src/xb-silo-export.c - main - githubmirror/libxmlb

src/xb-silo-export.c
296 строк8 KB
Richard Hughes
Prevent stack overflow from unbounded recursion in export
13 апр 2026, 20:41
13 апр 2026, 20:4179fdf66
/*
 * Copyright 2018 Richard Hughes <richard@hughsie.com>
 *
 * SPDX-License-Identifier: LGPL-2.1-or-later
 */

#define G_LOG_DOMAIN "XbSilo"

#include "config.h"

#include <gio/gio.h>

#include "xb-node-private.h"
#include "xb-silo-export-private.h"
#include "xb-silo-node.h"
#include "xb-string-private.h"

#define XB_SILO_EXPORT_MAX_DEPTH 100

typedef struct {
	GString *xml;
	XbNodeExportFlags flags;
	guint32 off;
	guint level;
} XbSiloExportHelper;

static gboolean
xb_silo_export_node(XbSilo *self, XbSiloExportHelper *helper, XbSiloNode *sn, GError **error)
{
	XbSiloNode *sn2;
	const gchar *element_name;

	helper->off = xb_silo_get_offset_for_node(self, sn);

	/* add start of opening tag */
	if (helper->flags & XB_NODE_EXPORT_FLAG_FORMAT_INDENT) {
		for (guint i = 0; i < helper->level; i++)
			g_string_append(helper->xml, "  ");
	}
	element_name = xb_silo_from_strtab(self, sn->element_name, error);
	if (element_name == NULL)
		return FALSE;
	g_string_append_printf(helper->xml, "<%s", element_name);

	/* add any attributes */
	for (guint8 i = 0; i < xb_silo_node_get_attr_count(sn); i++) {
		XbSiloNodeAttr *a = xb_silo_node_get_attr(sn, i);
		const gchar *name_unsafe;
		const gchar *value_unsafe;
		g_autofree gchar *name = NULL;
		g_autofree gchar *value = NULL;

		name_unsafe = xb_silo_from_strtab(self, a->attr_name, error);
		if (name_unsafe == NULL)
			return FALSE;
		name = xb_string_xml_escape(name_unsafe);

		value_unsafe = xb_silo_from_strtab(self, a->attr_value, error);
		if (value_unsafe == NULL)
			return FALSE;
		value = xb_string_xml_escape(value_unsafe);

		g_string_append_printf(helper->xml, " %s=\"%s\"", name, value);
	}

	/* collapse open/close tags together if no text or children */
	if (helper->flags & XB_NODE_EXPORT_FLAG_COLLAPSE_EMPTY &&
	    xb_silo_node_get_text_idx(sn) == XB_SILO_UNSET &&
	    xb_silo_get_child_node(self, sn, NULL) == NULL) {
		g_string_append(helper->xml, " />");

		/* offset by opening tag and single byte sentinel */
		helper->off += xb_silo_node_get_size(sn);
		sn2 = xb_silo_get_node(self, helper->off, error);
		if (sn2 == NULL)
			return FALSE;
		helper->off += xb_silo_node_get_size(sn2);
	} else {
		/* finish the opening tag and add any text if it exists */
		if (xb_silo_node_get_text_idx(sn) != XB_SILO_UNSET) {
			const gchar *text_unsafe;
			g_autofree gchar *text = NULL;

			text_unsafe =
			    xb_silo_from_strtab(self, xb_silo_node_get_text_idx(sn), error);
			if (text_unsafe == NULL)
				return FALSE;
			text = xb_string_xml_escape(text_unsafe);
			g_string_append(helper->xml, ">");
			g_string_append(helper->xml, text);
		} else {
			g_string_append(helper->xml, ">");
			if (helper->flags & XB_NODE_EXPORT_FLAG_FORMAT_MULTILINE)
				g_string_append(helper->xml, "\n");
		}
		helper->off += xb_silo_node_get_size(sn);

		/* recurse deeper */
		while (TRUE) {
			XbSiloNode *child = xb_silo_get_node(self, helper->off, error);
			if (child == NULL)
				return FALSE;
			if (!xb_silo_node_has_flag(child, XB_SILO_NODE_FLAG_IS_ELEMENT))
				break;

			/* check recursion depth to prevent stack overflow */
			if (helper->level >= XB_SILO_EXPORT_MAX_DEPTH) {
				g_set_error(error,
					    G_IO_ERROR,
					    G_IO_ERROR_INVALID_DATA,
					    "nesting deeper than %u levels not supported",
					    (guint)XB_SILO_EXPORT_MAX_DEPTH);
				return FALSE;
			}

			helper->level++;
			if (!xb_silo_export_node(self, helper, child, error))
				return FALSE;
			helper->level--;
		}

		/* check for the single byte sentinel */
		sn2 = xb_silo_get_node(self, helper->off, error);
		if (sn2 == NULL)
			return FALSE;
		if (xb_silo_node_has_flag(sn2, XB_SILO_NODE_FLAG_IS_ELEMENT)) {
			g_set_error(error,
				    G_IO_ERROR,
				    G_IO_ERROR_INVALID_DATA,
				    "no seninel at %" G_GUINT32_FORMAT,
				    helper->off);
			return FALSE;
		}
		helper->off += xb_silo_node_get_size(sn2);

