2 * Copyright 2014-2018 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the OpenSSL license (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
11 #include <openssl/crypto.h>
12 #include <openssl/err.h>
13 #include "modes_lcl.h"
15 #ifndef OPENSSL_NO_OCB
18 * Calculate the number of binary trailing zero's in any given number
20 static u32 ocb_ntz(u64 n)
25 * We do a right-to-left simple sequential search. This is surprisingly
26 * efficient as the distribution of trailing zeros is not uniform,
27 * e.g. the number of possible inputs with no trailing zeros is equal to
28 * the number with 1 or more; the number with exactly 1 is equal to the
29 * number with 2 or more, etc. Checking the last two bits covers 75% of
30 * all numbers. Checking the last three covers 87.5%
40 * Shift a block of 16 bytes left by shift bits
42 static void ocb_block_lshift(const unsigned char *in, size_t shift,
45 unsigned char shift_mask;
47 unsigned char mask[15];
50 shift_mask <<= (8 - shift);
51 for (i = 15; i >= 0; i--) {
53 mask[i - 1] = in[i] & shift_mask;
54 mask[i - 1] >>= 8 - shift;
56 out[i] = in[i] << shift;
65 * Perform a "double" operation as per OCB spec
67 static void ocb_double(OCB_BLOCK *in, OCB_BLOCK *out)
72 * Calculate the mask based on the most significant bit. There are more
73 * efficient ways to do this - but this way is constant time
75 mask = in->c[0] & 0x80;
79 ocb_block_lshift(in->c, 1, out->c);
85 * Perform an xor on in1 and in2 - each of len bytes. Store result in out
87 static void ocb_block_xor(const unsigned char *in1,
88 const unsigned char *in2, size_t len,
92 for (i = 0; i < len; i++) {
93 out[i] = in1[i] ^ in2[i];
98 * Lookup L_index in our lookup table. If we haven't already got it we need to
101 static OCB_BLOCK *ocb_lookup_l(OCB128_CONTEXT *ctx, size_t idx)
103 size_t l_index = ctx->l_index;
105 if (idx <= l_index) {
109 /* We don't have it - so calculate it */
110 if (idx >= ctx->max_l_index) {
113 * Each additional entry allows to process almost double as
114 * much data, so that in linear world the table will need to
115 * be expanded with smaller and smaller increments. Originally
116 * it was doubling in size, which was a waste. Growing it
117 * linearly is not formally optimal, but is simpler to implement.
118 * We grow table by minimally required 4*n that would accommodate
121 ctx->max_l_index += (idx - ctx->max_l_index + 4) & ~3;
123 OPENSSL_realloc(ctx->l, ctx->max_l_index * sizeof(OCB_BLOCK));
124 if (tmp_ptr == NULL) /* prevent ctx->l from being clobbered */
128 while (l_index < idx) {
129 ocb_double(ctx->l + l_index, ctx->l + l_index + 1);
132 ctx->l_index = l_index;
138 * Create a new OCB128_CONTEXT
140 OCB128_CONTEXT *CRYPTO_ocb128_new(void *keyenc, void *keydec,
141 block128_f encrypt, block128_f decrypt,
144 OCB128_CONTEXT *octx;
147 if ((octx = OPENSSL_malloc(sizeof(*octx))) != NULL) {
148 ret = CRYPTO_ocb128_init(octx, keyenc, keydec, encrypt, decrypt,
159 * Initialise an existing OCB128_CONTEXT
161 int CRYPTO_ocb128_init(OCB128_CONTEXT *ctx, void *keyenc, void *keydec,
162 block128_f encrypt, block128_f decrypt,
165 memset(ctx, 0, sizeof(*ctx));
167 ctx->max_l_index = 5;
168 if ((ctx->l = OPENSSL_malloc(ctx->max_l_index * 16)) == NULL) {
169 CRYPTOerr(CRYPTO_F_CRYPTO_OCB128_INIT, ERR_R_MALLOC_FAILURE);
174 * We set both the encryption and decryption key schedules - decryption
175 * needs both. Don't really need decryption schedule if only doing
176 * encryption - but it simplifies things to take it anyway
178 ctx->encrypt = encrypt;
