Fix Veracrypt compatible support for longer passphrases.

Previous fix for longer passhphrases increased maximal
passphrase length even if it was not needed, for example
if used with SHA256 hash in combination with keyfiles.

This patch tries to fix the problem, so some older volumes
can be opened again.

Also some test images are added for regression testing.

Fixes: #542.

lib/tcrypt/tcrypt.c

@@ -535,13 +535,11 @@ static int TCRYPT_init_hdr(struct crypt_device *cd,
 	if (posix_memalign((void*)&key, crypt_getpagesize(), TCRYPT_HDR_KEY_LEN))
 		return -ENOMEM;
 
-	if (params->flags & CRYPT_TCRYPT_VERA_MODES) {
-		max_passphrase_size = VCRYPT_KEY_POOL_LEN;
+	if (params->flags & CRYPT_TCRYPT_VERA_MODES &&
+	    params->passphrase_size > TCRYPT_KEY_POOL_LEN) {
 		/* Really. Keyfile pool length depends on passphrase size in Veracrypt. */
-		if (params->passphrase_size > TCRYPT_KEY_POOL_LEN)
+		max_passphrase_size = VCRYPT_KEY_POOL_LEN;
 		keyfiles_pool_length = VCRYPT_KEY_POOL_LEN;
-		else
-			keyfiles_pool_length = TCRYPT_KEY_POOL_LEN;
 	} else {
 		max_passphrase_size = TCRYPT_KEY_POOL_LEN;
 		keyfiles_pool_length = TCRYPT_KEY_POOL_LEN;

tests/tcrypt-compat-test

@@ -8,6 +8,7 @@ TST_DIR=tcrypt-images
 MAP=tctst
 PASSWORD="aaaaaaaaaaaa"
 PASSWORD_HIDDEN="bbbbbbbbbbbb"
+PASSWORD_72C="aaaaaaaaaaaabbbbbbbbbbbbccccccccccccddddddddddddeeeeeeeeeeeeffffffffffff"
 PIM=1234
 
 [ -z "$srcdir" ] && srcdir="."
@@ -123,7 +124,10 @@ done
 echo "HEADER KEYFILES CHECK"
 for file in $(ls $TST_DIR/[tv]ck_*) ; do
 	echo -n " $file"
-	echo $PASSWORD | $CRYPTSETUP tcryptDump --veracrypt -d $TST_DIR/keyfile1 -d $TST_DIR/keyfile2 $file >/dev/null || fail
+	PWD=$PASSWORD
+	[[ $file =~ vck_1_nopw.* ]] && PWD=""
+	[[ $file =~ vck_1_pw72.* ]] && PWD=$PASSWORD_72C
+	echo $PWD | $CRYPTSETUP tcryptDump --veracrypt -d $TST_DIR/keyfile1 -d $TST_DIR/keyfile2 $file >/dev/null || fail
 	echo " [OK]"
 done