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From "Ilguiz Latypov (Jira)" <j...@apache.org>
Subject [jira] [Comment Edited] (SLING-8879) Make JSONObject#toString and XSSAPI#encodeForJSString both safe and correct for pasting into a javascript string literal
Date Thu, 05 Dec 2019 17:56:00 GMT

    [ https://issues.apache.org/jira/browse/SLING-8879?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16989033#comment-16989033
] 

Ilguiz Latypov edited comment on SLING-8879 at 12/5/19 5:55 PM:
----------------------------------------------------------------

I also see a suggestion to fool-proof more characters serialized as JSON strings in case these
strings are embedded into a javascript embedded in HTML.

https://security.stackexchange.com/questions/11091/is-this-json-encoding-vulnerable-to-cdata-injection/11097#11097

This suggests to encode with {{raw &#x5C;uXXXX}}
* the opening angle bracket {{raw &#x3C;}} against closing the script tag or opening a
comment tag, 
* the closing angle bracket {{raw &#x3E;}} against closing a possible CDATA wrapper around
the javascript text embedded in XHTML (and HTML?),
* {{U+2028}} and {{U+2029}} allowed in JSON but not in Javascript against disrupting the javascript
engine.
* the ampersand {{raw &#x26;}} without a specific concern.




was (Author: ilatypov):
I also see a suggestion to fool-proof more characters serialized as JSON strings in case these
strings are embedded into a javascript embedded in HTML.

https://security.stackexchange.com/questions/11091/is-this-json-encoding-vulnerable-to-cdata-injection/11097#11097

This suggests to encode 
* the opening angle bracket {{raw &#x3C;}} against closing the script tag or opening a
comment tag, 
* the closing angle bracket {{raw &#x3E;}} against closing a possible CDATA wrapper around
the javascript text embedded in XHTML (and HTML?),
* {{U+2028}} and {{U+2029}} allowed in JSON but not in Javascript against disrupting the javascript
engine.
* the ampersand {{raw &#x26;}} without a specific concern.



> Make JSONObject#toString and XSSAPI#encodeForJSString both safe and correct for pasting
into a javascript string literal
> ------------------------------------------------------------------------------------------------------------------------
>
>                 Key: SLING-8879
>                 URL: https://issues.apache.org/jira/browse/SLING-8879
>             Project: Sling
>          Issue Type: Bug
>          Components: XSS Protection API
>            Reporter: Ilguiz Latypov
>            Priority: Minor
>
> The current implementation risks exceptions in strict javascript engines.
> |return source == null ? null : Encode.forJavaScript(source).replace("&#x5C;&#x5C;-",
"&#x5C;&#x5C;u002D");|
> Substitutes on top of the encoder's result with the intent to correct the encoder are
near-sighted (i.e. suffer from the context-free approach). If {{source}} had a backslash followed
by a dash, i.e. {{raw &#x5C;&#x2D;}}, the {{forJavaScript}} call would properly change
the backslash into 2 backslashes {{raw &#x5C;&#x5C;&#x2D;}} (this would result
in the javascript engine turning the string literal back to {{raw &#x5C;&#x2D;}}).
But the subsequent {{replace}} call will destroy the context of the second backslash, turning
the string into {{raw &#x5C;&#x5C;u002D}} which would turn to {{raw &#x5C;u002D}}
in the javascript engine's variable.
> I argue for dropping the {{.replace()}} call (aiming at disabling malicious comment injection)
here and encoding the opening angle bracket {{raw <}} as {{raw &#x5C;u003C}} in the
{{Encode.forJavaScript}} implementation. This will protect against both the malicious comment
injection and the injection of closing script tags {{raw &#x3C;&#x5C;script>}}
forcing the javascript interpreter to drop out of the string literal context and drop out
of the script context.
> The existing prefixing of forward slashes with a backslash agrees with JSON but not with
Javascript. It should be removed in favour of replacing just the opening angle bracket.
> {noformat}
> SingleEscapeCharacter :: one of
> ' " \ b f n r t v
> {noformat}
> [https://www.ecma-international.org/ecma-262/6.0/#sec-literals-string-literals]
> [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String#Escape_notation]
> I noticed that JSONObject#toString suffers from the same idea of a non-universal protection
of the forward slash.  I guess both XSSAPI and JSONObject#toString reuse the same code.



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