diff options
Diffstat (limited to 'lib/cookies/helper.c')
| -rw-r--r-- | lib/cookies/helper.c | 296 |
1 files changed, 296 insertions, 0 deletions
diff --git a/lib/cookies/helper.c b/lib/cookies/helper.c new file mode 100644 index 0000000..e07b8cb --- /dev/null +++ b/lib/cookies/helper.c @@ -0,0 +1,296 @@ +/* Copyright (C) 2016-2017 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 <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) +{ + assert(cache && sa && cc && cc_len); + + 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) +{ + assert(opt_rr && data && data_len > 0); + + 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); + } + assert(data_len == cc_len + sc_len); + + 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); + } + assert(cookies_data != NULL); + + 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); + } + assert(cookies_size == data_len); + + 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) +{ + assert(opt_rr && option); + + 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); + } + assert(cc_alg->gen_func); + 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); + } + assert(cookie != NULL); + + /* + * 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); +} |