extensions: simplified requirements from send callback

The callback no longer needs to return the number of sent data;
they are now calculated by the caller.

Signed-off-by: Nikos Mavrogiannopoulos <nmav@redhat.com>

4 files changed, 27 insertions, 16 deletions

diff --git a/doc/cha-internals.texi b/doc/cha-internals.texi
index d368054712..532057d51a 100644
--- a/doc/cha-internals.texi
+++ b/doc/cha-internals.texi
@@ -246,7 +246,13 @@ The @funcintref{_foobar_recv_params} function is responsible for
 parsing incoming extension data (both in the client and server).
 
 The @funcintref{_foobar_send_params} function is responsible for
-sending extension data (both in the client and server).
+sending extension data (both in the client and server). It should
+append data to provided buffer and return a positive (or zero) number on
+success or a negative error code. Previous to 3.6.0 versions of GnuTLS required
+that function to return the number of bytes that were written. If zero
+is returned and no bytes are appended the extension will not be sent.
+If a zero byte extension is to be sent this function must return
+@code{GNUTLS_E_INT_RET_0}.
 
 If you receive length fields that don't match, return
 @code{GNUTLS_E_@-UNEXPECTED_@-PACKET_@-LENGTH}.  If you receive invalid
diff --git a/lib/errors.h b/lib/errors.h
index ab71b69b98..e0f6b906c2 100644
--- a/lib/errors.h
+++ b/lib/errors.h
@@ -28,9 +28,6 @@
 #include <mpi.h>
 #include <gnutls/x509.h>
 
-#define GNUTLS_E_INT_RET_0 -1251
-#define GNUTLS_E_INT_CHECK_AGAIN -1252
-
 #ifdef __FILE__
 #ifdef __LINE__
 #define gnutls_assert() _gnutls_assert_log( "ASSERT: %s[%s]:%d\n", __FILE__,__func__,__LINE__);
diff --git a/lib/extensions.c b/lib/extensions.c
index b4c2284f9a..bd4f933fb7 100644
--- a/lib/extensions.c
+++ b/lib/extensions.c
@@ -293,7 +293,8 @@ static
 int send_extension(gnutls_session_t session, const extension_entry_st *p,
 		   gnutls_buffer_st *extdata, gnutls_ext_parse_type_t parse_type)
 {
-	int size_pos, size, ret;
+	int size_pos, appended, ret;
+	size_t size_prev;
 
 	if (p->send_func == NULL)
 		return 0;
@@ -323,16 +324,23 @@ int send_extension(gnutls_session_t session, const extension_entry_st *p,
 	if (ret < 0)
 		return gnutls_assert_val(ret);
 
-	size = p->send_func(session, extdata);
+	size_prev = extdata->length;
+	ret = p->send_func(session, extdata);
+	if (ret < 0 && ret != GNUTLS_E_INT_RET_0) {
+		return gnutls_assert_val(ret);
+	}
+
 	/* returning GNUTLS_E_INT_RET_0 means to send an empty
 	 * extension of this type.
 	 */
-	if (size > 0 || size == GNUTLS_E_INT_RET_0) {
-		if (size == GNUTLS_E_INT_RET_0)
-			size = 0;
+	appended = extdata->length - size_prev;
+
+	if (appended > 0 || ret == GNUTLS_E_INT_RET_0) {
+		if (ret == GNUTLS_E_INT_RET_0)
+			appended = 0;
 
 		/* write the real size */
-		_gnutls_write_uint16(size,
+		_gnutls_write_uint16(appended,
 				     &extdata->data[size_pos]);
 
 		/* add this extension to the extension list
@@ -342,11 +350,8 @@ int send_extension(gnutls_session_t session, const extension_entry_st *p,
 
 		_gnutls_handshake_log
 			    ("EXT[%p]: Sending extension %s (%d bytes)\n",
-			     session, p->name, size);
-	} else if (size < 0) {
-		gnutls_assert();
-		return size;
-	} else if (size == 0)
+			     session, p->name, appended);
+	} else if (appended == 0)
 		extdata->length -= 4;	/* reset type and size */
 
 	return 0;
diff --git a/lib/includes/gnutls/gnutls.h.in b/lib/includes/gnutls/gnutls.h.in
index 80c0819fb6..9562785498 100644
--- a/lib/includes/gnutls/gnutls.h.in
+++ b/lib/includes/gnutls/gnutls.h.in
@@ -2939,7 +2939,10 @@ unsigned gnutls_fips140_mode_enabled(void);
 
 #define GNUTLS_E_UNIMPLEMENTED_FEATURE -1250
 
-
+/* Internal errors of the library; will never be returned
+ * to a calling application */
+#define GNUTLS_E_INT_RET_0 -1251
+#define GNUTLS_E_INT_CHECK_AGAIN -1252
 
 #define GNUTLS_E_APPLICATION_ERROR_MAX -65000
 #define GNUTLS_E_APPLICATION_ERROR_MIN -65500