signer scripts: use `sudo` if need be when modifying /etc/lsb-release

If we try to run the signing_poller daemon as non-root, it fails to set
the channel.  Detect if the lsb file is writable, and if not, switch to
using sudo on the fly.

BUG=None
TEST=`./signer/signing_poller.py` as non-root and setting the channel works

Change-Id: Iadb10ae68582edfb332f33d3b101c83949ee9502
Reviewed-on: https://gerrit.chromium.org/gerrit/20089
Reviewed-by: Gaurav Shah <gauravsh@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Ready: Mike Frysinger <vapier@chromium.org>

2 files changed, 24 insertions, 11 deletions

diff --git a/scripts/image_signing/set_channel.sh b/scripts/image_signing/set_channel.sh
index 064d737f..bb0927ac 100755
--- a/scripts/image_signing/set_channel.sh
+++ b/scripts/image_signing/set_channel.sh
@@ -1,6 +1,6 @@
 #!/bin/bash
 
-# Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
+# Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
@@ -24,17 +24,23 @@ fi
 main() {
   local image=$1
   local to=$2
-  
+  local rootfs lsb
+
   rootfs=$(make_temp_dir)
+  lsb="${rootfs}/etc/lsb-release"
   mount_image_partition "${image}" 3 "${rootfs}"
   # Get the current channel on the image.
-  local from=$(grep '^CHROMEOS_RELEASE_TRACK=' \
-    "${rootfs}/etc/lsb-release" | cut -d '=' -f 2)
+  local from=$(grep '^CHROMEOS_RELEASE_TRACK=' "${lsb}" | cut -d '=' -f 2)
   from=${from%"-channel"}
   echo "Current channel is '${from}'. Changing to '${to}'."
-  sed -i "s/\b${from}\b/${to}/" "${rootfs}/etc/lsb-release" &&
+
+  local sudo
+  if [[ ! -w ${lsb} ]] ; then
+    sudo="sudo"
+  fi
+  ${sudo} sed -i "s/\b${from}\b/${to}/" "${lsb}" &&
     echo "Channel change successful."
-  cat "${rootfs}/etc/lsb-release"
+  cat "${lsb}"
 }
 
 main "$@"
diff --git a/scripts/image_signing/tag_image.sh b/scripts/image_signing/tag_image.sh
index aa19871c..0059f931 100755
--- a/scripts/image_signing/tag_image.sh
+++ b/scripts/image_signing/tag_image.sh
@@ -1,6 +1,6 @@
 #!/bin/bash
 
-# Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+# Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
@@ -173,22 +173,29 @@ process_all_tags() {
 process_all_lsb_mods() {
   local rootfs="$1"
   local do_modifications="$2"
+  local lsb="${rootfs}/etc/lsb-release"
+  local sudo
+
+  if [ ! -w "${lsb}" ]; then
+    sudo="sudo"
+  fi
+
   if [ ${FLAGS_remove_test_label} = ${FLAGS_TRUE} ]; then
-    if grep -wq "test" ${rootfs}/etc/lsb-release; then
+    if grep -wq "test" "${lsb}"; then
       g_modified=${FLAGS_TRUE}
     fi
     if [ ${do_modifications} = ${FLAGS_TRUE} ]; then
-      sed -i 's/\btest\b//' "${rootfs}/etc/lsb-release" &&
+      ${sudo} sed -i 's/\btest\b//' "${lsb}" &&
         echo "Test Label removed from /etc/lsb-release"
     fi
   fi
 
   if [ ${FLAGS_change_dev_to_beta} = ${FLAGS_TRUE} ]; then
-    if grep -wq "dev" ${rootfs}/etc/lsb-release; then
+    if grep -wq "dev" "${lsb}"; then
       g_modified=${FLAGS_TRUE}
     fi
     if [ ${do_modifications} = ${FLAGS_TRUE} ]; then
-      sed -i 's/\bdev\b/beta/' "${rootfs}/etc/lsb-release" &&
+      ${sudo} sed -i 's/\bdev\b/beta/' "${lsb}" &&
         echo "Dev Channel Label was changed to Beta"
     fi
   fi