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NetBSD/sys/secmodel/keylock/secmodel_keylock.c
jym 926571dfa7 Implement the register/deregister/evaluation API for secmodel(9). It 
allows registration of callbacks that can be used later for
cross-secmodel "safe" communication.

When a secmodel wishes to know a property maintained by another
secmodel, it has to submit a request to it so the other secmodel can
proceed to evaluating the request. This is done through the
secmodel_eval(9) call; example:

    bool isroot;
    error = secmodel_eval("org.netbsd.secmodel.suser", "is-root",
        cred, &isroot);
    if (error == 0 && !isroot)
            result = KAUTH_RESULT_DENY;

This one asks the suser module if the credentials are assumed to be root
when evaluated by suser module. If the module is present, it will
respond. If absent, the call will return an error.

Args and command are arbitrarily defined; it's up to the secmodel(9) to
document what it expects.

Typical example is securelevel testing: when someone wants to know
whether securelevel is raised above a certain level or not, the caller
has to request this property to the secmodel_securelevel(9) module.
Given that securelevel module may be absent from system's context (thus
making access to the global "securelevel" variable impossible or
unsafe), this API can cope with this absence and return an error.

We are using secmodel_eval(9) to implement a secmodel_extensions(9)
module, which plugs with the bsd44, suser and securelevel secmodels
to provide the logic behind curtain, usermount and user_set_cpu_affinity
modes, without adding hooks to traditional secmodels. This solves a
real issue with the current secmodel(9) code, as usermount or
user_set_cpu_affinity are not really tied to secmodel_suser(9).

The secmodel_eval(9) is also used to restrict security.models settings
when securelevel is above 0, through the "is-securelevel-above"
evaluation:
- curtain can be enabled any time, but cannot be disabled if
securelevel is above 0.
- usermount/user_set_cpu_affinity can be disabled any time, but cannot
be enabled if securelevel is above 0.

Regarding sysctl(7) entries:
curtain and usermount are now found under security.models.extensions
tree. The security.curtain and vfs.generic.usermount are still
accessible for backwards compat.

Documentation is incoming, I am proof-reading my writings.

Written by elad@, reviewed and tested (anita test + interact for rights
tests) by me. ok elad@.

See also
http://mail-index.netbsd.org/tech-security/2011/11/29/msg000422.html

XXX might consider va0 mapping too.

XXX Having a secmodel(9) specific printf (like aprint_*) for reporting
secmodel(9) errors might be a good idea, but I am not sure on how
to design such a function right now.
2011-12-04 19:24:58 +00:00

