Certificatetest

The scope of this page is to be the guide to manage ZNC's certificates. To increase the security check the Hardening page.

ZNC PKI Management

Make sure that the certificate private keys are not encrypted and have not password protection on it. ZNC is unable to properly handle encrypted private key files.

ZNC Certificates

ZNC acts as a proxy for the IRC connections; it places itself between our IRC Client(s) and the IRC Server(s) acting as:

• Server for our IRC Clients (Client <-> ZNC)
• Client for IRC Servers (ZNC <-> Server)

As per the time of writing (August 2021), current ZNC version involves certificates in 3 ways:

• Client <-> ZNC
  • znc.pem: the main and mandatory certificate used by the ZNC to establish all secure connections with IRC and web Client(s).
  • client.pem: the certificates used by the CertAuth module module for the authentication of IRC & web Client(s) with ZNC.

- Certificate stored on local machine and Fingerprint saved in the ZNC

• ZNC <-> Server
  • user.pem: the certificates used by the Cert module for the authentication of ZNC with the IRC Server(s).

- Certificate stored on ZNC machine and Fingerprint saved in the IRC Server account

In the commands below we will talk generally of private key (priv.pem), public key (pub.pem), Certificate Signing Request (csr.pem) and Certificate (cert.pem) without using precise names. Check the page from which you are coming from to understand how to manage the name of generated file.

Note: Be aware that znc.pem is automatically created during configuration process (if SSL is enabled) and it can be overwritten with the command znc --makepem.

znc.pem

ZNC 1.7.0+

Since 1.7, you can configure ZNC to read different parts of the certificate from different files:

SSLCertFile = /path/to/combined/cert.pem
SSLKeyFile = /path/to/private/priv.pem
SSLDHParamFile = /path/to/DH/dhparam.pem

Read Configuration about how to edit config.

The old way (described below) still works.

Before ZNC 1.7

znc.pem must contain everything in order from the "most private" to the "most public" entries, except for the root certificate.

It may be something like this:

cat your-certificate-private-key.pem > znc.pem
cat your-certificate.pem >> znc.pem

# If your certificate has been signed by a CA
## add first the Intermediate certificate (if exists - not signed directly by the Root)
cat intermediate-certificate-of-CA.pem >> znc.pem
## and after add the Root certificate; even if this is redundant. If client doesn't know this CA, it's not trusted anyway.
cat root-certificate-of-CA.pem >> znc.pem

# DH parameters at the end
## If they will not be added, ciphers which relay DH can't be used
cat dhparam.pem >> znc.pem

To apply changes to certificate file to ZNC, just put (replace) it in ZNC's work folder.

Note: As of 1.6.2, ZNC will reload znc.pem each time a client connects, but it'll be fixed in future.

Algorithms

The Public Key Infrastructures (PKI) are based on asymmetric cryptography principles: public & private key.

There are 3 primary algorithms used for PKI key generation:

• (ECC) Elliptic Curve Cryptography

It is the most recently-developed encryption method of the three, but it is going to be more supported. With shorter key lengths, it provides equivalent levels of cryptographic strength as RSA and DSA.

• (RSA) Rivest-Shamir-Adleman

The RSA algorithm was developed in 1977 by Ron Rivest, Adi Shamir, and Leonard Adleman. It is currently the most used and supported key algorithm. Nowadays the key length standard is 2048-4096 bits.

• (DSA) Digital Signature Algorithm

It uses a different algorithm than RSA to create public/private keys but both are considered to be equivalent at same key length. The main differences come down to performance, speed and adoption by the market. Moreover some software are limited to manage DSA up to 1024 bits.

Algorithms Key Size Comparison (bits)
Symmetric	RSA/DSA	ECC
80	1024	160-223
112	2048	224-255
128	3072	256-383
192	7680	384-511
256	15360	512+

Considering the current security standards, we will continue using ECC and RSA.

Key generation

The first step is to create a key pair. As described before, we will provide commands to create ECC or RSA keys.

WARNING: The folllowing commands will not encrypt/password protect the private key cause ZNC is unable to properly handle encrypted private key files. For this reason keep it secret.

Before to proceed, if you want to adopt the ECC, check 2 constraints:
* Your IRC Client/Server supports ECC
* In the case you want certificates signed by a Public CA, be sure it supports ECC
If any of these 2 points will be a NO, then use the RSA.

