lib/sign: initial implementation

Added the initial version of signing interface allowing to allowing to
sign and verify commits.
Implemented initial signing modules:
 - dummy -- simple module allowing to sign/verify with ASCII string
 - ed25519 -- module allowing to sign/verify commit with ed25519
   (EdDSA) signature scheme provided by libsodium library.

Signed-off-by: Denis Pynkin <denis.pynkin@collabora.com>

src/libostree/ostree-sign.h

@@ -0,0 +1,156 @@
+/* vim:set et sw=2 cin cino=t0,f0,(0,{s,>2s,n-s,^-s,e2s: */
+
+/*
+ * Copyright © 2019 Collabora Ltd.
+ *
+ * SPDX-License-Identifier: LGPL-2.0+
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ *
+ * Authors:
+ *  - Denis Pynkin (d4s) <denis.pynkin@collabora.com>
+ */
+
+#pragma once
+
+#include <glib.h>
+#include <glib-object.h>
+
+#include "ostree-ref.h"
+#include "ostree-remote.h"
+#include "ostree-types.h"
+
+/* Special remote */
+#define OSTREE_SIGN_ALL_REMOTES "__OSTREE_ALL_REMOTES__"
+
+
+G_BEGIN_DECLS
+
+#define OSTREE_TYPE_SIGN (ostree_sign_get_type ())
+
+_OSTREE_PUBLIC
+G_DECLARE_INTERFACE (OstreeSign, ostree_sign, OSTREE, SIGN, GObject)
+
+struct _OstreeSignInterface
+{
+  GTypeInterface g_iface;
+  gchar *(* get_name) (OstreeSign *self);
+  gboolean (* data)   (OstreeSign *self,
+                       GBytes *data,
+                       GBytes **signature,
+                       GCancellable *cancellable,
+                       GError **error);
+  gchar *(* metadata_key) (OstreeSign *self);
+  gchar *(* metadata_format) (OstreeSign *self);
+  gboolean (* metadata_verify) (OstreeSign *self,
+                                GBytes *data,
+                                GVariant   *metadata,
+                                GError **error);
+
+  gboolean (* set_sk) (OstreeSign *self,
+                       GVariant *secret_key,
+                       GError **error);
+
+  gboolean (* set_pk) (OstreeSign *self,
+                       GVariant *public_key,
+                       GError **error);
+
+  gboolean (* load_pk) (OstreeSign *self,
+                        gchar *remote_name,
+                        GError **error);
+
+};
+
+_OSTREE_PUBLIC
+const gchar * ostree_sign_get_name (OstreeSign *self);
+
+_OSTREE_PUBLIC
+gboolean ostree_sign_data (OstreeSign *self,
+                             GBytes *data,
+                             GBytes **signature,
+                             GCancellable *cancellable,
+                             GError **error);
+
+
+_OSTREE_PUBLIC
+gchar * ostree_sign_metadata_key (OstreeSign *self);
+
+_OSTREE_PUBLIC
+gchar * ostree_sign_metadata_format (OstreeSign *self);
+
+_OSTREE_PUBLIC
+GVariant * ostree_sign_detached_metadata_append (OstreeSign *self,
+                                                 GVariant   *existing_metadata,
+                                                 GBytes     *signature_bytes);
+
+_OSTREE_PUBLIC
+gboolean ostree_sign_commit (OstreeSign     *self,
+                             OstreeRepo     *repo,
+                             const gchar    *commit_checksum,
+                             GCancellable   *cancellable,
+                             GError         **error);
+
+_OSTREE_PUBLIC
+gboolean ostree_sign_metadata_verify (OstreeSign *self,
+                                      GBytes     *data,
+                                      GVariant   *signatures,
+                                      GError     **error);
+
+_OSTREE_PUBLIC
+gboolean ostree_sign_commit_verify (OstreeSign *self,
+                                    OstreeRepo     *repo,
+                                    const gchar    *commit_checksum,
+                                    GCancellable   *cancellable,
+                                    GError         **error);
+
+_OSTREE_PUBLIC
+gboolean ostree_sign_set_sk (OstreeSign *self,
+                             GVariant *secret_key,
+                             GError **error);
+
+_OSTREE_PUBLIC
+gboolean ostree_sign_set_pk (OstreeSign *self,
+                             GVariant *public_key,
+                             GError **error);
+
+_OSTREE_PUBLIC
+gboolean ostree_sign_load_pk (OstreeSign *self,
+                              gchar *remote_name,
+                              GError **error);
+
+
+/**
+ * ostree_sign_list_names:
+ *
+ * Return the array with all available sign modules names.
+ *
+ * Returns: (transfer full): an array of strings, free when you used it
+ */
+_OSTREE_PUBLIC
+GStrv ostree_sign_list_names(void);
+
+/**
+ * ostree_sign_get_by_name:
+ *
+ * Tries to find and return proper signing engine by it's name.
+ *
+ * Returns: (transfer full): a constant, free when you used it
+ */
+_OSTREE_PUBLIC
+OstreeSign * ostree_sign_get_by_name (const gchar *name, GError **error);
+
+G_END_DECLS
+