1 /* Copyright (c) 2014, Google Inc.
2 *
3 * Permission to use, copy, modify, and/or distribute this software for any
4 * purpose with or without fee is hereby granted, provided that the above
5 * copyright notice and this permission notice appear in all copies.
6 *
7 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
8 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
10 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
14
15 #include <openssl/aead.h>
16
17 #include <string.h>
18
19 #include <openssl/chacha.h>
20 #include <openssl/cipher.h>
21 #include <openssl/err.h>
22 #include <openssl/mem.h>
23 #include <openssl/poly1305.h>
24
25 #include "internal.h"
26
27
28 #define POLY1305_TAG_LEN 16
29 #define CHACHA20_NONCE_LEN 8
30
31 struct aead_chacha20_poly1305_ctx {
32 unsigned char key[32];
33 unsigned char tag_len;
34 };
35
aead_chacha20_poly1305_init(EVP_AEAD_CTX * ctx,const uint8_t * key,size_t key_len,size_t tag_len)36 static int aead_chacha20_poly1305_init(EVP_AEAD_CTX *ctx, const uint8_t *key,
37 size_t key_len, size_t tag_len) {
38 struct aead_chacha20_poly1305_ctx *c20_ctx;
39
40 if (tag_len == 0) {
41 tag_len = POLY1305_TAG_LEN;
42 }
43
44 if (tag_len > POLY1305_TAG_LEN) {
45 OPENSSL_PUT_ERROR(CIPHER, aead_chacha20_poly1305_init, CIPHER_R_TOO_LARGE);
46 return 0;
47 }
48
49 if (key_len != sizeof(c20_ctx->key)) {
50 return 0; /* internal error - EVP_AEAD_CTX_init should catch this. */
51 }
52
53 c20_ctx = OPENSSL_malloc(sizeof(struct aead_chacha20_poly1305_ctx));
54 if (c20_ctx == NULL) {
55 return 0;
56 }
57
58 memcpy(c20_ctx->key, key, key_len);
59 c20_ctx->tag_len = tag_len;
60 ctx->aead_state = c20_ctx;
61
62 return 1;
63 }
64
aead_chacha20_poly1305_cleanup(EVP_AEAD_CTX * ctx)65 static void aead_chacha20_poly1305_cleanup(EVP_AEAD_CTX *ctx) {
66 struct aead_chacha20_poly1305_ctx *c20_ctx = ctx->aead_state;
67 OPENSSL_cleanse(c20_ctx->key, sizeof(c20_ctx->key));
68 OPENSSL_free(c20_ctx);
69 }
70
poly1305_update_with_length(poly1305_state * poly1305,const uint8_t * data,size_t data_len)71 static void poly1305_update_with_length(poly1305_state *poly1305,
72 const uint8_t *data, size_t data_len) {
73 size_t j = data_len;
74 uint8_t length_bytes[8];
75 unsigned i;
76
77 for (i = 0; i < sizeof(length_bytes); i++) {
78 length_bytes[i] = j;
79 j >>= 8;
80 }
81
82 CRYPTO_poly1305_update(poly1305, data, data_len);
83 CRYPTO_poly1305_update(poly1305, length_bytes, sizeof(length_bytes));
84 }
85
86 #if defined(__arm__)
87 #define ALIGNED __attribute__((aligned(16)))
88 #else
89 #define ALIGNED
90 #endif
91
aead_chacha20_poly1305_seal(const EVP_AEAD_CTX * ctx,uint8_t * out,size_t * out_len,size_t max_out_len,const uint8_t * nonce,size_t nonce_len,const uint8_t * in,size_t in_len,const uint8_t * ad,size_t ad_len)92 static int aead_chacha20_poly1305_seal(const EVP_AEAD_CTX *ctx, uint8_t *out,
93 size_t *out_len, size_t max_out_len,
94 const uint8_t *nonce, size_t nonce_len,
95 const uint8_t *in, size_t in_len,
96 const uint8_t *ad, size_t ad_len) {
97 const struct aead_chacha20_poly1305_ctx *c20_ctx = ctx->aead_state;
98 uint8_t poly1305_key[32] ALIGNED;
99 poly1305_state poly1305;
100 const uint64_t in_len_64 = in_len;
101
102 /* The underlying ChaCha implementation may not overflow the block
103 * counter into the second counter word. Therefore we disallow
104 * individual operations that work on more than 256GB at a time.
105 * |in_len_64| is needed because, on 32-bit platforms, size_t is only
106 * 32-bits and this produces a warning because it's always false.