Regardless of the algorithm you choose, at the end of the process you will have:

• 1 priv.pem
• 1 pub.pem
• 1 priv.info (optional)

ECC

# Generate the ECC private key with 256-bit key length
openssl ecparam -genkey -name prime256v1 -outform PEM -out priv.pem

# Generate the ECC public key
openssl ec -outform PEM -pubout -in priv.pem -out pub.pem

# Get information on the ECC private key
openssl ecparam -noout -text -in priv.pem

# Get sensitive information on the ECC private key
openssl ecparam -noout -text -in priv.pem -param_enc explicit

On the last two commands you can add -out priv.info to get information stored on a file

RSA

# Generate the RSA private key with 4096-bit key length
openssl genrsa -out priv.pem 4096
# Generate the RSA public key
openssl rsa -outform PEM -pubout -in priv.pem -out pub.pem
# Get sensitive information on the RSA private key
openssl rsa -noout -text -in priv.pem

On the last command you can add -out priv.info to get information stored on a file

Certificate Signing Request

The second step is to create a Certificate Signing Request (CSR); to proceed a priv.pem is required (ECC or RSA doesn't matter).

At the end of the process you will have:

• 1 csr.pem

# Generate a CSR based on the private key
openssl req -new -sha512 -key priv.pem -out csr.pem

You will be prompted to fill the fields below:

Country Name (2 letter code)	The two-letter country code where your company is legally located.
State or Province Name (full name)	The state/province where your company is legally located.
Locality Name (e.g., city)	The city where your company is legally located.
Organization Name (e.g., company)	Your company's legally registered name (e.g., YourCompany, Inc.).
Organizational Unit Name (e.g., section)	The name of your department within the organization. (You can leave this option blank; simply press Enter.)
Common Name (e.g., server FQDN)	The fully-qualified domain name (FQDN) (e.g., www.example.com).
Email Address	Your email address. (You can leave this option blank; simply press Enter.)
A challenge password	Leave this option blank (simply press Enter).
An optional company name	Leave this option blank (simply press Enter).

If you want automate the process, you can feed the command providing information with this additional parameter:

-subj "/C=XX/ST=XXXX/L=YYYY/O=ZZZZ/OU=XYZ/CN=FQDN/emailAddress=user [at] domain [dot] com"

If you need the certificate only for the modules Cert or CertAuth you can simply use:

-subj "/CN=YourZncNickname"

or

-subj "/CN=FQDN:Port"

Note: Some user could encounter some issue to login via certificate due to random settings/old caching/etc; try to use your ZNC's FQDN:Port instead of YourZncNickname. Thanks to <CryptoSiD> on Freenode for the tip

Certificate generation

The last step is to generate the X.509 certificate using the CSR previously generated. Now you can:

• submit the CSR to a Public CA
• self signing it

A security overview of the difference between a Self Signed Certificate and a Public CA Signed one, is provided on the Hardening page.

Hint: If you are generating the certificate for:

• Client <-> ZNC
  • znc.pem: you have to decide based on your scenario
  • CertAuth module: you can opt for a Self Signed Certificate, but it could be recognized as untrusted
• ZNC <-> Server
  • Cert module: you can go directly with a simpler/faster/costless Self Signed Certificate

At the end of the process you will have:

• 1 cert.pem
• 1 cert.info (optional)
• 1 bundle.pem (optional - depending on the Public CA)

Signed by Public CA

Signed SSL certificates are recommended when more than one person share the same ZNC instance.

Most of the time they are generated by third-party companies; for this reason you can check the dedicated page Signed_SSL_certificate on the topic.

Note: remember to retrieve the Root and Intermediate certificate of the Public CA you will choose. They could be provided in a single bundle file too.

Self Signed

The strict definition of Self Signed Certificate is:

In cryptography and computer security, a self-signed certificate is a security certificate that is not signed by a certificate authority (CA)
- [Source: Wikipedia]

Extending the mindset, the CA is considered Public, so widely distribuited. In that case even a Private CA Signed certificate can be considered as a Self Signed (signed by our own CA - not Public). To do not go out of the scope of this page, we will not consider the scenario of signing the CSR with a Private CA; moreover, if you have a Private CA, you should be able to sign a CSR by your self.

Regardless you opted out for an ECC or a RSA algorithms, the commands are the same.

# Generate the Certificate, selfsigning the CSR
openssl req -x509 -sha512 -days 3650 -key priv.pem -in csr.pem -out cert.pem
# Store information of the certificate
openssl x509 -fingerprint -sha512 -serial -hash -text -noout -in cert.pem -out cert.info

DHparam

An additional step is to generate the Diffie-Hellman key exchange parameters.

