[PATCH v2] configure: fix out of tree build; check unsafe characters in srcdir

[Tomi Ollila]

While check for GMime session key extraction support... was made
out of tree build compatible, related (and some unrelated) unsafe
characters are now checked in notmuch source directory path.

The known unsafe characters in NOTMUCH_SRCDIR are:

- Single quote (') -- NOTMUCH_SRCDIR='${NOTMUCH_SRCDIR}'
  is written to sh.config in configure line 1328.

- Double quote (") -- configure line 521 *now* writes "$srcdir"
  into generated c source file ($NOTMUCH_SRCDIR includes $srcdir).

- Backslash (\) could also be problematic in configure line 521.

- The added $ and ` are potentially unsafe -- inside double quotes
  in shell script those have special meaning.

  Other characters don't expand inside double quoted strings.
---

V2: added missing \ to the case pattern

 configure | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index 1e7b9f7a..ef81e71b 100755
--- a/configure
+++ b/configure
@@ -26,6 +26,11 @@ readonly DEFAULT_IFS="$IFS"
 srcdir=$(dirname "$0")
 NOTMUCH_SRCDIR=$(cd "$srcdir" && pwd)
 
+case $NOTMUCH_SRCDIR in ( *\'* | *['\"`$']* )
+	echo "Definitely unsafe characters in source path '$NOTMUCH_SRCDIR'".
+	exit 1
+esac
+
 subdirs="util compat lib parse-time-string completion doc emacs"
 subdirs="${subdirs} performance-test test test/test-databases"
 subdirs="${subdirs} bindings"
@@ -513,7 +518,7 @@ int main () {
 
     g_mime_init ();
     parser = g_mime_parser_new ();
-    g_mime_parser_init_with_stream (parser, g_mime_stream_file_open("test/corpora/crypto/basic-encrypted.eml", "r", &error));
+    g_mime_parser_init_with_stream (parser, g_mime_stream_file_open("$srcdir/test/corpora/crypto/basic-encrypted.eml", "r", &error));
     if (error) return !! fprintf (stderr, "failed to instantiate parser with test/corpora/crypto/basic-encrypted.eml\n");
 
     body = GMIME_MULTIPART_ENCRYPTED(g_mime_message_get_mime_part (g_mime_parser_construct_message (parser, NULL)));
@@ -533,7 +538,7 @@ EOF
         printf 'No.\nCould not make tempdir for testing session-key support.\n'
         errors=$((errors + 1))
     elif ${CC} ${CFLAGS} ${gmime_cflags} _check_session_keys.c ${gmime_ldflags} -o _check_session_keys \
-           && GNUPGHOME=${TEMP_GPG} gpg --batch --quiet --import < test/gnupg-secret-key.asc \
+           && GNUPGHOME=${TEMP_GPG} gpg --batch --quiet --import < "$srcdir"/test/gnupg-secret-key.asc \
            && SESSION_KEY=$(GNUPGHOME=${TEMP_GPG} ./_check_session_keys) \
            && [ $SESSION_KEY = 9:0BACD64099D1468AB07C796F0C0AC4851948A658A15B34E803865E9FC635F2F5 ]
     then
-- 
2.21.0