certfp: Add certfp retrieval from client

irc/socket.go

@@ -6,11 +6,20 @@ package irc
 
 import (
 	"bufio"
+	"crypto/sha256"
+	"crypto/tls"
+	"encoding/hex"
+	"errors"
 	"io"
 	"net"
 	"strings"
 )
 
+var (
+	errNotTls      = errors.New("Not a TLS connection")
+	errNoPeerCerts = errors.New("Client did not provide a certificate")
+)
+
 // Socket represents an IRC socket.
 type Socket struct {
 	Closed bool
@@ -35,6 +44,24 @@ func (socket *Socket) Close() {
 	socket.conn.Close()
 }
 
+// CertFP returns the fingerprint of the certificate provided by the client.
+func (socket *Socket) CertFP() (string, error) {
+	var tlsConn, isTLS = socket.conn.(*tls.Conn)
+	if !isTLS {
+		return "", errNotTls
+	}
+
+	peerCerts := tlsConn.ConnectionState().PeerCertificates
+	if len(peerCerts) < 1 {
+		return "", errNoPeerCerts
+	}
+
+	rawCert := sha256.Sum256(peerCerts[0].Raw)
+	fingerprint := hex.EncodeToString(rawCert[:])
+
+	return fingerprint, nil
+}
+
 // Read returns a single IRC line from a Socket.
 func (socket *Socket) Read() (string, error) {
 	if socket.Closed {