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 "modes_lcl.h"
14 #ifndef OPENSSL_NO_OCB
17 * Calculate the number of binary trailing zero's in any given number
19 static u32 ocb_ntz(u64 n)
24 * We do a right-to-left simple sequential search. This is surprisingly
25 * efficient as the distribution of trailing zeros is not uniform,
26 * e.g. the number of possible inputs with no trailing zeros is equal to
27 * the number with 1 or more; the number with exactly 1 is equal to the
28 * number with 2 or more, etc. Checking the last two bits covers 75% of
29 * all numbers. Checking the last three covers 87.5%
39 * Shift a block of 16 bytes left by shift bits
41 static void ocb_block_lshift(const unsigned char *in, size_t shift,
44 unsigned char shift_mask;
46 unsigned char mask[15];
49 shift_mask <<= (8 - shift);
50 for (i = 15; i >= 0; i--) {
52 mask[i - 1] = in[i] & shift_mask;
53 mask[i - 1] >>= 8 - shift;
55 out[i] = in[i] << shift;
64 * Perform a "double" operation as per OCB spec
66 static void ocb_double(OCB_BLOCK *in, OCB_BLOCK *out)
71 * Calculate the mask based on the most significant bit. There are more
72 * efficient ways to do this - but this way is constant time
74 mask = in->c[0] & 0x80;
78 ocb_block_lshift(in->c, 1, out->c);
84 * Perform an xor on in1 and in2 - each of len bytes. Store result in out
86 static void ocb_block_xor(const unsigned char *in1,
87 const unsigned char *in2, size_t len,
91 for (i = 0; i < len; i++) {
92 out[i] = in1[i] ^ in2[i];
97 * Lookup L_index in our lookup table. If we haven't already got it we need to
100 static OCB_BLOCK *ocb_lookup_l(OCB128_CONTEXT *ctx, size_t idx)
102 size_t l_index = ctx->l_index;
104 if (idx <= l_index) {
108 /* We don't have it - so calculate it */
109 if (idx >= ctx->max_l_index) {
112 * Each additional entry allows to process almost double as
113 * much data, so that in linear world the table will need to
114 * be expanded with smaller and smaller increments. Originally
115 * it was doubling in size, which was a waste. Growing it
116 * linearly is not formally optimal, but is simpler to implement.
117 * We grow table by minimally required 4*n that would accommodate
120 ctx->max_l_index += (idx - ctx->max_l_index + 4) & ~3;
122 OPENSSL_realloc(ctx->l, ctx->max_l_index * sizeof(OCB_BLOCK));
123 if (tmp_ptr == NULL) /* prevent ctx->l from being clobbered */
127 while (l_index < idx) {
128 ocb_double(ctx->l + l_index, ctx->l + l_index + 1);
131 ctx->l_index = l_index;
137 * Create a new OCB128_CONTEXT
139 OCB128_CONTEXT *CRYPTO_ocb128_new(void *keyenc, void *keydec,
140 block128_f encrypt, block128_f decrypt,
143 OCB128_CONTEXT *octx;
146 if ((octx = OPENSSL_malloc(sizeof(*octx))) != NULL) {
147 ret = CRYPTO_ocb128_init(octx, keyenc, keydec, encrypt, decrypt,
158 * Initialise an existing OCB128_CONTEXT
160 int CRYPTO_ocb128_init(OCB128_CONTEXT *ctx, void *keyenc, void *keydec,
161 block128_f encrypt, block128_f decrypt,
164 memset(ctx, 0, sizeof(*ctx));
166 ctx->max_l_index = 5;
167 ctx->l = OPENSSL_malloc(ctx->max_l_index * 16);
172 * We set both the encryption and decryption key schedules - decryption
173 * needs both. Don't really need decryption schedule if only doing
174 * encryption - but it simplifies things to take it anyway
176 ctx->encrypt = encrypt;
177 ctx->decrypt = decrypt;
