Asynchronous SSL sockets in Perl 6
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Latest commit a26149f Apr 12, 2017 @jnthn committed on GitHub Merge pull request #1 from gfldex/master
add t/meta.t and it's deps; please Test::META

README.md

IO::Socket::Async::SSL

This module provides a secure sockets implementation with an API very much like that of the Perl 6 built-in IO::Socket::Async class. For the client case, provided the standard certificate and host verification are sufficient, it is drop-in replacement. The server case only needs two extra arguments to listen, specifying the server key and certificate.

As with IO::Socket::Async, it is safe to have concurrent connections and to share them across threads.

Synopsis

Client:

use IO::Socket::Async::SSL;

my $conn = await IO::Socket::Async::SSL.connect('www.perl6.org', 443);
$conn.print: "GET / HTTP/1.0\r\nHost: www.perl6.org\r\n\r\n";
react {
    whenever $conn {
        .print
    }
}
$conn.close;

Server (assumes certificate and key files server-crt.pem and server-key.pem):

use IO::Socket::Async::SSL;

react {
    my %ssl-config =
        certificate-file => 'server-crt.pem',
        private-key-file => 'server-key.pem';
    whenever IO::Socket::Async::SSL.listen('localhost', 4433, |%ssl-config) -> $conn {
        my $req = '';
        whenever $conn {
            $req ~= $_;
            if $req.contains("\r\n\r\n") {
                say $req.lines[0];
                await $conn.print(
                    "HTTP/1.0 200 OK\r\nContent-type: text/html\r\n\r\n" ~
                    "<strong>Hello from a Perl 6 HTTP server</strong>\n");
                $conn.close;
            }
        }
    }
}

Client

The connect method on IO::Socket::Async::SSL is used to establish a SSL connection to a server. It requies two positional arguments, which specify the host and port to connect to. It returns a Promise, which will be kept with an IO::Socket::Async::SSL instance when the connection is established and the SSL handshake completed.

my $conn = await IO::Socket::Async::SSL.connect($host, $port);

By default, the SSL certificate will be verified, using the default set of accepted Certificate Authorities. The Promise return by conenct will be broken if verification fails.

Sometimes it is convenient to create a CA and use it to sign certificates for internal use, for example to secure communications between a set of services on an internal network. In this case, the ca-file named argument can be passed to specify the certificate authority certificate file:

my $ca-file = '/config/ca-crt.pem';
my $conn = await IO::Socket::Async::SSL.connect('user-service', 443, :$ca-file);

Alternatively, a ca-path argument can be specified, indicating a directory where one or more certificates may be found.

It is possible to disable certificate verification by passing the insecure named argument a true value. As the name suggests, this is not a secure configuration, since there is no way for the client to be sure that it is communicating with the intended server. Therefore, it is vulnerable to man-in-the-middle attacks.

Server

The listen method returns a Supply that, when tapped, will start an SSL server. The server can be shut down by closing the tap. Whenever a connection is made to the server, the Supply will emit an IO::Socket::Async::SSL instance. The listen method requires two positional arguments, specifying the host and port to listen on. Two named arguments are also required, providing the certificate-file and private-key-file.

my %ssl-config =
    certificate-file => 'server-crt.pem',
    private-key-file => 'server-key.pem';
my $connections = IO::Socket::Async::SSL.listen('localhost', 4433, |%ssl-config);
react {
    my $listener = do whenever $connections -> $conn {
        say "Got a connection!";
        $conn.close;
    }

    whenever signal(SIGINT) {
        say "Shutting down...";
        $listener.close;
        exit;
    }
}

Common client and server functionality

Both the connect and listen methods take the following optional named arguments:

  • enc, which specifies the encoding to use when the socket is used in character mode. Defaults to utf-8.
  • scheduler, which specifies the scheduler to use for processing events from the underlying IO::Socket::Async instance. The default is $*SCHEDULER. There is rarely a need to change this.

The Supply, print, write, and close methods have the same semantics as in IO::Socket::Async.

Bugs, feature requests, and contributions

Please use GitHub Issues to file bug reports and feature requests. If you wish to contribute to this module, please file a GitHub Pull Request, or email a Git patch (produced using format-patch) to jnthn@jnthn.net.