Re: Insecure Password Authentication in Yahoo! Messenger

[Emre Yildirim <emre () sgi asper org>]

> GOBBLES then run tcpdump and using YMSG structure above as reference he find
> first packet with service type constant 0x01. This LOGIN packet. GOBBLES
> notice it use MCF/MD5 encryption of user password with crypt(3) salt like
> $1$_2S43d5f$. Encrypted password is sent over the wire in LOGIN packet. User
> is immediately authenticated. 


Try this, login to Yahoo and type this into your URL bar:

javascript:document.cookie

This will reveal your Yahoo cookie.  Now, take a look at the Y= part:

Y=v=1&n=9pmgnpttq7fsr&l=6e11b4i1k6jh0g/o&p=m2g298l2020002&r=8p&lg=us

v= is probably version, n= is most likely the hashed password, like you 
already pointed out, probably a MD5 hash. Now, l= is more interesting. 
This is obviously "login".  My friend (jabanks () qwest net) figured out 
that this is simply some sort of ROT13-type encryption:

6 = g, e = o, 1 = b, b = l, 4 = e, i = s and so on...It's a matter of 
replacing letters and rotating the alphabet around.

So 6e11b4i1k6jh0g = gobblesbugtraq.  The /o never changes in the cookies 
for some reason.  I have no idea what p= is, but after several tests 
(changing passwords) it is not the password, regardless of "p".  It 
doesn't even seem to matter when someone logs in. I also don't know what 
r= is, but I'm sure it has something to do with n=, the password.  lg= 
is the language.

So in conclusion, if you could figure out n= you could also login to 
someone's account using a cookie.  Just my $0.02


> GREETS
> ******

[snip]

> nietzsche, radiohead,

Good philosophy...good music :)