check-hash
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#!/usr/bin/env bash
set -e
# Helper to check a file matches its known hash
# Call it with:
# $1: the path of the file containing all the expected hashes
# $2: the full path to the temporary file that was downloaded, and
# that is to be checked
# $3: the final basename of the file, to which it will be ultimately
# saved as, to be able to match it to the corresponding hashes
# in the .hash file
#
# Exit codes:
# 0: the hash file exists and the file to check matches all its hashes,
# or the hash file does not exist
# 1: unknown command-line option
# 2: the hash file exists and the file to check does not match at least
# one of its hashes
# 3: the hash file exists and there was no hash to check the file against
# 4: the hash file exists and at least one hash type is unknown
while getopts :q OPT; do
case "${OPT}" in
q) exec >/dev/null;;
\?) exit 1;;
esac
done
shift $((OPTIND-1))
h_file="${1}"
file="${2}"
base="${3}"
# Bail early if no hash to check
if [ -z "${h_file}" ]; then
exit 0
fi
# Does the hash-file exist?
if [ ! -f "${h_file}" ]; then
printf "WARNING: no hash file for %s\n" "${base}" >&2
exit 0
fi
# Check one hash for a file
# $1: known hash
# $2: file (full path)
check_one_hash() {
_h="${1}"
_known="${2}"
_file="${3}"
# Note: md5 is supported, but undocumented on purpose.
# Note: sha3 is not supported, since there is currently no implementation
# (the NIST has yet to publish the parameters).
# Note: 'none' means there is explicitly no hash for that file.
case "${_h}" in
none)
return 0
;;
md5|sha1) ;;
sha224|sha256|sha384|sha512) ;;
*) # Unknown hash, exit with error
printf "ERROR: unknown hash '%s' for '%s'\n" \
"${_h}" "${base}" >&2
exit 4
;;
esac
# Do the hashes match?
_hash=$( ${_h}sum "${_file}" |cut -d ' ' -f 1 )
if [ "${_hash}" = "${_known}" ]; then
printf "%s: OK (%s: %s)\n" "${base}" "${_h}" "${_hash}"
return 0
fi
printf "ERROR: %s has wrong %s hash:\n" "${base}" "${_h}" >&2
printf "ERROR: expected: %s\n" "${_known}" >&2
printf "ERROR: got : %s\n" "${_hash}" >&2
printf "ERROR: Incomplete download, or man-in-the-middle (MITM) attack\n" >&2
exit 2
}
# Do we know one or more hashes for that file?
nb_checks=0
while read t h f; do
case "${t}" in
''|'#'*)
# Skip comments and empty lines
continue
;;
*)
if [ "${f}" = "${base}" ]; then
check_one_hash "${t}" "${h}" "${file}"
: $((nb_checks++))
fi
;;
esac
done <"${h_file}"
if [ ${nb_checks} -eq 0 ]; then
case " ${BR_NO_CHECK_HASH_FOR} " in
*" ${base} "*)
# File explicitly has no hash
exit 0
;;
esac
printf "ERROR: No hash found for %s\n" "${base}" >&2
exit 3
fi