1 /* $NetBSD: ssh-ed25519-sk.c,v 1.4 2021/03/05 17:47:16 christos Exp $ */ 2 /* $OpenBSD: ssh-ed25519-sk.c,v 1.6 2020/10/18 11:32:02 djm Exp $ */ 3 4 /* 5 * Copyright (c) 2019 Markus Friedl. All rights reserved. 6 * 7 * Permission to use, copy, modify, and distribute this software for any 8 * purpose with or without fee is hereby granted, provided that the above 9 * copyright notice and this permission notice appear in all copies. 10 * 11 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 12 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 13 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 14 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 17 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 18 */ 19 #include "includes.h" 20 __RCSID("$NetBSD: ssh-ed25519-sk.c,v 1.4 2021/03/05 17:47:16 christos Exp $"); 21 22 /* #define DEBUG_SK 1 */ 23 24 #define SSHKEY_INTERNAL 25 #include <sys/types.h> 26 #include <limits.h> 27 28 #include "crypto_api.h" 29 30 #include <string.h> 31 #include <stdarg.h> 32 33 #include "log.h" 34 #include "sshbuf.h" 35 #include "sshkey.h" 36 #include "ssherr.h" 37 #include "ssh.h" 38 #include "digest.h" 39 40 int 41 ssh_ed25519_sk_verify(const struct sshkey *key, 42 const u_char *signature, size_t signaturelen, 43 const u_char *data, size_t datalen, u_int compat, 44 struct sshkey_sig_details **detailsp) 45 { 46 struct sshbuf *b = NULL; 47 struct sshbuf *encoded = NULL; 48 char *ktype = NULL; 49 const u_char *sigblob; 50 const u_char *sm; 51 u_char *m = NULL; 52 u_char apphash[32]; 53 u_char msghash[32]; 54 u_char sig_flags; 55 u_int sig_counter; 56 size_t len; 57 unsigned long long smlen = 0, mlen = 0; 58 int r = SSH_ERR_INTERNAL_ERROR; 59 int ret; 60 struct sshkey_sig_details *details = NULL; 61 62 if (detailsp != NULL) 63 *detailsp = NULL; 64 65 if (key == NULL || 66 sshkey_type_plain(key->type) != KEY_ED25519_SK || 67 key->ed25519_pk == NULL || 68 signature == NULL || signaturelen == 0) 69 return SSH_ERR_INVALID_ARGUMENT; 70 71 if ((b = sshbuf_from(signature, signaturelen)) == NULL) 72 return SSH_ERR_ALLOC_FAIL; 73 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 || 74 sshbuf_get_string_direct(b, &sigblob, &len) != 0 || 75 sshbuf_get_u8(b, &sig_flags) != 0 || 76 sshbuf_get_u32(b, &sig_counter) != 0) { 77 r = SSH_ERR_INVALID_FORMAT; 78 goto out; 79 } 80 #ifdef DEBUG_SK 81 fprintf(stderr, "%s: data:\n", __func__); 82 /* sshbuf_dump_data(data, datalen, stderr); */ 83 fprintf(stderr, "%s: sigblob:\n", __func__); 84 sshbuf_dump_data(sigblob, len, stderr); 85 fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n", 86 __func__, sig_flags, sig_counter); 87 #endif 88 if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) { 89 r = SSH_ERR_KEY_TYPE_MISMATCH; 90 goto out; 91 } 92 if (sshbuf_len(b) != 0) { 93 r = SSH_ERR_UNEXPECTED_TRAILING_DATA; 94 goto out; 95 } 96 if (len > crypto_sign_ed25519_BYTES) { 97 r = SSH_ERR_INVALID_FORMAT; 98 goto out; 99 } 100 if (ssh_digest_memory(SSH_DIGEST_SHA256, key->sk_application, 101 strlen(key->sk_application), apphash, sizeof(apphash)) != 0 || 102 ssh_digest_memory(SSH_DIGEST_SHA256, data, datalen, 103 msghash, sizeof(msghash)) != 0) { 104 r = SSH_ERR_INVALID_ARGUMENT; 105 goto out; 106 } 107 #ifdef DEBUG_SK 108 fprintf(stderr, "%s: hashed application:\n", __func__); 109 sshbuf_dump_data(apphash, sizeof(apphash), stderr); 110 fprintf(stderr, "%s: hashed message:\n", __func__); 111 sshbuf_dump_data(msghash, sizeof(msghash), stderr); 112 #endif 113 if ((details = calloc(1, sizeof(*details))) == NULL) { 114 r = SSH_ERR_ALLOC_FAIL; 115 goto out; 116 } 117 details->sk_counter = sig_counter; 118 details->sk_flags = sig_flags; 119 if ((encoded = sshbuf_new()) == NULL) { 120 r = SSH_ERR_ALLOC_FAIL; 121 goto out; 122 } 123 if (sshbuf_put(encoded, sigblob, len) != 0 || 124 sshbuf_put(encoded, apphash, sizeof(apphash)) != 0 || 125 sshbuf_put_u8(encoded, sig_flags) != 0 || 126 sshbuf_put_u32(encoded, sig_counter) != 0 || 127 sshbuf_put(encoded, msghash, sizeof(msghash)) != 0) { 128 r = SSH_ERR_ALLOC_FAIL; 129 goto out; 130 } 131 #ifdef DEBUG_SK 132 fprintf(stderr, "%s: signed buf:\n", __func__); 133 sshbuf_dump(encoded, stderr); 134 #endif 135 sm = sshbuf_ptr(encoded); 136 smlen = sshbuf_len(encoded); 137 mlen = smlen; 138 if ((m = malloc(smlen)) == NULL) { 139 r = SSH_ERR_ALLOC_FAIL; 140 goto out; 141 } 142 if ((ret = crypto_sign_ed25519_open(m, &mlen, sm, smlen, 143 key->ed25519_pk)) != 0) { 144 debug2_f("crypto_sign_ed25519_open failed: %d", ret); 145 } 146 if (ret != 0 || mlen != smlen - len) { 147 r = SSH_ERR_SIGNATURE_INVALID; 148 goto out; 149 } 150 /* XXX compare 'm' and 'sm + len' ? */ 151 /* success */ 152 r = 0; 153 if (detailsp != NULL) { 154 *detailsp = details; 155 details = NULL; 156 } 157 out: 158 if (m != NULL) 159 freezero(m, smlen); /* NB mlen may be invalid if r != 0 */ 160 sshkey_sig_details_free(details); 161 sshbuf_free(b); 162 sshbuf_free(encoded); 163 free(ktype); 164 return r; 165 } 166