tdebase/kdesu/kdesud/kdesud.cpp

/* vi: ts=8 sts=4 sw=4
 *
 * This file is part of the KDE project, module kdesu.
 * Copyright (C) 1999,2000 Geert Jansen <jansen@kde.org>
 * 
 *
 * kdesud.cpp: KDE su daemon. Offers "keep password" functionality to kde su.
 *
 * The socket $KDEHOME/socket-$(HOSTNAME)/kdesud_$(display) is used for communication with
 * client programs.
 *
 * The protocol: Client initiates the connection. All commands and responses
 * are terminated by a newline.
 *
 *   Client                     Server     Description
 *   ------                     ------     -----------
 *
 *   PASS <pass> <timeout>      OK         Set password for commands in
 *                                         this session. Password is
 *                                         valid for <timeout> seconds.
 *
 *   USER <user>                OK         Set the target user [required]
 *
 *   EXEC <command>             OK         Execute command <command>. If
 *                              NO         <command> has been executed
 *                                         before (< timeout) no PASS
 *                                         command is needed.
 *                                              
 *   DEL <command>              OK         Delete password for command
 *                              NO         <command>.
 *
 *   PING                       OK         Ping the server (diagnostics).
 */


#include <config.h>

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <ctype.h>
#include <string.h>
#include <stdarg.h>
#include <signal.h>
#include <pwd.h>
#include <errno.h>

#include <sys/prctl.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/resource.h>
#include <sys/wait.h>
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>                // Needed on some systems.
#endif

#include <tqptrvector.h>
#include <tqfile.h>
#include <tqregexp.h>

#include <kinstance.h>
#include <kdebug.h>
#include <klocale.h>
#include <kcmdlineargs.h>
#include <kstandarddirs.h>
#include <kaboutdata.h>
#include <kdesu/client.h>
#include <kdesu/defaults.h>
#include <ksockaddr.h>

#include "repo.h"
#include "handler.h"

#include <X11/X.h>
#include <X11/Xlib.h>

#ifndef SUN_LEN
#define SUN_LEN(ptr) ((kde_socklen_t) (((struct sockaddr_un *) 0)->sun_path) \
                     + strlen ((ptr)->sun_path))   
#endif

#define ERR strerror(errno)

// Globals

Repository *repo;
const char *Version = "1.01";
TQCString sock;
Display *x11Display;
int pipeOfDeath[2];


void kdesud_cleanup()
{
    unlink(sock);
}


// Borrowed from kdebase/kaudio/kaudioserver.cpp

extern "C" int xio_errhandler(Display *);

int xio_errhandler(Display *)
{
    kdError(1205) << "Fatal IO error, exiting...\n";
    kdesud_cleanup();
    exit(1);
    return 1;  //silence compilers
}

int initXconnection()
{
    x11Display = XOpenDisplay(NULL);
    if (x11Display != 0L) 
    {
        XSetIOErrorHandler(xio_errhandler);
        XCreateSimpleWindow(x11Display, DefaultRootWindow(x11Display), 
                0, 0, 1, 1, 0,
                BlackPixelOfScreen(DefaultScreenOfDisplay(x11Display)),
                BlackPixelOfScreen(DefaultScreenOfDisplay(x11Display)));
        return XConnectionNumber(x11Display);
    } else 
    {
        kdWarning(1205) << "Can't connect to the X Server.\n";
        kdWarning(1205) << "Might not terminate at end of session.\n";
        return -1;
    }
}

extern "C" {
  void signal_exit(int);
  void sigchld_handler(int);
}

void signal_exit(int sig)
{
    kdDebug(1205) << "Exiting on signal " << sig << "\n";
    kdesud_cleanup();
    exit(1);
}

void sigchld_handler(int)
{
    char c = ' ';
    write(pipeOfDeath[1], &c, 1);
}

/**
 * Creates an AF_UNIX socket in socket resource, mode 0600.
 */

int create_socket()
{
    int sockfd;
    ksocklen_t addrlen;
    struct stat s;

