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kex: Add sntrup761x25519-sha512@openssh.com.

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All of the initial work was done by Simon. Jakub cleaned up the
formatting issues, resolved the padding of bignum to match specs
and be interoperable with OpenSSH (and few more minor details).

Closes: #194.

Signed-off-by: Simon Josefsson <simon@josefsson.org>
Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
Reviewed-by: Sahana Prasad <sahana@redhat.com>
This commit is contained in:
Simon Josefsson
2023-08-02 11:39:48 +02:00
committed by Jakub Jelen
parent 3468cc0dc5
commit 4becc8eb82
16 changed files with 1771 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

52
src/kex.c
View File

@@ -40,6 +40,7 @@
#include "libssh/ssh2.h"
#include "libssh/string.h"
#include "libssh/curve25519.h"
#include "libssh/sntrup761.h"
#include "libssh/knownhosts.h"
#include "libssh/misc.h"
#include "libssh/pki.h"
@@ -95,6 +96,12 @@
#define CURVE25519 ""
#endif /* HAVE_CURVE25519 */
#ifdef HAVE_SNTRUP761
#define SNTRUP761X25519 "sntrup761x25519-sha512@openssh.com,"
#else
#define SNTRUP761X25519 ""
#endif /* HAVE_SNTRUP761 */
#ifdef HAVE_ECC
#define ECDH "ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,"
#define EC_HOSTKEYS "ecdsa-sha2-nistp521," \
@@ -159,6 +166,7 @@
#define DEFAULT_KEY_EXCHANGE \
CURVE25519 \
SNTRUP761X25519 \
ECDH \
"diffie-hellman-group18-sha512,diffie-hellman-group16-sha512," \
GEX_SHA256 \
@@ -894,6 +902,8 @@ kex_select_kex_type(const char *kex)
return SSH_KEX_CURVE25519_SHA256_LIBSSH_ORG;
} else if (strcmp(kex, "curve25519-sha256") == 0) {
return SSH_KEX_CURVE25519_SHA256;
} else if (strcmp(kex, "sntrup761x25519-sha512@openssh.com") == 0) {
return SSH_KEX_SNTRUP761X25519_SHA512_OPENSSH_COM;
}
/* should not happen. We should be getting only valid names at this stage */
return 0;
@@ -933,6 +943,11 @@ static void revert_kex_callbacks(ssh_session session)
case SSH_KEX_CURVE25519_SHA256_LIBSSH_ORG:
ssh_client_curve25519_remove_callbacks(session);
break;
#endif
#ifdef HAVE_SNTRUP761
case SSH_KEX_SNTRUP761X25519_SHA512_OPENSSH_COM:
ssh_client_sntrup761x25519_remove_callbacks(session);
break;
#endif
}
}
@@ -1475,8 +1490,35 @@ int ssh_make_sessionid(ssh_session session)
}
break;
#endif /* HAVE_CURVE25519 */
#ifdef HAVE_SNTRUP761
case SSH_KEX_SNTRUP761X25519_SHA512_OPENSSH_COM:
rc = ssh_buffer_pack(buf,
"dPPdPP",
SNTRUP761_PUBLICKEY_SIZE + CURVE25519_PUBKEY_SIZE,
(size_t)SNTRUP761_PUBLICKEY_SIZE,
session->next_crypto->sntrup761_client_pubkey,
(size_t)CURVE25519_PUBKEY_SIZE,
session->next_crypto->curve25519_client_pubkey,
SNTRUP761_CIPHERTEXT_SIZE + CURVE25519_PUBKEY_SIZE,
(size_t)SNTRUP761_CIPHERTEXT_SIZE,
session->next_crypto->sntrup761_ciphertext,
(size_t)CURVE25519_PUBKEY_SIZE,
session->next_crypto->curve25519_server_pubkey);
if (rc != SSH_OK) {
goto error;
}
break;
#endif /* HAVE_SNTRUP761 */
}
if (session->next_crypto->kex_type == SSH_KEX_SNTRUP761X25519_SHA512_OPENSSH_COM) {
rc = ssh_buffer_pack(buf,
"F",
session->next_crypto->shared_secret,
SHA512_DIGEST_LEN);
} else {
rc = ssh_buffer_pack(buf, "B", session->next_crypto->shared_secret);
}
rc = ssh_buffer_pack(buf, "B", session->next_crypto->shared_secret);
if (rc != SSH_OK) {
goto error;
}
@@ -1532,6 +1574,7 @@ int ssh_make_sessionid(ssh_session session)
case SSH_KEX_DH_GROUP16_SHA512:
case SSH_KEX_DH_GROUP18_SHA512:
case SSH_KEX_ECDH_SHA2_NISTP521:
case SSH_KEX_SNTRUP761X25519_SHA512_OPENSSH_COM:
session->next_crypto->digest_len = SHA512_DIGEST_LENGTH;
session->next_crypto->digest_type = SSH_KDF_SHA512;
session->next_crypto->secret_hash = malloc(session->next_crypto->digest_len);
@@ -1668,7 +1711,12 @@ int ssh_generate_session_keys(ssh_session session)
size_t intkey_srv_to_cli_len = 0;
int rc = -1;
k_string = ssh_make_bignum_string(crypto->shared_secret);
if (session->next_crypto->kex_type == SSH_KEX_SNTRUP761X25519_SHA512_OPENSSH_COM) {
k_string = ssh_make_padded_bignum_string(crypto->shared_secret,
SHA512_DIGEST_LEN);
} else {
k_string = ssh_make_bignum_string(crypto->shared_secret);
}
if (k_string == NULL) {
ssh_set_error_oom(session);
goto error;