/src/openssl/crypto/cmac/cmac.c

Source
/*
 * Copyright 2010-2025 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the Apache License 2.0 (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

/*
 * CMAC low level APIs are deprecated for public use, but still ok for internal
 * use.
 */
#include "internal/deprecated.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "internal/cryptlib.h"
#include <openssl/cmac.h>
#include <openssl/err.h>
#include "crypto/cmac.h"
#include "internal/common.h"

#define LOCAL_BUF_SIZE 2048
struct CMAC_CTX_st {
    /* Cipher context to use */
    EVP_CIPHER_CTX *cctx;
    /* Keys k1 and k2 */
    unsigned char k1[EVP_MAX_BLOCK_LENGTH];
    unsigned char k2[EVP_MAX_BLOCK_LENGTH];
    /* Temporary block */
    unsigned char tbl[EVP_MAX_BLOCK_LENGTH];
    /* Last (possibly partial) block */
    unsigned char last_block[EVP_MAX_BLOCK_LENGTH];
    /* Number of bytes in last block: -1 means context not initialised */
    int nlast_block;
};

/* Make temporary keys K1 and K2 */

static void make_kn(unsigned char *k1, const unsigned char *l, int bl)
{
    int i;
    unsigned char c = l[0], carry = c >> 7, cnext;

    /* Shift block to left, including carry */
    for (i = 0; i < bl - 1; i++, c = cnext)
        k1[i] = (c << 1) | ((cnext = l[i + 1]) >> 7);

    /* If MSB set fixup with R */
    k1[i] = (c << 1) ^ ((0 - carry) & (bl == 16 ? 0x87 : 0x1b));
}

CMAC_CTX *CMAC_CTX_new(void)
{
    CMAC_CTX *ctx;

    if ((ctx = OPENSSL_malloc(sizeof(*ctx))) == NULL)
        return NULL;
    ctx->cctx = EVP_CIPHER_CTX_new();
    if (ctx->cctx == NULL) {
        OPENSSL_free(ctx);
        return NULL;
    }
    ctx->nlast_block = -1;
    return ctx;
}

void CMAC_CTX_cleanup(CMAC_CTX *ctx)
{
    EVP_CIPHER_CTX_reset(ctx->cctx);
    OPENSSL_cleanse(ctx->tbl, EVP_MAX_BLOCK_LENGTH);
    OPENSSL_cleanse(ctx->k1, EVP_MAX_BLOCK_LENGTH);
    OPENSSL_cleanse(ctx->k2, EVP_MAX_BLOCK_LENGTH);
    OPENSSL_cleanse(ctx->last_block, EVP_MAX_BLOCK_LENGTH);
    ctx->nlast_block = -1;
}

EVP_CIPHER_CTX *CMAC_CTX_get0_cipher_ctx(CMAC_CTX *ctx)
{
    return ctx->cctx;
}

void CMAC_CTX_free(CMAC_CTX *ctx)
{
    if (!ctx)
        return;
    CMAC_CTX_cleanup(ctx);
    EVP_CIPHER_CTX_free(ctx->cctx);
    OPENSSL_free(ctx);
}

int CMAC_CTX_copy(CMAC_CTX *out, const CMAC_CTX *in)
{
    int bl;

    if (in->nlast_block == -1)
        return 0;
    if ((bl = EVP_CIPHER_CTX_get_block_size(in->cctx)) == 0)
        return 0;
    if (!EVP_CIPHER_CTX_copy(out->cctx, in->cctx))
        return 0;
    memcpy(out->k1, in->k1, bl);
    memcpy(out->k2, in->k2, bl);
    memcpy(out->tbl, in->tbl, bl);
    memcpy(out->last_block, in->last_block, bl);
    out->nlast_block = in->nlast_block;
    return 1;
}

int ossl_cmac_init(CMAC_CTX *ctx, const void *key, size_t keylen,
                   const EVP_CIPHER *cipher, const OSSL_PARAM param[])
{
    static const unsigned char zero_iv[EVP_MAX_BLOCK_LENGTH] = { 0 };
    int block_len;

    /* All zeros means restart */
    if (key == NULL && cipher == NULL && keylen == 0) {
        /* Not initialised */
        if (ctx->nlast_block == -1)
            return 0;
        if (!EVP_EncryptInit_ex2(ctx->cctx, NULL, NULL, zero_iv, param))
            return 0;
        block_len = EVP_CIPHER_CTX_get_block_size(ctx->cctx);
        if (block_len == 0)
            return 0;
        memset(ctx->tbl, 0, block_len);
        ctx->nlast_block = 0;
        return 1;
    }
    /* Initialise context */
    if (cipher != NULL) {
        /* Ensure we can't use this ctx until we also have a key */
        ctx->nlast_block = -1;
        if (!EVP_EncryptInit_ex2(ctx->cctx, cipher, NULL, NULL, param))
            return 0;
    }
    /* Non-NULL key means initialisation complete */
    if (key != NULL) {
        int bl;

