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  1. @hsteiger hsteiger created this gist Oct 22, 2019.
    158 changes: 158 additions & 0 deletions STARTTLS with Let's Encrypt and PowerMTA
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    STARTTLS with Let's Encrypt and PowerMTA
    This is an update to my previous post. I tried using the same certificate to let PowerMTA secure our e-mail server using STARTTLS, but unfortunately, Let's Encrypt is still untrusted by our PHP front-end because Let's Encrypt is still a new certificate authority. The solution is to include IdentTrust's root certificate as it's already trusted by all clients.

    This setup is specific to a server with Apache and PowerMTA. You can probably make this work without a web server. Simply adjust the paths and other things as necessary.

    I'm pasting the previous steps in this post with some updates.

    First, log in as root. It's supposed to be a bad practice to work directly on root, but what the heck:

    # sudo su -

    Then, download GetSSL to your box:

    # mkdir -p /root/getssl /etc/letsencrypt

    # cd /root/getssl

    # curl -s https://raw.githubusercontent.com/srvrco/getssl/master/getssl > getssl

    # chmod 700 getssl

    Then, generate the default config files:

    # ./getssl -c example.org
    Making domain directory - /root/.getssl/example.org
    creating domain config file in /root/.getssl/example.org/getssl.cfg

    Edit the global config at: ~/.getssl/getssl.cfg. Pay particular attention to the followine line:
    RELOAD_CMD="service httpd reload"

    Depending on your system, it can be "service apache2 reload" or something similar. Update as necessary.

    Uncomment the following line also:
    CA="https://acme-v01.api.letsencrypt.org"

    WARNING: The server has a limit of 5 certificates per 7 days, so use the staging server when experimenting. I hit the limit when writing this post. Lolz.

    Edit the domain config at ~/.getssl/example.org/getssl.cfg and insert the following lines:

    SANS=www.example.org
    DOMAIN_KEY_CERT_LOCATION=/etc/letsencrypt/example.org.crt
    SERVER_TYPE="https"
    CHECK_REMOTE="true"
    ACL=('/var/www/pub/.well-known/acme-challenge')
    USE_SINGLE_ACL="true"

    Adjust the paths as necessary.

    The ACL variable above is the path for the Automatic Certificate Management Environment (ACME) challenge. It should point to a folder inside your web server's document root and should be accessible to the public via HTTP. The ACME challenge is used to prove that you control the web server.

    Next, edit the Apache config and insert this in your SSL section:

    Header always set Strict-Transport-Security "max-age=15768000"
    SSLProtocol all -SSLv2 -SSLv3
    SSLCipherSuite ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:ECDHE-ECDSA-DES-CBC3-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-CBC3-SHA:!DSS
    SSLHonorCipherOrder on
    SSLCertificateFile /etc/letsencrypt/example.org.crt
    SSLCertificateChainFile /etc/letsencrypt/le.crt

    Manually download Let's Encrypt's certificate:

    # curl -s https://letsencrypt.org/certs/lets-encrypt-x3-cross-signed.pem > /etc/letsencrypt/le.crt

    Next, we need to merge IdenTrust's root certificate with Let's Encrypt's. Open your browser and go to: https://www.identrust.com/certificates/trustid/root-download-x3.html

    Then, edit /etc/letsencrypt/le.crt and paste IdenTrust's cert at the bottom of the cert. le.crt should look like:

