Linux Upgrade Password Hashing Algorithm to SHA-512

by on November 10, 2009 · 12 comments· LAST UPDATED November 12, 2009

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The default algorithm for storing password hashes in /etc/shadow is MD5. I was told to use SHA-512 hashing algorithm. How do I set password hashing using the SHA-256 and SHA-512 under CentOS or Redhat Enterprise Linux 5.4?

You need to use authconfig command to setup SHA-256/512 hashing. This command provides a simple method of configuring /etc/sysconfig/network to handle NIS, as well as /etc/passwd and /etc/shadow, the files used for shadow password support. Basic LDAP, Kerberos 5, and SMB (authentication) client configuration is also provided.

Display Current Hashing Algorithm

Type the following command:
# authconfig --test | grep hashing
Sample outputs:

password hashing algorithm is md5

Configure Linux Server To Use The SHA-512

To configure the Linux system to use the SHA-512 algorithm, enter:
# authconfig --passalgo=sha512 --update
Note users need to change their passwords in order to generate hashes using SHA-512. You can force users to change their password on next login:
# chage -d 0 userName

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{ 12 comments… read them below or add one }

1 Andrii November 11, 2009 at 12:52 pm

Is it works in Debian?

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2 iCroc November 11, 2009 at 2:29 pm

This message appear

authconfig: Unknown password hashing algorithm specified, using sha256.

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3 iCroc November 11, 2009 at 10:19 pm

I have solved this problem by replacing this command
authconfig –passalgo=SHA512 –update
to
authconfig –passalgo=sha512 –update

Because no algorithm called SHA512

Best Regards

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4 Philippe Petrinko November 12, 2009 at 10:56 am

Hi Vivek,
This is an Interesting post. Thanks for writing it.

BTW, would you modify
# authconfig –passalgo=SHA512 –update

to lowercase “sha512″ as iCroc observed ?

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5 kubrick November 12, 2009 at 11:16 am

I’ve found this little article for Debian based systems.
You could change the default MD5 algorithm for the more secure Blowfish.

On Debian GNU/Linux, switching from the default MD5 algorithm to Blowfish is slightly more work, but still not terribly difficult to accomplish:

First, install the libpam-unix2 module. That can be done simply via APT, Debian’s software management system, using the command
# apt-get install libpam-unix2
Next, edit /etc/pam.d/common-auth, /etc/pam.d/common-account, /etc/pam.d/common-session, and /etc/pam.d/common-password so that in each file you replace pam_unix.so with pam_unix2.so.
Finally, while you are editing the common-password file, change the term md5 so that it reads blowfish instead.

Cheers!

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6 nixCraft November 12, 2009 at 1:17 pm

@ iCroc / Philippe

Thanks for pointing out the typo.

@ kubrick,

Thanks for sharing Debian specific information.

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7 j0rn November 24, 2009 at 11:45 pm

nice tip, thx :)
the algorithm corresponds to the second parameter in shadow passwords entries

user:$1$abcdef…

$1$ is md5 while $6$ is sha512, $0$ should be old des and $2$ blowfish I think

man crypt ;)

I updated my local users digest “by hand” by modifying the “ENCRYPT_METHOD” directive directly in login.defs, but I didn’t that -more elegant- way to do

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8 KING SABRI January 11, 2010 at 1:38 am

Thnaks Vivek

Fedora 12 by Default uses SHA-512
CentOS-5.4 by Default uses MD5
Ubuntu by Default uses MD5, But the command Not Found

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9 nixCraft January 11, 2010 at 4:46 am

Try kubrick comment # 5, it may work on Ubuntu too…

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10 wedgeshot April 7, 2010 at 2:43 pm

Actually Ubuntu is sha512 in 9.04 and 9.10. I don’t remember changing anything related to PAM so that should be the default

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11 chris July 30, 2012 at 8:54 am

sha-512 should not be used for passwords. nor should md5 – you need some kind of HMAC solution instead – see hashcat speeds for a great example of what’s really weak.

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12 william October 23, 2012 at 2:35 am

does it affect other passwords like application servers installed in the same linux box?

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