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-rw-r--r--lib/dnssec/signature.c304
1 files changed, 304 insertions, 0 deletions
diff --git a/lib/dnssec/signature.c b/lib/dnssec/signature.c
new file mode 100644
index 0000000..aadb5cb
--- /dev/null
+++ b/lib/dnssec/signature.c
@@ -0,0 +1,304 @@
+/* Copyright (C) CZ.NIC, z.s.p.o. <knot-resolver@labs.nic.cz>
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#include <arpa/inet.h>
+#include <string.h>
+
+#include <libdnssec/error.h>
+#include <libdnssec/key.h>
+#include <libdnssec/sign.h>
+#include <libknot/descriptor.h>
+#include <libknot/packet/rrset-wire.h>
+#include <libknot/packet/wire.h>
+#include <libknot/rrset.h>
+#include <libknot/rrtype/rrsig.h>
+#include <libknot/rrtype/ds.h>
+#include <libknot/wire.h>
+
+#include "lib/defines.h"
+#include "lib/utils.h"
+#include "lib/dnssec/signature.h"
+
+static int authenticate_ds(const dnssec_key_t *key, dnssec_binary_t *ds_rdata, uint8_t digest_type)
+{
+ /* Compute DS RDATA from the DNSKEY. */
+ dnssec_binary_t computed_ds = { 0, };
+ int ret = dnssec_key_create_ds(key, digest_type, &computed_ds);
+ if (ret != DNSSEC_EOK)
+ goto fail;
+
+ /* DS records contain algorithm, key tag and the digest.
+ * Therefore the comparison of the two DS is sufficient.
+ */
+ ret = (ds_rdata->size == computed_ds.size) &&
+ (memcmp(ds_rdata->data, computed_ds.data, ds_rdata->size) == 0);
+ ret = ret ? kr_ok() : kr_error(ENOENT);
+
+fail:
+ dnssec_binary_free(&computed_ds);
+ return kr_error(ret);
+}
+
+int kr_authenticate_referral(const knot_rrset_t *ref, const dnssec_key_t *key)
+{
+ if (kr_fails_assert(ref && key))
+ return kr_error(EINVAL);
+ if (ref->type != KNOT_RRTYPE_DS)
+ return kr_error(EINVAL);
+
+ /* Determine whether to ignore SHA1 digests, because:
+ https://datatracker.ietf.org/doc/html/rfc4509#section-3
+ * Now, the RFCs seem to only mention SHA1 and SHA256 (e.g. no SHA384),
+ * but the most natural extension is to make any other algorithm trump SHA1.
+ * (Note that the old GOST version is already unsupported by libdnssec.) */
+ bool skip_sha1 = false;
+ knot_rdata_t *rd = ref->rrs.rdata;
+ for (int i = 0; i < ref->rrs.count; ++i, rd = knot_rdataset_next(rd)) {
+ const uint8_t algo = knot_ds_digest_type(rd);
+ if (algo != DNSSEC_KEY_DIGEST_SHA1 && dnssec_algorithm_digest_support(algo)) {
+ skip_sha1 = true;
+ break;
+ }
+ }
+ /* But otherwise try all possible DS records. */
+ int ret = 0;
+ rd = ref->rrs.rdata;
+ for (int i = 0; i < ref->rrs.count; ++i, rd = knot_rdataset_next(rd)) {
+ const uint8_t algo = knot_ds_digest_type(rd);
+ if (skip_sha1 && algo == DNSSEC_KEY_DIGEST_SHA1)
+ continue;
+ dnssec_binary_t ds_rdata = {
+ .size = rd->len,
+ .data = rd->data
+ };
+ ret = authenticate_ds(key, &ds_rdata, algo);
+ if (ret == 0) /* Found a good DS */
+ return kr_ok();
+ }
+
+ return kr_error(ret);
+}
+
+/**
+ * Adjust TTL in wire format.
+ * @param wire RR Set in wire format.
+ * @param wire_size Size of the wire data portion.
+ * @param new_ttl TTL value to be set for all RRs.
+ * @return 0 or error code.
