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List:       centos
Subject:    [CentOS] C7 pam_oath.so changes group ownership of system file
From:       Tom Yates <madhatter () teaparty ! net>
Date:       2022-06-04 9:44:47
Message-ID: 5863c7ea-3e66-cddb-16af-537a51ca7e3 () teaparty ! net
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I'm using pam_oath.so to control sudo access. The following line appears 
in my /etc/pam.d/sudo:

auth       sufficient   pam_oath.so usersfile=/etc/users.oath window=5 digits=8

It works well, and has done since time out of mind.  I've recently 
noticed, however, that having a user authenticate via a HOTP OATH token 
not only causes the /etc/users.oath file to be updated (which makes sense, 
the stored counter needs to be incremented) but also have its 
group-ownership changed to the primary group of the last user who sudoed.

The file has no group read- or writeability, but it still strikes me as 
weird, and if the group modes were not -rwx, it might be a vulnerability. 
Does anyone else use HOTP OATH via PAM, and see this?  Is there a good 
reason for it?


[me@dormouse ~]$ ls -la /etc/users.oath
-rw-------. 1 root root 550 Jun  4 10:31 /etc/users.oath
[me@dormouse ~]$ sudo -l
One-time password (OATH) for `me':
[...]
User me may run the following commands on dormouse:
     (ALL) ALL
[me@dormouse ~]$ ls -la /etc/users.oath
-rw-------. 1 root me 550 Jun  4 10:33 /etc/users.oath



-- 

       Tom Yates  -  https://www.teaparty.net
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