jcs.org
qemu with hax to log dma reads & writes
jcs.org/2018/11/12/vfio
authz: add QAuthZPAM object type for authorizing using PAM
Add an authorization backend that talks to PAM to check whether the user
identity is allowed. This only uses the PAM account validation facility,
which is essentially just a check to see if the provided username is permitted
access. It doesn't use the authentication or session parts of PAM, since
that's dealt with by the relevant part of QEMU (eg VNC server).
Consider starting QEMU with a VNC server and telling it to use TLS with
x509 client certificates and configuring it to use an PAM to validate
the x509 distinguished name. In this example we're telling it to use PAM
for the QAuthZ impl with a service name of "qemu-vnc"
$ qemu-system-x86_64 \
-object tls-creds-x509,id=tls0,dir=/home/berrange/security/qemutls,\
endpoint=server,verify-peer=yes \
-object authz-pam,id=authz0,service=qemu-vnc \
-vnc :1,tls-creds=tls0,tls-authz=authz0
This requires an /etc/pam/qemu-vnc file to be created with the auth
rules. A very simple file based whitelist can be setup using
$ cat > /etc/pam/qemu-vnc <<EOF
account requisite pam_listfile.so item=user sense=allow file=/etc/qemu/vnc.allow
EOF
The /etc/qemu/vnc.allow file simply contains one username per line. Any
username not in the file is denied. The usernames in this example are
the x509 distinguished name from the client's x509 cert.
$ cat > /etc/qemu/vnc.allow <<EOF
CN=laptop.berrange.com,O=Berrange Home,L=London,ST=London,C=GB
EOF
More interesting would be to configure PAM to use an LDAP backend, so
that the QEMU authorization check data can be centralized instead of
requiring each compute host to have file maintained.
The main limitation with this PAM module is that the rules apply to all
QEMU instances on the host. Setting up different rules per VM, would
require creating a separate PAM service name & config file for every
guest. An alternative approach for the future might be to not pass in
the plain username to PAM, but instead combine the VM name or UUID with
the username. This requires further consideration though.
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
+452
+3
authz/Makefile.objs
+3
authz/Makefile.objs
+148
authz/pamacct.c
+148
authz/pamacct.c
···
1
+
/*
2
+
* QEMU PAM authorization driver
3
+
*
4
+
* Copyright (c) 2018 Red Hat, Inc.
5
+
*
6
+
* This library is free software; you can redistribute it and/or
7
+
* modify it under the terms of the GNU Lesser General Public
8
+
* License as published by the Free Software Foundation; either
9
+
* version 2 of the License, or (at your option) any later version.
10
+
*
11
+
* This library is distributed in the hope that it will be useful,
12
+
* but WITHOUT ANY WARRANTY; without even the implied warranty of
13
+
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14
+
* Lesser General Public License for more details.
15
+
*
16
+
* You should have received a copy of the GNU Lesser General Public
17
+
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
18
+
*
19
+
*/
20
+
21
+
#include "qemu/osdep.h"
22
+
#include "authz/pamacct.h"
23
+
#include "authz/trace.h"
24
+
#include "qom/object_interfaces.h"
25
+
26
+
#include <security/pam_appl.h>
27
+
28
+
29
+
static bool qauthz_pam_is_allowed(QAuthZ *authz,
30
+
const char *identity,
31
+
Error **errp)
32
+
{
33
+
QAuthZPAM *pauthz = QAUTHZ_PAM(authz);
34
+
const struct pam_conv pam_conversation = { 0 };
35
+
pam_handle_t *pamh = NULL;
36
+
int ret;
37
+
38
+
trace_qauthz_pam_check(authz, identity, pauthz->service);
39
+
ret = pam_start(pauthz->service,
40
+
identity,
41
+
&pam_conversation,
42
+
&pamh);
43
+
if (ret != PAM_SUCCESS) {
44
+
