Showing posts with label passwords. Show all posts

Thursday, 1 November 2018

Securing Glassfish

As written in my previous blogpost, I mentioned securing Glassfish.

Here are the steps I took. I plan to add more steps, if I find them.

change the default passwords

a no-brainer, I think

do not run glassfish as root

I already did that, but I just mention it here. If you need to have it listening to port 80, there are plenty of ways to do that without running glassfish as root.

make sure the user running glassfish has /sbin/nologin as a login shell

so nobody can get shell access, unless you use another account¹.

Also means if we need to access the account ourselves, we could run:

sudo -u glassfish /bin/bash

turn off admin console access from outside the server

Go to Configuration -> server-config -> Network Config -> Network Listeners -> admin-listener.

Under the General tab, in the Address: field replace 0.0.0.0 to 127.0.0.1

Restart the server

You can access the admin console using an ssh tunnel⁶:

[user@localhost ~]$ ssh user@mysite.com -L 4848:localhost:4848 -N

The first 4848 is the port of your homepc. The second 4848 is the remote port. And then connecting your browser to localhost:4848.

make sure only the essentials are accessible from outside the server

an application server has a very high number of open ports, many of them are only required for local access. Verifying this can be done with the following command:

[root ~]# netstat -tulpen
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       User       Inode      PID/Program name
tcp        0      0 0.0.0.0:7676            0.0.0.0:*               LISTEN      1002       8518781    14140/java
tcp        0      0 0.0.0.0:42853           0.0.0.0:*               LISTEN      1002       9560152    14140/java
tcp        0      0 0.0.0.0:44425           0.0.0.0:*               LISTEN      1002       9560153    14140/java
tcp        0      0 0.0.0.0:45613           0.0.0.0:*               LISTEN      1002       9560151    14140/java
tcp        0      0 0.0.0.0:8686            0.0.0.0:*               LISTEN      1002       8518047    14140/java
tcp        0      0 0.0.0.0:4848            0.0.0.0:*               LISTEN      1002       8517513    14140/java
tcp        0      0 0.0.0.0:8080            0.0.0.0:*               LISTEN      1002       8516146    14140/java
tcp        0      0 0.0.0.0:3700            0.0.0.0:*               LISTEN      1002       8516151    14140/java
tcp        0      0 0.0.0.0:8181            0.0.0.0:*               LISTEN      1002       8516148    14140/java
tcp        0      0 0.0.0.0:41593           0.0.0.0:*               LISTEN      1002       8517967    14140/javat

port	type	comments
7676		Message Queue Port
42853
44425
45613
8686	Pure JMX Clients Port
4848	the administration console	set it to localhost, and connect using ssh tunnel
8080	the normal http listener	this should be accessible from outside the server
3700	IIOP Port ("ORB listener 1")
8181	the normal https listener	this should be accessible from outside the server
41593

This can be either done by changing the ip address in the configuration of the glassfish server to 127.0.0.1 instead of 0.0.0.0.

But it could also be done by adding firewall rules, disallowing incoming traffic to ports you do not approve.

However, why not do both?

turn off autodeployments²

asadmin set server.admin-service.das-config.autodeploy-enabled=false

dynamic-reload-enabled² is another useful one to turn on and off in this manner

asadmin set server.admin-service.das-config.dynamic-reload-enabled=false

hide your identity

glassfish response headers contain information on what server you are running, what version, what frameworks, etc. You can turn this option off by following instructions of reference 3. Has some other excellent advice as well.

make sure any database access used by glassfish is as restricted as possible

usually it is enough to create a database user that has only access to one specific database^{4 5}

add a second admin user account for accessing the glassfish admin console

just in case of problems

make sure the user running the glassfish has files with as restricted rights as possible

there is no reason for "other" and "group" to have any access.

