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crypto-policies(7)

==================

:doctype: manpage

:man source: crypto-policies

NAME

----

crypto-policies - system-wide crypto policies overview

DESCRIPTION

-----------

The security of cryptographic components of the operating system

does not remain constant over time. Algorithms, such as

cryptographic hashing and encryption, typically have a lifetime,

after which they are considered either too risky to use or plain insecure.

That means, we need to phase out such algorithms from the default

settings or completely disable them if they could cause an irreparable problem.

While in the past the algorithms were not disabled in a consistent way

and different applications applied different policies, the system-wide

crypto-policies followed by the crypto core components allow consistently

deprecating and disabling algorithms system-wide.

The individual policy levels (*DEFAULT*, *LEGACY*, *FUTURE*, and *FIPS*)

are included in the *crypto-policies(7)* package. In the future, there will

be also a mechanism for easy creation and deployment of policies defined

by the system administrator or a third party vendor.

For rationale, see *RFC 7457* for a list of attacks taking advantage of

legacy crypto algorithms.

COVERED APPLICATIONS

--------------------

Crypto-policies apply to the configuration of the core cryptographic subsystems,

covering *TLS*, *IKE*, *IPSec*, *DNSSec*, and *Kerberos* protocols; i.e., the

supported secure communications protocols on the base operating system.

Once an application runs in the operating system, it follows the default

or selected policy and refuses to fall back to algorithms and protocols not

within the policy, unless the user has explicitly requested the application

to do so. That is, the policy applies to the default behavior of applications

when running with the system-provided configuration but the user can override

it on an application-specific basis.

The policies currently provide settings for these applications and libraries:

* *BIND* DNS name server daemon

* *GnuTLS* TLS library

* *OpenJDK* runtime environment

* *Kerberos 5* library

* *Libreswan* IPsec and IKE protocol implementation

* *NSS* TLS library

* *OpenSSH* SSH2 protocol implementation

* *OpenSSL* TLS library

Applications using the above libraries and tools are covered by the

cryptographic policies unless they are explicitly configured not to be so.

PROVIDED POLICY LEVELS

----------------------

*LEGACY*::

  This policy ensures maximum compatibility with legacy systems; it is

  less secure and it includes support for *TLS 1.0*, *TLS 1.1*, and *SSH2*

  protocols or later. The algorithms *DSA*, *3DES*, and *RC4* are allowed,

  while *RSA* and *Diffie-Hellman* parameters are accepted if larger than 1023 bits.

  The level provides at least 64-bit security.

  * MACs: all *HMAC* with *SHA-1* or better + all modern MACs (*Poly1305*

    etc.)

  * Curves: all prime >= 255 bits (including Bernstein curves)

  * Signature algorithms: with *SHA1* hash or better (*DSA* allowed)

  * *TLS* Ciphers: all available >= 112-bit key, >= 128-bit block (including

    *RC4* and *3DES*)

  * Non-TLS Ciphers: same as *TLS* ciphers with added *Camellia*

  * Key exchange: *ECDHE*, *RSA*, *DHE*

  * *DH* params size: >= 1023

  * *RSA* keys size: >= 1023

  * *DSA* params size: >= 1023

  * *TLS* protocols: *TLS* >= 1.0, *DTLS* >= 1.0

*DEFAULT*::

  The *DEFAULT* policy is a reasonable default policy for today's standards,

  compatible with *PCI-DSS* requirements. It allows the *TLS 1.2* and

  *TLS 1.3* protocols, as well as *IKEv2* and *SSH2*. The *RSA* and

  *Diffie-Hellman* parameters are accepted if larger than 2047 bits.

  The level provides at least 112-bit security with the exception of *SHA-1*

  signatures needed for *DNSSec* and other still prevalent legacy use of

  *SHA-1* signatures.

  * MACs: all *HMAC* with *SHA-1* or better + all modern MACs (*Poly1305*

    etc.)

  * Curves: all prime >= 255 bits (including Bernstein curves)

  * Signature algorithms: with *SHA-1* hash or better (no *DSA*)

  * *TLS* Ciphers: >= 128-bit key, >= 128-bit block (*AES*, *ChaCha20*,

    including *AES-CBC*)

  * non-TLS Ciphers: as *TLS* Ciphers with added *Camellia*

  * key exchange: *ECDHE*, *RSA*, *DHE* (no *DHE-DSS*)

  * *DH* params size: >= 2048

  * *RSA* keys size: >= 2048

  * *TLS* protocols: *TLS* >= 1.2, *DTLS* >= 1.2

*FUTURE*::

  A conservative security level that is believed to withstand any near-term

  future attacks. This level does not allow the use of *SHA-1* in signature

  algorithms. The level also provides some (not complete) preparation for

  post-quantum encryption support in form of 256-bit symmetric encryption

  requirement. The *RSA* and *Diffie-Hellman* parameters are accepted if

  larger than 3071 bits. The level provides at least 128-bit security.

