/proc/sys/crypto/

These files show up in /proc/sys/crypto/, depending on the kernel configuration:

af_alg_restrict

Controls the level of restriction of AF_ALG.

AF_ALG is a deprecated and rarely-used userspace interface that is a frequent source of vulnerabilities. It also unnecessarily exposes a large number of kernel implementation details. For more information about AF_ALG, see Documentation/crypto/userspace-if.rst.

Starting in Linux v7.3, AF_ALG supports only a limited set of algorithms by default. This sysctl allows the system administrator to remove this restriction when needed for compatibility reasons, or to go further and disable AF_ALG entirely. The default value is 1.

0

AF_ALG is unrestricted.

1

AF_ALG is supported with a limited list of algorithms. The list is designed for compatibility with known users such as iwd and bluez that haven’t yet been fixed to use userspace crypto code.

Specifically, there is an allowlist for unprivileged processes and a somewhat longer allowlist for processes that hold CAP_SYS_ADMIN or CAP_NET_ADMIN in the initial user namespace.

Attempts to bind() an AF_ALG socket with a disallowed algorithm fail with ENOENT.

2

AF_ALG is completely disabled. Attempts to create an AF_ALG socket fail with EAFNOSUPPORT.

fips_enabled

Read-only flag that indicates whether FIPS mode is enabled.

  • 0: FIPS mode is disabled (default).

  • 1: FIPS mode is enabled.

This value is set at boot time via the fips=1 kernel command line parameter. When enabled, the cryptographic API will restrict the use of certain algorithms and perform self-tests to ensure compliance with FIPS (Federal Information Processing Standards) requirements, such as FIPS 140-2 and the newer FIPS 140-3, depending on the kernel configuration and the module in use.

fips_name

Read-only file that contains the name of the FIPS module currently in use. The value is typically configured via the CONFIG_CRYPTO_FIPS_NAME kernel configuration option.

fips_version

Read-only file that contains the version string of the FIPS module. If CONFIG_CRYPTO_FIPS_CUSTOM_VERSION is set, it uses the value from CONFIG_CRYPTO_FIPS_VERSION. Otherwise, it defaults to the kernel release version (UTS_RELEASE).

Copyright (c) 2026, Shubham Chakraborty <chakrabortyshubham66@gmail.com>

For general info and legal blurb, please look in Documentation for /proc/sys.