ssh: Implement authentication for new ssh server

internal/wisski/ingredient/barrel/barrel.go

@@ -1,6 +1,8 @@
 package barrel
 
 import (
+	"path/filepath"
+
 	"github.com/FAU-CDI/wisski-distillery/internal/wisski/ingredient"
 	"github.com/FAU-CDI/wisski-distillery/internal/wisski/ingredient/locker"
 	"github.com/FAU-CDI/wisski-distillery/internal/wisski/ingredient/mstore"
@@ -13,3 +15,11 @@ type Barrel struct {
 	Locker *locker.Locker
 	MStore *mstore.MStore
 }
+
+func (barrel *Barrel) DataPath() string {
+	return filepath.Join(barrel.FilesystemBase, "data")
+}
+
+func (barrel *Barrel) AuthorizedKeysPath() string {
+	return filepath.Join(barrel.DataPath(), "authorized_keys")
+}

internal/wisski/ingredient/barrel/ssh/ssh.go

@@ -0,0 +1,32 @@
+package ssh
+
+import (
+	"io"
+
+	"github.com/FAU-CDI/wisski-distillery/internal/wisski/ingredient"
+	"github.com/FAU-CDI/wisski-distillery/internal/wisski/ingredient/barrel"
+	"github.com/FAU-CDI/wisski-distillery/pkg/environment"
+	"github.com/FAU-CDI/wisski-distillery/pkg/sshx"
+	"github.com/gliderlabs/ssh"
+)
+
+type SSH struct {
+	ingredient.Base
+	Barrel *barrel.Barrel
+}
+
+func (ssh *SSH) Keys() ([]ssh.PublicKey, error) {
+	file, err := ssh.Environment.Open(ssh.Barrel.AuthorizedKeysPath())
+	if environment.IsNotExist(err) {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	bytes, err := io.ReadAll(file)
+	if err != nil {
+		return nil, err
+	}
+	return sshx.ParseAllKeys(bytes), nil
+}