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f-stack/freebsd/kern/subr_acl_posix1e.c

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/*-
* Copyright (c) 1999-2006 Robert N. M. Watson
* All rights reserved.
*
* This software was developed by Robert Watson for the TrustedBSD Project.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* Developed by the TrustedBSD Project.
*
* ACL support routines specific to POSIX.1e access control lists. These are
* utility routines for code common across file systems implementing POSIX.1e
* ACLs.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/module.h>
#include <sys/systm.h>
#include <sys/mount.h>
#include <sys/priv.h>
#include <sys/vnode.h>
#include <sys/errno.h>
#include <sys/stat.h>
#include <sys/acl.h>
/*
* Implement a version of vaccess() that understands POSIX.1e ACL semantics;
* the access ACL has already been prepared for evaluation by the file system
* and is passed via 'uid', 'gid', and 'acl'. Return 0 on success, else an
* errno value.
*/
int
vaccess_acl_posix1e(enum vtype type, uid_t file_uid, gid_t file_gid,
struct acl *acl, accmode_t accmode, struct ucred *cred, int *privused)
{
struct acl_entry *acl_other, *acl_mask;
accmode_t dac_granted;
accmode_t priv_granted;
accmode_t acl_mask_granted;
int group_matched, i;
KASSERT((accmode & ~(VEXEC | VWRITE | VREAD | VADMIN | VAPPEND)) == 0,
("invalid bit in accmode"));
KASSERT((accmode & VAPPEND) == 0 || (accmode & VWRITE),
("VAPPEND without VWRITE"));
/*
* Look for a normal, non-privileged way to access the file/directory
* as requested. If it exists, go with that. Otherwise, attempt to
* use privileges granted via priv_granted. In some cases, which
* privileges to use may be ambiguous due to "best match", in which
* case fall back on first match for the time being.
*/
if (privused != NULL)
*privused = 0;
/*
* Determine privileges now, but don't apply until we've found a DAC
* entry that matches but has failed to allow access.
*
* XXXRW: Ideally, we'd determine the privileges required before
* asking for them.
*/
priv_granted = 0;
if (type == VDIR) {
if ((accmode & VEXEC) && !priv_check_cred(cred,
PRIV_VFS_LOOKUP, 0))
priv_granted |= VEXEC;
} else {
/*
* Ensure that at least one execute bit is on. Otherwise,
* a privileged user will always succeed, and we don't want
* this to happen unless the file really is executable.
*/
if ((accmode & VEXEC) && (acl_posix1e_acl_to_mode(acl) &
(S_IXUSR | S_IXGRP | S_IXOTH)) != 0 &&
!priv_check_cred(cred, PRIV_VFS_EXEC, 0))
priv_granted |= VEXEC;
}
if ((accmode & VREAD) && !priv_check_cred(cred, PRIV_VFS_READ, 0))
priv_granted |= VREAD;
if (((accmode & VWRITE) || (accmode & VAPPEND)) &&
!priv_check_cred(cred, PRIV_VFS_WRITE, 0))
priv_granted |= (VWRITE | VAPPEND);
if ((accmode & VADMIN) && !priv_check_cred(cred, PRIV_VFS_ADMIN, 0))
priv_granted |= VADMIN;
/*
* The owner matches if the effective uid associated with the
* credential matches that of the ACL_USER_OBJ entry. While we're
* doing the first scan, also cache the location of the ACL_MASK and
* ACL_OTHER entries, preventing some future iterations.
*/
acl_mask = acl_other = NULL;
for (i = 0; i < acl->acl_cnt; i++) {
switch (acl->acl_entry[i].ae_tag) {
case ACL_USER_OBJ:
if (file_uid != cred->cr_uid)
break;
dac_granted = 0;
dac_granted |= VADMIN;
if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
dac_granted |= VEXEC;
if (acl->acl_entry[i].ae_perm & ACL_READ)
dac_granted |= VREAD;
if (acl->acl_entry[i].ae_perm & ACL_WRITE)
dac_granted |= (VWRITE | VAPPEND);
if ((accmode & dac_granted) == accmode)
return (0);
/*
* XXXRW: Do privilege lookup here.
