freebsd-skq/sys/kern/subr_acl_posix1e.c
rwatson e8e07ae08e Move POSIX.1e-specific utility routines from kern_acl.c to
subr_acl_posix1e.c, leaving kern_acl.c containing only ACL system
calls and utility routines common across ACL types.

Add subr_acl_posix1e.c to the build.

Obtained from:	TrustedBSD Project
2006-07-06 23:37:39 +00:00

626 lines
17 KiB
C

/*-
* 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/systm.h>
#include <sys/mount.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.
* Return 0 on success, else an errno value. Should be merged into
* vaccess() eventually.
*/
int
vaccess_acl_posix1e(enum vtype type, uid_t file_uid, gid_t file_gid,
struct acl *acl, mode_t acc_mode, struct ucred *cred, int *privused)
{
struct acl_entry *acl_other, *acl_mask;
mode_t dac_granted;
mode_t cap_granted;
mode_t acl_mask_granted;
int group_matched, i;
/*
* 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 cap_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.
*/
#ifndef CAPABILITIES
if (suser_cred(cred, SUSER_ALLOWJAIL) == 0)
cap_granted = VALLPERM;
else
cap_granted = 0;
#else
cap_granted = 0;
if (type == VDIR) {
if ((acc_mode & VEXEC) && !cap_check(cred, NULL,
CAP_DAC_READ_SEARCH, SUSER_ALLOWJAIL))
cap_granted |= VEXEC;
} else {
if ((acc_mode & VEXEC) && !cap_check(cred, NULL,
CAP_DAC_EXECUTE, SUSER_ALLOWJAIL))
cap_granted |= VEXEC;
}
if ((acc_mode & VREAD) && !cap_check(cred, NULL, CAP_DAC_READ_SEARCH,
SUSER_ALLOWJAIL))
cap_granted |= VREAD;
if (((acc_mode & VWRITE) || (acc_mode & VAPPEND)) &&
!cap_check(cred, NULL, CAP_DAC_WRITE, SUSER_ALLOWJAIL))
cap_granted |= (VWRITE | VAPPEND);
if ((acc_mode & VADMIN) && !cap_check(cred, NULL, CAP_FOWNER,
SUSER_ALLOWJAIL))
cap_granted |= VADMIN;
#endif /* CAPABILITIES */
/*
* 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 ((acc_mode & dac_granted) == acc_mode)
return (0);
if ((acc_mode & (dac_granted | cap_granted)) ==
acc_mode) {
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;
/*
* Iterate through user ACL entries. Do checks twice, first
* without privilege, and then if a match is found but failed,
* a second time with privilege.
*/
/*
* Check ACL_USER ACL entries.
*/
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 ((acc_mode & dac_granted) == acc_mode)
return (0);
if ((acc_mode & (dac_granted | cap_granted)) !=
acc_mode)
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 ((acc_mode & dac_granted) == acc_mode)
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 ((acc_mode & dac_granted) == acc_mode)
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;
if ((acc_mode & (dac_granted | cap_granted)) !=
acc_mode)
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;
if ((acc_mode & (dac_granted | cap_granted)) !=
acc_mode)
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 ((acc_mode & dac_granted) == acc_mode)
return (0);
if ((acc_mode & (dac_granted | cap_granted)) == acc_mode) {
if (privused != NULL)
*privused = 1;
return (0);
}
error:
return ((acc_mode & 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);
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 || acl->acl_cnt < 0)
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);
}