Description: An SSH public key is one of two files used in SSH public key authentication. In this authentication method, a public key is a key that can be used for verifying digital signatures generated using a corresponding private key. Only a public key that corresponds to a private key will be able to authenticate successfully. Rationale: If a public host key file is modified by an unauthorized user, the SSH service may be compromised Audit: Run the following command and verify Access does not grant write or execute permissions to group or other for all returned files # find /etc/ssh -xdev -type f -name 'ssh_host_*_key.pub' -exec stat {} ; File: /etc/ssh/ssh_host_rsa_key.pub Size: 382 Blocks: 8 IO Block: 4096 regular file Device: ca01h/51713d Inode: 8631758 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2018-10-22 18:24:56.861750616 +0000 Modify: 2018-10-22 18:24:56.861750616 +0000 Change: 2018-10-22 18:24:56.881750616 +0000 Birth: - File: /etc/ssh/ssh_host_ecdsa_key.pub Size: 162 Blocks: 8 IO Block: 4096 regular file Device: ca01h/51713d Inode: 8631761 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2018-10-22 18:24:56.897750616 +0000 Modify: 2018-10-22 18:24:56.897750616 +0000 Change: 2018-10-22 18:24:56.917750616 +0000 Birth: - File: /etc/ssh/ssh_host_ed25519_key.pub Size: 82 Blocks: 8 IO Block: 4096 regular file Device: ca01h/51713d Inode: 8631763 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2018-10-22 18:24:56.945750616 +0000 Modify: 2018-10-22 18:24:56.945750616 +0000 Change: 2018-10-22 18:24:56.961750616 +0000 Birth: - Remediation: Run the following commands to set permissions and ownership on the SSH host public key files # find /etc/ssh -xdev -type f -name 'ssh_host_*_key.pub' -exec chmod 0644 {} ; #find /etc/ssh -xdev -type f -name 'ssh_host_*_key.pub' -exec chown root:root {} ;

[110100100, root, root]

Run the following commands to set permissions and ownership on the SSH host public key files # find /etc/ssh -xdev -type f -name 'ssh_host_*_key.pub' -exec chmod 0644 {} ; #find /etc/ssh -xdev -type f -name 'ssh_host_*_key.pub' -exec chown root:root {} ;