2 * Copyright 2014-2016 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 /* Nonce = num2str(TAGLEN mod 128,7) || zeros(120-bitlen(N)) || 1 || N */
243 nonce[0] = ((taglen * 8) % 128) << 1;
244 memset(nonce + 1, 0, 15);
245 memcpy(nonce + 16 - len, iv, len);
246 nonce[15 - len] |= 1;
248 /* Ktop = ENCIPHER(K, Nonce[1..122] || zeros(6)) */
249 memcpy(tmp, nonce, 16);
251 ctx->encrypt(tmp, ktop, ctx->keyenc);
253 /* Stretch = Ktop || (Ktop[1..64] xor Ktop[9..72]) */
254 memcpy(stretch, ktop, 16);
255 ocb_block_xor(ktop, ktop + 1, 8, stretch + 16);
257 /* bottom = str2num(Nonce[123..128]) */
258 bottom = nonce[15] & 0x3f;
260 /* Offset_0 = Stretch[1+bottom..128+bottom] */
262 ocb_block_lshift(stretch + (bottom / 8), shift, ctx->offset.c);
266 (*(stretch + (bottom / 8) + 16) & mask) >> (8 - shift);
272 * Provide any AAD. This can be called multiple times. Only the final time can
273 * have a partial block
275 int CRYPTO_ocb128_aad(OCB128_CONTEXT *ctx, const unsigned char *aad,
278 u64 i, all_num_blocks;
279 size_t num_blocks, last_len;
282 /* Calculate the number of blocks of AAD provided now, and so far */
283 num_blocks = len / 16;
284 all_num_blocks = num_blocks + ctx->blocks_hashed;
286 /* Loop through all full blocks of AAD */
287 for (i = ctx->blocks_hashed + 1; i <= all_num_blocks; i++) {
290 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
291 lookup = ocb_lookup_l(ctx, ocb_ntz(i));
294 ocb_block16_xor(&ctx->offset_aad, lookup, &ctx->offset_aad);
296 memcpy(tmp.c, aad, 16);
299 /* Sum_i = Sum_{i-1} xor ENCIPHER(K, A_i xor Offset_i) */
300 ocb_block16_xor(&ctx->offset_aad, &tmp, &tmp);
301 ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
302 ocb_block16_xor(&tmp, &ctx->sum, &ctx->sum);
306 * Check if we have any partial blocks left over. This is only valid in the
307 * last call to this function
312 /* Offset_* = Offset_m xor L_* */
313 ocb_block16_xor(&ctx->offset_aad, &ctx->l_star, &ctx->offset_aad);
315 /* CipherInput = (A_* || 1 || zeros(127-bitlen(A_*))) xor Offset_* */
316 memset(tmp.c, 0, 16);
317 memcpy(tmp.c, aad, last_len);
318 tmp.c[last_len] = 0x80;
319 ocb_block16_xor(&ctx->offset_aad, &tmp, &tmp);
321 /* Sum = Sum_m xor ENCIPHER(K, CipherInput) */
322 ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
323 ocb_block16_xor(&tmp, &ctx->sum, &ctx->sum);
326 ctx->blocks_hashed = all_num_blocks;
332 * Provide any data to be encrypted. This can be called multiple times. Only
333 * the final time can have a partial block
335 int CRYPTO_ocb128_encrypt(OCB128_CONTEXT *ctx,
336 const unsigned char *in, unsigned char *out,
339 u64 i, all_num_blocks;
340 size_t num_blocks, last_len;
343 * Calculate the number of blocks of data to be encrypted provided now, and
346 num_blocks = len / 16;
347 all_num_blocks = num_blocks + ctx->blocks_processed;
349 if (num_blocks && all_num_blocks == (size_t)all_num_blocks
350 && ctx->stream != NULL) {
351 size_t max_idx = 0, top = (size_t)all_num_blocks;
354 * See how many L_{i} entries we need to process data at hand
355 * and pre-compute missing entries in the table [if any]...
