Tag Archives: TLS

Get certificates for “internal” hosts from Let’s Encrypt

I have a pretty large internal IT “landscape” in my house, and as an IT pro I want everything to be clean and “safe.” So even internally I’m using official SSL (or I should say “TLS”, as SSL 2.0 or 3.0 is deprecated since many years…) certificates for my router, WiFi access points, NAS devices, intranet server, etc., using host names in my own domain. I host this domain DNS-wise myself on a root server I rent from Hetzner.

Before the StartSSL disaster I got my certs from them. Afterwards I switched to WOSign, but now that they had their scandal as well, what to do?!

Well, Let’s Encrypt, a free public CA, is something I’m using anyway for my root server since they started operating. But to verify ownership of a domain name you had to run a web server on that respective host — something I can’t easily do for my internal hosts, as they have private IP addresses only, and their host names are not even publicly visible (they don’t have  a public A record, only one visible in my internal LAN). Even for my router’s externally visible host name I can’t easily use an HTTP-based challenge, as for security reasons I don’t want to operate a web server there.

By chance I came across the dns challenge that is now available in Let’s Encrypt’s certbot. This challenge works by deploying a TXT record that certbot requests to be under this domain name. Once you did this, you tell Let’s Encrypt to check, and if they find the TXT record this proves that you have authority over the domain.

Using it is quite straight forward:

# certbot certonly --manual -d hostname.internal.bergs.biz --preferred-challenges "dns"
[...]
Please deploy a DNS TXT record under the name
_acme-challenge.hostname.internal.bergs.biz with the following value:

YrAE-fmu-Zjsdhsjhd328723hjdhjcjHJJHJhds

Once this is deployed,
-------------------------------------------------------------------------------
Press Enter to Continue

A few seconds later I had successfully received my certificate.

So now I will write a script that will run periodically on my intranet server, and that will retrieve the then-current certificates for my internal hosts from my root server, and deploy them internally.

Enabling Forward Secrecy in Apache

I tried to follow the instructions given in this article by Ivan Ristic, but somehow it seems not to be working, or the test at https://www.ssllabs.com/ssltest/ might be broken… :-(

Unfortunately I can’t seem to comment on Ivan’s article (I even registered just to reply), so I created this blog post, hoping that my trackback will work…

This is what I have in Apache:

SSLHonorCipherOrder On
SSLCipherSuite ECDHE-RSA-AES128-SHA256:AES128-GCM-SHA256:RC4:HIGH:!MD5:!aNULL:!EDH

According to the output of openssl ciphers this should enable the following cipher suites (filtered by only those that contain ECDHE):

ECDHE-RSA-AES128-SHA256 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AES(128)  Mac=SHA256
ECDHE-RSA-RC4-SHA       SSLv3 Kx=ECDH     Au=RSA  Enc=RC4(128)  Mac=SHA1
ECDHE-ECDSA-RC4-SHA     SSLv3 Kx=ECDH     Au=ECDSA Enc=RC4(128)  Mac=SHA1
ECDHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AESGCM(256) Mac=AEAD
ECDHE-ECDSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH     Au=ECDSA Enc=AESGCM(256) Mac=AEAD
ECDHE-RSA-AES256-SHA384 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AES(256)  Mac=SHA384
ECDHE-ECDSA-AES256-SHA384 TLSv1.2 Kx=ECDH     Au=ECDSA Enc=AES(256)  Mac=SHA384
ECDHE-RSA-AES256-SHA    SSLv3 Kx=ECDH     Au=RSA  Enc=AES(256)  Mac=SHA1
ECDHE-ECDSA-AES256-SHA  SSLv3 Kx=ECDH     Au=ECDSA Enc=AES(256)  Mac=SHA1
ECDHE-RSA-DES-CBC3-SHA  SSLv3 Kx=ECDH     Au=RSA  Enc=3DES(168) Mac=SHA1
ECDHE-ECDSA-DES-CBC3-SHA SSLv3 Kx=ECDH     Au=ECDSA Enc=3DES(168) Mac=SHA1
ECDHE-RSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AESGCM(128) Mac=AEAD
ECDHE-ECDSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH     Au=ECDSA Enc=AESGCM(128) Mac=AEAD
ECDHE-ECDSA-AES128-SHA256 TLSv1.2 Kx=ECDH     Au=ECDSA Enc=AES(128)  Mac=SHA256
ECDHE-RSA-AES128-SHA    SSLv3 Kx=ECDH     Au=RSA  Enc=AES(128)  Mac=SHA1
ECDHE-ECDSA-AES128-SHA  SSLv3 Kx=ECDH     Au=ECDSA Enc=AES(128)  Mac=SHA1

As far as I can tell this should include the below cipher suites which supposedly enable forward secrecy:

    TLS_ECDHE_RSA_WITH_RC4_128_SHA
    TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
    TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
    TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA

Unfortunately the above SSL test shows the following when running towards my Apache:

Forward Secrecy 	No

Does anyone know what that means? Is the test just broken, or am I misunderstanding anything?