crypto: introduce new module for handling TLS sessions

Introduce a QCryptoTLSSession object that will encapsulate
all the code for setting up and using a client/sever TLS
session. This isolates the code which depends on the gnutls
library, avoiding #ifdefs in the rest of the codebase, as
well as facilitating any possible future port to other TLS
libraries, if desired. It makes use of the previously
defined QCryptoTLSCreds object to access credentials to
use with the session. It also includes further unit tests
to validate the correctness of the TLS session handshake
and certificate validation. This is functionally equivalent
to the current TLS session handling code embedded in the
VNC server, and will obsolete it.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

2 files changed, 575 insertions, 0 deletions

diff --git a/crypto/Makefile.objs b/crypto/Makefile.objs
index 8f16b31..b2a0e0b 100644
--- a/crypto/Makefile.objs
+++ b/crypto/Makefile.objs
@@ -6,6 +6,7 @@ crypto-obj-y += cipher.o
 crypto-obj-y += tlscreds.o
 crypto-obj-y += tlscredsanon.o
 crypto-obj-y += tlscredsx509.o
+crypto-obj-y += tlssession.o
 
 # Let the userspace emulators avoid linking gnutls/etc
 crypto-aes-obj-y = aes.o
diff --git a/crypto/tlssession.c b/crypto/tlssession.c
new file mode 100644
index 0000000..ffc5c47
--- /dev/null
+++ b/crypto/tlssession.c
@@ -0,0 +1,574 @@
+/*
+ * 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 "crypto/tlssession.h"
+#include "crypto/tlscredsanon.h"
+#include "crypto/tlscredsx509.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);
+
+        ret = gnutls_priority_set_direct(session->handle,
+                                         "NORMAL:+ANON-DH", NULL);
+        if (ret < 0) {
+            error_setg(errp, "Unable to set TLS session priority: %s",
+                       gnutls_strerror(ret));
+            goto error;
+        }
+        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);
+
+        ret = gnutls_set_default_priority(session->handle);
+        if (ret < 0) {
+            error_setg(errp, "Cannot set default TLS session priority: %s",
+                       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);
+
+                error_setg(errp, "TLS x509 ACL check for %s is %s",
+                           session->peername, allow ? "allowed" : "denied");
+                if (!allow) {
+                    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