[Libguestfs] [nbdkit PATCH 3/3] tlsdummy: New filter

[Eric Blake]

On 8/7/20 5:00 PM, Eric Blake wrote:
> Take advantage of the fact that we can now detect the type of client
> during --tls=on in order to provide safe dummy content for plaintext
> clients without having to rewrite plugins to do so.
> 
> Signed-off-by: Eric Blake <eblake at redhat.com>
> ---

I got a test working (although it still shows that we are bit awkward 
until nbdkit makes it easier for filters to skip calling next_open when 
it wants to)

diff --git c/tests/Makefile.am i/tests/Makefile.am
index b5ef96a7..dd756723 100644
--- c/tests/Makefile.am
+++ i/tests/Makefile.am
@@ -1501,6 +1501,10 @@ EXTRA_DIST += \
  	test-truncate-extents.sh \
  	$(NULL)

+# tlsdummy filter test.
+TESTS += test-tlsdummy.sh
+EXTRA_DIST += test-tlsdummy.sh
+
  # xz filter test.
  LIBGUESTFS_TESTS += test-xz

diff --git c/tests/test-tlsdummy.sh i/tests/test-tlsdummy.sh
new file mode 100755
index 00000000..40c29602
--- /dev/null
+++ i/tests/test-tlsdummy.sh
@@ -0,0 +1,98 @@
+#!/usr/bin/env bash
+# nbdkit
+# Copyright (C) 2019-2020 Red Hat Inc.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+# * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution.
+#
+# * Neither the name of Red Hat nor the names of its contributors may be
+# used to endorse or promote products derived from this software without
+# specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+
+source ./functions.sh
+set -e
+set -x
+
+requires nbdsh -c 'exit (not h.supports_tls ())'
+
+# Does the nbdkit binary support TLS?
+if ! nbdkit --dump-config | grep -sq tls=yes; then
+    echo "$0: nbdkit built without TLS support"
+    exit 77
+fi
+
+# Did we create the PSK keys file?
+# Probably 'certtool' is missing.
+if [ ! -s keys.psk ]; then
+    echo "$0: PSK keys file was not created by the test harness"
+    exit 77
+fi
+
+export sock=`mktemp -u`
+pid="tlsdummy.pid"
+
+files="$sock $pid"
+rm -f $files
+cleanup_fn rm -f $files
+
+# Run dual-mode server
+start_nbdkit -P $pid -U $sock --tls=on --tls-psk=keys.psk \
+    --filter=tlsdummy sh - tlsreadme=$'dummy\n' <<\EOF
+if test "$2" = insecure; then
+    echo 'EINVAL insecure handle' 2>&1; exit 1
+fi
+case $1 in
+  list_exports) echo NAMES; echo hello; echo world ;;
+  open) if test "$4" != true; then
+      # nbdkit needs a fix to let tlsdummy skip .open when insecure...
+      # echo 'EINVAL unexpected tls mode' 2>&1; exit 1
+      echo insecure; exit 0
+    fi
+    echo $3 ;;
+  get_size) echo 6 ;;
+  pread) echo "$2" | dd skip=$4 count=$3 iflag=skip_bytes,count_bytes ;;
+  *) exit 2;
+esac
+EOF
+
+# Plaintext client sees only dummy volume
+nbdsh -c '
+import os
+h.set_export_name ("hello")
+h.connect_unix (os.environ["sock"])
+assert h.get_size () == 512
+assert h.pread (5, 0) == b"dummy"
+'
+
+# Encrypted client sees desired volumes
+nbdsh -c '
+import os
+h.set_export_name ("hello")
+h.set_tls (nbd.TLS_REQUIRE)
+h.set_tls_psk_file ("keys.psk")
+h.set_tls_username ("qemu")
+h.connect_unix (os.environ["sock"])
+assert h.get_size () == 6
+assert h.pread (5, 0) == b"hello"
+'


-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org