sign: Add PEM reading facility

This adds a new class OstreePemReader, which reads PEM blocks from an
input stream.  This would be useful for the "x509" signing backend, as
the keys are typically stored in the PEM format.

Signed-off-by: Daiki Ueno <[email protected]>

Makefile-libostree.am

@@ -268,6 +268,9 @@ libostree_1_la_SOURCES += \
 	src/libostree/ostree-blob-reader-base64.h \
 	src/libostree/ostree-blob-reader-raw.c \
 	src/libostree/ostree-blob-reader-raw.h \
+	src/libostree/ostree-blob-reader-pem.c \
+	src/libostree/ostree-blob-reader-pem.h \
+	src/libostree/ostree-blob-reader-private.h \
 	$(NULL)
 
 if USE_COMPOSEFS

Makefile-tests.am

@@ -270,7 +270,7 @@ _installed_or_uninstalled_test_programs = tests/test-varint tests/test-ot-unix-u
 	tests/test-keyfile-utils tests/test-ot-opt-utils tests/test-ot-tool-util \
 	tests/test-checksum tests/test-lzma tests/test-rollsum \
 	tests/test-basic-c tests/test-sysroot-c tests/test-pull-c tests/test-repo tests/test-include-ostree-h tests/test-kargs \
-	tests/test-rfc2616-dates
+	tests/test-rfc2616-dates tests/test-pem
 
 if USE_GPGME
 _installed_or_uninstalled_test_programs += \
@@ -403,6 +403,12 @@ tests_test_rfc2616_dates_SOURCES = \
 tests_test_rfc2616_dates_CFLAGS = $(TESTS_CFLAGS)
 tests_test_rfc2616_dates_LDADD = $(TESTS_LDADD)
 
+tests_test_pem_SOURCES = \
+	src/libostree/ostree-blob-reader-pem.c \
+	tests/test-pem.c
+tests_test_pem_CFLAGS = $(TESTS_CFLAGS)
+tests_test_pem_LDADD = $(TESTS_LDADD)
+
 noinst_PROGRAMS += tests/test-commit-sign-sh-ext
 tests_test_commit_sign_sh_ext_CFLAGS = $(TESTS_CFLAGS)
 tests_test_commit_sign_sh_ext_LDADD = $(TESTS_LDADD)

