{

FILE *out=stdout;

if(retCode!=0)

{

out=stderr;

}

fprintf(out,"Usage: Xkill [display]\n\n");

fprintf(out,"display corresponds to the X server you wish to kill, with a default value of :0\n");

fprintf(out,"A regular(i.e. non-root) user is not allowed to kill the X server(s) started by other users\n");

exit(retCode);

{

struct passwd pwd, *ppwd;

char pwd_buffer[2048];

char *display=NULL;

if(argc>2)

usage(-1);

// Find the invoking user ID

if(getpwuid_r(getuid(), &pwd, pwd_buffer, sizeof(pwd_buffer), &ppwd)!=0)

{

perror("ERROR : Failed to username of invoking user\n");

exit(-1);

}

if(argc==1)

{

display=":0";

}

else

{

int dispNum=atoi(argv[1]+1);

char dispStr[256];

sprintf(dispStr,":%d",dispNum);

if((argv[1][0]!=':') || (strcmp(dispStr, argv[1])!=0) || (dispNum<0))

{

fprintf(stderr, "ERROR : Invalid display value '%s'.\n", argv[1]);

usage(-1);

}

display=argv[1];

}

char xuser_filename[4096];

sprintf(xuser_filename, "/var/run/vizstack/xuser-%s",display+1);

FILE *fp=fopen(xuser_filename, "r");

if(fp==NULL)

{

fprintf(stderr, "The specified X server (on %s) is not running", display);

exit(-1);

}

char username[4096]; // Safe static sizes I think !!

int pid;

int rgsPromptUser;

char linebuffer[4096];

if(fgets(linebuffer, sizeof(linebuffer), fp)==NULL)

{

fprintf(stderr, "Unable to get contents from vizstack xuser file");

exit(-1);

}

if(sscanf(linebuffer, "%s %d %d", username, &pid, &rgsPromptUser)!=3)

{

fprintf(stderr, "Parse error on vizstack xuser file for display %s", display);

exit(-1);

}

fclose(fp);

if((getuid()!=0) && (strcmp(username, pwd.pw_name)!=0))

{

fprintf(stderr, "You do not have permission to kill the specified X session(%s)\n", display);

exit(-1);

}

// Now shift to become the root user, to kill em all :-)

// This is done by setting the real uid to 0.

// This approach works as this binary is expected to be SUID root.

int status;

status = setreuid(0, 0);

if (status != 0)

{

perror("ERROR: Unable to set real id to euid");

exit(-1);

}

if(strcmp(username, pwd.pw_name)==0)

{

printf("Killing X server '%s'\n", display);

}

else

{

printf("Killing X server '%s' belonging to user '%s'\n", display, username);

}

// Finally, kill the thing!

if(kill(pid, SIGTERM)<0)

{

if(errno==EPERM)

{

// FIXME: this can't happen!

}

else

if(errno==ESRCH)

{

fprintf(stderr, "The X server doesn't seem to exist. Probably it's already died ?\n");

// process does not exist!

// so delete the file

unlink(xuser_filename);

exit(-1);

}

}

// Check for some time for the server to die

bool success=false;

int exitDelay=10; // FIXME: we should wait for longer & initimate users about progress.

for(int i=0;i<exitDelay;i++)

{

sleep(1);

if(getpgid(pid)!=0) // This is just a way to see if the process exists

{

// If a process doesn't exist, then we get ESRCH as the errno

// This process is running as root, so other return values are

// not possible

if(errno==ESRCH)

{

success=true;

break;

}

}

}

if(!success)

{

fprintf(stderr, "X server didn't die in %d seconds. Try kill -9\n", exitDelay);

exit(-1);

}

exit(0);