sysdeps/unix/sysv/linux/recvmsg.c

   1 /* Copyright (C) 1998 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include <sys/socket.h>
  20 #include <errno.h>
  21 #include <string.h>
  22
  23 #include <asm/posix_types.h>
  24
  25 /* The kernel expects this structure in SCM_CREDS messages.
  26  * Note: sizeof(struct __kernel_ucred) <= sizeof(struct cmsgcred) must hold.
  27  */
  28 struct __kernel_ucred
  29 {
  30   __kernel_pid_t pid;
  31   __kernel_uid_t uid;
  32   __kernel_gid_t gid;
  33 };
  34
  35 extern int __recvmsg (int, struct msghdr *, int);
  36
  37 int
  38 recvmsg (fd, message, flags)
  39      int fd;
  40      struct msghdr *message;
  41      int flags;
  42 {
  43   struct cmsghdr *cm;
  44   int ret;
  45   int found_creds = 0;
  46
  47   /* Must check for space first. */
  48   cm = CMSG_FIRSTHDR (message);
  49   while (cm)
  50     {
  51       if (cm->cmsg_type == SCM_CREDS)
  52         {
  53           if (cm->cmsg_len < CMSG_SPACE (sizeof (struct cmsgcred)))
  54             {
  55               __set_errno (EINVAL);
  56               return -1;
  57             }
  58           found_creds = 1;
  59         }
  60       cm = CMSG_NXTHDR (message, cm);
  61     }
  62
  63
  64   ret = __recvmsg (fd, message, flags);
  65
  66   if (ret == -1)
  67     return ret;
  68
  69   /* Postprocess the message control block for SCM_CREDS. */
  70   cm = CMSG_FIRSTHDR (message);
  71   if (found_creds)
  72     while (cm)
  73       {
  74         if (cm->cmsg_type == SCM_CREDS)
  75           {
  76             struct cmsgcred *c = (struct cmsgcred *) CMSG_DATA (cm);
  77             struct __kernel_ucred u;
  78             int i;
  79             memcpy (&u, CMSG_DATA (cm), sizeof (struct __kernel_ucred));
  80
  81             c->cmcred_pid = u.pid;
  82             c->cmcred_uid = u.uid;
  83             c->cmcred_gid = u.gid;
  84
  85             c->cmcred_euid = -1;
  86             c->cmcred_ngroups = 0;
  87             for (i = 0; i < CMGROUP_MAX; i++)
  88               c->cmcred_groups[i] = -1;
  89           }
  90         cm = CMSG_NXTHDR (message, cm);
  91       }
  92   return ret;
  93 }