* [Qemu-devel] [PATCH v2] crypto: Implement TLS Pre-Shared Keys (PSK).
2018-06-26 10:25 [Qemu-devel] [PATCH v2] crypto: Implement TLS Pre-Shared Keys (PSK) Richard W.M. Jones
@ 2018-06-26 10:25 ` Richard W.M. Jones
2018-06-27 12:21 ` Daniel P. Berrangé
0 siblings, 1 reply; 3+ messages in thread
From: Richard W.M. Jones @ 2018-06-26 10:25 UTC (permalink / raw)
To: qemu-devel
Pre-Shared Keys (PSK) is a simpler mechanism for enabling TLS
connections than using certificates. It requires only a simple secret
key:
$ mkdir -m 0700 /tmp/keys
$ psktool -u rjones -p /tmp/keys/keys.psk
$ cat /tmp/keys/keys.psk
rjones:d543770c15ad93d76443fb56f501a31969235f47e999720ae8d2336f6a13fcbc
The key can be secretly shared between clients and servers. Clients
must specify the directory containing the "keys.psk" file and a
username (defaults to "qemu"). Servers must specify only the
directory.
Example NBD client:
$ qemu-img info \
--object tls-creds-psk,id=tls0,dir=/tmp/keys,username=rjones,endpoint=client \
--image-opts \
file.driver=nbd,file.host=localhost,file.port=10809,file.tls-creds=tls0,file.export=/
Example NBD server using qemu-nbd:
$ qemu-nbd -t -x / \
--object tls-creds-psk,id=tls0,endpoint=server,dir=/tmp/keys \
--tls-creds tls0 \
image.qcow2
Example NBD server using nbdkit:
$ nbdkit -n -e / -fv \
--tls=on --tls-psk=/tmp/keys/keys.psk \
file file=disk.img
Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
---
crypto/Makefile.objs | 1 +
crypto/tlscredspsk.c | 300 +++++++++++++++++++++++++++++++++++++++++++
crypto/tlssession.c | 38 ++++++
crypto/trace-events | 3 +
include/crypto/tlscredspsk.h | 106 +++++++++++++++
qemu-doc.texi | 37 ++++++
qemu-options.hx | 24 ++++
7 files changed, 509 insertions(+)
diff --git a/crypto/Makefile.objs b/crypto/Makefile.objs
index 2b99e08062..756bab111b 100644
--- a/crypto/Makefile.objs
+++ b/crypto/Makefile.objs
@@ -15,6 +15,7 @@ crypto-obj-$(CONFIG_AF_ALG) += cipher-afalg.o
crypto-obj-$(CONFIG_AF_ALG) += hash-afalg.o
crypto-obj-y += tlscreds.o
crypto-obj-y += tlscredsanon.o
+crypto-obj-y += tlscredspsk.o
crypto-obj-y += tlscredsx509.o
crypto-obj-y += tlssession.o
crypto-obj-y += secret.o
diff --git a/crypto/tlscredspsk.c b/crypto/tlscredspsk.c
new file mode 100644
index 0000000000..e9ec23b457
--- /dev/null
+++ b/crypto/tlscredspsk.c
@@ -0,0 +1,300 @@
+/*
+ * QEMU crypto TLS Pre-Shared Keys (PSK) support
+ *
+ * Copyright (c) 2018 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "crypto/tlscredspsk.h"
+#include "tlscredspriv.h"
+#include "qapi/error.h"
+#include "qom/object_interfaces.h"
+#include "trace.h"
+
+
+#ifdef CONFIG_GNUTLS
+
+static int
+lookup_key(const char *pskfile, const char *username, gnutls_datum_t *key,
+ Error **errp)
