Categories
Linux Security Windows

Securing SSH with Yubikey using WSL

If using Windows, start with downloading Gpg4Win and Kleopatra. As i use Windows Terminal I wont be downloading Putty. After the installation of these two, open the configuration files of the gpg-agent and scdaemon and append the following:

# C:\Users\<username>\AppData\Roaming\gnupg\gpg-agent.conf
enable-putty-support
enable-ssh-support

You can also to this with powershell, using the following command:

Add-Content $env:APPDATA\gnupg\gpg-agent.conf "enable-putty-support"
Add-Content $env:APPDATA\gnupg\gpg-agent.conf "enable-ssh-support"

Add-Content $env:APPDATA\gnupg\scdaemon.conf "debug-level guru"
Add-Content $env:APPDATA\gnupg\scdaemon.conf "log-file scdaemon.log"
Add-Content $env:APPDATA\gnupg\scdaemon.conf "reader-port Yubico Yubi"

Restart the agent with the following commands:

gpgconf --kill gpg-agent
gpg-connect-agent /bye

Open up Powershell and check if the Yubikey is visible to the system. You should get output similair to this:

PS C:\Users\wiege> gpg --card-status
Reader ...........: Yubico YubiKey OTP FIDO CCID 0
Application ID ...: < .... >
Application type .: OpenPGP
Version ..........: 3.4
Manufacturer .....: Yubico
Serial number ....: < .... >
Name of cardholder: < .... >
Language prefs ...: < .... >
Salutation .......: < .... >
URL of public key : [not set]
Login data .......: < .... >
Signature PIN ....: not forced
Key attributes ...: < .... >
Max. PIN lengths .: < .... >
PIN retry counter : 3 3 3
Signature counter : 0
KDF setting ......: off

When you open Kleopatra and go to Smartcards, you should also see your Yubikey present. If your Yubikey is new, there are no keys listed and you need to create them. This can be done several ways, through Kleopatra or on CLI (i prefer CLI as it provides more options).

Open up CMD or Powershell and use gpg to generate your new key:

$ gpg --expert --full-generate-key

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)
   (7) DSA (set your own capabilities)
   (8) RSA (set your own capabilities)
   (9) ECC and ECC
  (10) ECC (sign only)
  (11) ECC (set your own capabilities)
  (13) Existing key
Your selection? 11

Possible actions for a RSA key: Sign Certify Encrypt Authenticate
Current allowed actions: Sign Certify Encrypt

   (S) Toggle the sign capability
   (E) Toggle the encrypt capability
   (A) Toggle the authenticate capability
   (Q) Finished

Your selection? E

Possible actions for a RSA key: Sign Certify Encrypt Authenticate
Current allowed actions: Sign Certify

   (S) Toggle the sign capability
   (E) Toggle the encrypt capability
   (A) Toggle the authenticate capability
   (Q) Finished

Your selection? S

Possible actions for a RSA key: Sign Certify Encrypt Authenticate
Current allowed actions: Certify

   (S) Toggle the sign capability
   (E) Toggle the encrypt capability
   (A) Toggle the authenticate capability
   (Q) Finished

Your selection? Q

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

It will ask you for your name and emailadress, fill those in and conform with (O). Verify if your key has been generated:

$ gpg --list-keys
------------------------------------------------
pub   ed25519 2022-11-15 [C]
      E6444634F7318577BA18F43201A0XXXXXXXXXX

If you use Linux, you can export the key id (to be used for later)

export KEYID=E6444634F7318577BA18F43201A0XXXXXXXXXX

Now edit the master key and start adding sub-keys for encryption/signing and authentication:

$  gpg --expert --edit-key  E6444634F7318577BA18F43201A0XXXXXXXXXX
gpg (GnuPG) 2.3.8; Copyright (C) 2021 g10 Code GmbH
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Secret key is available.

sec  ed25519/01A0XXXXXXXXX
     created: 2022-11-15  expires: never       usage: C
     trust: ultimate      validity: ultimate

Add a new key for signing (and then repeat these for Encryption and Authentication):

gpg> addkey

gpg> addkey
Please select what kind of key you want:
   (3) DSA (sign only)
   (4) RSA (sign only)
   (5) Elgamal (encrypt only)
   (6) RSA (encrypt only)
   (7) DSA (set your own capabilities)
   (8) RSA (set your own capabilities)
  (10) ECC (sign only)
  (11) ECC (set your own capabilities)
  (12) ECC (encrypt only)
  (13) Existing key
  (14) Existing key from card
Your selection? 10

Please specify how long the key should be valid.
         0 = key does not expire
      <n>  = key expires in n days
      <n>w = key expires in n weeks
      <n>m = key expires in n months
      <n>y = key expires in n years
Key is valid for? (0) 1y
Key expires at xxxxxxxxxxxxxxxxxxx
Is this correct? (y/N) y
Really create? (y/N) y
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.