error_setg(errp, "Unable to start PAM transaction: %s",
45
+
pam_strerror(NULL, ret));
46
+
return false;
47
+
}
48
+
49
+
ret = pam_acct_mgmt(pamh, PAM_SILENT);
50
+
pam_end(pamh, ret);
51
+
if (ret != PAM_SUCCESS) {
52
+
error_setg(errp, "Unable to authorize user '%s': %s",
53
+
identity, pam_strerror(pamh, ret));
54
+
return false;
55
+
}
56
+
57
+
return true;
58
+
}
59
+
60
+
61
+
static void
62
+
qauthz_pam_prop_set_service(Object *obj,
63
+
const char *service,
64
+
Error **errp G_GNUC_UNUSED)
65
+
{
66
+
QAuthZPAM *pauthz = QAUTHZ_PAM(obj);
67
+
68
+
g_free(pauthz->service);
69
+
pauthz->service = g_strdup(service);
70
+
}
71
+
72
+
73
+
static char *
74
+
qauthz_pam_prop_get_service(Object *obj,
75
+
Error **errp G_GNUC_UNUSED)
76
+
{
77
+
QAuthZPAM *pauthz = QAUTHZ_PAM(obj);
78
+
79
+
return g_strdup(pauthz->service);
80
+
}
81
+
82
+
83
+
static void
84
+
qauthz_pam_complete(UserCreatable *uc, Error **errp)
85
+
{
86
+
}
87
+
88
+
89
+
static void
90
+
qauthz_pam_finalize(Object *obj)
91
+
{
92
+
QAuthZPAM *pauthz = QAUTHZ_PAM(obj);
93
+
94
+
g_free(pauthz->service);
95
+
}
96
+
97
+
98
+
static void
99
+
qauthz_pam_class_init(ObjectClass *oc, void *data)
100
+
{
101
+
UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
102
+
QAuthZClass *authz = QAUTHZ_CLASS(oc);
103
+
104
+
ucc->complete = qauthz_pam_complete;
105
+
authz->is_allowed = qauthz_pam_is_allowed;
106
+
107
+
object_class_property_add_str(oc, "service",
108
+
qauthz_pam_prop_get_service,
109
+
qauthz_pam_prop_set_service,
110
+
NULL);
111
+
}
112
+
113
+
114
+
QAuthZPAM *qauthz_pam_new(const char *id,
115
+
const char *service,
116
+
Error **errp)
117
+
{
118
+
return QAUTHZ_PAM(
119
+
object_new_with_props(TYPE_QAUTHZ_PAM,
120
+
object_get_objects_root(),
121
+
id, errp,
122
+
"service", service,
123
+
NULL));
124
+
}
125
+
126
+
127
+
static const TypeInfo qauthz_pam_info = {
128
+
.parent = TYPE_QAUTHZ,
129
+
.name = TYPE_QAUTHZ_PAM,
130
+
.instance_size = sizeof(QAuthZPAM),
131
+
.instance_finalize = qauthz_pam_finalize,
132
+
.class_size = sizeof(QAuthZPAMClass),
133
+
.class_init = qauthz_pam_class_init,
134
+
.interfaces = (InterfaceInfo[]) {
135
+
{ TYPE_USER_CREATABLE },
136
+
{ }
137
+
}
138
+
};
139
+
140
+
141
+
static void
142
+
qauthz_pam_register_types(void)
143
+
{
144
+
type_register_static(&qauthz_pam_info);
145
+
}
146
+
147
+
148
+
type_init(qauthz_pam_register_types);
+3
authz/trace-events
+3
authz/trace-events
···
13
13
# auth/listfile.c
14
14
qauthz_list_file_load(void *authz, const char *filename) "AuthZ file %p load filename=%s"
15
15
qauthz_list_file_refresh(void *authz, const char *filename, int success) "AuthZ file %p load filename=%s success=%d"
16
+
17
+
# auth/pam.c
18
+
qauthz_pam_check(void *authz, const char *identity, const char *service) "AuthZ PAM %p identity=%s service=%s"
+37
configure
+37
configure
···
463
463
nettle=""
464
464
gcrypt=""
465
465
gcrypt_hmac="no"
466
+
auth_pam=""
466
467
vte=""
467
468
virglrenderer=""
468
469
tpm="yes"
···
1380
1381
--disable-gcrypt) gcrypt="no"
1381
1382
;;
1382
1383
--enable-gcrypt) gcrypt="yes"
1384
+
;;
1385
+
--disable-auth-pam) auth_pam="no"
1386
+
;;
1387
+
--enable-auth-pam) auth_pam="yes"
1383
1388
;;
1384
1389
--enable-rdma) rdma="yes"
1385
1390
;;
···
1707
1712
gnutls GNUTLS cryptography support
1708
1713
nettle nettle cryptography support
1709
1714
gcrypt libgcrypt cryptography support
1715
+
auth-pam PAM access control
1710
1716
sdl SDL UI
1711
1717
sdl_image SDL Image support for icons
1712
1718
gtk gtk UI
···
2863
2869
tasn1=no
2864
2870
fi
2865
2871
2872
+
2873
+
##########################################
2874
+
# PAM probe
2875
+
2876
+
if test "$auth_pam" != "no"; then
2877
+
cat > $TMPC <<EOF
2878
