Unencrypt passwords

[BIS]

Hallo,

Is there any way to get users passwords. I have a mailserver that I want to migrate to another machine. Instead of having all users change their passwords (which would be useful I guess), is there a way that I can 'un'encrypt the passwords in /etc/passwd and /etc/shadow ?? Many of these users have never vhanged their passwords for the last couple of years and are not even awware of what their passwords are...

 

[sleipnir214]

Nope.

Linux passwords are not encrypted -- they're hashed. Hashes are one-way functions, because it is possible for two different passwords to hash to the same value.

However, if your new machine is running Linux, too, you should be able to move the passwords over as is. The hash algorithm should be the same. Want the best answers? Ask the best questions:

http://www.tuxedo.org/~esr/faqs/smart-questions.html

TANSTAAFL!

 

[Morsing]

You should find your sysadm whip (our best friend) and go after those users...

Cheers Henrik Morsing
Certified AIX 4.3 Systems Administration
& p690 Technical Support

 

[BIS]

Many thanks for the quick replys. New machine is indeed also Linux, but using md5 encryption (or something like that..). Old machine is 'old', has a variety of passwords, some in /etc/passwd, some in /etc/shadow. I am not sure they would work. How would I copy them? Just copy the string after username: and insert it on the other machine?

 

[sleipnir214]

There is one sure way to see if the hash algorithms are compatible.

Create the same test username on both servers, using the same password. Then compare the hash values in /etc/shadow between the two machines.

If they match, chances are you will be able to recreate the users on the new machine and overwrite their passwords in /etc/shadow using the values from the old machine. Want the best answers? Ask the best questions:

http://www.tuxedo.org/~esr/faqs/smart-questions.html

TANSTAAFL!

 

[flugh]

I'd install "shadow-utils" (Mandrake's name for the package) and use "pwunconv" to convert everything from shadow back to "regular" password locations. Once everything is back in /etc/passwd and /etc/group. Now for enabling MD5'd passwords... not sure. At least, for how to convert them. This post mentions looking at /etc/pam.d/passwd:

http://security-archive.merton.ox.ac.uk/linux-security-199911/0013.html

It's a start anyway --
JR

 

[BIS]

Many thanks for all your help.