src/daemon.c

   1 #ifdef HAVE_CONFIG_H
   2 #include <config.h>
   3 #endif
   4 #include <stdio.h>
   5 #include <stdlib.h>
   6 #include <unistd.h>
   7 #include <fcntl.h>
   8 #include <errno.h>
   9 #include <signal.h>
  10 #include <string.h>
  11 #include <sys/types.h>
  12 #include <pwd.h>
  13 #include <grp.h>
  14 #include <pthread.h>
  15 #include <sys/wait.h>
  16 #include <sys/stat.h>
  17
  18 #include "common.h"
  19 #include "appconfig.h"
  20 #include "log.h"
  21 #include "web_client.h"
  22 #include "plugins_d.h"
  23 #include "rrd.h"
  24 #include "popen.h"
  25 #include "main.h"
  26 #include "daemon.h"
  27
  28 char pidfile[FILENAME_MAX + 1] = "";
  29 int pidfd = -1;
  30
  31 void sig_handler(int signo)
  32 {
  33         if(signo)
  34                 netdata_exit = 1;
  35 }
  36
  37 int become_user(const char *username)
  38 {
  39         struct passwd *pw = getpwnam(username);
  40         if(!pw) {
  41                 error("User %s is not present.", username);
  42                 return -1;
  43         }
  44
  45         uid_t uid = pw->pw_uid;
  46         gid_t gid = pw->pw_gid;
  47
  48         int ngroups =  sysconf(_SC_NGROUPS_MAX);
  49         gid_t *supplementary_groups = NULL;
  50         if(ngroups) {
  51                 supplementary_groups = malloc(sizeof(gid_t) * ngroups);
  52                 if(supplementary_groups) {
  53                         if(getgrouplist(username, gid, supplementary_groups, &ngroups) == -1) {
  54                                 error("Cannot get supplementary groups of user '%s'.", username);
  55                                 free(supplementary_groups);
  56                                 supplementary_groups = NULL;
  57                                 ngroups = 0;
  58                         }
  59                 }
  60                 else fatal("Cannot allocate memory for %d supplementary groups", ngroups);
  61         }
  62
  63         if(pidfile[0] && getuid() != uid) {
  64                 // we are dropping privileges
  65                 if(chown(pidfile, uid, gid) != 0)
  66                         error("Cannot chown pidfile '%s' to user '%s'", pidfile, username);
  67
  68                 else if(pidfd != -1) {
  69                         // not need to keep it open
  70                         close(pidfd);
  71                         pidfd = -1;
  72                 }
  73         }
  74         else if(pidfd != -1) {
  75                 // not need to keep it open
  76                 close(pidfd);
  77                 pidfd = -1;
  78         }
  79
  80         if(supplementary_groups && ngroups) {
  81                 if(setgroups(ngroups, supplementary_groups) == -1)
  82                         error("Cannot set supplementary groups for user '%s'", username);
  83
  84                 free(supplementary_groups);
  85                 supplementary_groups = NULL;
  86                 ngroups = 0;
  87         }
  88
  89         if(setresgid(gid, gid, gid) != 0) {
  90                 error("Cannot switch to user's %s group (gid: %d).", username, gid);
  91                 return -1;
  92         }
  93
  94         if(setresuid(uid, uid, uid) != 0) {
  95                 error("Cannot switch to user %s (uid: %d).", username, uid);
  96                 return -1;
  97         }
  98
  99         if(setgid(gid) != 0) {
 100                 error("Cannot switch to user's %s group (gid: %d).", username, gid);
 101                 return -1;
 102         }
 103         if(setegid(gid) != 0) {
 104                 error("Cannot effectively switch to user's %s group (gid: %d).", username, gid);
 105                 return -1;
 106         }
 107         if(setuid(uid) != 0) {
 108                 error("Cannot switch to user %s (uid: %d).", username, uid);
 109                 return -1;
 110         }
 111         if(seteuid(uid) != 0) {
 112                 error("Cannot effectively switch to user %s (uid: %d).", username, uid);
 113                 return -1;
 114         }
 115
 116         return(0);
 117 }
 118
 119 int become_daemon(int dont_fork, int close_all_files, const char *user, const char *input, const char *output, const char *error, const char *access, int *access_fd, FILE **access_fp)
 120 {
 121         fflush(NULL);
 122
 123         // open the files before forking
 124         int input_fd = -1, output_fd = -1, error_fd = -1, dev_null;
 125
 126         if(input && *input) {
 127                 if((input_fd = open(input, O_RDONLY, 0666)) == -1) {
 128                         error("Cannot open input file '%s'.", input);
 129                         return -1;
 130                 }
 131         }
 132
 133         if(output && *output) {
 134                 if((output_fd = open(output, O_RDWR | O_APPEND | O_CREAT, 0666)) == -1) {
 135                         error("Cannot open output log file '%s'", output);
 136                         if(input_fd != -1) close(input_fd);
 137                         return -1;
 138                 }
 139         }
 140
 141         if(error && *error) {
 142                 if((error_fd = open(error, O_RDWR | O_APPEND | O_CREAT, 0666)) == -1) {
 143                         error("Cannot open error log file '%s'.", error);
 144                         if(input_fd != -1) close(input_fd);
 145                         if(output_fd != -1) close(output_fd);
 146                         return -1;
 147                 }
 148         }
 149
 150         if(access && *access && access_fd) {
 151                 if((*access_fd = open(access, O_RDWR | O_APPEND | O_CREAT, 0666)) == -1) {
 152                         error("Cannot open access log file '%s'", access);
 153                         if(input_fd != -1) close(input_fd);
 154                         if(output_fd != -1) close(output_fd);
 155                         if(error_fd != -1) close(error_fd);
 156                         return -1;
 157                 }
 158
 159                 if(access_fp) {
 160                         *access_fp = fdopen(*access_fd, "w");
