Initial draft of a TLS abstraction layer based on GNU TLS.

This adds a tls_t that looks a bit like a socket, but can turn
on and off tls. The idea would be to plug this into the xmpp_conn_t
and use it iff the connection is in TLS mode.

src/tls.c

@@ -0,0 +1,123 @@
+/* tls.c
+** libstrophe XMPP client library -- TLS abstraction header
+**
+** Copyright (C) 2005 OGG, LCC. All rights reserved.
+**
+**  This software is provided AS-IS with no warranty, either express
+**  or implied.
+**
+**  This software is distributed under license and may not be copied,
+**  modified or distributed except as expressly authorized under the
+**  terms of the license contained in the file LICENSE.txt in this
+**  distribution.
+*/
+
+#include <gnutls/gnutls.h>
+
+#include "common.h"
+#include "tls.h"
+#include "sock.h"
+
+struct _tls {
+    xmpp_ctx_t *ctx; /* do we need this? */
+    sock_t sock;
+    gnutls_session_t session;
+    gnutls_certificate_credentials_t cred;
+};
+
+void tls_initialize(void)
+{
+    /* initialize the GNU TLS global state */
+    gnutls_global_init();
+
+    /* TODO: wire in xmpp_ctx_t allocator somehow?
+       unfortunately in gnutls it's global, so we can
+       only do so much. */
+}
+
+void tls_shutdown(void)
+{
+    /* tear down the GNU TLS global state */
+    gnutls_global_deinit();
+}
+
+tls_t *tls_new(xmpp_ctx_t *ctx, sock_t sock)
+{
+    tls_t *tls = xmpp_alloc(ctx, sizeof(tls_t));
+    const int cert_type_priority[3] = { GNUTLS_CRT_X509,
+        GNUTLS_CRT_OPENPGP, 0 };
+
+    if (tls) {
+	tls->ctx = ctx;
+	tls->sock = sock;
+	gnutls_init(&tls->session, GNUTLS_CLIENT);
+
+	gnutls_certificate_allocate_credentials(&tls->cred);
+
+	gnutls_set_default_priority(tls->session);
+	gnutls_certificate_type_set_priority(tls->session, cert_type_priority);
+
+	/* fixme: this may require setting a callback on win32? */
+	gnutls_transport_set_ptr(tls->session, 
+		(gnutls_transport_ptr_t)sock);
+    }
+
+    return tls;
+}
+
+void tls_free(tls_t *tls)
+{
+    gnutls_deinit(tls->session);
+    gnutls_certificate_free_credentials(tls->cred);
+    xmpp_free(tls->ctx, tls);
+}
+
+int tls_setcredentials(tls_t *tls, const char *cafilename)
+{
+    int err;
+
+    /* set trusted credentials -- takes a .pem filename */
+    err = gnutls_certificate_set_x509_trust_file(tls->cred,
+	    cafilename, GNUTLS_X509_FMT_PEM);
+    if (err < 0) return err;
+
+    err = gnutls_credentials_set(tls->session, GNUTLS_CRD_CERTIFICATE, 
+	    tls->cred);
+
+    return err;
+}
+
+int tls_start(tls_t *tls)
+{
+    return gnutls_handshake(tls->session);
+}
+
+int tls_stop(tls_t *tls)
+{
+    return gnutls_bye(tls->session, GNUTLS_SHUT_RDWR);
+}
+
+int tls_error(tls_t *tls)
+{
+    /* todo: some kind of error polling/dump */
+    return 0;
+}
+
+int tls_read(tls_t *tls, void * const buff, const size_t len)
+{
+    int ret;
+
+    ret = gnutls_record_recv(tls->session, buff, len);
+
+    return ret;
+}
+
+int tls_write(tls_t *tls, const void * const buff, const size_t len)
+{
+    int ret;
+
+    ret = gnutls_record_send(tls->session, buff, len);
+
+    return ret;
+}
+

src/tls.h

@@ -0,0 +1,40 @@
+/* tls.h
+** libstrophe XMPP client library -- TLS abstraction header
+**
+** Copyright (C) 2005 OGG, LCC. All rights reserved.
+**
+**  This software is provided AS-IS with no warranty, either express
+**  or implied.
+**
+**  This software is distributed under license and may not be copied,
+**  modified or distributed except as expressly authorized under the
+**  terms of the license contained in the file LICENSE.txt in this
+**  distribution.
+*/
+
+#ifndef __LIBSTROPHE_TLS_H__
+#define __LIBSTROPHE_TLS_H__
+
+#include <gnutls/gnutls.h>
+#include "common.h"
+#include "sock.h"
+
+typedef struct _tls tls_t;
+
+void tls_initialize(void);
+void tls_shutdown(void);
+
+tls_t *tls_new(xmpp_ctx_t *ctx, sock_t sock);
+void tls_free(tls_t *tls);
+
+int tls_setcredentials(tls_t *tls, const char *cafilename);
+
+int tls_start(tls_t *tls);
+int tls_stop(tls_t *tls);
+
+int tls_error(tls_t *tls);
+
+int tls_read(tls_t *tls, void * const buff, const size_t len);
+int tls_write(tls_t *tls, const void * const buff, const size_t len);
+
+#endif /* __LIBSTROPHE_TLS_H__ */