xref: /openssl/crypto/cmac/cmac.c (revision 4f5febe2) 
1 /*
2  * Copyright 2010-2024 The OpenSSL Project Authors. All Rights Reserved.
3  *
4  * Licensed under the Apache License 2.0 (the "License").  You may not use
5  * this file except in compliance with the License.  You can obtain a copy
6  * in the file LICENSE in the source distribution or at
7  * https://www.openssl.org/source/license.html
8  */
9 
10 /*
11  * CMAC low level APIs are deprecated for public use, but still ok for internal
12  * use.
13  */
14 #include "internal/deprecated.h"
15 
16 #include <stdio.h>
17 #include <stdlib.h>
18 #include <string.h>
19 #include "internal/cryptlib.h"
20 #include <openssl/cmac.h>
21 #include <openssl/err.h>
22 #include "crypto/cmac.h"
23 
24 #define LOCAL_BUF_SIZE 2048
25 struct CMAC_CTX_st {
26     /* Cipher context to use */
27     EVP_CIPHER_CTX *cctx;
28     /* Keys k1 and k2 */
29     unsigned char k1[EVP_MAX_BLOCK_LENGTH];
30     unsigned char k2[EVP_MAX_BLOCK_LENGTH];
31     /* Temporary block */
32     unsigned char tbl[EVP_MAX_BLOCK_LENGTH];
33     /* Last (possibly partial) block */
34     unsigned char last_block[EVP_MAX_BLOCK_LENGTH];
35     /* Number of bytes in last block: -1 means context not initialised */
36     int nlast_block;
37 };
38 
39 /* Make temporary keys K1 and K2 */
40 
make_kn(unsigned char * k1,const unsigned char * l,int bl)41 static void make_kn(unsigned char *k1, const unsigned char *l, int bl)
42 {
43     int i;
44     unsigned char c = l[0], carry = c >> 7, cnext;
45 
46     /* Shift block to left, including carry */
47     for (i = 0; i < bl - 1; i++, c = cnext)
48         k1[i] = (c << 1) | ((cnext = l[i + 1]) >> 7);
49 
50     /* If MSB set fixup with R */
51     k1[i] = (c << 1) ^ ((0 - carry) & (bl == 16 ? 0x87 : 0x1b));
52 }
53 
CMAC_CTX_new(void)54 CMAC_CTX *CMAC_CTX_new(void)
55 {
56     CMAC_CTX *ctx;
57 
58     if ((ctx = OPENSSL_malloc(sizeof(*ctx))) == NULL)
59         return NULL;
60     ctx->cctx = EVP_CIPHER_CTX_new();
61     if (ctx->cctx == NULL) {
62         OPENSSL_free(ctx);
63         return NULL;
64     }
65     ctx->nlast_block = -1;
66     return ctx;
67 }
68 
CMAC_CTX_cleanup(CMAC_CTX * ctx)69 void CMAC_CTX_cleanup(CMAC_CTX *ctx)
70 {
71     EVP_CIPHER_CTX_reset(ctx->cctx);
72     OPENSSL_cleanse(ctx->tbl, EVP_MAX_BLOCK_LENGTH);
73     OPENSSL_cleanse(ctx->k1, EVP_MAX_BLOCK_LENGTH);
74     OPENSSL_cleanse(ctx->k2, EVP_MAX_BLOCK_LENGTH);
75     OPENSSL_cleanse(ctx->last_block, EVP_MAX_BLOCK_LENGTH);
76     ctx->nlast_block = -1;
77 }
78 
CMAC_CTX_get0_cipher_ctx(CMAC_CTX * ctx)79 EVP_CIPHER_CTX *CMAC_CTX_get0_cipher_ctx(CMAC_CTX *ctx)
80 {
81     return ctx->cctx;
82 }
83 
CMAC_CTX_free(CMAC_CTX * ctx)84 void CMAC_CTX_free(CMAC_CTX *ctx)
85 {
86     if (!ctx)
87         return;
88     CMAC_CTX_cleanup(ctx);
89     EVP_CIPHER_CTX_free(ctx->cctx);
90     OPENSSL_free(ctx);
91 }
92 
CMAC_CTX_copy(CMAC_CTX * out,const CMAC_CTX * in)93 int CMAC_CTX_copy(CMAC_CTX *out, const CMAC_CTX *in)
94 {
95     int bl;
96 
97     if (in->nlast_block == -1)
98         return 0;
99     if ((bl = EVP_CIPHER_CTX_get_block_size(in->cctx)) == 0)
100         return 0;
101     if (!EVP_CIPHER_CTX_copy(out->cctx, in->cctx))
102         return 0;
103     memcpy(out->k1, in->k1, bl);
104     memcpy(out->k2, in->k2, bl);
105     memcpy(out->tbl, in->tbl, bl);
106     memcpy(out->last_block, in->last_block, bl);
107     out->nlast_block = in->nlast_block;
108     return 1;
109 }
110 
ossl_cmac_init(CMAC_CTX * ctx,const void * key,size_t keylen,const EVP_CIPHER * cipher,ENGINE * impl,const OSSL_PARAM param[])111 int ossl_cmac_init(CMAC_CTX *ctx, const void *key, size_t keylen,
112                    const EVP_CIPHER *cipher, ENGINE *impl,
113                    const OSSL_PARAM param[])
114 {
115     static const unsigned char zero_iv[EVP_MAX_BLOCK_LENGTH] = { 0 };
116     int block_len;
