1 /* ====================================================================
2 * Copyright (c) 2014 The OpenSSL Project. All rights reserved.
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
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9 * notice, this list of conditions and the following disclaimer.
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13 * the documentation and/or other materials provided with the
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19 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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47 * ====================================================================
51 #include <openssl/crypto.h>
52 #include "modes_lcl.h"
54 #ifndef OPENSSL_NO_OCB
57 * Calculate the number of binary trailing zero's in any given number
59 static u32 ocb_ntz(u64 n)
64 * We do a right-to-left simple sequential search. This is surprisingly
65 * efficient as the distribution of trailing zeros is not uniform,
66 * e.g. the number of possible inputs with no trailing zeros is equal to
67 * the number with 1 or more; the number with exactly 1 is equal to the
68 * number with 2 or more, etc. Checking the last two bits covers 75% of
69 * all numbers. Checking the last three covers 87.5%
79 * Shift a block of 16 bytes left by shift bits
81 static void ocb_block_lshift(const unsigned char *in, size_t shift,
84 unsigned char shift_mask;
86 unsigned char mask[15];
89 shift_mask <<= (8 - shift);
90 for (i = 15; i >= 0; i--) {
92 mask[i - 1] = in[i] & shift_mask;
93 mask[i - 1] >>= 8 - shift;
95 out[i] = in[i] << shift;
104 * Perform a "double" operation as per OCB spec
106 static void ocb_double(OCB_BLOCK *in, OCB_BLOCK *out)
111 * Calculate the mask based on the most significant bit. There are more
112 * efficient ways to do this - but this way is constant time
114 mask = in->c[0] & 0x80;
118 ocb_block_lshift(in->c, 1, out->c);
124 * Perform an xor on in1 and in2 - each of len bytes. Store result in out
126 static void ocb_block_xor(const unsigned char *in1,
127 const unsigned char *in2, size_t len,
131 for (i = 0; i < len; i++) {
132 out[i] = in1[i] ^ in2[i];
137 * Lookup L_index in our lookup table. If we haven't already got it we need to
140 static OCB_BLOCK *ocb_lookup_l(OCB128_CONTEXT *ctx, size_t idx)
142 size_t l_index = ctx->l_index;
144 if (idx <= l_index) {
148 /* We don't have it - so calculate it */
149 if (idx >= ctx->max_l_index) {
152 * Each additional entry allows to process almost double as
153 * much data, so that in linear world the table will need to
154 * be expanded with smaller and smaller increments. Originally
155 * it was doubling in size, which was a waste. Growing it
156 * linearly is not formally optimal, but is simpler to implement.
157 * We grow table by minimally required 4*n that would accommodate
160 ctx->max_l_index += (idx - ctx->max_l_index + 4) & ~3;
162 OPENSSL_realloc(ctx->l, ctx->max_l_index * sizeof(OCB_BLOCK));
163 if (tmp_ptr == NULL) /* prevent ctx->l from being clobbered */
167 while (l_index < idx) {
168 ocb_double(ctx->l + l_index, ctx->l + l_index + 1);
171 ctx->l_index = l_index;
177 * Create a new OCB128_CONTEXT
179 OCB128_CONTEXT *CRYPTO_ocb128_new(void *keyenc, void *keydec,
180 block128_f encrypt, block128_f decrypt,
183 OCB128_CONTEXT *octx;
186 if ((octx = OPENSSL_malloc(sizeof(*octx))) != NULL) {
187 ret = CRYPTO_ocb128_init(octx, keyenc, keydec, encrypt, decrypt,
198 * Initialise an existing OCB128_CONTEXT
200 int CRYPTO_ocb128_init(OCB128_CONTEXT *ctx, void *keyenc, void *keydec,
201 block128_f encrypt, block128_f decrypt,
204 memset(ctx, 0, sizeof(*ctx));
