Adding upstream version 3.2.6.upstream/3.2.6upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

3 files changed, 718 insertions, 0 deletions

diff --git a/src/libdnssec/sign/der.c b/src/libdnssec/sign/der.c
new file mode 100644
index 0000000..cd6102d
--- /dev/null
+++ b/src/libdnssec/sign/der.c
@@ -0,0 +1,229 @@
+/*  Copyright (C) 2018 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 <stdbool.h>
+
+#include "libdnssec/shared/bignum.h"
+#include "libdnssec/binary.h"
+#include "libdnssec/error.h"
+#include "libdnssec/sign/der.h"
+#include "libdnssec/shared/binary_wire.h"
+
+/*
+ * In fact, this is a very tiny subset of ASN.1 encoding format implementation,
+ * which is necessary for the purpose of DNSSEC.
+ *
+ * References: RFC 3279 (X.509 PKI), X.690, RFC 6605 (ECDSA), RFC8080 (EDDSA)
+ *
+ * Dss-Sig-Value ::= SEQUENCE { r INTEGER, s INTEGER }
+ */
+
+#define ASN1_TYPE_SEQUENCE 0x30
+#define ASN1_TYPE_INTEGER  0x02
+
+#define ASN1_MAX_SIZE 127
+
+/*!
+ * Check if the next object has a given type.
+ */
+static bool asn1_expect_type(wire_ctx_t *wire, uint8_t type)
+{
+	assert(wire);
+	return (wire_ctx_available(wire) >= 1 && wire_ctx_read_u8(wire) == type);
+}
+
+/*!
+ * Decode the size of the object (only short format is supported).
+ */
+static int asn1_decode_size(wire_ctx_t *wire, size_t *size)
+{
+	assert(wire);
+	assert(size);
+
+	if (wire_ctx_available(wire) < 1) {
+		return DNSSEC_MALFORMED_DATA;
+	}
+
+	uint8_t byte = wire_ctx_read_u8(wire);
+	if (byte & 0x80) {
+		// long form, we do not need it for DNSSEC
+		return DNSSEC_NOT_IMPLEMENTED_ERROR;
+	}
+
+	*size = byte;
+
+	return DNSSEC_EOK;
+}
+
+/*!
+ * Decode an unsigned integer object.
+ */
+static int asn1_decode_integer(wire_ctx_t *wire, dnssec_binary_t *_value)
+{
+	assert(wire);
+	assert(_value);
+
+	if (!asn1_expect_type(wire, ASN1_TYPE_INTEGER)) {
+		return DNSSEC_MALFORMED_DATA;
+	}
+
+	size_t size;
+	int result = asn1_decode_size(wire, &size);
+	if (result != DNSSEC_EOK) {
+		return result;
+	}
+
+	if (size == 0 || size > wire_ctx_available(wire)) {
+		return DNSSEC_MALFORMED_DATA;
+	}
+
+	dnssec_binary_t value = { .data = wire->position, .size = size };
+	wire->position += size;
+
+	// skip leading zeroes (unless equal to zero)
+	while (value.size > 1 && value.data[0] == 0) {
+		value.data += 1;
+		value.size -= 1;
+	}
+
+	*_value = value;
+
+	return DNSSEC_EOK;
+}
+
+/*!
+ * Encode object header (type and length).
+ */
+static void asn1_write_header(wire_ctx_t *wire, uint8_t type, size_t length)
+{
+	assert(wire);
+	assert(length < ASN1_MAX_SIZE);
+
+	wire_ctx_write_u8(wire, type);
+	wire_ctx_write_u8(wire, length);
+}
+
+/*!
+ * Encode unsigned integer object.
+ */
+static void asn1_write_integer(wire_ctx_t *wire, size_t integer_size,
+			       const dnssec_binary_t *integer)
+{
+	assert(wire);
+	assert(integer);
+	assert(integer->data);
+
+	asn1_write_header(wire, ASN1_TYPE_INTEGER, integer_size);
+	bignum_write(wire, integer_size, integer);
+}
+
+/*!
+ * Decode signature parameters from X.509 ECDSA signature.
