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qemu/crypto/tlssession.c
Daniel P. Berrange a1c5e949dd crypto: allow default TLS priority to be chosen at build time 
Modern gnutls can use a global config file to control the
crypto priority settings for TLS connections. For example
the priority string "@SYSTEM" instructs gnutls to find the
priority setting named "SYSTEM" in the global config file.

Latest gnutls GIT codebase gained the ability to reference
multiple priority strings in the config file, with the first
one that is found to existing winning. This means it is now
possible to configure QEMU out of the box with a default
priority of "@QEMU,SYSTEM", which says to look for the
settings "QEMU" first, and if not found, use the "SYSTEM"
settings.

To make use of this facility, we introduce the ability to
set the QEMU default priority at build time via a new
configure argument.  It is anticipated that distro vendors
will set this when building QEMU to a suitable value for
use with distro crypto policy setup. eg current Fedora
would run

 ./configure --tls-priority=@SYSTEM

while future Fedora would run

 ./configure --tls-priority=@QEMU,SYSTEM

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
2016-07-04 15:53:19 +01:00

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/*
* QEMU crypto TLS session support
*
* Copyright (c) 2015 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/tlssession.h"
#include "crypto/tlscredsanon.h"
#include "crypto/tlscredsx509.h"
#include "qapi/error.h"
#include "qemu/acl.h"
#include "trace.h"
#ifdef CONFIG_GNUTLS
#include <gnutls/x509.h>
struct QCryptoTLSSession {
QCryptoTLSCreds *creds;
gnutls_session_t handle;
char *hostname;
char *aclname;
bool handshakeComplete;
QCryptoTLSSessionWriteFunc writeFunc;
QCryptoTLSSessionReadFunc readFunc;
void *opaque;
char *peername;
};
void
qcrypto_tls_session_free(QCryptoTLSSession *session)
{
if (!session) {
return;
}
gnutls_deinit(session->handle);
g_free(session->hostname);
g_free(session->peername);
g_free(session->aclname);
object_unref(OBJECT(session->creds));
g_free(session);
}
static ssize_t
qcrypto_tls_session_push(void *opaque, const void *buf, size_t len)
{
QCryptoTLSSession *session = opaque;
if (!session->writeFunc) {
errno = EIO;
return -1;
};
return session->writeFunc(buf, len, session->opaque);
}
static ssize_t
qcrypto_tls_session_pull(void *opaque, void *buf, size_t len)
{
QCryptoTLSSession *session = opaque;
if (!session->readFunc) {
errno = EIO;
return -1;
};
return session->readFunc(buf, len, session->opaque);
}
QCryptoTLSSession *
qcrypto_tls_session_new(QCryptoTLSCreds *creds,
const char *hostname,
const char *aclname,
QCryptoTLSCredsEndpoint endpoint,
Error **errp)
{
QCryptoTLSSession *session;
int ret;
session = g_new0(QCryptoTLSSession, 1);
trace_qcrypto_tls_session_new(
session, creds, hostname ? hostname : "<none>",
aclname ? aclname : "<none>", endpoint);
if (hostname) {
session->hostname = g_strdup(hostname);
}
if (aclname) {
session->aclname = g_strdup(aclname);
}
session->creds = creds;
object_ref(OBJECT(creds));
if (creds->endpoint != endpoint) {
error_setg(errp, "Credentials endpoint doesn't match session");
goto error;
}
if (endpoint == QCRYPTO_TLS_CREDS_ENDPOINT_SERVER) {
ret = gnutls_init(&session->handle, GNUTLS_SERVER);
} else {
ret = gnutls_init(&session->handle, GNUTLS_CLIENT);
}
if (ret < 0) {
error_setg(errp, "Cannot initialize TLS session: %s",
gnutls_strerror(ret));
goto error;
}
if (object_dynamic_cast(OBJECT(creds),
TYPE_QCRYPTO_TLS_CREDS_ANON)) {
QCryptoTLSCredsAnon *acreds = QCRYPTO_TLS_CREDS_ANON(creds);
char *prio;
if (creds->priority != NULL) {
prio = g_strdup_printf("%s:+ANON-DH", creds->priority);
} else {
prio = g_strdup(CONFIG_TLS_PRIORITY ":+ANON-DH");
}
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_ANON,
acreds->data.server);
} else {
ret = gnutls_credentials_set(session->handle,
GNUTLS_CRD_ANON,
acreds->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);
