1 files changed, 113 insertions, 0 deletions
diff --git a/src/knot/modules/onlinesign/nsec_next.c b/src/knot/modules/onlinesign/nsec_next.c
new file mode 100644
index 0000000..2205f6b
--- /dev/null
+++ b/src/knot/modules/onlinesign/nsec_next.c
@@ -0,0 +1,113 @@
+/*  Copyright (C) 2019 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program 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.
+
+    This program 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 <https://www.gnu.org/licenses/>.
+ */
+
+#include <assert.h>
+#include <stdbool.h>
+#include <stdlib.h>
+
+#include "knot/modules/onlinesign/nsec_next.h"
+#include "libknot/libknot.h"
+
+static bool inc_label(const uint8_t *buffer, uint8_t **label_ptr)
+{
+	assert(buffer);
+	assert(label_ptr && *label_ptr);
+	assert(buffer <= *label_ptr && *label_ptr < buffer + KNOT_DNAME_MAXLEN);
+
+	const uint8_t *label = *label_ptr;
+	const uint8_t len    = *label;
+	const uint8_t *first = *label_ptr + 1;
+	const uint8_t *last  = *label_ptr + len;
+
+	assert(len <= KNOT_DNAME_MAXLABELLEN);
+
+	// jump over trailing 0xff chars
+	uint8_t *scan = (uint8_t *)last;
+	while (scan >= first && *scan == 0xff) {
+		scan -= 1;
+	}
+
+	// increase in place
+	if (scan >= first) {
+		if (*scan == 'A' - 1) {
+			*scan = 'Z' + 1;
+		} else {
+			*scan += 1;
+		}
+		memset(scan + 1, 0x00, last - scan);
+		return true;
+	}
+
+	// check name and label boundaries
+	if (scan - 1 < buffer || len == KNOT_DNAME_MAXLABELLEN) {
+		return false;
+	}
+
+	// append a zero byte at the end of the label
+	scan -= 1;
+	scan[0] = len + 1;
+	memmove(scan + 1, first, len);
+	scan[len + 1] = 0x00;
+
+	*label_ptr = scan;
+
+	return true;
+}
+
+static void strip_label(uint8_t **name_ptr)
+{
+	assert(name_ptr && *name_ptr);
+
+	uint8_t len = **name_ptr;
+	*name_ptr += 1 + len;
+}
+
+knot_dname_t *online_nsec_next(const knot_dname_t *dname, const knot_dname_t *apex)
+{
+	assert(dname);
+	assert(apex);
+
+	// right aligned copy of the domain name
+	knot_dname_storage_t copy = { 0 };
+	const size_t dname_len = knot_dname_size(dname);
+	const size_t empty_len = sizeof(copy) - dname_len;
+	memmove(copy + empty_len, dname, dname_len);
+
+	// add new zero-byte label
+	if (empty_len >= 2) {
+		uint8_t *pos = copy + empty_len - 2;
+		pos[0] = 0x01;
+		pos[1] = 0x00;
+		return knot_dname_copy(pos, NULL);
+	}
+
+	// find apex position in the buffer
+	size_t apex_len = knot_dname_size(apex);
+	const uint8_t *apex_pos = copy + sizeof(copy) - apex_len;
+	assert(knot_dname_is_equal(apex, apex_pos));
+
+	// find first label which can be incremented
+	uint8_t *pos = copy + empty_len;
+	while (pos != apex_pos) {
+		if (inc_label(copy, &pos)) {
+			return knot_dname_copy(pos, NULL);
+		}
+		strip_label(&pos);
+	}
+
+	// apex completes the chain
+	return knot_dname_copy(pos, NULL);
+}