I want to allow users to execute a bash script that contains sensitive data. Thus, I don't want them to have reading permissions. A 'direct' solution seems to be impossible, but I may have found a workaround in the expect man page:
Create the Expect script (that contains the secret data) as usual.
Make its permissions be 750 (-rwxr-x---) and owned by a trusted group,
i.e., a group which is allowed to read it. If necessary, create a new
group for this purpose. Next, create a /bin/sh script with permissions
2751 (-rwxr-s--x) owned by the same group as before.
I've tried to replicate this as follows:
In a folder, I have two scripts:
script.sh:
#!/bin/sh
echo "targetscript echo"
runscript.sh:
#!/bin/sh
echo "runscript echo"
groups
./script.sh
I gave them the rights as suggested in the man page:
groupadd scriptrunner
chown {myusername}:scriptrunner runscript.sh
chmod 2751 runscript.sh
chown root:scriptrunner script.sh
chmod 750 script.sh
The output of ls -l appears to be alright:
-rwxr-s--x. 1 {myusername} scriptrunner 51 Aug 25 13:04 runscript.sh
-rwxr-x---. 1 root scriptrunner 35 Aug 25 13:01 script.sh
However, when I run ./runscript.sh without root, I get the following error:
runscript echo
{myusername} wheel
./runscript.sh: line 4: ./script.sh: Permission denied
I don't know what went wrong. Can anyone help me?
I'll go back to the root problem as I think it's easier to solve without the expect hack.
So, what you need is having the execute permission on your script but not the reading permission. That is only possible for binaries (i.e. not interpreted scripts)- see details here https://unix.stackexchange.com/questions/34202/can-a-script-be-executable-but-not-readable
So maybe you'll be better off by first compiling your bash script into a binary (with shc - see here https://unix.stackexchange.com/questions/64762/how-to-convert-a-shell-script-into-a-binary-executable) and then set the execute only permission on the binary. Afterwards your users should be able to execute (but not read) the binary.
Related
I am trying a POC running a python script in a back-end implemented in PHP. The web server is Apache in a Docker container.
This is the PHP code:
$command = escapeshellcmd('/usr/local/test/script.py');
$output = shell_exec($command);
echo $output;
When I execute the python script using the back-end we are getting a permission denied error for creating the file.
My python script:
#!/usr/bin/env python
file = open("/tmp/testfile.txt","w+")
file.write("Hello World")
file.close()
This is the error I'm getting:
IOError: [Errno 13] Permission denied: 'testfile.txt'
For the directory im working with the permissions are as follows,
drwxrwsr-x 2 1001 www-data 4096 May 8 05:35 .
drwxrwxr-x 3 1001 1001 4096 May 3 08:49 ..
Any thoughts on this? How do I overcome this problem?
To start is is incredibly bad practice to have relative paths in any scripting environment. Start by rewriting your code to use a full path such as /usr/local/test/script.py and /tmp/testfile.txt. My guess is your script is attempting to write to a different spot than you think it is.
When you know exactly where the files are being written go to the directory and run ls -la and check the permissions on the directory. You want it to be writeable by the same user or group as the web server runs.
Looking at the permissions you have shown you don't have the user able to write to the directory, just everyone and the group. You need to add user write permissions - chmod u+w /tmp will do the job.
I believe the problem is that you are trying to write to an existing file in the /tmp/ directory. Typically /tmp/ will have the sticky permission bit set. That means that only the owner of a file has permission to write or delete it. Group write permissions on files do not matter if the sticky bit is set on the parent directory.
So if this is the contents of your /tmp
$ ls -al /tmp
drwxrwxrwt 5 root root 760 Apr 30 12:00 .
drwxr-xr-x 21 root root 4096 Apr 30 12:00 ..
-rw-rw---- 2 1001 www-data 80 May 8 12:00 testfile.txt
We might assume that users in the group www-data should be able to write to testfile.txt. But that is not the case, since . (the /tmp/ directory itself) has the sticky bit set (the t in the permissions section indicates this).
The reason why the sticky bit is set here is that everyone should be able to write files there, but not have to worry that other users might modify our temporary files.
To avoid permission errors, you can use the standard library tempfile module. This code will create a unique filename such as testfile.JCDxK2.txt, so it doesn't matter if testfile.txt already exists.
