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

   1 /*      $NetBSD$        */
   2
   3 /*++
   4 /* NAME
   5 /*      open_as 3
   6 /* SUMMARY
   7 /*      open file as user
   8 /* SYNOPSIS
   9 /*      #include <fcntl.h>
  10 /*      #include <open_as.h>
  11 /*
  12 /*      int     open_as(path, flags, mode, euid, egid)
  13 /*      const char *path;
  14 /*      int     mode;
  15 /*      uid_t   euid;
  16 /*      gid_t   egid;
  17 /* DESCRIPTION
  18 /*      open_as() opens the named \fIpath\fR with the named \fIflags\fR
  19 /*      and \fImode\fR, and with the effective rights specified by \fIeuid\fR
  20 /*      and \fIegid\fR.  A -1 result means the open failed.
  21 /* DIAGNOSTICS
  22 /*      Fatal error: no permission to change privilege level.
  23 /* SEE ALSO
  24 /*      set_eugid(3) switch effective rights
  25 /* LICENSE
  26 /* .ad
  27 /* .fi
  28 /*      The Secure Mailer license must be distributed with this software.
  29 /* AUTHOR(S)
  30 /*      Wietse Venema
  31 /*      IBM T.J. Watson Research
  32 /*      P.O. Box 704
  33 /*      Yorktown Heights, NY 10598, USA
  34 /*--*/
  35
  36 /* System library. */
  37
  38 #include <sys_defs.h>
  39 #include <fcntl.h>
  40 #include <unistd.h>
  41
  42 /* Utility library. */
  43
  44 #include "msg.h"
  45 #include "set_eugid.h"
  46 #include "open_as.h"
  47
  48 /* open_as - open file as user */
  49
  50 int     open_as(const char *path, int flags, int mode, uid_t euid, gid_t egid)
  51 {
  52     uid_t   saved_euid = geteuid();
  53     gid_t   saved_egid = getegid();
  54     int     fd;
  55
  56     /*
  57      * Switch to the target user privileges.
  58      */
  59     set_eugid(euid, egid);
  60
  61     /*
  62      * Open that file.
  63      */
  64     fd = open(path, flags, mode);
  65
  66     /*
  67      * Restore saved privileges.
  68      */
  69     set_eugid(saved_euid, saved_egid);
  70
  71     return (fd);
  72 }