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[原创]AFL-FUZZ学习:QEMU模式的使用(MIPS架构)
2022-8-16 14:29 9714

[原创]AFL-FUZZ学习:QEMU模式的使用(MIPS架构)

2022-8-16 14:29
9714

最近学习用AFL(American Fuzzy Lop)进行漏洞挖掘,简单的记录一下AFL的QEMU模式的使用。

首先创建测试用例:test.c

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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>
 
int vuln(char *str)
{
    int len = strlen(str);
    if(str[0] == 'A' && len == 66)
    {
        raise(SIGSEGV);
        //如果输入的字符串的首字符为A并且长度为66,则异常退出
    }
    else if(str[0] == 'F' && len == 6)
    {
        raise(SIGSEGV);
        //如果输入的字符串的首字符为F并且长度为6,则异常退出
    }
    else
    {
        printf("it is good!\n");
    }
    return 0;
}
 
int main(int argc, char *argv[])
{
    char buf[100]={0};
    gets(buf);//存在栈溢出漏洞
    printf(buf);//存在格式化字符串漏洞
    vuln(buf);
 
    return 0;
}

编译生成MIPS架构的可执行文件(需要建立MIPS交叉编译环境)

使用mips-linux-gcc编译test.c文件,

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mips-linux-gcc -g -o mips-test test.c

在这里插入图片描述

 

使用file命令查看文件类型

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ubuntu20-1@ubuntu:~/fuzzing$ file mips-test
mips-test: ELF 32-bit MSB executable, MIPS, MIPS32 version 1 (SYSV), dynamically linked, interpreter /lib/ld-uClibc.so.0, with debug_info, not stripped

在使用afl进行fuzz前,先用qemu的用户模式测试MIPS文件能否正常运行

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ubuntu20-1@ubuntu:~/fuzzing$ qemu-mips -L ./ mips-test
qemu-mips: Could not open '/lib/ld-uClibc.so.0': No such file or directory

-L 参数的作用:将elf解释器前缀设置为“path”,通常为lib文件夹的父目录

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-L path              QEMU_LD_PREFIX    set the elf interpreter prefix to 'path'

报错:qemu-mips: Could not open '/lib/ld-uClibc.so.0': No such file or directory,缺少lib文件

 

解决方法:在当前目录创建lib文件夹,使用locate命令进行查找,并将ld-uClibc.so.0文件复制进lib文件夹

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ubuntu20-1@ubuntu:~/fuzzing$ locate ld-uClibc.so.0
 
/home/ubuntu20-1/buildroot-mips/output/build/uclibc-1.0.39/lib/ld-uClibc.so.0
/home/ubuntu20-1/buildroot-mips/output/host/mips-buildroot-linux-uclibc/sysroot/lib/ld-uClibc.so.0
/home/ubuntu20-1/buildroot-mips/output/target/lib/ld-uClibc.so.0
 
ubuntu20-1@ubuntu:~/fuzzing$ mkdir lib
ubuntu20-1@ubuntu:~/fuzzing$ cp /home/ubuntu20-1/buildroot-mips/output/target/lib/ld-uClibc.so.0 ./lib
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#再次执行qemu-mips,仍然报错,解决方法同上
ubuntu20-1@ubuntu:~/fuzzing$ qemu-mips -L ./ mips-test
/home/ubuntu20-1/fuzzing/mips-test: can't load library 'libc.so.0'
 
ubuntu20-1@ubuntu:~/fuzzing$ locate libc.so.0
 
/home/ubuntu20-1/buildroot-mips/output/build/uclibc-1.0.39/lib/ld-uClibc.so.0
/home/ubuntu20-1/buildroot-mips/output/build/uclibc-1.0.39/lib/libc.so.0
/home/ubuntu20-1/buildroot-mips/output/host/mips-buildroot-linux-uclibc/sysroot/lib/ld-uClibc.so.0
/home/ubuntu20-1/buildroot-mips/output/host/mips-buildroot-linux-uclibc/sysroot/lib/libc.so.0
/home/ubuntu20-1/buildroot-mips/output/target/lib/ld-uClibc.so.0
/home/ubuntu20-1/buildroot-mips/output/target/lib/libc.so.0
 
