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- /* $OpenBSD: ssh-ed25519-sk.c,v 1.15 2022/10/28 00:44:44 djm Exp $ */
- /*
- * Copyright (c) 2019 Markus Friedl. All rights reserved.
- *
- * Permission to use, copy, modify, and distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice appear in all copies.
- *
- * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
- * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
- * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
- * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
- * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
- * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
- */
-
- /* #define DEBUG_SK 1 */
-
- #include "includes.h"
-
- #define SSHKEY_INTERNAL
- #include <sys/types.h>
- #include <limits.h>
-
- #include "crypto_api.h"
-
- #include <string.h>
- #include <stdarg.h>
-
- #include "log.h"
- #include "sshbuf.h"
- #include "sshkey.h"
- #include "ssherr.h"
- #include "ssh.h"
- #include "digest.h"
-
- /* Reuse some ED25519 internals */
- extern struct sshkey_impl_funcs sshkey_ed25519_funcs;
-
- static void
- ssh_ed25519_sk_cleanup(struct sshkey *k)
- {
- sshkey_sk_cleanup(k);
- sshkey_ed25519_funcs.cleanup(k);
- }
-
- static int
- ssh_ed25519_sk_equal(const struct sshkey *a, const struct sshkey *b)
- {
- if (!sshkey_sk_fields_equal(a, b))
- return 0;
- if (!sshkey_ed25519_funcs.equal(a, b))
- return 0;
- return 1;
- }
-
- static int
- ssh_ed25519_sk_serialize_public(const struct sshkey *key, struct sshbuf *b,
- enum sshkey_serialize_rep opts)
- {
- int r;
-
- if ((r = sshkey_ed25519_funcs.serialize_public(key, b, opts)) != 0)
- return r;
- if ((r = sshkey_serialize_sk(key, b)) != 0)
- return r;
-
- return 0;
- }
-
- static int
- ssh_ed25519_sk_serialize_private(const struct sshkey *key, struct sshbuf *b,
- enum sshkey_serialize_rep opts)
- {
- int r;
-
- if ((r = sshkey_ed25519_funcs.serialize_public(key, b, opts)) != 0)
- return r;
- if ((r = sshkey_serialize_private_sk(key, b)) != 0)
- return r;
-
- return 0;
- }
-
- static int
- ssh_ed25519_sk_copy_public(const struct sshkey *from, struct sshkey *to)
- {
- int r;
-
- if ((r = sshkey_ed25519_funcs.copy_public(from, to)) != 0)
- return r;
- if ((r = sshkey_copy_public_sk(from, to)) != 0)
- return r;
- return 0;
- }
-
- static int
- ssh_ed25519_sk_deserialize_public(const char *ktype, struct sshbuf *b,
- struct sshkey *key)
- {
- int r;
-
- if ((r = sshkey_ed25519_funcs.deserialize_public(ktype, b, key)) != 0)
- return r;
- if ((r = sshkey_deserialize_sk(b, key)) != 0)
- return r;
- return 0;
- }
-
- static int
- ssh_ed25519_sk_deserialize_private(const char *ktype, struct sshbuf *b,
- struct sshkey *key)
- {
- int r;
-
- if ((r = sshkey_ed25519_funcs.deserialize_public(ktype, b, key)) != 0)
- return r;
- if ((r = sshkey_private_deserialize_sk(b, key)) != 0)
- return r;
- return 0;
- }
-
- static int
- ssh_ed25519_sk_verify(const struct sshkey *key,
- const u_char *sig, size_t siglen,
- const u_char *data, size_t dlen, const char *alg, u_int compat,
- struct sshkey_sig_details **detailsp)
- {
- struct sshbuf *b = NULL;
- struct sshbuf *encoded = NULL;
- char *ktype = NULL;
- const u_char *sigblob;
- const u_char *sm;
- u_char *m = NULL;
- u_char apphash[32];
- u_char msghash[32];
- u_char sig_flags;
- u_int sig_counter;
- size_t len;
- unsigned long long smlen = 0, mlen = 0;
- int r = SSH_ERR_INTERNAL_ERROR;
- int ret;
- struct sshkey_sig_details *details = NULL;
-
- if (detailsp != NULL)
- *detailsp = NULL;
-
- if (key == NULL ||
- sshkey_type_plain(key->type) != KEY_ED25519_SK ||
- key->ed25519_pk == NULL ||
- sig == NULL || siglen == 0)
- return SSH_ERR_INVALID_ARGUMENT;
-
- if ((b = sshbuf_from(sig, siglen)) == NULL)
- return SSH_ERR_ALLOC_FAIL;
- if (sshbuf_get_cstring(b, &ktype, NULL) != 0 ||
- sshbuf_get_string_direct(b, &sigblob, &len) != 0 ||
- sshbuf_get_u8(b, &sig_flags) != 0 ||