+{
+ FILE *fp;
+ char line[1024]; /* Maximum key length in psktool is 512 bytes. */
+ size_t ulen = strlen(username);
+ size_t len;
+
+ fp = fopen(pskfile, "r");
+ if (fp == NULL) {
+ error_setg_errno(errp, errno, "Cannot open PSK file %s", pskfile);
+ return -1;
+ }
+ while (fgets(line, sizeof line, fp) != NULL) {
+ if (strncmp(line, username, ulen) == 0 && line[ulen] == ':') {
+ len = strlen(line);
+ if (len > 0 && line[len - 1] == '\n') {
+ len--;
+ line[len] = '\0';
+ }
+ key->data = (unsigned char *) g_strdup(&line[ulen + 1]);
+ key->size = len - ulen - 1;
+ fclose(fp);
+ return 0;
+ }
+ }
+ fclose(fp);
+ error_setg(errp, "Username %s not found in PSK file %s",
+ username, pskfile);
+ return -1;
+}
+
+static int
+qcrypto_tls_creds_psk_load(QCryptoTLSCredsPSK *creds,
+ Error **errp)
+{
+ char *pskfile = NULL, *dhparams = NULL;
+ const char *username;
+ int ret;
+ int rv = -1;
+ gnutls_datum_t key = { .data = NULL };
+
+ trace_qcrypto_tls_creds_psk_load(creds,
+ creds->parent_obj.dir ? creds->parent_obj.dir : "<nodir>");
+
+ if (creds->parent_obj.endpoint == QCRYPTO_TLS_CREDS_ENDPOINT_SERVER) {
+ if (qcrypto_tls_creds_get_path(&creds->parent_obj,
+ QCRYPTO_TLS_CREDS_DH_PARAMS,
+ false, &dhparams, errp) < 0 ||
+ qcrypto_tls_creds_get_path(&creds->parent_obj,
+ QCRYPTO_TLS_CREDS_PSKFILE,
+ true, &pskfile, errp) < 0) {
+ goto cleanup;
+ }
+
+ ret = gnutls_psk_allocate_server_credentials(&creds->data.server);
+ if (ret < 0) {
+ error_setg(errp, "Cannot allocate credentials: %s",
+ gnutls_strerror(ret));
+ goto cleanup;
+ }
+
+ if (qcrypto_tls_creds_get_dh_params_file(&creds->parent_obj, dhparams,
+ &creds->parent_obj.dh_params,
+ errp) < 0) {
+ goto cleanup;
+ }
+
+ gnutls_psk_set_server_credentials_file(creds->data.server, pskfile);
+ gnutls_psk_set_server_dh_params(creds->data.server,
+ creds->parent_obj.dh_params);
+ } else {
+ if (qcrypto_tls_creds_get_path(&creds->parent_obj,
+ QCRYPTO_TLS_CREDS_PSKFILE,
+ true, &pskfile, errp) < 0) {
+ goto cleanup;
+ }
+
+ if (creds->username) {
+ username = creds->username;
+ } else {
+ username = "qemu";
+ }
+ if (lookup_key(pskfile, username, &key, errp) != 0) {
+ goto cleanup;
+ }
+
+ ret = gnutls_psk_allocate_client_credentials(&creds->data.client);
+ if (ret < 0) {
+ error_setg(errp, "Cannot allocate credentials: %s",
+ gnutls_strerror(ret));
+ goto cleanup;
+ }
+
+ gnutls_psk_set_client_credentials(creds->data.client,
+ username, &key, GNUTLS_PSK_KEY_HEX);
+ }
+
+ rv = 0;
+ cleanup:
+ g_free(key.data);
+ g_free(pskfile);
+ g_free(dhparams);
+ return rv;
+}
+
+
+static void
+qcrypto_tls_creds_psk_unload(QCryptoTLSCredsPSK *creds)
+{
+ if (creds->parent_obj.endpoint == QCRYPTO_TLS_CREDS_ENDPOINT_CLIENT) {
