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Network Security Services

Network Security Services (NSS) is a set of libraries designed to support cross-platform development of security-enabled client and server applications. NSS supports TLS 1.2, TLS 1.3, PKCS #5, PKCS#7, PKCS #11, PKCS #12, S/MIME, X.509 v3 certificates, and other security standards.

Getting started

In order to get started create a new directory on that you will be uses as your local work area, and check out NSS and NSPR. (Note that there's no git mirror of NSPR and you require mercurial to get the latest NSPR source.)

git clone
hg clone

NSS can also be cloned with mercurial

hg clone

Building NSS

This build system is under development. It does not yet support all the features or platforms that NSS supports. To build on anything other than Mac or Linux please use the legacy build system as described below.

Build requirements:

After changing into the NSS directory a typical build is done as follows


Once the build is done the build output is found in the directory ../dist/Debug for debug builds and ../dist/Release for opt builds. Exported header files can be found in the include directory, library files in directory lib, and tools in directory bin. In order to run the tools, set your system environment to use the libraries of your build from the "lib" directory, e.g., using the LD_LIBRARY_PATH or DYLD_LIBRARY_PATH.

See help.txt for more information on using

Building NSS (legacy build system)

After changing into the NSS directory a typical build of 32-bit NSS is done as follows:

make nss_build_all

The following environment variables might be useful:

  • BUILD_OPT=1 to get an optimised build

  • USE_64=1 to get a 64-bit build (recommended)

The complete list of environment variables can be found here.

To clean the build directory run:

make nss_clean_all



Make sure that the address $HOST.$DOMSUF on your computer is available. This is necessary because NSS tests generate certificates and establish TLS connections, which requires a fully qualified domain name. You can test this by calling ping $HOST.$DOMSUF. If this is working, you're all set. If it's not, set or export:


Note that you might have to add nss.local to /etc/hosts if it's not there. The entry should look something like nss.local nss.

Running tests

Runnning all tests will take a while!

cd tests

Make sure that all environment variables set for the build are set while running the tests as well. Test results are published in the folder ../../test_results/.

Individual tests can be run with the NSS_TESTS environment variable, e.g. NSS_TESTS=ssl_gtests ./ or by changing into the according directory and running the bash script there cd ssl_gtests && ./ The following tests are available:

cipher lowhash libpkix cert dbtests tools fips sdr crmf smime ssl ocsp merge pkits chains ec gtests ssl_gtests bogo policy

To make tests run faster it's recommended to set NSS_CYCLES=standard to run only the standard cycle.


NSS releases can be found at Mozilla's download server. Because NSS depends on the base library NSPR you should download the archive that combines both NSS and NSPR.


Bugzilla is used to track NSS development and bugs. File new bugs in the NSS product.

A list with good first bugs to start with are listed here.

NSS Folder Structure

The nss directory contains the following important subdirectories:

  • coreconf contains the build logic.

  • lib contains all library code that is used to create the runtime libraries.

  • cmd contains a set of various tool programs that are built with NSS. Several tools are general purpose and can be used to inspect and manipulate the storage files that software using the NSS library creates and modifies. Other tools are only used for testing purposes.

  • test and gtests contain the NSS test suite. While test contains shell scripts to drive test programs in cmd, gtests holds a set of gtests.

A more comprehensible overview of the NSS folder structure and API guidelines can be found here.

Build mechanisms related to FIPS compliance

NSS supports build configurations for FIPS-140 compliance, and alternative build configurations that disable functionality specific to FIPS-140 compliance.

This section documents the environment variables and build parameters that control these configurations.

Build FIPS startup tests

The C macro NSS_NO_INIT_SUPPORT controls the FIPS startup self tests. If NSS_NO_INIT_SUPPORT is defined, the startup tests are disabled.

The legacy build system (make) by default disables these tests. To enable these tests, set environment variable NSS_FORCE_FIPS=1 at build time.

The gyp build system by default disables these tests. To enable these tests, pass parameter --enable-fips to

Building either FIPS compliant or alternative compliant code

The C macro NSS_FIPS_DISABLED can be used to disable some FIPS compliant code and enable alternative implementations.

The legacy build system (make) never defines NSS_FIPS_DISABLED and always uses the FIPS compliant code.

The gyp build system by default defines NSS_FIPS_DISABLED. To use the FIPS compliant code, pass parameter --enable-fips to

Test execution

The NSS test suite may contain tests that are included, excluded, or are different based on the FIPS build configuration. To execute the correct tests, it's necessary to determine which build configuration was used.

The legacy build system (make) uses environment variables to control all aspects of the build configuration, including FIPS build configuration.

Because the gyp build system doesn't use environment variables to control the build configuration, the NSS tests cannot rely on environment variables to determine the build configuration.

A helper binary named nss-build-flags is produced as part of the NSS build, which prints the C macro symbols that were defined at build time, and which are relevant to test execution.