        /* If anything fails then ensure we can't use this ctx */
        ctx->nlast_block = -1;
        if (EVP_CIPHER_CTX_get0_cipher(ctx->cctx) == NULL)
            return 0;
        if (keylen > INT_MAX
            || EVP_CIPHER_CTX_set_key_length(ctx->cctx, (int)keylen) <= 0)
            return 0;
        if (!EVP_EncryptInit_ex2(ctx->cctx, NULL, key, zero_iv, param))
            return 0;
        if ((bl = EVP_CIPHER_CTX_get_block_size(ctx->cctx)) < 0)
            return 0;
        if (EVP_Cipher(ctx->cctx, ctx->tbl, zero_iv, bl) <= 0)
            return 0;
        make_kn(ctx->k1, ctx->tbl, bl);
        make_kn(ctx->k2, ctx->k1, bl);
        OPENSSL_cleanse(ctx->tbl, bl);
        /* Reset context again ready for first data block */
        if (!EVP_EncryptInit_ex2(ctx->cctx, NULL, NULL, zero_iv, param))
            return 0;
        /* Zero tbl so resume works */
        memset(ctx->tbl, 0, bl);
        ctx->nlast_block = 0;
    }
    return 1;
}

int CMAC_Init(CMAC_CTX *ctx, const void *key, size_t keylen,
              const EVP_CIPHER *cipher, ENGINE *impl)
{
    if (!ossl_assert(impl == NULL))
        return 0;
    return ossl_cmac_init(ctx, key, keylen, cipher, NULL);
}

int CMAC_Update(CMAC_CTX *ctx, const void *in, size_t dlen)
{
    const unsigned char *data = in;
    int bl;
    size_t max_burst_blocks, cipher_blocks;
    unsigned char buf[LOCAL_BUF_SIZE];

    if (ctx->nlast_block == -1)
        return 0;
    if (dlen == 0)
        return 1;
    if ((bl = EVP_CIPHER_CTX_get_block_size(ctx->cctx)) == 0)
        return 0;
    /* Copy into partial block if we need to */
    if (ctx->nlast_block > 0) {
        size_t nleft;

        nleft = bl - ctx->nlast_block;
        if (dlen < nleft)
            nleft = dlen;
        memcpy(ctx->last_block + ctx->nlast_block, data, nleft);
        dlen -= nleft;
        ctx->nlast_block += (int)nleft;
        /* If no more to process return */
        if (dlen == 0)
            return 1;
        data += nleft;
        /* Else not final block so encrypt it */
        if (EVP_Cipher(ctx->cctx, ctx->tbl, ctx->last_block, bl) <= 0)
            return 0;
    }
    /* Encrypt all but one of the complete blocks left */

    max_burst_blocks = LOCAL_BUF_SIZE / bl;
    cipher_blocks = (dlen - 1) / bl;
    if (max_burst_blocks == 0) {
        /*
         * When block length is greater than local buffer size,
         * use ctx->tbl as cipher output.
         */
        while (dlen > (size_t)bl) {
            if (EVP_Cipher(ctx->cctx, ctx->tbl, data, bl) <= 0)
                return 0;
            dlen -= bl;
            data += bl;
        }
    } else {
        while (cipher_blocks > max_burst_blocks) {
            if (EVP_Cipher(ctx->cctx, buf, data, (int)(max_burst_blocks * bl)) <= 0)
                return 0;
            dlen -= max_burst_blocks * bl;
            data += max_burst_blocks * bl;
            cipher_blocks -= max_burst_blocks;
        }
        if (cipher_blocks > 0) {
            if (EVP_Cipher(ctx->cctx, buf, data, (int)(cipher_blocks * bl)) <= 0)
                return 0;
            dlen -= cipher_blocks * bl;
            data += cipher_blocks * bl;
            memcpy(ctx->tbl, &buf[(cipher_blocks - 1) * bl], bl);
        }
    }
    /* Copy any data left to last block buffer */
    memcpy(ctx->last_block, data, dlen);
    ctx->nlast_block = (int)dlen;
    return 1;