#!/usr/bin/env python
import tempfile
with tempfile.NamedTemporaryFile(
mode='w',
prefix='testfile.',
suffix='.txt',
delete=False,
) as file:
file.write("Hello World")
I am using Codeigniter's file helper class to create and write to files. (for logging) Is there a way I can change the user:group to apache:apache for these files programmatically during creation.
ls -l
-rw-r--r-- 1 surjya goper 188 Oct 31 02:03 mylog.log
I tried php's chown command just after file creation but it fails saying 'not permitted'. This is because php allows only if you are a super user.
Any work around for this would be appreciated.
I don't know if you can do that directly in PHP but you could always call a .sh script on the server to do it for you using shell_exec().
From my understanding, only a su can use chown, so you'd probably need to make an 'expect' script (http://docs.oracle.com/cd/E35328_01/E35336/html/vmcli-script.html) that will let the script become su, so it can chown the file.
I want to execute a Bash script present on the system from a PHP script. I have two scripts present on the system. One of them is a PHP script called client.php present at /var/www/html and the other is a Bash script called testscript present at /home/testuser.
My client.php script looks like
<?php
$message=shell_exec("/home/testuser/testscript 2>&1");
print_r($message);
?>
My testscript looks like
#!/bin/bash
echo "Testscript run succesful"
When i do the following on terminal
php client.php
I get the following output on terminal
Testscript run successful
But when i open the page at
http://serverdomain/client.php
I get the following output
sh: /home/testuser/testscript: Permission denied
I get this error even after I did chmod +x testscript.
How do I get it to work from the browser? Please help.
I would have a directory somewhere called scripts under the WWW folder so that it's not reachable from the web but is reachable by PHP.
e.g. /var/www/scripts/testscript
Make sure the user/group for your testscript is the same as your webfiles. For instance if your client.php is owned by apache:apache, change the bash script to the same user/group using chown. You can find out what your client.php and web files are owned by doing ls -al.
Then run
<?php
$message=shell_exec("/var/www/scripts/testscript 2>&1");
print_r($message);
?>
EDIT:
If you really want to run a file as root from a webserver you can try this binary wrapper below. Check out this solution for the same thing you want to do.
Execute root commands via PHP
Without really knowing the complexity of the setup, I like the sudo route.
First, you must configure sudo to permit your webserver to sudo run the given command as root. Then, you need to have the script that the webserver shell_exec's(testscript) run the command with sudo.
For A Debian box with Apache and sudo:
Configure sudo:
As root, run the following to edit a new/dedicated configuration file for sudo:
visudo -f /etc/sudoers.d/Webserver
(or whatever you want to call your file in /etc/sudoers.d/)
Add the following to the file:
www-data ALL = (root) NOPASSWD: <executable_file_path>
where <executable_file_path> is the command that you need to be able to run as root with the full path in its name(say /bin/chown for the chown executable). If the executable will be run with the same arguments every time, you can add its arguments right after the executable file's name to further restrict its use.
For example, say we always want to copy the same file in the /root/ directory, we would write the following:
www-data ALL = (root) NOPASSWD: /bin/cp /root/test1 /root/test2
Modify the script(testscript):
Edit your script such that sudo appears before the command that requires root privileges(say sudo /bin/chown ... or sudo /bin/cp /root/test1 /root/test2). Make sure that the arguments specified in the sudo configuration file exactly match the arguments used with the executable in this file.
So, for our example above, we would have the following in the script:
sudo /bin/cp /root/test1 /root/test2
If you are still getting permission denied, the script file and it's parent directories' permissions may not allow the webserver to execute the script itself.
Thus, you need to move the script to a more appropriate directory and/or change the script and parent directory's permissions to allow execution by www-data(user or group), which is beyond the scope of this tutorial.
Keep in mind:
When configuring sudo, the objective is to permit the command in it's most restricted form. For example, instead of permitting the general use of the cp command, you only allow the cp command if the arguments are, say, /root/test1 /root/test2. This means that cp's arguments(and cp's functionality cannot be altered).
I was struggling with this exact issue for three days. I had set permissions on the script to 755. I had been calling my script as follows.
<?php
$outcome = shell_exec('/tmp/clearUp.sh');
echo $outcome;
?>
My script was as follows.
#!bin/bash
find . -maxdepth 1 -name "search*.csv" -mmin +0 -exec rm {} \;
I was getting no output or feedback. The change I made to get the script to run was to add a cd to tmp inside the script:
#!bin/bash
cd /tmp;
find . -maxdepth 1 -name "search*.csv" -mmin +0 -exec rm {} \;
This was more by luck than judgement but it is now working perfectly. I hope this helps.
