Cron files /etc/at.allow and /etc/cron.allow files, root permission abnormal behaviour? - cron

In my open vpn server, i am ensuring cron file permission to be only accessable from root user.
I have removed the at.deny and cron.deny files and have created at.allow and cron.allow and 0600 permissions are applied for files, both files are empty and file permissions are as below, which clearly says root has read and write access.
-rw------- 1 root root 0 Jul 21 08:40 cron.allow
-rw------- 1 root root 0 Jul 21 08:40 at.allow
however this change allows my openvpnas user to still list the crontab and even allows to edit cron.
openvpnas#openvpnas2:~$ crontab -l
no crontab for openvpnas
Where as when the file permissions are as below,
-rw-r--r-- 1 root root 0 Jul 21 08:41 cron.allow
-rw-r--r-- 1 root root 0 Jul 21 08:41 at.allow
It restricts my non root users to access or edit cron files! This issue is only with one of my server, where as other server permissions and behaviours are as expected,
openvpnas#openvpnas2:~$ crontab -l
You (openvpnas) are not allowed to use this program (crontab)
See crontab(1) for more information
Please provide your inputs on this, this has kept me blocked from continuing my work.

This issue i faced was in Ubuntu 18.04 instance,
Current /usr/bin/crontab permission was as below,
-rwxr-sr-x 1 root crontab 39352 Nov 16 2017 /usr/bin/crontab
Had to change the group user from crontab to root and file permission to as below,
sudo chmod 4755 /usr/bin/crontab
sudo chown root:root /usr/bin/crontab
-rwsr-xr-x 1 root root 39352 Nov 16 2017 /usr/bin/crontab
This permission restricts the non-root user to schedule cronjobs. The access can be allowed to non-root users by adding the user names in cron.allow file.
openvpnas#openvpnas2:~$ crontab -l
You (openvpnas) are not allowed to use this program (crontab)
See crontab(1) for more information

Related

file owner can not change ownership in Linux

In Linux, I am the owner of a file, then I tried to change owner to another account, failed. Operation not permitted. Do you know why ? I am the user 'BBB'. Thanks
-bash-4.1$ ls -al
drwxrwxrwx 2 AAA games 4096 Nov 23 14:39 .
drwxr-xr-x 3 AAA games 4096 Nov 23 14:36 ..
-rw-r--r-- 1 BBB esmgroup 16798 Nov 23 14:38 XXX-1.0-SNAPSHOT.jar
-bash-4.1$ chown AAA:games ./*.jar
chown: changing ownership of `./XXX-1.0-SNAPSHOT.jar': Operation not permitted
Only root can change the owner on the file. That's final.
You can do that by login to root using su or use sudo before your command.
More information here: https://unix.stackexchange.com/questions/27350/why-cant-a-normal-user-chown-a-file
You can change the file's group if you're in more than one group.
You should login to root account to be granted to change ownership to any user
You can type sudo before the command and then login to your root user

How to change ubuntu to root?

I am new to linux. when i list the files under folder 1, i see below result
-rwxrwxrwx 1 root root 920 Jun 3 10:36 file1.xsd
-rwxrwxrwx 1 root root 920 Jun 3 10:36 file2.xsd
drwxrwxrwx 2 ubuntu ubuntu 4096 Jun 12 11:10 temp
-rwxrwxrwx 1 ubuntu ubuntu 1853 Jun 19 11:07 file3.xsd
for some files(file1 and file2) root root is written after permisionsbut for file3 ubuntu ubuntu is displayed.
what is difference b/w ubuntu ubuntu and root root ?
How can i change ubuntu ubuntu for file 3 to root root ?
The first "root" stands for user name and second "root" stands for the group name. By design, Ubuntu uses "sudo" command to run other commands "as root", and the actual root user is not used.
So what that means, every time you use the command sudo to run a command, it is actually being done as root. That's most likely the reason for the two of your files being owned by root (and the group root).
You can change the ownership of the file with command chown:
chown root:root file3.xsd

Can't CD to directory inside of root

I am currently creating an application that requires separate users running duplicate programs. They cannot run under root because of security reasons, so they are initiated by a Java app that I am working on, and I am starting them with runuser -l. However, I cannot cd into a directory, even though it is owned by the user, and the user has 770 permissions in the folder.
Here's what I'm running:
runuser -l lp1 -c 'java \-jar /root/Desktop/workspace/LitePanel/servers/server1/server.jar \-Xms1024M nogui'
And the output of this is:
runuser: warning: cannot change directory to /root/Desktop/workspace/LitePanel/bin/servers/server1/: Permission denied
Here's an ls -all:
drwxr-xr-x. 3 root root 4096 Jan 30 14:03 .
drwxr-xr-x. 7 root root 4096 Jan 30 14:02 ..
drwxrwx---. 2 lp1 lp1 4096 Jan 31 03:07 server1
Inside the directory:
drwxrwx---. 2 lp1 lp1 4096 Jan 31 03:07 .
drwxr-xr-x. 3 root root 4096 Jan 30 14:03 ..
-rwxrwx---. 1 lp1 lp1 9170551 Jan 31 03:07 server.jar
And here's /etc/passwd:
lp1:x:501:501::/root/Desktop/workspace/LitePanel/bin/servers/server1/:/bin/false
Anyone know why this is happening? It looks like the user has the necessary permissions to do this.
You have said that the directory itself has permissions 770 and is owned by the user, but what about its parents? I believe the cd command will need at least read access (and possibly execute) on the parent directories.

File delete rights in Linux

I have the following problem, I run a script on multiple servers that writes files on a single server.
Files are written with these rights:
-rw-r--r-- 1 someuser someuser 139 Apr 2 12:40 filename.jpg
What I would like to do would be to be able to delete this file via a php script that runs with www-data rights.
Is there a way to configure something so www-data is allowed to remove the above file?
The php script run wiht user (euid): www-data and group (egid): www-data.
One solution may be the following:
-rw-rw-r-- 1 someuser www-data 139 Apr 2 12:40 filename.jpg
In this situation, the php script could delete the file without problems.

why it is not possible to modify file in a directory, where i have read/write group rights

I am currently messing around on my linux system and now I have the following situation.
The directory /srv/http has the following permissions set:
drwxrwxr-x 2 root httpdev 80 Jun 13 11:48 ./
drwxr-xr-x 6 root root 152 Mar 26 13:56 ../
-rwxrwxr-x 1 root httpdev 8 Jun 13 11:48 index.html*
I have created the group httpdev before with the command:
groupadd httpdev
and added my user sighter with:
gpasswd -a sighter httpdev
Then I have set the permissions as above using the chown and chmod commands.
But now I am not allowed to modify the index.html file or create a new file, as user sighter ,with touch like that:
<sighter [bassment] ~http> touch hallo.php
touch: cannot touch `hallo.php': Permission denied
What do I understand wrong. I was expecting that I can do what I want there then the group has all the rights.
The following Output is for your information.
<sighter [bassment] ~http> cat /etc/group | grep sighter
...
httpdev:x:1000:sighter
...
The used linux-distro is archlinux.
Adding a user to a group does not affect currently running sessions. So you have to logout and login again or use su - sighter to login.
After this you should be able to do what you want to do.
You're not in the right group. You need to log out and back in again. Also, superuser.

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