+ if (creds->data.client) {
+ gnutls_psk_free_client_credentials(creds->data.client);
+ creds->data.client = NULL;
+ }
+ } else {
+ if (creds->data.server) {
+ gnutls_psk_free_server_credentials(creds->data.server);
+ creds->data.server = NULL;
+ }
+ }
+ if (creds->parent_obj.dh_params) {
+ gnutls_dh_params_deinit(creds->parent_obj.dh_params);
+ creds->parent_obj.dh_params = NULL;
+ }
+}
+
+#else /* ! CONFIG_GNUTLS */
+
+
+static void
+qcrypto_tls_creds_psk_load(QCryptoTLSCredsPSK *creds G_GNUC_UNUSED,
+ Error **errp)
+{
+ error_setg(errp, "TLS credentials support requires GNUTLS");
+}
+
+
+static void
+qcrypto_tls_creds_psk_unload(QCryptoTLSCredsPSK *creds G_GNUC_UNUSED)
+{
+ /* nada */
+}
+
+
+#endif /* ! CONFIG_GNUTLS */
+
+
+static void
+qcrypto_tls_creds_psk_prop_set_loaded(Object *obj,
+ bool value,
+ Error **errp)
+{
+ QCryptoTLSCredsPSK *creds = QCRYPTO_TLS_CREDS_PSK(obj);
+
+ if (value) {
+ qcrypto_tls_creds_psk_load(creds, errp);
+ } else {
+ qcrypto_tls_creds_psk_unload(creds);
+ }
+}
+
+
+#ifdef CONFIG_GNUTLS
+
+
+static bool
+qcrypto_tls_creds_psk_prop_get_loaded(Object *obj,
+ Error **errp G_GNUC_UNUSED)
+{
+ QCryptoTLSCredsPSK *creds = QCRYPTO_TLS_CREDS_PSK(obj);
+
+ if (creds->parent_obj.endpoint == QCRYPTO_TLS_CREDS_ENDPOINT_SERVER) {
+ return creds->data.server != NULL;
+ } else {
+ return creds->data.client != NULL;
+ }
+}
+
+
+#else /* ! CONFIG_GNUTLS */
+
+
+static bool
+qcrypto_tls_creds_psk_prop_get_loaded(Object *obj G_GNUC_UNUSED,
+ Error **errp G_GNUC_UNUSED)
+{
+ return false;
+}
+
+
+#endif /* ! CONFIG_GNUTLS */
+
+
+static void
+qcrypto_tls_creds_psk_complete(UserCreatable *uc, Error **errp)
+{
+ object_property_set_bool(OBJECT(uc), true, "loaded", errp);
+}
+
+
+static void
+qcrypto_tls_creds_psk_finalize(Object *obj)
+{
+ QCryptoTLSCredsPSK *creds = QCRYPTO_TLS_CREDS_PSK(obj);
+
+ qcrypto_tls_creds_psk_unload(creds);
+}
+
+static void
+qcrypto_tls_creds_psk_prop_set_username(Object *obj,
+ const char *value,
+ Error **errp G_GNUC_UNUSED)
+{
+ QCryptoTLSCredsPSK *creds = QCRYPTO_TLS_CREDS_PSK(obj);
+
+ creds->username = g_strdup(value);
+}
+
+
+static char *
+qcrypto_tls_creds_psk_prop_get_username(Object *obj,
+ Error **errp G_GNUC_UNUSED)
+{
+ QCryptoTLSCredsPSK *creds = QCRYPTO_TLS_CREDS_PSK(obj);
+
+ return g_strdup(creds->username);
+}
+
+static void
+qcrypto_tls_creds_psk_class_init(ObjectClass *oc, void *data)
+{
+ UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
+
+ ucc->complete = qcrypto_tls_creds_psk_complete;
+
+ object_class_property_add_bool(oc, "loaded",
+ qcrypto_tls_creds_psk_prop_get_loaded,
+ qcrypto_tls_creds_psk_prop_set_loaded,
+ NULL);
+ object_class_property_add_str(oc, "username",
+ qcrypto_tls_creds_psk_prop_get_username,