The Diffie-Hellman key exchange WikipediaOpenSSL is a method of securely exchanging cryptographic keys.

It has to be append at the end of the znc.pem.

The dhparam file haven't to be kept secret and can be used multiple times.

Local generation

In the command below, feel free to increase 2048 as you like but be aware that this will take a long time.

# Generate DH parameters
openssl dhparam -out dhparam.pem 2048
# Check DH parameters created
openssl dhparam -noout -text -check -in dhparam.pem

Online generation

If you want to speed up the generation process you can use the services of [2ton]; they offer freshly generated DHparam files.

You can simply download them (wget or curl) choosing the size you want (2048, 3072,4096,8192):

wget https://2ton.com.au/dhparam/2048 -O dhparam.pem
curl https://2ton.com.au/dhparam/2048 -o dhparam.pem

Additional useful commands

PKCS#12

The command below will change the format of the certificate from PEM to PKCS#12.

For example you need this kind of format when you have to interact with browser (Ex. CertAuth module)

openssl pkcs12 -export -in cert.pem -out znc_user.pfx

Fingerprint

Each certificate has its own fingerprint and can be recognized by it. Fingerprints are calculated using HASHes. Allowed hashes are: MD5,SHA1,SHA256,SHA512.

There are many reasons for which we would like to verify the fingerprint of a certificate:

• to setup the Cert module
• to check if a MITM attack is progress
• etc

We could retrieve the fingerprint as from a local certificate as from an online one.

Local certificate

openssl x509 -md5    -noout -fingerprint -in cert.pem | sed -e 's/^.*=//;s/://g;y/ABCDEF/abcdef/'
openssl x509 -sha1   -noout -fingerprint -in cert.pem | sed -e 's/^.*=//;s/://g;y/ABCDEF/abcdef/'
openssl x509 -sha256 -noout -fingerprint -in cert.pem | sed -e 's/^.*=//;s/://g;y/ABCDEF/abcdef/'
openssl x509 -sha512 -noout -fingerprint -in cert.pem | sed -e 's/^.*=//;s/://g;y/ABCDEF/abcdef/'

If you need the fingerprint in the default format, remove | sed -e 's/^.*=//;s/://g;y/ABCDEF/abcdef/'

Note: If you are here from the Cert module, be aware that different IRC networks use different fingerprints; for example Libera.chat uses SHA-512. Consult the network you're connecting to for this information.

Online certificate

# Replace with the hostname/FQDN of your ZNC Server
sslhost=znc.example.com
# Replace with the SSL port of your ZNC Server
sslport=6697

sslcert=$(openssl s_client -showcerts -connect "$sslhost":"$sslport" < /dev/null)
echo "$sslcert" | openssl x509 -noout -fingerprint -md5
echo "$sslcert" | openssl x509 -noout -fingerprint -sha1
echo "$sslcert" | openssl x509 -noout -fingerprint -sha256
echo "$sslcert" | openssl x509 -noout -fingerprint -sha512

Glossary

• CA: Certificate Authority or Certification Authority is the entity that issues digital (X.509) certificates
• Certificate: Also known as X.509 certificate, it is used to encrypt and decrypt data relaying on a related public and private key pair.
• CSR: Certificate Signing Request
• DER: Distinguished Encoding Rules is a binary encoding for X.509 certificates and private keys
• DES: Data Encryption Standard is a symmetric-key algorithm for the encryption of digital data. Too insecure for encryption nowadays.
• DSA: Digital Signature Algorithm
• ECC: Elliptic Curve Cryptography algorithms
• FQDN: Fully Qualified Domain Name or Hostname
• MITM: Man-In-The-Middle attack; an attacker acts as proxy sniffing and/or altering the traffic data
• P12: Common file extension for PKCS#12 format
• PEM: Privacy Enhanced Mail is a Base64 encoded ASCII file format
• PFX: Common file extension for PKCS#12 format
• PKCS12: Common file extension for PKCS#12 format
• PKCS#12: Binary format for storing certificate chain and private key in a single: encryptable file
• PKI: Public Key Infrastructures
• Private Key: One of the key pair. It is the one that must be kept secret
• Public Key: One of the key pair. It is the one that can be freely shared
• RSA: Rivest-Shamir-Adleman algorithms
• SSL: Secure Sockets Layer is a cryptographic protocol designed to provide communications security over a computer network