Composer: Do not send 'Autocrypt' headers larger than 10KB

The Autocrypt specification has this limit. See:
https://autocrypt.org/level1.html#id74

Related to https://gitlab.gnome.org/GNOME/evolution/-/issues/375

src/composer/e-msg-composer.c

@@ -7016,6 +7016,7 @@ void
 e_msg_composer_check_autocrypt (EMsgComposer *composer,
 				CamelMimeMessage *original_message)
 {
+	EAlertBar *alert_bar;
 	gchar *from_email = NULL;
 	gchar *keyid = NULL;
 	gboolean send_public_key = FALSE;
@@ -7028,6 +7029,10 @@ e_msg_composer_check_autocrypt (EMsgComposer *composer,
 
 	e_msg_composer_remove_header (composer, "Autocrypt");
 
+	alert_bar = e_html_editor_get_alert_bar (e_msg_composer_get_editor (composer));
+	if (alert_bar)
+		e_alert_bar_remove_alert_by_tag (alert_bar, "mail-composer:info-autocrypt-header-too-large");
+
 	if (gtk_toggle_action_get_active (GTK_TOGGLE_ACTION (ACTION (SMIME_SIGN))) ||
 	    gtk_toggle_action_get_active (GTK_TOGGLE_ACTION (ACTION (SMIME_ENCRYPT)))) {
 		/* Autocrypt is about GPG, thus ignore it when the user uses S/MIME */
@@ -7094,7 +7099,13 @@ e_msg_composer_check_autocrypt (EMsgComposer *composer,
 			g_string_append (value, "; keydata=");
 			g_string_append (value, keydata);
 
-			e_msg_composer_add_header (composer, "Autocrypt", value->str);
+			/* Ignore headers above 10KB in size. See:
+			   https://autocrypt.org/level1.html#id74 */
+			if (value->len <= 10240)
+				e_msg_composer_add_header (composer, "Autocrypt", value->str);
+			else
+				e_alert_submit (E_ALERT_SINK (e_msg_composer_get_editor (composer)),
+					"mail-composer:info-autocrypt-header-too-large", from_email, NULL);
 
 			g_string_free (value, TRUE);
 		}

src/composer/mail-composer.error.xml

@@ -158,4 +158,9 @@ Detailed error: {0}</_secondary>
    <_primary>Message Redirection</_primary>
    <_secondary>This message is a redirection, which allows you to change the recipients, subject and other message attributes, but not the contents of the message.</_secondary>
  </error>
+
+ <error id="info-autocrypt-header-too-large" type="info">
+   <_primary>Not adding OpenPGP public key into the mail.</_primary>
+   <_secondary>The OpenPGP public key for “{0}” is too large for the transfer.</_secondary>
+ </error>
 </error-list>

src/e-util/e-alert-bar.c

@@ -542,6 +542,27 @@ e_alert_bar_clear (EAlertBar *alert_bar)
 		alert_bar_response_close (alert);
 }
 
+gboolean
+e_alert_bar_remove_alert_by_tag (EAlertBar *alert_bar,
+				 const gchar *tag)
+{
+	GList *link;
+
+	g_return_val_if_fail (E_IS_ALERT_BAR (alert_bar), FALSE);
+	g_return_val_if_fail (tag != NULL, FALSE);
+
+	for (link = g_queue_peek_head_link (&alert_bar->priv->alerts); link; link = g_list_next (link)) {
+		EAlert *alert = link->data;
+
+		if (g_strcmp0 (tag, e_alert_get_tag (alert)) == 0) {
+			alert_bar_response_close (alert);
+			return TRUE;
+		}
+	}
+
+	return FALSE;
+}
+
 typedef struct {
 	gboolean found;
 	EAlert *looking_for;

src/e-util/e-alert-bar.h

@@ -65,6 +65,8 @@ GtkWidget *	e_alert_bar_new			(void);
 void		e_alert_bar_clear		(EAlertBar *alert_bar);
 void		e_alert_bar_add_alert		(EAlertBar *alert_bar,
 						 EAlert *alert);
+gboolean	e_alert_bar_remove_alert_by_tag	(EAlertBar *alert_bar,
+						 const gchar *tag);
 gboolean	e_alert_bar_close_alert		(EAlertBar *alert_bar);
 void		e_alert_bar_submit_alert	(EAlertBar *alert_bar,
 						 EAlert *alert);

src/e-util/e-alert.c

@@ -790,6 +790,14 @@ e_alert_new_array (const gchar *tag,
 	return g_object_new (E_TYPE_ALERT, "tag", tag, "args", args, NULL);
 }
 
+const gchar *
+e_alert_get_tag (EAlert *alert)
+{
+	g_return_val_if_fail (E_IS_ALERT (alert), NULL);
+
+	return alert->priv->tag;
+}
+
 gint
 e_alert_get_default_response (EAlert *alert)
 {

src/e-util/e-alert.h

@@ -86,6 +86,7 @@ EAlert *	e_alert_new_valist		(const gchar *tag,
 						 va_list va);
 EAlert *	e_alert_new_array		(const gchar *tag,
 						 GPtrArray *args);
+const gchar *	e_alert_get_tag			(EAlert *alert);
 gint		e_alert_get_default_response	(EAlert *alert);
 void		e_alert_set_default_response	(EAlert *alert,
 						 gint response_id);

src/e-util/e-html-editor.c

@@ -2476,3 +2476,21 @@ e_html_editor_clear_alerts (EHTMLEditor *editor)
 	if (editor->priv->alert_bar)
 		e_alert_bar_clear (E_ALERT_BAR (editor->priv->alert_bar));
 }
+
+/**
+ * e_html_editor_get_alert_bar:
+ * @editor: an #EHTMLEditor
+ *
+ * Returns an #EAlertBar used by the @editor.
+ *
+ * Returns: (transfer none) (nullable): an #EAlertBar used by the @editor
+ *
+ * Since: 3.50
+ **/
+EAlertBar *
+e_html_editor_get_alert_bar (EHTMLEditor *editor)
+{
+	g_return_val_if_fail (E_IS_HTML_EDITOR (editor), NULL);
+
+	return editor->priv->alert_bar ? E_ALERT_BAR (editor->priv->alert_bar) : NULL;
+}

src/e-util/e-html-editor.h

@@ -29,6 +29,7 @@
 #include <e-util/e-action-combo-box.h>
 #include <e-util/e-activity.h>
 #include <e-util/e-activity-bar.h>
+#include <e-util/e-alert-bar.h>
 #include <e-util/e-content-editor.h>
 #include <e-util/e-focus-tracker.h>
 
@@ -142,6 +143,7 @@ void		e_html_editor_remove_all_cid_parts
 CamelMimePart * e_html_editor_ref_cid_part	(EHTMLEditor *editor,
 						 const gchar *cid_uri);
 void		e_html_editor_clear_alerts	(EHTMLEditor *editor);
+EAlertBar *	e_html_editor_get_alert_bar	(EHTMLEditor *editor);
 EActionComboBox *
 		e_html_editor_util_new_mode_combobox
 						(void);