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/* $OpenBSD: ssh-ed25519-sk.c,v 1.6 2020/10/18 11:32:02 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 */
#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"
int
ssh_ed25519_sk_verify(const struct sshkey *key,
const u_char *signature, size_t signaturelen,
const u_char *data, size_t datalen, 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 ||
signature == NULL || signaturelen == 0)
return SSH_ERR_INVALID_ARGUMENT;
if ((b = sshbuf_from(signature, signaturelen)) == 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, datalen,
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;
}
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