const char *prio = creds->priority;
if (!prio) {
prio = CONFIG_TLS_PRIORITY;
}
ret = gnutls_priority_set_direct(session->handle, prio, NULL);
if (ret < 0) {
error_setg(errp, "Cannot set default TLS session priority %s: %s",
prio, gnutls_strerror(ret));
goto error;
}
ret = gnutls_credentials_set(session->handle,
GNUTLS_CRD_CERTIFICATE,
tcreds->data);
if (ret < 0) {
error_setg(errp, "Cannot set session credentials: %s",
gnutls_strerror(ret));
goto error;
}
if (creds->endpoint == QCRYPTO_TLS_CREDS_ENDPOINT_SERVER) {
/* This requests, but does not enforce a client cert.
* The cert checking code later does enforcement */
gnutls_certificate_server_set_request(session->handle,
GNUTLS_CERT_REQUEST);
}
} else {
error_setg(errp, "Unsupported TLS credentials type %s",
object_get_typename(OBJECT(creds)));
goto error;
}
gnutls_transport_set_ptr(session->handle, session);
gnutls_transport_set_push_function(session->handle,
qcrypto_tls_session_push);
gnutls_transport_set_pull_function(session->handle,
qcrypto_tls_session_pull);
return session;
error:
qcrypto_tls_session_free(session);
return NULL;
}
static int
qcrypto_tls_session_check_certificate(QCryptoTLSSession *session,
Error **errp)
{
int ret;
unsigned int status;
const gnutls_datum_t *certs;
unsigned int nCerts, i;
time_t now;
gnutls_x509_crt_t cert = NULL;
now = time(NULL);
if (now == ((time_t)-1)) {
error_setg_errno(errp, errno, "Cannot get current time");
return -1;
}
ret = gnutls_certificate_verify_peers2(session->handle, &status);
if (ret < 0) {
error_setg(errp, "Verify failed: %s", gnutls_strerror(ret));
return -1;
}
if (status != 0) {
const char *reason = "Invalid certificate";
if (status & GNUTLS_CERT_INVALID) {
reason = "The certificate is not trusted";
}
if (status & GNUTLS_CERT_SIGNER_NOT_FOUND) {
reason = "The certificate hasn't got a known issuer";
}
if (status & GNUTLS_CERT_REVOKED) {
reason = "The certificate has been revoked";
}
if (status & GNUTLS_CERT_INSECURE_ALGORITHM) {
reason = "The certificate uses an insecure algorithm";
}
error_setg(errp, "%s", reason);
return -1;
}
certs = gnutls_certificate_get_peers(session->handle, &nCerts);
if (!certs) {
error_setg(errp, "No certificate peers");
return -1;
}
for (i = 0; i < nCerts; i++) {
ret = gnutls_x509_crt_init(&cert);
if (ret < 0) {
error_setg(errp, "Cannot initialize certificate: %s",
gnutls_strerror(ret));
return -1;
}
ret = gnutls_x509_crt_import(cert, &certs[i], GNUTLS_X509_FMT_DER);
if (ret < 0) {
error_setg(errp, "Cannot import certificate: %s",
gnutls_strerror(ret));
goto error;
}
if (gnutls_x509_crt_get_expiration_time(cert) < now) {
error_setg(errp, "The certificate has expired");
goto error;
}
if (gnutls_x509_crt_get_activation_time(cert) > now) {
error_setg(errp, "The certificate is not yet activated");
goto error;
}
if (gnutls_x509_crt_get_activation_time(cert) > now) {
error_setg(errp, "The certificate is not yet activated");
goto error;
}
if (i == 0) {
size_t dnameSize = 1024;
session->peername = g_malloc(dnameSize);
requery:
ret = gnutls_x509_crt_get_dn(cert, session->peername, &dnameSize);
if (ret < 0) {
if (ret == GNUTLS_E_SHORT_MEMORY_BUFFER) {
session->peername = g_realloc(session->peername,
dnameSize);
goto requery;
}
error_setg(errp, "Cannot get client distinguished name: %s",
gnutls_strerror(ret));
goto error;
}
if (session->aclname) {
qemu_acl *acl = qemu_acl_find(session->aclname);
int allow;
if (!acl) {
error_setg(errp, "Cannot find ACL %s",
session->aclname);
goto error;
}
allow = qemu_acl_party_is_allowed(acl, session->peername);
if (!allow) {
error_setg(errp, "TLS x509 ACL check for %s is denied",
session->peername);
goto error;
}
}
if (session->hostname) {
if (!gnutls_x509_crt_check_hostname(cert, session->hostname)) {
error_setg(errp,
"Certificate does not match the hostname %s",
session->hostname);
goto error;
}
}
}
gnutls_x509_crt_deinit(cert);
}
return 0;
error:
gnutls_x509_crt_deinit(cert);
return -1;
}
int
qcrypto_tls_session_check_credentials(QCryptoTLSSession *session,
Error **errp)
{
