Line | Count | Source (jump to first uncovered line) |
1 | | /* |
2 | | * Copyright (c) 2018-2021 Yubico AB. All rights reserved. |
3 | | * Use of this source code is governed by a BSD-style |
4 | | * license that can be found in the LICENSE file. |
5 | | */ |
6 | | |
7 | | #include <openssl/evp.h> |
8 | | #include <openssl/sha.h> |
9 | | #if defined(LIBRESSL_VERSION_NUMBER) |
10 | | #include <openssl/hkdf.h> |
11 | | #else |
12 | | #include <openssl/kdf.h> |
13 | | #endif |
14 | | |
15 | | #include "fido.h" |
16 | | #include "fido/es256.h" |
17 | | |
18 | | #if defined(LIBRESSL_VERSION_NUMBER) |
19 | | static int |
20 | | hkdf_sha256(uint8_t *key, const char *info, const fido_blob_t *secret) |
21 | | { |
22 | | const EVP_MD *md; |
23 | | uint8_t salt[32]; |
24 | | |
25 | | memset(salt, 0, sizeof(salt)); |
26 | | if ((md = EVP_sha256()) == NULL || |
27 | | HKDF(key, SHA256_DIGEST_LENGTH, md, secret->ptr, secret->len, salt, |
28 | | sizeof(salt), (const uint8_t *)info, strlen(info)) != 1) |
29 | | return -1; |
30 | | |
31 | | return 0; |
32 | | } |
33 | | #else |
34 | | static int |
35 | | hkdf_sha256(uint8_t *key, char *info, fido_blob_t *secret) |
36 | 836 | { |
37 | 836 | const EVP_MD *const_md; |
38 | 836 | EVP_MD *md = NULL; |
39 | 836 | EVP_PKEY_CTX *ctx = NULL; |
40 | 836 | size_t keylen = SHA256_DIGEST_LENGTH; |
41 | 836 | uint8_t salt[32]; |
42 | 836 | int ok = -1; |
43 | | |
44 | 836 | memset(salt, 0, sizeof(salt)); |
45 | 836 | if (secret->len > INT_MAX || strlen(info) > INT_MAX) { |
46 | 0 | fido_log_debug("%s: invalid param", __func__); |
47 | 0 | goto fail; |
48 | 0 | } |
49 | 836 | if ((const_md = EVP_sha256()) == NULL || |
50 | 836 | (md = EVP_MD_meth_dup(const_md)) == NULL || |
51 | 836 | (ctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL)) == NULL) { |
52 | 22 | fido_log_debug("%s: init", __func__); |
53 | 22 | goto fail; |
54 | 22 | } |
55 | 814 | if (EVP_PKEY_derive_init(ctx) < 1 || |
56 | 814 | EVP_PKEY_CTX_set_hkdf_md(ctx, md) < 1 || |
57 | 814 | EVP_PKEY_CTX_set1_hkdf_salt(ctx, salt, sizeof(salt)) < 1 || |
58 | 814 | EVP_PKEY_CTX_set1_hkdf_key(ctx, secret->ptr, (int)secret->len) < 1 || |
59 | 814 | EVP_PKEY_CTX_add1_hkdf_info(ctx, (void *)info, (int)strlen(info)) < 1) { |
60 | 62 | fido_log_debug("%s: EVP_PKEY_CTX", __func__); |
61 | 62 | goto fail; |
62 | 62 | } |
63 | 752 | if (EVP_PKEY_derive(ctx, key, &keylen) < 1) { |
64 | 12 | fido_log_debug("%s: EVP_PKEY_derive", __func__); |
65 | 12 | goto fail; |
66 | 12 | } |
67 | | |
68 | 740 | ok = 0; |
69 | 836 | fail: |
