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Diffstat (limited to 'kexc25519.c')
| -rw-r--r-- | kexc25519.c | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/kexc25519.c b/kexc25519.c new file mode 100644 index 0000000..0897b8c --- /dev/null +++ b/kexc25519.c @@ -0,0 +1,133 @@ +/* $OpenBSD: kexc25519.c,v 1.10 2016/05/02 08:49:03 djm Exp $ */ +/* + * Copyright (c) 2001, 2013 Markus Friedl. All rights reserved. + * Copyright (c) 2010 Damien Miller. All rights reserved. + * Copyright (c) 2013 Aris Adamantiadis. 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 <signal.h> +#include <string.h> + +#include <openssl/bn.h> +#include <openssl/evp.h> + +#include "sshbuf.h" +#include "ssh2.h" +#include "sshkey.h" +#include "cipher.h" +#include "kex.h" +#include "log.h" +#include "digest.h" +#include "ssherr.h" + +extern int crypto_scalarmult_curve25519(u_char a[CURVE25519_SIZE], + const u_char b[CURVE25519_SIZE], const u_char c[CURVE25519_SIZE]) + __attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE))) + __attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE))) + __attribute__((__bounded__(__minbytes__, 3, CURVE25519_SIZE))); + +void +kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE]) +{ + static const u_char basepoint[CURVE25519_SIZE] = {9}; + + arc4random_buf(key, CURVE25519_SIZE); + crypto_scalarmult_curve25519(pub, key, basepoint); +} + +int +kexc25519_shared_key(const u_char key[CURVE25519_SIZE], + const u_char pub[CURVE25519_SIZE], struct sshbuf *out) +{ + u_char shared_key[CURVE25519_SIZE]; + int r; + + /* Check for all-zero public key */ + explicit_bzero(shared_key, CURVE25519_SIZE); + if (timingsafe_bcmp(pub, shared_key, CURVE25519_SIZE) == 0) + return SSH_ERR_KEY_INVALID_EC_VALUE; + + crypto_scalarmult_curve25519(shared_key, key, pub); +#ifdef DEBUG_KEXECDH + dump_digest("shared secret", shared_key, CURVE25519_SIZE); +#endif + sshbuf_reset(out); + r = sshbuf_put_bignum2_bytes(out, shared_key, CURVE25519_SIZE); + explicit_bzero(shared_key, CURVE25519_SIZE); + return r; +} + +int +kex_c25519_hash( + int hash_alg, + const char *client_version_string, + const char *server_version_string, + const u_char *ckexinit, size_t ckexinitlen, + const u_char *skexinit, size_t skexinitlen, + const u_char *serverhostkeyblob, size_t sbloblen, + const u_char client_dh_pub[CURVE25519_SIZE], + const u_char server_dh_pub[CURVE25519_SIZE], + const u_char *shared_secret, size_t secretlen, + u_char *hash, size_t *hashlen) +{ + struct sshbuf *b; + int r; + + if (*hashlen < ssh_digest_bytes(hash_alg)) + return SSH_ERR_INVALID_ARGUMENT; + if ((b = sshbuf_new()) == NULL) + return SSH_ERR_ALLOC_FAIL; + if ((r = sshbuf_put_cstring(b, client_version_string)) < 0 || + (r = sshbuf_put_cstring(b, server_version_string)) < 0 || + /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */ + (r = sshbuf_put_u32(b, ckexinitlen+1)) < 0 || + (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) < 0 || + (r = sshbuf_put(b, ckexinit, ckexinitlen)) < 0 || + (r = sshbuf_put_u32(b, skexinitlen+1)) < 0 || + (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) < 0 || + (r = sshbuf_put(b, skexinit, skexinitlen)) < 0 || + (r = sshbuf_put_string(b, serverhostkeyblob, sbloblen)) < 0 || + (r = sshbuf_put_string(b, client_dh_pub, CURVE25519_SIZE)) < 0 || + (r = sshbuf_put_string(b, server_dh_pub, CURVE25519_SIZE)) < 0 || + (r = sshbuf_put(b, shared_secret, secretlen)) < 0) { + sshbuf_free(b); + return r; + } +#ifdef DEBUG_KEX + sshbuf_dump(b, stderr); +#endif + if (ssh_digest_buffer(hash_alg, b, hash, *hashlen) != 0) { + sshbuf_free(b); + return SSH_ERR_LIBCRYPTO_ERROR; + } + sshbuf_free(b); + *hashlen = ssh_digest_bytes(hash_alg); +#ifdef DEBUG_KEX + dump_digest("hash", hash, *hashlen); +#endif + return 0; +} |