+ */
+int dss_sig_value_decode(const dnssec_binary_t *der,
+			 dnssec_binary_t *r, dnssec_binary_t *s)
+{
+	if (!der || !der->data || !r || !s) {
+		return DNSSEC_EINVAL;
+	}
+
+	wire_ctx_t wire = binary_init(der);
+
+	size_t size;
+	int result;
+
+	// decode the sequence
+
+	if (!asn1_expect_type(&wire, ASN1_TYPE_SEQUENCE)) {
+		return DNSSEC_MALFORMED_DATA;
+	}
+
+	result = asn1_decode_size(&wire, &size);
+	if (result != DNSSEC_EOK) {
+		return result;
+	}
+
+	if (size != wire_ctx_available(&wire)) {
+		return DNSSEC_MALFORMED_DATA;
+	}
+
+	// decode the 'r' and 's' values
+
+	dnssec_binary_t der_r;
+	result = asn1_decode_integer(&wire, &der_r);
+	if (result != DNSSEC_EOK) {
+		return result;
+	}
+
+	dnssec_binary_t der_s;
+	result = asn1_decode_integer(&wire, &der_s);
+	if (result != DNSSEC_EOK) {
+		return result;
+	}
+
+	if (wire_ctx_available(&wire) != 0) {
+		return DNSSEC_MALFORMED_DATA;
+	}
+
+	*r = der_r;
+	*s = der_s;
+
+	return DNSSEC_EOK;
+}
+
+/*!
+ * Encode signature parameters from X.509 ECDSA signature.
+ */
+int dss_sig_value_encode(const dnssec_binary_t *r, const dnssec_binary_t *s,
+			 dnssec_binary_t *der)
+{
+	if (!r || !r->data || !s || !s->data || !der) {
+		return DNSSEC_EINVAL;
+	}
+
+	size_t r_size = bignum_size_s(r);
+	size_t s_size = bignum_size_s(s);
+
+	// check supported inputs range
+
+	if (r_size > ASN1_MAX_SIZE || s_size > ASN1_MAX_SIZE) {
+		return DNSSEC_NOT_IMPLEMENTED_ERROR;
+	}
+
+	size_t seq_size = 2 + r_size + 2 + s_size;
+	if (seq_size > ASN1_MAX_SIZE) {
+		return DNSSEC_NOT_IMPLEMENTED_ERROR;
+	}
+
+	// encode result
+
+	size_t total_size = 2 + seq_size;
+
+	dnssec_binary_t _der = { 0 };
+	if (dnssec_binary_alloc(&_der, total_size)) {
+		return DNSSEC_ENOMEM;
+	}
+
+	wire_ctx_t wire = binary_init(&_der);
+	asn1_write_header(&wire, ASN1_TYPE_SEQUENCE, seq_size);
+	asn1_write_integer(&wire, r_size, r);
+	asn1_write_integer(&wire, s_size, s);
+	assert(wire_ctx_available(&wire) == 0);
+
+	*der = _der;
+
+	return DNSSEC_EOK;
+}
diff --git a/src/libdnssec/sign/der.h b/src/libdnssec/sign/der.h
new file mode 100644
index 0000000..687b061
--- /dev/null
+++ b/src/libdnssec/sign/der.h
@@ -0,0 +1,56 @@
+/*  Copyright (C) 2018 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/>.
+ */
+
+#pragma once
+
+#include "libdnssec/binary.h"
+
+/*
+ * The ECDSA signatures in DNSSEC are encoded differently than in X.509
+ * (PKCS #1). The cryptographic libraries usually produce the signatures in
+ * X.509 format, which uses Dss-Sig-Value to encapsulate 'r' and 's' values
+ * of the signature.
+ *
+ * This module provides decoding and encoding of this format.
+ *
+ * The 'r' and 's' values are treated as unsigned values: The leading zeroes
+ * are stripped on decoding; an extra leading zero is added on encoding in case
+ * the value starts with a set bit.
+ */
+
+/*!
+ * Decode signature parameters from X.509 ECDSA signature.
+ *
+ * \param[in]  der  X.509 encoded signature.
+ * \param[out] s    Value 's' of the signature, will point to the data in DER.
+ * \param[out] r    Value 'r' of the signature, will point to the data in DER.
+ *
+ * \return Error code, DNSSEC_EOK if successful.
+ */
+int dss_sig_value_decode(const dnssec_binary_t *der,
+			 dnssec_binary_t *r, dnssec_binary_t *s);
+
+/*!
