Getting the source code of Network Security Services (NSS), how to build it, and how to run its test suite.
Getting source code, and a quick overview
The easiest way is to download archives of NSS releases from Mozilla's download server. Find the directory that contains the highest version number. Because NSS depends on the base library NSPR, you should download the archive that combines both NSS and NSPR.
If you are a software developer and intend to contribute enhancements to NSS, you should obtain the latest development snapshot of NSS using mercurial/hg (a distributed source control management tool). In order to get started, anonymous read-only access is sufficient. Create a new directory on your computer that you will use as your local work area, and run the following commands.
hg clone https://hg.mozilla.org/projects/nspr hg clone https://hg.mozilla.org/projects/nss
After the above commands complete, you should have two local directories, named nspr and nss, next to each other.
(Historical information: NSPR and NSS source code have recently been re-organized into a new directory structure. In past versions, all files were located in a directory hierarchy that started with the "mozilla" prefix. The NSPR base library was located in directory mozilla/nsprpub. The subdirectories dbm, security/dbm, security/coreconf, security/nss were part of the NSS sources.)
The nss directory contains the following important subdirectories:
Contains knowledge for cross platform building.
Contains all the library code that is used to create the runtime libraries used by applications.
Contains a set of various tool programs that are built using 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. However, all these tools are good examples of how to write software that makes use of the NSS library.
This directory contains the NSS test suite, which is routinely used to ensure that changes to NSS don't introduce regressions.
Code for NSS unit tests running in Googletest.
It is important to mention the difference between internal NSS code and exported interfaces. Software that would like to use the NSS library must use only the exported interfaces. These can be found by looking at the files with the .def file extension, inside the nss/lib directory hierarchy. Any C function that isn't contained in .def files is strictly for private use within NSS, and applications and test tools are not allowed to call them. For any functions that are listed in the .def files, NSS promises that the binary function interface (ABI) will remain stable.
Once the build is done, you can find the build output below directory dist/?, where ? will be a name dynamically derived from your system's architecture. Exported header files for NSS applications can be found in directory "include", library files in directory "lib", and the tools in directory "bin". In order to run the tools, you should 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 environment variable.
Running the NSS test suite
This is an important part of development work, in order to ensure your changes don't introduce regressions. When adding new features to NSS, tests for the new feature should be added as well.
You must build NSS prior to running the tests. After the build on your computer has succeeded, before you can run the tests on your computer, it might be necessary to set additional environment variables. The NSS tests will start TCP/IP server tools on your computer, and in order for that to work, the NSS test suite needs to know which hostname can be used by client tools to connect to the server tools. On machines that are configured with a hostname that has been registered in your network's DNS, this should work automatically. In other environments (for example in home networks), you could set the HOST and DOMSUF (for domain suffix) environment variables to tell the NSS suite which hostname to use. As a test, it must be possible to successfully use the command "ping $HOST.$DOMSUF" on your computer (ping reports receiving replies). On many computers the variables HOST=localhost DOMSUF=localdomain works. In case you built NSS in 64 bits, you need to set the USE_64 environment variable to 1 to run the tests. If you get name resolution errors, try to disable IPv6 on the loopback device.
After you have set the required environment variables, use "cd nss/tests" and start the tests using "./all.sh". The tests will take a while to complete; on a slow computer it could take a couple of hours.
Once the test suite has completed, a summary will be printed that shows the number of failures. You can find the test suite results in directory nss/../tests_results (i.e. the results directory ends up next to the nss directory, not within it). Each test suite execution will create a new subdirectory; you should clean them up from time to time. Inside the directory you'll find text file output.log, which contains a detailed report of all tests being executed. In order to learn about the details of test failures, search the file for the uppercase test FAILED.
If desired, it's possible to run only subsets of the tests. Read the contents of file all.sh to learn how that works.