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/* uacces.c
Check access to a file by user name.
Copyright (C) 1992 Ian Lance Taylor
This file is part of the Taylor UUCP package.
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
The author of the program may be contacted at ian@airs.com or
c/o Cygnus Support, 48 Grove Street, Somerville, MA 02144.
*/
#include "uucp.h"
#include "uudefs.h"
#include "sysdep.h"
#include <pwd.h>
#include <errno.h>
#if HAVE_GETGRENT
#include <grp.h>
#if GETGRENT_DECLARATION_OK
#ifndef getgrent
extern struct group *getgrent ();
#endif
#endif
#endif /* HAVE_GETGRENT */
#if GETPWNAM_DECLARATION_OK
#ifndef getpwnam
extern struct passwd *getpwnam ();
#endif
#endif
/* Do access(2) on a stat structure, except that the user name is
provided. If the user name in zuser is NULL, require the file to
be accessible to the world. Return TRUE if access is permitted,
FALSE otherwise. This does not log an error message. */
boolean
fsuser_access (q, imode, zuser)
const struct stat *q;
int imode;
const char *zuser;
{
static char *zuser_hold;
static uid_t iuid_hold;
static gid_t igid_hold;
static int cgroups_hold;
static gid_t *paigroups_hold;
int ir, iw, ix, iand;
if (imode == F_OK)
return TRUE;
if (zuser != NULL)
{
/* We keep static variables around for the last user we did, to
avoid looking up a user multiple times. */
if (zuser_hold == NULL || strcmp (zuser_hold, zuser) != 0)
{
struct passwd *qpwd;
if (zuser_hold != NULL)
{
ubuffree (zuser_hold);
zuser_hold = NULL;
cgroups_hold = 0;
xfree ((pointer) paigroups_hold);
paigroups_hold = NULL;
}
qpwd = getpwnam ((char *) zuser);
if (qpwd == NULL)
{
/* Check this as a remote request. */
zuser = NULL;
}
else
{
#if HAVE_GETGRENT
struct group *qg;
#endif
zuser_hold = zbufcpy (zuser);
iuid_hold = qpwd->pw_uid;
igid_hold = qpwd->pw_gid;
#if HAVE_GETGRENT
/* Get the list of groups for this user. This is
definitely more appropriate for BSD than for System
V. It may just be a waste of time, and perhaps it
should be configurable. */
setgrent ();
while ((qg = getgrent ()) != NULL)
{
const char **pz;
if (qg->gr_gid == igid_hold)
continue;
for (pz = (const char **) qg->gr_mem; *pz != NULL; pz++)
{
if ((*pz)[0] == *zuser
&& strcmp (*pz, zuser) == 0)
{
paigroups_hold = ((gid_t *)
(xrealloc
((pointer) paigroups_hold,
((cgroups_hold + 1)
* sizeof (gid_t)))));
paigroups_hold[cgroups_hold] = qg->gr_gid;
++cgroups_hold;
break;
}
}
}
endgrent ();
#endif
}
}
}
/* Now do the actual access check. */
if (zuser != NULL)
{
/* The superuser can do anything. */
if (iuid_hold == 0)
return TRUE;
/* If this is the uid we're running under, there's no point to
checking access further, because when we actually try the
operation the system will do the checking for us. */
if (iuid_hold == geteuid ())
return TRUE;
}
ir = S_IROTH;
iw = S_IWOTH;
ix = S_IXOTH;
if (zuser != NULL)
{
if (iuid_hold == q->st_uid)
{
ir = S_IRUSR;
iw = S_IWUSR;
ix = S_IXUSR;
}
else
{
boolean fgroup;
fgroup = FALSE;
if (igid_hold == q->st_gid)
fgroup = TRUE;
else
{
int i;
for (i = 0; i < cgroups_hold; i++)
{
if (paigroups_hold[i] == q->st_gid)
{
fgroup = TRUE;
break;
}
}
}
if (fgroup)
{
ir = S_IRGRP;
iw = S_IWGRP;
ix = S_IXGRP;
}
}
}
iand = 0;
if ((imode & R_OK) != 0)
iand |= ir;
if ((imode & W_OK) != 0)
iand |= iw;
if ((imode & X_OK) != 0)
iand |= ix;
return (q->st_mode & iand) == iand;
}
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