minix/lib/libpuffs/protect.c

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/* Created (MFS based):
* June 2011 (Evgeniy Ivanov)
*/
#include "fs.h"
#include <minix/vfsif.h>
#include "puffs.h"
#include "puffs_priv.h"
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static int in_group(gid_t grp);
/*===========================================================================*
* fs_chmod *
*===========================================================================*/
int fs_chmod(void)
{
/* Perform the chmod(name, mode) system call. */
struct puffs_node *pn;
mode_t mode;
struct vattr va;
PUFFS_MAKECRED(pcr, &global_kcred);
if (global_pu->pu_ops.puffs_node_setattr == NULL)
return(EINVAL);
mode = (mode_t) fs_m_in.REQ_MODE;
if ((pn = puffs_pn_nodewalk(global_pu, 0, &fs_m_in.REQ_INODE_NR)) == NULL)
return(EINVAL);
puffs_vattr_null(&va);
/* Clear setgid bit if file is not in caller's grp */
va.va_mode = (pn->pn_va.va_mode & ~ALL_MODES) | (mode & ALL_MODES);
va.va_ctime = clock_timespec();
if (global_pu->pu_ops.puffs_node_setattr(global_pu, pn, &va, pcr) != 0)
return(EINVAL);
/* Return full new mode to caller. */
fs_m_out.RES_MODE = pn->pn_va.va_mode;
return(OK);
}
/*===========================================================================*
* fs_chown *
*===========================================================================*/
int fs_chown(void)
{
struct puffs_node *pn;
struct vattr va;
PUFFS_MAKECRED(pcr, &global_kcred);
if ((pn = puffs_pn_nodewalk(global_pu, 0, &fs_m_in.REQ_INODE_NR)) == NULL)
return(EINVAL);
/* Not permitted to change the owner of a file on a read-only file sys. */
if (!is_readonly_fs) {
puffs_vattr_null(&va);
va.va_uid = fs_m_in.REQ_UID;
va.va_gid = fs_m_in.REQ_GID;
va.va_mode = pn->pn_va.va_mode & ~(I_SET_UID_BIT | I_SET_GID_BIT);
va.va_ctime = clock_timespec();
if (global_pu->pu_ops.puffs_node_setattr(global_pu, pn, &va, pcr) != 0)
return(EINVAL);
}
/* Update caller on current mode, as it may have changed. */
fs_m_out.RES_MODE = pn->pn_va.va_mode;
return(OK);
}
/*===========================================================================*
* forbidden *
*===========================================================================*/
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int forbidden(register struct puffs_node *pn, mode_t access_desired)
{
/* Given a pointer to an pnode, 'pn', 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 mode_t bits, perm_bits;
int r, shift;
/* Isolate the relevant rwx bits from the mode. */
bits = pn->pn_va.va_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 == pn->pn_va.va_uid) shift = 6; /* owner */
else if (caller_gid == pn->pn_va.va_gid) shift = 3; /* group */
else if (in_group(pn->pn_va.va_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 = is_readonly_fs ? EROFS : OK;
}
}
return(r);
}
/*===========================================================================*
* in_group *
*===========================================================================*/
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static int in_group(gid_t grp)
{
int i;
for(i = 0; i < credentials.vu_ngroups; i++)
if (credentials.vu_sgroups[i] == grp)
return(OK);
return(EINVAL);
}