B #1481: Avoid downloading complete file on partial download (#1513)

src/datastore_mad/remotes/downloader.sh

@@ -270,8 +270,13 @@ done
 FROM="$1"
 TO="$2"
 
+if [ -n "${HASH_TYPE}" -a -n "${MAX_SIZE}" ]; then
+    echo "Hash check not supported for partial downloads" >&2
+    exit -1
+else
     # File used by the hasher function to store the resulting hash
     export HASH_FILE="/tmp/downloader.hash.$$"
+fi
 
 GLOBAL_CURL_ARGS="--fail -sS -k -L"
 
@@ -335,20 +340,45 @@ if [ -z "${MAX_SIZE}" ]; then
     eval "$command" | \
         tee >( hasher $HASH_TYPE) | \
         decompress "$decompressor" "$TO"
-else
-    # ignore broken pipe
-    trap '' PIPE
-
-    eval "$command" | \
-        tee >( hasher $HASH_TYPE) 2>/dev/null | \
-        decompress "$decompressor" "$TO" 2>/dev/null | \
-        head -c "${MAX_SIZE}"
-fi
 
     if [ "$?" != "0" -o "$PIPESTATUS" != "0" ]; then
         echo "Error copying" >&2
         exit -1
     fi
+else
+    # Order of the 'head' command is here on purpose:
+    # 1. We want to download more bytes than needed to get a requested
+    #    number of bytes on the output. Decompressor may need more
+    #    data to decompress the stream.
+    # 2. Decompressor command is also misused to detect SIGPIPE error.
+    eval "$command" | \
+        decompress "$decompressor" "$TO" 2>/dev/null | \
+        head -c "${MAX_SIZE}"
+
+    # Following table shows exit codes of each command
+    # in the pipe for various scenarios:
+    #
+    # ----------------------------------------------------
+    # | $COMMAND | TYPE          | PIPESTATUS | BEHAVIOUR
+    # ----------------------------------------------------
+    # | cat      | partial       | 141 141  0 | OK
+    # | cat      | full          |   0   0  0 | OK
+    # | cat      | error         |   1   0  0 | fail
+    # | curl     | partial       |  23 141  0 | OK
+    # | curl     | full          |   0   0  0 | OK
+    # | curl     | error         |  22   0  0 | fail
+    # | ssh      | partial       | 255 141  0 | OK
+    # | ssh      | full          |   0   0  0 | OK
+    # | ssh      | error ssh     | 255   0  0 | fail
+    # | ssh      | error ssh cat |   1   0  0 | fail
+    if [ \( "${PIPESTATUS[0]}" != '0' -a "${PIPESTATUS[1]}" = '0' \) \
+         -o \( "${PIPESTATUS[1]}" != '0' -a "${PIPESTATUS[1]}" != '141' \) \
+         -o \( "${PIPESTATUS[2]}" != "0" \) ];
+    then
+        echo "Error copying" >&2
+        exit -1
+    fi
+fi
 
 if [ -n "$HASH_TYPE" ]; then
     HASH_RESULT=$( cat $HASH_FILE)