}

int CMAC_Final(CMAC_CTX *ctx, unsigned char *out, size_t *poutlen)
{
    int i, bl, lb;

    if (ctx->nlast_block == -1)
        return 0;
    if ((bl = EVP_CIPHER_CTX_get_block_size(ctx->cctx)) == 0)
        return 0;
    if (poutlen != NULL)
        *poutlen = (size_t)bl;
    if (!out)
        return 1;
    lb = ctx->nlast_block;
    /* Is last block complete? */
    if (lb == bl) {
        for (i = 0; i < bl; i++)
            out[i] = ctx->last_block[i] ^ ctx->k1[i];
    } else {
        ctx->last_block[lb] = 0x80;
        if (bl - lb > 1)
            memset(ctx->last_block + lb + 1, 0, bl - lb - 1);
        for (i = 0; i < bl; i++)
            out[i] = ctx->last_block[i] ^ ctx->k2[i];
    }
    if (EVP_Cipher(ctx->cctx, out, out, bl) <= 0) {
        OPENSSL_cleanse(out, bl);
        return 0;
    }
    return 1;
}

int CMAC_resume(CMAC_CTX *ctx)
{
    if (ctx->nlast_block == -1)
        return 0;
    /*
     * The buffer "tbl" contains the last fully encrypted block which is the
     * last IV (or all zeroes if no last encrypted block). The last block has
     * not been modified since CMAC_final(). So reinitialising using the last
     * decrypted block will allow CMAC to continue after calling
     * CMAC_Final().
     */
    return EVP_EncryptInit_ex(ctx->cctx, NULL, NULL, NULL, ctx->tbl);
}