178 ctx->stream = stream;
179 ctx->keyenc = keyenc;
180 ctx->keydec = keydec;
182 /* L_* = ENCIPHER(K, zeros(128)) */
183 ctx->encrypt(ctx->l_star.c, ctx->l_star.c, ctx->keyenc);
185 /* L_$ = double(L_*) */
186 ocb_double(&ctx->l_star, &ctx->l_dollar);
188 /* L_0 = double(L_$) */
189 ocb_double(&ctx->l_dollar, ctx->l);
191 /* L_{i} = double(L_{i-1}) */
192 ocb_double(ctx->l, ctx->l+1);
193 ocb_double(ctx->l+1, ctx->l+2);
194 ocb_double(ctx->l+2, ctx->l+3);
195 ocb_double(ctx->l+3, ctx->l+4);
196 ctx->l_index = 4; /* enough to process up to 496 bytes */
202 * Copy an OCB128_CONTEXT object
204 int CRYPTO_ocb128_copy_ctx(OCB128_CONTEXT *dest, OCB128_CONTEXT *src,
205 void *keyenc, void *keydec)
207 memcpy(dest, src, sizeof(OCB128_CONTEXT));
209 dest->keyenc = keyenc;
211 dest->keydec = keydec;
213 dest->l = OPENSSL_malloc(src->max_l_index * 16);
216 memcpy(dest->l, src->l, (src->l_index + 1) * 16);
222 * Set the IV to be used for this operation. Must be 1 - 15 bytes.
224 int CRYPTO_ocb128_setiv(OCB128_CONTEXT *ctx, const unsigned char *iv,
225 size_t len, size_t taglen)
227 unsigned char ktop[16], tmp[16], mask;
228 unsigned char stretch[24], nonce[16];
229 size_t bottom, shift;
232 * Spec says IV is 120 bits or fewer - it allows non byte aligned lengths.
233 * We don't support this at this stage
235 if ((len > 15) || (len < 1) || (taglen > 16) || (taglen < 1)) {
239 /* Nonce = num2str(TAGLEN mod 128,7) || zeros(120-bitlen(N)) || 1 || N */
240 nonce[0] = ((taglen * 8) % 128) << 1;
241 memset(nonce + 1, 0, 15);
242 memcpy(nonce + 16 - len, iv, len);
243 nonce[15 - len] |= 1;
245 /* Ktop = ENCIPHER(K, Nonce[1..122] || zeros(6)) */
246 memcpy(tmp, nonce, 16);
248 ctx->encrypt(tmp, ktop, ctx->keyenc);
250 /* Stretch = Ktop || (Ktop[1..64] xor Ktop[9..72]) */
251 memcpy(stretch, ktop, 16);
252 ocb_block_xor(ktop, ktop + 1, 8, stretch + 16);
254 /* bottom = str2num(Nonce[123..128]) */
255 bottom = nonce[15] & 0x3f;
257 /* Offset_0 = Stretch[1+bottom..128+bottom] */
259 ocb_block_lshift(stretch + (bottom / 8), shift, ctx->offset.c);
263 (*(stretch + (bottom / 8) + 16) & mask) >> (8 - shift);
269 * Provide any AAD. This can be called multiple times. Only the final time can
270 * have a partial block
272 int CRYPTO_ocb128_aad(OCB128_CONTEXT *ctx, const unsigned char *aad,
275 u64 i, all_num_blocks;
276 size_t num_blocks, last_len;
279 /* Calculate the number of blocks of AAD provided now, and so far */
280 num_blocks = len / 16;
281 all_num_blocks = num_blocks + ctx->blocks_hashed;
283 /* Loop through all full blocks of AAD */
284 for (i = ctx->blocks_hashed + 1; i <= all_num_blocks; i++) {
287 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
288 lookup = ocb_lookup_l(ctx, ocb_ntz(i));
291 ocb_block16_xor(&ctx->offset_aad, lookup, &ctx->offset_aad);
293 memcpy(tmp.c, aad, 16);
296 /* Sum_i = Sum_{i-1} xor ENCIPHER(K, A_i xor Offset_i) */
297 ocb_block16_xor(&ctx->offset_aad, &tmp, &tmp);
298 ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
299 ocb_block16_xor(&tmp, &ctx->sum, &ctx->sum);
303 * Check if we have any partial blocks left over. This is only valid in the
304 * last call to this function
309 /* Offset_* = Offset_m xor L_* */
310 ocb_block16_xor(&ctx->offset_aad, &ctx->l_star, &ctx->offset_aad);
312 /* CipherInput = (A_* || 1 || zeros(127-bitlen(A_*))) xor Offset_* */
