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Prevent panic on fuzzer provided string #14405

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merged 5 commits into from
Jan 20, 2021
Merged

Prevent panic on fuzzer provided string #14405

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29289d4
Prevent panic on fuzzer provided string
zeripath Jan 19, 2021
79330db
Placate lint
zeripath Jan 20, 2021
3cb8f9f
placate lint again
zeripath Jan 20, 2021
bce2a0e
minor cleanup
zeripath Jan 20, 2021
6ebd07b
Merge remote-tracking branch 'origin/master' into alternate-fuzz-fix
zeripath Jan 20, 2021
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38 changes: 28 additions & 10 deletions modules/markup/html.go
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Original file line number Diff line number Diff line change
Expand Up @@ -317,19 +317,16 @@ func RenderEmoji(
return ctx.postProcess(rawHTML)
}

var byteBodyTag = []byte("<body>")
var byteBodyTagClosing = []byte("</body>")

func (ctx *postProcessCtx) postProcess(rawHTML []byte) ([]byte, error) {
if ctx.procs == nil {
ctx.procs = defaultProcessors
}

// give a generous extra 50 bytes
res := make([]byte, 0, len(rawHTML)+50)
res = append(res, byteBodyTag...)
res = append(res, "<html><body>"...)
res = append(res, rawHTML...)
res = append(res, byteBodyTagClosing...)
res = append(res, "</body></html>"...)

// parse the HTML
nodes, err := html.ParseFragment(bytes.NewReader(res), nil)
Expand All @@ -341,6 +338,31 @@ func (ctx *postProcessCtx) postProcess(rawHTML []byte) ([]byte, error) {
ctx.visitNode(node, true)
}

newNodes := make([]*html.Node, 0, len(nodes))

for _, node := range nodes {
if node.Data == "html" {
node = node.FirstChild
for node != nil && node.Data != "body" {
node = node.NextSibling
}
}
if node == nil {
continue
}
if node.Data == "body" {
child := node.FirstChild
for child != nil {
newNodes = append(newNodes, child)
child = child.NextSibling
}
} else {
newNodes = append(newNodes, node)
}
}

nodes = newNodes

// Create buffer in which the data will be placed again. We know that the
// length will be at least that of res; to spare a few alloc+copy, we
// reuse res, resetting its length to 0.
Expand All @@ -353,12 +375,8 @@ func (ctx *postProcessCtx) postProcess(rawHTML []byte) ([]byte, error) {
}
}

// remove initial parts - because Render creates a whole HTML page.
res = buf.Bytes()
res = res[bytes.Index(res, byteBodyTag)+len(byteBodyTag) : bytes.LastIndex(res, byteBodyTagClosing)]

// Everything done successfully, return parsed data.
return res, nil
return buf.Bytes(), nil
}

func (ctx *postProcessCtx) visitNode(node *html.Node, visitText bool) {
Expand Down
25 changes: 25 additions & 0 deletions modules/markup/html_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -383,3 +383,28 @@ func TestRender_ShortLinks(t *testing.T) {
`<p><a href="https://example.org" rel="nofollow">[[foobar]]</a></p>`,
`<p><a href="https://example.org" rel="nofollow">[[foobar]]</a></p>`)
}

func Test_ParseClusterFuzz(t *testing.T) {
setting.AppURL = AppURL
setting.AppSubURL = AppSubURL

var localMetas = map[string]string{
"user": "go-gitea",
"repo": "gitea",
}

data := "<A><maTH><tr><MN><bodY ÿ><temPlate></template><tH><tr></A><tH><d<bodY "

val, err := PostProcess([]byte(data), "https://example.com", localMetas, false)

assert.NoError(t, err)
assert.NotContains(t, string(val), "<html")

data = "<!DOCTYPE html>\n<A><maTH><tr><MN><bodY ÿ><temPlate></template><tH><tr></A><tH><d<bodY "

val, err = PostProcess([]byte(data), "https://example.com", localMetas, false)

assert.NoError(t, err)

assert.NotContains(t, string(val), "<html")
}