Apache mod_proxy模块HTTP分块编码整数溢出漏洞

发布日期:2010-01-27
更新日期:2010-01-28

受影响系统:
Apache Group Apache 1.3.x
描述:
--------------------------------------------------------------------------------
BUGTRAQ  ID: 37966
CVE(CAN) ID: CVE-2010-0010

Apache HTTP Server是一款流行的Web服务器。

Apache服务器的mod_proxy模块在执行字符类型转换时存在最终可导致堆溢出的整数溢出漏洞。以下是有漏洞的代码段:

"./src/modules/proxy/proxy_util.c"
long int ap_proxy_send_fb(BUFF *f, request_rec *r, cache_req *c, off_t len, int nowrite, int chunked, size_t recv_buffer_size)
{

...
    size_t buf_size;
    long remaining = 0;
...

    for (end_of_chunk = ok = 1; ok;) {
...
        if (chunked) {
            long chunk_start = 0;
            n = 0;

            /* start of a new chunk */
            if (end_of_chunk) {
                end_of_chunk = 0;
                /* get the chunk size from the stream */
                chunk_start = ap_getline(buf, buf_size, f, 0);    <----------------  [0] reading line from traffic (socket)
                if ((chunk_start <= 0) || ((size_t)chunk_start + 1 >= buf_size) || !ap_isxdigit(*buf)) {
                    n = -1;
                }
                /* parse the chunk size */
                else {
                    remaining = ap_get_chunk_size(buf);           <----------------  [1] convert readed data to 'long' size!
                    if (remaining == 0) { /* Last chunk indicated, get footers */
...
...
                        }
                    }
                    else if (remaining < 0) {
                        n = -1;
                        ap_log_rerror(APLOG_MARK, APLOG_DEBUG|APLOG_NOERRNO, r,
                                      "proxy: remote protocol error, invalid chunk size");
                    }
                }
            }

            /* read the chunk */
            if (remaining > 0) {
                n = ap_bread(f, buf, MIN((int)buf_size, (int)remaining));     <------------- [2] convert 'long' to 'int' !!!!
                if (n > -1) {
                    remaining -= n;
                    end_of_chunk = (remaining == 0);
                }
            }
...
...
}

服务器在读取HTTP头时,如果是分块连接,在[0]处会等待并从套接字读取块大小的数据,在[1]处将所接收到的数据转换为long类型;如果存在正值的块大小,[2]处直接将long类型转换为int类型,这在amd64架构上可能触发整数溢出。

<*来源:Adam Zabrocki ([email protected]
 
  链接:http://site.pi3.com.pl/adv/mod_proxy.txt
        http://secunia.com/advisories/38319/
*>

测试方法:
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警 告

以下程序(方法)可能带有攻击性,仅供安全研究与教学之用。使用者风险自负!

http://site.pi3.com.pl/adv/mod_proxy.txt

建议:
--------------------------------------------------------------------------------
厂商补丁:

Apache Group
------------
目前厂商还没有提供补丁或者升级程序,我们建议使用此软件的用户随时关注厂商的主页以获取最新版本:

http://www.apache.org

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