How to verify the root password

[smrutilal2]

Hi,

I want to verify the root password. I am using rPath linux and my use case is like this:

1. There is screen in my application through which user can change the root user's password. He provides 2 information in the screen

i. existing password
ii. new password

2. I use a shell script in the back end that uses the "passwd" command to do it. And it doesn't ask for the existing password.

But, my business use case is if user enters wrong existing password, I should not reset the password and throw some error message.

How do I verify the existing root user's password? And also keep in mind that I am already in that linux box (logged in as root).

Plz, help me with this. Also let me now if there is any smarter way of doing it other than "passwd" command.

[Lakshmipathi]

Here is my suggestion :
#since you logged in as root - passwd not promting for existing root password.
#example root pwd is : abc and i have normal user account called laks

#get root user password from user , user gave " xyz"

#su laks
# now i'm not a root user just a normal user.
# now try to login to root with user given password "xyz"
laks>su root # here pass "xyz"
#if login fails - don't reset the password
#if user gave correct password then - just go ahead and change it.

the key point is - switch between normal user and root user.

[smrutilal2]

Thank you Lakshmipathi.

But, "su" is an interactive command. How do give both username and password in the script file itself ?

[Lakshmipathi]

Normally "here doc" will be used for interactive shell scripts.Here Documents - But i'm not sure whether su will work with here doc -- because this is serious security issue.

[Rubberman]

Your application is likely running as a root user if it isn't authenticating the old password. This is very, very bad form and can only happen if either the application was started by root, or is suid root (chmod +s appname). If it is running as root, then what it is doing is understandable - the system doesn't know that the connected user isn't root, and just changes it.