+ * Encode signature parameters from X.509 ECDSA signature.
+ *
+ * \param[in]  s    Value 's' of the signature.
+ * \param[in]  r    Value 'r' of the signature.
+ * \param[out] der  X.509 signature, the content will be allocated.
+ *
+ * \return Error code, DNSSEC_EOK if successful.
+ */
+int dss_sig_value_encode(const dnssec_binary_t *r, const dnssec_binary_t *s,
+			 dnssec_binary_t *der);
diff --git a/src/libdnssec/sign/sign.c b/src/libdnssec/sign/sign.c
new file mode 100644
index 0000000..3a7bcba
--- /dev/null
+++ b/src/libdnssec/sign/sign.c
@@ -0,0 +1,433 @@
+/*  Copyright (C) 2020 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 <stdlib.h>
+#include <string.h>
+#include <gnutls/gnutls.h>
+#include <gnutls/crypto.h>
+
+#include "contrib/macros.h"
+#include "contrib/vpool/vpool.h"
+#include "libdnssec/shared/bignum.h"
+#include "libdnssec/error.h"
+#include "libdnssec/key.h"
+#include "libdnssec/key/internal.h"
+#include "libdnssec/shared/shared.h"
+#include "libdnssec/sign.h"
+#include "libdnssec/sign/der.h"
+#include "libdnssec/shared/binary_wire.h"
+
+/*!
+ * Signature format conversion callback.
+ *
+ * \param ctx   DNSSEC signing context.
+ * \param from  Data in source format.
+ * \param to    Allocated data in target format.
+ *
+ * \return Error code, DNSSEC_EOK if successful.
+ */
+typedef int (*signature_convert_cb)(dnssec_sign_ctx_t *ctx,
+				    const dnssec_binary_t *from,
+				    dnssec_binary_t *to);
+
+/*!
+ * Algorithm specific callbacks.
+ */
+typedef struct algorithm_functions {
+	//! Convert X.509 signature to DNSSEC format.
+	signature_convert_cb x509_to_dnssec;
+	//! Convert DNSSEC signature to X.509 format.
+	signature_convert_cb dnssec_to_x509;
+} algorithm_functions_t;
+
+typedef struct dnssec_buffer {
+	uint8_t *allocd;	//!< Pointer to allocated data.
+	uint8_t *data;		//!< API: pointer to data to copy from.
+	size_t max_length;
+	size_t length;		//!< API: current length.
+} dnssec_buffer_t;
+
+/*!
+ * DNSSEC signing context.
+ */
+struct dnssec_sign_ctx {
+	const dnssec_key_t *key;		  //!< Signing key.
+	const algorithm_functions_t *functions;	  //!< Implementation specific.
+
+	gnutls_sign_algorithm_t sign_algorithm;   //!< Used algorithm for signing.
+	struct vpool buffer;                      //!< Buffer for the data to be signed.
+};
+
+/* -- signature format conversions ----------------------------------------- */
+
+/*!
+ * Conversion of RSA signature between X.509 and DNSSEC format is a NOOP.
+ *
+ * \note Described in RFC 3110.
+ */
+static int rsa_copy_signature(dnssec_sign_ctx_t *ctx,
+			      const dnssec_binary_t *from,
+			      dnssec_binary_t *to)
+{
+	assert(ctx);
+	assert(from);
+	assert(to);
+
+	return dnssec_binary_dup(from, to);
+}
+
+static const algorithm_functions_t rsa_functions = {
+	.x509_to_dnssec = rsa_copy_signature,
+	.dnssec_to_x509 = rsa_copy_signature,
+};
+
+static size_t ecdsa_sign_integer_size(dnssec_sign_ctx_t *ctx)
+{
+	assert(ctx);
+
+	switch (ctx->sign_algorithm) {
+	case GNUTLS_SIGN_ECDSA_SHA256: return 32;
+	case GNUTLS_SIGN_ECDSA_SHA384: return 48;
+	default: return 0;
+	};
+}
+
+/*!
+ * Convert ECDSA signature to DNSSEC format.
+ *
+ * \note Described in RFC 6605.