Coverage Report

Created: 2025-12-08 06:22

Line	Count	Source
1		/*
2		* Copyright 2010-2025 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		#include "internal/common.h"
24
25	0	#define LOCAL_BUF_SIZE 2048
26		struct CMAC_CTX_st {
27		/* Cipher context to use */
28		EVP_CIPHER_CTX *cctx;
29		/* Keys k1 and k2 */
30		unsigned char k1[EVP_MAX_BLOCK_LENGTH];
31		unsigned char k2[EVP_MAX_BLOCK_LENGTH];
32		/* Temporary block */
33		unsigned char tbl[EVP_MAX_BLOCK_LENGTH];
34		/* Last (possibly partial) block */
35		unsigned char last_block[EVP_MAX_BLOCK_LENGTH];
36		/* Number of bytes in last block: -1 means context not initialised */
37		int nlast_block;
38		};
39
40		/* Make temporary keys K1 and K2 */
41
42		static void make_kn(unsigned char k1, const unsigned char l, int bl)
43	0	{
44	0	int i;
45	0	unsigned char c = l[0], carry = c >> 7, cnext;
46
47		/* Shift block to left, including carry */
48	0	for (i = 0; i < bl - 1; i++, c = cnext)
49	0	k1[i] = (c << 1) \| ((cnext = l[i + 1]) >> 7);
50
51		/* If MSB set fixup with R */
52	0	k1[i] = (c << 1) ^ ((0 - carry) & (bl == 16 ? 0x87 : 0x1b));
53	0	}
54
55		CMAC_CTX *CMAC_CTX_new(void)
56	0	{
57	0	CMAC_CTX *ctx;
58
59	0	if ((ctx = OPENSSL_malloc(sizeof(*ctx))) == NULL)
60	0	return NULL;
61	0	ctx->cctx = EVP_CIPHER_CTX_new();
62	0	if (ctx->cctx == NULL) {
63	0	OPENSSL_free(ctx);
64	0	return NULL;
65	0	}
66	0	ctx->nlast_block = -1;
67	0	return ctx;
68	0	}
69
70		void CMAC_CTX_cleanup(CMAC_CTX *ctx)
71	0	{
72	0	EVP_CIPHER_CTX_reset(ctx->cctx);
73	0	OPENSSL_cleanse(ctx->tbl, EVP_MAX_BLOCK_LENGTH);
74	0	OPENSSL_cleanse(ctx->k1, EVP_MAX_BLOCK_LENGTH);
75	0	OPENSSL_cleanse(ctx->k2, EVP_MAX_BLOCK_LENGTH);
76	0	OPENSSL_cleanse(ctx->last_block, EVP_MAX_BLOCK_LENGTH);
77	0	ctx->nlast_block = -1;
78	0	}
79
80		EVP_CIPHER_CTX CMAC_CTX_get0_cipher_ctx(CMAC_CTX ctx)
81	0	{
82	0	return ctx->cctx;
83	0	}
84
85		void CMAC_CTX_free(CMAC_CTX *ctx)
86	0	{
87	0	if (!ctx)
88	0	return;
89	0	CMAC_CTX_cleanup(ctx);
90	0	EVP_CIPHER_CTX_free(ctx->cctx);
91	0	OPENSSL_free(ctx);
92	0	}
93
94		int CMAC_CTX_copy(CMAC_CTX out, const CMAC_CTX in)
95	0	{
96	0	int bl;
97
98	0	if (in->nlast_block == -1)
99	0	return 0;
100	0	if ((bl = EVP_CIPHER_CTX_get_block_size(in->cctx)) == 0)
101	0	return 0;
102	0	if (!EVP_CIPHER_CTX_copy(out->cctx, in->cctx))
103	0	return 0;
104	0	memcpy(out->k1, in->k1, bl);
105	0	memcpy(out->k2, in->k2, bl);
106	0	memcpy(out->tbl, in->tbl, bl);
107	0	memcpy(out->last_block, in->last_block, bl);
108	0	out->nlast_block = in->nlast_block;
109	0	return 1;
110	0	}
111
112		int ossl_cmac_init(CMAC_CTX ctx, const void key, size_t keylen,
113		const EVP_CIPHER *cipher, const OSSL_PARAM param[])
114	0	{
115	0	static const unsigned char zero_iv[EVP_MAX_BLOCK_LENGTH] = { 0 };
116	0	int block_len;
117
118		/* All zeros means restart */
119	0	if (key == NULL && cipher == NULL && keylen == 0) {
120		/* Not initialised */
121	0	if (ctx->nlast_block == -1)
122	0	return 0;
123	0	if (!EVP_EncryptInit_ex2(ctx->cctx, NULL, NULL, zero_iv, param))
124	0	return 0;
125	0	block_len = EVP_CIPHER_CTX_get_block_size(ctx->cctx);
126	0	if (block_len == 0)
127	0	return 0;
128	0	memset(ctx->tbl, 0, block_len);
129	0	ctx->nlast_block = 0;
130	0	return 1;
131	0	}
132		/* Initialise context */
133	0	if (cipher != NULL) {
134		/* Ensure we can't use this ctx until we also have a key */
135	0	ctx->nlast_block = -1;
136	0	if (!EVP_EncryptInit_ex2(ctx->cctx, cipher, NULL, NULL, param))
137	0	return 0;
138	0	}
139		/* Non-NULL key means initialisation complete */
140	0	if (key != NULL) {
141	0	int bl;
142
143		/* If anything fails then ensure we can't use this ctx */
144	0	ctx->nlast_block = -1;
145	0	if (EVP_CIPHER_CTX_get0_cipher(ctx->cctx) == NULL)
146	0	return 0;
147	0	if (keylen > INT_MAX
148	0	\|\| EVP_CIPHER_CTX_set_key_length(ctx->cctx, (int)keylen) <= 0)
149	0	return 0;
150	0	if (!EVP_EncryptInit_ex2(ctx->cctx, NULL, key, zero_iv, param))
151	0	return 0;
152	0	if ((bl = EVP_CIPHER_CTX_get_block_size(ctx->cctx)) < 0)
153	0	return 0;
154	0	if (EVP_Cipher(ctx->cctx, ctx->tbl, zero_iv, bl) <= 0)