*/
if ((accmode & (dac_granted | priv_granted)) ==
accmode) {
if (privused != NULL)
*privused = 1;
return (0);
}
goto error;
case ACL_MASK:
acl_mask = &acl->acl_entry[i];
break;
case ACL_OTHER:
acl_other = &acl->acl_entry[i];
break;
default:
break;
}
}
/*
* An ACL_OTHER entry should always exist in a valid access ACL. If
* it doesn't, then generate a serious failure. For now, this means
* a debugging message and EPERM, but in the future should probably
* be a panic.
*/
if (acl_other == NULL) {
/*
* XXX This should never happen
*/
printf("vaccess_acl_posix1e: ACL_OTHER missing\n");
return (EPERM);
}
/*
* Checks against ACL_USER, ACL_GROUP_OBJ, and ACL_GROUP fields are
* masked by an ACL_MASK entry, if any. As such, first identify the
* ACL_MASK field, then iterate through identifying potential user
* matches, then group matches. If there is no ACL_MASK, assume that
* the mask allows all requests to succeed.
*/
if (acl_mask != NULL) {
acl_mask_granted = 0;
if (acl_mask->ae_perm & ACL_EXECUTE)
acl_mask_granted |= VEXEC;
if (acl_mask->ae_perm & ACL_READ)
acl_mask_granted |= VREAD;
if (acl_mask->ae_perm & ACL_WRITE)
acl_mask_granted |= (VWRITE | VAPPEND);
} else
acl_mask_granted = VEXEC | VREAD | VWRITE | VAPPEND;
/*
* Check ACL_USER ACL entries. There will either be one or no
* matches; if there is one, we accept or rejected based on the
* match; otherwise, we continue on to groups.
*/
for (i = 0; i < acl->acl_cnt; i++) {
switch (acl->acl_entry[i].ae_tag) {
case ACL_USER:
if (acl->acl_entry[i].ae_id != cred->cr_uid)
break;
dac_granted = 0;
if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
dac_granted |= VEXEC;
if (acl->acl_entry[i].ae_perm & ACL_READ)
dac_granted |= VREAD;
if (acl->acl_entry[i].ae_perm & ACL_WRITE)
dac_granted |= (VWRITE | VAPPEND);
dac_granted &= acl_mask_granted;
if ((accmode & dac_granted) == accmode)
return (0);
/*
* XXXRW: Do privilege lookup here.
*/
if ((accmode & (dac_granted | priv_granted)) !=
accmode)
goto error;
if (privused != NULL)
*privused = 1;
return (0);
}
}
/*
* Group match is best-match, not first-match, so find a "best"
* match. Iterate across, testing each potential group match. Make
* sure we keep track of whether we found a match or not, so that we
* know if we should try again with any available privilege, or if we
* should move on to ACL_OTHER.
*/
group_matched = 0;
for (i = 0; i < acl->acl_cnt; i++) {
switch (acl->acl_entry[i].ae_tag) {
case ACL_GROUP_OBJ:
if (!groupmember(file_gid, cred))
break;
dac_granted = 0;
if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
dac_granted |= VEXEC;
if (acl->acl_entry[i].ae_perm & ACL_READ)
dac_granted |= VREAD;
if (acl->acl_entry[i].ae_perm & ACL_WRITE)
dac_granted |= (VWRITE | VAPPEND);
dac_granted &= acl_mask_granted;
if ((accmode & dac_granted) == accmode)
return (0);
group_matched = 1;
break;
case ACL_GROUP:
if (!groupmember(acl->acl_entry[i].ae_id, cred))
break;
dac_granted = 0;
if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
dac_granted |= VEXEC;
if (acl->acl_entry[i].ae_perm & ACL_READ)
dac_granted |= VREAD;
if (acl->acl_entry[i].ae_perm & ACL_WRITE)
dac_granted |= (VWRITE | VAPPEND);
dac_granted &= acl_mask_granted;
if ((accmode & dac_granted) == accmode)
return (0);
group_matched = 1;
break;
default:
break;
}
}
if (group_matched == 1) {
/*
* There was a match, but it did not grant rights via pure
* DAC. Try again, this time with privilege.
