strongswan/src/libstrongswan/plugins/botan/botan_ec_public_key.c

/*
 * Copyright (C) 2018 René Korthaus
 * Copyright (C) 2018 Konstantinos Kolelis
 * Rohde & Schwarz Cybersecurity GmbH
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "botan_ec_public_key.h"

#include <botan/build.h>

#ifdef BOTAN_HAS_ECDSA

#include <asn1/asn1.h>
#include <asn1/asn1_parser.h>

#include <utils/debug.h>

#include <botan/ffi.h>

typedef struct private_botan_ec_public_key_t private_botan_ec_public_key_t;

/**
 * Private data structure with signing context.
 */
struct private_botan_ec_public_key_t {
	/**
	 * Public interface for this signer
	 */
	botan_ec_public_key_t public;

	/**
	 * Botan ec public key
	 */
	botan_pubkey_t key;

	/**
	 * Reference counter
	 */
	refcount_t ref;
};

#define SIG_FORMAT_IEEE_1363 0
#define SIG_FORMAT_DER_SEQUENCE 1

/**
 * Verification of a DER encoded signature as in RFC 3279 or as in RFC 4754
 */
static bool verify_signature(private_botan_ec_public_key_t *this,
	const char* hash_and_padding, int signature_format, size_t keylen,
	chunk_t data, chunk_t signature)
{
	chunk_t sig;

	if (signature_format == SIG_FORMAT_DER_SEQUENCE)
	{
		/*
		 * botan requires a signature in IEEE 1363 format (r||s)
		 * re-encode from ASN.1 sequence of two integers r,s
		 */
		chunk_t parse, r, s;
		parse = signature;

		if (asn1_unwrap(&parse, &parse) != ASN1_SEQUENCE
		    || asn1_unwrap(&parse, &r) != ASN1_INTEGER
		    || asn1_unwrap(&parse, &s) != ASN1_INTEGER)
		{
			return FALSE;
		}

		r = chunk_skip_zero(r);
		s = chunk_skip_zero(s);

		/*
		 * r and s must be of size m_order.bytes()/2 each
		 */
		if (r.len > keylen || s.len > keylen)
		{
			return FALSE;
		}

		sig = chunk_alloca(2 * keylen);
		memset(sig.ptr, 0, sig.len);
		memcpy(sig.ptr + (keylen - r.len), r.ptr, r.len);
		memcpy(sig.ptr + keylen + (keylen - s.len), s.ptr, s.len);
	}
	else
	{
		sig.ptr = signature.ptr;
		sig.len = signature.len;
	}

	{
		botan_pk_op_verify_t verify_op;
		bool valid = FALSE;

		if (botan_pk_op_verify_create(&verify_op, this->key, hash_and_padding,
									  0))
		{
			return FALSE;
		}

		if (botan_pk_op_verify_update(verify_op, data.ptr, data.len))
		{
			botan_pk_op_verify_destroy(verify_op);
			return FALSE;
		}

		valid = !(botan_pk_op_verify_finish(verify_op, sig.ptr, sig.len));

		botan_pk_op_verify_destroy(verify_op);

		return valid;
	}
}

METHOD(public_key_t, get_type, key_type_t,
	private_botan_ec_public_key_t *this)
{
	return KEY_ECDSA;
}

METHOD(public_key_t, get_keysize, int,
	private_botan_ec_public_key_t *this)
{
	botan_mp_t p;
	if(botan_mp_init(&p))
	{
		return 0;
	}

	if(botan_pubkey_get_field(p, this->key, "p"))
	{
		botan_mp_destroy(p);
		return 0;
	}

	size_t bits = 0;
	if(botan_mp_num_bits(p, &bits))
	{
		botan_mp_destroy(p);
		return 0;
	}

	botan_mp_destroy(p);
	return bits;
}

METHOD(public_key_t, verify, bool,
	private_botan_ec_public_key_t *this, signature_scheme_t scheme,
	void *params, chunk_t data, chunk_t signature)
{
	size_t keylen = (get_keysize(this) + 7) / 8;
	const char *hash_and_padding;
	int sig_format;