+ */
+static int adjust_wire_ttl(uint8_t *wire, size_t wire_size, uint32_t new_ttl)
+{
+ if (kr_fails_assert(wire))
+ return kr_error(EINVAL);
+ static_assert(sizeof(uint16_t) == 2, "uint16_t must be exactly 2 bytes");
+ static_assert(sizeof(uint32_t) == 4, "uint32_t must be exactly 4 bytes");
+ uint16_t rdlen;
+
+ int ret;
+
+ new_ttl = htonl(new_ttl);
+
+ size_t i = 0;
+ /* RR wire format in RFC1035 3.2.1 */
+ while(i < wire_size) {
+ ret = knot_dname_size(wire + i);
+ if (ret < 0)
+ return ret;
+ i += ret + 4;
+ memcpy(wire + i, &new_ttl, sizeof(uint32_t));
+ i += sizeof(uint32_t);
+
+ memcpy(&rdlen, wire + i, sizeof(uint16_t));
+ rdlen = ntohs(rdlen);
+ i += sizeof(uint16_t) + rdlen;
+
+ if (kr_fails_assert(i <= wire_size))
+ return kr_error(EINVAL);
+ }
+
+ return kr_ok();
+}
+
+/*!
+ * \brief Add RRSIG RDATA without signature to signing context.
+ *
+ * Requires signer name in RDATA in canonical form.
+ *
+ * \param ctx Signing context.
+ * \param rdata Pointer to RRSIG RDATA.
+ *
+ * \return Error code, KNOT_EOK if successful.
+ */
+#define RRSIG_RDATA_SIGNER_OFFSET 18
+static int sign_ctx_add_self(dnssec_sign_ctx_t *ctx, const uint8_t *rdata)
+{
+ if (kr_fails_assert(ctx && rdata))
+ return kr_error(EINVAL);
+
+ int result;
+
+ // static header
+
+ dnssec_binary_t header = {
+ .data = (uint8_t *)rdata,
+ .size = RRSIG_RDATA_SIGNER_OFFSET,
+ };
+
+ result = dnssec_sign_add(ctx, &header);
+ if (result != DNSSEC_EOK)
+ return result;
+
+ // signer name
+
+ const uint8_t *rdata_signer = rdata + RRSIG_RDATA_SIGNER_OFFSET;
+ dnssec_binary_t signer = { 0 };
+ signer.data = knot_dname_copy(rdata_signer, NULL);
+ signer.size = knot_dname_size(signer.data);
+
+ result = dnssec_sign_add(ctx, &signer);
+ free(signer.data);
+
+ return result;
+}
+#undef RRSIG_RDATA_SIGNER_OFFSET
+
+/*!
+ * \brief Add covered RRs to signing context.
+ *
+ * Requires all DNAMEs in canonical form and all RRs ordered canonically.
+ *
+ * \param ctx Signing context.
+ * \param covered Covered RRs.
+ *
+ * \return Error code, KNOT_EOK if successful.
+ */
+static int sign_ctx_add_records(dnssec_sign_ctx_t *ctx, const knot_rrset_t *covered,
+ uint32_t orig_ttl, int trim_labels)
+{
+ if (!ctx || !covered || trim_labels < 0)
+ return kr_error(EINVAL);
+
+ // huge block of rrsets can be optionally created
+ static uint8_t wire_buffer[KNOT_WIRE_MAX_PKTSIZE];
+ int written = knot_rrset_to_wire(covered, wire_buffer, sizeof(wire_buffer), NULL);
+ if (written < 0)
+ return written;
+
+ /* Set original ttl. */
+ int ret = adjust_wire_ttl(wire_buffer, written, orig_ttl);
+ if (ret != 0)
+ return ret;
+
+ if (!trim_labels) {
+ const dnssec_binary_t wire_binary = {
+ .size = written,
+ .data = wire_buffer
+ };
+ return dnssec_sign_add(ctx, &wire_binary);
+ }
+
+ /* RFC4035 5.3.2
+ * Remove leftmost labels and replace them with '*.'
+ * for each RR in covered.