Again: Repeat for Encryption and Authentication, then use 'save'.

If you wish to add more e-mail addresses, use adduid to them. End result should look like this:

$ gpg -K

sec   ed25519 2022-11-15 [C]
      E6444634F7318577BA18F4XXXXXXXXXXXXXXXXXX
uid           [ultimate] Wieger Bontekoe <[email protected]>
uid           [ultimate] Wieger Bontekoe <[email protected]>
ssb   ed25519 2022-11-15 [S] [expires: 2027-11-14]
ssb   cv25519 2022-11-15 [E] [expires: 2027-11-14]
ssb   ed25519 2022-11-15 [A] [expires: 2027-11-14]

Now export everything, once you have moved them to Yubikey you can't anymore. 

$ gpg --armor --export-secret-keys E6444634F7318577BA18F4XXXXXXXXXXXXXXXXXX
 > ./master.key
# Also do all the subs like this, repeat for all of them!
$ gpg --armor --export-secret-subkeys < SUBKEYID > ./sub1.key

You can also do this from Kleopatra if using windows, that is a lot simpler. Just go to 'certificates', right click the certificate and go to 'Details'. Under details go to 'more details'. Here you will see 4 certificates that you can export using right click.

Backup these files, you should never loose them. Now, transfer the keys to Yubikey!

$ gpg --edit-key E6444634F7318577BA18F4XXXXXXXXXXXXXXXXXX
gpg> key 1
gpg> keytocard
Please select where to store the key:
   (1) Signature key
   (3) Authentication key
Your selection? 1
gpg> key 1
gpg> key 2
gpg> keytocard
Please select where to store the key:
   (2) Encryption key
Your selection? 2
gpg> key 2
gpg> key 3
Please select where to store the key:
   (3) Authentication key
Your selection? 3

gpg> save

Now verify if the sub-keys were really moved

$ gpg --card-status
Reader ...........: Yubico YubiKey OTP FIDO CCID 0
Application ID ...: < .... >
Application type .: OpenPGP
Version ..........: 3.4
Manufacturer .....: Yubico
Serial number ....: < .... >
Name of cardholder: < .... >
Language prefs ...: < .... >
Salutation .......: < .... >
URL of public key : [not set]
Login data .......: < .... >
Signature PIN ....: not forced
Key attributes ...: < .... >
Max. PIN lengths .: < .... >
PIN retry counter : 3 3 3
Signature counter : 0
KDF setting ......: off
UIF setting ......: Sign=off Decrypt=off Auth=off
Signature key ....: 4B3C 6B30 B22F 9C3E F196  D72D DE7D 3E9F XXXX XXXX
      created ....: 2022-11-15 07:14:18
Encryption key....: 30CE FB8F 54E6 0E63 93D3  9D6B A29B E406 XXXX XXXX
      created ....: 2022-11-15 07:14:48
Authentication key: 2477 02D2 511B 5407 F9A3  6005 DF86 A2D3 XXXX XXXX
      created ....: 2022-11-15 07:15:07

PGP Part, all set! Let's check if we have an up to date version of openssh that supports ecdsa-sk:

$ ssh-keygen --help
unknown option -- -
usage: ssh-keygen [-q] [-a rounds] [-b bits] [-C comment] [-f output_keyfile]
                  [-m format] [-N new_passphrase] [-O option]
                  [-t dsa | ecdsa | ecdsa-sk | ed25519 | ed25519-sk | rsa]
                  [-w provider] [-Z cipher]

If you do not see the '-sk' option you need to upgrade openssh. Generate a new key using ed25519-sk and it will ask your verification using Yubikey:

$ ssh-keygen -t ed25519-sk -f ~/.ssh/mynewkey
Generating public/private ed25519-sk key pair
You may need to touch your authenticator to authorize key generation.

Just touch the metal circle and it’ll bind the SSH key pair to your Yubikey.

When it says “Enter passphrase (empty for no passphrase)”, you can just press enter to leave it empty. If you use linux, now copy your private key to your server (Windows doesn't support this, you have to do that by hand).

