Certificates Stored in File

To configure the server to allow user authentication with certificates, perform the following tasks:

  1. Acquire the CA certificate and copy it to the server machine. You can either copy the X.509 certificate(s) as such or you can copy a PKCS #7 package including the CA certificate(s). Certificates can be extracted from a PKCS #7 package by specifying the -7 flag with ssh-keygen-g3.

  2. Certificate authentication is a part of the publickey authentication method. Make sure that you have enabled it in the /opt/tectia/etc/sshd2_config file:

    AllowedAuthentications        publickey
    AuthPublicKey.Cert.Required   no 

    Setting the AuthPublicKey.Cert.Required option to yes defines that the user must authenticate with a certificate or else the authentication will fail.

  3. Specify the trusted CA certificate and the mapping file(s) in the ssh_certd_config file:

    Pki                     <ca-cert-path>
    MapFile                  <map-file-path>

    You can define several CA certificates by using several Pki keywords.

    Pki                     test-ca1.crt
    MapFile                  cert-user-mapping1.txt
    Pki                      test-ca2.crt
    MapFile                  cert-user-mapping2a.txt
    MapFile                  cert-user-mapping2b.txt

    Note that multiple MapFile keywords are permitted per Pki keyword. Also, if no mapping file is defined, all connections are denied even if user certificates can be verified using the defined CA certificate. The server will accept only certificates issued by defined CA(s).

  4. Also define the LDAP server(s) used for CRL checks in the ssh_certd_config file. If the CA services (OCSP, CRLs) are located behind a firewall, define also the SOCKS server.

    LdapServers             ldap://ldap.example.com:389
    SocksServer              socks://fw.example.com:1080

    Defining the LDAP server is not necessary if the CA certificate contains a CRL Distribution Point or an Authority Info Access extension.

  5. Create the certificate user mapping file as described in Certificate User Mapping File.

  6. Restart ssh-certd as instructed in Restarting and Stopping ssh-certd.

For more information on the configuration file options, see sshd2_config and ssh_certd_config.