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 static void properly_chown_netdata_generated_file(int fd, uid_t uid, gid_t gid) {
  38         if(fd == -1) return;
  39
  40         struct stat buf;
  41
  42         if(fstat(fd, &buf) == -1) {
  43                 error("Cannot fstat() fd %d", fd);
  44                 return;
  45         }
  46
  47         if((buf.st_uid != uid || buf.st_gid != gid) && S_ISREG(buf.st_mode)) {
  48                 if(fchown(fd, uid, gid) == -1)
  49                         error("Cannot fchown() fd %d.", fd);
  50         }
  51 }
  52
  53 int become_user(const char *username, int access_fd, int output_fd, int error_fd, int pid_fd)
  54 {
  55         struct passwd *pw = getpwnam(username);
  56         if(!pw) {
  57                 error("User %s is not present.", username);
  58                 return -1;
  59         }
  60
  61         uid_t uid = pw->pw_uid;
  62         gid_t gid = pw->pw_gid;
  63
  64         int ngroups =  sysconf(_SC_NGROUPS_MAX);
  65         gid_t *supplementary_groups = NULL;
  66         if(ngroups) {
  67                 supplementary_groups = malloc(sizeof(gid_t) * ngroups);
  68                 if(supplementary_groups) {
  69                         if(getgrouplist(username, gid, supplementary_groups, &ngroups) == -1) {
  70                                 error("Cannot get supplementary groups of user '%s'.", username);
  71                                 free(supplementary_groups);
  72                                 supplementary_groups = NULL;
  73                                 ngroups = 0;
  74                         }
  75                 }
  76                 else fatal("Cannot allocate memory for %d supplementary groups", ngroups);
  77         }
  78
  79         properly_chown_netdata_generated_file(access_fd, uid, gid);
  80         properly_chown_netdata_generated_file(output_fd, uid, gid);
  81         properly_chown_netdata_generated_file(error_fd, uid, gid);
  82         properly_chown_netdata_generated_file(pid_fd, uid, gid);
  83
  84         if(supplementary_groups && ngroups) {
  85                 if(setgroups(ngroups, supplementary_groups) == -1)
  86                         error("Cannot set supplementary groups for user '%s'", username);
  87
  88                 free(supplementary_groups);
  89                 supplementary_groups = NULL;
  90                 ngroups = 0;
  91         }
  92
  93         if(setresgid(gid, gid, gid) != 0) {
  94                 error("Cannot switch to user's %s group (gid: %d).", username, gid);
  95                 return -1;
  96         }
  97
  98         if(setresuid(uid, uid, uid) != 0) {
  99                 error("Cannot switch to user %s (uid: %d).", username, uid);
 100                 return -1;
 101         }
 102
 103         if(setgid(gid) != 0) {
 104                 error("Cannot switch to user's %s group (gid: %d).", username, gid);
 105                 return -1;
 106         }
 107         if(setegid(gid) != 0) {
 108                 error("Cannot effectively switch to user's %s group (gid: %d).", username, gid);
 109                 return -1;
 110         }
 111         if(setuid(uid) != 0) {
 112                 error("Cannot switch to user %s (uid: %d).", username, uid);
 113                 return -1;
 114         }
 115         if(seteuid(uid) != 0) {
 116                 error("Cannot effectively switch to user %s (uid: %d).", username, uid);
 117                 return -1;
 118         }
 119
 120         return(0);
 121 }
 122
 123 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)
 124 {
 125         fflush(NULL);
 126
 127         // open the files before forking
 128         int input_fd = -1, output_fd = -1, error_fd = -1, dev_null;
 129
 130         if(input && *input) {
 131                 if((input_fd = open(input, O_RDONLY, 0666)) == -1) {
 132                         error("Cannot open input file '%s'.", input);
 133                         return -1;
 134                 }
 135         }
 136
 137         if(output && *output && strcmp(output, "/dev/null") != 0) {
 138                 if((output_fd = open(output, O_RDWR | O_APPEND | O_CREAT, 0666)) == -1) {
 139                         error("Cannot open output log file '%s'", output);
 140                         if(input_fd != -1) close(input_fd);
 141                         return -1;
 142                 }
 143         }
 144
 145         if(error && *error && strcmp(error, "/dev/null") != 0) {
 146                 if((error_fd = open(error, O_RDWR | O_APPEND | O_CREAT, 0666)) == -1) {
 147                         error("Cannot open error log file '%s'.", error);
 148                         if(input_fd != -1) close(input_fd);
 149                         if(output_fd != -1) close(output_fd);
 150                         return -1;
 151                 }
 152         }
 153
 154         if(access && *access && access_fd && strcmp(access, "/dev/null") != 0) {
 155                 if((*access_fd = open(access, O_RDWR | O_APPEND | O_CREAT, 0666)) == -1) {
 156                         error("Cannot open access log file '%s'", access);
 157                         if(input_fd != -1) close(input_fd);
 158                         if(output_fd != -1) close(output_fd);
 159                         if(error_fd != -1) close(error_fd);
 160                         return -1;
 161                 }
 162
 163                 if(access_fp) {
 164                         *access_fp = fdopen(*access_fd, "w");
 165                         if(!*access_fp) {
 166                                 error("Cannot migrate file's '%s' fd %d.", access, *access_fd);
 167                                 if(input_fd != -1) close(input_fd);
 168                                 if(output_fd != -1) close(output_fd);
