minix/servers/vfs/protect.c
2007-08-07 12:52:47 +00:00

275 lines
7.1 KiB
C

/* This file deals with protection in the file system. It contains the code
* for four system calls that relate to protection.
*
* The entry points into this file are
* do_chmod: perform the CHMOD and FCHMOD system calls
* do_chown: perform the CHOWN and FCHOWN system calls
* do_umask: perform the UMASK system call
* do_access: perform the ACCESS system call
*
* Changes for VFS:
* Jul 2006 (Balazs Gerofi)
*/
#include "fs.h"
#include <unistd.h>
#include <minix/callnr.h>
#include "file.h"
#include "fproc.h"
#include "param.h"
#include <minix/vfsif.h>
#include "vnode.h"
#include "vmnt.h"
/*===========================================================================*
* do_chmod *
*===========================================================================*/
PUBLIC int do_chmod()
{
struct filp *flp;
struct vnode *vp;
int r;
uid_t uid;
gid_t gid;
mode_t new_mode;
if (call_nr == CHMOD) {
/* Perform the chmod(name, mode) system call. */
if (fetch_name(m_in.name, m_in.name_length, M3) != OK) return(err_code);
/* Request lookup */
r = lookup_vp(0 /*flags*/, 0 /*!use_realuid*/, &vp);
if (r != OK) return r;
}
else if (call_nr == FCHMOD) {
if (!(flp = get_filp(m_in.m3_i1))) return err_code;
vp= flp->filp_vno;
dup_vnode(vp);
}
else panic(__FILE__, "do_chmod called with strange call_nr", call_nr);
uid= fp->fp_effuid;
gid= fp->fp_effgid;
/* Only the owner or the super_user may change the mode of a file.
* No one may change the mode of a file on a read-only file system.
*/
if (vp->v_uid != uid && uid != SU_UID)
r = EPERM;
else
r = read_only(vp);
/* If error, return inode. */
if (r != OK) {
put_vnode(vp);
return(r);
}
/* Now make the change. Clear setgid bit if file is not in caller's grp */
if (uid != SU_UID && vp->v_gid != gid)
m_in.mode &= ~I_SET_GID_BIT;
/* Issue request */
r = req_chmod(vp->v_fs_e, vp->v_inode_nr, m_in.mode, &new_mode);
if (r == OK)
vp->v_mode = new_mode;
put_vnode(vp);
return OK;
}
/*===========================================================================*
* do_chown *
*===========================================================================*/
PUBLIC int do_chown()
{
int inode_nr;
int fs_e;
struct filp *flp;
struct vnode *vp;
int r;
uid_t uid;
gid_t gid;
mode_t new_mode;
if (call_nr == CHOWN) {
/* Perform the chmod(name, mode) system call. */
if (fetch_name(m_in.name1, m_in.name1_length, M1) != OK) return(err_code);
/* Request lookup */
r = lookup_vp(0 /*flags*/, 0 /*!use_realuid*/, &vp);
if (r != OK) return r;
}
else if (call_nr == FCHOWN) {
if (!(flp = get_filp(m_in.m1_i1))) return err_code;
vp= flp->filp_vno;
dup_vnode(vp);
}
else panic(__FILE__, "do_chmod called with strange call_nr", call_nr);
uid= fp->fp_effuid;
gid= fp->fp_effgid;
r= OK;
if (uid == SU_UID) {
/* The super user can do anything. */
} else {
/* Regular users can only change groups of their own files. */
if (vp->v_uid != uid)
r = EPERM; /* File does not belong to the caller */
if (vp->v_uid != m_in.owner)
r = EPERM; /* no giving away */
if (gid != m_in.group)
r = EPERM; /* only change to the current gid */
}
if (r != OK) {
put_vnode(vp);
return r;
}
/* Issue request */
r = req_chown(vp->v_fs_e, vp->v_inode_nr, m_in.owner, m_in.group, &new_mode);
if(r == OK) {
vp->v_uid = m_in.owner;
vp->v_gid = m_in.group;
vp->v_mode = new_mode;
}
put_vnode(vp);
return r;
}
