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 #define SSHKEY_INTERNAL 21 #include <sys/types.h> 22 #include <limits.h> 23 24 #include "crypto_api.h" 25 26 #include <string.h> 27 #include <stdarg.h> 28 29 #include "log.h" 30 #include "sshbuf.h" 31 #include "sshkey.h" 32 #include "ssherr.h" 33 #include "ssh.h" 34 #include "digest.h" 35 36 int 37 ssh_ed25519_sk_verify(const struct sshkey *key, 38 const u_char *signature, size_t signaturelen, 39 const u_char *data, size_t datalen, u_int compat, 40 struct sshkey_sig_details **detailsp) 41 { 42 struct sshbuf *b = NULL; 43 struct sshbuf *encoded = NULL; 44 char *ktype = NULL; 45 const u_char *sigblob; 46 const u_char *sm; 47 u_char *m = NULL; 48 u_char apphash[32]; 49 u_char msghash[32]; 50 u_char sig_flags; 51 u_int sig_counter; 52 size_t len; 53 unsigned long long smlen = 0, mlen = 0; 54 int r = SSH_ERR_INTERNAL_ERROR; 55 int ret; 56 struct sshkey_sig_details *details = NULL; 57 58 if (detailsp != NULL) 59 *detailsp = NULL; 60 61 if (key == NULL || 62 sshkey_type_plain(key->type) != KEY_ED25519_SK || 63 key->ed25519_pk == NULL || 64 signature == NULL || signaturelen == 0) 65 return SSH_ERR_INVALID_ARGUMENT; 66 67 if ((b = sshbuf_from(signature, signaturelen)) == NULL) 68 return SSH_ERR_ALLOC_FAIL; 69 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 || 70 sshbuf_get_string_direct(b, &sigblob, &len) != 0 || 71 sshbuf_get_u8(b, &sig_flags) != 0 || 72 sshbuf_get_u32(b, &sig_counter) != 0) { 73 r = SSH_ERR_INVALID_FORMAT; 74 goto out; 75 } 76 #ifdef DEBUG_SK 77 fprintf(stderr, "%s: data:\n", __func__); 78 /* sshbuf_dump_data(data, datalen, stderr); */ 79 fprintf(stderr, "%s: sigblob:\n", __func__); 80 sshbuf_dump_data(sigblob, len, stderr); 81 fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n", 82 __func__, sig_flags, sig_counter); 83 #endif 84 if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) { 85 r = SSH_ERR_KEY_TYPE_MISMATCH; 86 goto out; 87 } 88 if (sshbuf_len(b) != 0) { 89 r = SSH_ERR_UNEXPECTED_TRAILING_DATA; 90 goto out; 91 } 92 if (len > crypto_sign_ed25519_BYTES) { 93 r = SSH_ERR_INVALID_FORMAT; 94 goto out; 95 } 96 if (ssh_digest_memory(SSH_DIGEST_SHA256, key->sk_application, 97 strlen(key->sk_application), apphash, sizeof(apphash)) != 0 || 98 ssh_digest_memory(SSH_DIGEST_SHA256, data, datalen, 99 msghash, sizeof(msghash)) != 0) { 100 r = SSH_ERR_INVALID_ARGUMENT; 101 goto out; 102 } 103 #ifdef DEBUG_SK 104 fprintf(stderr, "%s: hashed application:\n", __func__); 105 sshbuf_dump_data(apphash, sizeof(apphash), stderr); 106 fprintf(stderr, "%s: hashed message:\n", __func__); 107 sshbuf_dump_data(msghash, sizeof(msghash), stderr); 108 #endif 109 if ((details = calloc(1, sizeof(*details))) == NULL) { 110 r = SSH_ERR_ALLOC_FAIL; 111 goto out; 112 } 113 details->sk_counter = sig_counter; 114 details->sk_flags = sig_flags; 115 if ((encoded = sshbuf_new()) == NULL) { 116 r = SSH_ERR_ALLOC_FAIL; 117 goto out; 118 } 119 if (sshbuf_put(encoded, sigblob, len) != 0 || 120 sshbuf_put(encoded, apphash, sizeof(apphash)) != 0 || 121 sshbuf_put_u8(encoded, sig_flags) != 0 || 122 sshbuf_put_u32(encoded, sig_counter) != 0 || 123 sshbuf_put(encoded, msghash, sizeof(msghash)) != 0) { 124 r = SSH_ERR_ALLOC_FAIL; 125 goto out; 126 } 127 #ifdef DEBUG_SK 128 fprintf(stderr, "%s: signed buf:\n", __func__); 129 sshbuf_dump(encoded, stderr); 130 #endif 131 sm = sshbuf_ptr(encoded); 132 smlen = sshbuf_len(encoded); 133 mlen = smlen; 134 if ((m = malloc(smlen)) == NULL) { 135 r = SSH_ERR_ALLOC_FAIL; 136 goto out; 137 } 138 if ((ret = crypto_sign_ed25519_open(m, &mlen, sm, smlen, 139 key->ed25519_pk)) != 0) { 140 debug2_f("crypto_sign_ed25519_open failed: %d", ret); 141 } 142 if (ret != 0 || mlen != smlen - len) { 143 r = SSH_ERR_SIGNATURE_INVALID; 144 goto out; 145 } 146 /* XXX compare 'm' and 'sm + len' ? */ 147 /* success */ 148 r = 0; 149 if (detailsp != NULL) { 150 *detailsp = details; 151 details = NULL; 152 } 153 out: 154 if (m != NULL) 155 freezero(m, smlen); /* NB mlen may be invalid if r != 0 */ 156 sshkey_sig_details_free(details); 157 sshbuf_free(b); 158 sshbuf_free(encoded); 159 free(ktype); 160 return r; 161 } 162