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Author Topic: WebShield incorrectly blocking page  (Read 17272 times)

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keystroke

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WebShield incorrectly blocking page
« on: August 02, 2005, 08:14:44 PM »
The current version of Avast webshield doesn't seem to like the following URL:
http://library.ilcso.illinois.edu/uiu/cgi-bin/Pwebrecon.cgi?DB=local&PAGE=pbLogon

I'll post what happens if you are unable to reproduce the error. Basically, only part of the web page loads. It took awhile to troubleshoot this problem.. sniffer showed the full HTTP stream was coming in, but none of 3 browers would show the page. There is a 94a on top of the source, above the !DOCTYPE.

Thanks for looking into this!
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Offline YLAP

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Re: WebShield incorrectly blocking page
« Reply #1 on: August 02, 2005, 08:29:44 PM »
opens perfectly for me...  ??? Don't think it's a Web Shield problem as it's not blocking URL's. If you hasn't manually configured it to block the specific pages. (URL Blocking card in Resident > Web Shield > Customize)
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keystroke

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Re: WebShield incorrectly blocking page
« Reply #2 on: August 02, 2005, 08:39:18 PM »
Thanks for checking YLAP. The problem occurs on all browsers for me (Firefox, Opera, IE) unless I disable Avast Webshield. I can also make it work by enabling Webshield and inserting the URL into the exclude section. I'll post the incorrect HTML shortly.
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keystroke

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Re: WebShield incorrectly blocking page
« Reply #3 on: August 02, 2005, 08:45:10 PM »
I've just checked on another machine with Avast webshield and I have the same problem except on top of the page it says 924 instead of 94a.

Here is the HTML which I see when I go to view source in a browser while webshield is running. Ethereal confirms the correct HTTP response is being sent to the machine.

The part which says:

HREF="/uiu/cgi-bin/Pwebrecon.cgi?PAGE=REQNOBIB&SE
7e
Q=20050802125048&PID=7845

is incorrect as there is no 7e in the HTML.
Both machines I have tested on are WinXP SP2 with all current hotfixes applied.

94a
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd">
<HTML>
<HEAD>
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<META HTTP-EQUIV="Expires" CONTENT="-1">
<TITLE>UIUC's ILLINET Online Patron Logon</TITLE>
</HEAD>
<BODY onLoad="document.logonpage.BC.focus()"  bgcolor="#ffffff" text="#000000" link="#0033cc" vlink="#663399" alink="#0033cc">
<!-- Start of HTML header portion -->
<link rel="stylesheet" href="/uiu/UIU_webvoy.css">
<script language="JavaScript" src="/uiu/ilcso/funcs.js"></script>
<script language="JavaScript" src="/uiu/ilcso/mystrings.js"></script>
<script language=JavaScript src="/uiu/ilcso/timeout/ilcsotime.js"></script>

<script language=javascript> timeIt(); </script>
<CENTER>
<img src="/uiu/images/banner.gif" banner usemap="#Map" border="0">
 <map name="Map">
   <area shape="rect" coords="327,12,431,28" href="http://www.library.uiuc.edu" ALT="Library Gateway">
   <area shape="rect" coords="433,11,547,26" href="http://www.library.uiuc.edu/services/" ALT="Hours & Locations">
   <area shape="rect" coords="328,30,427,45" href="http://www.library.uiuc.edu/orr/" ALT="E-Journals">
   <area shape="rect" coords="434,29,548,44" href="http://web.library.uiuc.edu/ugl/vr" ALT="Ask A Librarian">
   <area shape="rect" coords="55,9,326,47" href="http://www.library.uiuc.edu/catalog" ALT="University of Illinois Online Library Catalog">
 </map>
</CENTER>

<!-- End of HTML header portion -->
<CENTER>
<FONT face=Default size=3><A HREF="/uiu/cgi-bin/Pwebrecon.cgi?PAGE=First&SEQ=20050802125048&PID=7845"><IMG ALIGN="MIDDLE" BORDER=0 ALT="Start a New Search" SRC="/uiu/images/UpSearch.gif"></A><A HREF="http://library.ilcso.illinois.edu/uc/cgi-bin/Pwebrecon.cgi?DB=local&PAGE=First"><IMG ALIGN="MIDDLE" BORDER=0 ALT="Search All ILCSO Libraries" SRC="/uiu/images/UpILCSO.gif"></A><A HREF="http://web.library.uiuc.edu/resource/librarycatalogs.html#offcat"><IMG ALIGN="MIDDLE" BORDER=0 ALT="Search Other Libraries" SRC="/uiu/images/UpDatabase.gif"></A><A><IMG ALIGN="MIDDLE" BORDER=0 SRC="/uiu/images/DisabledHeadings.gif"></A><A><IMG ALIGN="MIDDLE" BORDER=0 SRC="/uiu/images/DisabledTitles.gif"></A><IMG ALIGN=MIDDLE BORDER=0 ALT="Open My Account" SRC="/uiu/images/DownPatron.gif"><IMG ALIGN=MIDDLE BORDER=0 ALT="Login" SRC="/uiu/images/DownLogin.gif"><A HREF="/uiu/cgi-bin/Pwebrecon.cgi?PAGE=REQNOBIB&SE
7e
Q=20050802125048&PID=7845"><IMG ALIGN="MIDDLE" BORDER=0 ALT="Request Title" SRC="/uiu/images/DisabledRequest.gif"></A><A>
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Offline lukor

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Re: WebShield incorrectly blocking page
« Reply #4 on: August 02, 2005, 09:03:41 PM »
Thanks keystroke,
it was really a bug in webshield's code.