179 ctx->decrypt = decrypt;
180 ctx->stream = stream;
181 ctx->keyenc = keyenc;
182 ctx->keydec = keydec;
184 /* L_* = ENCIPHER(K, zeros(128)) */
185 ctx->encrypt(ctx->l_star.c, ctx->l_star.c, ctx->keyenc);
187 /* L_$ = double(L_*) */
188 ocb_double(&ctx->l_star, &ctx->l_dollar);
190 /* L_0 = double(L_$) */
191 ocb_double(&ctx->l_dollar, ctx->l);
193 /* L_{i} = double(L_{i-1}) */
194 ocb_double(ctx->l, ctx->l+1);
195 ocb_double(ctx->l+1, ctx->l+2);
196 ocb_double(ctx->l+2, ctx->l+3);
197 ocb_double(ctx->l+3, ctx->l+4);
198 ctx->l_index = 4; /* enough to process up to 496 bytes */
204 * Copy an OCB128_CONTEXT object
206 int CRYPTO_ocb128_copy_ctx(OCB128_CONTEXT *dest, OCB128_CONTEXT *src,
207 void *keyenc, void *keydec)
209 memcpy(dest, src, sizeof(OCB128_CONTEXT));
211 dest->keyenc = keyenc;
213 dest->keydec = keydec;
215 if ((dest->l = OPENSSL_malloc(src->max_l_index * 16)) == NULL) {
216 CRYPTOerr(CRYPTO_F_CRYPTO_OCB128_COPY_CTX, ERR_R_MALLOC_FAILURE);
219 memcpy(dest->l, src->l, (src->l_index + 1) * 16);
225 * Set the IV to be used for this operation. Must be 1 - 15 bytes.
227 int CRYPTO_ocb128_setiv(OCB128_CONTEXT *ctx, const unsigned char *iv,
228 size_t len, size_t taglen)
230 unsigned char ktop[16], tmp[16], mask;
231 unsigned char stretch[24], nonce[16];
232 size_t bottom, shift;
235 * Spec says IV is 120 bits or fewer - it allows non byte aligned lengths.
236 * We don't support this at this stage
238 if ((len > 15) || (len < 1) || (taglen > 16) || (taglen < 1)) {
242 /* Reset nonce-dependent variables */
243 memset(&ctx->sess, 0, sizeof(ctx->sess));
245 /* Nonce = num2str(TAGLEN mod 128,7) || zeros(120-bitlen(N)) || 1 || N */
246 nonce[0] = ((taglen * 8) % 128) << 1;
247 memset(nonce + 1, 0, 15);
248 memcpy(nonce + 16 - len, iv, len);
249 nonce[15 - len] |= 1;
251 /* Ktop = ENCIPHER(K, Nonce[1..122] || zeros(6)) */
252 memcpy(tmp, nonce, 16);
254 ctx->encrypt(tmp, ktop, ctx->keyenc);
256 /* Stretch = Ktop || (Ktop[1..64] xor Ktop[9..72]) */
257 memcpy(stretch, ktop, 16);
258 ocb_block_xor(ktop, ktop + 1, 8, stretch + 16);
260 /* bottom = str2num(Nonce[123..128]) */
261 bottom = nonce[15] & 0x3f;
263 /* Offset_0 = Stretch[1+bottom..128+bottom] */
265 ocb_block_lshift(stretch + (bottom / 8), shift, ctx->sess.offset.c);
268 ctx->sess.offset.c[15] |=
269 (*(stretch + (bottom / 8) + 16) & mask) >> (8 - shift);
275 * Provide any AAD. This can be called multiple times. Only the final time can
276 * have a partial block
278 int CRYPTO_ocb128_aad(OCB128_CONTEXT *ctx, const unsigned char *aad,
281 u64 i, all_num_blocks;
282 size_t num_blocks, last_len;
285 /* Calculate the number of blocks of AAD provided now, and so far */
286 num_blocks = len / 16;
287 all_num_blocks = num_blocks + ctx->sess.blocks_hashed;
289 /* Loop through all full blocks of AAD */
290 for (i = ctx->sess.blocks_hashed + 1; i <= all_num_blocks; i++) {
293 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
294 lookup = ocb_lookup_l(ctx, ocb_ntz(i));
297 ocb_block16_xor(&ctx->sess.offset_aad, lookup, &ctx->sess.offset_aad);
299 memcpy(tmp.c, aad, 16);
302 /* Sum_i = Sum_{i-1} xor ENCIPHER(K, A_i xor Offset_i) */
303 ocb_block16_xor(&ctx->sess.offset_aad, &tmp, &tmp);
304 ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
305 ocb_block16_xor(&tmp, &ctx->sess.sum, &ctx->sess.sum);
309 * Check if we have any partial blocks left over. This is only valid in the
310 * last call to this function
315 /* Offset_* = Offset_m xor L_* */
316 ocb_block16_xor(&ctx->sess.offset_aad, &ctx->l_star,