+ */
+ uint8_t *beginp = wire_buffer;
+ for (uint16_t i = 0; i < covered->rrs.count; ++i) {
+ /* RR(i) = name | type | class | OrigTTL | RDATA length | RDATA */
+ for (int j = 0; j < trim_labels; ++j) {
+ if (kr_fails_assert(beginp[0]))
+ return kr_error(EINVAL);
+ beginp = (uint8_t *) knot_wire_next_label(beginp, NULL);
+ if (kr_fails_assert(beginp))
+ return kr_error(EFAULT);
+ }
+ *(--beginp) = '*';
+ *(--beginp) = 1;
+ const size_t rdatalen_offset = knot_dname_size(beginp) + /* name */
+ sizeof(uint16_t) + /* type */
+ sizeof(uint16_t) + /* class */
+ sizeof(uint32_t); /* OrigTTL */
+ const uint8_t *rdatalen_ptr = beginp + rdatalen_offset;
+ const uint16_t rdata_size = knot_wire_read_u16(rdatalen_ptr);
+ const size_t rr_size = rdatalen_offset +
+ sizeof(uint16_t) + /* RDATA length */
+ rdata_size; /* RDATA */
+ const dnssec_binary_t wire_binary = {
+ .size = rr_size,
+ .data = beginp
+ };
+ ret = dnssec_sign_add(ctx, &wire_binary);
+ if (ret != 0)
+ break;
+ beginp += rr_size;
+ }
+ return ret;
+}
+
+/*!
+ * \brief Add all data covered by signature into signing context.
+ *
+ * RFC 4034: The signature covers RRSIG RDATA field (excluding the signature)
+ * and all matching RR records, which are ordered canonically.
+ *
+ * Requires all DNAMEs in canonical form and all RRs ordered canonically.
+ *
+ * \param ctx Signing context.
+ * \param rrsig_rdata RRSIG RDATA with populated fields except signature.
+ * \param covered Covered RRs.
+ *
+ * \return Error code, KNOT_EOK if successful.
+ */
+/* TODO -- Taken from knot/src/knot/dnssec/rrset-sign.c. Re-write for better fit needed. */
+static int sign_ctx_add_data(dnssec_sign_ctx_t *ctx, const uint8_t *rrsig_rdata,
+ const knot_rrset_t *covered, uint32_t orig_ttl, int trim_labels)
+{
+ int result = sign_ctx_add_self(ctx, rrsig_rdata);
+ if (result != KNOT_EOK)
+ return result;
+
+ return sign_ctx_add_records(ctx, covered, orig_ttl, trim_labels);
+}
+
+int kr_check_signature(const knot_rdata_t *rrsig,
+ const dnssec_key_t *key, const knot_rrset_t *covered,
+ int trim_labels)
+{
+ if (!rrsig || !key || !dnssec_key_can_verify(key))
+ return kr_error(EINVAL);
+
+ int ret = 0;
+ dnssec_sign_ctx_t *sign_ctx = NULL;
+ dnssec_binary_t signature = {
+ .data = /*const-cast*/(uint8_t*)knot_rrsig_signature(rrsig),
+ .size = knot_rrsig_signature_len(rrsig),
+ };
+ if (!signature.data || !signature.size) {
+ ret = kr_error(EINVAL);
+ goto fail;
+ }
+
+ if (dnssec_sign_new(&sign_ctx, key) != 0) {
+ ret = kr_error(ENOMEM);
+ goto fail;
+ }
+
+ uint32_t orig_ttl = knot_rrsig_original_ttl(rrsig);
+
+ if (sign_ctx_add_data(sign_ctx, rrsig->data, covered, orig_ttl, trim_labels) != 0) {
+ ret = kr_error(ENOMEM);
+ goto fail;
+ }
+
+ ret = dnssec_sign_verify(sign_ctx, false, &signature);
+ if (ret != 0) {
+ ret = kr_error(EBADMSG);
+ goto fail;
+ }
+
+ ret = kr_ok();
+
+fail:
+ dnssec_sign_free(sign_ctx);
+ return ret;
+}
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