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dpaddy
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Joined: 25 Jun 2008
Posts: 117

PostPosted: Thu Aug 31, 2017 3:48 pm    Post subject: [SOLVED] manually hash passwords Reply with quote

I am root, and know what plaintext password was used for user foo.
Given that information, how can I manually create the entry for user foo that I find in /etc/shadow?

At this point I appreciate the fact that various files can influence how the entry for user foo in /etc/shadow is created.
But what files do I look at, what information do I extract from those files (and how), and then how do I use the information obtained together with knowledge of the plaintext password used for user foo to obtain the entry for user foo that I find in /etc/shadow?

I have seen https://forums.gentoo.org/viewtopic-t-677261-highlight-openssl+passwd.html but can't make things work.

What I find in /etc/shadow is

foo:$1$5xo...:17407:0:99999:7:::

where '...' indicates characters I have omitted, but

openssl passwd -1 -salt \$1 plaintext_password

does not produce what is in /etc/shadow. What does :?:


Last edited by dpaddy on Thu Aug 31, 2017 7:33 pm; edited 1 time in total
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fedeliallalinea
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Joined: 08 Mar 2003
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PostPosted: Thu Aug 31, 2017 4:12 pm    Post subject: Reply with quote

From internet (never tested):
Code:
# emerge whois
# mkpasswd -m sha-512 PASSWORD

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dpaddy
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Joined: 25 Jun 2008
Posts: 117

PostPosted: Thu Aug 31, 2017 7:27 pm    Post subject: Reply with quote

You may have nudged me in the right direction, but I still do not get what is stored in /etc/shadow...

Every time I execute
Code:
 mkpasswd -m sha-512 PASSWORD
I get a different answer.

I conjecture that has to do with (random?) salt... But where is the salt for user foo stored -- and how do I extract it -- so that I can use it to generate the hash of foo's password?
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dpaddy
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Joined: 25 Jun 2008
Posts: 117

PostPosted: Thu Aug 31, 2017 7:33 pm    Post subject: Reply with quote

I had previously looked (for quite some time, finding nothing that worked), but this time found the answer:

https://www.aychedee.com/2012/03/14/etc_shadow-password-hash-formats/

Thanks
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fedeliallalinea
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PostPosted: Thu Aug 31, 2017 7:43 pm    Post subject: Reply with quote

dpaddy wrote:
I conjecture that has to do with (random?) salt... But where is the salt for user foo stored -- and how do I extract it -- so that I can use it to generate the hash of foo's password?

Code:
$ mkpasswd -m sha-512 test -s xxxxxxxx
$6$xxxxxxxx$En/.y52/cZHAwsz.3QyXMCNpW8H7uHgWY4xS3rurbDH3atFhh2nCspgYuq1wWUK9F/Qz2r3r5Z6wP4Jepydsi1
   \______/
     salt

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szatox
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Joined: 27 Aug 2013
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PostPosted: Thu Aug 31, 2017 7:50 pm    Post subject: Reply with quote

Do you have an actual reason to do that manually?
Why not just go for:
Code:
# passwd foo

You could also use it's batch-oriented counterpart, chpasswd if you needed a non-interactive tool.
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