	switch (scheme)
	{
		case SIGN_ECDSA_WITH_NULL:
			/* r||s -> Botan::IEEE_1363, data is the hash already */
			hash_and_padding = "Raw";
			sig_format = SIG_FORMAT_IEEE_1363;
			break;
		case SIGN_ECDSA_WITH_SHA1_DER:
			/* DER SEQUENCE of two INTEGERS r,s -> Botan::DER_SEQUENCE */
			hash_and_padding = "EMSA1(SHA-1)";
			sig_format = SIG_FORMAT_DER_SEQUENCE;
			break;
		case SIGN_ECDSA_WITH_SHA256_DER:
			hash_and_padding = "EMSA1(SHA-256)";
			sig_format = SIG_FORMAT_DER_SEQUENCE;
			break;
		case SIGN_ECDSA_WITH_SHA384_DER:
			hash_and_padding = "EMSA1(SHA-384)";
			sig_format = SIG_FORMAT_DER_SEQUENCE;
			break;
		case SIGN_ECDSA_WITH_SHA512_DER:
			hash_and_padding = "EMSA1(SHA-512)";
			sig_format = SIG_FORMAT_DER_SEQUENCE;
			break;
		case SIGN_ECDSA_256:
			/* r||s -> Botan::IEEE_1363 */
			hash_and_padding = "EMSA1(SHA-256)";
			sig_format = SIG_FORMAT_IEEE_1363;
			break;
		case SIGN_ECDSA_384:
			/* r||s -> Botan::IEEE_1363 */
			hash_and_padding = "EMSA1(SHA-384)";
			sig_format = SIG_FORMAT_IEEE_1363;
			break;
		case SIGN_ECDSA_521:
			/* r||s -> Botan::IEEE_1363 */
			hash_and_padding = "EMSA1(SHA-512)";
			sig_format = SIG_FORMAT_IEEE_1363;
			break;
		default:
			DBG1(DBG_LIB, "signature scheme %N not supported via botan",
				 signature_scheme_names, scheme);
			return FALSE;
	}

	return verify_signature(this, hash_and_padding,
							sig_format, keylen, data, signature);
}

METHOD(public_key_t, encrypt, bool,
	private_botan_ec_public_key_t *this, encryption_scheme_t scheme,
	chunk_t crypto, chunk_t *plain)
{
	DBG1(DBG_LIB, "EC public key encryption not implemented");
	return FALSE;
}

/**
 * Calculate fingerprint from a botan_pubkey_t, also used in ec private key.
 */
bool botan_ec_fingerprint(botan_pubkey_t *ec, cred_encoding_type_t type,
						  chunk_t *fp)
{
	hasher_t *hasher;
	chunk_t key;

	if (lib->encoding->get_cache(lib->encoding, type, ec, fp))
	{
		return TRUE;
	}

	switch (type)
	{
		case KEYID_PUBKEY_SHA1:
			/* subjectPublicKey -> use botan_pubkey_fingerprint() */
			{
				if (botan_pubkey_fingerprint(*ec, "SHA-1", NULL, &fp->len))
				{
					return FALSE;
				}

				*fp = chunk_alloc(fp->len);

				if (botan_pubkey_fingerprint(*ec, "SHA-1", fp->ptr, &fp->len))
				{
					chunk_free(fp);
					return FALSE;
				}

				break;
			}
		case KEYID_PUBKEY_INFO_SHA1:
			/* subjectPublicKeyInfo -> use botan_pubkey_export(), then hash */
			{
				if (botan_pubkey_export(*ec, NULL, &key.len,
										BOTAN_PRIVKEY_EXPORT_FLAG_DER))
				{
					return FALSE;
				}

				key = chunk_alloc(key.len);

				if (botan_pubkey_export(*ec, key.ptr, &key.len,
										BOTAN_PRIVKEY_EXPORT_FLAG_DER))
				{
					chunk_free(&key);
					return FALSE;
				}

				hasher = lib->crypto->create_hasher(lib->crypto, HASH_SHA1);
				if (!hasher || !hasher->allocate_hash(hasher, key, fp))
				{
					DBG1(DBG_LIB, "SHA1 hash algorithm not supported,"
						 " fingerprinting failed");
					DESTROY_IF(hasher);
					chunk_free(&key);
					return FALSE;
				}

				hasher->destroy(hasher);
				chunk_free(&key);
				break;
			}
		default:
			return FALSE;
	}

	lib->encoding->cache(lib->encoding, type, ec, *fp);
	return TRUE;
}

METHOD(public_key_t, get_fingerprint, bool,
	private_botan_ec_public_key_t *this, cred_encoding_type_t type,
	chunk_t *fingerprint)
{
	return botan_ec_fingerprint(&this->key, type, fingerprint);
}

