1 files changed, 110 insertions, 0 deletions
diff --git a/lib/cookies/alg_sha.c b/lib/cookies/alg_sha.c
new file mode 100644
index 0000000..34e79c3
--- /dev/null
+++ b/lib/cookies/alg_sha.c
@@ -0,0 +1,110 @@
+/*  Copyright (C) CZ.NIC, z.s.p.o. <knot-resolver@labs.nic.cz>
+ *  SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#include <nettle/hmac.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <libknot/errcode.h>
+#include <libknot/rrtype/opt-cookie.h>
+
+#include "lib/cookies/alg_sha.h"
+#include "lib/utils.h"
+
+/**
+ * @brief Update hash value.
+ *
+ * @param ctx HMAC-SHA256 context to be updated.
+ * @param sa  Socket address.
+ */
+static inline void update_hash(struct hmac_sha256_ctx *ctx,
+                               const struct sockaddr *sa)
+{
+	if (kr_fails_assert(ctx && sa))
+		return;
+
+	int addr_len = kr_inaddr_len(sa);
+	const uint8_t *addr = (uint8_t *)kr_inaddr(sa);
+
+	if (addr && addr_len > 0) {
+		hmac_sha256_update(ctx, addr_len, addr);
+	}
+}
+
+/**
+ * @brief Compute client cookie using HMAC-SHA256-64.
+ * @note At least one of the arguments must be non-null.
+ * @param input  input parameters
+ * @param cc_out buffer for computed client cookie
+ * @param cc_len buffer size
+ * @return Non-zero size of written data on success, 0 in case of a failure.
+ */
+static uint16_t cc_gen_hmac_sha256_64(const struct knot_cc_input *input,
+                                      uint8_t *cc_out, uint16_t cc_len)
+{
+	if (!knot_cc_input_is_valid(input) ||
+	    !cc_out || cc_len < KNOT_OPT_COOKIE_CLNT) {
+		return 0;
+	}
+
+	struct hmac_sha256_ctx ctx;
+	hmac_sha256_set_key(&ctx, input->secret_len, input->secret_data);
+
+	if (input->clnt_sockaddr) {
+		update_hash(&ctx, input->clnt_sockaddr);
+	}
+
+	if (input->srvr_sockaddr) {
+		update_hash(&ctx, input->srvr_sockaddr);
+	}
+
+	/* KNOT_OPT_COOKIE_CLNT <= SHA256_DIGEST_SIZE */
+
+	hmac_sha256_digest(&ctx, KNOT_OPT_COOKIE_CLNT, cc_out);
+
+	return KNOT_OPT_COOKIE_CLNT;
+}
+
+#define SRVR_HMAC_SHA256_64_HASH_SIZE 8
+
+/**
+ * @brief Compute server cookie hash using HMAC-SHA256-64).
+ * @note Server cookie = nonce | time | HMAC-SHA256-64( server secret, client cookie | nonce| time | client IP )
+ * @param input    data to compute cookie from
+ * @param hash_out hash output buffer
+ * @param hash_len buffer size
+ * @return Non-zero size of written data on success, 0 in case of a failure.
+ */
+static uint16_t sc_gen_hmac_sha256_64(const struct knot_sc_input *input,
+                                      uint8_t *hash_out, uint16_t hash_len)
+{
+	if (!knot_sc_input_is_valid(input) ||
+	    !hash_out || hash_len < SRVR_HMAC_SHA256_64_HASH_SIZE) {
+		return 0;
+	}
+
+	struct hmac_sha256_ctx ctx;
+	hmac_sha256_set_key(&ctx, input->srvr_data->secret_len,
+	                    input->srvr_data->secret_data);
+
+	hmac_sha256_update(&ctx, input->cc_len, input->cc);
+
+	if (input->nonce && input->nonce_len) {
+		hmac_sha256_update(&ctx, input->nonce_len, input->nonce);
+	}
+
+	if (input->srvr_data->clnt_sockaddr) {
+		update_hash(&ctx, input->srvr_data->clnt_sockaddr);
+	}
+
+	/* SRVR_HMAC_SHA256_64_HASH_SIZE < SHA256_DIGEST_SIZE */
+
+	hmac_sha256_digest(&ctx, SRVR_HMAC_SHA256_64_HASH_SIZE, hash_out);
+
+	return SRVR_HMAC_SHA256_64_HASH_SIZE;
+}
+
+const struct knot_cc_alg knot_cc_alg_hmac_sha256_64 = { KNOT_OPT_COOKIE_CLNT, cc_gen_hmac_sha256_64 };
+
+const struct knot_sc_alg knot_sc_alg_hmac_sha256_64 = { SRVR_HMAC_SHA256_64_HASH_SIZE, sc_gen_hmac_sha256_64 };