HELP: Howtwo create a passwd-suitable hash for usage with psswd -H 0?

[O. Hartmann]

Am Thu, 18 Feb 2016 17:37:52 +0000
Gary Palmer <gpalmer at freebsd.org> schrieb:

> On Thu, Feb 18, 2016 at 06:11:22PM +0100, O. Hartmann wrote:
> > Am Thu, 18 Feb 2016 09:29:26 -0700
> > Ian Lepore <ian at freebsd.org> schrieb:
> >   
> > > On Thu, 2016-02-18 at 16:29 +0100, O. Hartmann wrote:  
> > > > On Thu, 18 Feb 2016 14:52:44 +0000
> > > > RW <rwmaillists at googlemail.com> wrote:
> > > >     
> > > > > On Thu, 18 Feb 2016 14:16:24 +0100
> > > > > O. Hartmann wrote:
> > > > >     
> > > > > > Hello out there,
> > > > > > 
> > > > > > I run into a problem and digging for a solution didn't work out.
> > > > > > 
> > > > > > Problem: I need a string that reflects the hashed password for the
> > > > > > usage with 
> > > > > > 
> > > > > > passwd -H 0      
> > > > > 
> > > > > Did you mean -h?    
> > > > 
> > > > no, I literally mean -H 0, I explain later ...
> > > >     
> > > > >     
> > > > > > I think the procedure is using 
> > > > > > 
> > > > > > sha512 -s Password
> > > > > > 
> > > > > > and using this output for further processing, but how?      
> > > > > 
> > > > > It's not as simple as that, password  hashes are usually salted and
> > > > > iterated. Salting means that the password is combined with a randomly
> > > > > generated string stored in plaintext, which means that the password
> > > > > doesn't hash to a fixed string.
> > > > > 
> > > > > I'm not sure exactly what you are trying to do, but crypt(3) may be of
> > > > > help.    
> > > > 
> > > > I'm now down to a small C routine utilizing crypt(3). But this is not what I
> > > > intend to have, since I want to use tools from the FBSD base system.
> > > > 
> > > > I build images of a small appliance in a secure isolated environment via
> > > > NanoBSD. I do not want to have passwords in the clear around here, but I also
> > > > do not want to type in everytime an image is created, so the idea is to have
> > > > passwords prepared as hashes in a local file/in variables. Therefore, I'm
> > > > inclined to use the option "-H 0" of the pw(1) command to provide an already
> > > > and clean hash (SHA512), which is then stored in /etc/master.passwd.
> > > > 
> > > > It is really funny: passwd or pw take passwords via stdin (-h 0 with pw) and
> > > > they "generate" somehow the hashed password and store that in master.password
> > > > - but I didn't find any way to pipe out the writing of the password to the
> > > > standard output from that piece of software. Why? Security concerns I forgot to
> > > > consider?
> > > > 
> > > > I found lots of articles and howtos to use pipes producing the required
> > > > password hashes via passwd, chpasswd or pw, but they all have one problem: I
> > > > have to provide somehow the cleartext password in an automated environment.
> > > > 
> > > > Maybe there is something missing ...
> > > > 
> > > > oh    
> > > 
> > > We use something like this at work (which I don't fully understand, but
> > > it works on freebsd 6.x through 10.x at least)...
> > > 
> > >  echo ${password} | openssl passwd -1 -stdin -salt VerySalty | \
> > >    pw -V ${IMAGE_CHROOT_DIR}/etc useradd -n ${username} -H0 $*
> > > 
> > > I guess for your use you'd capture and save the output of openssl so
> > > you could later feed it back to pw when making images.
> > > 
> > > -- Ian  
> > 
> > The "openssl passwd -1" refers to MD5 hashes, as I understand the manpage, but I
> > require at least sha256. With this solution suggested, I'd have the password still
> > stored in cleartext somewhere - if not read -in via read or similar.
> > 
> > If you snip off the openssl portion and substitute "-H0" with "-h0", then this is the
> > way I did before - as defined/configured in login.conf (usually in
> > ${IMAGE_CHROOT_DIR}/etc) SHA512 will be used as digest algorithm and the password
> > seems "salted", prepended by the $6$ characters.
> > 
> > I'd like to have something like
> > 
> > echo ${password} | openssl passwd -sha512 -stdin -salt VerySalty
> > 
> > and store the result in a variable somewhere for use with
> > 
> > echo ${password_salted_sha512_hash} | pw -V ${IMAGE_CHROOT_DIR}/etc usermod -n\
> > ${username} -H 0  
> 
> I presume you want to generate the password manually (to eliminate the
> storage of the cleartext password) and then store the hash in a script
> somewhere to be reused?  How often do you need to generate new hashes?

Quite often - weekly and the images are numerous. The problem is that I made in the
initial phase mistakes - lack of concentration et cetera and several passwords were then
worng and the images wrecked (CD/DVD).
 
> 
> I'm wondering why you can't have a dummy user that you just change the
> password for when you need a new hash and then grab the crypted password
> out of /etc/master.passwd

Well, this idea has also come to my mind - but the efford would be more (scripts to
extract ...) and, on the other hand, it's quite non-academic! I'd like a clean solution.

passwd() somehow results in such a hash - but passwd writes its hash into a file, no
chance so far to pipe the hash out. As Allen Jude already wrote - OpenBSD does have the
desired tool and it seems to me that there is need - in security areas, were OpenBSD has
its domain.

> 
> Thanks,
> 
> Gary
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