Can you please try to download this patch (into avast folder) and try it. You'll have to restart WebShield (terminate and start again) in order to load the patched module (ashwsftr.dll).

http://www2.asw.cz/~rypacek/ws_patch.zip

Edit: unpack both files into c:\program files\alwil software\avast4\ folder.
« Last Edit: August 02, 2005, 09:17:02 PM by lukor »
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Offline YLAP

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Re: WebShield incorrectly blocking page
« Reply #5 on: August 02, 2005, 09:34:12 PM »
Lukor, is there any need to do the same for me?  ???
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Offline lukor

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Re: WebShield incorrectly blocking page
« Reply #6 on: August 02, 2005, 09:44:28 PM »
Quote from: =YLAP= on August 02, 2005, 09:34:12 PM
Lukor, is there any need to do the same for me?  ???

I don't know your configuration, perhaps there are reasons why the problem is not visible at your place. It is definitely a bug, or let's say minor omission in the code. 99,9% percent of pages should not be affected by that - this one is the 0,1%.

The patch will of course be included in the next update, but we do not expect it sooner than in September.
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Offline YLAP

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Re: WebShield incorrectly blocking page
« Reply #7 on: August 02, 2005, 09:51:47 PM »
Thanks for info. As it's not a problem for me, I'll wait for BETA. Maybe it'll be sooner than in August!  ;)

My mistake. I've found what is missing in that page...  :-\ Donloaded patch too. Thanks to ALWIL team everything now works fine in that page.  ;D
« Last Edit: August 02, 2005, 10:13:49 PM by =YLAP= »
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Offline DavidR

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Re: WebShield incorrectly blocking page
« Reply #8 on: August 02, 2005, 09:58:14 PM »
For me that page didn't load fully, I downloaded the patch terminated web shield, copied both files into the avast4 folder, restarted web shield and the page then appears to have loaded fully.
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Windows 10 Home 64bit/ Acer Aspire F15/ Intel Core i5 7200U 2.5GHz, 8GB DDR4 memory, 256GB SSD, 1TB HDD/ avast! free 24.3.6108 (build 24.3.8975.762) UI 1.0.801/ Firefox, uBlock Origin, uMatrix/ MailWasher Pro/ Avast! Mobile Security

MFB

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Re: WebShield incorrectly blocking page
« Reply #9 on: August 02, 2005, 10:30:07 PM »
The patch works, I can see the page completely now.  Thanks Lukor for the link and keystroke for finding the bug.   :)
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Offline essexboy

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Re: WebShield incorrectly blocking page
« Reply #10 on: August 02, 2005, 11:38:11 PM »
Same problem fix works...Gracias
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keystroke

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Re: WebShield incorrectly blocking page
« Reply #11 on: August 03, 2005, 01:00:51 AM »
Thanks lukor for the patch, and everyone else for testing it before I had a chance. It works great! I'm glad to help Avast by finding this little bug. Out of curiosity, could you spare some more technical details as to just what was going on in that webpage which caused Avast to block it? What is the significance of the numbers on the top?

Thanks!
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Offline lukor

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Re: WebShield incorrectly blocking page
« Reply #12 on: August 03, 2005, 08:38:22 AM »
Quote from: keystroke on August 03, 2005, 01:00:51 AM
Thanks lukor for the patch, and everyone else for testing it before I had a chance. It works great! I'm glad to help Avast by finding this little bug. Out of curiosity, could you spare some more technical details as to just what was going on in that webpage which caused Avast to block it? What is the significance of the numbers on the top?

Thanks!

In the headers of the page there was one:

"Client-Transfer-Encoding: chunked"

This confused avast! in some place in the code. Avast! searches for the header "Transfer-Encoding: chunked". This header is checked during the transfer to detect if chunked encoding is used or not. One of the checks had a bug and incorrectly switched the stream to chunked encoding where it should not. The numbers you can see are headers of this encoding - number of bytes that follows.
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Mick Sturbes

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Re: WebShield incorrectly blocking page
« Reply #13 on: August 03, 2005, 09:43:38 AM »
Quote from: lukor on August 03, 2005, 08:38:22 AM
Quote from: keystroke on August 03, 2005, 01:00:51 AM
Thanks lukor for the patch, and everyone else for testing it before I had a chance. It works great! I'm glad to help Avast by finding this little bug. Out of curiosity, could you spare some more technical details as to just what was going on in that webpage which caused Avast to block it? What is the significance of the numbers on the top?

Thanks!

In the headers of the page there was one:

"Client-Transfer-Encoding: chunked"

This confused avast! in some place in the code. Avast! searches for the header "Transfer-Encoding: chunked". This header is checked during the transfer to detect if chunked encoding is used or not. One of the checks had a bug and incorrectly switched the stream to chunked encoding where it should not. The numbers you can see are headers of this encoding - number of bytes that follows.

Oh is that all it was ..................  :o  ???
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Offline lukor

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Re: WebShield incorrectly blocking page
« Reply #14 on: August 03, 2005, 09:46:06 AM »
Quote from: Mick Sturbes on August 03, 2005, 09:43:38 AM
Oh is that all it was ..................  :o  ???

yes.
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