  * MACs: all *HMAC* with *SHA-256* or better + all modern MACs (*Poly1305*

    etc.)

  * Curves: all prime >= 255 bits (including Bernstein curves)

  * Signature algorithms: with *SHA-256* hash or better (no *DSA*)

  * *TLS* Ciphers: >= 256-bit key, >= 128-bit block, only Authenticated

    Encryption (AE) ciphers

  * non-TLS Ciphers: same as *TLS* ciphers with added non AE ciphers and

    *Camellia*

  * key exchange: *ECDHE*, *DHE* (no *DHE-DSS*, no *RSA*)

  * *DH* params size: >= 3072

  * *RSA* keys size: >= 3072

  * *TLS* protocols: *TLS* >= 1.2, *DTLS* >= 1.2

*FIPS*::

  A level that conforms to the *FIPS 140-2* requirements. This policy is used

  internally by the *fips-mode-setup(8)* tool which can switch the system

  into the *FIPS 140-2* compliance mode.

  The level provides at least 112-bit security.

  * MACs: all *HMAC* with *SHA1* or better

  * Curves: all prime >= 256 bits

  * Signature algorithms: with *SHA-256* hash or better (no *DSA*)

  * *TLS* Ciphers: >= 128-bit key, >= 128-bit block (*AES*,

    including *AES-CBC*)

  * non-TLS Ciphers: same as *TLS* Ciphers

  * key exchange: *ECDHE*, *DHE* (no *DHE-DSS*, no *RSA*)

  * *DH* params size: >= 2048

  * *RSA* params size: >= 2048

  * *TLS* protocols: *TLS* >= 1.2, *DTLS* >= 1.2

*EMPTY*::

  All cryptographic algorithms are disabled (used for debugging only, do not

  use).

COMMANDS

--------

*update-crypto-policies(8)*::

  This command manages the policies available to the various cryptographic

  back ends and allows the system administrator to change the active

  cryptographic policy level.

*fips-mode-setup(8)*::

  This command allows the system administrator to enable, or disable the

  system FIPS mode and also apply the *FIPS* cryptographic policy level

  which limits the allowed algorithms and protocols to these allowed by

  the FIPS 140-2 requirements.

NOTES

-----

*Exceptions:*

* *Go-language* applications do not yet follow the system-wide policy.

* *Libssh* applications do not yet follow the system-wide policy.

* *GnuPG-2* application does not follow the system-wide policy.

In general only the data-in-transit is currently covered by the system-wide

policy.

If the system administrator changes the system-wide policy level with

the *update-crypto-policies(8)* command it is advisable to restart the

system as the individual back-end libraries read the configuration files

usually during their initialization. The changes in the policy level

thus take place in most cases only when the applications using the back-end

libraries are restarted.

*Removed cipher suites and protocols*

The following cipher suites and protocols are completely removed from the

core cryptographic libraries listed above:

* *DES*

* All export grade cipher suites

* *MD5* in signatures

* *SSLv2*

* *SSLv3*

* All *ECC* curves smaller than 224 bits

* All binary field *ECC* curves

*Cipher suites and protocols disabled in all policy levels*

The following ciphersuites and protocols are available but disabled in all

crypto policy levels. They can be enabled only by explicit configuration

of individual applications:

* *DH* with parameters < 1024 bits

* *RSA* with key size < 1024 bits

* *Camellia*

* *ARIA*

* *SEED*

* *IDEA*

* Integrity only ciphersuites

* *TLS* *CBC mode* ciphersuites using *SHA-384* HMAC

* *AES-CCM8*

* all *ECC* curves incompatible with *TLS 1.3*, including secp256k1

* *IKEv1*

FILES

-----

/etc/crypto-policies/back-ends::

	The individual cryptographical back-end configuration files.

	Usually linked to the configuration shipped in the crypto-policies

	package unless a configuration from *local.d* is added.

/etc/crypto-policies/config::

	The active crypto-policies level set on the system.

/etc/crypto-policies/local.d::

	Additional configuration shipped by other packages or created by

	the system administrator. The contents of the *<back-end>-file.config*

	is appended to the configuration from the policy back end as

	shipped in the crypto-policies package.

SEE ALSO

--------

update-crypto-policies(8), fips-mode-setup(8)

AUTHOR

------

Written by Tomáš Mráz.