Chapter 2. Installing the system in FIPS mode (2024)

The Federal Information Processing Standards (FIPS) Publication 140 is a series of computer security standards developed by the National Institute of Standards and Technology (NIST) to ensure the quality of cryptographic modules. The FIPS 140 standard ensures that cryptographic tools implement their algorithms correctly. Runtime cryptographic algorithm and integrity self-tests are some of the mechanisms to ensure a system uses cryptography that meets the requirements of the standard.

To ensure that your RHEL system generates and uses all cryptographic keys only with FIPS-approved algorithms, you must switch RHEL to FIPS mode.

You can enable FIPS mode by using one of the following methods:

If you aim for FIPS compliance, start the installation in FIPS mode. This avoids cryptographic key material regeneration and reevaluation of the compliance of the resulting system associated with converting already deployed systems.

To operate a FIPS-compliant system, create all cryptographic key material in FIPS mode. Furthermore, the cryptographic key material must never leave the FIPS environment unless it is securely wrapped and never unwrapped in non-FIPS environments.

Switching the system to FIPS mode by using the fips-mode-setup tool does not guarantee compliance with the FIPS 140 standard. Re-generating all cryptographic keys after setting the system to FIPS mode may not be possible. For example, in the case of an existing IdM realm with users' cryptographic keys you cannot re-generate all the keys. If you cannot start the installation in FIPS mode, always enable FIPS mode as the first step after the installation, before you make any post-installation configuration steps or install any workloads.

The fips-mode-setup tool also uses the FIPS system-wide cryptographic policy internally. But on top of what the update-crypto-policies --set FIPS command does, fips-mode-setup ensures the installation of the FIPS dracut module by using the fips-finish-install tool, it also adds the fips=1 boot option to the kernel command line and regenerates the initial RAM disk.

Furthermore, enforcement of restrictions required in FIPS mode depends on the contents of the /proc/sys/crypto/fips_enabled file. If the file contains 1, RHEL core cryptographic components switch to mode, in which they use only FIPS-approved implementations of cryptographic algorithms. If /proc/sys/crypto/fips_enabled contains 0, the cryptographic components do not enable their FIPS mode.

The FIPS system-wide cryptographic policy helps to configure higher-level restrictions. Therefore, communication protocols supporting cryptographic agility do not announce ciphers that the system refuses when selected. For example, the ChaCha20 algorithm is not FIPS-approved, and the FIPS cryptographic policy ensures that TLS servers and clients do not announce the TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256 TLS cipher suite, because any attempt to use such a cipher fails.

If you operate RHEL in FIPS mode and use an application providing its own FIPS-mode-related configuration options, ignore these options and the corresponding application guidance. The system running in FIPS mode and the system-wide cryptographic policies enforce only FIPS-compliant cryptography. For example, the Node.js configuration option --enable-fips is ignored if the system runs in FIPS mode. If you use the --enable-fips option on a system not running in FIPS mode, you do not meet the FIPS-140 compliance requirements.

To enable the cryptographic module self-checks mandated by the Federal Information Processing Standard (FIPS) 140, enable FIPS mode during the system installation.