minix/servers/ext2/protect.c

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/* Created (MFS based):
* February 2010 (Evgeniy Ivanov)
*/
#include "fs.h"
#include "inode.h"
#include "super.h"
#include <minix/vfsif.h>
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static int in_group(gid_t grp);
/*===========================================================================*
* fs_chmod *
*===========================================================================*/
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int fs_chmod()
{
/* Perform the chmod(name, mode) system call. */
register struct inode *rip;
pmode_t mode;
mode = (pmode_t) fs_m_in.REQ_MODE;
/* Temporarily open the file. */
if( (rip = get_inode(fs_dev, (pino_t) fs_m_in.REQ_INODE_NR)) == NULL)
return(EINVAL);
/* Now make the change. Clear setgid bit if file is not in caller's grp */
rip->i_mode = (rip->i_mode & ~ALL_MODES) | (mode & ALL_MODES);
rip->i_update |= CTIME;
rip->i_dirt = IN_DIRTY;
/* Return full new mode to caller. */
fs_m_out.RES_MODE = rip->i_mode;
put_inode(rip);
return(OK);
}
/*===========================================================================*
* fs_chown *
*===========================================================================*/
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int fs_chown()
{
register struct inode *rip;
register int r;
/* Temporarily open the file. */
if( (rip = get_inode(fs_dev, (pino_t) fs_m_in.REQ_INODE_NR)) == NULL)
return(EINVAL);
/* Not permitted to change the owner of a file on a read-only file sys. */
r = read_only(rip);
if (r == OK) {
rip->i_uid = fs_m_in.REQ_UID;
rip->i_gid = fs_m_in.REQ_GID;
rip->i_mode &= ~(I_SET_UID_BIT | I_SET_GID_BIT);
rip->i_update |= CTIME;
rip->i_dirt = IN_DIRTY;
}
/* Update caller on current mode, as it may have changed. */
fs_m_out.RES_MODE = rip->i_mode;
put_inode(rip);
return(r);
}
/*===========================================================================*
* forbidden *
*===========================================================================*/
int forbidden(register struct inode *rip, pmode_t access_desired)
{
/* 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 inode *old_rip = rip;
register pmode_t bits, perm_bits;
int r, shift;
/* Isolate the relevant rwx bits from the mode. */
bits = rip->i_mode;
if (caller_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 (caller_uid == rip->i_uid) shift = 6; /* owner */
else if (caller_gid == rip->i_gid) shift = 3; /* group */
else if (in_group(rip->i_gid) == OK) shift = 3; /* other groups */
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(rip);
}
}
if (rip != old_rip) put_inode(rip);
return(r);
}
/*===========================================================================*
* in_group *
*===========================================================================*/
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static int in_group(gid_t grp)
{
int i;
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if (credentials.vu_ngroups > NGROUPS_MAX)
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return(EINVAL);
for (i = 0; i < credentials.vu_ngroups; i++)
if (credentials.vu_sgroups[i] == grp)
return(OK);
return(EINVAL);
}
/*===========================================================================*
* read_only *
*===========================================================================*/
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int read_only(ip)
struct inode *ip; /* 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 super_block *sp;
sp = ip->i_sp;
return(sp->s_rd_only ? EROFS : OK);
}