Now when you would ssh to that host it should ask verification:

Categories
Linux

Regenerate Dockerfile from a Docker Image

It may happen that you have accidentally deleted your Dockerfile, or that you want to know how a Docker was built to learn from it. In this case it is useful to see what the Dockerfile looked like, which files have been modified or copied, and which packages have been installed.

With the command below you can easily view the Docker file of an image (run as root):

alias dfimage="docker run -v /var/run/docker.sock:/var/run/docker.sock --rm alpine/dfimage"
dfimage -sV=1.36 nginx:latest

The above commands show the steps from the Dockerfile:

[email protected]:~# alias dfimage="docker run -v /var/run/docker.sock:/var/run/docker.sock --rm alpine/dfimage"
[email protected]:~# dfimage -sV=1.36 nginx:latest
Unable to find image 'alpine/dfimage:latest' locally
latest: Pulling from alpine/dfimage
Status: Downloaded newer image for alpine/dfimage:latest
latest: Pulling from library/nginx
[..]
Status: Downloaded newer image for nginx:latest
Analyzing nginx:latest
Docker Version: 20.10.7
GraphDriver: overlay2
Environment Variables
|PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
|NGINX_VERSION=1.21.5
|NJS_VERSION=0.7.1
|PKG_RELEASE=1~bullseye

Open Ports
|80

Image user
|User is root

Potential secrets:
Dockerfile:
CMD ["bash"]
LABEL maintainer=NGINX Docker Maintainers <[email protected]>
ENV NGINX_VERSION=1.21.5
ENV NJS_VERSION=0.7.1
ENV PKG_RELEASE=1~bullseye

COPY file:65504f71f5855ca017fb64d502ce873a31b2e0decd75297a8fb0a287f97acf92 in /
        docker-entrypoint.sh

COPY file:0b866ff3fc1ef5b03c4e6c8c513ae014f691fb05d530257dfffd07035c1b75da in /docker-entrypoint.d
        docker-entrypoint.d/
        docker-entrypoint.d/10-listen-on-ipv6-by-default.sh

COPY file:0fd5fca330dcd6a7de297435e32af634f29f7132ed0550d342cad9fd20158258 in /docker-entrypoint.d
        docker-entrypoint.d/
        docker-entrypoint.d/20-envsubst-on-templates.sh

COPY file:09a214a3e07c919af2fb2d7c749ccbc446b8c10eb217366e5a65640ee9edcc25 in /docker-entrypoint.d
        docker-entrypoint.d/
        docker-entrypoint.d/30-tune-worker-processes.sh

ENTRYPOINT ["/docker-entrypoint.sh"]
EXPOSE 80
STOPSIGNAL SIGQUIT
CMD ["nginx" "-g" "daemon off;"]

[email protected]:~#

To keep it readable I've cut bits out of the output, but I suspect the idea is clear. This cannot be copied 1 on 1, but a Dockerfile can simply be rebuilt on the basis of this.

Categories
Linux

Clear and wipe all docker containers

docker update --restart=no $(docker ps -a -q)
docker stop $(docker ps -a -q)
docker rm $(docker ps -a -q)
Categories
Linux

SPF and DKIM with Postfix

SPF (Sender Policy Framework) record specifies which hosts or IP addresses are allowed to send emails on behalf of a domain. You should allow only your own email server or your ISP’s server to send emails for your domain.

DKIM (DomainKeys Identified Mail) uses a private key to add a signature to emails sent from your domain. Receiving SMTP servers verify the signature by using the corresponding public key, which is published in your DNS manager.

Create SPF record in DNS zone

n your DNS management interface, create a new TXT record like below.

TXT  @   v=spf1 mx ~all

Some DNS managers require you to wrap the SPF record with quotes like below.

TXT  @   "v=spf1 mx ~all"

Keep in mind that it can take up to an hour for the new record to be available.

