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-rw-r--r--lib/cookies/helper.c268
1 files changed, 268 insertions, 0 deletions
diff --git a/lib/cookies/helper.c b/lib/cookies/helper.c
new file mode 100644
index 0000000..4867817
--- /dev/null
+++ b/lib/cookies/helper.c
@@ -0,0 +1,268 @@
+/* Copyright (C) CZ.NIC, z.s.p.o. <knot-resolver@labs.nic.cz>
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#include <libknot/rrtype/opt.h>
+#include <libknot/rrtype/opt-cookie.h>
+
+#include "lib/cookies/helper.h"
+#include "lib/defines.h"
+
+/**
+ * @brief Check whether there is a cached cookie that matches the current
+ * client cookie.
+ */
+static const uint8_t *peek_and_check_cc(kr_cookie_lru_t *cache, const void *sa,
+ const uint8_t *cc, uint16_t cc_len)
+{
+ if (kr_fails_assert(cache && sa && cc && cc_len))
+ return NULL;
+
+ const uint8_t *cached_opt = kr_cookie_lru_get(cache, sa);
+ if (!cached_opt)
+ return NULL;
+
+ const uint8_t *cached_cc = knot_edns_opt_get_data((uint8_t *) cached_opt);
+
+ if (cc_len == KNOT_OPT_COOKIE_CLNT &&
+ 0 == memcmp(cc, cached_cc, cc_len)) {
+ return cached_opt;
+ }
+
+ return NULL;
+}
+
+/**
+ * @brief Put a client cookie into the RR Set.
+ */
+static int opt_rr_put_cookie(knot_rrset_t *opt_rr, uint8_t *data,
+ uint16_t data_len, knot_mm_t *mm)
+{
+ if (kr_fails_assert(opt_rr && data && data_len > 0))
+ return kr_error(EINVAL);
+
+ const uint8_t *cc = NULL, *sc = NULL;
+ uint16_t cc_len = 0, sc_len = 0;
+
+ int ret = knot_edns_opt_cookie_parse(data, data_len, &cc, &cc_len,
+ &sc, &sc_len);
+ if (ret != KNOT_EOK)
+ return kr_error(EINVAL);
+ if (kr_fails_assert(data_len == cc_len + sc_len))
+ return kr_error(EINVAL);
+
+ uint16_t cookies_size = data_len;
+ uint8_t *cookies_data = NULL;
+
+ ret = knot_edns_reserve_unique_option(opt_rr, KNOT_EDNS_OPTION_COOKIE,
+ cookies_size, &cookies_data, mm);
+ if (ret != KNOT_EOK)
+ return kr_error(EINVAL);
+ if (kr_fails_assert(cookies_data))
+ return kr_error(EINVAL);
+
+ cookies_size = knot_edns_opt_cookie_write(cc, cc_len, sc, sc_len,
+ cookies_data, cookies_size);
+ if (cookies_size == 0)
+ return kr_error(EINVAL);
+ if (kr_fails_assert(cookies_size == data_len))
+ return kr_error(EINVAL);
+
+ return kr_ok();
+}
+
+/**
+ * @brief Puts entire EDNS option into the RR Set.
+ */
+static int opt_rr_put_cookie_opt(knot_rrset_t *opt_rr, uint8_t *option, knot_mm_t *mm)
+{
+ if (kr_fails_assert(opt_rr && option))
+ return kr_error(EINVAL);
+
+ uint16_t opt_code = knot_edns_opt_get_code(option);
+ if (opt_code != KNOT_EDNS_OPTION_COOKIE)
+ return kr_error(EINVAL);
+
+ uint16_t opt_len = knot_edns_opt_get_length(option);
+ uint8_t *opt_data = knot_edns_opt_get_data(option);
+ if (!opt_data || opt_len == 0)
+ return kr_error(EINVAL);
+
+ return opt_rr_put_cookie(opt_rr, opt_data, opt_len, mm);
+}
+
+int kr_request_put_cookie(const struct kr_cookie_comp *clnt_comp,
+ kr_cookie_lru_t *cookie_cache,
+ const struct sockaddr *clnt_sa,
+ const struct sockaddr *srvr_sa,
+ struct kr_request *req)
+{
+ if (!clnt_comp || !req)
+ return kr_error(EINVAL);
+
+ if (!req->ctx->opt_rr)
+ return kr_ok();
+
+ if (!clnt_comp->secr || (clnt_comp->alg_id < 0) || !cookie_cache)
+ return kr_error(EINVAL);
+
+ /*
+ * Generate client cookie from client address, server address and
+ * secret quantity.
