Mastering Linux Debugging with GNU Debugger (GDB)

 

 

GNU debugger (gdb) is a debugger program used on the Linux system, usually used to debug applications or programs on the Linux system. Here what we use is pwndbg this pwndbg function makes it easier for us to use functions in the debugger.

For the installation tutorial, you can uninstall the default gdb default linux first, so that it can make it easier to configure pwngdb to the default gdb system.

 

Run the default gdb uninstall command:

$ sudo apt-get remove --purge gdb
$ sudo rm -rf /usr/share/gdb

Next we will do a git clone and install the pwndbg:

$ sudo su
$ cd # agar menuju directory root
$ git clone https://github.com/pwndbg/pwndbg
$ cd pwndbg

Before installing we will change the setup.sh script, you can copy the script that I have changed as below:

#!/bin/bash
set -ex

# If we are a root in a Docker container and `sudo` doesn't exist
# lets overwrite it with a function that just executes things passed to sudo
# (yeah it won't work for sudo executed with flags)
if [ -f /.dockerenv ] && ! hash sudo 2>/dev/null && whoami | grep root; then
    sudo() {
        ${*}
    }
fi

# Helper functions
linux() {
    uname | grep -i Linux &>/dev/null
}
osx() {
    uname | grep -i Darwin &>/dev/null
}

install_apt() {
    sudo apt-get update || true
    sudo apt-get install -y git gdb python3-dev python3-pip python3-setuptools libglib2.0-dev libc6-dbg

    if uname -m | grep x86_64 > /dev/null; then
        sudo dpkg --add-architecture i386 || true
        sudo apt-get update || true
        sudo apt-get install -y libc6-dbg:i386 || true
    fi
}

install_dnf() {
    sudo dnf update || true
    sudo dnf -y install gdb gdb-gdbserver python-devel python3-devel python-pip python3-pip glib2-devel make
    sudo dnf -y debuginfo-install glibc
}

install_xbps() {
    sudo xbps-install -Su
    sudo xbps-install -Sy gdb gcc python-devel python3-devel python-pip python3-pip glibc-devel make
    sudo xbps-install -Sy glibc-dbg
}

install_swupd() {
    sudo swupd update || true
    sudo swupd bundle-add gdb python3-basic make c-basic
}

install_zypper() {
    sudo zypper refresh || true
    sudo zypper install -y gdb gdbserver python-devel python3-devel python2-pip python3-pip glib2-devel make glibc-debuginfo

    if uname -m | grep x86_64 > /dev/null; then
        sudo zypper install -y glibc-32bit-debuginfo || true
    fi
}

install_emerge() {
    emerge --oneshot --deep --newuse --changed-use --changed-deps dev-lang/python dev-python/pip sys-devel/gdb
}

PYTHON=''
INSTALLFLAGS=''

if osx || [ "$1" == "--user" ]; then
    INSTALLFLAGS="--user"
else
    PYTHON="sudo "
fi

if linux; then
    distro=$(grep "^ID=" /etc/os-release | cut -d'=' -f2 | sed -e 's/"//g')

    case $distro in
        "ubuntu")
            install_apt
            ;;
        "fedora")
            install_dnf
            ;;
        "clear-linux-os")
            install_swupd
            ;;
        "opensuse-leap")
            install_zypper
            ;;
        "arch")
            echo "Install Arch linux using a community package. See:"
            echo " - https://www.archlinux.org/packages/community/any/pwndbg/"
            echo " - https://aur.archlinux.org/packages/pwndbg-git/"
            exit 1
            ;;
        "manjaro")
            echo "Pwndbg is not avaiable on Manjaro's repositories."
            echo "But it can be installed using Arch's AUR community package. See:"
            echo " - https://www.archlinux.org/packages/community/any/pwndbg/"
            echo " - https://aur.archlinux.org/packages/pwndbg-git/"
            exit 1
            ;;
        "void")
            install_xbps
            ;;
        "gentoo")
            install_emerge
            if ! hash sudo 2>/dev/null && whoami | grep root; then
                sudo() {
                    ${*}
                }
            fi
            ;;
        *) # we can add more install command for each distros.
            echo "\"$distro\" is not supported distro. Will search for 'apt' or 'dnf' package managers."
            if hash apt; then
                install_apt
            elif hash dnf; then
                install_dnf
            else
                echo "\"$distro\" is not supported and your distro don't have apt or dnf that we support currently."
                exit
            fi
            ;;
    esac
fi

if ! hash gdb; then
    echo "Could not find gdb in $PATH"
    exit
fi

# Update all submodules
git submodule update --init --recursive

# Find the Python version used by GDB.
PYVER=$(gdb -batch -q --nx -ex 'pi import platform; print(".".join(platform.python_version_tuple()[:2]))')
PYTHON+=$(gdb -batch -q --nx -ex 'pi import sys; print(sys.executable)')
PYTHON+="${PYVER}"

# Find the Python site-packages that we need to use so that
# GDB can find the files once we've installed them.
if linux && [ -z "$INSTALLFLAGS" ]; then
    SITE_PACKAGES=$(gdb -batch -q --nx -ex 'pi import site; print(site.getsitepackages()[0])')
    INSTALLFLAGS="${SITE_PACKAGES}"
fi

# Make sure that pip is available
if ! ${PYTHON} -m pip -V; then
    ${PYTHON} -m ensurepip --target "${INSTALLFLAGS}" --upgrade
fi

# Upgrade pip itself
${PYTHON} -m pip install --target "${INSTALLFLAGS}" --upgrade pip

# Install Python dependencies
${PYTHON} -m pip install --target "${INSTALLFLAGS}" -Ur requirements.txt

# Load Pwndbg into GDB on every launch.
if ! grep pwndbg ~/.gdbinit &>/dev/null; then
    echo "source $PWD/gdbinit.py" >> ~/.gdbinit
fi

Then save and now we run it with the command:

./setup.sh

After the install process is complete we will create a separate file in the /usr/bin directory, use the script below and save it with the name pwngdb:

#!/bin/sh
exec gdb -q -ex init-pwndbg "$@"

Continue by changing the permission to execute:

$ chmod +x /usr/bin/pwngdb

We will test with the pwngdb command in the terminal, if successful it will be as shown below.

Note: if you experience an error when running pwngdb as below, please replace the script in /root/pwndbg/pwndbg/command/context.py with the script  here.