 169                                 if(error_fd != -1) close(error_fd);
 170                                 close(*access_fd);
 171                                 *access_fd = -1;
 172                                 return -1;
 173                         }
 174                         if(setvbuf(*access_fp, NULL, _IOLBF, 0) != 0)
 175                                 error("Cannot set line buffering on access.log");
 176                 }
 177         }
 178
 179         if((dev_null = open("/dev/null", O_RDWR, 0666)) == -1) {
 180                 perror("Cannot open /dev/null");
 181                 if(input_fd != -1) close(input_fd);
 182                 if(output_fd != -1) close(output_fd);
 183                 if(error_fd != -1) close(error_fd);
 184                 if(access && access_fd && *access_fd != -1) {
 185                         close(*access_fd);
 186                         *access_fd = -1;
 187                         if(access_fp) {
 188                                 fclose(*access_fp);
 189                                 *access_fp = NULL;
 190                         }
 191                 }
 192                 return -1;
 193         }
 194
 195         // all files opened
 196         // lets do it
 197
 198         if(!dont_fork) {
 199                 int i = fork();
 200                 if(i == -1) {
 201                         perror("cannot fork");
 202                         exit(1);
 203                 }
 204                 if(i != 0) {
 205                         exit(0); // the parent
 206                 }
 207
 208                 // become session leader
 209                 if (setsid() < 0) {
 210                         perror("Cannot become session leader.");
 211                         exit(2);
 212                 }
 213         }
 214
 215         // fork() again
 216         if(!dont_fork) {
 217                 int i = fork();
 218                 if(i == -1) {
 219                         perror("cannot fork");
 220                         exit(1);
 221                 }
 222                 if(i != 0) {
 223                         exit(0); // the parent
 224                 }
 225         }
 226
 227         // Set new file permissions
 228         umask(0);
 229
 230         // close all files
 231         if(close_all_files) {
 232                 int i;
 233                 for(i = (int) (sysconf(_SC_OPEN_MAX) - 1); i > 0; i--)
 234                         if(
 235                                 ((access_fd && i != *access_fd) || !access_fd)
 236                                 && i != dev_null
 237                                 && i != input_fd
 238                                 && i != output_fd
 239                                 && i != error_fd
 240                                 && fd_is_valid(i)
 241                                 ) close(i);
 242         }
 243         else {
 244                 close(STDIN_FILENO);
 245                 close(STDOUT_FILENO);
 246                 close(STDERR_FILENO);
 247         }
 248
 249         // put the opened files
 250         // to our standard file descriptors
 251         if(input_fd != -1) {
 252                 if(input_fd != STDIN_FILENO) {
 253                         dup2(input_fd, STDIN_FILENO);
 254                         close(input_fd);
 255                 }
 256                 input_fd = -1;
 257         }
 258         else dup2(dev_null, STDIN_FILENO);
 259
 260         if(output_fd != -1) {
 261                 if(output_fd != STDOUT_FILENO) {
 262                         dup2(output_fd, STDOUT_FILENO);
 263                         close(output_fd);
 264                 }
 265
 266                 if(setvbuf(stdout, NULL, _IOLBF, 0) != 0)
 267                         error("Cannot set line buffering on debug.log");
 268
 269                 output_fd = STDOUT_FILENO;
 270         }
 271         else dup2(dev_null, STDOUT_FILENO);
 272
 273         if(error_fd != -1) {
 274                 if(error_fd != STDERR_FILENO) {
 275                         dup2(error_fd, STDERR_FILENO);
 276                         close(error_fd);
 277                 }
 278
 279                 if(setvbuf(stderr, NULL, _IOLBF, 0) != 0)
 280                         error("Cannot set line buffering on error.log");
 281
 282                 error_fd = STDERR_FILENO;
 283         }
 284         else dup2(dev_null, STDERR_FILENO);
 285
 286         // close /dev/null
 287         if(dev_null != STDIN_FILENO && dev_null != STDOUT_FILENO && dev_null != STDERR_FILENO)
 288                 close(dev_null);
 289
 290         // generate our pid file
 291         int pidfd = -1;
 292         if(pidfile[0]) {
 293                 pidfd = open(pidfile, O_RDWR | O_CREAT, 0644);
 294                 if(pidfd >= 0) {
 295                         if(ftruncate(pidfd, 0) != 0)
 296                                 error("Cannot truncate pidfile '%s'.", pidfile);
 297
 298                         char b[100];
 299                         sprintf(b, "%d\n", getpid());
 300                         ssize_t i = write(pidfd, b, strlen(b));
 301                         if(i <= 0)
 302                                 error("Cannot write pidfile '%s'.", pidfile);
 303                 }
 304                 else error("Failed to open pidfile '%s'.", pidfile);
 305         }
 306
 307         if(user && *user) {
 308                 if(become_user(user, (*access_fd)?*access_fd:-1, output_fd, error_fd, pidfd) != 0) {
 309                         error("Cannot become user '%s'. Continuing as we are.", user);
 310                 }
 311                 else info("Successfully became user '%s'.", user);
 312         }
 313
 314         if(pidfd != -1) {
 315                 close(pidfd);
 316                 pidfd = -1;
 317         }
 318
 319         return(0);
 320 }