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>

1 files changed, 322 insertions, 0 deletions

diff --git a/include/crypto/tlssession.h b/include/crypto/tlssession.h
new file mode 100644
index 0000000..b38fe69
--- /dev/null
+++ b/include/crypto/tlssession.h
@@ -0,0 +1,322 @@
+/*
+ * 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/>.
+ *
+ */
+
+#ifndef QCRYPTO_TLS_SESSION_H__
+#define QCRYPTO_TLS_SESSION_H__
+
+#include "crypto/tlscreds.h"
+
+/**
+ * QCryptoTLSSession:
+ *
+ * The QCryptoTLSSession object encapsulates the
+ * logic to integrate with a TLS providing library such
+ * as GNUTLS, to setup and run TLS sessions.
+ *
+ * The API is designed such that it has no assumption about
+ * the type of transport it is running over. It may be a
+ * traditional TCP socket, or something else entirely. The
+ * only requirement is a full-duplex stream of some kind.
+ *
+ * <example>
+ *   <title>Using TLS session objects</title>
+ *   <programlisting>
+ * static ssize_t mysock_send(const char *buf, size_t len,
+ *                            void *opaque)
+ * {
+ *    int fd = GPOINTER_TO_INT(opaque);
+ *
+ *    return write(*fd, buf, len);
+ * }
+ *
+ * static ssize_t mysock_recv(const char *buf, size_t len,
+ *                            void *opaque)
+ * {
+ *    int fd = GPOINTER_TO_INT(opaque);
+ *
+ *    return read(*fd, buf, len);
+ * }
+ *
+ * static int mysock_run_tls(int sockfd,
+ *                           QCryptoTLSCreds *creds,
+ *                           Error *erp)
+ * {
+ *    QCryptoTLSSession *sess;
+ *
+ *    sess = qcrypto_tls_session_new(creds,
+ *                                   "vnc.example.com",
+ *                                   NULL,
+ *                                   QCRYPTO_TLS_CREDS_ENDPOINT_CLIENT,
+ *                                   errp);
+ *    if (sess == NULL) {
+ *       return -1;
+ *    }
+ *
+ *    qcrypto_tls_session_set_callbacks(sess,
+ *                                      mysock_send,
+ *                                      mysock_recv
+ *                                      GINT_TO_POINTER(fd));
+ *
+ *    while (1) {
+ *       if (qcrypto_tls_session_handshake(sess, errp) < 0) {
+ *           qcrypto_tls_session_free(sess);
+ *           return -1;
+ *       }
+ *
+ *       switch(qcrypto_tls_session_get_handshake_status(sess)) {
+ *       case QCRYPTO_TLS_HANDSHAKE_COMPLETE:
+ *           if (qcrypto_tls_session_check_credentials(sess, errp) < )) {
+ *               qcrypto_tls_session_free(sess);
+ *               return -1;
+ *           }
+ *           goto done;
+ *       case QCRYPTO_TLS_HANDSHAKE_RECVING:
+ *           ...wait for GIO_IN event on fd...
+ *           break;
+ *       case QCRYPTO_TLS_HANDSHAKE_SENDING:
+ *           ...wait for GIO_OUT event on fd...
+ *           break;
+ *       }
+ *    }
+ *   done:
+ *
+ *    ....send/recv payload data on sess...
+ *
+ *    qcrypto_tls_session_free(sess):
+ * }
+ *   </programlisting>
+ * </example>
+ */
+
+typedef struct QCryptoTLSSession QCryptoTLSSession;
+
+
+/**
+ * qcrypto_tls_session_new:
+ * @creds: pointer to a TLS credentials object
+ * @hostname: optional hostname to validate
+ * @aclname: optional ACL to validate peer credentials against
+ * @endpoint: role of the TLS session, client or server
+ * @errp: pointer to an uninitialized error object
+ *
+ * Create a new TLS session object that will be used to
+ * negotiate a TLS session over an arbitrary data channel.
