kernel-pwn学习(1)--环境搭建

• gdb
• pwndbg
• qemu
• 虚拟机配置
• Ropper
• extract-vmlinux
• un-cpio
• gen-cpio
• 常见的kernel-exploit例子

这个系统自带就不说了

我个人比较喜欢用pwndbg,下面配置一下
首先需要安装一下git

sudo apt install git

然后git获取

git clone https://github.com/pwndbg/pwndbg
cd pwndbg
sudo ./setup.sh

这里由于他放到了root目录下，我们再cp一份到/home/用户下

cp /root/.gdbinit /home/zhou/.gdbinit

sudo apt install qemu-kvm

对于vmware来说，需要修改一下虚拟机设置

勾选上虚拟化InterlVT这一个，如下图，不然之后会报错

Could Not Access KVM kernel module: No Such file or directory. qemu-system-x86_64: Failed to Initialize KVM: No such file or directory.

这个用来从vmlinux里面寻找gadget,比ROPgadget更快

pip3 install ropper

下面添加一下path

vim ~/.bashrc

再最下面加上对应的路径

PATH=$PATH:/home/zhou/.local/bin

然后

source   ~/.bashrc

源代码位于github
extract-vmlinux

vim extract-vmlinux

把github里面的内容复制进来，也就是下面的内容

#!/bin/sh
# SPDX-License-Identifier: GPL-2.0-only
# ----------------------------------------------------------------------
# extract-vmlinux - Extract uncompressed vmlinux from a kernel image
#
# Inspired from extract-ikconfig
# (c) 2009,2010 Dick Streefland 
#
# (c) 2011      Corentin Chary 
#
# ----------------------------------------------------------------------

check_vmlinux()
{
	# Use readelf to check if it's a valid ELF
	# TODO: find a better to way to check that it's really vmlinux
	#       and not just an elf
	readelf -h $1 > /dev/null 2>&1 || return 1

	cat $1
	exit 0
}

try_decompress()
{
	# The obscure use of the "tr" filter is to work around older versions of
	# "grep" that report the byte offset of the line instead of the pattern.

	# Try to find the header ($1) and decompress from here
	for	pos in `tr "$1n$2" "n$2=" < "$img" | grep -abo "^$2"`
	do
		pos=${pos%%:*}
		tail -c+$pos "$img" | $3 > $tmp 2> /dev/null
		check_vmlinux $tmp
	done
}

# Check invocation:
me=${0##*/}
img=$1
if	[ $# -ne 1 -o ! -s "$img" ]
then
	echo "Usage: $me " >&2
	exit 2
fi

# Prepare temp files:
tmp=$(mktemp /tmp/vmlinux-XXX)
trap "rm -f $tmp" 0

# That didn't work, so retry after decompression.
try_decompress '3721310' xy    gunzip
try_decompress '3757zXZ00' abcde unxz
try_decompress 'BZh'          xy    bunzip2
try_decompress '135'   xxx   unlzma
try_decompress '211114132' xy    'lzop -d'
try_decompress '02!L30'   xxx   'lz4 -d'
try_decompress '(265/375'   xxx   unzstd

# Finally check for uncompressed images or objects:
check_vmlinux $img

# Bail out:
echo "$me: Cannot find vmlinux." >&2

保存之后

chmod +x extract-vmlinux && sudo mv extract-vmlinux /usr/bin/

下面是为了方便新人写了一个小小的解压脚本

vim un-cpio

#!/bin/bash
me=${0##*/}
if	[ $# -ne 1  ]
then
	echo "Usage: $me " >&2
	echo "Notice: please use this script in a empty dir where the file system will be decompressed" >&2
	exit 2
fi
wholepath="`pwd`/$1"
path=$(dirname $wholepath)
file=$(basename $wholepath)
cd $path
mv $file "${file}.gz"
gunzip "${file}.gz"
cpio -idm < $file
rm $file

保持

chmod +x un-cpio
sudo mv un-cpio /usr/bin/

一般做题首先有个压缩包

由于驱动在文件系统里我们需要解压cpio

首先创建一个空目录

解压完成，当修改好之后我们可以用下面的工具进行打包

下面是为了方便新人写了一个小小的压缩为镜像文件的脚本

vim gen-cpio

#!/bin/bash
me=${0##*/}
if	[ $# -ne 1  ]
then
	echo "Usage: $me " >&2
	exit 2
fi

find . -print0 |cpio --null -o --format=newc |gzip -9 > $1

保存之后我们

chmod +x gen-cpio
sudo mv gen-cpio /usr/bin/

用法就是
进入到我们需要打包的文件系统目录，一般是题目给的我们解压之后的目录

参数就是我们想要的目标cpio的名字

然后我们把这个cpio文件放到boots.sh同目录，这个时候文件系统就是我们最新的状态，一般exp就是要通过这种方式打包进qemu

buuctf里面很少有kernel的题，所以只能自己去git上找
这里我分享两个
ctf wiki
上面这个是ctf wiki里面讲解的题目，里面有kernel模块的例题
一共有3道

w0lfzhang/kernel_exploit
这个下面的题目就很多了