317 &ctx->sess.offset_aad);
319 /* CipherInput = (A_* || 1 || zeros(127-bitlen(A_*))) xor Offset_* */
320 memset(tmp.c, 0, 16);
321 memcpy(tmp.c, aad, last_len);
322 tmp.c[last_len] = 0x80;
323 ocb_block16_xor(&ctx->sess.offset_aad, &tmp, &tmp);
325 /* Sum = Sum_m xor ENCIPHER(K, CipherInput) */
326 ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
327 ocb_block16_xor(&tmp, &ctx->sess.sum, &ctx->sess.sum);
330 ctx->sess.blocks_hashed = all_num_blocks;
336 * Provide any data to be encrypted. This can be called multiple times. Only
337 * the final time can have a partial block
339 int CRYPTO_ocb128_encrypt(OCB128_CONTEXT *ctx,
340 const unsigned char *in, unsigned char *out,
343 u64 i, all_num_blocks;
344 size_t num_blocks, last_len;
347 * Calculate the number of blocks of data to be encrypted provided now, and
350 num_blocks = len / 16;
351 all_num_blocks = num_blocks + ctx->sess.blocks_processed;
353 if (num_blocks && all_num_blocks == (size_t)all_num_blocks
354 && ctx->stream != NULL) {
355 size_t max_idx = 0, top = (size_t)all_num_blocks;
358 * See how many L_{i} entries we need to process data at hand
359 * and pre-compute missing entries in the table [if any]...
363 if (ocb_lookup_l(ctx, max_idx) == NULL)
366 ctx->stream(in, out, num_blocks, ctx->keyenc,
367 (size_t)ctx->sess.blocks_processed + 1, ctx->sess.offset.c,
368 (const unsigned char (*)[16])ctx->l, ctx->sess.checksum.c);
370 /* Loop through all full blocks to be encrypted */
371 for (i = ctx->sess.blocks_processed + 1; i <= all_num_blocks; i++) {
375 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
376 lookup = ocb_lookup_l(ctx, ocb_ntz(i));
379 ocb_block16_xor(&ctx->sess.offset, lookup, &ctx->sess.offset);
381 memcpy(tmp.c, in, 16);
384 /* Checksum_i = Checksum_{i-1} xor P_i */
385 ocb_block16_xor(&tmp, &ctx->sess.checksum, &ctx->sess.checksum);
387 /* C_i = Offset_i xor ENCIPHER(K, P_i xor Offset_i) */
388 ocb_block16_xor(&ctx->sess.offset, &tmp, &tmp);
389 ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
390 ocb_block16_xor(&ctx->sess.offset, &tmp, &tmp);
392 memcpy(out, tmp.c, 16);
398 * Check if we have any partial blocks left over. This is only valid in the
399 * last call to this function
406 /* Offset_* = Offset_m xor L_* */
407 ocb_block16_xor(&ctx->sess.offset, &ctx->l_star, &ctx->sess.offset);
409 /* Pad = ENCIPHER(K, Offset_*) */
410 ctx->encrypt(ctx->sess.offset.c, pad.c, ctx->keyenc);
412 /* C_* = P_* xor Pad[1..bitlen(P_*)] */
413 ocb_block_xor(in, pad.c, last_len, out);
415 /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
416 memset(pad.c, 0, 16); /* borrow pad */
417 memcpy(pad.c, in, last_len);
418 pad.c[last_len] = 0x80;
419 ocb_block16_xor(&pad, &ctx->sess.checksum, &ctx->sess.checksum);
422 ctx->sess.blocks_processed = all_num_blocks;
428 * Provide any data to be decrypted. This can be called multiple times. Only
429 * the final time can have a partial block
431 int CRYPTO_ocb128_decrypt(OCB128_CONTEXT *ctx,
432 const unsigned char *in, unsigned char *out,
435 u64 i, all_num_blocks;
436 size_t num_blocks, last_len;
439 * Calculate the number of blocks of data to be decrypted provided now, and
442 num_blocks = len / 16;
443 all_num_blocks = num_blocks + ctx->sess.blocks_processed;
445 if (num_blocks && all_num_blocks == (size_t)all_num_blocks
446 && ctx->stream != NULL) {
447 size_t max_idx = 0, top = (size_t)all_num_blocks;
450 * See how many L_{i} entries we need to process data at hand
451 * and pre-compute missing entries in the table [if any]...