*/
for (i = 0; i < acl->acl_cnt; i++) {
switch (acl->acl_entry[i].ae_tag) {
case ACL_GROUP_OBJ:
if (!groupmember(file_gid, cred))
break;
dac_granted = 0;
if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
dac_granted |= VEXEC;
if (acl->acl_entry[i].ae_perm & ACL_READ)
dac_granted |= VREAD;
if (acl->acl_entry[i].ae_perm & ACL_WRITE)
dac_granted |= (VWRITE | VAPPEND);
dac_granted &= acl_mask_granted;
/*
* XXXRW: Do privilege lookup here.
*/
if ((accmode & (dac_granted | priv_granted))
!= accmode)
break;
if (privused != NULL)
*privused = 1;
return (0);
case ACL_GROUP:
if (!groupmember(acl->acl_entry[i].ae_id,
cred))
break;
dac_granted = 0;
if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
dac_granted |= VEXEC;
if (acl->acl_entry[i].ae_perm & ACL_READ)
dac_granted |= VREAD;
if (acl->acl_entry[i].ae_perm & ACL_WRITE)
dac_granted |= (VWRITE | VAPPEND);
dac_granted &= acl_mask_granted;
/*
* XXXRW: Do privilege lookup here.
*/
if ((accmode & (dac_granted | priv_granted))
!= accmode)
break;
if (privused != NULL)
*privused = 1;
return (0);
default:
break;
}
}
/*
* Even with privilege, group membership was not sufficient.
* Return failure.
*/
goto error;
}
/*
* Fall back on ACL_OTHER. ACL_MASK is not applied to ACL_OTHER.
*/
dac_granted = 0;
if (acl_other->ae_perm & ACL_EXECUTE)
dac_granted |= VEXEC;
if (acl_other->ae_perm & ACL_READ)
dac_granted |= VREAD;
if (acl_other->ae_perm & ACL_WRITE)
dac_granted |= (VWRITE | VAPPEND);
if ((accmode & dac_granted) == accmode)
return (0);
/*
* XXXRW: Do privilege lookup here.
*/
if ((accmode & (dac_granted | priv_granted)) == accmode) {
if (privused != NULL)
*privused = 1;
return (0);
}
error:
return ((accmode & VADMIN) ? EPERM : EACCES);
}
/*
* For the purposes of filesystems maintaining the _OBJ entries in an inode
* with a mode_t field, this routine converts a mode_t entry to an
* acl_perm_t.
*/
acl_perm_t
acl_posix1e_mode_to_perm(acl_tag_t tag, mode_t mode)
{
acl_perm_t perm = 0;
switch(tag) {
case ACL_USER_OBJ:
if (mode & S_IXUSR)
perm |= ACL_EXECUTE;
if (mode & S_IRUSR)
perm |= ACL_READ;
if (mode & S_IWUSR)
perm |= ACL_WRITE;
return (perm);
case ACL_GROUP_OBJ:
if (mode & S_IXGRP)
perm |= ACL_EXECUTE;
if (mode & S_IRGRP)
perm |= ACL_READ;
if (mode & S_IWGRP)
perm |= ACL_WRITE;
return (perm);
case ACL_OTHER:
if (mode & S_IXOTH)
perm |= ACL_EXECUTE;
if (mode & S_IROTH)
perm |= ACL_READ;
if (mode & S_IWOTH)
perm |= ACL_WRITE;
return (perm);
default:
printf("acl_posix1e_mode_to_perm: invalid tag (%d)\n", tag);
return (0);
}
}
/*
* Given inode information (uid, gid, mode), return an acl entry of the
* appropriate type.