		/* add closing tag */
		if ((helper->flags & XB_NODE_EXPORT_FLAG_FORMAT_INDENT) > 0 &&
		    xb_silo_node_get_text_idx(sn) == XB_SILO_UNSET) {
			for (guint i = 0; i < helper->level; i++)
				g_string_append(helper->xml, "  ");
		}
		g_string_append_printf(helper->xml, "</%s>", element_name);
	}

	/* add any optional tail */
	if (xb_silo_node_get_tail_idx(sn) != XB_SILO_UNSET) {
		const gchar *tail_unsafe;
		g_autofree gchar *tail = NULL;

		tail_unsafe = xb_silo_from_strtab(self, xb_silo_node_get_tail_idx(sn), error);
		if (tail_unsafe == NULL)
			return FALSE;
		tail = xb_string_xml_escape(tail_unsafe);
		g_string_append(helper->xml, tail);
	}

	if (helper->flags & XB_NODE_EXPORT_FLAG_FORMAT_MULTILINE)
		g_string_append(helper->xml, "\n");

	return TRUE;
}

/* private */
GString *
xb_silo_export_with_root(XbSilo *self, XbSiloNode *sroot, XbNodeExportFlags flags, GError **error)
{
	XbSiloNode *sn;
	XbSiloExportHelper helper = {
	    .flags = flags,
	    .level = 0,
	    .off = sizeof(XbSiloHeader),
	};

	g_return_val_if_fail(XB_IS_SILO(self), NULL);

	/* this implies the other */
	if (flags & XB_NODE_EXPORT_FLAG_ONLY_CHILDREN)
		flags |= XB_NODE_EXPORT_FLAG_INCLUDE_SIBLINGS;

	/* optional subtree export */
	if (sroot != NULL) {
		sn = sroot;
		if (sn != NULL && flags & XB_NODE_EXPORT_FLAG_ONLY_CHILDREN) {
			g_autoptr(GError) error_local = NULL;
			sn = xb_silo_get_child_node(self, sn, &error_local);
			if (sn == NULL) {
				if (!g_error_matches(error_local,
						     G_IO_ERROR,
						     G_IO_ERROR_INVALID_ARGUMENT)) {
					g_propagate_error(error, g_steal_pointer(&error_local));
					return NULL;
				}
			}
		}
	} else {
		sn = xb_silo_get_root_node(self, error);
		if (sn == NULL)
			return NULL;
	}

	/* no root */
	if (sn == NULL) {
		g_set_error_literal(error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND, "no data to export");
		return NULL;
	}

	/* root node */
	helper.xml = g_string_new(NULL);
	if ((flags & XB_NODE_EXPORT_FLAG_ADD_HEADER) > 0)
		g_string_append(helper.xml, "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n");
	do {
		g_autoptr(GError) error_local = NULL;
		if (!xb_silo_export_node(self, &helper, sn, error)) {
			g_string_free(helper.xml, TRUE);
			return NULL;
		}
		if ((flags & XB_NODE_EXPORT_FLAG_INCLUDE_SIBLINGS) == 0)
			break;
		sn = xb_silo_get_next_node(self, sn, &error_local);
		if (sn == NULL) {
			if (g_error_matches(error_local, G_IO_ERROR, G_IO_ERROR_INVALID_ARGUMENT))
				break;
			g_propagate_error(error, g_steal_pointer(&error_local));
			return NULL;
		}
	} while (TRUE);

	/* success */
	return helper.xml;
}

/**
 * xb_silo_export:
 * @self: a #XbSilo
 * @flags: some #XbNodeExportFlags, e.g. #XB_NODE_EXPORT_FLAG_NONE
 * @error: the #GError, or %NULL
 *
 * Exports the silo back to XML.
 *
 * Returns: XML data, or %NULL for an error
 *
 * Since: 0.1.0
 **/
gchar *
xb_silo_export(XbSilo *self, XbNodeExportFlags flags, GError **error)
{
	GString *xml;
	g_return_val_if_fail(XB_IS_SILO(self), NULL);
	g_return_val_if_fail(error == NULL || *error == NULL, NULL);
	xml = xb_silo_export_with_root(self, NULL, flags, error);
	if (xml == NULL)
		return NULL;
	return g_string_free(xml, FALSE);
}

/**
 * xb_silo_export_file:
 * @self: a #XbSilo
 * @file: a #GFile
 * @flags: some #XbNodeExportFlags, e.g. #XB_NODE_EXPORT_FLAG_NONE
 * @cancellable: a #GCancellable, or %NULL
 * @error: the #GError, or %NULL
 *
 * Exports the silo back to an XML file.
 *
 * Returns: %TRUE on success
 *
 * Since: 0.1.2
 **/
gboolean
xb_silo_export_file(XbSilo *self,
		    GFile *file,
		    XbNodeExportFlags flags,
		    GCancellable *cancellable,
		    GError **error)
{
	g_autoptr(GString) xml = NULL;

	g_return_val_if_fail(XB_IS_SILO(self), FALSE);
	g_return_val_if_fail(G_IS_FILE(file), FALSE);
	g_return_val_if_fail(cancellable == NULL || G_IS_CANCELLABLE(cancellable), FALSE);
	g_return_val_if_fail(error == NULL || *error == NULL, FALSE);

	xml = xb_silo_export_with_root(self, NULL, flags, error);
	if (xml == NULL)
		return FALSE;
	return g_file_replace_contents(file,
				       xml->str,
				       xml->len,
				       NULL,  /* etag */
				       FALSE, /* make-backup */
				       G_FILE_CREATE_NONE,
				       NULL, /* new etag */
				       cancellable,
				       error);
}