upgrade: Refuse chronologically older commits unless --allow-downgrade

We don't want to allow MITM attackers to intercept upgrade requests
and provide clients with older OS versions vulnerable to security
flaws.

Only "ostree admin upgrade" gets this behavior for now - whether we
want to do it for "ostree admin switch" is another question.

Makefile-tests.am

@@ -37,6 +37,7 @@ testfiles = test-basic \
 	test-admin-deploy-switch \
 	test-admin-deploy-etcmerge-cornercases \
 	test-admin-deploy-uboot \
+	test-admin-upgrade-not-backwards \
 	test-setuid \
 	test-delta \
 	test-xattrs \

src/libostree/ostree-core.c

@@ -1755,3 +1755,11 @@ ostree_commit_get_parent (GVariant  *commit_variant)
     return NULL;
   return ostree_checksum_from_bytes_v (bytes);
 }
+
+guint64
+ostree_commit_get_timestamp (GVariant  *commit_variant)
+{
+  guint64 ret;
+  g_variant_get_child (commit_variant, 5, "t", &ret);
+  return GUINT64_FROM_BE (ret);
+}

src/libostree/ostree-core.h

@@ -250,5 +250,6 @@ gboolean ostree_validate_structureof_dirmeta (GVariant      *dirmeta,
                                               GError       **error);
 
 gchar *  ostree_commit_get_parent            (GVariant  *commit_variant);
+guint64  ostree_commit_get_timestamp         (GVariant  *commit_variant);
 
 G_END_DECLS

src/ostree/ot-admin-builtin-upgrade.c

@@ -34,11 +34,13 @@
 #include <glib/gi18n.h>
 
 static gboolean opt_reboot;
+static gboolean opt_allow_downgrade;
 static char *opt_osname;
 
 static GOptionEntry options[] = {
   { "os", 0, 0, G_OPTION_ARG_STRING, &opt_osname, "Specify operating system root to use", NULL },
   { "reboot", 'r', 0, G_OPTION_ARG_NONE, &opt_reboot, "Reboot after a successful upgrade", NULL },
+  { "allow-downgrade", 0, 0, G_OPTION_ARG_NONE, &opt_allow_downgrade, "Permit deployment of chronologically older trees", NULL },
   { NULL }
 };
 
@@ -109,6 +111,44 @@ ot_admin_builtin_upgrade (int argc, char **argv, OstreeSysroot *sysroot, GCancel
   else
     {
       gs_unref_object GFile *real_sysroot = g_file_new_for_path ("/");
+
+      if (!opt_allow_downgrade)
+        {
+          const char *old_revision = ostree_deployment_get_csum (merge_deployment);
+          gs_unref_variant GVariant *old_commit = NULL;
+          gs_unref_variant GVariant *new_commit = NULL;
+
+          if (!ostree_repo_load_variant (repo, OSTREE_OBJECT_TYPE_COMMIT,
+                                         old_revision,
+                                         &old_commit,
+                                         error))
+            goto out;
+          
+          if (!ostree_repo_load_variant (repo, OSTREE_OBJECT_TYPE_COMMIT,
+                                         new_revision, &new_commit,
+                                         error))
+            goto out;
+
+          if (ostree_commit_get_timestamp (old_commit) > ostree_commit_get_timestamp (new_commit))
+            {
+              GDateTime *old_ts = g_date_time_new_from_unix_utc (ostree_commit_get_timestamp (old_commit));
+              GDateTime *new_ts = g_date_time_new_from_unix_utc (ostree_commit_get_timestamp (new_commit));
+              gs_free char *old_ts_str = NULL;
+              gs_free char *new_ts_str = NULL;
+
+              g_assert (old_ts);
+              g_assert (new_ts);
+              old_ts_str = g_date_time_format (old_ts, "%c");
+              new_ts_str = g_date_time_format (new_ts, "%c");
+              g_date_time_unref (old_ts);
+              g_date_time_unref (new_ts);
+
+              g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
+                           "Upgrade target revision '%s' with timestamp '%s' is chronologically older than current revision '%s' with timestamp '%s'; use --allow-downgrade to permit",
+                           new_revision, new_ts_str, old_revision, old_ts_str);
+              goto out;
+            }
+        }
       
       /* Here we perform cleanup of any leftover data from previous
        * partial failures.  This avoids having to call gs_shutil_rm_rf()

tests/libtest.sh

@@ -223,6 +223,8 @@ EOF
 
     ostree --repo=${test_tmpdir}/testos-repo commit -b testos/buildmaster/x86_64-runtime -s "Build"
     
+    # Ensure these commits have distinct second timestamps
+    sleep 2
     echo "a new executable" > usr/bin/sh
     ostree --repo=${test_tmpdir}/testos-repo commit -b testos/buildmaster/x86_64-runtime -s "Build"
 
@@ -248,6 +250,15 @@ EOF
 	    setup_os_boot_uboot
             ;;
     esac
+    
+    cd ${test_tmpdir}
+    mkdir ${test_tmpdir}/httpd
+    cd httpd
+    ln -s ${test_tmpdir} ostree
+    ostree trivial-httpd --daemonize -p ${test_tmpdir}/httpd-port $args
+    port=$(cat ${test_tmpdir}/httpd-port)
+    echo "http://127.0.0.1:${port}" > ${test_tmpdir}/httpd-address
+    cd ${oldpwd} 
 }
 
 os_repository_new_commit ()

tests/test-admin-upgrade-not-backwards.sh

@@ -0,0 +1,57 @@
+#!/bin/bash
+#
+# Copyright (C) 2014 Colin Walters <walters@verbum.org>
+#
+# 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.
+
+set -e
+
+. $(dirname $0)/libtest.sh
+
+echo "1..1"
+
+setup_os_repository "archive-z2" "syslinux"
+
+echo "ok setup"
+
+echo "1..2"
+
+cd ${test_tmpdir}
+ostree --repo=sysroot/ostree/repo remote add --set=gpg-verify=false testos $(cat httpd-address)/ostree/testos-repo
+ostree --repo=sysroot/ostree/repo pull testos testos/buildmaster/x86_64-runtime
+rev=$(ostree --repo=sysroot/ostree/repo rev-parse testos/buildmaster/x86_64-runtime)
+export rev
+echo "rev=${rev}"
+# This initial deployment gets kicked off with some kernel arguments 
+ostree admin --sysroot=sysroot deploy --karg=root=LABEL=MOO --karg=quiet --os=testos testos:testos/buildmaster/x86_64-runtime
+assert_has_dir sysroot/boot/ostree/testos-${bootcsum}
+
+# This should be a no-op
+ostree admin --sysroot=sysroot upgrade --os=testos
+
+# Now reset to an older revision
+ostree --repo=${test_tmpdir}/testos-repo reset testos/buildmaster/x86_64-runtime{,^}
+
+if ostree admin --sysroot=sysroot upgrade --os=testos 2>upgrade-err.txt; then
+    assert_not_reached 'upgrade unexpectedly succeeded'
+fi
+assert_file_has_content upgrade-err.txt 'chronologically older'
+
+echo 'ok upgrade will not go backwards'
+
+ostree admin --sysroot=sysroot upgrade --os=testos --allow-downgrade
+
+echo 'ok upgrade backwards'