455 if (ocb_lookup_l(ctx, max_idx) == NULL)
458 ctx->stream(in, out, num_blocks, ctx->keydec,
459 (size_t)ctx->sess.blocks_processed + 1, ctx->sess.offset.c,
460 (const unsigned char (*)[16])ctx->l, ctx->sess.checksum.c);
464 /* Loop through all full blocks to be decrypted */
465 for (i = ctx->sess.blocks_processed + 1; i <= all_num_blocks; i++) {
467 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
468 OCB_BLOCK *lookup = ocb_lookup_l(ctx, ocb_ntz(i));
471 ocb_block16_xor(&ctx->sess.offset, lookup, &ctx->sess.offset);
473 memcpy(tmp.c, in, 16);
476 /* P_i = Offset_i xor DECIPHER(K, C_i xor Offset_i) */
477 ocb_block16_xor(&ctx->sess.offset, &tmp, &tmp);
478 ctx->decrypt(tmp.c, tmp.c, ctx->keydec);
479 ocb_block16_xor(&ctx->sess.offset, &tmp, &tmp);
481 /* Checksum_i = Checksum_{i-1} xor P_i */
482 ocb_block16_xor(&tmp, &ctx->sess.checksum, &ctx->sess.checksum);
484 memcpy(out, tmp.c, 16);
490 * Check if we have any partial blocks left over. This is only valid in the
491 * last call to this function
498 /* Offset_* = Offset_m xor L_* */
499 ocb_block16_xor(&ctx->sess.offset, &ctx->l_star, &ctx->sess.offset);
501 /* Pad = ENCIPHER(K, Offset_*) */
502 ctx->encrypt(ctx->sess.offset.c, pad.c, ctx->keyenc);
504 /* P_* = C_* xor Pad[1..bitlen(C_*)] */
505 ocb_block_xor(in, pad.c, last_len, out);
507 /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
508 memset(pad.c, 0, 16); /* borrow pad */
509 memcpy(pad.c, out, last_len);
510 pad.c[last_len] = 0x80;
511 ocb_block16_xor(&pad, &ctx->sess.checksum, &ctx->sess.checksum);
514 ctx->sess.blocks_processed = all_num_blocks;
519 static int ocb_finish(OCB128_CONTEXT *ctx, unsigned char *tag, size_t len,
524 if (len > 16 || len < 1) {
529 * Tag = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) xor HASH(K,A)
531 ocb_block16_xor(&ctx->sess.checksum, &ctx->sess.offset, &tmp);
532 ocb_block16_xor(&ctx->l_dollar, &tmp, &tmp);
533 ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
534 ocb_block16_xor(&tmp, &ctx->sess.sum, &tmp);
537 memcpy(tag, &tmp, len);
540 return CRYPTO_memcmp(&tmp, tag, len);
545 * Calculate the tag and verify it against the supplied tag
547 int CRYPTO_ocb128_finish(OCB128_CONTEXT *ctx, const unsigned char *tag,
550 return ocb_finish(ctx, (unsigned char*)tag, len, 0);
554 * Retrieve the calculated tag
556 int CRYPTO_ocb128_tag(OCB128_CONTEXT *ctx, unsigned char *tag, size_t len)
558 return ocb_finish(ctx, tag, len, 1);
562 * Release all resources
564 void CRYPTO_ocb128_cleanup(OCB128_CONTEXT *ctx)
567 OPENSSL_clear_free(ctx->l, ctx->max_l_index * 16);
568 OPENSSL_cleanse(ctx, sizeof(*ctx));
572 #endif /* OPENSSL_NO_OCB */