libgit2: change knownHostsCallback logic

With Go backing the transport, the provided hostname to the callback
now does include the port, and we no longer need to take the `Host`
into account (as this will now result in a mismatch).

Signed-off-by: Hidde Beydals <hello@hidde.co>

pkg/git/libgit2/transport.go

@@ -25,7 +25,6 @@ import (
 	"crypto/x509"
 	"fmt"
 	"hash"
-	"net"
 	"strings"
 	"time"
 
@@ -128,26 +127,17 @@ func knownHostsCallback(host string, knownHosts []byte) git2go.CertificateCheckC
 			return fmt.Errorf("failed to parse known_hosts: %w", err)
 		}
 
-		// First, attempt to split the configured host and port to validate
-		// the port-less hostname given to the callback.
-		h, _, err := net.SplitHostPort(host)
-		if err != nil {
-			// SplitHostPort returns an error if the host is missing
-			// a port, assume the host has no port.
-			h = host
-		}
-
 		// Check if the configured host matches the hostname given to
 		// the callback.
-		if h != hostname {
-			return fmt.Errorf("hostname from server '%s' does not match '%s'", hostname, h)
+		if host != hostname {
+			return fmt.Errorf("hostname from server '%s' does not match '%s'", hostname, host)
 		}
 
 		// We are now certain that the configured host and the hostname
 		// given to the callback match. Use the configured host (that
 		// includes the port), and normalize it, so we can check if there
 		// is an entry for the hostname _and_ port.
-		h = knownhosts.Normalize(host)
+		h := knownhosts.Normalize(hostname)
 		for _, k := range kh {
 			if k.matches(h, cert.Hostkey) {
 				return nil

pkg/git/libgit2/transport_test.go

@@ -221,7 +221,7 @@ func Test_knownHostsCallback(t *testing.T) {
 		},
 		{
 			name:         "Match with port",
-			host:         "github.com",
+			host:         "github.com:22",
 			knownHosts:   []byte(knownHostsFixture),
 			hostkey:      git2go.HostkeyCertificate{Kind: git2go.HostkeySHA1 | git2go.HostkeyMD5, HashSHA1: sha1Fingerprint("v2toJdKXfFEaR1u++4iq1UqSrHM")},
 			expectedHost: "github.com:22",