313 memset(tmp.c, 0, 16);
314 memcpy(tmp.c, aad, last_len);
315 tmp.c[last_len] = 0x80;
316 ocb_block16_xor(&ctx->offset_aad, &tmp, &tmp);
318 /* Sum = Sum_m xor ENCIPHER(K, CipherInput) */
319 ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
320 ocb_block16_xor(&tmp, &ctx->sum, &ctx->sum);
323 ctx->blocks_hashed = all_num_blocks;
329 * Provide any data to be encrypted. This can be called multiple times. Only
330 * the final time can have a partial block
332 int CRYPTO_ocb128_encrypt(OCB128_CONTEXT *ctx,
333 const unsigned char *in, unsigned char *out,
336 u64 i, all_num_blocks;
337 size_t num_blocks, last_len;
340 * Calculate the number of blocks of data to be encrypted provided now, and
343 num_blocks = len / 16;
344 all_num_blocks = num_blocks + ctx->blocks_processed;
346 if (num_blocks && all_num_blocks == (size_t)all_num_blocks
347 && ctx->stream != NULL) {
348 size_t max_idx = 0, top = (size_t)all_num_blocks;
351 * See how many L_{i} entries we need to process data at hand
352 * and pre-compute missing entries in the table [if any]...
356 if (ocb_lookup_l(ctx, max_idx) == NULL)
359 ctx->stream(in, out, num_blocks, ctx->keyenc,
360 (size_t)ctx->blocks_processed + 1, ctx->offset.c,
361 (const unsigned char (*)[16])ctx->l, ctx->checksum.c);
363 /* Loop through all full blocks to be encrypted */
364 for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
368 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
369 lookup = ocb_lookup_l(ctx, ocb_ntz(i));
372 ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);
374 memcpy(tmp.c, in, 16);
377 /* Checksum_i = Checksum_{i-1} xor P_i */
378 ocb_block16_xor(&tmp, &ctx->checksum, &ctx->checksum);
380 /* C_i = Offset_i xor ENCIPHER(K, P_i xor Offset_i) */
381 ocb_block16_xor(&ctx->offset, &tmp, &tmp);
382 ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
383 ocb_block16_xor(&ctx->offset, &tmp, &tmp);
385 memcpy(out, tmp.c, 16);
391 * Check if we have any partial blocks left over. This is only valid in the
392 * last call to this function
399 /* Offset_* = Offset_m xor L_* */
400 ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);
402 /* Pad = ENCIPHER(K, Offset_*) */
403 ctx->encrypt(ctx->offset.c, pad.c, ctx->keyenc);
405 /* C_* = P_* xor Pad[1..bitlen(P_*)] */
406 ocb_block_xor(in, pad.c, last_len, out);
408 /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
409 memset(pad.c, 0, 16); /* borrow pad */
410 memcpy(pad.c, in, last_len);
411 pad.c[last_len] = 0x80;
412 ocb_block16_xor(&pad, &ctx->checksum, &ctx->checksum);
415 ctx->blocks_processed = all_num_blocks;
421 * Provide any data to be decrypted. This can be called multiple times. Only
422 * the final time can have a partial block
424 int CRYPTO_ocb128_decrypt(OCB128_CONTEXT *ctx,
425 const unsigned char *in, unsigned char *out,
428 u64 i, all_num_blocks;
429 size_t num_blocks, last_len;
432 * Calculate the number of blocks of data to be decrypted provided now, and
435 num_blocks = len / 16;
436 all_num_blocks = num_blocks + ctx->blocks_processed;
438 if (num_blocks && all_num_blocks == (size_t)all_num_blocks
439 && ctx->stream != NULL) {
440 size_t max_idx = 0, top = (size_t)all_num_blocks;
443 * See how many L_{i} entries we need to process data at hand
444 * and pre-compute missing entries in the table [if any]...
