gnutls-serv - GnuTLS server

NAME SYNOPSIS DESCRIPTION OPTIONS EXAMPLES EXIT STATUS SEE ALSO AUTHORS COPYRIGHT BUGS

SYNOPSIS

gnutls-serv [−flags] [−flag [value]] [−−option-name[[=| ]value]]

All arguments must be options.

DESCRIPTION

Server program that listens to incoming TLS connections.

OPTIONS

−d num, −−debug=num Enable debugging. This option takes an integer
number as its argument. The value of num is constrained to being:

in the range 0 through 9999

Specifies the debug level.

−−sni−hostname=str Server’s hostname for server name extension.

Server name of type host_name that the server will recognise as its
own. If the server receives client hello with different name, it will
send a warning−level unrecognized_name alert.

−−sni−hostname−fatal Send fatal alert on sni-hostname mismatch.

−−alpn=str Specify ALPN protocol to be enabled by the server. This
option may appear an unlimited number of times.

Specify the (textual) ALPN protocol for the server to use.

−−alpn−fatal Send fatal alert on non-matching ALPN name.

−−noticket Don’t accept session tickets.

−−earlydata Accept early data.

−−maxearlydata=num The maximum early data size to accept. This option
takes an integer number as its argument. The value of num is
constrained to being:

in the range 1 through 2147483648

−−nocookie Don’t require cookie on DTLS sessions.

−g, −−generate Generate Diffie-Hellman parameters.

−q, −−quiet Suppress some messages.

−−nodb Do not use a resumption database.

−−http Act as an HTTP server.

−−echo Act as an Echo server.

−−crlf Do not replace CRLF by LF in Echo server mode.

−u, −−udp Use DTLS (datagram TLS) over UDP.

−−mtu=num Set MTU for datagram TLS. This option takes an integer
number as its argument. The value of num is constrained to being:

in the range 0 through 17000

−−srtp−profiles=str Offer SRTP profiles.

−a, −−disable−client−cert Do not request a client certificate. This
option must not appear in combination with any of the following
options: require-client-cert.

−r, −−require−client−cert Require a client certificate.

This option before 3.6.0 used to imply −−verify−client−cert. Since
3.6.0 it will no longer verify the certificate by default.

−−verify−client−cert If a client certificate is sent then verify it.

Do not require, but if a client certificate is sent then verify it and
close the connection if invalid.

−−compress−cert=str Compress certificate. This option may appear an
unlimited number of times.

This option sets a supported compression method for certificate
compression.

−b, −−heartbeat Activate heartbeat support.

Regularly ping client via heartbeat extension messages

−−x509fmtder Use DER format for certificates to read from.

−−priority=str Priorities string.

TLS algorithms and protocols to enable. You can use predefined sets of
ciphersuites such as PERFORMANCE, NORMAL, SECURE128, SECURE256. The
default is NORMAL.

Check the GnuTLS manual on section “Priority strings” for more
information on allowed keywords

−−dhparams=file DH params file to use.

−−x509cafile=str Certificate file or PKCS #11 URL to use.

−−x509crlfile=file CRL file to use.

−−pgpkeyfile=file PGP Key file to use.

NOTE: THIS OPTION IS DEPRECATED
−−x509keyfile=str X.509 key file or PKCS #11 URL to use. This option
may appear an unlimited number of times.

Specify the private key file or URI to use; it must correspond to the
certificate specified in −−x509certfile. Multiple keys and certificates
can be specified with this option and in that case each occurrence of
keyfile must be followed by the corresponding x509certfile or
vice−versa.

−−x509certfile=str X.509 Certificate file or PKCS #11 URL to use. This
option may appear an unlimited number of times.

Specify the certificate file or URI to use; it must correspond to the
key specified in −−x509keyfile. Multiple keys and certificates can be
specified with this option and in that case each occurrence of keyfile
must be followed by the corresponding x509certfile or vice−versa.

−−x509dsakeyfile This is an alias for the --x509keyfile option.

NOTE: THIS OPTION IS DEPRECATED
−−x509dsacertfile This is an alias for the --x509certfile option.

NOTE: THIS OPTION IS DEPRECATED
−−x509ecckeyfile This is an alias for the --x509keyfile option.

NOTE: THIS OPTION IS DEPRECATED
−−x509ecccertfile This is an alias for the --x509certfile option.

NOTE: THIS OPTION IS DEPRECATED
−−rawpkkeyfile=str Private key file (PKCS #8 or PKCS #12) or PKCS #11
URL to use. This option may appear an unlimited number of times.

Specify the private key file or URI to use; it must correspond to the
raw public−key specified in −−rawpkfile. Multiple key pairs can be
specified with this option and in that case each occurrence of keyfile
must be followed by the corresponding rawpkfile or vice−versa.