METHOD(public_key_t, get_encoding, bool,
	private_botan_ec_public_key_t *this, cred_encoding_type_t type,
	chunk_t *encoding)
{
	bool success = TRUE;

	if (botan_pubkey_export(this->key, NULL, &encoding->len,
							BOTAN_PRIVKEY_EXPORT_FLAG_DER))
	{
		return FALSE;
	}

	*encoding = chunk_alloc(encoding->len);

	if (botan_pubkey_export(this->key, encoding->ptr, &encoding->len,
							BOTAN_PRIVKEY_EXPORT_FLAG_DER))
	{
		chunk_free(encoding);
		return FALSE;
	}

	if (type != PUBKEY_SPKI_ASN1_DER)
	{
		chunk_t asn1_encoding = *encoding;

		success = lib->encoding->encode(lib->encoding, type, NULL, encoding,
										CRED_PART_ECDSA_PUB_ASN1_DER,
										asn1_encoding, CRED_PART_END);
		chunk_free(&asn1_encoding);
	}

	return success;
}

METHOD(public_key_t, get_ref, public_key_t*,
	private_botan_ec_public_key_t *this)
{
	ref_get(&this->ref);
	return &this->public.key;
}

METHOD(public_key_t, destroy, void,
	private_botan_ec_public_key_t *this)
{
	if (ref_put(&this->ref))
	{
		botan_pubkey_destroy(this->key);
		free(this);
	}
}

/**
 * See header.
 */
botan_ec_public_key_t *botan_ec_public_key_load(key_type_t type, va_list args)
{
	private_botan_ec_public_key_t *this;
	chunk_t blob = chunk_empty;

	if (type != KEY_ECDSA)
	{
		return NULL;
	}

	while (TRUE)
	{
		switch (va_arg(args, builder_part_t))
		{
			case BUILD_BLOB_ASN1_DER:
				blob = va_arg(args, chunk_t);
				continue;
			case BUILD_END:
				break;
			default:
				return NULL;
		}
		break;
	}

	INIT(this,
		.public = {
			.key = {
				.get_type = _get_type,
				.verify = _verify,
				.encrypt = _encrypt,
				.get_keysize = _get_keysize,
				.equals = public_key_equals,
				.get_fingerprint = _get_fingerprint,
				.has_fingerprint = public_key_has_fingerprint,
				.get_encoding = _get_encoding,
				.get_ref = _get_ref,
				.destroy = _destroy,
			},
		},
		.ref = 1,
	);

	if (botan_pubkey_load(&this->key, blob.ptr, blob.len))
	{
		destroy(this);
		return NULL;
	}

	size_t namesize = 0;
	if (botan_pubkey_algo_name(this->key, NULL, &namesize) !=
							   BOTAN_FFI_ERROR_INSUFFICIENT_BUFFER_SPACE)
	{
		botan_pubkey_destroy(this->key);
		destroy(this);
		return NULL;
	}

	char* namebuf = malloc(namesize);
	if (botan_pubkey_algo_name(this->key, namebuf, &namesize))
	{
		free(namebuf);
		botan_pubkey_destroy(this->key);
		destroy(this);
		return NULL;
	}

	const char* algo_name = "ECDSA";
	if (!strneq(namebuf, algo_name, sizeof(algo_name)))
	{
		free(namebuf);
		botan_pubkey_destroy(this->key);
		destroy(this);
		return NULL;
	}
	free(namebuf);

	botan_rng_t rng;
	if (botan_rng_init(&rng, "user"))
	{
		return FALSE;
	}

	if (botan_pubkey_check_key(this->key, rng, BOTAN_CHECK_KEY_EXPENSIVE_TESTS))
	{
		DBG1(DBG_LIB, "public key failed key checks");
		botan_rng_destroy(rng);
		botan_pubkey_destroy(this->key);
		destroy(this);
		return NULL;
	}

	botan_rng_destroy(rng);
	return &this->public;
}

#endif