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/* 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);
}
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