external/ibm-public/postfix/dist/src/util/clean_env.c

   1 /*      $NetBSD$        */
   2
   3 /*++
   4 /* NAME
   5 /*      clean_env 3
   6 /* SUMMARY
   7 /*      clean up the environment
   8 /* SYNOPSIS
   9 /*      #include <clean_env.h>
  10 /*
  11 /*      void    clean_env(preserve_list)
  12 /*      const char **preserve_list;
  13 /* DESCRIPTION
  14 /*      clean_env() reduces the process environment to the bare minimum.
  15 /*      The function takes a null-terminated list of arguments.
  16 /*      Each argument specifies the name of an environment variable
  17 /*      that should be preserved, or specifies a name=value that should
  18 /*      be entered into the new environment.
  19 /* DIAGNOSTICS
  20 /*      Fatal error: out of memory.
  21 /* SEE ALSO
  22 /*      safe_getenv(3), guarded getenv()
  23 /* LICENSE
  24 /* .ad
  25 /* .fi
  26 /*      The Secure Mailer license must be distributed with this software.
  27 /* AUTHOR(S)
  28 /*      Wietse Venema
  29 /*      IBM T.J. Watson Research
  30 /*      P.O. Box 704
  31 /*      Yorktown Heights, NY 10598, USA
  32 /*--*/
  33
  34 /* System library. */
  35
  36 #include <sys_defs.h>
  37 #include <stdlib.h>
  38 #include <unistd.h>
  39 #include <string.h>
  40
  41 /* Utility library. */
  42
  43 #include <msg.h>
  44 #include <argv.h>
  45 #include <safe.h>
  46 #include <clean_env.h>
  47
  48 /* clean_env - clean up the environment */
  49
  50 void    clean_env(char **preserve_list)
  51 {
  52     extern char **environ;
  53     ARGV   *save_list;
  54     char   *value;
  55     char  **cpp;
  56     char   *eq;
  57
  58     /*
  59      * Preserve or specify selected environment variables.
  60      */
  61 #define STRING_AND_LENGTH(x, y) (x), (ssize_t) (y)
  62
  63     save_list = argv_alloc(10);
  64     for (cpp = preserve_list; *cpp; cpp++)
  65         if ((eq = strchr(*cpp, '=')) != 0)
  66             argv_addn(save_list, STRING_AND_LENGTH(*cpp, eq - *cpp),
  67                       STRING_AND_LENGTH(eq + 1, strlen(eq + 1)), (char *) 0);
  68         else if ((value = safe_getenv(*cpp)) != 0)
  69             argv_add(save_list, *cpp, value, (char *) 0);
  70
  71     /*
  72      * Truncate the process environment, if available. On some systems
  73      * (Ultrix!), environ can be a null pointer.
  74      */
  75     if (environ)
  76         environ[0] = 0;
  77
  78     /*
  79      * Restore preserved environment variables.
  80      */
  81     for (cpp = save_list->argv; *cpp; cpp += 2)
  82         if (setenv(cpp[0], cpp[1], 1))
  83             msg_fatal("setenv(%s, %s): %m", cpp[0], cpp[1]);
  84
  85     /*
  86      * Cleanup.
  87      */
  88     argv_free(save_list);
  89 }