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Nächste Überarbeitung		Vorhergehende Überarbeitung
it-wiki:linux:ssh_chrooted_jail [2021/03/10 20:31] – [Step 4: Configure SSH to Use Chroot Jail] markoit-wiki:linux:ssh_chrooted_jail [2021/03/10 21:06] (aktuell) – [Step 7. Testing SFTP with Chroot Jail] marko
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 # ls -l /dev/{null,zero,stdin,stdout,stderr,random,tty} # ls -l /dev/{null,zero,stdin,stdout,stderr,random,tty}
 </code> </code>
-{{ :it-wiki:linux:listing-required-files.png |}}+{{ :it-wiki:linux:listing-required-files.png?nolink |}}
  
 **3.** Now, create the ''/dev'' files as follows using the **mknod command**. In the command below, the ''-m'' flag is used to specify the file permissions bits, ''c'' means character file and the two numbers are major and minor numbers that the files point to. **3.** Now, create the ''/dev'' files as follows using the **mknod command**. In the command below, the ''-m'' flag is used to specify the file permissions bits, ''c'' means character file and the two numbers are major and minor numbers that the files point to.
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 # mknod -m 666 random c 1 8 # mknod -m 666 random c 1 8
 </code> </code>
-{{ :it-wiki:linux:create-required-files.png |}}+{{ :it-wiki:linux:create-required-files.png?nolink |}}
  
 **4.** Afterwards, set the appropriate permission on the chroot jail. Note that the chroot jail and its subdirectories and subfiles must be owned by **root** user, and not writable by any normal user or group: **4.** Afterwards, set the appropriate permission on the chroot jail. Note that the chroot jail and its subdirectories and subfiles must be owned by **root** user, and not writable by any normal user or group:
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 # ls -ld /home/test # ls -ld /home/test
 </code> </code>
-{{ :it-wiki:linux:set-permission-on-directory.png |}}+{{ :it-wiki:linux:set-permission-on-directory.png?nolink |}}
  
 ==== Step 2: Setup Interactive Shell for SSH Chroot Jail ==== ==== Step 2: Setup Interactive Shell for SSH Chroot Jail ====
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 # cp -v /bin/bash /home/test/bin/ # cp -v /bin/bash /home/test/bin/
 </code> </code>
-{{ :it-wiki:linux:copy-bin-files.png |}}+{{ :it-wiki:linux:copy-bin-files.png?nolink |}}
  
 **6.** Now, identify bash required shared ''libs'', as below and copy them into the ''lib'' directory: **6.** Now, identify bash required shared ''libs'', as below and copy them into the ''lib'' directory:
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 # cp -v /lib64/{libtinfo.so.5,libdl.so.2,libc.so.6,ld-linux-x86-64.so.2} /home/test/lib64/ # cp -v /lib64/{libtinfo.so.5,libdl.so.2,libc.so.6,ld-linux-x86-64.so.2} /home/test/lib64/
 </code> </code>
-{{ :it-wiki:linux:copy-shared-library-files.png |}}+{{ :it-wiki:linux:copy-shared-library-files.png?nolink |}}
  
 ==== Step 3: Create and Configure SSH User ==== ==== Step 3: Create and Configure SSH User ====
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 # cp -vf /etc/{passwd,group} /home/test/etc/ # cp -vf /etc/{passwd,group} /home/test/etc/
 </code> </code>
-{{ :it-wiki:linux:copy-password-files.png |}}+{{ :it-wiki:linux:copy-password-files.png?nolink |}}
  
 **<color red>Note</color>**: Each time you add more SSH users to the system, you will need to copy the updated account files into the ''/home/test/etc'' directory. **<color red>Note</color>**: Each time you add more SSH users to the system, you will need to copy the updated account files into the ''/home/test/etc'' directory.
  