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/* $NetBSD: secmodel_keylock.c,v 1.6 2011/12/04 19:25:00 jym Exp $ */
/*-
* Copyright (c) 2009 Marc Balmer <marc@msys.ch>
* Copyright (c) 2006 Elad Efrat <elad@NetBSD.org>
* All rights reserved.
*
* 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.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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.
*/
/*
* This file contains kauth(9) listeners needed to implement an experimental
* keylock based security scheme.
*
* The position of the keylock is a system-global indication on what
* operations are allowed or not. It affects all users, including root.
*
* Rules:
*
* - If the number of possible keylock positions is 0, assume there is no
* keylock present, do not dissallow any action, i.e. do nothing
*
* - If the number of possible keylock positions is greater than 0, but the
* current lock position is 0, assume tampering with the lock and forbid
* all actions.
*
* - If the lock is in the lowest position, assume the system is locked and
* forbid most actions.
*
* - If the lock is in the highest position, assume the system to be open and
* forbid nothing.
*
* - If the security.models.keylock.order sysctl is set to a value != 0,
* reverse this order.
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: secmodel_keylock.c,v 1.6 2011/12/04 19:25:00 jym Exp $");
#include <sys/types.h>
#include <sys/param.h>
#include <sys/kauth.h>
#include <sys/conf.h>
#include <sys/mount.h>
#include <sys/sysctl.h>
#include <sys/vnode.h>
#include <sys/timevar.h>
#include <dev/keylock.h>
#include <miscfs/specfs/specdev.h>
#include <secmodel/keylock/keylock.h>
static kauth_listener_t l_system, l_process, l_network, l_machdep, l_device;
SYSCTL_SETUP(sysctl_security_keylock_setup,
"sysctl security keylock setup")
{
const struct sysctlnode *rnode;
sysctl_createv(clog, 0, NULL, &rnode,
CTLFLAG_PERMANENT,
CTLTYPE_NODE, "security", NULL,
NULL, 0, NULL, 0,
CTL_SECURITY, CTL_EOL);
sysctl_createv(clog, 0, &rnode, &rnode,
CTLFLAG_PERMANENT,
CTLTYPE_NODE, "models", NULL,
NULL, 0, NULL, 0,
CTL_CREATE, CTL_EOL);
sysctl_createv(clog, 0, &rnode, &rnode,
CTLFLAG_PERMANENT,
CTLTYPE_NODE, "keylock",
SYSCTL_DESCR("Keylock security model"),
NULL, 0, NULL, 0,
CTL_CREATE, CTL_EOL);
sysctl_createv(clog, 0, &rnode, NULL,
CTLFLAG_PERMANENT,
CTLTYPE_STRING, "name", NULL,
NULL, 0, __UNCONST("Keylock"), 0,
CTL_CREATE, CTL_EOL);
}
void
secmodel_keylock_init(void)
{
int error = secmodel_register(&keylock_sm,
"org.netbsd.secmodel.keylock",
"NetBSD Security Model: Keylock", NULL, NULL, NULL);
if (error != 0)
printf("secmodel_keylock_init: secmodel_register "
"returned %d\n", error);
}
void
secmodel_keylock_start(void)
{
l_system = kauth_listen_scope(KAUTH_SCOPE_SYSTEM,
secmodel_keylock_system_cb, NULL);
l_process = kauth_listen_scope(KAUTH_SCOPE_PROCESS,
secmodel_keylock_process_cb, NULL);
l_network = kauth_listen_scope(KAUTH_SCOPE_NETWORK,
secmodel_keylock_network_cb, NULL);
l_machdep = kauth_listen_scope(KAUTH_SCOPE_MACHDEP,
secmodel_keylock_machdep_cb, NULL);
l_device = kauth_listen_scope(KAUTH_SCOPE_DEVICE,
secmodel_keylock_device_cb, NULL);
}
void
secmodel_keylock_stop(void)
{
int error;
kauth_unlisten_scope(l_system);
kauth_unlisten_scope(l_process);