    TQCString display(getenv("DISPLAY"));
    if (display.isEmpty())
    {
        kdWarning(1205) << "$DISPLAY is not set\n";
        return -1;
    }

    // strip the screen number from the display
    display.tqreplace(TQRegExp("\\.[0-9]+$"), "");

    sock = TQFile::encodeName(locateLocal("socket", TQString("kdesud_%1").arg(static_cast<const char *>(display))));
    int stat_err=lstat(sock, &s);
    if(!stat_err && S_ISLNK(s.st_mode)) {
        kdWarning(1205) << "Someone is running a symlink attack on you\n";
        if(unlink(sock)) {
            kdWarning(1205) << "Could not delete symlink\n";
            return -1;
        }
    }

    if (!access(sock, R_OK|W_OK)) 
    {
        KDEsuClient client;
        if (client.ping() == -1) 
        {
            kdWarning(1205) << "stale socket exists\n";
            if (unlink(sock)) 
            {
                kdWarning(1205) << "Could not delete stale socket\n";
                return -1;
            }
        } else 
        {
            kdWarning(1205) << "kdesud is already running\n";
            return -1;
        }

    }

    sockfd = socket(PF_UNIX, SOCK_STREAM, 0);
    if (sockfd < 0) 
    {
        kdError(1205) << "socket(): " << ERR << "\n";
        return -1;
    }

    struct sockaddr_un addr;
    addr.sun_family = AF_UNIX;
    strncpy(addr.sun_path, sock, sizeof(addr.sun_path)-1);
    addr.sun_path[sizeof(addr.sun_path)-1] = '\000';
    addrlen = SUN_LEN(&addr);
    if (bind(sockfd, (struct sockaddr *)&addr, addrlen) < 0) 
    {
        kdError(1205) << "bind(): " << ERR << "\n";
        return -1;
    }

    struct linger lin;
    lin.l_onoff = lin.l_linger = 0;
    if (setsockopt(sockfd, SOL_SOCKET, SO_LINGER, (char *) &lin,
                   sizeof(linger)) < 0) 
    {
        kdError(1205) << "setsockopt(SO_LINGER): " << ERR << "\n";
        return -1;
    }

    int opt = 1;
    if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, (char *) &opt,
                   sizeof(opt)) < 0) 
    {
        kdError(1205) << "setsockopt(SO_REUSEADDR): " << ERR << "\n";
        return -1;
    }
    opt = 1;
    if (setsockopt(sockfd, SOL_SOCKET, SO_KEEPALIVE, (char *) &opt,
                   sizeof(opt)) < 0) 
    {
        kdError(1205) << "setsockopt(SO_KEEPALIVE): " << ERR << "\n";
        return -1;
    }
    chmod(sock, 0600);
    return sockfd;
}


/**
 * Main program
 */

int main(int argc, char *argv[])
{
    prctl(PR_SET_DUMPABLE, 0);

    KAboutData aboutData("kdesud", I18N_NOOP("KDE su daemon"),
            Version, I18N_NOOP("Daemon used by kdesu"),
            KAboutData::License_Artistic,
            "Copyright (c) 1999,2000 Geert Jansen");
    aboutData.addAuthor("Geert Jansen", I18N_NOOP("Author"),
            "jansen@kde.org", "http://www.stack.nl/~geertj/");
    KCmdLineArgs::init(argc, argv, &aboutData);
    KInstance instance(&aboutData);

    // Set core dump size to 0
    struct rlimit rlim;
    rlim.rlim_cur = rlim.rlim_max = 0;
    if (setrlimit(RLIMIT_CORE, &rlim) < 0) 
    {
        kdError(1205) << "setrlimit(): " << ERR << "\n";
        exit(1);
    }

    // Create the Unix socket.
    int sockfd = create_socket();
    if (sockfd < 0)
        exit(1);
    if (listen(sockfd, 1) < 0) 
    {
        kdError(1205) << "listen(): " << ERR << "\n";
        kdesud_cleanup();
        exit(1);
    }
    int maxfd = sockfd;

