max password length issue: md5 + pam_unix

[Leonardo Canducci <leonardocanducci@yahoo.it>]

I'm using debian sarge with shadow passwords and md5. The file 
/etc/pam.d/common-password contains a single uncommented line:

password   required   pam_unix.so nullok obscure min=6 max=8 md5

passwd command doesn't let me chose a password shorter than 6
characthers (fine), but it accepts passwords longer than 8 chars (quite
strange).
I doesn't just consider the first 8 chars, but the whole password and
entries in /etc/shadow change if I choose for example:
charachter	123456789 ecc.
passwd1 	testpassWORD
passwd2		testpassFOO

Can somebody explain me that behaviour?

thanks
-- 
Leonardo Canducci 
GPG Key ID: 429683DA