206 ctx->max_l_index = 5;
207 ctx->l = OPENSSL_malloc(ctx->max_l_index * 16);
212 * We set both the encryption and decryption key schedules - decryption
213 * needs both. Don't really need decryption schedule if only doing
214 * encryption - but it simplifies things to take it anyway
216 ctx->encrypt = encrypt;
217 ctx->decrypt = decrypt;
218 ctx->stream = stream;
219 ctx->keyenc = keyenc;
220 ctx->keydec = keydec;
222 /* L_* = ENCIPHER(K, zeros(128)) */
223 ctx->encrypt(ctx->l_star.c, ctx->l_star.c, ctx->keyenc);
225 /* L_$ = double(L_*) */
226 ocb_double(&ctx->l_star, &ctx->l_dollar);
228 /* L_0 = double(L_$) */
229 ocb_double(&ctx->l_dollar, ctx->l);
231 /* L_{i} = double(L_{i-1}) */
232 ocb_double(ctx->l, ctx->l+1);
233 ocb_double(ctx->l+1, ctx->l+2);
234 ocb_double(ctx->l+2, ctx->l+3);
235 ocb_double(ctx->l+3, ctx->l+4);
236 ctx->l_index = 4; /* enough to process up to 496 bytes */
242 * Copy an OCB128_CONTEXT object
244 int CRYPTO_ocb128_copy_ctx(OCB128_CONTEXT *dest, OCB128_CONTEXT *src,
245 void *keyenc, void *keydec)
247 memcpy(dest, src, sizeof(OCB128_CONTEXT));
249 dest->keyenc = keyenc;
251 dest->keydec = keydec;
253 dest->l = OPENSSL_malloc(src->max_l_index * 16);
256 memcpy(dest->l, src->l, (src->l_index + 1) * 16);
262 * Set the IV to be used for this operation. Must be 1 - 15 bytes.
264 int CRYPTO_ocb128_setiv(OCB128_CONTEXT *ctx, const unsigned char *iv,
265 size_t len, size_t taglen)
267 unsigned char ktop[16], tmp[16], mask;
268 unsigned char stretch[24], nonce[16];
269 size_t bottom, shift;
272 * Spec says IV is 120 bits or fewer - it allows non byte aligned lengths.
273 * We don't support this at this stage
275 if ((len > 15) || (len < 1) || (taglen > 16) || (taglen < 1)) {
279 /* Nonce = num2str(TAGLEN mod 128,7) || zeros(120-bitlen(N)) || 1 || N */
280 nonce[0] = ((taglen * 8) % 128) << 1;
281 memset(nonce + 1, 0, 15);
282 memcpy(nonce + 16 - len, iv, len);
283 nonce[15 - len] |= 1;
285 /* Ktop = ENCIPHER(K, Nonce[1..122] || zeros(6)) */
286 memcpy(tmp, nonce, 16);
288 ctx->encrypt(tmp, ktop, ctx->keyenc);
290 /* Stretch = Ktop || (Ktop[1..64] xor Ktop[9..72]) */
291 memcpy(stretch, ktop, 16);
292 ocb_block_xor(ktop, ktop + 1, 8, stretch + 16);
294 /* bottom = str2num(Nonce[123..128]) */
295 bottom = nonce[15] & 0x3f;
297 /* Offset_0 = Stretch[1+bottom..128+bottom] */
299 ocb_block_lshift(stretch + (bottom / 8), shift, ctx->offset.c);
303 (*(stretch + (bottom / 8) + 16) & mask) >> (8 - shift);
309 * Provide any AAD. This can be called multiple times. Only the final time can
310 * have a partial block
312 int CRYPTO_ocb128_aad(OCB128_CONTEXT *ctx, const unsigned char *aad,
315 u64 i, all_num_blocks;
316 size_t num_blocks, last_len;
320 /* Calculate the number of blocks of AAD provided now, and so far */
321 num_blocks = len / 16;
322 all_num_blocks = num_blocks + ctx->blocks_hashed;
324 /* Loop through all full blocks of AAD */
325 for (i = ctx->blocks_hashed + 1; i <= all_num_blocks; i++) {
327 OCB_BLOCK *aad_block;
329 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
330 lookup = ocb_lookup_l(ctx, ocb_ntz(i));
333 ocb_block16_xor(&ctx->offset_aad, lookup, &ctx->offset_aad);
335 /* Sum_i = Sum_{i-1} xor ENCIPHER(K, A_i xor Offset_i) */
336 aad_block = (OCB_BLOCK *)(aad + ((i - ctx->blocks_hashed - 1) * 16));
337 ocb_block16_xor(&ctx->offset_aad, aad_block, &tmp1);
338 ctx->encrypt(tmp1.c, tmp2.c, ctx->keyenc);
339 ocb_block16_xor(&ctx->sum, &tmp2, &ctx->sum);
343 * Check if we have any partial blocks left over. This is only valid in the
344 * last call to this function
349 /* Offset_* = Offset_m xor L_* */
