generate hashed password for /etc/shadow

[PoolSnoopy]

Hi all,

does anyone know how to generate the hash used in /etc/shadow if the sha512 algorithm is used? for md5 I found that

openssl passwd -1 -salt <salt> <passwd>

will work fine. I'm using ubuntu 9.04 server and it seems that here sha512 instead of md5 is used. how can I generate a proper hash here?
a command line or php solution would be highly appreciated.

thanx a lot in advance!

[t00l]

<?php
echo hash('sha512', 'The quick brown fox jumped over the lazy dog.');
?>

Works for PHP5 >= 5.1.2

[PoolSnoopy]

well it's not quite as simple. :-) I would have figured that out myself. first of all the hash in /etc/shadow is salted and moreover the whole hash is kind of base64-encoded. but not the same way as for example mime-attachments in mails.

[t00l]

Well then, my fault. Still, maybe this would help (http://blog.loftninjas.org/2009/03/11/generating-sha512-passwords/) ;>
I've got blowfish in my OS so can't compare my results with any Ubuntu SHA512 psswd.

[PoolSnoopy]

thanx for that tip, but unfortunately it's not exactly what I need. :-( if I could provide the "salt" then it would be the perfect solution.

[koenn]

have you tried mkpasswd ?
mkpasswd [OPTIONS]... [PASSWORD [SALT]]


The version I have doesn't show sha512 as an available algorithm, but Im using 8.04 - maybe they updated mkpasswd along with the change in shadow ?

or,
a very elaborate workaround could be to use pwconv - depends on what exactly you're trying to do

[sisco311]

have you tried mkpasswd ?
mkpasswd [OPTIONS]... [PASSWORD [SALT]]


The version I have doesn't show sha512 as an available algorithm, but Im using 8.04 - maybe they updated mkpasswd along with the change in shadow ?


yep:
mkpasswd -m sha-512 password salt

[koenn]

cool.

[sisco311]

python:
python -c "import crypt, getpass, pwd; print crypt.crypt('password', '\$6\$SALTsalt\$')"

:)

[PoolSnoopy]

thank you so much.

the python solution works perfectly. the mkpasswd does not work with the salt given in /etc/shadow.

[sisco311]

thank you so much.

the python solution works perfectly. the mkpasswd does not work with the salt given in /etc/shadow.

in mkpasswd the salt must not contain prefixes such as $1$.

i.e.
$6$SALTSALT$PASSWORD
mkpasswd -m sha-512 password SALTSALT


you specify the method with the -m flag

in crypt
If salt is a character string starting with the characters "$id$" fol‐
lowed by a string terminated by "$":

$id$salt$encrypted

then instead of using the DES machine, id identifies the encryption
method used and this then determines how the rest of the password
string is interpreted. The following values of id are supported:

ID | Method
────────────────────────────────────────────────── ───────
1 | MD5
2a | Blowfish (not in mainline glibc; added in some
| Linux distributions)
5 | SHA-256 (since glibc 2.7)
6 | SHA-512 (since glibc 2.7)

So $5$salt$encrypted is an SHA-256 encoded password and
$6$salt$encrypted is an SHA-512 encoded one.

"salt" stands for the up to 16 characters following "$id$" in the salt.
The encrypted part of the password string is the actual computed pass‐
word. The size of this string is fixed:

MD5 | 22 characters
SHA-256 | 43 characters
SHA-512 | 86 characters

The characters in "salt" and "encrypted" are drawn from the set
[a–zA–Z0–9./]. In the SHA implementation the entire key is significant
(instead of only the first 8 bytes in MD5).

crypt('password', '\$6\$SALTSALT\$')"

for more info:
man mkpasswd
man 3 crypt

[PoolSnoopy]

ubuntu 9.04 comes with mkpasswd 4.7.30 and if I enter

mkpasswd -m sha-512 password saltsalt

I get

Wrong salt length: 8 byte(s) when 16 expected.

but I'm very happy with the python or php version. now I can use single-signon in web applications, too.

[cdenley]

ubuntu 9.04 comes with mkpasswd 4.7.30 and if I enter

mkpasswd -m sha-512 password saltsalt

I get

Wrong salt length: 8 byte(s) when 16 expected.

but I'm very happy with the python or php version. now I can use single-signon in web applications, too.

That is a bug in mkpasswd. It has been fixed in the next ubuntu release (9.10). Variable length salts are supported for SHA-512 password hashes, but mkpasswd didn't support them.
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=523387
http://changelogs.ubuntu.com/changelogs/pool/main/w/whois/whois_4.7.33/changelog