117 
118     /* All zeros means restart */
119     if (!key && !cipher && !impl && keylen == 0) {
120         /* Not initialised */
121         if (ctx->nlast_block == -1)
122             return 0;
123         if (!EVP_EncryptInit_ex2(ctx->cctx, NULL, NULL, zero_iv, param))
124             return 0;
125         block_len = EVP_CIPHER_CTX_get_block_size(ctx->cctx);
126         if (block_len == 0)
127             return 0;
128         memset(ctx->tbl, 0, block_len);
129         ctx->nlast_block = 0;
130         return 1;
131     }
132     /* Initialise context */
133     if (cipher != NULL) {
134         /* Ensure we can't use this ctx until we also have a key */
135         ctx->nlast_block = -1;
136         if (impl != NULL) {
137             if (!EVP_EncryptInit_ex(ctx->cctx, cipher, impl, NULL, NULL))
138                 return 0;
139         } else {
140             if (!EVP_EncryptInit_ex2(ctx->cctx, cipher, NULL, NULL, param))
141                 return 0;
142         }
143     }
144     /* Non-NULL key means initialisation complete */
145     if (key != NULL) {
146         int bl;
147 
148         /* If anything fails then ensure we can't use this ctx */
149         ctx->nlast_block = -1;
150         if (EVP_CIPHER_CTX_get0_cipher(ctx->cctx) == NULL)
151             return 0;
152         if (EVP_CIPHER_CTX_set_key_length(ctx->cctx, keylen) <= 0)
153             return 0;
154         if (!EVP_EncryptInit_ex2(ctx->cctx, NULL, key, zero_iv, param))
155             return 0;
156         if ((bl = EVP_CIPHER_CTX_get_block_size(ctx->cctx)) < 0)
157             return 0;
158         if (EVP_Cipher(ctx->cctx, ctx->tbl, zero_iv, bl) <= 0)
159             return 0;
160         make_kn(ctx->k1, ctx->tbl, bl);
161         make_kn(ctx->k2, ctx->k1, bl);
162         OPENSSL_cleanse(ctx->tbl, bl);
163         /* Reset context again ready for first data block */
164         if (!EVP_EncryptInit_ex2(ctx->cctx, NULL, NULL, zero_iv, param))
165             return 0;
166         /* Zero tbl so resume works */
167         memset(ctx->tbl, 0, bl);
168         ctx->nlast_block = 0;
169     }
170     return 1;
171 }
172 
CMAC_Init(CMAC_CTX * ctx,const void * key,size_t keylen,const EVP_CIPHER * cipher,ENGINE * impl)173 int CMAC_Init(CMAC_CTX *ctx, const void *key, size_t keylen,
174               const EVP_CIPHER *cipher, ENGINE *impl)
175 {
176     return ossl_cmac_init(ctx, key, keylen, cipher, impl, NULL);
177 }
178 
CMAC_Update(CMAC_CTX * ctx,const void * in,size_t dlen)179 int CMAC_Update(CMAC_CTX *ctx, const void *in, size_t dlen)
180 {
181     const unsigned char *data = in;
182     int bl;
183     size_t max_burst_blocks, cipher_blocks;
184     unsigned char buf[LOCAL_BUF_SIZE];
185 
186     if (ctx->nlast_block == -1)
187         return 0;
188     if (dlen == 0)
189         return 1;
190     if ((bl = EVP_CIPHER_CTX_get_block_size(ctx->cctx)) == 0)
191         return 0;
192     /* Copy into partial block if we need to */
193     if (ctx->nlast_block > 0) {
194         size_t nleft;
195 
196         nleft = bl - ctx->nlast_block;
197         if (dlen < nleft)
198             nleft = dlen;
199         memcpy(ctx->last_block + ctx->nlast_block, data, nleft);
200         dlen -= nleft;
201         ctx->nlast_block += nleft;
202         /* If no more to process return */
203         if (dlen == 0)
204             return 1;
205         data += nleft;
206         /* Else not final block so encrypt it */
207         if (EVP_Cipher(ctx->cctx, ctx->tbl, ctx->last_block, bl) <= 0)
208             return 0;
209     }
210     /* Encrypt all but one of the complete blocks left */
211 
212     max_burst_blocks = LOCAL_BUF_SIZE / bl;
213     cipher_blocks = (dlen - 1) / bl;
214     if (max_burst_blocks == 0) {
215         /*
216          * When block length is greater than local buffer size,
217          * use ctx->tbl as cipher output.