155	0	return 0;
156	0	make_kn(ctx->k1, ctx->tbl, bl);
157	0	make_kn(ctx->k2, ctx->k1, bl);
158	0	OPENSSL_cleanse(ctx->tbl, bl);
159		/* Reset context again ready for first data block */
160	0	if (!EVP_EncryptInit_ex2(ctx->cctx, NULL, NULL, zero_iv, param))
161	0	return 0;
162		/* Zero tbl so resume works */
163	0	memset(ctx->tbl, 0, bl);
164	0	ctx->nlast_block = 0;
165	0	}
166	0	return 1;
167	0	}
168
169		int CMAC_Init(CMAC_CTX ctx, const void key, size_t keylen,
170		const EVP_CIPHER cipher, ENGINE impl)
171	0	{
172	0	if (!ossl_assert(impl == NULL))
173	0	return 0;
174	0	return ossl_cmac_init(ctx, key, keylen, cipher, NULL);
175	0	}
176
177		int CMAC_Update(CMAC_CTX ctx, const void in, size_t dlen)
178	0	{
179	0	const unsigned char *data = in;
180	0	int bl;
181	0	size_t max_burst_blocks, cipher_blocks;
182	0	unsigned char buf[LOCAL_BUF_SIZE];
183
184	0	if (ctx->nlast_block == -1)
185	0	return 0;
186	0	if (dlen == 0)
187	0	return 1;
188	0	if ((bl = EVP_CIPHER_CTX_get_block_size(ctx->cctx)) == 0)
189	0	return 0;
190		/* Copy into partial block if we need to */
191	0	if (ctx->nlast_block > 0) {
192	0	size_t nleft;
193
194	0	nleft = bl - ctx->nlast_block;
195	0	if (dlen < nleft)
196	0	nleft = dlen;
197	0	memcpy(ctx->last_block + ctx->nlast_block, data, nleft);
198	0	dlen -= nleft;
199	0	ctx->nlast_block += (int)nleft;
200		/* If no more to process return */
201	0	if (dlen == 0)
202	0	return 1;
203	0	data += nleft;
204		/* Else not final block so encrypt it */
205	0	if (EVP_Cipher(ctx->cctx, ctx->tbl, ctx->last_block, bl) <= 0)
206	0	return 0;
207	0	}
208		/* Encrypt all but one of the complete blocks left */
209
210	0	max_burst_blocks = LOCAL_BUF_SIZE / bl;
211	0	cipher_blocks = (dlen - 1) / bl;
212	0	if (max_burst_blocks == 0) {
213		/*
214		* When block length is greater than local buffer size,
215		* use ctx->tbl as cipher output.
216		*/
217	0	while (dlen > (size_t)bl) {
218	0	if (EVP_Cipher(ctx->cctx, ctx->tbl, data, bl) <= 0)
219	0	return 0;
220	0	dlen -= bl;
221	0	data += bl;
222	0	}
223	0	} else {
224	0	while (cipher_blocks > max_burst_blocks) {
225	0	if (EVP_Cipher(ctx->cctx, buf, data, (int)(max_burst_blocks * bl)) <= 0)
226	0	return 0;
227	0	dlen -= max_burst_blocks * bl;
228	0	data += max_burst_blocks * bl;
229	0	cipher_blocks -= max_burst_blocks;
230	0	}
231	0	if (cipher_blocks > 0) {
232	0	if (EVP_Cipher(ctx->cctx, buf, data, (int)(cipher_blocks * bl)) <= 0)
233	0	return 0;
234	0	dlen -= cipher_blocks * bl;
235	0	data += cipher_blocks * bl;
236	0	memcpy(ctx->tbl, &buf[(cipher_blocks - 1) * bl], bl);
237	0	}
238	0	}
239		/* Copy any data left to last block buffer */
240	0	memcpy(ctx->last_block, data, dlen);
241	0	ctx->nlast_block = (int)dlen;
242	0	return 1;
243
244	0	}
245
246		int CMAC_Final(CMAC_CTX ctx, unsigned char out, size_t *poutlen)
247	0	{
248	0	int i, bl, lb;
249
250	0	if (ctx->nlast_block == -1)
251	0	return 0;
252	0	if ((bl = EVP_CIPHER_CTX_get_block_size(ctx->cctx)) == 0)
253	0	return 0;
254	0	if (poutlen != NULL)
255	0	*poutlen = (size_t)bl;
256	0	if (!out)
257	0	return 1;
258	0	lb = ctx->nlast_block;
259		/* Is last block complete? */
260	0	if (lb == bl) {
261	0	for (i = 0; i < bl; i++)
262	0	out[i] = ctx->last_block[i] ^ ctx->k1[i];
263	0	} else {
264	0	ctx->last_block[lb] = 0x80;
265	0	if (bl - lb > 1)
266	0	memset(ctx->last_block + lb + 1, 0, bl - lb - 1);
267	0	for (i = 0; i < bl; i++)
268	0	out[i] = ctx->last_block[i] ^ ctx->k2[i];
269	0	}
270	0	if (EVP_Cipher(ctx->cctx, out, out, bl) <= 0) {
271	0	OPENSSL_cleanse(out, bl);
272	0	return 0;
273	0	}
274	0	return 1;
275	0	}
276
277		int CMAC_resume(CMAC_CTX *ctx)
278	0	{
279	0	if (ctx->nlast_block == -1)
280	0	return 0;
281		/*
282		* The buffer "tbl" contains the last fully encrypted block which is the
283		* last IV (or all zeroes if no last encrypted block). The last block has
284		* not been modified since CMAC_final(). So reinitialising using the last
285		* decrypted block will allow CMAC to continue after calling
286		* CMAC_Final().
287		*/
288	0	return EVP_EncryptInit_ex(ctx->cctx, NULL, NULL, NULL, ctx->tbl);
289	0	}