owntone-server/src/os-unix.c

/*
 * $Id$
 * Abstracts os interface
 *
 * Copyright (c) 2006 Ron Pedde (rpedde@users.sourceforge.net)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <dlfcn.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <limits.h>
#include <pthread.h>
#include <pwd.h>
#include <signal.h>
#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
#include <syslog.h>
#include <string.h>

#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif
#include <sys/types.h>
#include <sys/stat.h>
#ifdef HAVE_SYS_WAIT_H
# include <sys/wait.h>
#endif
#include <sys/time.h>
#include <sys/resource.h>

#include "conf.h"
#include "err.h"
#include "daapd.h"
#include "os-unix.h"

/** You say po-tay-to, I say po-tat-o */
#ifndef SIGCLD
# define SIGCLD SIGCHLD
#endif

/** Where to dump the pidfile */
#ifndef PIDFILE
#define PIDFILE "/var/run/mt-daapd.pid"
#endif

/* Forwards */
static int _os_daemon_start(void);
static void *_os_signal_handler(void *arg);
static int _os_start_signal_handler(pthread_t *handler_tid);
static volatile int _os_signal_pid;

/* Globals */
pthread_t _os_signal_tid;
char *_os_pidfile = PIDFILE;

/**
 * this initializes the platform... sets up signal handlers, forks to the
 * background, etc
 *
 * @param foreground whether to run in fg or fork to bg
 * @returns TRUE on success, FALSE otherwise
 */
int os_init(int foreground, char *runas) {
    int pid_fd;
    FILE *pid_fp=NULL;

    /* open the pidfile, so it can be written once we detach */
    if(!foreground) {
        if(-1 == (pid_fd = open(_os_pidfile,O_CREAT | O_WRONLY | O_TRUNC, 0644))) {
            DPRINTF(E_LOG,L_MAIN,"Error opening pidfile (%s): %s\n",
                    _os_pidfile,strerror(errno));
        } else {
            if(0 == (pid_fp = fdopen(pid_fd, "w")))
                DPRINTF(E_LOG,L_MAIN,"fdopen: %s\n",strerror(errno));
        }
        /* just to be on the safe side... */
        _os_signal_pid=0;
        _os_daemon_start();
    }

    // Drop privs here
    if(os_drop_privs(runas)) {
        DPRINTF(E_FATAL,L_MAIN,"Error in drop_privs: %s\n",strerror(errno));
    }

    /* block signals and set up the signal handling thread */
    DPRINTF(E_LOG,L_MAIN,"Starting signal handler\n");
    if(_os_start_signal_handler(&_os_signal_tid)) {
        DPRINTF(E_FATAL,L_MAIN,"Error starting signal handler %s\n",strerror(errno));
    }

    if(pid_fp) {
        /* wait to for config.pid to be set by the signal handler */
        while(!_os_signal_pid) {
            sleep(1);
        }

        fprintf(pid_fp,"%d\n",_os_signal_pid);
        fclose(pid_fp);
    }

    return TRUE;
}

/**
 * do any deinitialization necessary for the platform
 */
void os_deinit(void) {
    DPRINTF(E_LOG,L_MAIN,"Stopping signal handler\n");
    if(!pthread_kill(_os_signal_tid,SIGINT)) {
        pthread_join(_os_signal_tid,NULL);
    }
}

/**
 * start syslogging
 *
 * @returns TRUE on success, FALSE otherwise
 */
int os_opensyslog(void) {
    openlog(PACKAGE,LOG_PID,LOG_DAEMON);
    return TRUE;
}


/**
 * stop syslogging
 *
 * @returns TRUE on success, FALSE otherwise
 */
int os_closesyslog(void) {
    closelog();
    return TRUE;
}

