g10: Fix opening of trust database.

* g10/tdbio.c (tdbio_set_dbname): This function explicitly checks for
the file size, but handled the case of a zero-sized file incorrectly
by returning success.  Fix this by initializing the database in that
case.
* tests/openpgp/Makefile.am (XTESTS): Add new test.
* tests/openpgp/issue2417.scm: New file.

GnuPG-bug-id: 2417
Signed-off-by: Justus Winter <justus@g10code.com>

tests/openpgp/Makefile.am

@@ -84,6 +84,7 @@ XTESTS = \
 	ssh.scm \
 	issue2015.scm \
 	issue2346.scm \
+	issue2417.scm \
 	issue2419.scm
 
 # XXX: Currently, one cannot override automake's 'check' target.  As a

tests/openpgp/issue2417.scm

@@ -0,0 +1,39 @@
+#!/usr/bin/env gpgscm
+
+;; Copyright (C) 2016 g10 Code GmbH
+;;
+;; This file is part of GnuPG.
+;;
+;; GnuPG is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 3 of the License, or
+;; (at your option) any later version.
+;;
+;; GnuPG is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+;;
+;; You should have received a copy of the GNU General Public License
+;; along with this program; if not, see <http://www.gnu.org/licenses/>.
+
+(load (with-path "defs.scm"))
+
+(define (touch file-name)
+  (close (open file-name (logior O_WRONLY O_BINARY O_CREAT) #o600)))
+
+(info "Checking robustness wrt empty databases in gnupghome (issue2417)...")
+
+(lettmp
+ ;; Prepare some random key to import later.
+ (keyfile)
+ (pipe:do
+  (pipe:gpg '(--export alpha))
+  (pipe:write-to keyfile (logior O_WRONLY O_BINARY O_CREAT) #o600))
+
+ (with-temporary-working-directory
+  (setenv "GNUPGHOME" "." #t)
+  (touch "trustdb.gpg")
+  (touch "pubring.gpg")
+  (touch "pubring.kbx")
+  (call-check `(,(tool 'GPG) --import ,keyfile))))