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qemu/crypto/tlssession.c
Daniel P. Berrangé a2458b6f69 io: return 0 for EOF in TLS session read after shutdown 
GNUTLS takes a paranoid approach when seeing 0 bytes returned by the
underlying OS read() function. It will consider this an error and
return GNUTLS_E_PREMATURE_TERMINATION instead of propagating the 0
return value. It expects apps to arrange for clean termination at
the protocol level and not rely on seeing EOF from a read call to
detect shutdown. This is to harden apps against a malicious 3rd party
causing termination of the sockets layer.

This is unhelpful for the QEMU NBD code which does have a clean
protocol level shutdown, but still relies on seeing 0 from the I/O
channel read in the coroutine handling incoming replies.

The upshot is that when using a plain NBD connection shutdown is
silent, but when using TLS, the client spams the console with

  Cannot read from TLS channel: Broken pipe

The NBD connection has, however, called qio_channel_shutdown()
at this point to indicate that it is done with I/O. This gives
the opportunity to optimize the code such that when the channel
has been shutdown in the read direction, the error code
GNUTLS_E_PREMATURE_TERMINATION gets turned into a '0' return
instead of an error.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20181119134228.11031-1-berrange@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
2018-11-19 11:16:46 -06:00

644 lines
18 KiB
C
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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/tlscredspsk.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);
}
#define TLS_PRIORITY_ADDITIONAL_ANON "+ANON-DH"
#define TLS_PRIORITY_ADDITIONAL_PSK "+ECDHE-PSK:+DHE-PSK:+PSK"
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:%s",
creds->priority,
TLS_PRIORITY_ADDITIONAL_ANON);
} else {
prio = g_strdup(CONFIG_TLS_PRIORITY ":"
TLS_PRIORITY_ADDITIONAL_ANON);
}
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_PSK)) {
QCryptoTLSCredsPSK *pcreds = QCRYPTO_TLS_CREDS_PSK(creds);
char *prio;
if (creds->priority != NULL) {
prio = g_strdup_printf("%s:%s",
creds->priority,
TLS_PRIORITY_ADDITIONAL_PSK);
} else {
prio = g_strdup(CONFIG_TLS_PRIORITY ":"
TLS_PRIORITY_ADDITIONAL_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);
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)) {
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) {
int ret = qcrypto_tls_session_check_certificate(session,
errp);
trace_qcrypto_tls_session_check_creds(session,
ret == 0 ? "pass" : "fail");
return ret;
} else {
trace_qcrypto_tls_session_check_creds(session, "skip");
return 0;
}
} else {
trace_qcrypto_tls_session_check_creds(session, "error");
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;
case GNUTLS_E_PREMATURE_TERMINATION:
errno = ECONNABORTED;
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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