107 * Casting to uint64_t inside the conditional is not sufficient to stop
108 * the warning. */
109 if (in_len_64 >= (1ull << 32) * 64 - 64) {
110 OPENSSL_PUT_ERROR(CIPHER, aead_chacha20_poly1305_seal, CIPHER_R_TOO_LARGE);
111 return 0;
112 }
113
114 if (in_len + c20_ctx->tag_len < in_len) {
115 OPENSSL_PUT_ERROR(CIPHER, aead_chacha20_poly1305_seal, CIPHER_R_TOO_LARGE);
116 return 0;
117 }
118
119 if (max_out_len < in_len + c20_ctx->tag_len) {
120 OPENSSL_PUT_ERROR(CIPHER, aead_chacha20_poly1305_seal,
121 CIPHER_R_BUFFER_TOO_SMALL);
122 return 0;
123 }
124
125 if (nonce_len != CHACHA20_NONCE_LEN) {
126 OPENSSL_PUT_ERROR(CIPHER, aead_chacha20_poly1305_seal, CIPHER_R_IV_TOO_LARGE);
127 return 0;
128 }
129
130 memset(poly1305_key, 0, sizeof(poly1305_key));
131 CRYPTO_chacha_20(poly1305_key, poly1305_key, sizeof(poly1305_key),
132 c20_ctx->key, nonce, 0);
133
134 CRYPTO_poly1305_init(&poly1305, poly1305_key);
135 poly1305_update_with_length(&poly1305, ad, ad_len);
136 CRYPTO_chacha_20(out, in, in_len, c20_ctx->key, nonce, 1);
137 poly1305_update_with_length(&poly1305, out, in_len);
138
139 uint8_t tag[POLY1305_TAG_LEN] ALIGNED;
140 CRYPTO_poly1305_finish(&poly1305, tag);
141 memcpy(out + in_len, tag, c20_ctx->tag_len);
142 *out_len = in_len + c20_ctx->tag_len;
143 return 1;
144 }
145
aead_chacha20_poly1305_open(const EVP_AEAD_CTX * ctx,uint8_t * out,size_t * out_len,size_t max_out_len,const uint8_t * nonce,size_t nonce_len,const uint8_t * in,size_t in_len,const uint8_t * ad,size_t ad_len)146 static int aead_chacha20_poly1305_open(const EVP_AEAD_CTX *ctx, uint8_t *out,
147 size_t *out_len, size_t max_out_len,
148 const uint8_t *nonce, size_t nonce_len,
149 const uint8_t *in, size_t in_len,
150 const uint8_t *ad, size_t ad_len) {
151 const struct aead_chacha20_poly1305_ctx *c20_ctx = ctx->aead_state;
152 uint8_t mac[POLY1305_TAG_LEN];
153 uint8_t poly1305_key[32] ALIGNED;
154 size_t plaintext_len;
155 poly1305_state poly1305;
156 const uint64_t in_len_64 = in_len;
157
158 if (in_len < c20_ctx->tag_len) {
159 OPENSSL_PUT_ERROR(CIPHER, aead_chacha20_poly1305_open, CIPHER_R_BAD_DECRYPT);
160 return 0;
161 }
162
163 /* The underlying ChaCha implementation may not overflow the block
164 * counter into the second counter word. Therefore we disallow
165 * individual operations that work on more than 256GB at a time.
166 * |in_len_64| is needed because, on 32-bit platforms, size_t is only
167 * 32-bits and this produces a warning because it's always false.
168 * Casting to uint64_t inside the conditional is not sufficient to stop
169 * the warning. */
170 if (in_len_64 >= (1ull << 32) * 64 - 64) {
171 OPENSSL_PUT_ERROR(CIPHER, aead_chacha20_poly1305_open, CIPHER_R_TOO_LARGE);
172 return 0;
173 }
174
175 if (nonce_len != CHACHA20_NONCE_LEN) {
176 OPENSSL_PUT_ERROR(CIPHER, aead_chacha20_poly1305_open, CIPHER_R_IV_TOO_LARGE);
177 return 0;
178 }
179
180 plaintext_len = in_len - c20_ctx->tag_len;
181
182 if (max_out_len < plaintext_len) {
183 OPENSSL_PUT_ERROR(CIPHER, aead_chacha20_poly1305_open,
184 CIPHER_R_BUFFER_TOO_SMALL);
185 return 0;
186 }
187
188 memset(poly1305_key, 0, sizeof(poly1305_key));
189 CRYPTO_chacha_20(poly1305_key, poly1305_key, sizeof(poly1305_key),
190 c20_ctx->key, nonce, 0);
191
192 CRYPTO_poly1305_init(&poly1305, poly1305_key);
193 poly1305_update_with_length(&poly1305, ad, ad_len);
194 poly1305_update_with_length(&poly1305, in, plaintext_len);
195 CRYPTO_poly1305_finish(&poly1305, mac);
196
197 if (CRYPTO_memcmp(mac, in + plaintext_len, c20_ctx->tag_len) != 0) {
198 OPENSSL_PUT_ERROR(CIPHER, aead_chacha20_poly1305_open, CIPHER_R_BAD_DECRYPT);
199 return 0;
200 }
201
202 CRYPTO_chacha_20(out, in, plaintext_len, c20_ctx->key, nonce, 1);
203 *out_len = plaintext_len;
204 return 1;
205 }
206
207 static const EVP_AEAD aead_chacha20_poly1305 = {
208 32, /* key len */
209 CHACHA20_NONCE_LEN, /* nonce len */
210 POLY1305_TAG_LEN, /* overhead */
211 POLY1305_TAG_LEN, /* max tag length */
212 aead_chacha20_poly1305_init,
213 NULL, /* init_with_direction */
214 aead_chacha20_poly1305_cleanup,
215 aead_chacha20_poly1305_seal,
216 aead_chacha20_poly1305_open,
217 NULL, /* get_rc4_state */
218 };
219
EVP_aead_chacha20_poly1305(void)220 const EVP_AEAD *EVP_aead_chacha20_poly1305(void) {
221 return &aead_chacha20_poly1305;
222 }
223