if (object_dynamic_cast(OBJECT(session->creds),
TYPE_QCRYPTO_TLS_CREDS_ANON)) {
return 0;
} else if (object_dynamic_cast(OBJECT(session->creds),
TYPE_QCRYPTO_TLS_CREDS_X509)) {
if (session->creds->verifyPeer) {
return qcrypto_tls_session_check_certificate(session,
errp);
} else {
return 0;
}
} else {
error_setg(errp, "Unexpected credential type %s",
object_get_typename(OBJECT(session->creds)));
return -1;
}
}
void
qcrypto_tls_session_set_callbacks(QCryptoTLSSession *session,
QCryptoTLSSessionWriteFunc writeFunc,
QCryptoTLSSessionReadFunc readFunc,
void *opaque)
{
session->writeFunc = writeFunc;
session->readFunc = readFunc;
session->opaque = opaque;
}
ssize_t
qcrypto_tls_session_write(QCryptoTLSSession *session,
const char *buf,
size_t len)
{
ssize_t ret = gnutls_record_send(session->handle, buf, len);
if (ret < 0) {
switch (ret) {
case GNUTLS_E_AGAIN:
errno = EAGAIN;
break;
case GNUTLS_E_INTERRUPTED:
errno = EINTR;
break;
default:
errno = EIO;
break;
}
ret = -1;
}
return ret;
}
ssize_t
qcrypto_tls_session_read(QCryptoTLSSession *session,
char *buf,
size_t len)
{
ssize_t ret = gnutls_record_recv(session->handle, buf, len);
if (ret < 0) {
switch (ret) {
case GNUTLS_E_AGAIN:
errno = EAGAIN;
break;
case GNUTLS_E_INTERRUPTED:
errno = EINTR;
break;
default:
errno = EIO;
break;
}
ret = -1;
}
return ret;
}
int
qcrypto_tls_session_handshake(QCryptoTLSSession *session,
Error **errp)
{
int ret = gnutls_handshake(session->handle);
if (ret == 0) {
session->handshakeComplete = true;
} else {
if (ret == GNUTLS_E_INTERRUPTED ||
ret == GNUTLS_E_AGAIN) {
ret = 1;
} else {
error_setg(errp, "TLS handshake failed: %s",
gnutls_strerror(ret));
ret = -1;
}
}
return ret;
}
QCryptoTLSSessionHandshakeStatus
qcrypto_tls_session_get_handshake_status(QCryptoTLSSession *session)
{
if (session->handshakeComplete) {
return QCRYPTO_TLS_HANDSHAKE_COMPLETE;
} else if (gnutls_record_get_direction(session->handle) == 0) {
return QCRYPTO_TLS_HANDSHAKE_RECVING;
} else {
return QCRYPTO_TLS_HANDSHAKE_SENDING;
}
}
int
qcrypto_tls_session_get_key_size(QCryptoTLSSession *session,
Error **errp)
{
gnutls_cipher_algorithm_t cipher;
int ssf;
cipher = gnutls_cipher_get(session->handle);
ssf = gnutls_cipher_get_key_size(cipher);
if (!ssf) {
error_setg(errp, "Cannot get TLS cipher key size");
return -1;
}
return ssf;
}
char *
qcrypto_tls_session_get_peer_name(QCryptoTLSSession *session)
{
if (session->peername) {
return g_strdup(session->peername);
}
return NULL;
}
#else /* ! CONFIG_GNUTLS */
QCryptoTLSSession *
qcrypto_tls_session_new(QCryptoTLSCreds *creds G_GNUC_UNUSED,
const char *hostname G_GNUC_UNUSED,
const char *aclname G_GNUC_UNUSED,
QCryptoTLSCredsEndpoint endpoint G_GNUC_UNUSED,
Error **errp)
{
error_setg(errp, "TLS requires GNUTLS support");
return NULL;
}
void
qcrypto_tls_session_free(QCryptoTLSSession *sess G_GNUC_UNUSED)
{
}
int
qcrypto_tls_session_check_credentials(QCryptoTLSSession *sess G_GNUC_UNUSED,
Error **errp)
{
error_setg(errp, "TLS requires GNUTLS support");
return -1;
}
void
qcrypto_tls_session_set_callbacks(
QCryptoTLSSession *sess G_GNUC_UNUSED,
QCryptoTLSSessionWriteFunc writeFunc G_GNUC_UNUSED,
QCryptoTLSSessionReadFunc readFunc G_GNUC_UNUSED,
void *opaque G_GNUC_UNUSED)
{
}
ssize_t
qcrypto_tls_session_write(QCryptoTLSSession *sess,
const char *buf,
size_t len)
{
errno = -EIO;
return -1;
}
ssize_t
qcrypto_tls_session_read(QCryptoTLSSession *sess,
char *buf,
size_t len)
{
errno = -EIO;
return -1;
}
int
qcrypto_tls_session_handshake(QCryptoTLSSession *sess,
Error **errp)
{
error_setg(errp, "TLS requires GNUTLS support");
return -1;
}
QCryptoTLSSessionHandshakeStatus
qcrypto_tls_session_get_handshake_status(QCryptoTLSSession *sess)
{
return QCRYPTO_TLS_HANDSHAKE_COMPLETE;
}
int
qcrypto_tls_session_get_key_size(QCryptoTLSSession *sess,
Error **errp)
{
error_setg(errp, "TLS requires GNUTLS support");
return -1;
}
char *
qcrypto_tls_session_get_peer_name(QCryptoTLSSession *sess)
{
return NULL;
}
#endif
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