Move change key into library (add crypt_keyslot_change_by_passphrase).

This change is useful mainly in FIPS mode, where we cannot
extract volume key directly from libcryptsetup.

TODO

@@ -1,7 +1,4 @@
 Version 1.6.0:
 - Export wipe device functions
 - Support K/M suffixes for align payload (new switch?).
-- FIPS: move changekey to library
-- online reencryption api?
-- integrate more metadata formats
 - TRIM for keyslots

lib/libcryptsetup.h

@@ -598,6 +598,33 @@ int crypt_keyslot_add_by_passphrase(struct crypt_device *cd,
 	const char *new_passphrase,
 	size_t new_passphrase_size);
 
+/**
+ * Change defined key slot using provided passphrase
+ *
+ * @pre @e cd contains initialized and formatted LUKS device context
+ *
+ * @param cd crypt device handle
+ * @param keyslot_old old keyslot or @e CRYPT_ANY_SLOT
+ * @param keyslot_new new keyslot (can be the same as old)
+ * @param passphrase passphrase used to unlock volume key, @e NULL for query
+ * @param passphrase_size size of passphrase (binary data)
+ * @param new_passphrase passphrase for new keyslot, @e NULL for query
+ * @param new_passphrase_size size of @e new_passphrase (binary data)
+ *
+ * @return allocated key slot number or negative errno otherwise.
+ *
+ * @note This function is just internal implementation of luksChange
+ * command to avoid reading of volume key outside libcryptsetup boundary
+ * in FIPS mode.
+ */
+int crypt_keyslot_change_by_passphrase(struct crypt_device *cd,
+	int keyslot_old,
+	int keyslot_new,
+	const char *passphrase,
+	size_t passphrase_size,
+	const char *new_passphrase,
+	size_t new_passphrase_size);
+
 /**
 * Add key slot using provided key file path
  *

lib/libcryptsetup.sym

@@ -26,6 +26,7 @@ CRYPTSETUP_1.0 {
 		crypt_free;
 
 		crypt_keyslot_add_by_passphrase;
+		crypt_keyslot_change_by_passphrase;
 		crypt_keyslot_add_by_keyfile;
 		crypt_keyslot_add_by_keyfile_offset;
 		crypt_keyslot_add_by_volume_key;

lib/setup.c

@@ -1649,6 +1649,67 @@ out:
 	return r ?: keyslot;
 }
 
+int crypt_keyslot_change_by_passphrase(struct crypt_device *cd,
+	int keyslot_old,
+	int keyslot_new,
+	const char *passphrase,
+	size_t passphrase_size,
+	const char *new_passphrase,
+	size_t new_passphrase_size)
+{
+	struct volume_key *vk = NULL;
+	int r = -EINVAL;
+
+	log_dbg("Changing passphrase from old keyslot %d to new %d.",
+		keyslot_old, keyslot_new);
+
+	if (!isLUKS(cd->type)) {
+		log_err(cd, _("This operation is supported only for LUKS device.\n"));
+		return -EINVAL;
+	}
+
+	r = LUKS_open_key_with_hdr(keyslot_old, passphrase, passphrase_size,
+				   &cd->u.luks1.hdr, &vk, cd);
+	if (r < 0)
+		return r;
+
+	if (keyslot_old != CRYPT_ANY_SLOT && keyslot_old != r) {
+		log_dbg("Keyslot mismatch.");
+		goto out;
+	}
+	keyslot_old = r;
+
+	if (keyslot_new == CRYPT_ANY_SLOT) {
+		keyslot_new = LUKS_keyslot_find_empty(&cd->u.luks1.hdr);
+		if (keyslot_new < 0)
+			keyslot_new = keyslot_old;
+	}
+
+	if (keyslot_old == keyslot_new) {
+		log_dbg("Key slot %d is going to be overwritten.", keyslot_old);
+		(void)crypt_keyslot_destroy(cd, keyslot_old);
+	}
+
+	r = LUKS_set_key(keyslot_new, new_passphrase, new_passphrase_size,
+			 &cd->u.luks1.hdr, vk, cd->iteration_time,
+			 &cd->u.luks1.PBKDF2_per_sec, cd);
+
+	if (keyslot_old == keyslot_new) {
+		if (r >= 0)
+			log_verbose(cd, _("Key slot %d changed.\n"), r);
+	} else {
+		if (r >= 0) {
+			log_verbose(cd, _("Replaced with key slot %d.\n"), r);
+			r = crypt_keyslot_destroy(cd, keyslot_old);
+		}
+	}
+	if (r < 0)
+		log_err(cd, _("Failed to swap new key slot.\n"));
+out:
+	crypt_free_volume_key(vk);
+	return r ?: keyslot_new;
+}
+
 int crypt_keyslot_add_by_keyfile_offset(struct crypt_device *cd,
 	int keyslot,
 	const char *keyfile,