References

[1] StackExchange - Unix&Linux - Does /usr/sbin/nologin as a login shell serve a security purpose?: https://unix.stackexchange.com/questions/155139/does-usr-sbin-nologin-as-a-login-shell-serve-a-security-purpose
[2] GlassFish Server Open Source Edition - Application Deployment Guide - Release 5.0: https://javaee.github.io/glassfish/doc/5.0/application-deployment-guide.pdf
[3] Securing your GlassFish. Hardening Guide: http://blog.eisele.net/2011/05/securing-your-glassfish-hardening-guide.html
[4] How to create a user in MySQL/MariaDB and grant permissions on a specific database: http://www.daniloaz.com/en/how-to-create-a-user-in-mysql-mariadb-and-grant-permissions-on-a-specific-database/
[5] MariaDB - SET PASSWORD: https://mariadb.com/kb/en/library/set-password/
[6] Frank Wiles - Quick-Tip: SSH Tunneling Made Easy: https://www.revsys.com/writings/quicktips/ssh-tunnel.html
Fine Tuning Payara Server in Production: https://blog.payara.fish/fine-tuning-payara-server-in-production
Bug 1530511 - rocksdb appears under "show databases": https://bugzilla.redhat.com/show_bug.cgi?id=1530511

Saturday, 6 October 2018

SSH Key-Based Authentication

I'm using reference [1] almost exclusively, it is easy to follow and very well written. The reason I am writing stuff down here, is in the case the referenced article goes offline.

Generating Keys

[mrbear@localhost ~]$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/mrbear/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Passphrases do not match. Try again.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/mrbear/.ssh/id_rsa.
Your public key has been saved in /home/mrbear/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:etv4wn8 4843n3v48nvan80avw2408a4vn588an04845 mrbear@localhost.localdomain
The key's randomart image is:
+--[ RSA 2048]----+
| ..o |
| E o= . |
| o. o |
| .. |
| ..S |
| o o. |
| =o.+. |
|. =++.. |
|o=++. |
+-----------------+
[mrbear@localhost ~]$

Copying keys to the server

[mrbear@localhost ~]$ ssh-copy-id mrbear@www.mysite.org
The authenticity of host 'www.mysite.org (10.0.0.11)' can't be established.
ECDSA key fingerprint is SHA256:B&B(&BSf7bFSfb7fF&SFb7SF&tFibFuSOWWFuFBUf76.
Are you sure you want to continue connecting (yes/no)? yes
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
mrbear@www.mysite.org's password:

Number of key(s) added: 1

Now try logging into the machine, with: "ssh 'mrbear@www.mysite.org'"
and check to make sure that only the key(s) you wanted were added.

[mrbear@localhost ~]$

Logging in

[mrbear@localhost ~]$ ssh mrbear@www.mysite.org
Last login: Mon Sep 24 21:01:12 2018

Add to sudoers file

Found how to do this at [2].

[root@mysite ~]# usermod -aG wheel mrbear

Disabling Password Authentication

Edit the file /etc/ssh/sshd_config.

# To disable tunneled clear text passwords, change to no here!
#PasswordAuthentication yes
#PermitEmptyPasswords no
PasswordAuthentication no

# systemctl restart sshd.service

Now what you get when you try is:

$ ssh -l root www.mysite.org root@www.mysite.org: Permission denied (publickey,gssapi-keyex,gssapi-with-mic).

Thank the heavens I no longer have to worry about messages as the one below:

root@mysite's password:
Last failed login: Sat Oct 6 10:12:48 CEST 2018 from 10.0.0.1 on ssh:notty
There were 56310 failed login attempts since the last successful login.
Last login: Tue Oct 2 23:23:41 2018
[root@mysite ~]#

I originally had installed fail2ban, as a way to protect against a password-based attack, but even the man page of fail2ban³ indicates that the above way is pretty much better.

