Add sanity test for /etc/lsb-release file in CrOS images

scripts/image_signing/ensure_sane_lsb-release.sh

+#!/bin/bash
+
+# Copyright (c) 2011 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.
+
+# Abort on error.
+set -e
+
+LSB_FILE=/etc/lsb-release
+
+# Load common constants and variables.
+. "$(dirname "$0")/common.sh"
+
+usage() {
+  echo "Usage $PROG image [config]"
+}
+
+# Usage: lsbval path-to-lsb-file key
+# Returns the value for the given lsb-release file variable.
+lsbval() {
+  local lsbfile="$1"
+  local key="$2"
+  grep ^$key= "$lsbfile" | sed s/^$key=//
+}
+
+# Usage: lsbequals path-to-lsb-file key expected-value
+# Returns 0 if they match, 1 otherwise.
+# Also outputs a warning message if they don't match.
+lsbequals() {
+  local lsbfile="$1"
+  local key="$2"
+  local expectval="$3"
+  local realval=$(lsbval "$lsbfile" $key)
+  if [ "$realval" != "$expectval" ]; then
+    echo "$key mismatch. Expected '$expectval', image contains '$realval'"
+    return 1
+  fi
+  return 0
+}
+
+# Usage: check_keyval_in_list lsbfile lsbkey [list of values]
+# Extracts the lsb-release value for the specified key, and confirms it
+# matches one of the whitelisted values specified in value_array.
+# Implementation note:
+# You can't really pass bash arrays to functions. Best you can do is either
+# serialize to string/pass/deserialize (e.g. using whitspace/IFS hacks), or,
+# let the array contents be received as multiple arguments to the target
+# function. We take the latter approach here, hence the shift's to get the
+# first 2 arguments out, before we process the rest of the varargs.

[gauravsh, 2011/02/03 01:12:38]

you could, I guess, also use an eval assuming the 3rd argument is the name of a
list. not sure, if it will be necessarily cleaner, but worth a thought.

+check_keyval_in_list() {
+  local lsbfile="$1"
+  shift
+  local lsbkey="$1"
+  shift
+  local lsbval=$(lsbval "$lsbfile" "$lsbkey")
+  while [ $# -gt 0 ]; do
+    if [ "$lsbval" == "$1" ]; then
+      return 0
+    fi
+    shift
+  done
+  # If we get here, it wasn't found
+  echo "$lsbkey: Value '$lsbval' was not recognized"
+  return 1
+}
+
+# Usage: lsb_syntaxcheck path-to-lsb-file
+# Enforces a number of basic sanity checks on the overall format and contents
+# of the lsb-release file:
+# - Every line is "key=value".
+# - No space after key, no space before value.
+# - key is all A-Z or _, but not starting with _.
+# - value is made up of printable characters, or is empty.
+# - Each line is a reasonable size (<255 bytes).
+# - The whole file is a reasonable size (4kb).
+lsb_syntaxcheck() {
+  local lsbfile="$1"
+  syntaxbad=0
+  # Checks for key being A-Z_, 1 or more characters, not starting with _.
+  # Also checks for = with no spaces on either side.
+  # Checks that the value contains printables (and not starting with space).
+  # Alternatively, the value is permitted to be empty (0 chars) too.
+  badlines=$(grep -Ev '^[A-Z][A-Z_]*=([[:graph:]][[:print:]]*)?$' "$lsbfile")
+  if [ -n "$badlines" ]; then
+    syntaxbad=1
+    echo "$lsbfile: Some lines seem non-well-formed:"
+    echo "$badlines"
+  fi
+
+  # Checks for a lines exceeding a reasonable overall length.
+  badlines=$(grep -E '^.{255}' "$lsbfile")
+  if [ -n "$badlines" ]; then
+    syntaxbad=1
+    echo "$lsbfile: Some lsb-release lines seem unreasonably long:"
+    echo "$badlines"
+  fi
+  # Overall file size check:
+  size=$(ls -sk "$lsbfile" | cut -d ' ' -f 1)
+  if [ $size -gt 4 ]; then
+    syntaxbad=1
+    echo "$lsbfile: This file exceeds 4kb"
+  fi
+  return $syntaxbad
+}
+
+main() {
+  # We want to catch all the discrepancies, not just the first one.
+  # So, any time we find one, we set testfail=1 and continue.
+  # When finished we will use testfail to determine our exit value.
+  local testfail=0
+
+  if [ $# -ne 1 ] && [ $# -ne 2 ]; then
+    usage
+    exit 1
+  fi
+
+  local image="$1"
+
+  # Default config location: same name/directory as this script,
+  # with a .config file extension, ie ensure_sane_lsb-release.config.
+  local configfile="$(dirname "$0")/${0/%.sh/.config}"

[gauravsh, 2011/02/03 01:12:38]

A thought: Since we will only keep the a default config file in here (and not
the actual production config), you could replace this substitution with a file
called ${SCRIPT_DIR}/default_lsb_release.config.

This way the default config data file is not tied to the name of the script
(which makes renaming easier).

+  # Or, maybe a config was provided on the command line.
+  if [ $# -eq 2 ]; then
+    configfile="$2"
+  fi
+  # Either way, load test-expectations data from config.
+  echo -n "Loading config from $configfile... "
+  . "$configfile"
+  echo "Done."
+
+  local rootfs=$(make_temp_dir)
+  mount_image_partition_ro "$image" 3 "$rootfs"
+  local lsb="$rootfs/$LSB_FILE"
+
+  # Basic syntax check first.
+  lsb_syntaxcheck "$lsb" || testfail=1
+
+  lsbequals $lsb CHROMEOS_AUSERVER "$expected_auserver" || testfail=1
+  lsbequals $lsb CHROMEOS_RELEASE_NAME "$expected_release_name" || testfail=1
+  check_keyval_in_list $lsb CHROMEOS_RELEASE_TRACK \
+    "${expected_release_tracks[@]}" || testfail=1
+
+  if check_keyval_in_list $lsb CHROMEOS_RELEASE_BOARD \
+    "${expected_boards[@]}"; then
+    # Pick the right set of test-expectation data to use. The cuts
+    # turn e.g. x86-foo-pvtkeys into x86-foo.
+    local board=$(lsbval $lsb CHROMEOS_RELEASE_BOARD |
+                  cut -d = -f 2 |
+                  cut -d - -f 1,2)
+    # a copy of the board string with '-' squished to variable-name-safe '_'.
+    local boardvar=${board//-/_}
+    eval "expected_appid=\"\$expected_appid_$boardvar\""
+    lsbequals $lsb CHROMEOS_RELEASE_APPID "$expected_appid" || testfail=1
+  else # unrecognized board
+    testfail=1
+  fi
+
+  exit $testfail
+}
+
+main "$@"