/*===========================================================================*
* do_umask *
*===========================================================================*/
PUBLIC int do_umask()
{
/* Perform the umask(co_mode) system call. */
register mode_t r;
r = ~fp->fp_umask; /* set 'r' to complement of old mask */
fp->fp_umask = ~(m_in.co_mode & RWX_MODES);
return(r); /* return complement of old mask */
}
/*===========================================================================*
* do_access *
*===========================================================================*/
PUBLIC int do_access()
{
/* Perform the access(name, mode) system call. */
int r;
struct vnode *vp;
/* First check to see if the mode is correct. */
if ( (m_in.mode & ~(R_OK | W_OK | X_OK)) != 0 && m_in.mode != F_OK)
return(EINVAL);
if (fetch_name(m_in.name, m_in.name_length, M3) != OK) return(err_code);
/* Request lookup */
r = lookup_vp(0 /*flags*/, TRUE /*use_realuid*/, &vp);
if (r != OK) return r;
r= forbidden(vp, m_in.mode, 1 /*use_realuid*/);
put_vnode(vp);
return r;
}
/*===========================================================================*
* forbidden *
*===========================================================================*/
PUBLIC int forbidden(struct vnode *vp, mode_t access_desired, int use_realuid)
{
/* Given a pointer to an inode, 'rip', and the access desired, determine
* if the access is allowed, and if not why not. The routine looks up the
* caller's uid in the 'fproc' table. If access is allowed, OK is returned
* if it is forbidden, EACCES is returned.
*/
register struct super_block *sp;
register mode_t bits, perm_bits;
uid_t uid;
gid_t gid;
int r, shift, type;
if (vp->v_uid == (uid_t)-1 || vp->v_gid == (gid_t)-1)
{
printf("forbidden: bad uid/gid in vnode: inode %d on dev 0x%x\n",
vp->v_inode_nr, vp->v_dev);
printf("forbidden: last allocated at %s, %d\n", vp->v_file, vp->v_line);
return EACCES;
}
/* Isolate the relevant rwx bits from the mode. */
bits = vp->v_mode;
if (use_realuid)
{
uid= fp->fp_realuid;
gid= fp->fp_realgid;
}
else
{
uid= fp->fp_effuid;
gid= fp->fp_effgid;
}
if (uid == SU_UID) {
/* Grant read and write permission. Grant search permission for
* directories. Grant execute permission (for non-directories) if
* and only if one of the 'X' bits is set.
*/
if ( (bits & I_TYPE) == I_DIRECTORY ||
bits & ((X_BIT << 6) | (X_BIT << 3) | X_BIT))
perm_bits = R_BIT | W_BIT | X_BIT;
else
perm_bits = R_BIT | W_BIT;
} else {
if (uid == vp->v_uid) shift = 6; /* owner */
else if (gid == vp->v_gid ) shift = 3; /* group */
else shift = 0; /* other */
perm_bits = (bits >> shift) & (R_BIT | W_BIT | X_BIT);
}
/* If access desired is not a subset of what is allowed, it is refused. */
r = OK;
if ((perm_bits | access_desired) != perm_bits) {
r = EACCES;
}
/* Check to see if someone is trying to write on a file system that is
* mounted read-only.
*/
if (r == OK)
if (access_desired & W_BIT)
r = read_only(vp);
return(r);
}
/*===========================================================================*
* read_only *
*===========================================================================*/
PUBLIC int read_only(vp)
struct vnode *vp; /* ptr to inode whose file sys is to be cked */
{
/* Check to see if the file system on which the inode 'ip' resides is mounted
* read only. If so, return EROFS, else return OK.
*/
register struct vmnt *mp;
mp = vp->v_vmnt;
return(mp->m_flags ? EROFS : OK);
}