gnutls-serv command examples

gnutls-serv command examples

gnutls-serv – GnuTLS server

Running your own TLS server based on GnuTLS can be useful when debugging clients and/or GnuTLS itself. This section describes how to use gnutls-serv as a simple HTTPS server.

The most basic server can be started as:

gnutls-serv --http --priority "NORMAL:+ANON-ECDH:+ANON-DH"

It will only support anonymous ciphersuites, which many TLS clients refuse to use.

The next step is to add support for X.509. First we generate a CA:

$ certtool --generate-privkey > x509-ca-key.pem
$ echo 'cn = GnuTLS test CA' > ca.tmpl
$ echo 'ca' >> ca.tmpl
$ echo 'cert_signing_key' >> ca.tmpl
$ certtool --generate-self-signed --load-privkey x509-ca-key.pem --template ca.tmpl --outfile x509-ca.pem

Then generate a server certificate. Remember to change the dns_name value to the name of your server host, or skip that command to avoid the field.

$ certtool --generate-privkey > x509-server-key.pem
$ echo 'organization = GnuTLS test server' > server.tmpl
$ echo 'cn =' >> server.tmpl
$ echo 'tls_www_server' >> server.tmpl
$ echo 'encryption_key' >> server.tmpl
$ echo 'signing_key' >> server.tmpl
$ echo 'dns_name =' >> server.tmpl
$ certtool --generate-certificate --load-privkey x509-server-key.pem --load-ca-certificate x509-ca.pem --load-ca-privkey x509-ca-key.pem --template server.tmpl --outfile x509-server.pem

For use in the client, you may want to generate a client certificate as well.

$ certtool --generate-privkey > x509-client-key.pem
$ echo 'cn = GnuTLS test client' > client.tmpl
$ echo 'tls_www_client' >> client.tmpl
$ echo 'encryption_key' >> client.tmpl
$ echo 'signing_key' >> client.tmpl
$ certtool --generate-certificate --load-privkey x509-client-key.pem --load-ca-certificate x509-ca.pem --load-ca-privkey x509-ca-key.pem --template client.tmpl --outfile x509-client.pem

To be able to import the client key/certificate into some applications, you will need to convert them into a PKCS#12 structure. This also encrypts the security sensitive key with a password.

$ certtool --to-p12 --load-ca-certificate x509-ca.pem --load-privkey x509-client-key.pem --load-certificate x509-client.pem --outder --outfile x509-client.p12

For icing, we’ll create a proxy certificate for the client too.

$ certtool --generate-privkey > x509-proxy-key.pem
$ echo 'cn = GnuTLS test client proxy' > proxy.tmpl
$ certtool --generate-proxy --load-privkey x509-proxy-key.pem --load-ca-certificate x509-client.pem --load-ca-privkey x509-client-key.pem --load-certificate x509-client.pem --template proxy.tmpl --outfile x509-proxy.pem

Then start the server again:

$ gnutls-serv --http --x509cafile x509-ca.pem --x509keyfile x509-server-key.pem --x509certfile x509-server.pem

Try connecting to the server using your web browser. Note that the server listens to port 5556 by default.

While you are at it, to allow connections using DSA, you can also create a DSA key and certificate for the server. These credentials will be used in the final example below.

$ certtool --generate-privkey --dsa > x509-server-key-dsa.pem
$ certtool --generate-certificate --load-privkey x509-server-key-dsa.pem --load-ca-certificate x509-ca.pem --load-ca- 
\ privkey x509-ca-key.pem --template server.tmpl --outfile x509-server-dsa.pem
The next step is to create OpenPGP credentials for the server.

gpg –gen-key

Make a note of the OpenPGP key identifier of the newly generated key, here it was 5D1D14D8. You will need to export the key for GnuTLS to be able to use it.

gpg -a --export 5D1D14D8 > openpgp-server.txt
gpg --export 5D1D14D8 > openpgp-server.bin
gpg --export-secret-keys 5D1D14D8 > openpgp-server-key.bin
gpg -a --export-secret-keys 5D1D14D8 > openpgp-server-key.txt

Let’s start the server with support for OpenPGP credentials:

gnutls-serv --http --priority NORMAL:+CTYPE-OPENPGP --pgpkeyfile openpgp-server-key.txt --pgpcertfile openpgp-server.txt

The next step is to add support for SRP authentication. This requires an SRP password file created with srptool. To start the server with SRP support:

#gnutls-serv --http --priority NORMAL:+SRP-RSA:+SRP --srppasswdconf srp-tpasswd.conf --srppasswd srp-passwd.txt

Let’s also start a server with support for PSK. This would require a password file created with psktool.

gnutls-serv --http --priority NORMAL:+ECDHE-PSK:+PSK --pskpasswd psk-passwd.txt

Finally, we start the server with all the earlier parameters and you get this command:

gnutls-serv --http --priority NORMAL:+PSK:+SRP:+CTYPE-OPENPGP --x509cafile x509-ca.pem \
--x509keyfile x509-server-key.pem --x509certfile x509-server.pem --x509dsakeyfile \
x509-server-key-dsa.pem --x509dsacertfile x509-server-dsa.pem --pgpkeyfile \
openpgp-server-key.txt --pgpcertfile openpgp-server.txt --srppasswdconf \
srp-tpasswd.conf --srppasswd srp-passwd.txt --pskpasswd psk-passwd.txt

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