Use Only FIPS 140-2 Validated Key Exchange Algorithms
An XCCDF Rule
Description
Limit the key exchange algorithms to those which are FIPS-approved.
Add or modify the following line in /etc/crypto-policies/back-ends/opensshserver.config
CRYPTO_POLICY='-oKexAlgorithms=ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512'This rule ensures that only the key exchange algorithms mentioned above (or their subset) are configured for use, keeping the given order of algorithms.
warning alert: Warning
The system needs to be rebooted for these changes to take effect.
warning alert: Warning
This rule doesn't come with a remediation, automatically changing the crypto-policies may be too disruptive.
warning alert: Regulatory Warning
System crypto modules must be provided by a vendor that undergoes
FIPS-140 certifications.
FIPS-140 is applicable to all Federal agencies that use
cryptographic-based security systems to protect sensitive information
in computer and telecommunication systems (including voice systems) as
defined in Section 5131 of the Information Technology Management Reform
Act of 1996, Public Law 104-106. This standard shall be used in
designing and implementing cryptographic modules that Federal
departments and agencies operate or are operated for them under
contract. See https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.140-2.pdf
To meet this requirements, the system has to have cryptographic software
provided by a vendor that has undergone this certification. This means
providing documentation, test results, design information, and independent
third party review by an accredited lab. While open source software is
capable of meeting this, it does not meet FIPS-140 unless the vendor
submits to this process.
Rationale
DoD information systems are required to use FIPS-approved key exchange algorithms. The system will attempt to use the first algorithm presented by the client that matches the server list. Listing the values "strongest to weakest" is a method to ensure the use of the strongest algorithm available to secure the SSH connection.
- ID
- xccdf_org.ssgproject.content_rule_sshd_use_approved_kex_ordered_stig
- Severity
- Medium
- Updated