{"description": "Limit the Key Exchange to strong algorithms.\nThe following line in <tt>/etc/ssh/sshd_config</tt> demonstrates use\nof those:\n<pre>KexAlgorithms <sub idref=\"sshd_strong_kex\" /></pre>", "rationale": "Key exchange is any method in cryptography by which cryptographic keys are exchanged\nbetween two parties, allowing use of a cryptographic algorithm. If the sender and receiver\nwish to exchange encrypted messages, each must be equipped to encrypt messages to be\nsent and decrypt messages received", "severity": "medium", "references": {"pcidss": ["Req-2.3"], "cis": ["5.1.12"], "pcidss4": ["2.2.7", "2.2"]}, "control_references": {"cis": ["5.1.12"], "pcidss4": ["2.2.7", "2.2"]}, "components": [], "identifiers": {}, "ocil_clause": "KexAlgorithms option is commented out or not using strong hash algorithms", "ocil": "Only strong KEX algorithms should be used. To verify that only strong\nKexAlgorithms are in use, run the following command:\n<pre>$ sudo grep -i kexalgorithms /etc/ssh/sshd_config</pre>\nThe output should contain only those KexAlgorithms which are strong, namely,\n<sub idref=\"sshd_strong_kex\" />", "oval_external_content": null, "fixtext": "", "checktext": "", "vuldiscussion": "", "srg_requirement": "", "warnings": [], "conflicts": [], "requires": [], "policy_specific_content": {}, "platform": null, "platforms": [], "sce_metadata": {}, "inherited_platforms": ["system_with_kernel"], "cpe_platform_names": [], "inherited_cpe_platform_names": ["system_with_kernel"], "bash_conditional": null, "fixes": {}, "title": "Use Only Strong Key Exchange algorithms", "definition_location": "/aptdata/openscap/scap-security-guide/linux_os/guide/services/ssh/ssh_server/sshd_use_strong_kex/rule.yml", "template": null}