+ */
+static int ecdsa_x509_to_dnssec(dnssec_sign_ctx_t *ctx,
+				const dnssec_binary_t *x509,
+				dnssec_binary_t *dnssec)
+{
+	assert(ctx);
+	assert(x509);
+	assert(dnssec);
+
+	dnssec_binary_t value_r = { 0 };
+	dnssec_binary_t value_s = { 0 };
+
+	int result = dss_sig_value_decode(x509, &value_r, &value_s);
+	if (result != DNSSEC_EOK) {
+		return result;
+	}
+
+	size_t int_size = ecdsa_sign_integer_size(ctx);
+	size_t r_size = bignum_size_u(&value_r);
+	size_t s_size = bignum_size_u(&value_s);
+
+	if (r_size > int_size || s_size > int_size) {
+		return DNSSEC_MALFORMED_DATA;
+	}
+
+	result = dnssec_binary_alloc(dnssec, 2 * int_size);
+	if (result != DNSSEC_EOK) {
+		return result;
+	}
+
+	wire_ctx_t wire = binary_init(dnssec);
+	bignum_write(&wire, int_size, &value_r);
+	bignum_write(&wire, int_size, &value_s);
+	assert(wire_ctx_offset(&wire) == dnssec->size);
+
+	return DNSSEC_EOK;
+}
+
+static int ecdsa_dnssec_to_x509(dnssec_sign_ctx_t *ctx,
+				const dnssec_binary_t *dnssec,
+				dnssec_binary_t *x509)
+{
+	assert(ctx);
+	assert(x509);
+	assert(dnssec);
+
+	size_t int_size = ecdsa_sign_integer_size(ctx);
+
+	if (dnssec->size != 2 * int_size) {
+		return DNSSEC_INVALID_SIGNATURE;
+	}
+
+	const dnssec_binary_t value_r = { .size = int_size, .data = dnssec->data };
+	const dnssec_binary_t value_s = { .size = int_size, .data = dnssec->data + int_size };
+
+	return dss_sig_value_encode(&value_r, &value_s, x509);
+}
+
+static const algorithm_functions_t ecdsa_functions = {
+	.x509_to_dnssec = ecdsa_x509_to_dnssec,
+	.dnssec_to_x509 = ecdsa_dnssec_to_x509,
+};
+
+#define eddsa_copy_signature rsa_copy_signature
+static const algorithm_functions_t eddsa_functions = {
+	.x509_to_dnssec = eddsa_copy_signature,
+	.dnssec_to_x509 = eddsa_copy_signature,
+};
+
+/* -- crypto helper functions --------------------------------------------- */
+
+static const algorithm_functions_t *get_functions(const dnssec_key_t *key)
+{
+	uint8_t algorithm = dnssec_key_get_algorithm(key);
+
+	switch ((dnssec_key_algorithm_t)algorithm) {
+	case DNSSEC_KEY_ALGORITHM_RSA_SHA1:
+	case DNSSEC_KEY_ALGORITHM_RSA_SHA1_NSEC3:
+	case DNSSEC_KEY_ALGORITHM_RSA_SHA256:
+	case DNSSEC_KEY_ALGORITHM_RSA_SHA512:
+		return &rsa_functions;
+	case DNSSEC_KEY_ALGORITHM_ECDSA_P256_SHA256:
+	case DNSSEC_KEY_ALGORITHM_ECDSA_P384_SHA384:
+		return &ecdsa_functions;
+	case DNSSEC_KEY_ALGORITHM_ED25519:
+	case DNSSEC_KEY_ALGORITHM_ED448:
+		return &eddsa_functions;
+	default:
+		return NULL;
+	}
+}
+
+#ifndef HAVE_SIGN_DATA2
+/*!
+ * Get digest algorithm used with a given key.