Configure Postfix for SPF

First, install required packages:

sudo apt install postfix-policyd-spf-python

Edit the Postfix master process configuration file located at /etc/postfix/master.cf. Add these lines to the end:

policyd-spf  unix  -       n       n       -       0       spawn
    user=policyd-spf argv=/usr/bin/policyd-spf

Now open up the configuration file at /etc/postfix/main.cf. Add these lines to the end of the file:

policyd-spf_time_limit = 3600
smtpd_recipient_restrictions =
   permit_mynetworks,
   permit_sasl_authenticated,
   reject_unauth_destination,
   check_policy_service unix:private/policyd-spf

Now restart postfix

sudo systemctl restart postfix

Configure DKIM

sudo apt install opendkim opendkim-tools

Add the Postfix user to the OpenDKIM group

sudo gpasswd -a postfix opendkim

Now open the configuration of OpenDKIM and enable or add these lines:

Canonicalization   simple
Mode               sv
SubDomains         no
AutoRestart         yes
AutoRestartRate     10/1M
Background          yes
DNSTimeout          5
SignatureAlgorithm  rsa-sha256

Go to the end of the file and add these lines: 

#OpenDKIM user
# Remember to add user postfix to group opendkim
UserID             opendkim

# Map domains in From addresses to keys used to sign messages
KeyTable           refile:/etc/opendkim/key.table
SigningTable       refile:/etc/opendkim/signing.table

# Hosts to ignore when verifying signatures
ExternalIgnoreList  /etc/opendkim/trusted.hosts

# A set of internal hosts whose mail should be signed
InternalHosts       /etc/opendkim/trusted.hosts

We will need to create the signing table, key table and the trusted hosts file. 

sudo mkdir /etc/opendkim
sudo mkdir /etc/opendkim/keys
sudo chown -R opendkim:opendkim /etc/opendkim
sudo chmod go-rw /etc/opendkim/keys

Now create the signing table, using your domain. Open the file and add the second line in it:

sudo nano /etc/opendkim/signing.table
*@bontekoe.technology    default._domainkey.bontekoe.technology

Now create the key table

sudo nano /etc/opendkim/key.table
default._domainkey.bontekoe.technology     bontekoe.technology:default:/etc/opendkim/keys/bontekoe.technology/default.private

Now create the trusted hosts file:

sudo nano /etc/opendkim/trusted.hosts
127.0.0.1
localhost

*.bontekoe.technology

Generating DKIM Keypair

Create a separate folder for the domain.

sudo mkdir /etc/opendkim/keys/bontekoe.technology

Generate keys using opendkim-genkey tool.

sudo opendkim-genkey -b 2048 -d bontekoe.technology -D /etc/opendkim/keys/bontekoe.technology -s default -v
sudo chown opendkim:opendkim /etc/opendkim/keys/bontekoe.technology/default.private

Display the public key that was generated:

sudo cat /etc/opendkim/keys/bontekoe.technology/default.txt

This file contains the entire DNS record that should be published. Copy everything, startking with the v=DKIM1 and in your DNS record. After 15 minutes, test is the record has been successfully published:

sudo opendkim-testkey -d bontekoe.technology -s default -vvv

Result:

opendkim-testkey: using default configfile /etc/opendkim.conf
opendkim-testkey: checking key 'default._domainkey.bontekoe.technology'
opendkim-testkey: key secure
opendkim-testkey: key OK

Connecting Postfix to OpenDKIM

sudo mkdir /var/spool/postfix/opendkim
sudo chown opendkim:postfix /var/spool/postfix/opendkim

Open the configuration file at /etc/opendkim.conf, replace the socket (if defined, or add it):

Socket    local:/var/spool/postfix/opendkim/opendkim.sock

Open /etc/postfix/main.cf and add the following to the end:

# Milter configuration
milter_default_action = accept
milter_protocol = 6
smtpd_milters = local:opendkim/opendkim.sock
non_smtpd_milters = $smtpd_milters

Now restart Postfix and OpenDKIM:

sudo systemctl restart opendkim postfix

Categories
Linux

Apply Database Partitions to a live Zabbix database – without downtime

Due to the growth of our database (> 1TB), the 'housekeeper' no longer worked properly. The best solution to this problem is to apply Database Partitioning, however with a database of this size this takes a lot of time if you want to keep the data. We tried this action in several ways, the one below was the only way we were able to implement partitioning without downtime.

The example below must be repeated for each table and takes several hours per table.

