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Prevent panic on fuzzer provided string (#14405)
* Prevent panic on fuzzer provided string The fuzzer has found that providing a <body> tag with an attribute to PostProcess causes a panic. This PR removes any rendered html or body tags from the output. Signed-off-by: Andrew Thornton <art27@cantab.net> * Placate lint * placate lint again Signed-off-by: Andrew Thornton <art27@cantab.net> * minor cleanup Signed-off-by: Andrew Thornton <art27@cantab.net>
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@ -317,9 +317,6 @@ func RenderEmoji(
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return ctx.postProcess(rawHTML)
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}
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var byteBodyTag = []byte("<body>")
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var byteBodyTagClosing = []byte("</body>")
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func (ctx *postProcessCtx) postProcess(rawHTML []byte) ([]byte, error) {
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if ctx.procs == nil {
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ctx.procs = defaultProcessors
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@ -327,9 +324,9 @@ func (ctx *postProcessCtx) postProcess(rawHTML []byte) ([]byte, error) {
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// give a generous extra 50 bytes
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res := make([]byte, 0, len(rawHTML)+50)
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res = append(res, byteBodyTag...)
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res = append(res, "<html><body>"...)
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res = append(res, rawHTML...)
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res = append(res, byteBodyTagClosing...)
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res = append(res, "</body></html>"...)
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// parse the HTML
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nodes, err := html.ParseFragment(bytes.NewReader(res), nil)
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@ -341,6 +338,31 @@ func (ctx *postProcessCtx) postProcess(rawHTML []byte) ([]byte, error) {
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ctx.visitNode(node, true)
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}
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newNodes := make([]*html.Node, 0, len(nodes))
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for _, node := range nodes {
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if node.Data == "html" {
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node = node.FirstChild
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for node != nil && node.Data != "body" {
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node = node.NextSibling
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}
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}
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if node == nil {
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continue
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}
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if node.Data == "body" {
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child := node.FirstChild
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for child != nil {
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newNodes = append(newNodes, child)
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child = child.NextSibling
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}
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} else {
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newNodes = append(newNodes, node)
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}
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}
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nodes = newNodes
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// Create buffer in which the data will be placed again. We know that the
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// length will be at least that of res; to spare a few alloc+copy, we
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// reuse res, resetting its length to 0.
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@ -353,12 +375,8 @@ func (ctx *postProcessCtx) postProcess(rawHTML []byte) ([]byte, error) {
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}
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}
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// remove initial parts - because Render creates a whole HTML page.
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res = buf.Bytes()
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res = res[bytes.Index(res, byteBodyTag)+len(byteBodyTag) : bytes.LastIndex(res, byteBodyTagClosing)]
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// Everything done successfully, return parsed data.
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return res, nil
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return buf.Bytes(), nil
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}
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func (ctx *postProcessCtx) visitNode(node *html.Node, visitText bool) {
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@ -383,3 +383,28 @@ func TestRender_ShortLinks(t *testing.T) {
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`<p><a href="https://example.org" rel="nofollow">[[foobar]]</a></p>`,
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`<p><a href="https://example.org" rel="nofollow">[[foobar]]</a></p>`)
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}
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func Test_ParseClusterFuzz(t *testing.T) {
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setting.AppURL = AppURL
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setting.AppSubURL = AppSubURL
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var localMetas = map[string]string{
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"user": "go-gitea",
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"repo": "gitea",
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}
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data := "<A><maTH><tr><MN><bodY ÿ><temPlate></template><tH><tr></A><tH><d<bodY "
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val, err := PostProcess([]byte(data), "https://example.com", localMetas, false)
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assert.NoError(t, err)
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assert.NotContains(t, string(val), "<html")
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data = "<!DOCTYPE html>\n<A><maTH><tr><MN><bodY ÿ><temPlate></template><tH><tr></A><tH><d<bodY "
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val, err = PostProcess([]byte(data), "https://example.com", localMetas, false)
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assert.NoError(t, err)
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assert.NotContains(t, string(val), "<html")
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}
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