References

[1] Digital Ocean - How To Configure SSH Key-Based Authentication on a Linux Server: https://www.digitalocean.com/community/tutorials/how-to-configure-ssh-key-based-authentication-on-a-linux-server
[2] Top 20 OpenSSH Server Best Security Practices: https://www.cyberciti.biz/tips/linux-unix-bsd-openssh-server-best-practices.html
[3] Fail2ban: https://www.fail2ban.org/wiki/index.php/Main_Page
How to disable ssh password login on Linux to increase security: https://www.cyberciti.biz/faq/how-to-disable-ssh-password-login-on-linux/

Thursday, 19 November 2015

Linux Commandline Password Manager

Recently I was looking for a good Password Manager, as the number of passwords I need to maintain is growing steadily (I'm sure everyone knows how it is).

The one I found ("pass² - the standard unix password manager"), the one I am talking about, exemplifies the Unix philosophy⁰. Which is:

Do One Thing and Do It Well.

Write programs to work together.

Write programs to handle text streams, because that is a universal interface.

The password manager actually basically doesn't do anything itself, but delegates to other parts of the Linux system, namely the filesystem, and GPG for encryption, pwgen for the generation of random passwords, xclip for interfacing with the clipboard and (optionally) Git for version control.

It does mean that you have to setup Gnu Private Guard properly, before you can start using "pass", hence the next chapter.

Gnu Private Guard

“GnuPG¹ is a complete and free implementation of the OpenPGP standard as defined by RFC4880 (also known as PGP).”

Creating a key

All keys are stored in .gnupg.

bash-4.3$ gpg2 --full-gen-key
gpg (GnuPG) 2.1.7; Copyright (C) 2015 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

gpg: directory '/home/mrbear/.gnupg' created
gpg: new configuration file '/home/mrbear/.gnupg/gpg.conf' created
gpg: WARNING: options in '/home/mrbear/.gnupg/gpg.conf' are not yet active during this run
gpg: keybox '/home/mrbear/.gnupg/pubring.kbx' created
Please select what kind of key you want:
(1) RSA and RSA (default)
(2) DSA and Elgamal
(3) DSA (sign only)
(4) RSA (sign only)
Your selection? 2

I have decided to follow the advice of the website¹ and take 2.

DSA keys may be between 1024 and 3072 bits long.
What keysize do you want? (2048)

I take 2048, it seems fairly default.

Requested keysize is 2048 bits
Please specify how long the key should be valid.
0 = key does not expire
= key expires in n days
w = key expires in n weeks
m = key expires in n months
y = key expires in n years
Key is valid for? (0)
Key does not expire at all
Is this correct? (y/N) Y

GnuPG needs to construct a user ID to identify your key.

Real name: mrbear
Email address: mrbear@localhost.com
Comment: mrbear
You selected this USER-ID:
"mrbear (mrbear) "

Change (N)ame, (C)omment, (E)mail or (O)kay/(Q)uit?

And away we go!

We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.
gpg: WARNING: some OpenPGP programs can't handle a DSA key with this digest size
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.
gpg: /home/mrbear/.gnupg/trustdb.gpg: trustdb created
gpg: key 3A4CFDFE marked as ultimately trusted
gpg: directory '/home/mrbear/.gnupg/openpgp-revocs.d' created
public and secret key created and signed.

gpg: checking the trustdb
gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model
gpg: depth: 0 valid: 1 signed: 0 trust: 0-, 0q, 0n, 0m, 0f, 1u
pub dsa2048/3A4CFDFE 2015-10-14
Key fingerprint = 7FCC 07FA A6BE 32DE A971 2281 587B D827 3A4C FDFE
uid [ultimate] mrbear (mrbear)
sub elg2048/0B94C819 2015-10-14

So, just to check:

bash-4.3$ gpg2 --list-keys
/home/mrbear/.gnupg/pubring.kbx
---------------------------------
pub dsa2048/3A4CFDFE 2015-10-14
uid [ultimate] mrbear (mrbear)
sub elg2048/0B94C819 2015-10-14

Password store

Apparently, initialising the store needs to be done with the name of the key generated above.