kauth_unlisten_scope(l_network);
kauth_unlisten_scope(l_machdep);
kauth_unlisten_scope(l_device);
error = secmodel_deregister(&keylock_sm);
if (error != 0)
printf("secmodel_keylock_stop: secmodel_deregister "
"returned %d\n", error);
}
/*
* kauth(9) listener
*
* Security model: Multi-position keylock
* Scope: System
* Responsibility: Keylock
*/
int
secmodel_keylock_system_cb(kauth_cred_t cred,
kauth_action_t action, void *cookie, void *arg0, void *arg1,
void *arg2, void *arg3)
{
int result;
enum kauth_system_req req;
int kstate;
kstate = keylock_state();
if (kstate == KEYLOCK_ABSENT)
return KAUTH_RESULT_DEFER;
else if (kstate == KEYLOCK_TAMPER)
return KAUTH_RESULT_DENY;
result = KAUTH_RESULT_DEFER;
req = (enum kauth_system_req)arg0;
switch (action) {
case KAUTH_SYSTEM_CHSYSFLAGS:
if (kstate == KEYLOCK_CLOSE)
result = KAUTH_RESULT_DENY;
break;
case KAUTH_SYSTEM_TIME:
switch (req) {
case KAUTH_REQ_SYSTEM_TIME_RTCOFFSET:
if (kstate == KEYLOCK_CLOSE)
result = KAUTH_RESULT_DENY;
break;
case KAUTH_REQ_SYSTEM_TIME_SYSTEM: {
struct timespec *ts = arg1;
struct timespec *delta = arg2;
if (keylock_position() > 1 && time_wraps(ts, delta))
result = KAUTH_RESULT_DENY;
break;
}
default:
break;
}
break;
case KAUTH_SYSTEM_MODULE:
if (kstate == KEYLOCK_CLOSE)
result = KAUTH_RESULT_DENY;
break;
case KAUTH_SYSTEM_MOUNT:
switch (req) {
case KAUTH_REQ_SYSTEM_MOUNT_NEW:
if (kstate == KEYLOCK_CLOSE)
result = KAUTH_RESULT_DENY;
break;
case KAUTH_REQ_SYSTEM_MOUNT_UPDATE:
if (kstate == KEYLOCK_CLOSE) {
struct mount *mp = arg1;
u_long flags = (u_long)arg2;
/*
* Can only degrade from read/write to
* read-only.
*/
if (flags != (mp->mnt_flag | MNT_RDONLY |
MNT_RELOAD | MNT_FORCE | MNT_UPDATE))
result = KAUTH_RESULT_DENY;
}
break;
default:
break;
}
break;
case KAUTH_SYSTEM_SYSCTL:
switch (req) {
case KAUTH_REQ_SYSTEM_SYSCTL_ADD:
case KAUTH_REQ_SYSTEM_SYSCTL_DELETE:
case KAUTH_REQ_SYSTEM_SYSCTL_DESC:
if (kstate == KEYLOCK_CLOSE)
result = KAUTH_RESULT_DENY;
break;
default:
break;
}
break;
case KAUTH_SYSTEM_SETIDCORE:
if (kstate == KEYLOCK_CLOSE)
result = KAUTH_RESULT_DENY;
break;
case KAUTH_SYSTEM_DEBUG:
switch (req) {
case KAUTH_REQ_SYSTEM_DEBUG_IPKDB:
if (kstate == KEYLOCK_CLOSE)
result = KAUTH_RESULT_DENY;
break;
default:
break;
}
break;
}
return result;
}
/*
* kauth(9) listener
*
* Security model: Multi-position keylock
* Scope: Process
* Responsibility: Keylock
*/
int
secmodel_keylock_process_cb(kauth_cred_t cred,
kauth_action_t action, void *cookie, void *arg0,
void *arg1, void *arg2, void *arg3)
{
struct proc *p;
int result, kstate;
kstate = keylock_state();
if (kstate == KEYLOCK_ABSENT)
return KAUTH_RESULT_DEFER;
else if (kstate == KEYLOCK_TAMPER)
return KAUTH_RESULT_DENY;
result = KAUTH_RESULT_DEFER;
p = arg0;
switch (action) {
case KAUTH_PROCESS_PROCFS: {
enum kauth_process_req req;
req = (enum kauth_process_req)arg2;
switch (req) {
case KAUTH_REQ_PROCESS_PROCFS_READ:
break;
case KAUTH_REQ_PROCESS_PROCFS_RW:
case KAUTH_REQ_PROCESS_PROCFS_WRITE:
if ((p == initproc) && (kstate != KEYLOCK_OPEN))
result = KAUTH_RESULT_DENY;
break;
default:
break;
}
break;
}
case KAUTH_PROCESS_PTRACE:
if ((p == initproc) && (kstate != KEYLOCK_OPEN))
result = KAUTH_RESULT_DENY;
break;
case KAUTH_PROCESS_CORENAME:
if (kstate == KEYLOCK_CLOSE)