+
#include <security/pam_appl.h>
2879
+
#include <stdio.h>
2880
+
int main(void) {
2881
+
const char *service_name = "qemu";
2882
+
const char *user = "frank";
2883
+
const struct pam_conv *pam_conv = NULL;
2884
+
pam_handle_t *pamh = NULL;
2885
+
pam_start(service_name, user, pam_conv, &pamh);
2886
+
return 0;
2887
+
}
2888
+
EOF
2889
+
if compile_prog "" "-lpam" ; then
2890
+
auth_pam=yes
2891
+
else
2892
+
if test "$auth_pam" = "yes"; then
2893
+
feature_not_found "PAM" "Install PAM development package"
2894
+
else
2895
+
auth_pam=no
2896
+
fi
2897
+
fi
2898
+
fi
2866
2899
2867
2900
##########################################
2868
2901
# getifaddrs (for tests/test-io-channel-socket )
···
6091
6124
echo "libgcrypt $gcrypt"
6092
6125
echo "nettle $nettle $(echo_version $nettle $nettle_version)"
6093
6126
echo "libtasn1 $tasn1"
6127
+
echo "PAM $auth_pam"
6094
6128
echo "curses support $curses"
6095
6129
echo "virgl support $virglrenderer $(echo_version $virglrenderer $virgl_version)"
6096
6130
echo "curl support $curl"
···
6549
6583
fi
6550
6584
if test "$tasn1" = "yes" ; then
6551
6585
echo "CONFIG_TASN1=y" >> $config_host_mak
6586
+
fi
6587
+
if test "$auth_pam" = "yes" ; then
6588
+
echo "CONFIG_AUTH_PAM=y" >> $config_host_mak
6552
6589
fi
6553
6590
if test "$have_ifaddrs_h" = "yes" ; then
6554
6591
echo "HAVE_IFADDRS_H=y" >> $config_host_mak
+100
include/authz/pamacct.h
+100
include/authz/pamacct.h
···
1
+
/*
2
+
* QEMU PAM authorization driver
3
+
*
4
+
* Copyright (c) 2018 Red Hat, Inc.
5
+
*
6
+
* This library is free software; you can redistribute it and/or
7
+
* modify it under the terms of the GNU Lesser General Public
8
+
* License as published by the Free Software Foundation; either
9
+
* version 2 of the License, or (at your option) any later version.
10
+
*
11
+
* This library is distributed in the hope that it will be useful,
12
+
* but WITHOUT ANY WARRANTY; without even the implied warranty of
13
+
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14
+
* Lesser General Public License for more details.
15
+
*
16
+
* You should have received a copy of the GNU Lesser General Public
17
+
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
18
+
*
19
+
*/
20
+
21
+
#ifndef QAUTHZ_PAM_H__
22
+
#define QAUTHZ_PAM_H__
23
+
24
+
#include "authz/base.h"
25
+
26
+
27
+
#define TYPE_QAUTHZ_PAM "authz-pam"
28
+
29
+
#define QAUTHZ_PAM_CLASS(klass) \
30
+
OBJECT_CLASS_CHECK(QAuthZPAMClass, (klass), \
31
+
TYPE_QAUTHZ_PAM)
32
+
#define QAUTHZ_PAM_GET_CLASS(obj) \
33
+
OBJECT_GET_CLASS(QAuthZPAMClass, (obj), \
34
+
TYPE_QAUTHZ_PAM)
35
+
#define QAUTHZ_PAM(obj) \
36
+
INTERFACE_CHECK(QAuthZPAM, (obj), \
37
+
TYPE_QAUTHZ_PAM)
38
+
39
+
typedef struct QAuthZPAM QAuthZPAM;
40
+
typedef struct QAuthZPAMClass QAuthZPAMClass;
41
+
42
+
43
+
/**
44
+
* QAuthZPAM:
45
+
*
46
+
* This authorization driver provides a PAM mechanism
47
+
* for granting access by matching user names against a
48
+
* list of globs. Each match rule has an associated policy
49
+
* and a catch all policy applies if no rule matches
50
+
*
51
+
* To create an instance of this class via QMP:
52
+
*
53
+
* {
54
+
* "execute": "object-add",
55
+
* "arguments": {
56
+
* "qom-type": "authz-pam",
57
+
* "id": "authz0",
58
+
* "parameters": {
59
+
* "service": "qemu-vnc-tls"
60
+
* }
61
+
* }
62
+
* }
63
+
*
64
+
* The driver only uses the PAM "account" verification
65
+
* subsystem. The above config would require a config
66
+
* file /etc/pam.d/qemu-vnc-tls. For a simple file
67
+
* lookup it would contain
68
+
*
69
+
* account requisite pam_listfile.so item=user sense=allow \
70
+
* file=/etc/qemu/vnc.allow
71
+
*
72
+
* The external file would then contain a list of usernames.
