[ostree] upgrade: Refuse chronologically older commits unless --allow-downgrade

[Colin Walters <walters src gnome org>]

commit f2e0162846cbb84abf6fd9a38fabdfd588f4eb2f
Author: Colin Walters <walters verbum org>
Date:   Thu Feb 20 18:25:56 2014 -0500

    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                         |    1 +
 src/libostree/ostree-core.c               |    8 ++++
 src/libostree/ostree-core.h               |    1 +
 src/ostree/ot-admin-builtin-upgrade.c     |   40 ++++++++++++++++++++
 tests/libtest.sh                          |   11 ++++++
 tests/test-admin-upgrade-not-backwards.sh |   57 +++++++++++++++++++++++++++++
 6 files changed, 118 insertions(+), 0 deletions(-)
---
diff --git a/Makefile-tests.am b/Makefile-tests.am
index d1a8803..13c5d60 100644
--- a/Makefile-tests.am
+++ b/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 \
diff --git a/src/libostree/ostree-core.c b/src/libostree/ostree-core.c
index 9b7a237..b8fa114 100644
--- a/src/libostree/ostree-core.c
+++ b/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);
+}
diff --git a/src/libostree/ostree-core.h b/src/libostree/ostree-core.h
index bd8e68f..de1698d 100644
--- a/src/libostree/ostree-core.h
+++ b/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
diff --git a/src/ostree/ot-admin-builtin-upgrade.c b/src/ostree/ot-admin-builtin-upgrade.c
index 1b86cdd..9fcae67 100644
--- a/src/ostree/ot-admin-builtin-upgrade.c
+++ b/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()
diff --git a/tests/libtest.sh b/tests/libtest.sh
index da85c1c..7d726a5 100644
--- a/tests/libtest.sh
+++ b/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 ()
diff --git a/tests/test-admin-upgrade-not-backwards.sh b/tests/test-admin-upgrade-not-backwards.sh
new file mode 100644
index 0000000..6ea988b
--- /dev/null
+++ b/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'