Crthuky

When I try to set root's password:

root@OpenWrt:~# passwd
Changing password for root
Enter the new password (minimum of 5, maximum of 8 characters)
Please use a combination of upper and lower case letters and numbers.

It seems the maximum length is 8. If I try to set a password longer than 8, only first 8 characters is valid.
How can I set a longer password for root?

My openwrt version:

Linux OpenWrt 4.14.108 #0 SMP Wed Mar 27 21:59:03 2019 x86_64 GNU/Linux

I modified this in /etc/login.defs

PASS_MAX_LEN 8

problem fixed.

====================

Important additions:

After I changed the above parameters, although I can set a password larger than 8 digits, it is still invalid because the real password is only the first eight digits. I don't know if this is my problem.

My final solution is to set

# ENCRYPT_METHOD DES

to

ENCRYPT_METHOD MD5

in/etc/login.defs.

Now, I can finally set a root password that is really larger than eight.

This is because DES-based crypt truncates at 8 bytes.

That's the answer to your direct question, but here's some general advice implied by your context:

• Fortunately, from my reading, MD5 in /etc/login.defs is actually *md5crypt" ($1$), which, while a little outdated and no longer supported, is still far superior to DES-based crypt.




• It looks like SHA256 (actually sha256crypt) and SHA512 (actually sha512crypt) are also there. I would pick one of those instead.




• If you set your password to password or something under each scheme, you can visually verify whether or not my conclusion that they're the -crypt variants is correct (examples here are taken from the hashcat example hashes, all 'hashcat', some wrapped for readability):

Not recommended:

MD5 - 8743b52063cd84097a65d1633f5c74f5
SHA256 - 127e6fbfe24a750e72930c220a8e138275656b8e5d8f48a98c3c92df2caba935
SHA512 - 82a9dda829eb7f8ffe9fbe49e45d47d2dad9664fbb7adf72492e3c81ebd3e2 
 9134d9bc12212bf83c6840f10e8246b9db54a4859b7ccd0123d86e5872c1e5082f
descrypt - 48c/R8JAv757A

OK:

md5crypt - $1$28772684$iEwNOgGugqO9.bIz5sk8k/

Better:

sha256crypt - $5$rounds=5000$GX7BopJZJxPc/KEK$le16UF8I2Anb.rOrn22AUPWvzUETDGefUmAV8AZkGcD
sha512crypt - $6$52450745$k5ka2p8bFuSmoVT1tzOyyuaREkkKBcCNqoDKzYiJL9RaE8yMnPgh2XzzF0NDrUhgrcLwg78xs1w5pJiypEdFX/