Network Security Services

From ArchWiki

Network Security Services (NSS) is a set of libraries designed to support cross-platform development of security-enabled client and server applications.

Applications built with NSS can support SSL v2 and v3, TLS, PKCS #5, PKCS #7, PKCS #11, PKCS #12, S/MIME, X.509 v3 certificates, and other security standards.

NSS is required by many packages, including, for example, Chromium and Firefox.


Install the nss package.


NSS is implemented in terms of operations on a dynamically configured list of PKCS #11 modules. Each module can execute cryptographic operations and store cryptographic objects. The configured list of modules is usually stored in an arbitrary directory, provided by a user at initialization of NSS, in the file pkcs11.txt. The list always contains a built-in module "NSS Internal PKCS #11 Module" with tokens "NSS Generic Crypto Services" and "NSS Certificate DB". The first token provides cryptographic mechanisms such as RSA, SHA256, TLS etc. The second token stores certificates and private keys in the same user-provided directory in the files cert9.db and key4.db. The files pkcs11.txt, cert9.db and key4.db are also called "NSS databases". Paths to NSS databases for some applications are listed in the table below. You should provide some path for each operation. Examples below will use ~/.pki/nssdb/.

Application Path to NSS databases
chromium, evolution ~/.pki/nssdb/
firefox ~/.mozilla/firefox/<profile>/
thunderbird ~/.thunderbird/<profile>/
libreoffice-fresh configurable via Options [1]

For managing PKCS #11 modules NSS provides the modutil(1) utility, for managing certificates and private keys — the certutil(1) utility.

Note: NSS can automatically add /usr/lib/ to the list of PKCS #11 modules depending on initialization flags.

List certificate DB

To get list of all certificates:

$ certutil -d ~/.pki/nssdb/ -L

To get details about certificate:

$ certutil -d ~/.pki/nssdb/ -L -n certificate_nickname

Generate an RSA private key

$ certutil -d ~/.pki/nssdb/ -G -g keysize -n nickname

Generate a certificate signing request

$ certutil -d ~/.pki/nssdb/ -R -k key-id -s subject -o file

Generate a self-signed certificate

$ certutil -d ~/.pki/nssdb/ -S -s subject -n nickname -x -t C,C,C -o file

Import certificate

To add a certificate specify the -A option:

$ certutil -d ~/.pki/nssdb/ -A -t "TRUSTARGS" -n certificate_nickname -i /path/to/cert/filename

The TRUSTARGS are three strings of zero or more alphabetic characters, separated by commas, for example: "TCu,Cu,Tuw". They define how the certificate should be trusted for SSL, email, and object signing, and are explained in the certutil documentation[dead link 2023-05-06 ⓘ] or Meena's blog post on trust flags.

To add a personal certificate and private key for SSL client authentication use the command:

$ pk12util -d ~/.pki/nssdb/ -i /path/to/PKCS12/cert/filename.p12

This will import a personal certificate and private key stored in a PKCS #12 file. The TRUSTARGS of the personal certificate will be set to "u,u,u".

Edit certificate

Call certutil with -M option to edit the certificate. For example, to edit the TRUSTARGS:

$ certutil -d ~/.pki/nssdb/ -M -t "TRUSTARGS" -n certificate_nickname

Delete certificate

Use -D option to remove the certificate:

$ certutil -d ~/.pki/nssdb/ -D -n certificate_nickname

Adding a trusted CA certificate

A system-wide trust store /usr/lib/pkcs11/ is usually automatically added to the list of PKCS #11 modules. See Transport Layer Security#Trust management for system-wide configuration. For application-specific configuration use such a command to add a CA certificate:

certutil -d ~/.pki/nssdb/ -A -i /path/to/certificate -n certificate nickname -t C,,

See also