In order to instruct the application to negotiate raw public keys one
must enable the respective certificate types via the priority strings
(i.e. CTYPE−CLI−* and CTYPE−SRV−* flags).

Check the GnuTLS manual on section “Priority strings” for more
information on how to set certificate types.

−−rawpkfile=str Raw public-key file to use. This option may appear an
unlimited number of times. This option must appear in combination with
the following options: rawpkkeyfile.

Specify the raw public−key file to use; it must correspond to the
private key specified in −−rawpkkeyfile. Multiple key pairs can be
specified with this option and in that case each occurrence of keyfile
must be followed by the corresponding rawpkfile or vice−versa.

In order to instruct the application to negotiate raw public keys one
must enable the respective certificate types via the priority strings
(i.e. CTYPE−CLI−* and CTYPE−SRV−* flags).

Check the GnuTLS manual on section “Priority strings” for more
information on how to set certificate types.

−−srppasswd=file SRP password file to use.

−−srppasswdconf=file SRP password configuration file to use.

−−pskpasswd=file PSK password file to use.

−−pskhint=str PSK identity hint to use.

−−ocsp−response=str The OCSP response to send to client. This option
may appear an unlimited number of times.

If the client requested an OCSP response, return data from this file to
the client.

−−ignore−ocsp−response−errors Ignore any errors when setting the OCSP
response.

That option instructs gnutls to not attempt to match the provided OCSP
responses with the certificates.

−p num, −−port=num The port to connect to. This option takes an
integer number as its argument.

−l, −−list Print a list of the supported algorithms and modes.

Print a list of the supported algorithms and modes. If a priority
string is given then only the enabled ciphersuites are shown.

−−provider=file Specify the PKCS #11 provider library.

This will override the default options in /etc/gnutls/pkcs11.conf

−−keymatexport=str Label used for exporting keying material.

−−keymatexportsize=num Size of the exported keying material. This
option takes an integer number as its argument.

−−recordsize=num The maximum record size to advertise. This option
takes an integer number as its argument. The value of num is
constrained to being:

in the range 0 through 16384

−−httpdata=file The data used as HTTP response.

−−timeout=num The timeout period for server. This option takes an
integer number as its argument.

−−attime=timestamp Perform validation at the timestamp instead of the
system time.

timestamp is an instance in time encoded as Unix time or in a human
readable timestring such as "29 Feb 2004", "2004−02−29". Full
documentation available at
<https://www.gnu.org/software/coreutils/manual/html_node/Date−input−formats.html>
or locally via info ’(coreutils) date invocation’.

−v arg, −−version=arg Output version of program and exit. The default
mode is ‘v’, a simple version. The ‘c’ mode will print copyright
information and ‘n’ will print the full copyright notice.

−h, −−help Display usage information and exit.

−!, −−more−help Pass the extended usage information through a pager.

EXAMPLES

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 = test.gnutls.org’ >> server.tmpl
$ echo ’tls_www_server’ >> server.tmpl
$ echo ’encryption_key’ >> server.tmpl
$ echo ’signing_key’ >> server.tmpl
$ echo ’dns_name = test.gnutls.org’ >> 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 ECDSA, you can also create a ECDSA key and certificate for the server. These credentials will be used in the final example below.

$ certtool −−generate−privkey −−ecdsa > x509−server−key−ecc.pem
$ certtool −−generate−certificate −−load−privkey x509−server−key−ecc.pem −−load−ca−certificate x509−ca.pem −−load−ca−privkey x509−ca−key.pem −−template server.tmpl −−outfile x509−server−ecc.pem

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

If you want a server with support for raw public−keys we can also add these credentials. Note however that there is no identity information linked to these keys as is the case with regular x509 certificates. Authentication must be done via different means. Also we need to explicitly enable raw public−key certificates via the priority strings.

gnutls−serv −−http −−priority NORMAL:+CTYPE−CLI−RAWPK:+CTYPE−SRV−RAWPK −−rawpkfile srv.rawpk.pem −−rawpkkeyfile srv.key.pem

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

gnutls−serv −−http −−priority NORMAL:+PSK:+SRP:+CTYPE−CLI−RAWPK:+CTYPE−SRV−RAWPK −−x509cafile x509−ca.pem −−x509keyfile x509−server−key.pem −−x509certfile x509−server.pem −−x509keyfile x509−server−key−ecc.pem −−x509certfile x509−server−ecc.pem −−srppasswdconf srp−tpasswd.conf −−srppasswd srp−passwd.txt −−pskpasswd psk−passwd.txt −−rawpkfile srv.rawpk.pem −−rawpkkeyfile srv.key.pem