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djm@openbsd.orge0d38ae2019-11-26 03:04:27 +00001/* $OpenBSD: ssh-ed25519-sk.c,v 1.4 2019/11/26 03:04:27 djm Exp $ */
markus@openbsd.org7c096c42019-11-12 19:29:24 +00002/*
3 * Copyright (c) 2019 Markus Friedl. All rights reserved.
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
djm@openbsd.orge0d38ae2019-11-26 03:04:27 +000017
18/* #define DEBUG_SK 1 */
19
Darren Tuckera0989b62020-01-14 14:26:41 +110020#include "includes.h"
21
markus@openbsd.org7c096c42019-11-12 19:29:24 +000022#define SSHKEY_INTERNAL
23#include <sys/types.h>
24#include <limits.h>
25
26#include "crypto_api.h"
27
28#include <string.h>
29#include <stdarg.h>
30
31#include "log.h"
32#include "sshbuf.h"
33#include "sshkey.h"
34#include "ssherr.h"
35#include "ssh.h"
36#include "digest.h"
37
38int
39ssh_ed25519_sk_verify(const struct sshkey *key,
40 const u_char *signature, size_t signaturelen,
djm@openbsd.orgb7e74ea2019-11-25 00:51:37 +000041 const u_char *data, size_t datalen, u_int compat,
42 struct sshkey_sig_details **detailsp)
markus@openbsd.org7c096c42019-11-12 19:29:24 +000043{
44 struct sshbuf *b = NULL;
markus@openbsd.org7c096c42019-11-12 19:29:24 +000045 struct sshbuf *encoded = NULL;
46 char *ktype = NULL;
47 const u_char *sigblob;
48 const u_char *sm;
49 u_char *m = NULL;
50 u_char apphash[32];
51 u_char msghash[32];
52 u_char sig_flags;
53 u_int sig_counter;
54 size_t len;
55 unsigned long long smlen = 0, mlen = 0;
56 int r = SSH_ERR_INTERNAL_ERROR;
57 int ret;
djm@openbsd.orgb7e74ea2019-11-25 00:51:37 +000058 struct sshkey_sig_details *details = NULL;
59
60 if (detailsp != NULL)
61 *detailsp = NULL;
markus@openbsd.org7c096c42019-11-12 19:29:24 +000062
63 if (key == NULL ||
64 sshkey_type_plain(key->type) != KEY_ED25519_SK ||
65 key->ed25519_pk == NULL ||
66 signature == NULL || signaturelen == 0)
67 return SSH_ERR_INVALID_ARGUMENT;
68
69 if ((b = sshbuf_from(signature, signaturelen)) == NULL)
70 return SSH_ERR_ALLOC_FAIL;
71 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 ||
markus@openbsd.orgb556cc32019-11-12 19:34:40 +000072 sshbuf_get_string_direct(b, &sigblob, &len) != 0 ||
73 sshbuf_get_u8(b, &sig_flags) != 0 ||
74 sshbuf_get_u32(b, &sig_counter) != 0) {
markus@openbsd.org7c096c42019-11-12 19:29:24 +000075 r = SSH_ERR_INVALID_FORMAT;
76 goto out;
77 }
djm@openbsd.orge0d38ae2019-11-26 03:04:27 +000078#ifdef DEBUG_SK
79 fprintf(stderr, "%s: data:\n", __func__);
80 /* sshbuf_dump_data(data, datalen, stderr); */
81 fprintf(stderr, "%s: sigblob:\n", __func__);
82 sshbuf_dump_data(sigblob, len, stderr);
83 fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n",
84 __func__, sig_flags, sig_counter);
85#endif
markus@openbsd.org7c096c42019-11-12 19:29:24 +000086 if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) {