350 ocb_block16_xor(&ctx->offset_aad, &ctx->l_star, &ctx->offset_aad);
352 /* CipherInput = (A_* || 1 || zeros(127-bitlen(A_*))) xor Offset_* */
353 memset(&tmp1, 0, 16);
354 memcpy(&tmp1, aad + (num_blocks * 16), last_len);
355 ((unsigned char *)&tmp1)[last_len] = 0x80;
356 ocb_block16_xor(&ctx->offset_aad, &tmp1, &tmp2);
358 /* Sum = Sum_m xor ENCIPHER(K, CipherInput) */
359 ctx->encrypt(tmp2.c, tmp1.c, ctx->keyenc);
360 ocb_block16_xor(&ctx->sum, &tmp1, &ctx->sum);
363 ctx->blocks_hashed = all_num_blocks;
369 * Provide any data to be encrypted. This can be called multiple times. Only
370 * the final time can have a partial block
372 int CRYPTO_ocb128_encrypt(OCB128_CONTEXT *ctx,
373 const unsigned char *in, unsigned char *out,
376 u64 i, all_num_blocks;
377 size_t num_blocks, last_len;
383 * Calculate the number of blocks of data to be encrypted provided now, and
386 num_blocks = len / 16;
387 all_num_blocks = num_blocks + ctx->blocks_processed;
389 if (num_blocks && all_num_blocks == (size_t)all_num_blocks
390 && ctx->stream != NULL) {
391 size_t max_idx = 0, top = (size_t)all_num_blocks;
394 * See how many L_{i} entries we need to process data at hand
395 * and pre-compute missing entries in the table [if any]...
399 if (ocb_lookup_l(ctx, max_idx) == NULL)
402 ctx->stream(in, out, num_blocks, ctx->keyenc,
403 (size_t)ctx->blocks_processed + 1, ctx->offset.c,
404 (const unsigned char (*)[16])ctx->l, ctx->checksum.c);
406 /* Loop through all full blocks to be encrypted */
407 for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
412 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
413 lookup = ocb_lookup_l(ctx, ocb_ntz(i));
416 ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);
418 /* C_i = Offset_i xor ENCIPHER(K, P_i xor Offset_i) */
420 (OCB_BLOCK *)(in + ((i - ctx->blocks_processed - 1) * 16));
421 ocb_block16_xor_misaligned(&ctx->offset, inblock, &tmp1);
422 /* Checksum_i = Checksum_{i-1} xor P_i */
423 ocb_block16_xor_misaligned(&ctx->checksum, inblock, &ctx->checksum);
424 ctx->encrypt(tmp1.c, tmp2.c, ctx->keyenc);
426 (OCB_BLOCK *)(out + ((i - ctx->blocks_processed - 1) * 16));
427 ocb_block16_xor_misaligned(&ctx->offset, &tmp2, outblock);
432 * Check if we have any partial blocks left over. This is only valid in the
433 * last call to this function
438 /* Offset_* = Offset_m xor L_* */
439 ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);
441 /* Pad = ENCIPHER(K, Offset_*) */
442 ctx->encrypt(ctx->offset.c, pad.c, ctx->keyenc);
444 /* C_* = P_* xor Pad[1..bitlen(P_*)] */
445 ocb_block_xor(in + (len / 16) * 16, (unsigned char *)&pad, last_len,
446 out + (num_blocks * 16));
448 /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
449 memset(&tmp1, 0, 16);
450 memcpy(&tmp1, in + (len / 16) * 16, last_len);
451 ((unsigned char *)(&tmp1))[last_len] = 0x80;
452 ocb_block16_xor(&ctx->checksum, &tmp1, &ctx->checksum);
455 ctx->blocks_processed = all_num_blocks;
461 * Provide any data to be decrypted. This can be called multiple times. Only
462 * the final time can have a partial block
464 int CRYPTO_ocb128_decrypt(OCB128_CONTEXT *ctx,
465 const unsigned char *in, unsigned char *out,
468 u64 i, all_num_blocks;
469 size_t num_blocks, last_len;
475 * Calculate the number of blocks of data to be decrypted provided now, and
478 num_blocks = len / 16;
479 all_num_blocks = num_blocks + ctx->blocks_processed;
481 if (num_blocks && all_num_blocks == (size_t)all_num_blocks
482 && ctx->stream != NULL) {
483 size_t max_idx = 0, top = (size_t)all_num_blocks;
486 * See how many L_{i} entries we need to process data at hand
487 * and pre-compute missing entries in the table [if any]...
