Centos – useradd not encrypting passwords in /etc/shadow

centosftppasswordshadowuseradd

I stumbled accross this problem when trying to create new FTP users for vsftpd.
Upon creating a new user with the following command and attempting login with FileZilla, I would get an "incorrect password" error.

useradd f -p pass -d /home/f -s /bin/false

After doing this, /etc/shadow contains

f:pass:1111:0:99:2:::

Once I run the following command and provide the same pass pass

passwd f

/etc/shadow contains

f:$1$U1c5vVwg$x5TVDDDmhi0a7RWFer6Jn1:1111:0:99:2:::

It appears that encryption happens when I run passwd, but doesn't upon useradd

Importantly after doing this, I am able to login to FTP with the exact same credentials.

I am using CentOS 5.11, vsftpd for FTP, and FileZilla for FTP Access

/var/log/secure contains:

Dec 17 useradd[644]: new group: name=f, GID=511
Dec 17 useradd[644]: new user: name=f, UID=511, GID=511, home=/home/f, shell=/bin/false

Why does it not work when I pass -p pass to useradd? What do I need to do to make it work?

Best Answer

That is working as intended. If you want to set a password using the useradd command, you are supposed to give a hashed version of the password to useradd.

The string pass does satisfy the format criteria for the hashed password field in /etc/shadow, but no actual password hashes to that string. The result is that for all intents and purposes, that account will behave as having a password, but any password you try to use to access it will be rejected as not being the correct password.

See man useradd or the useradd documentation:

-p, --password PASSWORD

The encrypted password, as returned by crypt(3). The default is to disable the password.

Note: This option is not recommended because the password (or encrypted password) will be visible by users listing the processes.

You should make sure the password respects the system's password policy.

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