bash-4.3$ sudo dnf install pass
...
bash-4.3$ pass init "3A4CFDFE"
mkdir: created directory ‘/home/mrbear/.password-store/’
Password store initialized for 3A4CFDFE

And I wish to use Git, because I'm that kinda guy.

bash-4.3$ pass git init
Initialized empty Git repository in /home/mrbear/.password-store/.git/
[master (root-commit) 77cc085] Add current contents of password store.
1 file changed, 1 insertion(+)
create mode 100644 .gpg-id
[master 6655058] Configure git repository for gpg file diff.
1 file changed, 1 insertion(+)
create mode 100644 .gitattributes

Adding my passwords

For example, my email:

bash-4.3$ pass insert Email/mail.localhost.com
mkdir: created directory ‘/home/mrbear/.password-store/Email’
Enter password for Email/mail.localhost.com:
Retype password for Email/mail.localhost.com:
[master 40d6094] Add given password for Email/mail.localhost.com to store.
1 file changed, 0 insertions(+), 0 deletions(-)
create mode 100644 Email/mail.localhost.com.gpg

Adding parameter --multiline makes it possible to not only add your password but other stuff as well. Handy if the userid/username is not standard my email address.

Showing passwords

bash-4.3$ pass
Password Store
└── Email
└── mail.localhost.com

Generating passwords

bash-4.3$ pass generate Internet/sync.firefox.com 16
mkdir: created directory ‘/home/mrbear/.password-store/Internet’
[master 9b966af] Add generated password for Internet/sync.firefox.com.
1 file changed, 0 insertions(+), 0 deletions(-)
create mode 100644 Internet/sync.firefox.com.gpg
The generated password for Internet/sync.firefox.com is:
\$%R&E%&8^BA/

Some websites do not accept "odd" characters (< > ! @ # $ % ^ & * _) when it comes to passwords. When adding the "[--no-symbols,-n]" option you get a generated password containing only letters, capitals and digits.

Showing passwords and copying to clipboard

bash-4.3$ pass -c Email/mail.localhost.com
Copied Email/mail.localhost.com to clipboard. Will clear in 45 seconds.

Getting your stuff back

As basically this awesome password manager stored the passwords as a bunch of GPG2 encrypted files in .password-store, we should be able to decrypt the files directly.

This would work as follows:

bash-4.3$ gpg2 --decrypt .password-store/Email/mail.localhost.com.gpg
gpg: encrypted with 2048-bit ELG key, ID 0B94C819, created 2015-10-14
"mrbear (mrbear) "
itsasecret!

Syncing the git

As I wish to manage my passwords from multiple computers, there's a need to sync/merge the git repositories⁵ from time to time.

First is, of course, the copying of the GPG keys by copying the .gnupg directory.

scp -r .gnupg mrbear@toby:/home/mrbear

From the second machine, from my homedirectory:

git clone ssh://mrbear@sherlock/home/mrbear/.password-store
Cloning into '.password-store'...

After that it is nothing more but a "git pull" or "git push" whenever I need it.

References

[0] Wikipedia - Unix philosophy: https://en.wikipedia.org/wiki/Unix_philosophy
[1] GnuPG: https://www.gnupg.org/documentation/howtos.html
[2] Password store: http://www.passwordstore.org/
[3] Linux Crypto: Passwords: http://blog.sanctum.geek.nz/linux-crypto-passwords/
[4] StackExchange Unix - I try to add passwords to the pass password managers but my attempts fail: http://unix.stackexchange.com/questions/53912/i-try-to-add-passwords-to-the-pass-password-manager-but-my-attempts-fail-with
[5] Git - Git Basics Working with Remotes: https://git-scm.com/book/en/v2/Git-Basics-Working-with-Remotes
Fedora Magazine - GPG: a Fedora primer: https://fedoramagazine.org/gnupg-a-fedora-primer/
Fedora Magazine - GPG key management, part 1: https://fedoramagazine.org/gpg-key-management-part-1/