448 if (ocb_lookup_l(ctx, max_idx) == NULL)
451 ctx->stream(in, out, num_blocks, ctx->keydec,
452 (size_t)ctx->blocks_processed + 1, ctx->offset.c,
453 (const unsigned char (*)[16])ctx->l, ctx->checksum.c);
457 /* Loop through all full blocks to be decrypted */
458 for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
460 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
461 OCB_BLOCK *lookup = ocb_lookup_l(ctx, ocb_ntz(i));
464 ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);
466 memcpy(tmp.c, in, 16);
469 /* P_i = Offset_i xor DECIPHER(K, C_i xor Offset_i) */
470 ocb_block16_xor(&ctx->offset, &tmp, &tmp);
471 ctx->decrypt(tmp.c, tmp.c, ctx->keydec);
472 ocb_block16_xor(&ctx->offset, &tmp, &tmp);
474 /* Checksum_i = Checksum_{i-1} xor P_i */
475 ocb_block16_xor(&tmp, &ctx->checksum, &ctx->checksum);
477 memcpy(out, tmp.c, 16);
483 * Check if we have any partial blocks left over. This is only valid in the
484 * last call to this function
491 /* Offset_* = Offset_m xor L_* */
492 ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);
494 /* Pad = ENCIPHER(K, Offset_*) */
495 ctx->encrypt(ctx->offset.c, pad.c, ctx->keyenc);
497 /* P_* = C_* xor Pad[1..bitlen(C_*)] */
498 ocb_block_xor(in, pad.c, last_len, out);
500 /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
501 memset(pad.c, 0, 16); /* borrow pad */
502 memcpy(pad.c, out, last_len);
503 pad.c[last_len] = 0x80;
504 ocb_block16_xor(&pad, &ctx->checksum, &ctx->checksum);
507 ctx->blocks_processed = all_num_blocks;
513 * Calculate the tag and verify it against the supplied tag
515 int CRYPTO_ocb128_finish(OCB128_CONTEXT *ctx, const unsigned char *tag,
521 * Tag = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) xor HASH(K,A)
523 ocb_block16_xor(&ctx->checksum, &ctx->offset, &tmp);
524 ocb_block16_xor(&ctx->l_dollar, &tmp, &tmp);
525 ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
526 ocb_block16_xor(&tmp, &ctx->sum, &ctx->tag);
528 if (len > 16 || len < 1) {
532 /* Compare the tag if we've been given one */
534 return CRYPTO_memcmp(&ctx->tag, tag, len);
540 * Retrieve the calculated tag
542 int CRYPTO_ocb128_tag(OCB128_CONTEXT *ctx, unsigned char *tag, size_t len)
544 if (len > 16 || len < 1) {
548 /* Calculate the tag */
549 CRYPTO_ocb128_finish(ctx, NULL, 0);
551 /* Copy the tag into the supplied buffer */
552 memcpy(tag, ctx->tag.c, len);
558 * Release all resources
560 void CRYPTO_ocb128_cleanup(OCB128_CONTEXT *ctx)
563 OPENSSL_clear_free(ctx->l, ctx->max_l_index * 16);
564 OPENSSL_cleanse(ctx, sizeof(*ctx));
568 #endif /* OPENSSL_NO_OCB */