+ qcrypto_tls_creds_psk_prop_set_username,
+ NULL);
+}
+
+
+static const TypeInfo qcrypto_tls_creds_psk_info = {
+ .parent = TYPE_QCRYPTO_TLS_CREDS,
+ .name = TYPE_QCRYPTO_TLS_CREDS_PSK,
+ .instance_size = sizeof(QCryptoTLSCredsPSK),
+ .instance_finalize = qcrypto_tls_creds_psk_finalize,
+ .class_size = sizeof(QCryptoTLSCredsPSKClass),
+ .class_init = qcrypto_tls_creds_psk_class_init,
+ .interfaces = (InterfaceInfo[]) {
+ { TYPE_USER_CREATABLE },
+ { }
+ }
+};
+
+
+static void
+qcrypto_tls_creds_psk_register_types(void)
+{
+ type_register_static(&qcrypto_tls_creds_psk_info);
+}
+
+
+type_init(qcrypto_tls_creds_psk_register_types);
diff --git a/crypto/tlssession.c b/crypto/tlssession.c
index 96a02deb69..aed754bb83 100644
--- a/crypto/tlssession.c
+++ b/crypto/tlssession.c
@@ -21,6 +21,7 @@
#include "qemu/osdep.h"
#include "crypto/tlssession.h"
#include "crypto/tlscredsanon.h"
+#include "crypto/tlscredspsk.h"
#include "crypto/tlscredsx509.h"
#include "qapi/error.h"
#include "qemu/acl.h"
@@ -162,6 +163,39 @@ qcrypto_tls_session_new(QCryptoTLSCreds *creds,
gnutls_strerror(ret));
goto error;
}
+ } else if (object_dynamic_cast(OBJECT(creds),
+ TYPE_QCRYPTO_TLS_CREDS_PSK)) {
+ QCryptoTLSCredsPSK *pcreds = QCRYPTO_TLS_CREDS_PSK(creds);
+ char *prio;
+
+ if (creds->priority != NULL) {
+ prio = g_strdup_printf("%s:+PSK:+DHE-PSK", creds->priority);
+ } else {
+ prio = g_strdup(CONFIG_TLS_PRIORITY ":+PSK:+DHE-PSK");
+ }
+
+ ret = gnutls_priority_set_direct(session->handle, prio, NULL);
+ if (ret < 0) {
+ error_setg(errp, "Unable to set TLS session priority %s: %s",
+ prio, gnutls_strerror(ret));
+ g_free(prio);
+ goto error;
+ }
+ g_free(prio);
+ if (creds->endpoint == QCRYPTO_TLS_CREDS_ENDPOINT_SERVER) {
+ ret = gnutls_credentials_set(session->handle,
+ GNUTLS_CRD_PSK,
+ pcreds->data.server);
+ } else {
+ ret = gnutls_credentials_set(session->handle,
+ GNUTLS_CRD_PSK,
+ pcreds->data.client);
+ }
+ if (ret < 0) {
+ error_setg(errp, "Cannot set session credentials: %s",
+ gnutls_strerror(ret));
+ goto error;
+ }
} else if (object_dynamic_cast(OBJECT(creds),
TYPE_QCRYPTO_TLS_CREDS_X509)) {
QCryptoTLSCredsX509 *tcreds = QCRYPTO_TLS_CREDS_X509(creds);
@@ -353,6 +387,10 @@ qcrypto_tls_session_check_credentials(QCryptoTLSSession *session,
TYPE_QCRYPTO_TLS_CREDS_ANON)) {
trace_qcrypto_tls_session_check_creds(session, "nop");
return 0;
+ } else if (object_dynamic_cast(OBJECT(session->creds),
+ TYPE_QCRYPTO_TLS_CREDS_PSK)) {
+ trace_qcrypto_tls_session_check_creds(session, "nop");
+ return 0;
} else if (object_dynamic_cast(OBJECT(session->creds),
TYPE_QCRYPTO_TLS_CREDS_X509)) {
if (session->creds->verifyPeer) {
diff --git a/crypto/trace-events b/crypto/trace-events