218          */
219         while (dlen > (size_t)bl) {
220             if (EVP_Cipher(ctx->cctx, ctx->tbl, data, bl) <= 0)
221                 return 0;
222             dlen -= bl;
223             data += bl;
224         }
225     } else {
226         while (cipher_blocks > max_burst_blocks) {
227             if (EVP_Cipher(ctx->cctx, buf, data, max_burst_blocks * bl) <= 0)
228                 return 0;
229             dlen -= max_burst_blocks * bl;
230             data += max_burst_blocks * bl;
231             cipher_blocks -= max_burst_blocks;
232         }
233         if (cipher_blocks > 0) {
234             if (EVP_Cipher(ctx->cctx, buf, data, cipher_blocks * bl) <= 0)
235                 return 0;
236             dlen -= cipher_blocks * bl;
237             data += cipher_blocks * bl;
238             memcpy(ctx->tbl, &buf[(cipher_blocks - 1) * bl], bl);
239         }
240     }
241     /* Copy any data left to last block buffer */
242     memcpy(ctx->last_block, data, dlen);
243     ctx->nlast_block = dlen;
244     return 1;
245 
246 }
247 
CMAC_Final(CMAC_CTX * ctx,unsigned char * out,size_t * poutlen)248 int CMAC_Final(CMAC_CTX *ctx, unsigned char *out, size_t *poutlen)
249 {
250     int i, bl, lb;
251 
252     if (ctx->nlast_block == -1)
253         return 0;
254     if ((bl = EVP_CIPHER_CTX_get_block_size(ctx->cctx)) == 0)
255         return 0;
256     if (poutlen != NULL)
257         *poutlen = (size_t)bl;
258     if (!out)
259         return 1;
260     lb = ctx->nlast_block;
261     /* Is last block complete? */
262     if (lb == bl) {
263         for (i = 0; i < bl; i++)
264             out[i] = ctx->last_block[i] ^ ctx->k1[i];
265     } else {
266         ctx->last_block[lb] = 0x80;
267         if (bl - lb > 1)
268             memset(ctx->last_block + lb + 1, 0, bl - lb - 1);
269         for (i = 0; i < bl; i++)
270             out[i] = ctx->last_block[i] ^ ctx->k2[i];
271     }
272     if (EVP_Cipher(ctx->cctx, out, out, bl) <= 0) {
273         OPENSSL_cleanse(out, bl);
274         return 0;
275     }
276     return 1;
277 }
278 
CMAC_resume(CMAC_CTX * ctx)279 int CMAC_resume(CMAC_CTX *ctx)
280 {
281     if (ctx->nlast_block == -1)
282         return 0;
283     /*
284      * The buffer "tbl" contains the last fully encrypted block which is the
285      * last IV (or all zeroes if no last encrypted block). The last block has
286      * not been modified since CMAC_final(). So reinitialising using the last
287      * decrypted block will allow CMAC to continue after calling
288      * CMAC_Final().
289      */
290     return EVP_EncryptInit_ex(ctx->cctx, NULL, NULL, NULL, ctx->tbl);
291 }
292