*/
struct acl_entry
acl_posix1e_mode_to_entry(acl_tag_t tag, uid_t uid, gid_t gid, mode_t mode)
{
struct acl_entry acl_entry;
acl_entry.ae_tag = tag;
acl_entry.ae_perm = acl_posix1e_mode_to_perm(tag, mode);
acl_entry.ae_entry_type = 0;
acl_entry.ae_flags = 0;
switch(tag) {
case ACL_USER_OBJ:
acl_entry.ae_id = uid;
break;
case ACL_GROUP_OBJ:
acl_entry.ae_id = gid;
break;
case ACL_OTHER:
acl_entry.ae_id = ACL_UNDEFINED_ID;
break;
default:
acl_entry.ae_id = ACL_UNDEFINED_ID;
printf("acl_posix1e_mode_to_entry: invalid tag (%d)\n", tag);
}
return (acl_entry);
}
/*
* Utility function to generate a file mode given appropriate ACL entries.
*/
mode_t
acl_posix1e_perms_to_mode(struct acl_entry *acl_user_obj_entry,
struct acl_entry *acl_group_obj_entry, struct acl_entry *acl_other_entry)
{
mode_t mode;
mode = 0;
if (acl_user_obj_entry->ae_perm & ACL_EXECUTE)
mode |= S_IXUSR;
if (acl_user_obj_entry->ae_perm & ACL_READ)
mode |= S_IRUSR;
if (acl_user_obj_entry->ae_perm & ACL_WRITE)
mode |= S_IWUSR;
if (acl_group_obj_entry->ae_perm & ACL_EXECUTE)
mode |= S_IXGRP;
if (acl_group_obj_entry->ae_perm & ACL_READ)
mode |= S_IRGRP;
if (acl_group_obj_entry->ae_perm & ACL_WRITE)
mode |= S_IWGRP;
if (acl_other_entry->ae_perm & ACL_EXECUTE)
mode |= S_IXOTH;
if (acl_other_entry->ae_perm & ACL_READ)
mode |= S_IROTH;
if (acl_other_entry->ae_perm & ACL_WRITE)
mode |= S_IWOTH;
return (mode);
}
/*
* Utility function to generate a file mode given a complete POSIX.1e access
* ACL. Note that if the ACL is improperly formed, this may result in a
* panic.
*/
mode_t
acl_posix1e_acl_to_mode(struct acl *acl)
{
struct acl_entry *acl_mask, *acl_user_obj, *acl_group_obj, *acl_other;
int i;
/*
* Find the ACL entries relevant to a POSIX permission mode.
*/
acl_user_obj = acl_group_obj = acl_other = acl_mask = NULL;
for (i = 0; i < acl->acl_cnt; i++) {
switch (acl->acl_entry[i].ae_tag) {
case ACL_USER_OBJ:
acl_user_obj = &acl->acl_entry[i];
break;
case ACL_GROUP_OBJ:
acl_group_obj = &acl->acl_entry[i];
break;
case ACL_OTHER:
acl_other = &acl->acl_entry[i];
break;
case ACL_MASK:
acl_mask = &acl->acl_entry[i];
break;
case ACL_USER:
case ACL_GROUP:
break;
default:
panic("acl_posix1e_acl_to_mode: bad ae_tag");
}
}
if (acl_user_obj == NULL || acl_group_obj == NULL || acl_other == NULL)
panic("acl_posix1e_acl_to_mode: missing base ae_tags");
/*
* POSIX.1e specifies that if there is an ACL_MASK entry, we replace
* the mode "group" bits with its permissions. If there isn't, we
* use the ACL_GROUP_OBJ permissions.
*/
if (acl_mask != NULL)
return (acl_posix1e_perms_to_mode(acl_user_obj, acl_mask,
acl_other));
else
return (acl_posix1e_perms_to_mode(acl_user_obj, acl_group_obj,
acl_other));
}
/*
* Perform a syntactic check of the ACL, sufficient to allow an implementing
* filesystem to determine if it should accept this and rely on the POSIX.1e
* ACL properties.