src/libostree/ostree-blob-reader-pem.c

@@ -0,0 +1,225 @@
+/*
+ * 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, see <https://www.gnu.org/licenses/>.
+ */
+
+/* This implements a simple parser of the PEM format defined in RFC
+ * 7468, which doesn't allow headers to be encoded alongside the data
+ * (unlike the legacy RFC 1421).
+ */
+
+#include "config.h"
+
+#include "ostree-blob-reader-pem.h"
+#include "ostree-blob-reader-private.h"
+#include <string.h>
+
+enum
+{
+  PROP_0,
+  PROP_LABEL
+};
+
+struct _OstreeBlobReaderPem
+{
+  GDataInputStream parent_instance;
+
+  gchar *label;
+};
+
+static void ostree_blob_reader_pem_iface_init (OstreeBlobReaderInterface *iface);
+G_DEFINE_TYPE_WITH_CODE (OstreeBlobReaderPem, _ostree_blob_reader_pem, G_TYPE_DATA_INPUT_STREAM,
+                         G_IMPLEMENT_INTERFACE (OSTREE_TYPE_BLOB_READER,
+                                                ostree_blob_reader_pem_iface_init));
+
+static void
+ostree_blob_reader_pem_iface_init (OstreeBlobReaderInterface *iface)
+{
+  iface->read_blob = ostree_blob_reader_pem_read_blob;
+}
+
+static void
+ostree_blob_reader_pem_set_property (GObject *object, guint prop_id, const GValue *value,
+                                     GParamSpec *pspec)
+{
+  OstreeBlobReaderPem *self = OSTREE_BLOB_READER_PEM (object);
+
+  switch (prop_id)
+    {
+    case PROP_LABEL:
+      self->label = g_value_dup_string (value);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+    }
+}
+
+static void
+ostree_blob_reader_pem_get_property (GObject *object, guint prop_id, GValue *value,
+                                     GParamSpec *pspec)
+{
+  OstreeBlobReaderPem *self = OSTREE_BLOB_READER_PEM (object);
+
+  switch (prop_id)
+    {
+    case PROP_LABEL:
+      g_value_set_string (value, self->label);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+    }
+}
+
+static void
+ostree_blob_reader_pem_finalize (GObject *object)
+{
+  OstreeBlobReaderPem *self = OSTREE_BLOB_READER_PEM (object);
+
+  g_free (self->label);
+
+  G_OBJECT_CLASS (_ostree_blob_reader_pem_parent_class)->finalize (object);
+}
+
+static void
+_ostree_blob_reader_pem_class_init (OstreeBlobReaderPemClass *klass)
+{
+  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
+
+  gobject_class->set_property = ostree_blob_reader_pem_set_property;
+  gobject_class->get_property = ostree_blob_reader_pem_get_property;
+  gobject_class->finalize = ostree_blob_reader_pem_finalize;
+
+  /*
+   * OstreeBlobReaderPem:label:
+   *
+   * The label to filter the PEM blocks.
+   */
+  g_object_class_install_property (
+      gobject_class, PROP_LABEL,
+      g_param_spec_string ("label", "", "", "", G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY));
+}
+
+static void
+_ostree_blob_reader_pem_init (OstreeBlobReaderPem *self)
+{
+}
+
+OstreeBlobReaderPem *
+_ostree_blob_reader_pem_new (GInputStream *base, const gchar *label)
+{
+  g_assert (G_IS_INPUT_STREAM (base));
+
+  return g_object_new (OSTREE_TYPE_BLOB_READER_PEM, "base-stream", base, "label", label, NULL);
+}
+
+enum PemInputState
+{
+  PEM_INPUT_STATE_OUTER,
+  PEM_INPUT_STATE_INNER
+};
+
+#define PEM_SUFFIX "-----"
+#define PEM_PREFIX_BEGIN "-----BEGIN "
+#define PEM_PREFIX_END "-----END "
+
+GBytes *
+_ostree_read_pem_block (GDataInputStream *stream, gchar **label, GCancellable *cancellable,
+                        GError **error)
+{
+  enum PemInputState state = PEM_INPUT_STATE_OUTER;
+  g_autofree gchar *tmp_label = NULL;
+  g_autoptr (GString) buf = g_string_new ("");
+
+  while (TRUE)
+    {
+      g_autofree gchar *line = NULL;
+      gsize length;
+
+      line = g_data_input_stream_read_line (stream, &length, cancellable, error);
+      if (!line)
+        break;
+
+      line = g_strstrip (line);
+      if (*line == '\0')
+        continue;
+
+      switch (state)
+        {
+        case PEM_INPUT_STATE_OUTER:
+          if (g_str_has_prefix (line, PEM_PREFIX_BEGIN) && g_str_has_suffix (line, PEM_SUFFIX))
+            {
+              const gchar *start = line + sizeof (PEM_PREFIX_BEGIN) - 1;
+              const gchar *end = g_strrstr (start + 1, PEM_SUFFIX);
+
+              tmp_label = g_strndup (start, end - start);
+              state = PEM_INPUT_STATE_INNER;
+            }
+          break;
+
+        case PEM_INPUT_STATE_INNER:
+          if (g_str_has_prefix (line, PEM_PREFIX_END) && g_str_has_suffix (line, PEM_SUFFIX))
+            {
+              const gchar *start = line + sizeof (PEM_PREFIX_END) - 1;
+              const gchar *end = g_strrstr (start + 1, PEM_SUFFIX);
+
+              if (strncmp (tmp_label, start, end - start) != 0)
+                {
+                  g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_FAILED,
+                                       "Unmatched PEM header");
+                  return NULL;
+                }
+
+              g_base64_decode_inplace (buf->str, &buf->len);
+              GBytes *result = g_bytes_new_take (buf->str, buf->len);
+
+              /* Don't leak the trailing encoded bytes */
+              explicit_bzero (buf->str + buf->len, buf->allocated_len - buf->len);
+              g_string_free (buf, FALSE);
+              buf = NULL;
+
+              if (label)
+                *label = g_steal_pointer (&tmp_label);
+
+              return result;
+            }
+          else
+            g_string_append (buf, line);
+          break;
+
+        default:
+          g_assert_not_reached ();
+        }
+    }
+
+  return NULL;
+}
+
+GBytes *
+ostree_blob_reader_pem_read_blob (OstreeBlobReader *self, GCancellable *cancellable, GError **error)
+{
+  g_autofree gchar *label = NULL;
+  g_autoptr (GBytes) blob = NULL;
+  OstreeBlobReaderPem *pself = OSTREE_BLOB_READER_PEM (self);
+
+  blob = _ostree_read_pem_block (G_DATA_INPUT_STREAM (self), &label, cancellable, error);
+  if (blob != NULL && !g_str_equal (label, pself->label))
+    {
+      g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED, "Unexpected label \"%s\"", label);
+      g_clear_pointer (&blob, g_bytes_unref);
+    }
+  return g_steal_pointer (&blob);
+}

src/libostree/ostree-blob-reader-pem.h

@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2024 Red Hat, Inc.
+ *
+ * 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, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "ostree-blob-reader.h"
+
+G_BEGIN_DECLS
+
+#define OSTREE_TYPE_BLOB_READER_PEM (_ostree_blob_reader_pem_get_type ())
+
+_OSTREE_PUBLIC
+G_DECLARE_FINAL_TYPE (OstreeBlobReaderPem, _ostree_blob_reader_pem, OSTREE, BLOB_READER_PEM,
+                      GDataInputStream);
+
+_OSTREE_PUBLIC
+OstreeBlobReaderPem *_ostree_blob_reader_pem_new (GInputStream *base, const gchar *label);
+
+_OSTREE_PUBLIC
+GBytes *ostree_blob_reader_pem_read_blob (OstreeBlobReader *self, GCancellable *cancellable,
+                                          GError **error);
+
+G_END_DECLS

src/libostree/ostree-blob-reader-private.h

@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2024 Red Hat, Inc.
+ *
+ * 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, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#ifndef __GI_SCANNER__
+
+#include <gio/gio.h>
+
+G_BEGIN_DECLS
+
+GBytes *_ostree_read_pem_block (GDataInputStream *stream, gchar **label, GCancellable *cancellable,
+                                GError **error);
+
+G_END_DECLS
+
+#endif