fix(ssh): unable to pass a custom HostKeyCallback func

Don't overwrite HostKeyCallback if one is provided.

Fixes: c35b8082c863 ("plumbing: transport/ssh, auto-populate ClientConfig.HostKeyAlgorithms. Fixes #411")
Fixes: https://github.com/go-git/go-git/issues/654
Signed-off-by: Ayman Bagabas <ayman.bagabas@gmail.com>

1 files changed, 13 insertions, 20 deletions

diff --git a/plumbing/transport/ssh/common.go b/plumbing/transport/ssh/common.go
index 4b9ac07..e06958a 100644
--- a/plumbing/transport/ssh/common.go
+++ b/plumbing/transport/ssh/common.go
@@ -10,6 +10,7 @@ import (
 
 	"github.com/go-git/go-git/v5/plumbing/transport"
 	"github.com/go-git/go-git/v5/plumbing/transport/internal/common"
+	"github.com/skeema/knownhosts"
 
 	"github.com/kevinburke/ssh_config"
 	"golang.org/x/crypto/ssh"
@@ -122,9 +123,18 @@ func (c *command) connect() error {
 		return err
 	}
 	hostWithPort := c.getHostWithPort()
-	config, err = SetConfigHostKeyFields(config, hostWithPort)
-	if err != nil {
-		return err
+	if config.HostKeyCallback == nil {
+		kh, err := newKnownHosts()
+		if err != nil {
+			return err
+		}
+		config.HostKeyCallback = kh.HostKeyCallback()
+		config.HostKeyAlgorithms = kh.HostKeyAlgorithms(hostWithPort)
+	} else if len(config.HostKeyAlgorithms) == 0 {
+		// Set the HostKeyAlgorithms based on HostKeyCallback.
+		// For background see https://github.com/go-git/go-git/issues/411 as well as
+		// https://github.com/golang/go/issues/29286 for root cause.
+		config.HostKeyAlgorithms = knownhosts.HostKeyAlgorithms(config.HostKeyCallback, hostWithPort)
 	}
 
 	overrideConfig(c.config, config)
@@ -167,23 +177,6 @@ func dial(network, addr string, config *ssh.ClientConfig) (*ssh.Client, error) {
 	return ssh.NewClient(c, chans, reqs), nil
 }
 
-// SetConfigHostKeyFields sets cfg.HostKeyCallback and cfg.HostKeyAlgorithms
-// based on OpenSSH known_hosts. cfg is modified in-place. hostWithPort must be
-// supplied, since the algorithms will be set based on the known host keys for
-// that specific host. Otherwise, golang.org/x/crypto/ssh can return an error
-// upon connecting to a host whose *first* key is not known, even though other
-// keys (of different types) are known and match properly.
-// For background see https://github.com/go-git/go-git/issues/411 as well as
-// https://github.com/golang/go/issues/29286 for root cause.
-func SetConfigHostKeyFields(cfg *ssh.ClientConfig, hostWithPort string) (*ssh.ClientConfig, error) {
-	kh, err := newKnownHosts()
-	if err == nil {
-		cfg.HostKeyCallback = kh.HostKeyCallback()
-		cfg.HostKeyAlgorithms = kh.HostKeyAlgorithms(hostWithPort)
-	}
-	return cfg, err
-}
-
 func (c *command) getHostWithPort() string {
 	if addr, found := c.doGetHostWithPortFromSSHConfig(); found {
 		return addr