73
+
* If x509 cert was being used as the username, a suitable
74
+
* entry would match the distinguish name:
75
+
*
76
+
* CN=laptop.berrange.com,O=Berrange Home,L=London,ST=London,C=GB
77
+
*
78
+
* On the command line it can be created using
79
+
*
80
+
* -object authz-pam,id=authz0,service=qemu-vnc-tls
81
+
*
82
+
*/
83
+
struct QAuthZPAM {
84
+
QAuthZ parent_obj;
85
+
86
+
char *service;
87
+
};
88
+
89
+
90
+
struct QAuthZPAMClass {
91
+
QAuthZClass parent_class;
92
+
};
93
+
94
+
95
+
QAuthZPAM *qauthz_pam_new(const char *id,
96
+
const char *service,
97
+
Error **errp);
98
+
99
+
100
+
#endif /* QAUTHZ_PAM_H__ */
+35
qemu-options.hx
+35
qemu-options.hx
···
4435
4435
...
4436
4436
@end example
4437
4437
4438
+
@item -object authz-pam,id=@var{id},service=@var{string}
4439
+
4440
+
Create an authorization object that will control access to network services.
4441
+
4442
+
The @option{service} parameter provides the name of a PAM service to use
4443
+
for authorization. It requires that a file @code{/etc/pam.d/@var{service}}
4444
+
exist to provide the configuration for the @code{account} subsystem.
4445
+
4446
+
An example authorization object to validate a TLS x509 distinguished
4447
+
name would look like:
4448
+
4449
+
@example
4450
+
# $QEMU \
4451
+
...
4452
+
-object authz-pam,id=auth0,service=qemu-vnc
4453
+
...
4454
+
@end example
4455
+
4456
+
There would then be a corresponding config file for PAM at
4457
+
@code{/etc/pam.d/qemu-vnc} that contains:
4458
+
4459
+
@example
4460
+
account requisite pam_listfile.so item=user sense=allow \
4461
+
file=/etc/qemu/vnc.allow
4462
+
@end example
4463
+
4464
+
Finally the @code{/etc/qemu/vnc.allow} file would contain
4465
+
the list of x509 distingished names that are permitted
4466
+
access
4467
+
4468
+
@example
4469
+
CN=laptop.example.com,O=Example Home,L=London,ST=London,C=GB
4470
+
@end example
4471
+
4472
+
4438
4473
@end table
4439
4474
4440
4475
ETEXI
+2
tests/Makefile.include
+2
tests/Makefile.include
···
119
119
check-unit-y += tests/test-authz-simple$(EXESUF)
120
120
check-unit-y += tests/test-authz-list$(EXESUF)
121
121
check-unit-y += tests/test-authz-listfile$(EXESUF)
122
+
check-unit-$(CONFIG_AUTH_PAM) += tests/test-authz-pam$(EXESUF)
122
123
check-unit-y += tests/test-io-task$(EXESUF)
123
124
check-unit-y += tests/test-io-channel-socket$(EXESUF)
124
125
check-unit-y += tests/test-io-channel-file$(EXESUF)
···
669
670
tests/test-authz-simple$(EXESUF): tests/test-authz-simple.o $(test-authz-obj-y)
670
671
tests/test-authz-list$(EXESUF): tests/test-authz-list.o $(test-authz-obj-y)
671
672
tests/test-authz-listfile$(EXESUF): tests/test-authz-listfile.o $(test-authz-obj-y)
673
+
tests/test-authz-pam$(EXESUF): tests/test-authz-pam.o $(test-authz-obj-y)
672
674
tests/test-io-task$(EXESUF): tests/test-io-task.o $(test-io-obj-y)
673
675
tests/test-io-channel-socket$(EXESUF): tests/test-io-channel-socket.o \
674
676
tests/io-channel-helpers.o tests/socket-helpers.o $(test-io-obj-y)
+124
tests/test-authz-pam.c
+124
tests/test-authz-pam.c
···
1
+
/*
2
+
* QEMU PAM authorization object tests
3
+
*
4
+
* Copyright (c) 2018 Red Hat, Inc.