70 | 836 | if (md != NULL) |
71 | 825 | EVP_MD_meth_free(md); |
72 | 836 | if (ctx != NULL) |
73 | 814 | EVP_PKEY_CTX_free(ctx); |
74 | | |
75 | 836 | return ok; |
76 | 740 | } |
77 | | #endif /* defined(LIBRESSL_VERSION_NUMBER) */ |
78 | | |
79 | | static int |
80 | | kdf(uint8_t prot, fido_blob_t *key, /* const */ fido_blob_t *secret) |
81 | 3.42k | { |
82 | 3.42k | char hmac_info[] = "CTAP2 HMAC key"; /* const */ |
83 | 3.42k | char aes_info[] = "CTAP2 AES key"; /* const */ |
84 | | |
85 | 3.42k | switch (prot) { |
86 | 2.97k | case CTAP_PIN_PROTOCOL1: |
87 | | /* use sha256 on the resulting secret */ |
88 | 2.97k | key->len = SHA256_DIGEST_LENGTH; |
89 | 2.97k | if ((key->ptr = calloc(1, key->len)) == NULL || |
90 | 2.97k | SHA256(secret->ptr, secret->len, key->ptr) != key->ptr) { |
91 | 22 | fido_log_debug("%s: SHA256", __func__); |
92 | 22 | return -1; |
93 | 22 | } |
94 | 2.95k | break; |
95 | 2.95k | case CTAP_PIN_PROTOCOL2: |
96 | | /* use two instances of hkdf-sha256 on the resulting secret */ |
97 | 447 | key->len = 2 * SHA256_DIGEST_LENGTH; |
98 | 447 | if ((key->ptr = calloc(1, key->len)) == NULL || |
99 | 447 | hkdf_sha256(key->ptr, hmac_info, secret) < 0 || |
100 | 447 | hkdf_sha256(key->ptr + SHA256_DIGEST_LENGTH, aes_info, |
101 | 396 | secret) < 0) { |
102 | 103 | fido_log_debug("%s: hkdf", __func__); |
103 | 103 | return -1; |
104 | 103 | } |
105 | 344 | break; |
106 | 344 | default: |
107 | 0 | fido_log_debug("%s: unknown pin protocol %u", __func__, prot); |
108 | 0 | return -1; |
109 | 3.42k | } |
110 | | |
111 | 3.29k | return 0; |
112 | 3.42k | } |
113 | | |
114 | | static int |
115 | | do_ecdh(const fido_dev_t *dev, const es256_sk_t *sk, const es256_pk_t *pk, |
116 | | fido_blob_t **ecdh) |
117 | 3.80k | { |
118 | 3.80k | EVP_PKEY *pk_evp = NULL; |
119 | 3.80k | EVP_PKEY *sk_evp = NULL; |
120 | 3.80k | EVP_PKEY_CTX *ctx = NULL; |
121 | 3.80k | fido_blob_t *secret = NULL; |
122 | 3.80k | int ok = -1; |
123 | | |
124 | 3.80k | *ecdh = NULL; |
125 | 3.80k | if ((secret = fido_blob_new()) == NULL || |
126 | 3.80k | (*ecdh = fido_blob_new()) == NULL) |
127 | 19 | goto fail; |
128 | 3.78k | if ((pk_evp = es256_pk_to_EVP_PKEY(pk)) == NULL || |
129 | 3.78k | (sk_evp = es256_sk_to_EVP_PKEY(sk)) == NULL) { |
130 | 303 | fido_log_debug("%s: es256_to_EVP_PKEY", __func__); |
131 | 303 | goto fail; |
132 | 303 | } |
133 | 3.48k | if ((ctx = EVP_PKEY_CTX_new(sk_evp, NULL)) == NULL || |
134 | 3.48k | EVP_PKEY_derive_init(ctx) <= 0 || |
135 | 3.48k | EVP_PKEY_derive_set_peer(ctx, pk_evp) <= 0) { |