result = KAUTH_RESULT_DENY;
break;
}
return result;
}
/*
* kauth(9) listener
*
* Security model: Multi-position keylock
* Scope: Network
* Responsibility: Keylock
*/
int
secmodel_keylock_network_cb(kauth_cred_t cred,
kauth_action_t action, void *cookie, void *arg0,
void *arg1, void *arg2, void *arg3)
{
int result, kstate;
enum kauth_network_req req;
kstate = keylock_state();
if (kstate == KEYLOCK_ABSENT)
return KAUTH_RESULT_DEFER;
else if (kstate == KEYLOCK_TAMPER)
return KAUTH_RESULT_DENY;
result = KAUTH_RESULT_DEFER;
req = (enum kauth_network_req)arg0;
switch (action) {
case KAUTH_NETWORK_FIREWALL:
switch (req) {
case KAUTH_REQ_NETWORK_FIREWALL_FW:
case KAUTH_REQ_NETWORK_FIREWALL_NAT:
if (kstate == KEYLOCK_CLOSE)
result = KAUTH_RESULT_DENY;
break;
default:
break;
}
break;
case KAUTH_NETWORK_FORWSRCRT:
if (kstate != KEYLOCK_OPEN)
result = KAUTH_RESULT_DENY;
break;
}
return result;
}
/*
* kauth(9) listener
*
* Security model: Multi-position keylock
* Scope: Machdep
* Responsibility: Keylock
*/
int
secmodel_keylock_machdep_cb(kauth_cred_t cred,
kauth_action_t action, void *cookie, void *arg0,
void *arg1, void *arg2, void *arg3)
{
int result, kstate;
kstate = keylock_state();
if (kstate == KEYLOCK_ABSENT)
return KAUTH_RESULT_DEFER;
else if (kstate == KEYLOCK_TAMPER)
return KAUTH_RESULT_DENY;
result = KAUTH_RESULT_DEFER;
switch (action) {
case KAUTH_MACHDEP_IOPERM_SET:
case KAUTH_MACHDEP_IOPL:
if (kstate != KEYLOCK_OPEN)
result = KAUTH_RESULT_DENY;
break;
case KAUTH_MACHDEP_UNMANAGEDMEM:
if (kstate != KEYLOCK_OPEN)
result = KAUTH_RESULT_DENY;
break;
}
return result;
}
/*
* kauth(9) listener
*
* Security model: Multi-position keylock
* Scope: Device
* Responsibility: Keylock
*/
int
secmodel_keylock_device_cb(kauth_cred_t cred,
kauth_action_t action, void *cookie, void *arg0,
void *arg1, void *arg2, void *arg3)
{
int result, kstate, error;
kstate = keylock_state();
if (kstate == KEYLOCK_ABSENT)
return KAUTH_RESULT_DEFER;
else if (kstate == KEYLOCK_TAMPER)
return KAUTH_RESULT_DENY;
result = KAUTH_RESULT_DEFER;
switch (action) {
case KAUTH_DEVICE_RAWIO_SPEC: {
struct vnode *vp;
enum kauth_device_req req;
req = (enum kauth_device_req)arg0;
vp = arg1;
KASSERT(vp != NULL);
/* Handle /dev/mem and /dev/kmem. */
if (iskmemvp(vp)) {
switch (req) {
case KAUTH_REQ_DEVICE_RAWIO_SPEC_READ:
break;
case KAUTH_REQ_DEVICE_RAWIO_SPEC_WRITE:
case KAUTH_REQ_DEVICE_RAWIO_SPEC_RW:
if (kstate != KEYLOCK_OPEN)
result = KAUTH_RESULT_DENY;
break;
default:
break;
}
break;
}
switch (req) {
case KAUTH_REQ_DEVICE_RAWIO_SPEC_READ:
break;
case KAUTH_REQ_DEVICE_RAWIO_SPEC_WRITE:
case KAUTH_REQ_DEVICE_RAWIO_SPEC_RW:
error = rawdev_mounted(vp, NULL);
if (error == EINVAL)
break;
if (error && (kstate != KEYLOCK_OPEN))
break;
if (kstate == KEYLOCK_CLOSE)
result = KAUTH_RESULT_DENY;
break;
default:
break;
}
break;
}
case KAUTH_DEVICE_RAWIO_PASSTHRU:
if (kstate != KEYLOCK_OPEN) {
u_long bits;
bits = (u_long)arg0;
KASSERT(bits != 0);
KASSERT((bits & ~KAUTH_REQ_DEVICE_RAWIO_PASSTHRU_ALL)
== 0);
if (bits & ~KAUTH_REQ_DEVICE_RAWIO_PASSTHRU_READCONF)
result = KAUTH_RESULT_DENY;
}
break;
case KAUTH_DEVICE_GPIO_PINSET:
if (kstate != KEYLOCK_OPEN)
result = KAUTH_RESULT_DENY;
break;
default:
break;
}
return result;
}
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