+ */
+ struct knot_cc_input input = {
+ .clnt_sockaddr = clnt_sa,
+ .srvr_sockaddr = srvr_sa,
+ .secret_data = clnt_comp->secr->data,
+ .secret_len = clnt_comp->secr->size
+ };
+ uint8_t cc[KNOT_OPT_COOKIE_CLNT];
+ uint16_t cc_len = KNOT_OPT_COOKIE_CLNT;
+ const struct knot_cc_alg *cc_alg = kr_cc_alg_get(clnt_comp->alg_id);
+ if (!cc_alg)
+ return kr_error(EINVAL);
+ if (kr_fails_assert(cc_alg->gen_func))
+ return kr_error(EINVAL);
+ cc_len = cc_alg->gen_func(&input, cc, cc_len);
+ if (cc_len != KNOT_OPT_COOKIE_CLNT)
+ return kr_error(EINVAL);
+
+ const uint8_t *cached_cookie = peek_and_check_cc(cookie_cache,
+ srvr_sa, cc, cc_len);
+
+ /* Add cookie option. */
+ int ret;
+ if (cached_cookie) {
+ ret = opt_rr_put_cookie_opt(req->ctx->opt_rr,
+ (uint8_t *)cached_cookie,
+ req->ctx->pool);
+ } else {
+ ret = opt_rr_put_cookie(req->ctx->opt_rr, cc, cc_len,
+ req->ctx->pool);
+ }
+
+ return ret;
+}
+
+int kr_answer_write_cookie(struct knot_sc_input *sc_input,
+ const struct kr_nonce_input *nonce,
+ const struct knot_sc_alg *alg, knot_pkt_t *pkt)
+{
+ if (!sc_input || !sc_input->cc || sc_input->cc_len == 0)
+ return kr_error(EINVAL);
+
+ if (!sc_input->srvr_data || !sc_input->srvr_data->clnt_sockaddr ||
+ !sc_input->srvr_data->secret_data ||
+ !sc_input->srvr_data->secret_len) {
+ return kr_error(EINVAL);
+ }
+
+ if (!nonce)
+ return kr_error(EINVAL);
+
+ if (!alg || !alg->hash_size || !alg->hash_func)
+ return kr_error(EINVAL);
+
+ if (!pkt || !pkt->opt_rr)
+ return kr_error(EINVAL);
+
+ uint16_t nonce_len = KR_NONCE_LEN;
+ uint16_t hash_len = alg->hash_size;
+
+ /*
+ * Space for cookie is reserved inside the EDNS OPT RR of
+ * the answer packet.
+ */
+ uint8_t *cookie = NULL;
+ uint16_t cookie_len = knot_edns_opt_cookie_data_len(sc_input->cc_len,
+ nonce_len + hash_len);
+ if (cookie_len == 0)
+ return kr_error(EINVAL);
+
+ int ret = knot_edns_reserve_unique_option(pkt->opt_rr,
+ KNOT_EDNS_OPTION_COOKIE,
+ cookie_len, &cookie,
+ &pkt->mm);
+ if (ret != KNOT_EOK)
+ return kr_error(ENOMEM);
+ if (kr_fails_assert(cookie))
+ return kr_error(EFAULT);
+
+ /*
+ * Function knot_edns_opt_cookie_data_len() returns the sum of its
+ * parameters or zero. Anyway, let's check again.
+ */
+ if (cookie_len < (sc_input->cc_len + nonce_len + hash_len))
+ return kr_error(EINVAL);
+
+ /* Copy client cookie data portion. */
+ memcpy(cookie, sc_input->cc, sc_input->cc_len);
+
+ if (nonce_len) {
+ /* Write nonce data portion. */
+ kr_nonce_write_wire(cookie + sc_input->cc_len, nonce_len,
+ nonce);
+ /* Adjust input for written nonce value. */
+ sc_input->nonce = cookie + sc_input->cc_len;
+ sc_input->nonce_len = nonce_len;
+ }
+
+ hash_len = alg->hash_func(sc_input,
+ cookie + sc_input->cc_len + nonce_len,
+ hash_len);
+ /* Zero nonce values. */
+ sc_input->nonce = NULL;
+ sc_input->nonce_len = 0;
+
+ return (hash_len != 0) ? kr_ok() : kr_error(EINVAL);
+}
+
+int kr_pkt_set_ext_rcode(knot_pkt_t *pkt, uint16_t whole_rcode)
+{
+ /*
+ * RFC6891 6.1.3 -- extended RCODE forms the upper 8 bits of whole
+ * 12-bit RCODE (together with the 4 bits of 'normal' RCODE).
+ *
+ * | 11 10 09 08 07 06 05 04 | 03 02 01 00 |
+ * | 12-bit whole RCODE |
+ * | 8-bit extended RCODE | 4-bit RCODE |
+ */
+
+ if (!pkt || !knot_pkt_has_edns(pkt))
+ return kr_error(EINVAL);
+
+ uint8_t rcode = whole_rcode & 0x0f;
+ uint8_t ext_rcode = whole_rcode >> 4;
+ knot_wire_set_rcode(pkt->wire, rcode);
+ knot_edns_set_ext_rcode(pkt->opt_rr, ext_rcode);
+
+ return kr_ok();
+}
+
+uint8_t *kr_no_question_cookie_query(const knot_pkt_t *pkt)
+{
+ if (!pkt || knot_wire_get_qdcount(pkt->wire) > 0)
+ return false;
+
+ if (knot_wire_get_qr(pkt->wire) != 0 || !pkt->opt_rr)
+ return false;
+
+ return knot_edns_get_option(pkt->opt_rr, KNOT_EDNS_OPTION_COOKIE);
+}
+
+int kr_parse_cookie_opt(uint8_t *cookie_opt, struct knot_dns_cookies *cookies)
+{
+ if (!cookie_opt || !cookies)
+ return kr_error(EINVAL);
+
+ const uint8_t *cookie_data = knot_edns_opt_get_data(cookie_opt);
+ uint16_t cookie_len = knot_edns_opt_get_length(cookie_opt);
+ if (!cookie_data || cookie_len == 0)
+ return kr_error(EINVAL);
+
+ int ret = knot_edns_opt_cookie_parse(cookie_data, cookie_len,
+ &cookies->cc, &cookies->cc_len,
+ &cookies->sc, &cookies->sc_len);
+
+ return (ret == KNOT_EOK) ? kr_ok() : kr_error(EINVAL);
+}