index e589990359..597389b73c 100644
--- a/crypto/trace-events
+++ b/crypto/trace-events
@@ -7,6 +7,9 @@ qcrypto_tls_creds_get_path(void *creds, const char *filename, const char *path)
# crypto/tlscredsanon.c
qcrypto_tls_creds_anon_load(void *creds, const char *dir) "TLS creds anon load creds=%p dir=%s"
+# crypto/tlscredspsk.c
+qcrypto_tls_creds_psk_load(void *creds, const char *dir) "TLS creds psk load creds=%p dir=%s"
+
# crypto/tlscredsx509.c
qcrypto_tls_creds_x509_load(void *creds, const char *dir) "TLS creds x509 load creds=%p dir=%s"
qcrypto_tls_creds_x509_check_basic_constraints(void *creds, const char *file, int status) "TLS creds x509 check basic constraints creds=%p file=%s status=%d"
diff --git a/include/crypto/tlscredspsk.h b/include/crypto/tlscredspsk.h
new file mode 100644
index 0000000000..6bc2158ea9
--- /dev/null
+++ b/include/crypto/tlscredspsk.h
@@ -0,0 +1,106 @@
+/*
+ * QEMU crypto TLS Pre-Shared Key (PSK) support
+ *
+ * Copyright (c) 2018 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef QCRYPTO_TLSCREDSPSK_H
+#define QCRYPTO_TLSCREDSPSK_H
+
+#include "crypto/tlscreds.h"
+
+#define TYPE_QCRYPTO_TLS_CREDS_PSK "tls-creds-psk"
+#define QCRYPTO_TLS_CREDS_PSK(obj) \
+ OBJECT_CHECK(QCryptoTLSCredsPSK, (obj), TYPE_QCRYPTO_TLS_CREDS_PSK)
+
+typedef struct QCryptoTLSCredsPSK QCryptoTLSCredsPSK;
+typedef struct QCryptoTLSCredsPSKClass QCryptoTLSCredsPSKClass;
+
+#define QCRYPTO_TLS_CREDS_PSKFILE "keys.psk"
+
+/**
+ * QCryptoTLSCredsPSK:
+ *
+ * The QCryptoTLSCredsPSK object provides a representation
+ * of the Pre-Shared Key credential used to perform a TLS handshake.
+ *
+ * This is a user creatable object, which can be instantiated
+ * via object_new_propv():
+ *
+ * <example>
+ * <title>Creating TLS-PSK credential objects in code</title>
+ * <programlisting>
+ * Object *obj;
+ * Error *err = NULL;
+ * obj = object_new_propv(TYPE_QCRYPTO_TLS_CREDS_PSK,
+ * "tlscreds0",
+ * &err,
+ * "dir", "/path/to/dir",
+ * "endpoint", "client",
+ * NULL);
+ * </programlisting>
+ * </example>
+ *
+ * Or via QMP:
+ *
+ * <example>
+ * <title>Creating TLS-PSK credential objects via QMP</title>
+ * <programlisting>
+ * {
+ * "execute": "object-add", "arguments": {
+ * "id": "tlscreds0",
+ * "qom-type": "tls-creds-psk",
+ * "props": {
+ * "dir": "/path/to/dir",
+ * "endpoint": "client",
+ * }
+ * }
+ * }
+ * </programlisting>
+ * </example>
+ *
+ * Or via the CLI:
+ *
+ * <example>
+ * <title>Creating TLS-PSK credential objects via CLI</title>
+ * <programlisting>
+ * qemu-system-x86_64 -object tls-creds-psk,id=tlscreds0,\
+ * endpoint=client,dir=/path/to/dir[,username=qemu]
+ * </programlisting>
+ * </example>
+ *
+ * The PSK file can be created and managed using psktool.
