Re: Web session tracking security prob. Vulnerable: IIS and ColdF usion (maybe others)

[Kevin Fu <fubob () MIT EDU>]

Here's information about how CFTOKEN and CFID work.  Below is a
snippet of technical information that Allaire Corporation sent me.

My research group has documented stuff related to this on
http://cookies.lcs.mit.edu/.

--------
Kevin E. Fu (fubob () mit edu)
PGP key: https://snafu.fooworld.org/~fubob/pgp.html

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1) From the ColdFusion 4.5.1 SP2 Release Notes:
> > > CFID is assigned sequentially per machine. The entire value 
> > > must consist of all decimal digits (0-9). 
> > > CFTOKEN - by default assigned as a random long integer. The 
> > > value range is 0 < x < 2,147,483,647. ColdFusion no longer 
> > > validates any part of this token, allowing users to re-assign 
> > > this to any value they choose. 
> > >
> > > However, by setting the registry key 
> > > HKEY_LOCAL_MACHINE\Software\Allaire\ColdFusion\CurrentVersion\
> > > Clients\ UuidToken to be the string value "1", ColdFusion 
> > > assigns CFTOKENS using the same random number concatenated 
> > > with a UUID, which is guaranteed to be globally unique.
> > >
> > > We use the random number to avoid simple guessing of the 
> > > uuids, since only a small portion of a uuid changes with each 
> > > assignment, and to make database lookups more efficient.
> > >
> > > A typical CFTOKEN using this method looks like this: 
> > > 57c6419-f0c43bb2-9e8d-11d3-8b87-00c04fa35ba5
> > >
> > > If you turn on the UuidToken switch and you are storing 
> > > client variable information in a database, you will need to 
> > > increase the column width of the 'cfid' column in the CDATA 
> > > and CGLOBAL tables. You should change the current width of 20 
> > > characters to at least 50 characters, due to the increased 
> > > length of CFTOKEN.
> > >
> > > You may also have to change other applications if they are 
> > > storing the CFTOKEN value in a fixed length field.

2) I looked into the algorithm we use to generate the random number.  The
answer from our lead developer for ColdFusion is:

> We use a random number generator from the book
>     Algorithms in C, p513 by Sedgewick

Our lead developer does not think the random number generator is
cryptographically secure.

...

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