Add --null flag to qubesd-query

This allows avoiding a spurious call to printf(1).
QubesOS · Dec 20, 2022 · f8835ea · f8835ea
1 parent dd058ec
commit f8835ea
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Showing 4 changed files with 25 additions and 8 deletions.
diff --git a/doc/manpages/qubesd-query.rst b/doc/manpages/qubesd-query.rst
@@ -44,6 +44,11 @@ Options
    is not passed, and 1024 otherwise.  This option can be used to lower this
    value, though not raise it.
 
+.. option:: --null
+
+   bash's ``read -r -d ''`` expects that the string being read is terminated by
+   NUL byte.  This option causes qubesd-query to add one to qubesd's response.
+
 Description
 -----------
 

diff --git a/qubes-rpc/admin.vm.volume.Import b/qubes-rpc/admin.vm.volume.Import
@@ -45,14 +45,11 @@ admin.vm.volume.Import) flags=(--empty);;
 *) printf 'Invoked with unknown basename %q, cannot continue\n' "${0##*/}" >&2; exit 1;;
 esac
 
-{
-    qubesd-query "${flags[@]}" -c /var/run/qubesd.internal.sock \
-        "$QREXEC_REMOTE_DOMAIN" \
-        "internal.vm.volume.ImportBegin" \
-        "$QREXEC_REQUESTED_TARGET" \
-        "$1"
-    printf \\0
-} >"$tmpfile"
+qubesd-query --null "${flags[@]}" -c /var/run/qubesd.internal.sock \
+    "$QREXEC_REMOTE_DOMAIN" \
+    "internal.vm.volume.ImportBegin" \
+    "$QREXEC_REQUESTED_TARGET" \
+    "$1" >"$tmpfile"
 
 {
     # Read response from qubesd

diff --git a/qubes/tests/rpc_import.py b/qubes/tests/rpc_import.py
@@ -39,6 +39,13 @@ class TestRpcImport(qubes.tests.QubesTestCase):
 
     QUBESD_QUERY = '''\
 #!/bin/sh -e
+unset null
+null=false
+
+if [ "$1" = --null ]; then
+   shift
+   null=true
+fi
 
 if [ "$1" = --single-line ] && [ "$2" = --max-bytes=21 ]; then
     shift 2
@@ -54,6 +61,7 @@ class TestRpcImport(qubes.tests.QubesTestCase):
 fi
 echo "$@" > "command-$method"
 cat -- "response-$method"
+if [ "$null" = true ]; then printf '\\0'; fi
 '''
 
     RPC_FILE_PATH = os.path.abspath(os.path.join(

diff --git a/qubes/tools/qubesd_query.py b/qubes/tools/qubesd_query.py
@@ -45,6 +45,11 @@
     action='store_true',
     default=False,
     help='Only read a single line of input')
+parser.add_argument('--null',
+    dest='null',
+    action='store_true',
+    default=False,
+    help="Print an extra NUL byte; useful for shell scripts")
 
 def sighandler(loop, signame, coro):
     print('caught {}, exiting'.format(signame))
@@ -157,6 +162,8 @@ def main(args=None):
 
     if args.fail:
         return returncode
+    if args.null:
+        sys.stdout.buffer.write(b'\0')
     return 0
 
 if __name__ == '__main__':