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/*
* SCCS: @(#)eaccess.c 1.12 (99/04/21)
*
* UniSoft Ltd., London, England
*
* (C) Copyright 1992 X/Open Company Limited
*
* All rights reserved. No part of this source code may be reproduced,
* stored in a retrieval system, or transmitted, in any form or by any
* means, electronic, mechanical, photocopying, recording or otherwise,
* except as stated in the end-user licence agreement, without the prior
* permission of the copyright owners.
*
* X/Open and the 'X' symbol are trademarks of X/Open Company Limited in
* the UK and other countries.
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
/************************************************************************
SCCS: @(#)eaccess.c 1.12 99/04/21 TETware release 3.3
NAME: eaccess.c
PRODUCT: TETware
AUTHOR: Andrew Dingwall, UniSoft Ltd.
DATE CREATED: June 1992
DESCRIPTION:
function to check access permissions wrt effective user and group IDs
MODIFICATIONS:
Andrew Dingwall, UniSoft Ltd., January 1994
use S_ISDIR instead of S_IFMT for strict posix conformance
Geoff Clare, UniSoft Ltd., August 1996
Missing <unistd.h>.
Andrew Dingwall, UniSoft Ltd., March 1999
On UNIX systems, check group permissions w.r.t. supplementary
group IDs as well as against the egid.
************************************************************************/
#include <stdio.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
# include <limits.h>
# include <unistd.h>
#include "dtmac.h"
#include "error.h"
#include "ltoa.h"
#include "dtetlib.h"
/* static function declarations */
static int check_grouplist PROTOLIST((struct STAT_ST *, int));
/*
** tet_eaccess() - like access() but checks permissions wrt
** effective user and group IDs
**
** Note: this routine assumes that access and file modes are
** encoded in the traditional way; ie: 4 = read, 2 = write, 1 = exec
** user perms = 0700, group perms = 070, other perms = 07.
**
** Since this routine provides support for the tccd OP_ACCESS
** request (among other things) and thus needs to be able to
** receive a mode argument from another system, it will be necessary
** to implement a machine-independent mode transfer mechanism if
** the above assumption is incorrect for a particular system.
*/
int tet_eaccess(path, mode)
char *path;
register int mode;
{
struct STAT_ST stbuf;
uid_t euid;
int rc, rc2;
/*
** first check for things like non-existent file,
** read-only file system etc.
*/
if (ACCESS(path, mode) < 0) {
if (errno != EACCES)
return(-1);
}
else
if ((mode &= 07) == 0)
return(0);
/*
** here if access() succeeded, or failed because of wrong permissions;
** first get the file permissions
*/
if (STAT(path, &stbuf) < 0)
return(-1);
/*
** check the permissions wrt the euid, the egid and the
** supplementary groups list;
** treating root specially (like the kernel does)
*/
rc = 0;
if ((euid = geteuid()) == 0) {
if (!S_ISDIR(stbuf.st_mode) &&
(stbuf.st_mode & 0111) == 0 && (mode & 01))
rc = -1;
}
else if (stbuf.st_uid == euid) {
if (((stbuf.st_mode >> 6) & mode) != mode)
rc = -1;
}
else if (stbuf.st_gid == getegid()) {
if (((stbuf.st_mode >> 3) & mode) != mode)
rc = -1;
}
else {
rc2 = check_grouplist(&stbuf, mode);
switch (rc2) {
case 2:
break;
case 1:
rc = -1;
break;
case 0:
if ((stbuf.st_mode & mode) != mode)
rc = -1;
break;
case -1:
return(-1);
default:
/* "can't happen" */
fatal(0, "check_grouplist() returned unexpected value",
tet_i2a(rc2));
/* NOTREACHED */
return(-1);
}
}
if (rc < 0)
errno = EACCES;
return(rc);
}
/*
** check_grouplist() - check the requested access mode against
** the process's supplementary grouplist
**
** return 2 if a supplementary group matched and group access is allowed
** 1 if a supplementary group matched but group access is
** not allowed
** 0 if no supplementary groups matched
** -1 on error (with errno set)
*/
static int check_grouplist(stp, mode)
struct STAT_ST *stp;
int mode;
{
int errsave, ngids, ngmax;
gid_t *gidp;
static gid_t *gids = (gid_t *) 0;
static int lgids = 0;
/*
** allocate a buffer to hold the supplementary group list;
** we only evaluate NGROUPS_MAX once because on some systems it
** can be a call to sysconf()
*/
ngmax = (int) NGROUPS_MAX;
if (BUFCHK((char **) &gids, &lgids, ngmax * (int) sizeof *gidp) < 0) {
errno = ENOMEM;
return(-1);
}
/*
** get the supplementary group list from the kernel;
** it probably won't change from one invocation of tet_eaccess() to
** the next, but we get it on each call just to be on the safe side
**/
if ((ngids = getgroups(ngmax, gids)) < 0) {
errsave = errno;
error(errno, "can't get supplementary group list", (char *) 0);
errno = errsave;
return(-1);
}
/*
** check the file's group id against each supplementary group;
** if the groups match, see if the requested access permission(s)
** will be granted
*/
for (gidp = gids; gidp < gids + ngids; gidp++)
if (stp->st_gid == *gidp)
return(((stp->st_mode >> 3) & mode) == mode ? 2 : 1);
return(0);
}
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