+ */
+static gnutls_digest_algorithm_t get_digest_algorithm(const dnssec_key_t *key)
+{
+	uint8_t algorithm = dnssec_key_get_algorithm(key);
+
+	switch ((dnssec_key_algorithm_t)algorithm) {
+	case DNSSEC_KEY_ALGORITHM_RSA_SHA1:
+	case DNSSEC_KEY_ALGORITHM_RSA_SHA1_NSEC3:
+		return GNUTLS_DIG_SHA1;
+	case DNSSEC_KEY_ALGORITHM_RSA_SHA256:
+	case DNSSEC_KEY_ALGORITHM_ECDSA_P256_SHA256:
+		return GNUTLS_DIG_SHA256;
+	case DNSSEC_KEY_ALGORITHM_RSA_SHA512:
+		return GNUTLS_DIG_SHA512;
+	case DNSSEC_KEY_ALGORITHM_ECDSA_P384_SHA384:
+		return GNUTLS_DIG_SHA384;
+	case DNSSEC_KEY_ALGORITHM_ED25519:
+	case DNSSEC_KEY_ALGORITHM_ED448:
+		return GNUTLS_DIG_SHA512;
+	default:
+		return GNUTLS_DIG_UNKNOWN;
+	}
+}
+#endif
+
+static gnutls_sign_algorithm_t algo_dnssec2gnutls(dnssec_key_algorithm_t algorithm)
+{
+	switch (algorithm) {
+	case DNSSEC_KEY_ALGORITHM_RSA_SHA1:
+	case DNSSEC_KEY_ALGORITHM_RSA_SHA1_NSEC3:
+		return GNUTLS_SIGN_RSA_SHA1;
+	case DNSSEC_KEY_ALGORITHM_RSA_SHA256:
+		return GNUTLS_SIGN_RSA_SHA256;
+	case DNSSEC_KEY_ALGORITHM_ECDSA_P256_SHA256:
+		return GNUTLS_SIGN_ECDSA_SHA256;
+	case DNSSEC_KEY_ALGORITHM_RSA_SHA512:
+		return GNUTLS_SIGN_RSA_SHA512;
+	case DNSSEC_KEY_ALGORITHM_ECDSA_P384_SHA384:
+		return GNUTLS_SIGN_ECDSA_SHA384;
+#ifdef HAVE_ED25519
+	case DNSSEC_KEY_ALGORITHM_ED25519:
+		return GNUTLS_SIGN_EDDSA_ED25519;
+#endif
+#ifdef HAVE_ED448
+	case DNSSEC_KEY_ALGORITHM_ED448:
+		return GNUTLS_SIGN_EDDSA_ED448;
+#endif
+	default:
+		return GNUTLS_SIGN_UNKNOWN;
+	}
+}
+
+/* -- public API ---------------------------------------------------------- */
+
+_public_
+bool dnssec_algorithm_key_support(dnssec_key_algorithm_t algorithm)
+{
+	gnutls_sign_algorithm_t a = algo_dnssec2gnutls(algorithm);
+	return a != GNUTLS_SIGN_UNKNOWN && gnutls_sign_is_secure(a);
+}
+
+_public_
+int dnssec_sign_new(dnssec_sign_ctx_t **ctx_ptr, const dnssec_key_t *key)
+{
+	if (!ctx_ptr) {
+		return DNSSEC_EINVAL;
+	}
+
+	dnssec_sign_ctx_t *ctx = calloc(1, sizeof(*ctx));
+
+	ctx->key = key;
+
+	ctx->functions = get_functions(key);
+	if (ctx->functions == NULL) {
+		free(ctx);
+		return DNSSEC_INVALID_KEY_ALGORITHM;
+	}
+
+	const uint8_t algo_raw = dnssec_key_get_algorithm(key);
+	ctx->sign_algorithm = algo_dnssec2gnutls((dnssec_key_algorithm_t)algo_raw);
+	int result = dnssec_sign_init(ctx);
+	if (result != DNSSEC_EOK) {
+		free(ctx);
+		return result;
+	}
+
+	*ctx_ptr = ctx;
+
+	return DNSSEC_EOK;
+}
+
+_public_
+void dnssec_sign_free(dnssec_sign_ctx_t *ctx)
+{
+	if (!ctx) {
+		return;
+	}
+
+	vpool_reset(&ctx->buffer);
+
+	free(ctx);
+}
+
+_public_
+int dnssec_sign_init(dnssec_sign_ctx_t *ctx)
+{
+	if (!ctx) {
+		return DNSSEC_EINVAL;
+	}
+
+	if (vpool_get_buf(&ctx->buffer) != NULL) {
+		vpool_wipe(&ctx->buffer);
+	} else {
+		vpool_init(&ctx->buffer, 1024, 0);
+	}
+
