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MD5 encryption on Slackware

Posted on 1998-07-31
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Last Modified: 2013-12-15
How can I setup MD5 encryption on a Slackware Linux installation? I'm migrating a FreeBSD box to Slackware Linux and I need to convert the password files, but I can't see how to implement MD5 encryption on Slackware.
It seems that RedHat have support to MD5 encryption, BUT I DONT want to use RedHat.
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Question by:normanjr
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Expert Comment

by:mirek071497
ID: 1628900
If you need shadow passwords then

If you have [ackages installed (they are in default) then try "pwconv" and "grpconv" this commands set the shadows.
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Expert Comment

by:mirek071497
ID: 1628901
OHH sorry - I was read very fast your question - please reject my answer. I wrote this for the Redhat, but You need to use Slackware and I don't know about this nothing.
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Accepted Solution

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JYoungman earned 200 total points
ID: 1628902
Red Hat use Pluggable Authentication Modules (a Sun invention)  to do this; it works in the same sort of way as does glibc2's /etc/nsswitch.conf system, by loading named shared objects under control of a configuration file.   Thus the programs themselves need have no idea how the passwords are encrypted.  (You can change all the pw encryption methods without recompiling anything).

Slackware just doesn't have anything like this, so you would need to modify and recompile login, su, {pop3,imap}d, passwd, chfn, chsh, and any X screen lockers, as a minimum.  

If the situation is that you just don't want to use Red Hat, you may have more luck with Debian than Slackware.  If it's that you must use Slackware, I'm afraid you're in for a lot of work.

There are methods of doing this that allow you just to modify the implementation of crypt(3) in the C library to make it auomatically recognise which encryption type is being used, but that depends on the password effectively having a special salt to indicate the encryption type.   I don't know if you have that luxury.

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Author Comment

by:normanjr
ID: 1628903
Well, actually slackware seems to partially support MD5, I do some tests on an old slackware 3.3 installation, where I just upgrade the kernel to 2.0.34, sendmail to 8.9.0, wuftpd to 2.6.0 and binutils. The results: Login (Telnet) accepts MD5 passwords on shadow file, recognising one or another (DES), in.pop3 accepts MD5 too, but wuftpd DONT. Do anyone knows a good source of information on the method explained by JYoungman about modifying crypt(3) in the C library? I have found an old file on an old mirror of sunsite called "md5crypt-1.0.tar.gz", but it dont work as expected. It generates a shared library "md5crypt.so.1", I putted it on ld.so.conf, ldconfig, etc etc, but apparently it dont change anything: login and pop3 still MD5 aware, but the rest that depends on crypt continues to NO understand MD5... It talks about and "ld.so.preload" file. This exists on slackware? I put the lib on "ld.so.conf". Here are the .LSM from this file:
Title:          MD5-based crypt() replacement
Version:        1.0
Entered-date:   01OCT97
Description:    Support for FreeBSD- and glibc-compatible MD5-based
                encrypted passwords.  Unlimited password length
                (instead of 8 characters in traditional DES-based
                passwords), more secure, no US export restrictions.
                No need to recompile libc - use /etc/ld.so.preload.
                Already implemented in glibc-2.x (libc6).
Keywords:       MD5 crypt passwd FreeBSD glibc
Author:         phk@login.dknet.dk (Poul-Henning Kamp)
                colin@nyx.cs.du.edu (Colin Plumb)
Maintained-by:  marekm@piast.t19.ds.pwr.wroc.pl (Marek Michalkiewicz)
Primary-site:   sunsite.unc.edu /pub/Linux/system/admin/
                14K md5crypt-1.0.tar.gz
Alternate-site: ftp.ists.pwr.wroc.pl /pub/linux/shadow/
Original-site:      
Platforms:      Linux, ld.so-1.8.x, libc-5.x

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Expert Comment

by:JYoungman
ID: 1628904
You may be able to use LD_PRELOAD or /etc/ld.so.preload,
if and only if the name of the function exported by the new library is also called crypt().


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Author Comment

by:normanjr
ID: 1628905
Yes, JYoungman, but the succesful including of the new library, with the new crypt() will override the original one?
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