/**
 * log a syslog message
 *
 * @param level log level (1-9: 1=fatal, 9=debug)
 * @param msg message to log to the syslog
 * @returns TRUE on success, FALSE otherwise
 */
int os_syslog(int level, char *msg) {
    int priority;

    switch(level) {
    case 0:
    case 1:
        priority = LOG_ALERT;
        break;
    case 2:
    case 3:
    case 4:
        priority = LOG_NOTICE;
        break;
    case 5:
    case 6:
    case 7:
    case 8:
        priority = LOG_INFO;
        break;

    case 9:
    default:
        priority = LOG_DEBUG;
        break;
    }

    syslog(priority,"%s",msg);
    return TRUE;
}


/**
 * os-specific chown
 *
 *
 */
extern int os_chown(char *path, char *user) {
    struct passwd *pw=NULL;

    DPRINTF(E_DBG,L_MISC,"Chowning %s to %s\n",path,user);

    /* drop privs */
    if(getuid() == (uid_t)0) {
        if(atoi(user)) {
            pw=getpwuid((uid_t)atoi(user)); /* doh! */
        } else {
            pw=getpwnam(user);
        }

        if(pw) {
            if(initgroups(user,pw->pw_gid) != 0 ||
               chown(path, pw->pw_uid, pw->pw_gid) != 0) {
                DPRINTF(E_LOG,L_MISC,"Couldn't chown %s, gid=%d, uid=%d\n",
                        user,pw->pw_gid, pw->pw_uid);
                return FALSE;
            }
        } else {
            DPRINTF(E_LOG,L_MISC,"Couldn't lookup user %s for chown\n",user);
            return FALSE;
        }
    }

    DPRINTF(E_DBG,L_MISC,"Success!\n");
    return TRUE;
}

/**
 * Fork and exit.  Stolen pretty much straight from Stevens.
 *
 * @returns 0 on success, -1 with errno set on error
 */
int _os_daemon_start(void) {
    int childpid, fd;

    signal(SIGTTOU, SIG_IGN);
    signal(SIGTTIN, SIG_IGN);
    signal(SIGTSTP, SIG_IGN);

    // Fork and exit
    if ((childpid = fork()) < 0) {
        fprintf(stderr, "Can't fork!\n");
        return -1;
    } else if (childpid > 0)
        exit(0);

#ifdef SETPGRP_VOID
    setpgrp();
#else
    setpgrp(0,0);
#endif

#ifdef TIOCNOTTY
    if ((fd = open("/dev/tty", O_RDWR)) >= 0) {
        ioctl(fd, TIOCNOTTY, (char *) NULL);
        close(fd);
    }
#endif

    if((fd = open("/dev/null", O_RDWR, 0)) != -1) {
        dup2(fd, STDIN_FILENO);
        dup2(fd, STDOUT_FILENO);
        dup2(fd, STDERR_FILENO);
        if (fd > 2)
            close(fd);
    }

    /*
    for (fd = 0; fd < FOPEN_MAX; fd++)
        close(fd);
    */

    errno = 0;

    chdir("/");
    umask(0);

    return 0;
}


/**
 * Drop privs.  This allows mt-daapd to run as a non-privileged user.
 * Hopefully this will limit the damage it could do if exploited
 * remotely.  Note that only the user need be specified.  GID
 * is set to the primary group of the user.
 *
 * \param user user to run as (or UID)
 */
int os_drop_privs(char *user) {
    int err;
    struct passwd *pw=NULL;

    /* drop privs */
    if(getuid() == (uid_t)0) {
        if(atoi(user)) {
            pw=getpwuid((uid_t)atoi(user)); /* doh! */
        } else {
            pw=getpwnam(user);
        }

        if(pw) {
            if(initgroups(user,pw->pw_gid) != 0 ||
               setgid(pw->pw_gid) != 0 ||
               setuid(pw->pw_uid) != 0) {
                err=errno;
                fprintf(stderr,"Couldn't change to %s, gid=%d, uid=%d\n",
                        user,pw->pw_gid, pw->pw_uid);
                errno=err;
                return -1;
            }
        } else {
            err=errno;
            fprintf(stderr,"Couldn't lookup user %s\n",user);
            errno=err;
            return -1;
        }
    }