    -----BEGIN CERTIFICATE-----
    MIIEkjCCA3qgAwIBAgIQCgFBQgAAAVOFc2oLheynCDANBgkqhkiG9w0BAQsFADA/
    MSQwIgYDVQQKExtEaWdpdGFsIFNpZ25hdHVyZSBUcnVzdCBDby4xFzAVBgNVBAMT
    DkRTVCBSb290IENBIFgzMB4XDTE2MDMxNzE2NDA0NloXDTIxMDMxNzE2NDA0Nlow
    SjELMAkGA1UEBhMCVVMxFjAUBgNVBAoTDUxldCdzIEVuY3J5cHQxIzAhBgNVBAMT
    GkxldCdzIEVuY3J5cHQgQXV0aG9yaXR5IFgzMIIBIjANBgkqhkiG9w0BAQEFAAOC
    AQ8AMIIBCgKCAQEAnNMM8FrlLke3cl03g7NoYzDq1zUmGSXhvb418XCSL7e4S0EF
    q6meNQhY7LEqxGiHC6PjdeTm86dicbp5gWAf15Gan/PQeGdxyGkOlZHP/uaZ6WA8
    SMx+yk13EiSdRxta67nsHjcAHJyse6cF6s5K671B5TaYucv9bTyWaN8jKkKQDIZ0
    Z8h/pZq4UmEUEz9l6YKHy9v6Dlb2honzhT+Xhq+w3Brvaw2VFn3EK6BlspkENnWA
    a6xK8xuQSXgvopZPKiAlKQTGdMDQMc2PMTiVFrqoM7hD8bEfwzB/onkxEz0tNvjj
    /PIzark5McWvxI0NHWQWM6r6hCm21AvA2H3DkwIDAQABo4IBfTCCAXkwEgYDVR0T
    AQH/BAgwBgEB/wIBADAOBgNVHQ8BAf8EBAMCAYYwfwYIKwYBBQUHAQEEczBxMDIG
    CCsGAQUFBzABhiZodHRwOi8vaXNyZy50cnVzdGlkLm9jc3AuaWRlbnRydXN0LmNv
    bTA7BggrBgEFBQcwAoYvaHR0cDovL2FwcHMuaWRlbnRydXN0LmNvbS9yb290cy9k
    c3Ryb290Y2F4My5wN2MwHwYDVR0jBBgwFoAUxKexpHsscfrb4UuQdf/EFWCFiRAw
    VAYDVR0gBE0wSzAIBgZngQwBAgEwPwYLKwYBBAGC3xMBAQEwMDAuBggrBgEFBQcC
    ARYiaHR0cDovL2Nwcy5yb290LXgxLmxldHNlbmNyeXB0Lm9yZzA8BgNVHR8ENTAz
    MDGgL6AthitodHRwOi8vY3JsLmlkZW50cnVzdC5jb20vRFNUUk9PVENBWDNDUkwu
    Y3JsMB0GA1UdDgQWBBSoSmpjBH3duubRObemRWXv86jsoTANBgkqhkiG9w0BAQsF
    AAOCAQEA3TPXEfNjWDjdGBX7CVW+dla5cEilaUcne8IkCJLxWh9KEik3JHRRHGJo
    uM2VcGfl96S8TihRzZvoroed6ti6WqEBmtzw3Wodatg+VyOeph4EYpr/1wXKtx8/
    wApIvJSwtmVi4MFU5aMqrSDE6ea73Mj2tcMyo5jMd6jmeWUHK8so/joWUoHOUgwu
    X4Po1QYz+3dszkDqMp4fklxBwXRsW10KXzPMTZ+sOPAveyxindmjkW8lGy+QsRlG
    PfZ+G6Z6h7mjem0Y+iWlkYcV4PIWL1iwBi8saCbGS5jN2p8M+X+Q7UNKEkROb3N6
    KOqkqm57TH2H3eDJAkSnh6/DNFu0Qg==
    -----END CERTIFICATE-----
    -----BEGIN CERTIFICATE-----
    MIIDSjCCAjKgAwIBAgIQRK+wgNajJ7qJMDmGLvhAazANBgkqhkiG9w0BAQUFADA/
    MSQwIgYDVQQKExtEaWdpdGFsIFNpZ25hdHVyZSBUcnVzdCBDby4xFzAVBgNVBAMT
    DkRTVCBSb290IENBIFgzMB4XDTAwMDkzMDIxMTIxOVoXDTIxMDkzMDE0MDExNVow
    PzEkMCIGA1UEChMbRGlnaXRhbCBTaWduYXR1cmUgVHJ1c3QgQ28uMRcwFQYDVQQD
    Ew5EU1QgUm9vdCBDQSBYMzCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEB
    AN+v6ZdQCINXtMxiZfaQguzH0yxrMMpb7NnDfcdAwRgUi+DoM3ZJKuM/IUmTrE4O
    rz5Iy2Xu/NMhD2XSKtkyj4zl93ewEnu1lcCJo6m67XMuegwGMoOifooUMM0RoOEq
    OLl5CjH9UL2AZd+3UWODyOKIYepLYYHsUmu5ouJLGiifSKOeDNoJjj4XLh7dIN9b
    xiqKqy69cK3FCxolkHRyxXtqqzTWMIn/5WgTe1QLyNau7Fqckh49ZLOMxt+/yUFw
    7BZy1SbsOFU5Q9D8/RhcQPGX69Wam40dutolucbY38EVAjqr2m7xPi71XAicPNaD
    aeQQmxkqtilX4+U9m5/wAl0CAwEAAaNCMEAwDwYDVR0TAQH/BAUwAwEB/zAOBgNV
    HQ8BAf8EBAMCAQYwHQYDVR0OBBYEFMSnsaR7LHH62+FLkHX/xBVghYkQMA0GCSqG
    SIb3DQEBBQUAA4IBAQCjGiybFwBcqR7uKGY3Or+Dxz9LwwmglSBd49lZRNI+DT69
    ikugdB/OEIKcdBodfpga3csTS7MgROSR6cz8faXbauX+5v3gTt23ADq1cEmv8uXr
    AvHRAosZy5Q6XkjEGB5YGV8eAlrwDPGxrancWYaLbumR9YbK+rlmM6pZW87ipxZz
    R8srzJmwN0jP41ZL9c8PDHIyh8bwRLtTcm1D9SZImlJnt1ir/md2cXjbDaJWFBM5
    JDGFoqgCWjBH4d1QB7wCCZAA62RjYJsWvIjJEubSfZGL+T0yjWW06XyxV3bqxbYo
    Ob8VZRzI9neWagqNdwvYkQsEjgfbKbYK7p2CNTUQ
    -----END CERTIFICATE-----

    For convenience, you can also paste the certificate above. Don't do this on sensitive websites though.


    Then, execute GetSSL:

    ./getssl -u -a

    Verify if your certificates are OK:

    # openssl verify -CAfile /etc/letsencrypt/le.crt /etc/letsencrypt/example.org.crt
    /etc/letsencrypt/example.org.crt: OK

    Restart Apache:

    # service httpd restart
    Stopping httpd: [ OK ]
    Starting httpd:

    Finally, edit your PowerMTA config:

    smtp-server-tls-certificate /etc/letsencrypt/example.org.crt
    smtp-server-tls-ca-file /etc/letsencrypt/le.crt

    <source 0/0>
    allow-starttls yes
    require-starttls-before-auth yes
    </source>

    Reload PowerMTA:

    # service pmta restart
    Stopping PowerMTA: [ OK ]
    Starting PowerMTA: [ OK ]

    Let's Encrypt's certificate expires every 90 days, so you need to update your crontab:

    # crontab -e

    Insert the following line in the crontab:

    0 0 1 * * /root/getssl/getssl -u -a

    Remember to protect your private keys and set the appropriate permissions. Just leave a comment if I missed some steps.