Encryption of login passwords--where and how is it done?

[Vince]

 > 
> > Where's the actual code that accepts the input of a password and/or 
> > encrypts it?  I looked in login.c, but that only seems to 
> call PAM or 
> > something; from that point on, I wasn't sure where to look.
> 
> Start with crypt(3).

As an aside, you can change the encryption used by login by changing the 
passwd_format option in login.conf for you login class. 
>From man login.conf

passwd_format    string    md5     The encryption format that new or
                                   changed passwords will use.  Valid
                                   values include "des", "md5" and
                                   "blf".  NIS clients using a
                                   non-FreeBSD NIS server should proba-
                                   bly use "des".


> 
> > I'm especially interested in knowing how a very long 
> password (up to 
> > the FreeBSD limit of, I think, 128 characters) is hashed and mashed 
> > into an encrypted password, but I'm also generally 
> interested in the 
> > whole process.  I'd like to think that a 128-byte password 
> consisting 
> > of random words and special characters would be just as secure as a 
> > shorter, completely random password, but that's only true 
> if FreeBSD 
> > is hashing the entire 128-byte string in some 
> cryptographically secure 
> > way in order to produce an encrypt password that is a function of 
> > every bit of the plaintext password.
> 
> Look in /usr/src/lib/libcrypt/.  The MD5 password hashing 
> scheme is found in crypt-md5.c (the whole password is being 
> used, btw).
> 
>     $.02,
>     /Mikko
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