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Diffstat (limited to '')
| -rw-r--r-- | kexmlkem768x25519.c | 280 |
1 files changed, 280 insertions, 0 deletions
diff --git a/kexmlkem768x25519.c b/kexmlkem768x25519.c new file mode 100644 index 0000000..679446e --- /dev/null +++ b/kexmlkem768x25519.c @@ -0,0 +1,280 @@ +/* $OpenBSD: kexmlkem768x25519.c,v 1.1 2024/09/02 12:13:56 djm Exp $ */ +/* + * Copyright (c) 2023 Markus Friedl. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include "includes.h" + +#include <sys/types.h> + +#include <stdio.h> +#ifdef HAVE_STDINT_H +#include <stdint.h> +#endif +#include <stdbool.h> +#include <string.h> +#include <signal.h> + +#include "sshkey.h" +#include "kex.h" +#include "sshbuf.h" +#include "digest.h" +#include "ssherr.h" +#include "log.h" + +#ifdef USE_MLKEM768X25519 + +#include "libcrux_mlkem768_sha3.h" + +int +kex_kem_mlkem768x25519_keypair(struct kex *kex) +{ + struct sshbuf *buf = NULL; + u_char rnd[LIBCRUX_ML_KEM_KEY_PAIR_PRNG_LEN], *cp = NULL; + size_t need; + int r = SSH_ERR_INTERNAL_ERROR; + struct libcrux_mlkem768_keypair keypair; + + if ((buf = sshbuf_new()) == NULL) + return SSH_ERR_ALLOC_FAIL; + need = crypto_kem_mlkem768_PUBLICKEYBYTES + CURVE25519_SIZE; + if ((r = sshbuf_reserve(buf, need, &cp)) != 0) + goto out; + arc4random_buf(rnd, sizeof(rnd)); + keypair = libcrux_ml_kem_mlkem768_portable_generate_key_pair(rnd); + memcpy(cp, keypair.pk.value, crypto_kem_mlkem768_PUBLICKEYBYTES); + memcpy(kex->mlkem768_client_key, keypair.sk.value, + sizeof(kex->mlkem768_client_key)); +#ifdef DEBUG_KEXECDH + dump_digest("client public key mlkem768:", cp, + crypto_kem_mlkem768_PUBLICKEYBYTES); +#endif + cp += crypto_kem_mlkem768_PUBLICKEYBYTES; + kexc25519_keygen(kex->c25519_client_key, cp); +#ifdef DEBUG_KEXECDH + dump_digest("client public key c25519:", cp, CURVE25519_SIZE); +#endif + /* success */ + r = 0; + kex->client_pub = buf; + buf = NULL; + out: + explicit_bzero(&keypair, sizeof(keypair)); + explicit_bzero(rnd, sizeof(rnd)); + sshbuf_free(buf); + return r; +} + +int +kex_kem_mlkem768x25519_enc(struct kex *kex, + const struct sshbuf *client_blob, struct sshbuf **server_blobp, + struct sshbuf **shared_secretp) +{ + struct sshbuf *server_blob = NULL; + struct sshbuf *buf = NULL; + const u_char *client_pub; + u_char rnd[LIBCRUX_ML_KEM_ENC_PRNG_LEN]; + u_char server_pub[CURVE25519_SIZE], server_key[CURVE25519_SIZE]; + u_char hash[SSH_DIGEST_MAX_LENGTH]; + size_t need; + int r = SSH_ERR_INTERNAL_ERROR; + struct libcrux_mlkem768_enc_result enc; + struct libcrux_mlkem768_pk mlkem_pub; + + *server_blobp = NULL; + *shared_secretp = NULL; + memset(&mlkem_pub, 0, sizeof(mlkem_pub)); + + /* client_blob contains both KEM and ECDH client pubkeys */ + need = crypto_kem_mlkem768_PUBLICKEYBYTES + CURVE25519_SIZE; + if (sshbuf_len(client_blob) != need) { + r = SSH_ERR_SIGNATURE_INVALID; + goto out; + } + client_pub = sshbuf_ptr(client_blob); +#ifdef DEBUG_KEXECDH + dump_digest("client public key mlkem768:", client_pub, + crypto_kem_mlkem768_PUBLICKEYBYTES); + dump_digest("client public key 25519:", + client_pub + crypto_kem_mlkem768_PUBLICKEYBYTES, + CURVE25519_SIZE); +#endif + /* check public key validity */ + memcpy(mlkem_pub.value, client_pub, crypto_kem_mlkem768_PUBLICKEYBYTES); + if (!libcrux_ml_kem_mlkem768_portable_validate_public_key(&mlkem_pub)) { + r = SSH_ERR_SIGNATURE_INVALID; + goto out; + } + + /* allocate buffer for concatenation of KEM key and ECDH shared key */ + /* the buffer will be hashed and the result is the shared secret */ + if ((buf = sshbuf_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + /* allocate space for encrypted KEM key and ECDH pub key */ + if ((server_blob = sshbuf_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + /* generate and encrypt KEM key with client key */ + arc4random_buf(rnd, sizeof(rnd)); + enc = libcrux_ml_kem_mlkem768_portable_encapsulate(&mlkem_pub, rnd); + /* generate ECDH key pair, store server pubkey after ciphertext */ + kexc25519_keygen(server_key, server_pub); + if ((r = sshbuf_put(buf, enc.snd, sizeof(enc.snd))) != 0 || + (r = sshbuf_put(server_blob, enc.fst.value, sizeof(enc.fst.value))) != 0 || + (r = sshbuf_put(server_blob, server_pub, sizeof(server_pub))) != 0) + goto out; + /* append ECDH shared key */ + client_pub += crypto_kem_mlkem768_PUBLICKEYBYTES; + if ((r = kexc25519_shared_key_ext(server_key, client_pub, buf, 1)) < 0) + goto out; + if ((r = ssh_digest_buffer(kex->hash_alg, buf, hash, sizeof(hash))) != 0) + goto out; +#ifdef DEBUG_KEXECDH + dump_digest("server public key 25519:", server_pub, CURVE25519_SIZE); + dump_digest("server cipher text:", + enc.fst.value, sizeof(enc.fst.value)); + dump_digest("server kem key:", enc.snd, sizeof(enc.snd)); + dump_digest("concatenation of KEM key and ECDH shared key:", + sshbuf_ptr(buf), sshbuf_len(buf)); +#endif + /* string-encoded hash is resulting shared secret */ + sshbuf_reset(buf); + if ((r = sshbuf_put_string(buf, hash, + ssh_digest_bytes(kex->hash_alg))) != 0) + goto out; +#ifdef DEBUG_KEXECDH + dump_digest("encoded shared secret:", sshbuf_ptr(buf), sshbuf_len(buf)); +#endif + /* success */ + r = 0; + *server_blobp = server_blob; + *shared_secretp = buf; + server_blob = NULL; + buf = NULL; + out: + explicit_bzero(hash, sizeof(hash)); + explicit_bzero(server_key, sizeof(server_key)); + explicit_bzero(rnd, sizeof(rnd)); + explicit_bzero(&enc, sizeof(enc)); + sshbuf_free(server_blob); + sshbuf_free(buf); + return r; +} + +int +kex_kem_mlkem768x25519_dec(struct kex *kex, + const struct sshbuf *server_blob, struct sshbuf **shared_secretp) +{ + struct sshbuf *buf = NULL; + u_char mlkem_key[crypto_kem_mlkem768_BYTES]; + const u_char *ciphertext, *server_pub; + u_char hash[SSH_DIGEST_MAX_LENGTH]; + size_t need; + int r; + struct libcrux_mlkem768_sk mlkem_priv; + struct libcrux_mlkem768_ciphertext mlkem_ciphertext; + + *shared_secretp = NULL; + memset(&mlkem_priv, 0, sizeof(mlkem_priv)); + memset(&mlkem_ciphertext, 0, sizeof(mlkem_ciphertext)); + + need = crypto_kem_mlkem768_CIPHERTEXTBYTES + CURVE25519_SIZE; + if (sshbuf_len(server_blob) != need) { + r = SSH_ERR_SIGNATURE_INVALID; + goto out; + } + ciphertext = sshbuf_ptr(server_blob); + server_pub = ciphertext + crypto_kem_mlkem768_CIPHERTEXTBYTES; + /* hash concatenation of KEM key and ECDH shared key */ + if ((buf = sshbuf_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + memcpy(mlkem_priv.value, kex->mlkem768_client_key, + sizeof(kex->mlkem768_client_key)); + memcpy(mlkem_ciphertext.value, ciphertext, + sizeof(mlkem_ciphertext.value)); +#ifdef DEBUG_KEXECDH + dump_digest("server cipher text:", mlkem_ciphertext.value, + sizeof(mlkem_ciphertext.value)); + dump_digest("server public key c25519:", server_pub, CURVE25519_SIZE); +#endif + libcrux_ml_kem_mlkem768_portable_decapsulate(&mlkem_priv, + &mlkem_ciphertext, mlkem_key); + if ((r = sshbuf_put(buf, mlkem_key, sizeof(mlkem_key))) != 0) + goto out; + if ((r = kexc25519_shared_key_ext(kex->c25519_client_key, server_pub, + buf, 1)) < 0) + goto out; + if ((r = ssh_digest_buffer(kex->hash_alg, buf, + hash, sizeof(hash))) != 0) + goto out; +#ifdef DEBUG_KEXECDH + dump_digest("client kem key:", mlkem_key, sizeof(mlkem_key)); + dump_digest("concatenation of KEM key and ECDH shared key:", + sshbuf_ptr(buf), sshbuf_len(buf)); +#endif + sshbuf_reset(buf); + if ((r = sshbuf_put_string(buf, hash, + ssh_digest_bytes(kex->hash_alg))) != 0) + goto out; +#ifdef DEBUG_KEXECDH + dump_digest("encoded shared secret:", sshbuf_ptr(buf), sshbuf_len(buf)); +#endif + /* success */ + r = 0; + *shared_secretp = buf; + buf = NULL; + out: + explicit_bzero(hash, sizeof(hash)); + explicit_bzero(&mlkem_priv, sizeof(mlkem_priv)); + explicit_bzero(&mlkem_ciphertext, sizeof(mlkem_ciphertext)); + explicit_bzero(mlkem_key, sizeof(mlkem_key)); + sshbuf_free(buf); + return r; +} +#else /* USE_MLKEM768X25519 */ +int +kex_kem_mlkem768x25519_keypair(struct kex *kex) +{ + return SSH_ERR_SIGN_ALG_UNSUPPORTED; +} + +int +kex_kem_mlkem768x25519_enc(struct kex *kex, + const struct sshbuf *client_blob, struct sshbuf **server_blobp, + struct sshbuf **shared_secretp) +{ + return SSH_ERR_SIGN_ALG_UNSUPPORTED; +} + +int +kex_kem_mlkem768x25519_dec(struct kex *kex, + const struct sshbuf *server_blob, struct sshbuf **shared_secretp) +{ + return SSH_ERR_SIGN_ALG_UNSUPPORTED; +} +#endif /* USE_MLKEM768X25519 */ |