ubuntu20-1@ubuntu:~/fuzzing$ cp /home/ubuntu20-1/buildroot-mips/output/host/mips-buildroot-linux-uclibc/sysroot/lib/libc.so.0 ./lib
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#再次执行qemu-mips
ubuntu20-1@ubuntu:~/fuzzing$ qemu-mips -L ./ mips-test
123
123it is good!
#正常输出,可用afl-fuzz进行测试

进行fuzz

创建afl-fuzz的输入文件夹,并构造测试用例

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mkdir afl-in
cd afl-in
echo abc > testcase
cd ..

使用afl-fuzz进行fuzz,因为没有使用afl-gcc进行插桩编译,需要加上-Q参数,即使用QEMU模式进行fuzz测试

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#初始化设置
 
#需要设置core_pattern,若未设置会出现报错1,详情见后文
sudo su
echo core >/proc/sys/kernel/core_pattern
exit
 
#设置AFL相关的环境变量
#AFL_PATH为afl的安装路径
#QEMU_LD_PREFIX 为 MIPS 的 lib/ 目录所在的目录,MIPS文件的根目录
export AFL_PATH=/home/ubuntu20-1/afl-2.52b
export QEMU_LD_PREFIX=.
#若未设置 -m none,会出现报错2,详情见后文
#若未设置export QEMU_LD_PREFIX=.,会出现报错3,详情见后文
afl-fuzz -i afl-in -o afl-out -m none -Q ./mips-test

参数解释:
-i afl-in:输入文件夹为afl-in
-o afl-out:输出文件夹为afl-out
-m none:不限制内存大小
-Q:使用afl的QEMU模式
./mips-test:被fuzz测试的文件

开始fuzz

在这里插入图片描述

报错1:

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[-] Hmm, your system is configured to send core dump notifications to an
    external utility. This will cause issues: there will be an extended delay
    between stumbling upon a crash and having this information relayed to the
    fuzzer via the standard waitpid() API.
 
    To avoid having crashes misinterpreted as timeouts, please log in as root
    and temporarily modify /proc/sys/kernel/core_pattern, like so:
 
    echo core >/proc/sys/kernel/core_pattern
 
[-] PROGRAM ABORT : Pipe at the beginning of 'core_pattern'
         Location : check_crash_handling(), afl-fuzz.c:7275

在这里插入图片描述

报错2:

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[-] Hmm, looks like the target binary terminated before we could complete a
    handshake with the injected code. There are two probable explanations:
 
    - The current memory limit (200 MB) is too restrictive, causing an OOM
      fault in the dynamic linker. This can be fixed with the -m option. A
      simple way to confirm the diagnosis may be:
 
      ( ulimit -Sv $[199 << 10]; /path/to/fuzzed_app )
 
      Tip: you can use http://jwilk.net/software/recidivm to quickly
      estimate the required amount of virtual memory for the binary.
 
    - Less likely, there is a horrible bug in the fuzzer. If other options
      fail, poke <lcamtuf@coredump.cx> for troubleshooting tips.
 
[-] PROGRAM ABORT : Fork server handshake failed
         Location : init_forkserver(), afl-fuzz.c:2253

在这里插入图片描述

报错3:

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[-] Hmm, looks like the target binary terminated before we could complete a
    handshake with the injected code. Perhaps there is a horrible bug in the
    fuzzer. Poke <lcamtuf@coredump.cx> for troubleshooting tips.
 
[-] PROGRAM ABORT : Fork server handshake failed
         Location : init_forkserver(), afl-fuzz.c:2253

在这里插入图片描述


[招生]科锐逆向工程师培训46期预科班将于 2023年02月09日 正式开班

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