491 if (ocb_lookup_l(ctx, max_idx) == NULL)
494 ctx->stream(in, out, num_blocks, ctx->keydec,
495 (size_t)ctx->blocks_processed + 1, ctx->offset.c,
496 (const unsigned char (*)[16])ctx->l, ctx->checksum.c);
498 /* Loop through all full blocks to be decrypted */
499 for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
503 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
504 OCB_BLOCK *lookup = ocb_lookup_l(ctx, ocb_ntz(i));
507 ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);
509 /* P_i = Offset_i xor DECIPHER(K, C_i xor Offset_i) */
511 (OCB_BLOCK *)(in + ((i - ctx->blocks_processed - 1) * 16));
512 ocb_block16_xor_misaligned(&ctx->offset, inblock, &tmp1);
513 ctx->decrypt(tmp1.c, tmp2.c, ctx->keydec);
515 (OCB_BLOCK *)(out + ((i - ctx->blocks_processed - 1) * 16));
516 ocb_block16_xor_misaligned(&ctx->offset, &tmp2, outblock);
518 /* Checksum_i = Checksum_{i-1} xor P_i */
519 ocb_block16_xor_misaligned(&ctx->checksum, outblock, &ctx->checksum);
524 * Check if we have any partial blocks left over. This is only valid in the
525 * last call to this function
530 /* Offset_* = Offset_m xor L_* */
531 ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);
533 /* Pad = ENCIPHER(K, Offset_*) */
534 ctx->encrypt(ctx->offset.c, pad.c, ctx->keyenc);
536 /* P_* = C_* xor Pad[1..bitlen(C_*)] */
537 ocb_block_xor(in + (len / 16) * 16, (unsigned char *)&pad, last_len,
538 out + (num_blocks * 16));
540 /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
541 memset(&tmp1, 0, 16);
542 memcpy(&tmp1, out + (len / 16) * 16, last_len);
543 ((unsigned char *)(&tmp1))[last_len] = 0x80;
544 ocb_block16_xor(&ctx->checksum, &tmp1, &ctx->checksum);
547 ctx->blocks_processed = all_num_blocks;
553 * Calculate the tag and verify it against the supplied tag
555 int CRYPTO_ocb128_finish(OCB128_CONTEXT *ctx, const unsigned char *tag,
558 OCB_BLOCK tmp1, tmp2;
561 * Tag = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) xor HASH(K,A)
563 ocb_block16_xor(&ctx->checksum, &ctx->offset, &tmp1);
564 ocb_block16_xor(&tmp1, &ctx->l_dollar, &tmp2);
565 ctx->encrypt(tmp2.c, tmp1.c, ctx->keyenc);
566 ocb_block16_xor(&tmp1, &ctx->sum, &ctx->tag);
568 if (len > 16 || len < 1) {
572 /* Compare the tag if we've been given one */
574 return CRYPTO_memcmp(&ctx->tag, tag, len);
580 * Retrieve the calculated tag
582 int CRYPTO_ocb128_tag(OCB128_CONTEXT *ctx, unsigned char *tag, size_t len)
584 if (len > 16 || len < 1) {
588 /* Calculate the tag */
589 CRYPTO_ocb128_finish(ctx, NULL, 0);
591 /* Copy the tag into the supplied buffer */
592 memcpy(tag, &ctx->tag, len);
598 * Release all resources
600 void CRYPTO_ocb128_cleanup(OCB128_CONTEXT *ctx)
603 OPENSSL_clear_free(ctx->l, ctx->max_l_index * 16);
604 OPENSSL_cleanse(ctx, sizeof(*ctx));
608 #endif /* OPENSSL_NO_OCB */