# Create temporary partition 
CREATE TABLE `history_log_tmp` LIKE `history_log`;
# Apply partitioning
CALL partition_maintenance('zabbix', 'history_log_tmp', 30, 24, 3);

# Rename tables so the new empty table will be used by Zabbix. Leaving the old one as backup
BEGIN;
RENAME TABLE history_log TO history_backup_log;
RENAME TABLE history_log_tmp TO history_log;
COMMIT;

# Output all data from backup table to file
SELECT * INTO OUTFILE '/var/lib/mysql-files/history_backup_log.sql' FROM history_backup_log;

# Open MySQL Shell and start import
mysqlsh
shell.connect('localhost:3306')
util.importTable("/var/lib/mysql-files/history_backup_log.sql", {schema: "zabbix", table: "history_log", columns: ["itemid","clock","value","ns"], dialect: "default", skipRows: 0, showProgress: true, fieldsOptionallyEnclosed: false, linesTerminatedBy: "\n",threads: 2, bytesPerChunk: "50M", maxRate: "10M"})
Categories
Linux

How to Get the Size of all tables in a MySQL Database

SELECT
  TABLE_NAME AS `Table`,
  ROUND((DATA_LENGTH + INDEX_LENGTH) / 1024 / 1024) AS `Size (MB)`
FROM
  information_schema.TABLES
WHERE
  TABLE_SCHEMA = "zabbix"
ORDER BY
  (DATA_LENGTH + INDEX_LENGTH)
DESC;

Categories
Ansible Security

Ansible Tower – Custom Credentials Type

Within playbooks you occasionally connect to external applications or services, in my case Zabbix and ServiceNow. Because I also need login details and do not want to leave this plain text in playbooks, I use a 'Custom Credentials Type'. The advantage of this is that I can use the login details within a playbook (as a macro) and they are stored encrypted in Ansible Tower.

I first create a new credential type by defining the fields it will have and how these will be passed to my playbook. Credential types consist of two parts – “inputs” and “injectors“.

  • Inputs:
    define the value types that are used for this credential – such as a username, a password, a token, or any other identifier that’s part of the credential.
  • Injectors:
    describe how these credentials are exposed for Ansible (or us) to use – this can be Ansible extra variables, environment variables, or templated file content.

Both these configurations are specified as YAML or as JSON. In my case, the new credential type is called "ServiceNow" and i’m providing the instance, username and password as part of this credential type:

fields:
  - id: instance
    type: string
    label: ServiceNow Instance
  - id: username
    type: string
    label: ServiceNow Username
  - id: password
    type: string
    label: ServiceNow password
    secret: true
required:
  - instance
  - username
  - password

Then in the Injector configuration:

extra_vars:
  snow_instance: '{{ instance }}'
  snow_password: '{{ password }}'
  snow_username: '{{ username }}'

Now go to Credentials and add a new one, selecting "ServiceNow" as Credential Type:

Thats it! When you link this credential to your host, or playbook, you can use this credentials from within your playbook!

Categories
Windows

Enable ‘Previous Versions’

Anyone who’s ever trashed a spreadsheet, or accidentally deleted a file, will appreciate the 'previous versions' function. However, you will only find out that this is not enabled by default when it is already too late.

You can enable previous versions by enabling shadow copies at a ‘volume’ level, Server Manager> Tools> Computer Management > Share Folders > Configure Shadow Copies > Select the Volume > Enable. It will take about 15% of your space, so make sure you have enough room.

In my case i want a copy each hour, go to Advanced Schedule Options interface, select Repeat task, and then set the frequency to every 1 hours, then Select Time, and then change the time value to 2:58 AM.

Categories
Windows

Enable LLDP on Windows Server 2016/2019

The Link Layer Discovery Protocol (LLDP) is a vendor-neutral link layer protocol used by network devices for advertising their identity, capabilities, and neighbors on a local area network based on IEEE 802 technology, principally wired Ethernet. The protocol is formally referred to by the IEEE as Station and Media Access Control Connectivity Discovery specified in IEEE 802.1AB and IEEE 802.3 section 6 clause 79. More info here

The following will install the DatacenterBridging feature and enable lldp and all interfaces:

Enable-WindowsOptionalFeature -Online -FeatureName 'DataCenterBridging'
Get-NetAdapter | Where-Object { $_.Name -like "*Ethernet*" -and $_.Status -eq 'Up' } | ForEach { Enable-NetLldpAgent -NetAdapterName $_.Name -Verbose }
Categories
Linux

Mysql Clear Diskspace

When you are running out of diskspace you can purge the MySQL binary logs to free up some space

mysql> PURGE BINARY LOGS BEFORE 'yyyy-mm-dd hh:mm:ss';

Sometimes you are already on 99% disk space and need more drastic methods. This requires manually removing the logfiles.

systemctl stop mysql
cd /var/llog/mysql && a=`ls |grep -v relay |grep bin.index` && b=`wc -l <$a` ; c=`echo $(($b/2))` |xargs -l rm ; echo $c | head -n $b $a |cut -d "/" -f2 && sed 1,$c\d $a -i
systemctl start mysql