daemon.c

   1 /*
   2  * Copyright (C) 1997-2006 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file daemon.c some helpers for programs that detach from the console */
   8 #include "para.h"
   9 #include "daemon.h"
  10 #include <pwd.h>
  11
  12 /* getgrnam() */
  13 #include <sys/types.h>
  14 #include <grp.h>
  15
  16 #include "string.h"
  17
  18 /**
  19  * do the usual stuff to become a daemon
  20  *
  21  * Fork, become session leader, dup fd 0, 1, 2 to /dev/null.
  22  *
  23  * \sa fork(2), setsid(2), dup(2)
  24  */
  25 void daemon_init(void)
  26 {
  27         pid_t pid;
  28         int null;
  29
  30         PARA_INFO_LOG("%s", "daemonizing\n");
  31         if ((pid = fork()) < 0) {
  32                 PARA_EMERG_LOG("%s", "failed to init daemon\n");
  33                 exit(EXIT_FAILURE);
  34         } else if (pid)
  35                 exit(EXIT_SUCCESS); /* parent exits */
  36         /* child */
  37         setsid(); /* become session leader */
  38         chdir("/");
  39         umask(0);
  40
  41         null = open("/dev/null", O_RDONLY);
  42         if (null < 0)
  43                 exit(EXIT_FAILURE);
  44         dup2(null, STDIN_FILENO);
  45         dup2(null, STDOUT_FILENO);
  46         dup2(null, STDERR_FILENO);
  47         close(null);
  48 }
  49
  50 /**
  51  * fopen() a file in append mode
  52  *
  53  * \param logfile_name the name of the file to open
  54  *
  55  * Either calls exit() or returns a valid file handle.
  56  */
  57 FILE *open_log(const char *logfile_name)
  58 {
  59         FILE *logfile;
  60
  61         if (!logfile_name)
  62                 return NULL;
  63         if (!(logfile = fopen(logfile_name, "a"))) {
  64                 PARA_EMERG_LOG("can not open %s, uid: %d\n", logfile_name,
  65                         getuid());
  66                 exit(EXIT_FAILURE);
  67         }
  68         setlinebuf(logfile);
  69         return logfile;
  70 }
  71
  72 /**
  73  * close the log file of the daemon
  74  *
  75  * \param logfile the log file handle
  76  *
  77  * It's OK to call this with logfile == NULL
  78  */
  79 void close_log(FILE* logfile)
  80 {
  81         if (!logfile)
  82                 return;
  83         PARA_INFO_LOG("%s", "closing logfile\n");
  84         fclose(logfile);
  85 }
  86
  87 /**
  88  * log the startup message containing the paraslash version
  89  */
  90 void log_welcome(const char *whoami, int loglevel)
  91 {
  92         PARA_INFO_LOG("welcome to %s " PACKAGE_VERSION " ("BUILD_DATE")\n",
  93                 whoami);
  94         PARA_DEBUG_LOG("using loglevel %d\n", loglevel);
  95 }
  96
  97 /**
  98  * give up superuser privileges
  99  *
 100  * \param username the user to switch to
 101  * \param groupname the group to switch to
 102  *
 103  * This function returns immediately if not invoked with EUID zero. Otherwise,
 104  * it tries to obtain the GID of \a groupname and the UID of \a username.  On
 105  * success, effective and real GID/UID and the saved set-group-ID/set-user-ID
 106  * are all set accordingly. On errors, an appropriate message is logged and
 107  * exit() is called to terminate the process.
 108  *
 109  * \sa getpwnam(3), getuid(2), setuid(2), getgrnam(2), setgid(2)
 110  */
 111 void para_drop_privileges(const char *username, const char *groupname)
 112 {
 113         struct passwd *p;
 114         char *tmp;
 115
 116         if (geteuid())
 117                 return;
 118         if (groupname) {
 119                 struct group *g = getgrnam(groupname);
 120                 if (!g) {
 121                         PARA_EMERG_LOG("failed to get group %s\n", groupname);
 122                         exit(EXIT_FAILURE);
 123                 }
 124                 if (setgid(g->gr_gid) < 0) {
 125                         PARA_EMERG_LOG("failed to set group id %d (%s)\n",
 126                                 g->gr_gid, strerror(errno));
 127                         exit(EXIT_FAILURE);
 128                 }
 129         }
 130         if (!username) {
 131                 PARA_EMERG_LOG("%s", "root privileges, but no user option given\n");
 132                 exit(EXIT_FAILURE);
 133         }
 134         tmp = para_strdup(username);
 135         p = getpwnam(tmp);
 136         free(tmp);
 137         if (!p) {
 138                 PARA_EMERG_LOG("%s", "no such user\n");
 139                 exit(EXIT_FAILURE);
 140         }
 141         PARA_INFO_LOG("%s", "dropping root privileges\n");
 142         setuid(p->pw_uid);
 143         PARA_DEBUG_LOG("uid: %d, euid: %d\n", getuid(), geteuid());
 144 }
 145
 146 /**
 147  * set/get the server uptime
 148  *
 149  * \param set_or_get chose one of the two modes
 150  *
 151  * This should be called at startup time with \a set_or_get equal to \p
 152  * UPTIME_SET which sets the uptime to zero.  Subsequent calls with \a
 153  * set_or_get equal to \p UPTIME_GET return the number of seconds ellapsed
 154  * since the last reset.
 155  *
 156  * \sa time(2), difftime(3)
 157  */
 158 time_t server_uptime(enum uptime set_or_get)
 159 {
 160         static time_t startuptime;
 161         time_t now;
 162         double diff;
 163
 164         if (set_or_get == UPTIME_SET) {
 165                 time(&startuptime);
 166                 return 0;
 167         }
 168         time(&now);
 169         diff = difftime(now, startuptime);
 170         return (time_t) diff;
 171 }
 172
 173 /**
 174  * construct string containing uptime
 175  *
 176  * The format of the returned string is "days:hours:minutes"
 177  *
 178  * \sa server_uptime
 179  */
 180 __malloc char *uptime_str(void)
 181 {
 182         time_t t = server_uptime(UPTIME_GET);
 183         return make_message("%li:%02li:%02li", t / 86400,
 184                 (t / 3600) % 24, (t / 60) % 60);
 185 }