+ * The session object can operate as either the server or
+ * client, according to the value of the @endpoint argument.
+ *
+ * For clients, the @hostname parameter should hold the full
+ * unmodified hostname as requested by the user. This will
+ * be used to verify the against the hostname reported in
+ * the server's credentials (aka x509 certificate).
+ *
+ * The @aclname parameter (optionally) specifies the name
+ * of an access control list that will be used to validate
+ * the peer's credentials. For x509 credentials, the ACL
+ * will be matched against the CommonName shown in the peer's
+ * certificate. If the session is acting as a server, setting
+ * an ACL will require that the client provide a validate
+ * x509 client certificate.
+ *
+ * After creating the session object, the I/O callbacks
+ * must be set using the qcrypto_tls_session_set_callbacks()
+ * method. A TLS handshake sequence must then be completed
+ * using qcrypto_tls_session_handshake(), before payload
+ * data is permitted to be sent/received.
+ *
+ * The session object must be released by calling
+ * qcrypto_tls_session_free() when no longer required
+ *
+ * Returns: a TLS session object, or NULL on error.
+ */
+QCryptoTLSSession *qcrypto_tls_session_new(QCryptoTLSCreds *creds,
+                                           const char *hostname,
+                                           const char *aclname,
+                                           QCryptoTLSCredsEndpoint endpoint,
+                                           Error **errp);
+
+/**
+ * qcrypto_tls_session_free:
+ * @sess: the TLS session object
+ *
+ * Release all memory associated with the TLS session
+ * object previously allocated by qcrypto_tls_session_new()
+ */
+void qcrypto_tls_session_free(QCryptoTLSSession *sess);
+
+/**
+ * qcrypto_tls_session_check_credentials:
+ * @sess: the TLS session object
+ * @errp: pointer to an uninitialized error object
+ *
+ * Validate the peer's credentials after a successful
+ * TLS handshake. It is an error to call this before
+ * qcrypto_tls_session_get_handshake_status() returns
+ * QCRYPTO_TLS_HANDSHAKE_COMPLETE
+ *
+ * Returns 0 if the credentials validated, -1 on error
+ */
+int qcrypto_tls_session_check_credentials(QCryptoTLSSession *sess,
+                                          Error **errp);
+
+typedef ssize_t (*QCryptoTLSSessionWriteFunc)(const char *buf,
+                                              size_t len,
+                                              void *opaque);
+typedef ssize_t (*QCryptoTLSSessionReadFunc)(char *buf,
+                                             size_t len,
+                                             void *opaque);
+
+/**
+ * qcrypto_tls_session_set_callbacks:
+ * @sess: the TLS session object
+ * @writeFunc: callback for sending data
+ * @readFunc: callback to receiving data
+ * @opaque: data to pass to callbacks
+ *
+ * Sets the callback functions that are to be used for sending
+ * and receiving data on the underlying data channel. Typically
+ * the callbacks to write/read to/from a TCP socket, but there
+ * is no assumption made about the type of channel used.
+ *
+ * The @writeFunc callback will be passed the encrypted
+ * data to send to the remote peer.
