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x/net/html: readRawOrRCDATA() parsing issue when text ends with '<' #20741

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sprungknoedl opened this issue Jun 21, 2017 · 0 comments
Open

x/net/html: readRawOrRCDATA() parsing issue when text ends with '<' #20741

sprungknoedl opened this issue Jun 21, 2017 · 0 comments
Milestone
Unreleased

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@sprungknoedl
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What version of Go are you using (go version)?

go version go1.8.3
golang.org/x/net/html: 057a25b06247e0c51ba15d8ae475feb2fcb72164

What operating system and processor architecture are you using (go env)?

linux/amd64

What did you do?

Tried to parse HTML that contains a textarea that ends with <. Minimal example below:

package main

import (
	"fmt"
	"strings"

	"golang.org/x/net/html"
)

func main() {
	example := `<textarea>ends with <</textarea>`
	z := html.NewTokenizer(strings.NewReader(example))

	for {
		tt := z.Next()
		switch tt {
		case html.ErrorToken:
			return

		case html.TextToken:
			txt := z.Text()
			fmt.Printf("$%s$ ", txt)

		case html.StartTagToken:
			tn, _ := z.TagName()
			fmt.Printf("<%s> ", tn)

		case html.EndTagToken:
			tn, _ := z.TagName()
			fmt.Printf("</%s> ", tn)
		}
	}
}

What did you expect to see?

<textarea> $ends with <$ </textarea>

What did you see instead?

<textarea> $ends with <</textarea>$

Possible solution

This diff fixes the problem and passes all tests, but not sure it is correct in all cases and according to the HTML spec:

diff --git a/html/token.go b/html/token.go
index 893e272..41cb76f 100644
--- a/html/token.go
+++ b/html/token.go
@@ -347,6 +347,7 @@ loop:
                        break loop
                }
                if c != '/' {
+                       z.raw.end--
                        continue loop
                }
                if z.readRawEndTag() || z.err != nil {
diff --git a/html/token_test.go b/html/token_test.go
index 20221c3..f8e3fdf 100644
--- a/html/token_test.go
+++ b/html/token_test.go
@@ -254,6 +254,11 @@ var tokenTests = []tokenTest{
                "<textarea>$&lt;div&gt;$</textarea>",
        },
        {
+               "textarea ends with '<'",
+               "<textarea><</textarea>",
+               "<textarea>$&lt;$</textarea>",
+       },
+       {
                "title with tag and entity",
                "<title><b>K&amp;R C</b></title>",
                "<title>$&lt;b&gt;K&amp;R C&lt;/b&gt;$</title>",
@gopherbot gopherbot added this to the Unreleased milestone Jun 21, 2017
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@sprungknoedl @gopherbot