    // Ok, we're accepting connections. Fork to the background.
    pid_t pid = fork();
    if (pid == -1) 
    {
        kdError(1205) << "fork():" << ERR << "\n";
        kdesud_cleanup();
        exit(1);
    }
    if (pid)
        exit(0);

    // Make sure we exit when the display gets closed.
    int x11Fd = initXconnection();
    maxfd = QMAX(maxfd, x11Fd);

    repo = new Repository;
    TQPtrVector<ConnectionHandler> handler;
    handler.setAutoDelete(true);

    pipe(pipeOfDeath);
    maxfd = QMAX(maxfd, pipeOfDeath[0]);

    // Signal handlers 
    struct sigaction sa;
    sa.sa_handler = signal_exit;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = 0;
    sigaction(SIGHUP, &sa, 0L);
    sigaction(SIGINT, &sa, 0L);
    sigaction(SIGTERM, &sa, 0L);
    sigaction(SIGQUIT, &sa, 0L);

    sa.sa_handler = sigchld_handler;
    sa.sa_flags = SA_NOCLDSTOP;
    sigaction(SIGCHLD, &sa, 0L);
    sa.sa_handler = SIG_IGN;
    sigaction(SIGPIPE, &sa, 0L);

    // Main execution loop 

    ksocklen_t addrlen;
    struct sockaddr_un clientname;

    fd_set tmp_fds, active_fds;
    FD_ZERO(&active_fds);
    FD_SET(sockfd, &active_fds);
    FD_SET(pipeOfDeath[0], &active_fds);
    if (x11Fd != -1)
        FD_SET(x11Fd, &active_fds);

    while (1) 
    {
        tmp_fds = active_fds;
        if(x11Display)
            XFlush(x11Display);
        if (select(maxfd+1, &tmp_fds, 0L, 0L, 0L) < 0) 
        {
            if (errno == EINTR) continue;
            
            kdError(1205) << "select(): " << ERR << "\n";
            exit(1);
        }
        repo->expire();
        for (int i=0; i<=maxfd; i++) 
        {
            if (!FD_ISSET(i, &tmp_fds)) 
                continue;

            if (i == pipeOfDeath[0])
            {
                char buf[101];
                read(pipeOfDeath[0], buf, 100);
                pid_t result;
                do
                {
                    int status;
                    result = waitpid((pid_t)-1, &status, WNOHANG);
                    if (result > 0)
                    {
                        for(int j=handler.size(); j--;)
                        {
                            if (handler[j] && (handler[j]->m_pid == result))
                            {
                                handler[j]->m_exitCode = WEXITSTATUS(status);
                                handler[j]->m_hasExitCode = true;
                                handler[j]->sendExitCode();
                                handler[j]->m_pid = 0;
                                break;
                            }
                        }
                    }
                }
                while(result > 0);
            }

            if (i == x11Fd) 
            {
                // Discard X events
                XEvent event_return;
                if (x11Display)
                    while(XPending(x11Display))
                        XNextEvent(x11Display, &event_return);
                continue;
            }

            if (i == sockfd) 
            {
                // Accept new connection
                int fd;
                addrlen = 64;
                fd = accept(sockfd, (struct sockaddr *) &clientname, &addrlen);
                if (fd < 0) 
                {
                    kdError(1205) << "accept():" << ERR << "\n";
                    continue;
                }
                if (fd+1 > (int) handler.size())
                    handler.resize(fd+1);
                handler.insert(fd, new ConnectionHandler(fd));
                maxfd = TQMAX(maxfd, fd);
                FD_SET(fd, &active_fds);
                continue;
            }

            // handle alreay established connection
            if (handler[i] && handler[i]->handle() < 0) 
            {
                handler.remove(i);
                FD_CLR(i, &active_fds);
            }
        }
    }
    kdWarning(1205) << "???\n";
}