 ==== Step 4: Configure SSH to Use Chroot Jail ==== ==== Step 4: Configure SSH to Use Chroot Jail ====
-9. Now, open the ''sshd_config'' file.+**9.** Now, open the ''sshd_config'' file.
 <code bash> <code bash>
 # vi /etc/ssh/sshd_config # vi /etc/ssh/sshd_config
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 </code> </code>
 {{ :it-wiki:linux:configure-ssh-chroot-jail.png?nolink |}} {{ :it-wiki:linux:configure-ssh-chroot-jail.png?nolink |}}
 +
 +Save the file and exit, and restart the SSHD services:
 +<code bash>
 +# systemctl restart sshd
 +</code>
 +
 +==== Step 5: Testing SSH with Chroot Jail ====
 +**10.** At this point, test if the chroot jail setup is working as expected:
 +<code bash>
 +# ssh tecmint@192.168.0.10
 +-bash-4.1$ ls
 +-bash-4.1$ date
 +-bash-4.1$ uname
 +</code>
 +{{ :it-wiki:linux:testing-ssh-user-chroot-jail.png?nolink |}}
 +
 +From the screenshot above, we can see that the SSH user is locked in the chrooted jail, and can’t run any external commands (ls, date, uname etc).
 +
 +The user can only execute bash and its builtin commands such as(pwd, history, echo etc) as seen below:
 +<code bash>
 +# ssh tecmint@192.168.0.10
 +-bash-4.1$ pwd
 +-bash-4.1$ echo "Tecmint - Fastest Growing Linux Site"
 +-bash-4.1$ history
 +</code>
 +{{ :it-wiki:linux:ssh-builtin-commands.png?nolink |}}
 +
 +==== Step 6. Create SSH User’s Home Directory and Add Linux Commands ====
 +**11.** From the previous step, we can notice that the user is locked in the root directory, we can create a home directory for the the SSH user like so (do this for all future users):
 +<code bash>
 +# mkdir -p /home/test/home/tecmint
 +# chown -R tecmint:tecmint /home/test/home/tecmint
 +# chmod -R 0700 /home/test/home/tecmint
 +</code>
 +{{ :it-wiki:linux:create-ssh-user-home-directory.png?nolink |}}
 +
 +**12.** Next, install a few user commands such as ls, date, mkdir in the ''bin'' directory:
 +<code bash>
 +# cp -v /bin/ls /home/test/bin/
 +# cp -v /bin/date /home/test/bin/
 +# cp -v /bin/mkdir /home/test/bin/
 +</code>
 +{{ :it-wiki:linux:add-commands-to-ssh-user.png?nolink |}}
 +
 +**13.** Next, check the shared libraries for the commands above and move them into the chrooted jail libraries directory:
 +<code bash>
 +# ldd /bin/ls
 +# cp -v /lib64/{libselinux.so.1,libcap.so.2,libacl.so.1,libc.so.6,libpcre.so.1,libdl.so.2,ld-linux-x86-64.so.2,libattr.so.1,libpthread.so.0} /home/test/lib64/
 +</code>
 +{{ :it-wiki:linux:copy-shared-libraries.png?nolink |}}
 +
 +==== Step 7. Testing SFTP with Chroot Jail ====
 +**14.** Do a final test using sftp; check if the commands you have just installed are working.
 +
 +Add the line below in the ''/etc/ssh/sshd_config'' file:
 +<code bash>
 +#Enable sftp to chrooted jail 
 +ForceCommand internal-sftp
 +</code>
 +
 +Save the file and exit. Then restart the SSHD services:
 +<code bash>
 +# systemctl restart sshd
 +</code>
 +
 +**15.** Now, test using SSH, you’ll get the following error:
 +<code bash>
 +# ssh tecmint@192.168.0.10
 +</code>
 +{{ :it-wiki:linux:test-ssh-chroot-jail.png?nolink |}}
 +
 +Try using SFTP as follows:
 +<code>
 +# sftp tecmint@192.168.0.10
 +</code>
 +{{ :it-wiki:linux:testing-sftp-ssh-user.png?nolink |}}
 +
it-wiki/linux/ssh_chrooted_jail.1615408316.txt.gz · Zuletzt geändert: von marko