136 | 33 | fido_log_debug("%s: EVP_PKEY_derive_init", __func__); |
137 | 33 | goto fail; |
138 | 33 | } |
139 | 3.45k | if (EVP_PKEY_derive(ctx, NULL, &secret->len) <= 0 || |
140 | 3.45k | (secret->ptr = calloc(1, secret->len)) == NULL || |
141 | 3.45k | EVP_PKEY_derive(ctx, secret->ptr, &secret->len) <= 0) { |
142 | 30 | fido_log_debug("%s: EVP_PKEY_derive", __func__); |
143 | 30 | goto fail; |
144 | 30 | } |
145 | 3.42k | if (kdf(fido_dev_get_pin_protocol(dev), *ecdh, secret) < 0) { |
146 | 125 | fido_log_debug("%s: kdf", __func__); |
147 | 125 | goto fail; |
148 | 125 | } |
149 | | |
150 | 3.29k | ok = 0; |
151 | 3.80k | fail: |
152 | 3.80k | if (pk_evp != NULL) |
153 | 3.55k | EVP_PKEY_free(pk_evp); |
154 | 3.80k | if (sk_evp != NULL) |
155 | 3.48k | EVP_PKEY_free(sk_evp); |
156 | 3.80k | if (ctx != NULL) |
157 | 3.47k | EVP_PKEY_CTX_free(ctx); |
158 | 3.80k | if (ok < 0) |
159 | 510 | fido_blob_free(ecdh); |
160 | | |
161 | 3.80k | fido_blob_free(&secret); |
162 | | |
163 | 3.80k | return ok; |
164 | 3.29k | } |
165 | | |
166 | | int |
167 | | fido_do_ecdh(fido_dev_t *dev, es256_pk_t **pk, fido_blob_t **ecdh, int *ms) |
168 | 7.52k | { |
169 | 7.52k | es256_sk_t *sk = NULL; /* our private key */ |
170 | 7.52k | es256_pk_t *ak = NULL; /* authenticator's public key */ |
171 | 7.52k | int r; |
172 | | |
173 | 7.52k | *pk = NULL; |
174 | 7.52k | *ecdh = NULL; |
175 | 7.52k | if ((sk = es256_sk_new()) == NULL || (*pk = es256_pk_new()) == NULL) { |
176 | 65 | r = FIDO_ERR_INTERNAL; |
177 | 65 | goto fail; |
178 | 65 | } |
179 | 7.46k | if (es256_sk_create(sk) < 0 || es256_derive_pk(sk, *pk) < 0) { |
180 | 683 | fido_log_debug("%s: es256_derive_pk", __func__); |
181 | 683 | r = FIDO_ERR_INTERNAL; |
182 | 683 | goto fail; |
183 | 683 | } |
184 | 6.77k | if ((ak = es256_pk_new()) == NULL || |
185 | 6.77k | fido_dev_authkey(dev, ak, ms) != FIDO_OK) { |
186 | 2.96k | fido_log_debug("%s: fido_dev_authkey", __func__); |
187 | 2.96k | r = FIDO_ERR_INTERNAL; |
188 | 2.96k | goto fail; |
189 | 2.96k | } |
190 | 3.80k | if (do_ecdh(dev, sk, ak, ecdh) < 0) { |
191 | 510 | fido_log_debug("%s: do_ecdh", __func__); |
192 | 510 | r = FIDO_ERR_INTERNAL; |
193 | 510 | goto fail; |
194 | 510 | } |
195 | | |
196 | 3.29k | r = FIDO_OK; |
197 | 7.52k | fail: |
198 | 7.52k | es256_sk_free(&sk); |
199 | 7.52k | es256_pk_free(&ak); |
200 | | |
201 | 7.52k | if (r != FIDO_OK) { |
202 | 4.22k | es256_pk_free(pk); |
203 | 4.22k | fido_blob_free(ecdh); |
204 | 4.22k | } |
205 | | |
206 | 7.52k | return r; |
207 | 3.29k | } |