*/
int
acl_posix1e_check(struct acl *acl)
{
int num_acl_user_obj, num_acl_user, num_acl_group_obj, num_acl_group;
int num_acl_mask, num_acl_other, i;
/*
* Verify that the number of entries does not exceed the maximum
* defined for acl_t.
*
* Verify that the correct number of various sorts of ae_tags are
* present:
* Exactly one ACL_USER_OBJ
* Exactly one ACL_GROUP_OBJ
* Exactly one ACL_OTHER
* If any ACL_USER or ACL_GROUP entries appear, then exactly one
* ACL_MASK entry must also appear.
*
* Verify that all ae_perm entries are in ACL_PERM_BITS.
*
* Verify all ae_tag entries are understood by this implementation.
*
* Note: Does not check for uniqueness of qualifier (ae_id) field.
*/
num_acl_user_obj = num_acl_user = num_acl_group_obj = num_acl_group =
num_acl_mask = num_acl_other = 0;
if (acl->acl_cnt > ACL_MAX_ENTRIES)
return (EINVAL);
for (i = 0; i < acl->acl_cnt; i++) {
/*
* Check for a valid tag.
*/
switch(acl->acl_entry[i].ae_tag) {
case ACL_USER_OBJ:
acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
return (EINVAL);
num_acl_user_obj++;
break;
case ACL_GROUP_OBJ:
acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
return (EINVAL);
num_acl_group_obj++;
break;
case ACL_USER:
if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID)
return (EINVAL);
num_acl_user++;
break;
case ACL_GROUP:
if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID)
return (EINVAL);
num_acl_group++;
break;
case ACL_OTHER:
acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
return (EINVAL);
num_acl_other++;
break;
case ACL_MASK:
acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
return (EINVAL);
num_acl_mask++;
break;
default:
return (EINVAL);
}
/*
* Check for valid perm entries.
*/
if ((acl->acl_entry[i].ae_perm | ACL_PERM_BITS) !=
ACL_PERM_BITS)
return (EINVAL);
}
if ((num_acl_user_obj != 1) || (num_acl_group_obj != 1) ||
(num_acl_other != 1) || (num_acl_mask != 0 && num_acl_mask != 1))
return (EINVAL);
if (((num_acl_group != 0) || (num_acl_user != 0)) &&
(num_acl_mask != 1))
return (EINVAL);
return (0);
}
/*
* Given a requested mode for a new object, and a default ACL, combine the
* two to produce a new mode. Be careful not to clear any bits that aren't
* intended to be affected by the POSIX.1e ACL. Eventually, this might also
* take the cmask as an argument, if we push that down into
* per-filesystem-code.
*/
mode_t
acl_posix1e_newfilemode(mode_t cmode, struct acl *dacl)
{
mode_t mode;
mode = cmode;
/*
* The current composition policy is that a permission bit must be
* set in *both* the ACL and the requested creation mode for it to
* appear in the resulting mode/ACL. First clear any possibly
* effected bits, then reconstruct.
*/
mode &= ACL_PRESERVE_MASK;
mode |= (ACL_OVERRIDE_MASK & cmode & acl_posix1e_acl_to_mode(dacl));
return (mode);
}
static int
acl_posix1e_modload(module_t mod, int what, void *arg)
{
int ret;
ret = 0;
switch (what) {
case MOD_LOAD:
case MOD_SHUTDOWN:
break;
case MOD_QUIESCE:
/* XXX TODO */
ret = 0;
break;
case MOD_UNLOAD:
/* XXX TODO */
ret = 0;
break;
default:
ret = EINVAL;
break;
}
return (ret);
}
static moduledata_t acl_posix1e_mod = {
"acl_posix1e",
acl_posix1e_modload,
NULL
};
DECLARE_MODULE(acl_posix1e, acl_posix1e_mod, SI_SUB_VFS, SI_ORDER_FIRST);
MODULE_VERSION(acl_posix1e, 1);
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