1 /* $OpenBSD: ssh-ed25519-sk.c,v 1.6 2020/10/18 11:32:02 djm Exp $ */ 2 /* 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 */ 17 18 /* #define DEBUG_SK 1 */ 19 20 #include "includes.h" 21 22 #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 38 int 39 ssh_ed25519_sk_verify(const struct sshkey *key, 40 const u_char *signature, size_t signaturelen, 41 const u_char *data, size_t datalen, u_int compat, 42 struct sshkey_sig_details **detailsp) 43 { 44 struct sshbuf *b = NULL; 45 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; 58 struct sshkey_sig_details *details = NULL; 59 60 if (detailsp != NULL) 61 *detailsp = NULL; 62 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 || 72 sshbuf_get_string_direct(b, &sigblob, &len) != 0 || 73 sshbuf_get_u8(b, &sig_flags) != 0 || 74 sshbuf_get_u32(b, &sig_counter) != 0) { 75 r = SSH_ERR_INVALID_FORMAT; 76 goto out; 77 } 78 #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 86 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 } 105 #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 111 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; 117 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 } 129 #ifdef DEBUG_SK 130 fprintf(stderr, "%s: signed buf:\n", __func__); 131 sshbuf_dump(encoded, stderr); 132 #endif 133 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_f("crypto_sign_ed25519_open failed: %d", ret); 143 } 144 if (ret != 0 || mlen != smlen - len) { 145 r = SSH_ERR_SIGNATURE_INVALID; 146 goto out; 147 } 148 /* XXX compare 'm' and 'sm + len' ? */ 149 /* success */ 150 r = 0; 151 if (detailsp != NULL) { 152 *detailsp = details; 153 details = NULL; 154 } 155 out: 156 if (m != NULL) 157 freezero(m, smlen); /* NB mlen may be invalid if r != 0 */ 158 sshkey_sig_details_free(details); 159 sshbuf_free(b); 160 sshbuf_free(encoded); 161 free(ktype); 162 return r; 163 } 164