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non-root permission to the /etc/shadow?

A regular user needs to change his password. Users' encrypted password is stored in /etc/shadow a file which can only be modified by the root user. How a non-root user can change his own password when he does not have write permission to the /etc/shadow?

Quote:

Originally Posted by tvdtharindu (Post 5905988)

The passwd program has the setuid bit. It's the "s" in "rws" below:

Code:

$ ls -l /usr/bin/passwd

-rwsr-xr-x 1 root root 54256 May 17  2017 /usr/bin/passwd

The effect is that a passwd process adopts the identity of the owner, in this case root. This is how it can modify the shadow file.

Lots of detail in Wikipedia.

Quote:

Originally Posted by berndbausch (Post 5905998)

The passwd program has the setuid bit. It's the "s" in "rws" below:

Code:

$ ls -l /usr/bin/passwd

-rwsr-xr-x 1 root root 54256 May 17  2017 /usr/bin/passwd

The effect is that a passwd process adopts the identity of the owner, in this case root. This is how it can modify the shadow file.

Lots of detail in Wikipedia.

thanks berndbausch ..

did bit of research and found some details , but couldn't combine all those. your answer completed quarry