pkg-download: verify the hashes from the download wrapper

Instead of repeating the check in our download rules, delegate the check
of the hashes to the download wrapper.

This needs three different changes:

  - add a new argument to the download wrapper, that is the full path to
    the hash file; if the hash file does not exist, that does not change
    the current behaviour, as the existence of the hash file is checked
    for in the check-hash script;

  - add a third argument to the check-hash script, to be the basename of
    the file to check; this is required because we no longer check the
    final file with the final filename, but an intermediate file with a
    temporary filename;

  - do the actual call to the check-hash script from within the download
    wrapper.

This further paves the way to doing pre-download checks of the hashes
for the locally cached files.

Note: this patch removes the check for hashes for already downloaded
files, since the wrapper script exits early. The behaviour to check
localy cached files will be restored and enhanced in the following
patch.

[Thomas: fix minor typo in comment.]

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Peter Korsgaard <jacmet@uclibc.org>
Cc: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

2 files changed, 29 insertions, 9 deletions

diff --git a/support/download/check-hash b/support/download/check-hash
index 13e361afc..b59fd2a22 100755
--- a/support/download/check-hash
+++ b/support/download/check-hash
@@ -4,10 +4,15 @@ set -e
 # Helper to check a file matches its known hash
 # Call it with:
 #   $1: the path of the file containing all the the expected hashes
-#   $2: the full path to the file to check
+#   $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
 
 h_file="${1}"
 file="${2}"
+base="${3}"
 
 # Does the hash-file exist?
 if [ ! -f "${h_file}" ]; then
@@ -30,7 +35,7 @@ check_one_hash() {
         sha224|sha256|sha384|sha512)    ;;
         *) # Unknown hash, exit with error
             printf "ERROR: unknown hash '%s' for '%s'\n"  \
-                   "${_h}" "${_file##*/}" >&2
+                   "${_h}" "${base}" >&2
             exit 1
             ;;
     esac
@@ -38,11 +43,11 @@ check_one_hash() {
     # Do the hashes match?
     _hash=$( ${_h}sum "${_file}" |cut -d ' ' -f 1 )
     if [ "${_hash}" = "${_known}" ]; then
-        printf "%s: OK (%s: %s)\n" "${_file##*/}" "${_h}" "${_hash}"
+        printf "%s: OK (%s: %s)\n" "${base}" "${_h}" "${_hash}"
         return 0
     fi
 
-    printf "ERROR: %s has wrong %s hash:\n" "${_file##*/}" "${_h}" >&2
+    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
@@ -59,7 +64,7 @@ while read t h f; do
             continue
             ;;
         *)
-            if [ "${f}" = "${file##*/}" ]; then
+            if [ "${f}" = "${base}" ]; then
                 check_one_hash "${t}" "${h}" "${file}"
                 : $((nb_checks++))
             fi
@@ -69,9 +74,9 @@ done <"${h_file}"
 
 if [ ${nb_checks} -eq 0 ]; then
     if [ -n "${BR2_ENFORCE_CHECK_HASH}" ]; then
-        printf "ERROR: No hash found for %s\n" "${file}" >&2
+        printf "ERROR: No hash found for %s\n" "${base}" >&2
         exit 1
     else
-        printf "WARNING: No hash found for %s\n" "${file}" >&2
+        printf "WARNING: No hash found for %s\n" "${base}" >&2
     fi
 fi
diff --git a/support/download/dl-wrapper b/support/download/dl-wrapper
index dc5b4b08d..f0cdd735b 100755
--- a/support/download/dl-wrapper
+++ b/support/download/dl-wrapper
@@ -21,14 +21,15 @@ set -e
 
 main() {
     local OPT OPTARG
-    local backend output
+    local backend output hfile
 
     # Parse our options; anything after '--' is for the backend
-    while getopts :hb:o: OPT; do
+    while getopts :hb:o:H: OPT; do
         case "${OPT}" in
         h)  help; exit 0;;
         b)  backend="${OPTARG}";;
         o)  output="${OPTARG}";;
+        H)  hfile="${OPTARG}";;
         :)  error "option '%s' expects a mandatory argument\n" "${OPTARG}";;
         \?) error "unknown option '%s'\n" "${OPTARG}";;
         esac
@@ -42,6 +43,9 @@ main() {
     if [ -z "${output}" ]; then
         error "no output specified, use -o\n"
     fi
+    if [ -z "${hfile}" ]; then
+        error "no hash-file specified, use -H\n"
+    fi
 
     # If the output file already exists, do not download it again
     if [ -e "${output}" ]; then
@@ -75,6 +79,13 @@ main() {
     # cd back to free the temp-dir, so we can remove it later
     cd "${OLDPWD}"
 
+    # Check if the downloaded file is sane, and matches the stored hashes
+    # for that file
+    if ! support/download/check-hash "${hfile}" "${tmpf}" "${output##*/}"; then
+        rm -rf "${tmpd}"
+        exit 1
+    fi
+
     # tmp_output is in the same directory as the final output, so we can
     # later move it atomically.
     tmp_output="$(mktemp "${output}.XXXXXX")"
@@ -150,6 +161,10 @@ DESCRIPTION
     -o FILE
         Store the downloaded archive in FILE.
 
+    -H FILE
+        Use FILE to read hashes from, and check them against the downloaded
+        archive.
+
   Exit status:
     0   if OK
     !0  in case of error