 161                         if(!*access_fp) {
 162                                 error("Cannot migrate file's '%s' fd %d.", access, *access_fd);
 163                                 if(input_fd != -1) close(input_fd);
 164                                 if(output_fd != -1) close(output_fd);
 165                                 if(error_fd != -1) close(error_fd);
 166                                 close(*access_fd);
 167                                 *access_fd = -1;
 168                                 return -1;
 169                         }
 170                         if(setvbuf(*access_fp, NULL, _IOLBF, 0) != 0)
 171                                 error("Cannot set line buffering on access.log");
 172                 }
 173         }
 174
 175         if((dev_null = open("/dev/null", O_RDWR, 0666)) == -1) {
 176                 perror("Cannot open /dev/null");
 177                 if(input_fd != -1) close(input_fd);
 178                 if(output_fd != -1) close(output_fd);
 179                 if(error_fd != -1) close(error_fd);
 180                 if(access && access_fd && *access_fd != -1) {
 181                         close(*access_fd);
 182                         *access_fd = -1;
 183                         if(access_fp) {
 184                                 fclose(*access_fp);
 185                                 *access_fp = NULL;
 186                         }
 187                 }
 188                 return -1;
 189         }
 190
 191         // all files opened
 192         // lets do it
 193
 194         if(!dont_fork) {
 195                 int i = fork();
 196                 if(i == -1) {
 197                         perror("cannot fork");
 198                         exit(1);
 199                 }
 200                 if(i != 0) {
 201                         exit(0); // the parent
 202                 }
 203
 204                 // become session leader
 205                 if (setsid() < 0) {
 206                         perror("Cannot become session leader.");
 207                         exit(2);
 208                 }
 209         }
 210
 211         // fork() again
 212         if(!dont_fork) {
 213                 int i = fork();
 214                 if(i == -1) {
 215                         perror("cannot fork");
 216                         exit(1);
 217                 }
 218                 if(i != 0) {
 219                         exit(0); // the parent
 220                 }
 221         }
 222
 223         // Set new file permissions
 224         umask(0);
 225
 226         // close all files
 227         if(close_all_files) {
 228                 int i;
 229                 for(i = (int) (sysconf(_SC_OPEN_MAX) - 1); i > 0; i--)
 230                         if(
 231                                 ((access_fd && i != *access_fd) || !access_fd)
 232                                 && i != dev_null
 233                                 && i != input_fd
 234                                 && i != output_fd
 235                                 && i != error_fd
 236                                 && fd_is_valid(i)
 237                                 ) close(i);
 238         }
 239         else {
 240                 close(STDIN_FILENO);
 241                 close(STDOUT_FILENO);
 242                 close(STDERR_FILENO);
 243         }
 244
 245         // put the opened files
 246         // to our standard file descriptors
 247         if(input_fd != -1) {
 248                 if(input_fd != STDIN_FILENO) {
 249                         dup2(input_fd, STDIN_FILENO);
 250                         close(input_fd);
 251                 }
 252                 input_fd = -1;
 253         }
 254         else dup2(dev_null, STDIN_FILENO);
 255
 256         if(output_fd != -1) {
 257                 if(output_fd != STDOUT_FILENO) {
 258                         dup2(output_fd, STDOUT_FILENO);
 259                         close(output_fd);
 260                 }
 261
 262                 if(setvbuf(stdout, NULL, _IOLBF, 0) != 0)
 263                         error("Cannot set line buffering on debug.log");
 264
 265                 output_fd = -1;
 266         }
 267         else dup2(dev_null, STDOUT_FILENO);
 268
 269         if(error_fd != -1) {
 270                 if(error_fd != STDERR_FILENO) {
 271                         dup2(error_fd, STDERR_FILENO);
 272                         close(error_fd);
 273                 }
 274
 275                 if(setvbuf(stderr, NULL, _IOLBF, 0) != 0)
 276                         error("Cannot set line buffering on error.log");
 277
 278                 error_fd = -1;
 279         }
 280         else dup2(dev_null, STDERR_FILENO);
 281
 282         // close /dev/null
 283         if(dev_null != STDIN_FILENO && dev_null != STDOUT_FILENO && dev_null != STDERR_FILENO)
 284                 close(dev_null);
 285
 286         // generate our pid file
 287         if(pidfile[0]) {
 288                 pidfd = open(pidfile, O_RDWR | O_CREAT, 0644);
 289                 if(pidfd >= 0) {
 290                         if(ftruncate(pidfd, 0) != 0)
 291                                 error("Cannot truncate pidfile '%s'.", pidfile);
 292
 293                         char b[100];
 294                         sprintf(b, "%d\n", getpid());
 295                         ssize_t i = write(pidfd, b, strlen(b));
 296                         if(i <= 0)
 297                                 error("Cannot write pidfile '%s'.", pidfile);
 298
 299                         // don't close it, we might need it at exit
 300                         // close(pidfd);
 301                 }
 302                 else error("Failed to open pidfile '%s'.", pidfile);
 303         }
 304
 305         if(user && *user) {
 306                 if(become_user(user) != 0) {
 307                         error("Cannot become user '%s'. Continuing as we are.", user);
 308                 }
 309                 else info("Successfully became user '%s'.", user);
 310         }
 311         else if(pidfd != -1)
 312                 close(pidfd);
 313
 314         return(0);
 315 }