- sshbuf_get_u32(b, &sig_counter) != 0) {
- r = SSH_ERR_INVALID_FORMAT;
- goto out;
- }
- #ifdef DEBUG_SK
- fprintf(stderr, "%s: data:\n", __func__);
- /* sshbuf_dump_data(data, datalen, stderr); */
- fprintf(stderr, "%s: sigblob:\n", __func__);
- sshbuf_dump_data(sigblob, len, stderr);
- fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n",
- __func__, sig_flags, sig_counter);
- #endif
- if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) {
- r = SSH_ERR_KEY_TYPE_MISMATCH;
- goto out;
- }
- if (sshbuf_len(b) != 0) {
- r = SSH_ERR_UNEXPECTED_TRAILING_DATA;
- goto out;
- }
- if (len > crypto_sign_ed25519_BYTES) {
- r = SSH_ERR_INVALID_FORMAT;
- goto out;
- }
- if (ssh_digest_memory(SSH_DIGEST_SHA256, key->sk_application,
- strlen(key->sk_application), apphash, sizeof(apphash)) != 0 ||
- ssh_digest_memory(SSH_DIGEST_SHA256, data, dlen,
- msghash, sizeof(msghash)) != 0) {
- r = SSH_ERR_INVALID_ARGUMENT;
- goto out;
- }
- #ifdef DEBUG_SK
- fprintf(stderr, "%s: hashed application:\n", __func__);
- sshbuf_dump_data(apphash, sizeof(apphash), stderr);
- fprintf(stderr, "%s: hashed message:\n", __func__);
- sshbuf_dump_data(msghash, sizeof(msghash), stderr);
- #endif
- if ((details = calloc(1, sizeof(*details))) == NULL) {
- r = SSH_ERR_ALLOC_FAIL;
- goto out;
- }
- details->sk_counter = sig_counter;
- details->sk_flags = sig_flags;
- if ((encoded = sshbuf_new()) == NULL) {
- r = SSH_ERR_ALLOC_FAIL;
- goto out;
- }
- if (sshbuf_put(encoded, sigblob, len) != 0 ||
- sshbuf_put(encoded, apphash, sizeof(apphash)) != 0 ||
- sshbuf_put_u8(encoded, sig_flags) != 0 ||
- sshbuf_put_u32(encoded, sig_counter) != 0 ||
- sshbuf_put(encoded, msghash, sizeof(msghash)) != 0) {
- r = SSH_ERR_ALLOC_FAIL;
- goto out;
- }
- #ifdef DEBUG_SK
- fprintf(stderr, "%s: signed buf:\n", __func__);
- sshbuf_dump(encoded, stderr);
- #endif
- sm = sshbuf_ptr(encoded);
- smlen = sshbuf_len(encoded);
- mlen = smlen;
- if ((m = malloc(smlen)) == NULL) {
- r = SSH_ERR_ALLOC_FAIL;
- goto out;
- }
- if ((ret = crypto_sign_ed25519_open(m, &mlen, sm, smlen,
- key->ed25519_pk)) != 0) {
- debug2_f("crypto_sign_ed25519_open failed: %d", ret);
- }
- if (ret != 0 || mlen != smlen - len) {
- r = SSH_ERR_SIGNATURE_INVALID;
- goto out;
- }
- /* XXX compare 'm' and 'sm + len' ? */
- /* success */
- r = 0;
- if (detailsp != NULL) {
- *detailsp = details;
- details = NULL;
- }
- out:
- if (m != NULL)
- freezero(m, smlen); /* NB mlen may be invalid if r != 0 */
- sshkey_sig_details_free(details);
- sshbuf_free(b);
- sshbuf_free(encoded);
- free(ktype);
- return r;
- }
-
- static const struct sshkey_impl_funcs sshkey_ed25519_sk_funcs = {
- /* .size = */ NULL,
- /* .alloc = */ NULL,
- /* .cleanup = */ ssh_ed25519_sk_cleanup,
- /* .equal = */ ssh_ed25519_sk_equal,
- /* .ssh_serialize_public = */ ssh_ed25519_sk_serialize_public,
- /* .ssh_deserialize_public = */ ssh_ed25519_sk_deserialize_public,
- /* .ssh_serialize_private = */ ssh_ed25519_sk_serialize_private,
- /* .ssh_deserialize_private = */ ssh_ed25519_sk_deserialize_private,
- /* .generate = */ NULL,
- /* .copy_public = */ ssh_ed25519_sk_copy_public,
- /* .sign = */ NULL,
- /* .verify = */ ssh_ed25519_sk_verify,
- };
-
- const struct sshkey_impl sshkey_ed25519_sk_impl = {
- /* .name = */ "sk-ssh-ed25519@openssh.com",
- /* .shortname = */ "ED25519-SK",
- /* .sigalg = */ NULL,
- /* .type = */ KEY_ED25519_SK,
- /* .nid = */ 0,
- /* .cert = */ 0,
- /* .sigonly = */ 0,
- /* .keybits = */ 256,
- /* .funcs = */ &sshkey_ed25519_sk_funcs,
- };
-
- const struct sshkey_impl sshkey_ed25519_sk_cert_impl = {
- /* .name = */ "sk-ssh-ed25519-cert-v01@openssh.com",
- /* .shortname = */ "ED25519-SK-CERT",
- /* .sigalg = */ NULL,
- /* .type = */ KEY_ED25519_SK_CERT,
- /* .nid = */ 0,
- /* .cert = */ 1,
- /* .sigonly = */ 0,
- /* .keybits = */ 256,
- /* .funcs = */ &sshkey_ed25519_sk_funcs,
- };
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