File delete rights in Linux - 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.

Related

Unable to write to a file with group permissions

We are getting the error "permission denied" when trying to write to a file that is owned by a service user and a shared group. In particular that is www-data:www-data and the user trying to write to it is in the group www-data.
There is no acl on none of the parent folders and the permissions to the file and folders are correct.
Here some details:
$ sudo -u deploy id -Gn
www-data
$ ls -lah /tmp
drwxrwxrwt 17 root root 4.0K Jul 11 11:22 .
drwxr-xr-x 23 root root 4.0K Jul 8 10:08 ..
...
-rw-rw-r-- 1 www-data www-data 0 Jul 11 10:50 test
...
$ echo 'hello world' | sudo -u deploy tee -a /tmp/test
tee: /tmp/test: Permission denied
hello world
we tried that on different folders and made sure there is no acl on any of the folders or parents or files...
Unfortunately that is not described in the link stark posted in the comment. And also not in any other page I found until I found an answer here on stackoverflow that clarified it.
2018 two new filesystem configurations got added to sysctl that should prevent regular files and fifos from beeing opened with the O_CREAT flag (as append mode is doing) in directories with the sticky bit set unless the user is the owner of the file. This commit added the settings: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=30aba6656f61ed44cba445a3c0d38b296fa9e8f5
To change that behaviour you have to set fs.protected_regular to 0:
sudo sysctl fs.protected_regular=0
Or to persist the change add fs.protected_regular=0 to your sysctl.conf.
side node: since O_CREAT is not deleting or renaming the file I'm wondered why it is connected to the sticky bit. It really is possible to create a file in directories with the stick bit set.

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

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

Apache umask setting not working properly

I want files created by Apache to have 660 permissions, so I added the line "umask 007" to the file "/etc/sysconfig/httpd" and it works MOST of the time (as weird as that sounds).
For example, these files were created by Apache and the first one has the correct permissions, but the others don't.
-rw-rw---- 1 apache psacln 0 Aug 4 17:20 timthumb_cacheLastCleanTime.touch
-rw------- 1 apache psacln 124670 Aug 4 17:46 timthumb_int_00d3cbe9ad96f30121f17bbe1a92b42e.timthumb.txt
-rw------- 1 apache psacln 290077 Aug 4 18:27 timthumb_int_02d34e93c41599570c5302d6a08c8ba6.timthumb.txt
I'm not sure what to look for in order to fix this as it seems the UMASK setting is being ignored for some files. The problem here is that the FTP user (member of the psacln group) can't read the files that don't have group read permissions (because for security reasons I don't want to give permissions to "others").
Let me know if you have any idea why this may be happening.
umask controls which file permissions are set for files and directories when they are created. Most probably there is a code that is changing the permissions after the creation.

anacron script in cron.daily not running via symlink

What can I do to make this script run daily?
If I manually run the script, it works. I can see that it did what it's supposed to do. (backup files) However, it will not run as a cron.daily script. I've let it go for days without touching it -- and it never runs.
The actual script is here /var/www/myapp/backup.sh
There is a symlink to it here /etc/cron.daily/myapp_backup.sh -> /var/www/myapp/backup.sh
The cron log at /var/log/cron shows anacron running this script:
Aug 19 03:09:01 ip-123-456-78-90 anacron[31537]: Job `cron.daily' started
Aug 19 03:09:01 ip-123-456-78-90 run-parts(/etc/cron.daily)[31545]: starting myapp_backup.sh
Aug 19 03:09:01 ip-123-456-78-90 run-parts(/etc/cron.daily)[31559]: finished myapp_backup.sh
Yet there is no evidence that the script actually did anything.
Here is the security info on these files:
ls -la /var/cron.daily
<snip>
lrwxrwxrwx 1 root root 25 Aug 12 21:18 myapp_backup.sh -> /var/www/myapp/backup.sh
</snip>
ls -la /var/www/myapp
<snip>
drwxr-xr-x 2 root root 4096 Aug 13 13:55 .
drwxr-xr-x 10 root root 4096 Jul 12 01:00 ..
-rwxr-xr-x 1 root root 407 Aug 12 23:37 backup.sh
-rw-r--r-- 1 root root 33 Aug 12 21:13 list.txt
</snip>
The file called list.txt is used by backup.sh.
The script just runs tar to create an archive.
From the cron manpage of a debian/ubuntu system:
the files under these directories have to be pass some sanity checks including the following: be executable, be owned by root, not be writable by group or other and, if symlinks, point to files owned by root. Additionally, the file names must conform to the filename requirements of run-parts: they must be entirely made up of letters, digits and can only contain the special signs underscores ('_') and hyphens ('-'). Any file that does not conform to these requirements will not be executed by run-parts. For example, any file containing dots will be ignored.
So:
file need to be owned by root
if symlink, the source file need to be owned by root
if symlink, the link name should NOT contain dots
I had a similar situation with cron.hourly and awstats processing.
I THINK it is related to SELinux and anacron not having the same powers/permissions as cron.
The ACTUAL solution defeated me (so far).
MY WORKAROUND SOLUTION: Run the job via root's cron entries (crontab -e ) and simply schedule it hourly.

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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