src/cryptsetup.c

@@ -909,24 +909,13 @@ out:
 	return r;
 }
 
-static int _slots_full(struct crypt_device *cd)
-{
-	int i;
-
-	for (i = 0; i < crypt_keyslot_max(crypt_get_type(cd)); i++)
-		if (crypt_keyslot_status(cd, i) == CRYPT_SLOT_INACTIVE)
-			return 0;
-	return 1;
-}
-
 static int action_luksChangeKey(void)
 {
 	const char *opt_new_key_file = (action_argc > 1 ? action_argv[1] : NULL);
 	struct crypt_device *cd = NULL;
-	char *vk = NULL, *password = NULL;
-	size_t passwordLen = 0;
-	size_t vk_size;
-	int new_key_slot, old_key_slot, r;
+	char *password = NULL, *password_new = NULL;
+	size_t password_size = 0, password_new_size = 0;
+	int r;
 
 	if ((r = crypt_init(&cd, uuid_or_device(action_argv[0]))))
 		goto out;
@@ -938,71 +927,31 @@ static int action_luksChangeKey(void)
 		crypt_set_iteration_time(cd, opt_iteration_time);
 
 	r = crypt_get_key(_("Enter LUKS passphrase to be changed: "),
-		      &password, &passwordLen,
+		      &password, &password_size,
 		      opt_keyfile_offset, opt_keyfile_size, opt_key_file,
 		      opt_timeout, _verify_passphrase(0), cd);
 	if (r < 0)
 		goto out;
 
-	vk_size = crypt_get_volume_key_size(cd);
-	vk = crypt_safe_alloc(vk_size);
-	if (!vk) {
-		r = -ENOMEM;
+	/* Check password before asking for new one */
+	r = crypt_activate_by_passphrase(cd, NULL, opt_key_slot,
+					 password, password_size, 0);
+	if (r < 0)
 		goto out;
-	}
 
-	r = crypt_volume_key_get(cd, opt_key_slot, vk, &vk_size,
-				 password, passwordLen);
-	if (r < 0) {
-		if (opt_key_slot != CRYPT_ANY_SLOT)
-			log_err(_("No key available with this passphrase.\n"));
-		goto out;
-	}
-
-	if (opt_key_slot != CRYPT_ANY_SLOT || _slots_full(cd)) {
-		log_dbg("Key slot %d is going to be overwritten (%s).",
-			r, opt_key_slot != CRYPT_ANY_SLOT ?
-			"explicit key slot specified" : "no free key slot");
-		old_key_slot = r;
-		new_key_slot = r;
-	} else {
-		log_dbg("Allocating new key slot.");
-		old_key_slot = r;
-		new_key_slot = CRYPT_ANY_SLOT;
-	}
-
-	crypt_safe_free(password);
-	password = NULL;
-	passwordLen = 0;
 	r = crypt_get_key(_("Enter new LUKS passphrase: "),
-			  &password, &passwordLen,
+			  &password_new, &password_new_size,
 			  opt_new_keyfile_offset, opt_new_keyfile_size,
 			  opt_new_key_file,
 			  opt_timeout, _verify_passphrase(0), cd);
 	if (r < 0)
 		goto out;
 
-	if (new_key_slot == old_key_slot) {
-		(void)crypt_keyslot_destroy(cd, old_key_slot);
-		r = crypt_keyslot_add_by_volume_key(cd, new_key_slot,
-						    vk, vk_size,
-						    password, passwordLen);
-		if (r >= 0)
-			log_verbose(_("Key slot %d changed.\n"), r);
-	} else {
-		r = crypt_keyslot_add_by_volume_key(cd, CRYPT_ANY_SLOT,
-						    vk, vk_size,
-						    password, passwordLen);
-		if (r >= 0) {
-			log_verbose(_("Replaced with key slot %d.\n"), r);
-			r = crypt_keyslot_destroy(cd, old_key_slot);
-		}
-	}
-	if (r < 0)
-		log_err(_("Failed to swap new key slot.\n"));
+	r = crypt_keyslot_change_by_passphrase(cd, opt_key_slot, opt_key_slot,
+		password, password_size, password_new, password_new_size);
 out:
-	crypt_safe_free(vk);
 	crypt_safe_free(password);
+	crypt_safe_free(password_new);
 	crypt_free(cd);
 	return r;
 }