    return 0;
}

/**
 * Wait for signals and flag the main process.  This is
 * a thread handler for the signal processing thread.  It
 * does absolutely nothing except wait for signals.  The rest
 * of the threads are running with signals blocked, so this thread
 * is guaranteed to catch all the signals.  It sets flags in
 * the config structure that the main thread looks for.  Specifically,
 * the stop flag (from an INT signal), and the reload flag (from HUP).
 * \param arg NULL, but required of a thread procedure
 */
void *_os_signal_handler(void *arg) {
    sigset_t intmask;
    int sig;
    int status;

    config.stop=0;
    config.reload=0;
    _os_signal_pid=getpid();

    DPRINTF(E_WARN,L_MAIN,"Signal handler started\n");

    while(!config.stop) {
        if((sigemptyset(&intmask) == -1) ||
           (sigaddset(&intmask, SIGCLD) == -1) ||
           (sigaddset(&intmask, SIGINT) == -1) ||
           (sigaddset(&intmask, SIGHUP) == -1) ||
           (sigwait(&intmask, &sig) == -1)) {
            DPRINTF(E_FATAL,L_MAIN,"Error waiting for signals.  Aborting\n");
        } else {
            /* process the signal */
            switch(sig) {
            case SIGCLD:
                DPRINTF(E_LOG,L_MAIN,"Got CLD signal.  Reaping\n");
                while (wait3(&status, WNOHANG, NULL) > 0) {
                }
                break;
            case SIGINT:
                DPRINTF(E_LOG,L_MAIN,"Got INT signal. Notifying daap server.\n");
                config.stop=1;
                return NULL;
                break;
            case SIGHUP:
                DPRINTF(E_LOG,L_MAIN,"Got HUP signal. Notifying daap server.\n");
                /* if we can't reload, it keeps the old config file,
                 * so no real damage */
                conf_reload();
                err_reopen();

                config.reload=1;
                break;
            default:
                DPRINTF(E_LOG,L_MAIN,"What am I doing here?\n");
                break;
            }
        }
    }

    return NULL;
}

/**
 * Block signals, then start the signal handler.  The
 * signal handler started by spawning a new thread on
 * signal_handler().
 *
 * \returns 0 on success, -1 on failure with errno set
 */
int _os_start_signal_handler(pthread_t *handler_tid) {
    int error;
    sigset_t set;

    if((sigemptyset(&set) == -1) ||
       (sigaddset(&set,SIGINT) == -1) ||
       (sigaddset(&set,SIGHUP) == -1) ||
       (sigaddset(&set,SIGCLD) == -1) ||
       (sigprocmask(SIG_BLOCK, &set, NULL) == -1)) {
        DPRINTF(E_LOG,L_MAIN,"Error setting signal set\n");
        return -1;
    }

    if((error=pthread_create(handler_tid, NULL, _os_signal_handler, NULL))) {
        errno=error;
        DPRINTF(E_LOG,L_MAIN,"Error creating signal_handler thread\n");
        return -1;
    }

    /* we'll not detach this... let's join it */
    //pthread_detach(handler_tid);
    return 0;
}

/**
 * set the pidfile to a non-default value
 *
 * @param file file to use as pidfile
 */
 void os_set_pidfile(char *file) {
    _os_pidfile = file;
 }



/**
 * load a shared library
 *
 * @param
 */
void *os_loadlib(char **pe, char *path) {
    void *retval;

    if(!(retval = dlopen(path,RTLD_NOW)))
        *pe = strdup(dlerror());

    return retval;
}

void *os_libfunc(char **pe, void *handle, char *function) {
    void *retval;

    if(!(retval = dlsym(handle,function)))
        *pe = strdup(dlerror());

    return retval;
}

int os_unload(void *handle) {
    return dlclose(handle);
}