security/prelude-lml/files/run-prelude-lml.c

   1 #define PRELUDE_LML_USER "@PRELUDE_USER@"
   2 #define PRELUDE_LML_PATH "@PREFIX@/bin/prelude-lml"
   3
   4 #include <unistd.h>
   5 #include <string.h>
   6 #include <stdio.h>
   7 #include <errno.h>
   8 #include <stdlib.h>
   9 #include <sys/wait.h>
  10 #include <pwd.h>
  11 #include <syslog.h>
  12
  13 #define MAX_ARGS 40
  14 #ifndef         TRUE
  15 #define         TRUE                            1
  16 #endif                          /* TRUE */
  17
  18 #ifndef         FALSE
  19 #define         FALSE                           0
  20 #endif                          /* FALSE */
  21
  22
  23 void error_sys(char *str)
  24
  25 {
  26     /* Output error message to syslog */
  27     char msg[1024];
  28     snprintf(msg, sizeof(msg), "run-prelude-lml : %s : %s", str, strerror(errno));
  29     syslog(LOG_ALERT, msg);
  30
  31 }
  32
  33
  34 int obtainUIDandGID(const char *name, uid_t *pw_uid, gid_t *pw_gid)
  35 {
  36     /* Obtain UID and GID from passwd entry identified by name */
  37     struct passwd *pw_entry;
  38     char msg[100];
  39
  40     if ((pw_entry = getpwnam(name)) == NULL)
  41     {
  42         snprintf(msg, sizeof(msg), "failed to get password entry for %s", name);
  43         error_sys(msg);
  44         return FALSE;
  45     }
  46     else
  47     {
  48         *pw_uid = pw_entry->pw_uid;
  49         *pw_gid = pw_entry->pw_gid;
  50         return TRUE;
  51
  52     }
  53 }
  54
  55
  56 int main (int argc, char **argv )
  57
  58 {
  59
  60     pid_t pid;
  61     uid_t UID;
  62     gid_t GID;
  63     pid_t pidwait;
  64     int waitstat;
  65     int s;
  66     int max_fd;
  67
  68     /* Sanity check */
  69     if (argc > MAX_ARGS)
  70     {
  71         error_sys("arg buffer too small");
  72         exit(-1);
  73     }
  74
  75     if (geteuid() != 0)
  76     {
  77         error_sys("must be called by root");
  78         exit(-1);
  79     }
  80
  81     /* fork child that will become prelude-lml */
  82     if ((pid = fork()) < 0)
  83
  84         error_sys("fork error");
  85
  86     else
  87
  88     {
  89
  90         if (pid == 0)
  91
  92         {
  93
  94             /* We're the child */
  95             char *args[MAX_ARGS];
  96             unsigned int i;
  97
  98             /* Become session leader */
  99             setsid();
 100
 101             /* Change working directory to root directory.
 102                The current working directory could be a mounted
 103                filesystem; if the daemon stays on a mounted
 104                filesystem it could prevent the filesystem from
 105                being umounted. */
 106             chdir("/");
 107
 108             /* Clear out file creation mask */
 109             umask(0);
 110
 111             /* Close unneeded file descriptors */
 112             max_fd = (int) sysconf(_SC_OPEN_MAX);
 113             if (max_fd == -1)
 114                 max_fd = getdtablesize();
 115             for (s = 3; s < max_fd; s++)
 116                 (void) close(s);
 117
 118             if (!obtainUIDandGID(PRELUDE_LML_USER, &UID, &GID))
 119                 exit(-1);
 120
 121             /* Drop privileges immediately */
 122             if (setgid(GID) < 0)
 123             {
 124                 /* It is VERY important to check return
 125                    value and not continue if setgid fails
 126                 */
 127                 error_sys ("setgid failed");
 128                 exit (-1);
 129             }
 130
 131             if (setuid(UID) < 0)
 132             {
 133                 /* It is VERY important to check return
 134                    value and not continue if setuid fails
 135                 */
 136                 error_sys ("setuid failed");
 137                 exit (-1);
 138             }
 139
 140             /* Build calling argv */
 141             args[0] = PRELUDE_LML_PATH;
 142             for (i=1;i<argc;i++)
 143             {
 144                 args[i] = argv[i];
 145             }
 146             args[i++] = NULL;
 147
 148             /* Finally transform self into prelude-lml */
 149             if (execvp(PRELUDE_LML_PATH, args) < 0)
 150                 error_sys("execve error");
 151             else
 152                 ; /* avoid if-then ambiguity */
 153         }
 154
 155         else
 156
 157         {
 158             /* We're the parent
 159                Terminate
 160             */
 161             exit(0);
 162         }
 163
 164     }
 165
 166 }