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 /* Reset nonce-dependent variables */
240 memset(&ctx->sess, 0, sizeof(ctx->sess));
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->sess.offset.c);
265 ctx->sess.offset.c[15] |=
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->sess.blocks_hashed;
286 /* Loop through all full blocks of AAD */
287 for (i = ctx->sess.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->sess.offset_aad, lookup, &ctx->sess.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->sess.offset_aad, &tmp, &tmp);
301 ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
302 ocb_block16_xor(&tmp, &ctx->sess.sum, &ctx->sess.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->sess.offset_aad, &ctx->l_star,
314 &ctx->sess.offset_aad);
316 /* CipherInput = (A_* || 1 || zeros(127-bitlen(A_*))) xor Offset_* */
317 memset(tmp.c, 0, 16);
318 memcpy(tmp.c, aad, last_len);
319 tmp.c[last_len] = 0x80;
320 ocb_block16_xor(&ctx->sess.offset_aad, &tmp, &tmp);
322 /* Sum = Sum_m xor ENCIPHER(K, CipherInput) */
323 ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
324 ocb_block16_xor(&tmp, &ctx->sess.sum, &ctx->sess.sum);
327 ctx->sess.blocks_hashed = all_num_blocks;
333 * Provide any data to be encrypted. This can be called multiple times. Only
334 * the final time can have a partial block
336 int CRYPTO_ocb128_encrypt(OCB128_CONTEXT *ctx,
337 const unsigned char *in, unsigned char *out,
340 u64 i, all_num_blocks;
341 size_t num_blocks, last_len;
344 * Calculate the number of blocks of data to be encrypted provided now, and
347 num_blocks = len / 16;
348 all_num_blocks = num_blocks + ctx->sess.blocks_processed;
350 if (num_blocks && all_num_blocks == (size_t)all_num_blocks
351 && ctx->stream != NULL) {
352 size_t max_idx = 0, top = (size_t)all_num_blocks;
355 * See how many L_{i} entries we need to process data at hand
356 * and pre-compute missing entries in the table [if any]...
360 if (ocb_lookup_l(ctx, max_idx) == NULL)
363 ctx->stream(in, out, num_blocks, ctx->keyenc,
364 (size_t)ctx->sess.blocks_processed + 1, ctx->sess.offset.c,
365 (const unsigned char (*)[16])ctx->l, ctx->sess.checksum.c);
367 /* Loop through all full blocks to be encrypted */
368 for (i = ctx->sess.blocks_processed + 1; i <= all_num_blocks; i++) {
372 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
373 lookup = ocb_lookup_l(ctx, ocb_ntz(i));
376 ocb_block16_xor(&ctx->sess.offset, lookup, &ctx->sess.offset);
378 memcpy(tmp.c, in, 16);
381 /* Checksum_i = Checksum_{i-1} xor P_i */
382 ocb_block16_xor(&tmp, &ctx->sess.checksum, &ctx->sess.checksum);
384 /* C_i = Offset_i xor ENCIPHER(K, P_i xor Offset_i) */
385 ocb_block16_xor(&ctx->sess.offset, &tmp, &tmp);
386 ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
387 ocb_block16_xor(&ctx->sess.offset, &tmp, &tmp);
389 memcpy(out, tmp.c, 16);
395 * Check if we have any partial blocks left over. This is only valid in the
396 * last call to this function
403 /* Offset_* = Offset_m xor L_* */
404 ocb_block16_xor(&ctx->sess.offset, &ctx->l_star, &ctx->sess.offset);
406 /* Pad = ENCIPHER(K, Offset_*) */
407 ctx->encrypt(ctx->sess.offset.c, pad.c, ctx->keyenc);
409 /* C_* = P_* xor Pad[1..bitlen(P_*)] */
410 ocb_block_xor(in, pad.c, last_len, out);
412 /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
413 memset(pad.c, 0, 16); /* borrow pad */
414 memcpy(pad.c, in, last_len);
415 pad.c[last_len] = 0x80;
416 ocb_block16_xor(&pad, &ctx->sess.checksum, &ctx->sess.checksum);
419 ctx->sess.blocks_processed = all_num_blocks;
425 * Provide any data to be decrypted. This can be called multiple times. Only
426 * the final time can have a partial block
428 int CRYPTO_ocb128_decrypt(OCB128_CONTEXT *ctx,
429 const unsigned char *in, unsigned char *out,
432 u64 i, all_num_blocks;
433 size_t num_blocks, last_len;
436 * Calculate the number of blocks of data to be decrypted provided now, and
439 num_blocks = len / 16;
440 all_num_blocks = num_blocks + ctx->sess.blocks_processed;
442 if (num_blocks && all_num_blocks == (size_t)all_num_blocks
443 && ctx->stream != NULL) {
444 size_t max_idx = 0, top = (size_t)all_num_blocks;
447 * See how many L_{i} entries we need to process data at hand
448 * and pre-compute missing entries in the table [if any]...