+ *
+ * The @readFunc callback will be passed a pointer to fill
+ * with encrypted data received from the remote peer
+ */
+void qcrypto_tls_session_set_callbacks(QCryptoTLSSession *sess,
+                                       QCryptoTLSSessionWriteFunc writeFunc,
+                                       QCryptoTLSSessionReadFunc readFunc,
+                                       void *opaque);
+
+/**
+ * qcrypto_tls_session_write:
+ * @sess: the TLS session object
+ * @buf: the plain text to send
+ * @len: the length of @buf
+ *
+ * Encrypt @len bytes of the data in @buf and send
+ * it to the remote peer using the callback previously
+ * registered with qcrypto_tls_session_set_callbacks()
+ *
+ * It is an error to call this before
+ * qcrypto_tls_session_get_handshake_status() returns
+ * QCRYPTO_TLS_HANDSHAKE_COMPLETE
+ *
+ * Returns: the number of bytes sent, or -1 on error
+ */
+ssize_t qcrypto_tls_session_write(QCryptoTLSSession *sess,
+                                  const char *buf,
+                                  size_t len);
+
+/**
+ * qcrypto_tls_session_read:
+ * @sess: the TLS session object
+ * @buf: to fill with plain text received
+ * @len: the length of @buf
+ *
+ * Receive up to @len bytes of data from the remote peer
+ * using the callback previously registered with
+ * qcrypto_tls_session_set_callbacks(), decrypt it and
+ * store it in @buf.
+ *
+ * It is an error to call this before
+ * qcrypto_tls_session_get_handshake_status() returns
+ * QCRYPTO_TLS_HANDSHAKE_COMPLETE
+ *
+ * Returns: the number of bytes received, or -1 on error
+ */
+ssize_t qcrypto_tls_session_read(QCryptoTLSSession *sess,
+                                 char *buf,
+                                 size_t len);
+
+/**
+ * qcrypto_tls_session_handshake:
+ * @sess: the TLS session object
+ * @errp: pointer to an uninitialized error object
+ *
+ * Start, or continue, a TLS handshake sequence. If
+ * the underlying data channel is non-blocking, then
+ * this method may return control before the handshake
+ * is complete. On non-blocking channels the
+ * qcrypto_tls_session_get_handshake_status() method
+ * should be used to determine whether the handshake
+ * has completed, or is waiting to send or receive
+ * data. In the latter cases, the caller should setup
+ * an event loop watch and call this method again
+ * once the underlying data channel is ready to read
+ * or write again
+ */
+int qcrypto_tls_session_handshake(QCryptoTLSSession *sess,
+                                  Error **errp);
+
+typedef enum {
+    QCRYPTO_TLS_HANDSHAKE_COMPLETE,
+    QCRYPTO_TLS_HANDSHAKE_SENDING,
+    QCRYPTO_TLS_HANDSHAKE_RECVING,
+} QCryptoTLSSessionHandshakeStatus;
+
+/**
+ * qcrypto_tls_session_get_handshake_status:
+ * @sess: the TLS session object
+ *
+ * Check the status of the TLS handshake. This
+ * is used with non-blocking data channels to
+ * determine whether the handshake is waiting
+ * to send or receive further data to/from the
+ * remote peer.
+ *
+ * Once this returns QCRYPTO_TLS_HANDSHAKE_COMPLETE
+ * it is permitted to send/receive payload data on
+ * the channel
+ */
+QCryptoTLSSessionHandshakeStatus
+qcrypto_tls_session_get_handshake_status(QCryptoTLSSession *sess);
+
+/**
+ * qcrypto_tls_session_get_key_size:
+ * @sess: the TLS session object
+ * @errp: pointer to an uninitialized error object
+ *
+ * Check the size of the data channel encryption key
+ *
+ * Returns: the length in bytes of the encryption key
+ * or -1 on error
+ */
+int qcrypto_tls_session_get_key_size(QCryptoTLSSession *sess,
+                                     Error **errp);
+
+/**
+ * qcrypto_tls_session_get_peer_name:
+ * @sess: the TLS session object
+ *
+ * Get the identified name of the remote peer. If the
+ * TLS session was negotiated using x509 certificate
+ * credentials, this will return the CommonName from
+ * the peer's certificate. If no identified name is
+ * available it will return NULL.
+ *
+ * The returned data must be released with g_free()
+ * when no longer required.
+ *
+ * Returns: the peer's name or NULL.
+ */
+char *qcrypto_tls_session_get_peer_name(QCryptoTLSSession *sess);
+
+#endif /* QCRYPTO_TLS_SESSION_H__ */