+	return DNSSEC_EOK;
+}
+
+_public_
+int dnssec_sign_add(dnssec_sign_ctx_t *ctx, const dnssec_binary_t *data)
+{
+	if (!ctx || !data || !data->data) {
+		return DNSSEC_EINVAL;
+	}
+
+	void *result = vpool_insert(&ctx->buffer, vpool_get_length(&ctx->buffer), data->data, data->size);
+	if (result == NULL) {
+		return DNSSEC_SIGN_ERROR;
+	}
+
+	return DNSSEC_EOK;
+}
+
+_public_
+int dnssec_sign_write(dnssec_sign_ctx_t *ctx, dnssec_sign_flags_t flags, dnssec_binary_t *signature)
+{
+	if (!ctx || !signature) {
+		return DNSSEC_EINVAL;
+	}
+
+	if (!dnssec_key_can_sign(ctx->key)) {
+		return DNSSEC_NO_PRIVATE_KEY;
+	}
+
+	gnutls_datum_t data = {
+		.data = vpool_get_buf(&ctx->buffer),
+		.size = vpool_get_length(&ctx->buffer)
+	};
+
+	unsigned gnutls_flags = 0;
+#ifdef HAVE_GNUTLS_REPRODUCIBLE
+	if (flags & DNSSEC_SIGN_REPRODUCIBLE) {
+		gnutls_flags |= GNUTLS_PRIVKEY_FLAG_REPRODUCIBLE;
+	}
+#endif
+
+	assert(ctx->key->private_key);
+	_cleanup_datum_ gnutls_datum_t raw = { 0 };
+#ifdef HAVE_SIGN_DATA2
+	int result = gnutls_privkey_sign_data2(ctx->key->private_key,
+					       ctx->sign_algorithm,
+					       gnutls_flags, &data, &raw);
+#else
+	gnutls_digest_algorithm_t digest_algorithm = get_digest_algorithm(ctx->key);
+	int result = gnutls_privkey_sign_data(ctx->key->private_key,
+					      digest_algorithm,
+					      gnutls_flags, &data, &raw);
+#endif
+	if (result < 0) {
+		return DNSSEC_SIGN_ERROR;
+	}
+
+	dnssec_binary_t bin_raw = binary_from_datum(&raw);
+
+	return ctx->functions->x509_to_dnssec(ctx, &bin_raw, signature);
+}
+
+_public_
+int dnssec_sign_verify(dnssec_sign_ctx_t *ctx, bool sign_cmp, const dnssec_binary_t *signature)
+{
+	if (!ctx || !signature) {
+		return DNSSEC_EINVAL;
+	}
+
+	if (sign_cmp && dnssec_key_can_sign(ctx->key)) {
+		dnssec_binary_t sign = { 0 };
+		int ret = dnssec_sign_write(ctx, DNSSEC_SIGN_REPRODUCIBLE, &sign);
+		if (ret == KNOT_EOK) {
+			ret = dnssec_binary_cmp(&sign, signature)
+			      ? DNSSEC_INVALID_SIGNATURE
+			      : DNSSEC_EOK;
+		}
+		dnssec_binary_free(&sign);
+		return ret;
+	}
+
+	if (!dnssec_key_can_verify(ctx->key)) {
+		return DNSSEC_NO_PUBLIC_KEY;
+	}
+
+	gnutls_datum_t data = {
+		.data = vpool_get_buf(&ctx->buffer),
+		.size = vpool_get_length(&ctx->buffer)
+	};
+
+	_cleanup_binary_ dnssec_binary_t bin_raw = { 0 };
+	int result = ctx->functions->dnssec_to_x509(ctx, signature, &bin_raw);
+	if (result != DNSSEC_EOK) {
+		return result;
+	}
+
+	gnutls_datum_t raw = binary_to_datum(&bin_raw);
+
+	assert(ctx->key->public_key);
+	result = gnutls_pubkey_verify_data2(ctx->key->public_key,
+					    ctx->sign_algorithm,
+					    0, &data, &raw);
+	if (result == GNUTLS_E_PK_SIG_VERIFY_FAILED) {
+		return DNSSEC_INVALID_SIGNATURE;
+	} else if (result < 0) {
+		return DNSSEC_ERROR;
+	}
+
+	return DNSSEC_EOK;
+}