5
+
*
6
+
* This library is free software; you can redistribute it and/or
7
+
* modify it under the terms of the GNU Lesser General Public
8
+
* License as published by the Free Software Foundation; either
9
+
* version 2 of the License, or (at your option) any later version.
10
+
*
11
+
* This library is distributed in the hope that it will be useful,
12
+
* but WITHOUT ANY WARRANTY; without even the implied warranty of
13
+
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14
+
* Lesser General Public License for more details.
15
+
*
16
+
* You should have received a copy of the GNU Lesser General Public
17
+
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
18
+
*
19
+
*/
20
+
21
+
#include "qemu/osdep.h"
22
+
#include "qapi/error.h"
23
+
#include "authz/pamacct.h"
24
+
25
+
#include <security/pam_appl.h>
26
+
27
+
static bool failauth;
28
+
29
+
/*
30
+
* These two functions are exported by libpam.so.
31
+
*
32
+
* By defining them again here, our impls are resolved
33
+
* by the linker instead of those in libpam.so
34
+
*
35
+
* The test suite is thus isolated from the host system
36
+
* PAM setup, so we can do predictable test scenarios
37
+
*/
38
+
int
39
+
pam_start(const char *service_name, const char *user,
40
+
const struct pam_conv *pam_conversation,
41
+
pam_handle_t **pamh)
42
+
{
43
+
failauth = true;
44
+
if (!g_str_equal(service_name, "qemu-vnc")) {
45
+
return PAM_AUTH_ERR;
46
+
}
47
+
48
+
if (g_str_equal(user, "fred")) {
49
+
failauth = false;
50
+
}
51
+
52
+
return PAM_SUCCESS;
53
+
}
54
+
55
+
56
+
int
57
+
pam_acct_mgmt(pam_handle_t *pamh, int flags)
58
+
{
59
+
if (failauth) {
60
+
return PAM_AUTH_ERR;
61
+
}
62
+
63
+
return PAM_SUCCESS;
64
+
}
65
+
66
+
67
+
static void test_authz_unknown_service(void)
68
+
{
69
+
Error *local_err = NULL;
70
+
QAuthZPAM *auth = qauthz_pam_new("auth0",
71
+
"qemu-does-not-exist",
72
+
&error_abort);
73
+
74
+
g_assert_nonnull(auth);
75
+
76
+
g_assert_false(qauthz_is_allowed(QAUTHZ(auth), "fred", &local_err));
77
+
78
+
error_free_or_abort(&local_err);
79
+
object_unparent(OBJECT(auth));
80
+
}
81
+
82
+
83
+
static void test_authz_good_user(void)
84
+
{
85
+
QAuthZPAM *auth = qauthz_pam_new("auth0",
86
+
"qemu-vnc",
87
+
&error_abort);
88
+
89
+
g_assert_nonnull(auth);
90
+
91
+
g_assert_true(qauthz_is_allowed(QAUTHZ(auth), "fred", &error_abort));
92
+
93
+
object_unparent(OBJECT(auth));
94
+
}
95
+
96
+
97
+
static void test_authz_bad_user(void)
98
+
{
99
+
Error *local_err = NULL;
100
+
QAuthZPAM *auth = qauthz_pam_new("auth0",
101
+
"qemu-vnc",
102
+
&error_abort);
103
+
104
+
g_assert_nonnull(auth);
105
+
106
+
g_assert_false(qauthz_is_allowed(QAUTHZ(auth), "bob", &local_err));
107
+
108
+
error_free_or_abort(&local_err);
109
+
object_unparent(OBJECT(auth));
110
+
}
111
+
112
+
113
+
int main(int argc, char **argv)
114
+
{
115
+
g_test_init(&argc, &argv, NULL);
116
+
117
+
module_call_init(MODULE_INIT_QOM);
118
+
119
+
g_test_add_func("/auth/pam/unknown-service", test_authz_unknown_service);
120
+
g_test_add_func("/auth/pam/good-user", test_authz_good_user);
121
+
g_test_add_func("/auth/pam/bad-user", test_authz_bad_user);
122
+
123
+
return g_test_run();
124
+
}