359 if (ocb_lookup_l(ctx, max_idx) == NULL)
362 ctx->stream(in, out, num_blocks, ctx->keyenc,
363 (size_t)ctx->blocks_processed + 1, ctx->offset.c,
364 (const unsigned char (*)[16])ctx->l, ctx->checksum.c);
366 /* Loop through all full blocks to be encrypted */
367 for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
371 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
372 lookup = ocb_lookup_l(ctx, ocb_ntz(i));
375 ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);
377 memcpy(tmp.c, in, 16);
380 /* Checksum_i = Checksum_{i-1} xor P_i */
381 ocb_block16_xor(&tmp, &ctx->checksum, &ctx->checksum);
383 /* C_i = Offset_i xor ENCIPHER(K, P_i xor Offset_i) */
384 ocb_block16_xor(&ctx->offset, &tmp, &tmp);
385 ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
386 ocb_block16_xor(&ctx->offset, &tmp, &tmp);
388 memcpy(out, tmp.c, 16);
394 * Check if we have any partial blocks left over. This is only valid in the
395 * last call to this function
402 /* Offset_* = Offset_m xor L_* */
403 ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);
405 /* Pad = ENCIPHER(K, Offset_*) */
406 ctx->encrypt(ctx->offset.c, pad.c, ctx->keyenc);
408 /* C_* = P_* xor Pad[1..bitlen(P_*)] */
409 ocb_block_xor(in, pad.c, last_len, out);
411 /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
412 memset(pad.c, 0, 16); /* borrow pad */
413 memcpy(pad.c, in, last_len);
414 pad.c[last_len] = 0x80;
415 ocb_block16_xor(&pad, &ctx->checksum, &ctx->checksum);
418 ctx->blocks_processed = all_num_blocks;
424 * Provide any data to be decrypted. This can be called multiple times. Only
425 * the final time can have a partial block
427 int CRYPTO_ocb128_decrypt(OCB128_CONTEXT *ctx,
428 const unsigned char *in, unsigned char *out,
431 u64 i, all_num_blocks;
432 size_t num_blocks, last_len;
435 * Calculate the number of blocks of data to be decrypted provided now, and
438 num_blocks = len / 16;
439 all_num_blocks = num_blocks + ctx->blocks_processed;
441 if (num_blocks && all_num_blocks == (size_t)all_num_blocks
442 && ctx->stream != NULL) {
443 size_t max_idx = 0, top = (size_t)all_num_blocks;
446 * See how many L_{i} entries we need to process data at hand
447 * and pre-compute missing entries in the table [if any]...
451 if (ocb_lookup_l(ctx, max_idx) == NULL)
454 ctx->stream(in, out, num_blocks, ctx->keydec,
455 (size_t)ctx->blocks_processed + 1, ctx->offset.c,
456 (const unsigned char (*)[16])ctx->l, ctx->checksum.c);
460 /* Loop through all full blocks to be decrypted */
461 for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
463 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
464 OCB_BLOCK *lookup = ocb_lookup_l(ctx, ocb_ntz(i));
467 ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);
469 memcpy(tmp.c, in, 16);
472 /* P_i = Offset_i xor DECIPHER(K, C_i xor Offset_i) */
473 ocb_block16_xor(&ctx->offset, &tmp, &tmp);
474 ctx->decrypt(tmp.c, tmp.c, ctx->keydec);
475 ocb_block16_xor(&ctx->offset, &tmp, &tmp);
477 /* Checksum_i = Checksum_{i-1} xor P_i */
478 ocb_block16_xor(&tmp, &ctx->checksum, &ctx->checksum);
480 memcpy(out, tmp.c, 16);
486 * Check if we have any partial blocks left over. This is only valid in the
487 * last call to this function
494 /* Offset_* = Offset_m xor L_* */
495 ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);
497 /* Pad = ENCIPHER(K, Offset_*) */
498 ctx->encrypt(ctx->offset.c, pad.c, ctx->keyenc);
500 /* P_* = C_* xor Pad[1..bitlen(C_*)] */
501 ocb_block_xor(in, pad.c, last_len, out);
503 /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
504 memset(pad.c, 0, 16); /* borrow pad */
505 memcpy(pad.c, out, last_len);
506 pad.c[last_len] = 0x80;
507 ocb_block16_xor(&pad, &ctx->checksum, &ctx->checksum);
510 ctx->blocks_processed = all_num_blocks;
516 * Calculate the tag and verify it against the supplied tag
518 int CRYPTO_ocb128_finish(OCB128_CONTEXT *ctx, const unsigned char *tag,
524 * Tag = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) xor HASH(K,A)
526 ocb_block16_xor(&ctx->checksum, &ctx->offset, &tmp);
527 ocb_block16_xor(&ctx->l_dollar, &tmp, &tmp);
528 ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
529 ocb_block16_xor(&tmp, &ctx->sum, &ctx->tag);
531 if (len > 16 || len < 1) {
535 /* Compare the tag if we've been given one */
537 return CRYPTO_memcmp(&ctx->tag, tag, len);
543 * Retrieve the calculated tag
545 int CRYPTO_ocb128_tag(OCB128_CONTEXT *ctx, unsigned char *tag, size_t len)
547 if (len > 16 || len < 1) {
551 /* Calculate the tag */
552 CRYPTO_ocb128_finish(ctx, NULL, 0);
554 /* Copy the tag into the supplied buffer */
555 memcpy(tag, ctx->tag.c, len);
561 * Release all resources
563 void CRYPTO_ocb128_cleanup(OCB128_CONTEXT *ctx)
566 OPENSSL_clear_free(ctx->l, ctx->max_l_index * 16);
567 OPENSSL_cleanse(ctx, sizeof(*ctx));
571 #endif /* OPENSSL_NO_OCB */