OCI: Add flatpak_oci_registry_get_token() method

This tries to do a HEAD request to the repository and if that fails
with 401 uses the OCI mechanism to (given a basic auth token) generate
a token for the download.

common/flatpak-oci-registry-private.h

@@ -78,6 +78,12 @@ int                    flatpak_oci_registry_download_blob (FlatpakOciRegistry
                                                            gpointer               user_data,
                                                            GCancellable          *cancellable,
                                                            GError               **error);
+char *                 flatpak_oci_registry_get_token (FlatpakOciRegistry *self,
+                                                       const char         *repository,
+                                                       const char         *digest,
+                                                       const char         *basic_auth,
+                                                       GCancellable       *cancellable,
+                                                       GError            **error);
 GBytes             *   flatpak_oci_registry_load_blob (FlatpakOciRegistry *self,
                                                        const char         *repository,
                                                        gboolean            manifest,

common/flatpak-oci-registry.c

@@ -879,6 +879,165 @@ flatpak_oci_registry_mirror_blob (FlatpakOciRegistry    *self,
   return TRUE;
 }
 
+static const char *
+object_get_string_member_with_default (JsonNode *json,
+                                       const char *member_name,
+                                       const char *default_value)
+{
+  JsonNode *node;
+
+  if (json == NULL || !JSON_NODE_HOLDS_OBJECT(json))
+    return default_value;
+
+  node = json_object_get_member (json_node_get_object (json), member_name);
+
+  if (node == NULL || JSON_NODE_HOLDS_NULL (node) || JSON_NODE_TYPE (node) != JSON_NODE_VALUE)
+    return default_value;
+
+  return json_node_get_string (node);
+}
+
+
+static char *
+get_token_for_www_auth (FlatpakOciRegistry *self,
+                        const char    *www_authenticate,
+                        const char    *auth,
+                        GCancellable  *cancellable,
+                        GError        **error)
+{
+  g_autoptr(GInputStream) auth_stream = NULL;
+  g_autoptr(SoupMessage) auth_msg = NULL;
+  g_autoptr(GHashTable) params = NULL;
+  g_autoptr(GHashTable) args = NULL;
+  const char *realm, *service, *scope, *token;
+  g_autoptr(SoupURI) auth_uri = NULL;
+  g_autoptr(GBytes) body = NULL;
+  g_autoptr(JsonNode) json = NULL;
+
+  if (g_ascii_strncasecmp (www_authenticate, "Bearer ", strlen ("Bearer ")) != 0)
+    {
+      g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED, "Only Bearer authentication supported");
+      return NULL;
+    }
+
+  params = soup_header_parse_param_list (www_authenticate + strlen ("Bearer "));
+
+  realm = g_hash_table_lookup (params, "realm");
+  if (realm == NULL)
+    {
+      g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED, "Only realm in authentication request");
+      return NULL;
+    }
+
+  auth_uri = soup_uri_new (realm);
+  if (auth_uri == NULL)
+    {
+      g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED, "Invalid realm in authentication request");
+      return NULL;
+    }
+
+  args = g_hash_table_new_full (g_str_hash, g_str_equal, NULL, NULL);
+  service = g_hash_table_lookup (params, "service");
+  if (service)
+    g_hash_table_insert (args, "service", (char *)service);
+  scope = g_hash_table_lookup (params, "scope");
+  if (scope)
+    g_hash_table_insert (args, "scope", (char *)scope);
+
+  soup_uri_set_query_from_form (auth_uri, args);
+
+  auth_msg = soup_message_new_from_uri ("GET", auth_uri);
+
+  g_autofree char *basic_auth = g_strdup_printf ("Basic %s", auth);
+  soup_message_headers_replace (auth_msg->request_headers, "Authorization", basic_auth);
+
+  auth_stream = soup_session_send (self->soup_session, auth_msg, NULL, error);
+  if (auth_stream == NULL)
+    return NULL;
+
+  body = flatpak_read_stream (auth_stream, TRUE, error);
+  if (body == NULL)
+    return NULL;
+
+  json = json_from_string ((char *)g_bytes_get_data (body, NULL), error);
+  if (json == NULL)
+    return NULL;
+
+  token = object_get_string_member_with_default (json, "token", NULL);
+  if (token == NULL)
+    {
+      g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED, "Invalid authentication request response");
+      return NULL;
+    }
+
+  return g_strdup (token);
+}
+
+char *
+flatpak_oci_registry_get_token (FlatpakOciRegistry *self,
+                                const char         *repository,
+                                const char         *digest,
+                                const char         *basic_auth,
+                                GCancellable       *cancellable,
+                                GError            **error)
+{
+  g_autofree char *subpath = NULL;
+  g_autoptr(SoupURI) uri = NULL;
+  g_autoptr(GBytes) bytes = NULL;
+  g_autofree char *uri_s = NULL;
+  g_autoptr(GInputStream) stream = NULL;
+  g_autoptr(SoupMessage) msg = NULL;
+  g_autofree char *www_authenticate = NULL;
+  g_autofree char *token = NULL;
+
+  g_assert (self->valid);
+
+  subpath = get_digest_subpath (self, repository, TRUE, digest, error);
+  if (subpath == NULL)
+    return NULL;
+
+  if (self->dfd != -1)
+    return g_strdup (""); // No tokens for local repos
+
+  uri = soup_uri_new_with_base (self->base_uri, subpath);
+  if (uri == NULL)
+    {
+      g_set_error (error, G_IO_ERROR, G_IO_ERROR_INVALID_ARGUMENT,
+                   "Invalid relative url %s", subpath);
+      return NULL;
+    }
+
+  msg = soup_message_new_from_uri ("HEAD", uri);
+
+  stream = soup_session_send (self->soup_session, msg, NULL, error);
+  if (stream == NULL)
+    return NULL;
+
+  if (SOUP_STATUS_IS_SUCCESSFUL (msg->status_code))
+    {
+      return g_strdup ("");
+    }
+  else if (msg->status_code != SOUP_STATUS_UNAUTHORIZED)
+    {
+      g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED, "Unexpected response status %d from repo", msg->status_code);
+      return NULL;
+    }
+
+  /* Need www-authenticated header */
+  www_authenticate = g_strdup (soup_message_headers_get_one (msg->response_headers, "WWW-Authenticate"));
+  if (www_authenticate == NULL)
+    {
+      g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED, "Now WWW-Authenticate header from repo");
+      return NULL;
+    }
+
+  token = get_token_for_www_auth (self, www_authenticate, basic_auth, cancellable, error);
+  if (token == NULL)
+    return NULL;
+
+  return g_steal_pointer (&token);
+}
+
 GBytes *
 flatpak_oci_registry_load_blob (FlatpakOciRegistry *self,
                                 const char         *repository,