Merge pull request #41 from jingweno/fix_no_such_file_host

Create known_hosts file if it doesn't exist

host/host.go

@@ -25,6 +25,10 @@ import (
 )
 
 func NewPromptingHostKeyCallback(stdin io.Reader, stdout io.Writer, knownHostsFilename string) (ssh.HostKeyCallback, error) {
+	if err := createFileIfNotExist(knownHostsFilename); err != nil {
+		return nil, err
+	}
+
 	cb, err := knownhosts.New(knownHostsFilename)
 	if err != nil {
 		return nil, err
@@ -299,3 +303,17 @@ func (c *Host) Run(ctx context.Context) error {
 func keyType(t string) string {
 	return strings.ToUpper(strings.TrimPrefix(t, "ssh-"))
 }
+
+func createFileIfNotExist(file string) error {
+	_, err := os.Stat(file)
+	if os.IsNotExist(err) {
+		file, err := os.Create(file)
+		if err != nil {
+			return err
+		}
+
+		defer file.Close()
+	}
+
+	return nil
+}

host/host_test.go

@@ -5,6 +5,7 @@ import (
 	"io/ioutil"
 	"net"
 	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 
@@ -16,6 +17,41 @@ const (
 	testPublicKey = `ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIN0EWrjdcHcuMfI8bGAyHPcGsAc/vd/gl5673pRkRBGY`
 )
 
+func Test_hostKeyCallbackKnowHostsFileNotExist(t *testing.T) {
+	dir, err := ioutil.TempDir("", "test")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(dir)
+
+	knownHostsFile := filepath.Join(dir, "known_hosts")
+
+	stdin := bytes.NewBufferString("yes\n") // Simulate typing "yes" in stdin
+	stdout := bytes.NewBuffer(nil)
+
+	pk, _, _, _, err := ssh.ParseAuthorizedKey([]byte(testPublicKey))
+	if err != nil {
+		t.Fatal(err)
+	}
+	fp := utils.FingerprintSHA256(pk)
+
+	cb, err := NewPromptingHostKeyCallback(stdin, stdout, knownHostsFile)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	addr := &net.TCPAddr{
+		IP:   net.IPv4(127, 0, 0, 1),
+		Port: 22,
+	}
+	if err := cb("127.0.0.1:22", addr, pk); err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(stdout.String(), "ED25519 key fingerprint is "+fp) {
+		t.Fatalf("stdout should contain fingerprint %s: %s", fp, stdout)
+	}
+}
+
 func Test_hostKeyCallback(t *testing.T) {
 	tmpfile, err := ioutil.TempFile("", "known_hosts")
 	if err != nil {