87 r = SSH_ERR_KEY_TYPE_MISMATCH;
88 goto out;
89 }
90 if (sshbuf_len(b) != 0) {
91 r = SSH_ERR_UNEXPECTED_TRAILING_DATA;
92 goto out;
93 }
94 if (len > crypto_sign_ed25519_BYTES) {
95 r = SSH_ERR_INVALID_FORMAT;
96 goto out;
97 }
98 if (ssh_digest_memory(SSH_DIGEST_SHA256, key->sk_application,
99 strlen(key->sk_application), apphash, sizeof(apphash)) != 0 ||
100 ssh_digest_memory(SSH_DIGEST_SHA256, data, datalen,
101 msghash, sizeof(msghash)) != 0) {
102 r = SSH_ERR_INVALID_ARGUMENT;
103 goto out;
104 }
djm@openbsd.orge0d38ae2019-11-26 03:04:27 +0000105#ifdef DEBUG_SK
106 fprintf(stderr, "%s: hashed application:\n", __func__);
107 sshbuf_dump_data(apphash, sizeof(apphash), stderr);
108 fprintf(stderr, "%s: hashed message:\n", __func__);
109 sshbuf_dump_data(msghash, sizeof(msghash), stderr);
110#endif
djm@openbsd.orgb7e74ea2019-11-25 00:51:37 +0000111 if ((details = calloc(1, sizeof(*details))) == NULL) {
112 r = SSH_ERR_ALLOC_FAIL;
113 goto out;
114 }
115 details->sk_counter = sig_counter;
116 details->sk_flags = sig_flags;
markus@openbsd.org7c096c42019-11-12 19:29:24 +0000117 if ((encoded = sshbuf_new()) == NULL) {
118 r = SSH_ERR_ALLOC_FAIL;
119 goto out;
120 }
121 if (sshbuf_put(encoded, sigblob, len) != 0 ||
122 sshbuf_put(encoded, apphash, sizeof(apphash)) != 0 ||
123 sshbuf_put_u8(encoded, sig_flags) != 0 ||
124 sshbuf_put_u32(encoded, sig_counter) != 0 ||
125 sshbuf_put(encoded, msghash, sizeof(msghash)) != 0) {
126 r = SSH_ERR_ALLOC_FAIL;
127 goto out;
128 }
djm@openbsd.orge0d38ae2019-11-26 03:04:27 +0000129#ifdef DEBUG_SK
130 fprintf(stderr, "%s: signed buf:\n", __func__);
131 sshbuf_dump(encoded, stderr);
132#endif
markus@openbsd.org7c096c42019-11-12 19:29:24 +0000133 sm = sshbuf_ptr(encoded);
134 smlen = sshbuf_len(encoded);
135 mlen = smlen;
136 if ((m = malloc(smlen)) == NULL) {
137 r = SSH_ERR_ALLOC_FAIL;
138 goto out;
139 }
140 if ((ret = crypto_sign_ed25519_open(m, &mlen, sm, smlen,
141 key->ed25519_pk)) != 0) {
142 debug2("%s: crypto_sign_ed25519_open failed: %d",
143 __func__, ret);
144 }
145 if (ret != 0 || mlen != smlen - len) {
146 r = SSH_ERR_SIGNATURE_INVALID;
147 goto out;
148 }
149 /* XXX compare 'm' and 'sm + len' ? */
150 /* success */
151 r = 0;
djm@openbsd.orgb7e74ea2019-11-25 00:51:37 +0000152 if (detailsp != NULL) {
153 *detailsp = details;
154 details = NULL;
155 }
markus@openbsd.org7c096c42019-11-12 19:29:24 +0000156 out:
157 if (m != NULL) {
158 explicit_bzero(m, smlen); /* NB mlen may be invalid if r != 0 */
159 free(m);
160 }
djm@openbsd.orgb7e74ea2019-11-25 00:51:37 +0000161 sshkey_sig_details_free(details);
markus@openbsd.org7c096c42019-11-12 19:29:24 +0000162 sshbuf_free(b);
markus@openbsd.org7c096c42019-11-12 19:29:24 +0000163 sshbuf_free(encoded);
164 free(ktype);
165 return r;
166}