It's a simple problem. When you are running from terminal, you are running the php file from terminal as a privileged user. When you go to the php from your web browser, the php script is being run as the web server user which does not have permissions to execute files in your home directory. In Ubuntu, the www-data user is the apache web server user. If you're on ubuntu you would have to do the following:
chown yourusername:www-data /home/testuser/testscript
chmod g+x /home/testuser/testscript
what the above does is transfers user ownership of the file to you, and gives the webserver group ownership of it. the next command gives the group executable permission to the file. Now the next time you go ahead and do it from the browser, it should work.
I am trying to run adb from PHP using:
exec( 'adb devices', $output, $return_val );
but I get 126 error.
I think the problem is that php is running as 'www-data' user and does not have permissions to execute adb.
Any solutions?
Check this site out:
http://bzed.de/posts/2009/05/howto_set_android_developer_device_permissions_with_udev/
And add www-data to androiddev.
You need to add your specific model to the udev-lines. You can find the vendor- and product-id by connecting your phone to your computer and executing lsusb in a terminal.
You get something like:
Bus 001 Device 002: ID 413c:a001 Dell Computer Corp. Hub
where 413c is the Vendor ID and a001 is the ID of the product. Of course, your cell phone should be the line instead of "Dell Computer"...
Good luck!
If you are working on Windows, the easier solution that I know is:
Create a file.bat with the order adb devices and the variables $1 and $2.
Call the file.bat with php using exec command
That should work.
If you are working on Linux, use a /bin/bash. And use the same procedure.
Your friend google will help you if don't know how to do the scripts.
Although this is not a solution for 126 error, it's a way to run adb from php on Linux Debian 8.
If you have installed android-tools-adb, surely have noted that a new group has be created: adb, the user www-data must belong to it:
usermod -a -G adb www-data
And if you have using a Android version greater than or equal to 4.4.2 you need to accept RSA key fingerprint on screen on your cell phone, that at the same time makes a hidden directory in your computer named .android on user home path, there, will be stored both adbkey and adbkey.pub files, running:
cat /etc/passwd | grep www-data
You get
www-data:x:33:33:www-data:/var/www
Therefore, /var/www is for www-data user,
So, I changed its group from root to www-data
chown root:www-data /var/www
Then, I set write permissions
chmod 775 /var/www/
Now, .android directory can be created. Despite the message when you're going to accept RSA key fingerprint says: "Always allow from this computer", you must accept each user for computer if adb command is being used by different users on the same computer
And you can just try the adb command as www-data user, executing: (as root)
sudo -u www-data adb devices -l
I hope this helps someone else
I am trying to backup all the files on our server using some SSH commands via PHP and I have a script working to some extent.
The problem is that only some of the folders actually contain any files but the folder structure seems to be correct though.
This is the script I am using:
<?php
$output = `cd /
ls -al
tar -cf /home/b/a/backup/web/public_html/archive.tar home/*`;
echo "<pre>$output</pre>";
?>
I cant even view the files via SSH commands, an example of this is the test account. If I use the following command I am unable to view the website files.
<?php
$output = `cd /home/t/e/test/
ls -alRh`;
echo "<pre>$output</pre>";
?>
But if I use the same commands on the a different account I am able to see and download of the website files.
Is this a permission problem or am I missing something in my script?
Thanks
ls -l / | grep home
the output will be like this:
lrwxr-xr-x 1 root wheel 8 Mar 30 14:13 home -> usr/home
In my case, the owner is root, and the root user its primary group is wheel, so now we add www-data user to wheel group so he can list files in there:
usermod -a -G wheel www-data
You can download some files because they located in directory owned by www-data user, and when you can't, www-data has no permission in that.
I think it permission problem, try to give apache user(or what you set it) permission to read /home/* directory's.
To find the user name that used by apache service run this:
For linux:
egrep -iw --color=auto 'user|group' /etc/httpd/conf/httpd.conf
For FreeBSD:
egrep -iw --color=auto '^user|^group' /usr/local/etc/apache22/httpd.conf
My guess is that PHP is running in a chroot.
If you just want to execute a backup, consider doing it in a different language. Especially if it is just a sequence of UNIX commands, write a shell script. Perhaps more details on what this script will be used for and who is providing and maintaining your hosting will be useful.