+ */
+
+struct QCryptoTLSCredsPSK {
+ QCryptoTLSCreds parent_obj;
+ char *username;
+#ifdef CONFIG_GNUTLS
+ union {
+ gnutls_psk_server_credentials_t server;
+ gnutls_psk_client_credentials_t client;
+ } data;
+#endif
+};
+
+
+struct QCryptoTLSCredsPSKClass {
+ QCryptoTLSCredsClass parent_class;
+};
+
+
+#endif /* QCRYPTO_TLSCREDSPSK_H */
diff --git a/qemu-doc.texi b/qemu-doc.texi
index 282bc3dc35..a4f9373699 100644
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -1262,6 +1262,7 @@ The recommendation is for the server to keep its certificates in either
* tls_generate_server::
* tls_generate_client::
* tls_creds_setup::
+* tls_psk::
@end menu
@node tls_generate_ca
@subsection Setup the Certificate Authority
@@ -1510,6 +1511,42 @@ example with VNC:
$QEMU -vnc 0.0.0.0:0,tls-creds=tls0
@end example
+@node tls_psk
+@subsection TLS Pre-Shared Keys (PSK)
+
+Instead of using certificates, you may also use TLS Pre-Shared Keys
+(TLS-PSK). This can be simpler to set up than certificates but is
+less scalable.
+
+Use the GnuTLS @code{psktool} program to generate a @code{keys.psk}
+file containing one or more usernames and random keys:
+
+@example
+mkdir -m 0700 /tmp/keys
+psktool -u rich -p /tmp/keys/keys.psk
+@end example
+
+TLS-enabled servers such as qemu-nbd can use this directory like so:
+
+@example
+qemu-nbd \
+ -t -x / \
+ --object tls-creds-psk,id=tls0,endpoint=server,dir=/tmp/keys \
+ --tls-creds tls0 \
+ image.qcow2
+@end example
+
+When connecting from a qemu-based client you must specify the
+directory containing @code{keys.psk} and an optional @var{username}
+(defaults to ``qemu''):
+
+@example
+qemu-img info \
+ --object tls-creds-psk,id=tls0,dir=/tmp/keys,username=rich,endpoint=client \
+ --image-opts \
+ file.driver=nbd,file.host=localhost,file.port=10809,file.tls-creds=tls0,file.export=/
+@end example
+
@node gdb_usage
@section GDB usage
diff --git a/qemu-options.hx b/qemu-options.hx
index d5b0c26e8e..afc5e6528f 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4099,6 +4099,30 @@ expensive operation that consumes random pool entropy, so it is
recommended that a persistent set of parameters be generated
upfront and saved.
+@item -object tls-creds-psk,id=@var{id},endpoint=@var{endpoint},dir=@var{/path/to/keys/dir}[,username=@var{username}]
+
+Creates a TLS Pre-Shared Keys (PSK) credentials object, which can be used to provide
+TLS support on network backends. The @option{id} parameter is a unique
+ID which network backends will use to access the credentials. The
+@option{endpoint} is either @option{server} or @option{client} depending
+on whether the QEMU network backend that uses the credentials will be
+acting as a client or as a server. For clients only, @option{username}
+is the username which will be sent to the server. If omitted
+it defaults to ``qemu''.
+
+The @var{dir} parameter tells QEMU where to find the keys file.
+It is called ``@var{dir}/keys.psk'' and contains ``username:key''
+pairs. This file can most easily be created using the GnuTLS
+@code{psktool} program.
+
+For server endpoints, @var{dir} may also contain a file
+@var{dh-params.pem} providing diffie-hellman parameters to use
+for the TLS server. If the file is missing, QEMU will generate
+a set of DH parameters at startup. This is a computationally
+expensive operation that consumes random pool entropy, so it is
+recommended that a persistent set of parameters be generated
+upfront and saved.
+
@item -object tls-creds-x509,id=@var{id},endpoint=@var{endpoint},dir=@var{/path/to/cred/dir},priority=@var{priority},verify-peer=@var{on|off},passwordid=@var{id}
Creates a TLS anonymous credentials object, which can be used to provide
--
2.16.2
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