452 if (ocb_lookup_l(ctx, max_idx) == NULL)
455 ctx->stream(in, out, num_blocks, ctx->keydec,
456 (size_t)ctx->sess.blocks_processed + 1, ctx->sess.offset.c,
457 (const unsigned char (*)[16])ctx->l, ctx->sess.checksum.c);
461 /* Loop through all full blocks to be decrypted */
462 for (i = ctx->sess.blocks_processed + 1; i <= all_num_blocks; i++) {
464 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
465 OCB_BLOCK *lookup = ocb_lookup_l(ctx, ocb_ntz(i));
468 ocb_block16_xor(&ctx->sess.offset, lookup, &ctx->sess.offset);
470 memcpy(tmp.c, in, 16);
473 /* P_i = Offset_i xor DECIPHER(K, C_i xor Offset_i) */
474 ocb_block16_xor(&ctx->sess.offset, &tmp, &tmp);
475 ctx->decrypt(tmp.c, tmp.c, ctx->keydec);
476 ocb_block16_xor(&ctx->sess.offset, &tmp, &tmp);
478 /* Checksum_i = Checksum_{i-1} xor P_i */
479 ocb_block16_xor(&tmp, &ctx->sess.checksum, &ctx->sess.checksum);
481 memcpy(out, tmp.c, 16);
487 * Check if we have any partial blocks left over. This is only valid in the
488 * last call to this function
495 /* Offset_* = Offset_m xor L_* */
496 ocb_block16_xor(&ctx->sess.offset, &ctx->l_star, &ctx->sess.offset);
498 /* Pad = ENCIPHER(K, Offset_*) */
499 ctx->encrypt(ctx->sess.offset.c, pad.c, ctx->keyenc);
501 /* P_* = C_* xor Pad[1..bitlen(C_*)] */
502 ocb_block_xor(in, pad.c, last_len, out);
504 /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
505 memset(pad.c, 0, 16); /* borrow pad */
506 memcpy(pad.c, out, last_len);
507 pad.c[last_len] = 0x80;
508 ocb_block16_xor(&pad, &ctx->sess.checksum, &ctx->sess.checksum);
511 ctx->sess.blocks_processed = all_num_blocks;
516 static int ocb_finish(OCB128_CONTEXT *ctx, unsigned char *tag, size_t len,
521 if (len > 16 || len < 1) {
526 * Tag = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) xor HASH(K,A)
528 ocb_block16_xor(&ctx->sess.checksum, &ctx->sess.offset, &tmp);
529 ocb_block16_xor(&ctx->l_dollar, &tmp, &tmp);
530 ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
531 ocb_block16_xor(&tmp, &ctx->sess.sum, &tmp);
534 memcpy(tag, &tmp, len);
537 return CRYPTO_memcmp(&tmp, tag, len);
542 * Calculate the tag and verify it against the supplied tag
544 int CRYPTO_ocb128_finish(OCB128_CONTEXT *ctx, const unsigned char *tag,
547 return ocb_finish(ctx, (unsigned char*)tag, len, 0);
551 * Retrieve the calculated tag
553 int CRYPTO_ocb128_tag(OCB128_CONTEXT *ctx, unsigned char *tag, size_t len)
555 return ocb_finish(ctx, tag, len, 1);
559 * Release all resources
561 void CRYPTO_ocb128_cleanup(OCB128_CONTEXT *ctx)
564 OPENSSL_clear_free(ctx->l, ctx->max_l_index * 16);
565 OPENSSL_cleanse(ctx, sizeof(*ctx));
569 #endif /* OPENSSL_NO_OCB */