Back to normal gdb interactive mode.

All of these methods are fully documented at online doc, go for it!

Examples

Play with argv using gdb-ruby.

This script does:

1. Set a break point at main.
2. Get argv using register and read_memory.
3. Change argv using write_memory.

require 'gdb'

# launch a gdb instance
gdb = GDB::GDB.new('bash')

# 1. set breakpoint
gdb.break('main')
#=> "Breakpoint 1 at 0x41eed0"
gdb.run('-c "echo cat"')

# 2. get argv pointers
rdi = gdb.reg(:rdi)
#=> 3
rsi = gdb.reg(:rsi)
argv = gdb.readm(rsi, rdi, as: :u64)
argv.map { |c| '0x%x' % c }
#=> ['0x7fffffffe61b', '0x7fffffffe625', '0x7fffffffe628']

# 3. overwrite argv[2]'s 'cat' to 'FAT'
gdb.writem(argv[2] + 5, 'FAT') # echo FAT

puts gdb.execute('continue')
# Continuing.
# FAT
# [Inferior 1 (process 32217) exited normally]

Set a break point, run it, and back to gdb interactive mode.

require 'gdb'

# launch a gdb instance
gdb = GDB::GDB.new('bash')
# set breakpoints
gdb.break('main')
gdb.run
# to show the process do stop at the breakpoint
gdb.execute('info reg rip')
#=> "rip            0x41eed0\t0x41eed0 <main>"

# interaction like normal gdb!
gdb.interact

Installation

Available on RubyGems.org!

$ gem install gdb

Development

git clone https://github.com/david942j/gdb-ruby
cd gdb-ruby
bundle
bundle exec rake

Bugs & Feedback

Feel free to file an issue if you find any bugs. Any feature requests and suggestions are welcome! 😬

Growing up

gdb-ruby is under developing, give it a star and watch for latest updates!