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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17 * software must display the following acknowledgment:
18 * "This product includes software developed by the OpenSSL Project
19 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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32 * "This product includes software developed by the OpenSSL Project
33 * 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) {
151 * Each additional entry allows to process almost double as
152 * much data, so that in linear world the table will need to
153 * be expanded with smaller and smaller increments. Originally
154 * it was doubling in size, which was a waste. Growing it
155 * linearly is not formally optimal, but is simpler to implement.
156 * We grow table by minimally required 4*n that would accommodate
159 ctx->max_l_index += (idx - ctx->max_l_index + 4) & ~3;
161 OPENSSL_realloc(ctx->l, ctx->max_l_index * sizeof(OCB_BLOCK));
165 while (l_index <= idx) {
166 ocb_double(ctx->l + l_index, ctx->l + l_index + 1);
169 ctx->l_index = l_index;
175 * Encrypt a block from |in| and store the result in |out|
177 static void ocb_encrypt(OCB128_CONTEXT *ctx, OCB_BLOCK *in, OCB_BLOCK *out,
180 ctx->encrypt(in->c, out->c, keyenc);
184 * Decrypt a block from |in| and store the result in |out|
186 static void ocb_decrypt(OCB128_CONTEXT *ctx, OCB_BLOCK *in, OCB_BLOCK *out,
189 ctx->decrypt(in->c, out->c, keydec);
193 * Create a new OCB128_CONTEXT
195 OCB128_CONTEXT *CRYPTO_ocb128_new(void *keyenc, void *keydec,
196 block128_f encrypt, block128_f decrypt)
198 OCB128_CONTEXT *octx;
201 if ((octx = OPENSSL_malloc(sizeof(*octx))) != NULL) {
202 ret = CRYPTO_ocb128_init(octx, keyenc, keydec, encrypt, decrypt);
212 * Initialise an existing OCB128_CONTEXT
214 int CRYPTO_ocb128_init(OCB128_CONTEXT *ctx, void *keyenc, void *keydec,
215 block128_f encrypt, block128_f decrypt)
217 memset(ctx, 0, sizeof(*ctx));
219 ctx->max_l_index = 5;
220 ctx->l = OPENSSL_malloc(ctx->max_l_index * 16);
225 * We set both the encryption and decryption key schedules - decryption
226 * needs both. Don't really need decryption schedule if only doing
227 * encryption - but it simplifies things to take it anyway
229 ctx->encrypt = encrypt;
230 ctx->decrypt = decrypt;
231 ctx->keyenc = keyenc;
232 ctx->keydec = keydec;
234 /* L_* = ENCIPHER(K, zeros(128)) */
235 ocb_encrypt(ctx, &ctx->l_star, &ctx->l_star, ctx->keyenc);
237 /* L_$ = double(L_*) */
238 ocb_double(&ctx->l_star, &ctx->l_dollar);
240 /* L_0 = double(L_$) */
241 ocb_double(&ctx->l_dollar, ctx->l);
243 /* L_{i} = double(L_{i-1}) */
244 ocb_double(ctx->l, ctx->l+1);
245 ocb_double(ctx->l+1, ctx->l+2);
246 ocb_double(ctx->l+2, ctx->l+3);
247 ocb_double(ctx->l+3, ctx->l+4);
248 ctx->l_index = 4; /* enough to process up to 496 bytes */
254 * Copy an OCB128_CONTEXT object
256 int CRYPTO_ocb128_copy_ctx(OCB128_CONTEXT *dest, OCB128_CONTEXT *src,
257 void *keyenc, void *keydec)
259 memcpy(dest, src, sizeof(OCB128_CONTEXT));
261 dest->keyenc = keyenc;
263 dest->keydec = keydec;
265 dest->l = OPENSSL_malloc(src->max_l_index * 16);
268 memcpy(dest->l, src->l, (src->l_index + 1) * 16);
274 * Set the IV to be used for this operation. Must be 1 - 15 bytes.
276 int CRYPTO_ocb128_setiv(OCB128_CONTEXT *ctx, const unsigned char *iv,
277 size_t len, size_t taglen)
279 unsigned char ktop[16], tmp[16], mask;
280 unsigned char stretch[24], nonce[16];
281 size_t bottom, shift;
284 * Spec says IV is 120 bits or fewer - it allows non byte aligned lengths.
285 * We don't support this at this stage
287 if ((len > 15) || (len < 1) || (taglen > 16) || (taglen < 1)) {
291 /* Nonce = num2str(TAGLEN mod 128,7) || zeros(120-bitlen(N)) || 1 || N */
292 nonce[0] = ((taglen * 8) % 128) << 1;
293 memset(nonce + 1, 0, 15);
294 memcpy(nonce + 16 - len, iv, len);
295 nonce[15 - len] |= 1;
297 /* Ktop = ENCIPHER(K, Nonce[1..122] || zeros(6)) */
298 memcpy(tmp, nonce, 16);
300 ctx->encrypt(tmp, ktop, ctx->keyenc);
302 /* Stretch = Ktop || (Ktop[1..64] xor Ktop[9..72]) */
303 memcpy(stretch, ktop, 16);
304 ocb_block_xor(ktop, ktop + 1, 8, stretch + 16);
306 /* bottom = str2num(Nonce[123..128]) */
307 bottom = nonce[15] & 0x3f;
309 /* Offset_0 = Stretch[1+bottom..128+bottom] */
311 ocb_block_lshift(stretch + (bottom / 8), shift, ctx->offset.c);
315 (*(stretch + (bottom / 8) + 16) & mask) >> (8 - shift);
321 * Provide any AAD. This can be called multiple times. Only the final time can
322 * have a partial block
324 int CRYPTO_ocb128_aad(OCB128_CONTEXT *ctx, const unsigned char *aad,
327 u64 all_num_blocks, num_blocks;
333 /* Calculate the number of blocks of AAD provided now, and so far */
334 num_blocks = len / 16;
335 all_num_blocks = num_blocks + ctx->blocks_hashed;
337 /* Loop through all full blocks of AAD */
338 for (i = ctx->blocks_hashed + 1; i <= all_num_blocks; i++) {
340 OCB_BLOCK *aad_block;
342 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
343 lookup = ocb_lookup_l(ctx, ocb_ntz(i));
346 ocb_block16_xor(&ctx->offset_aad, lookup, &ctx->offset_aad);
348 /* Sum_i = Sum_{i-1} xor ENCIPHER(K, A_i xor Offset_i) */
349 aad_block = (OCB_BLOCK *)(aad + ((i - ctx->blocks_hashed - 1) * 16));
350 ocb_block16_xor(&ctx->offset_aad, aad_block, &tmp1);
351 ocb_encrypt(ctx, &tmp1, &tmp2, ctx->keyenc);
352 ocb_block16_xor(&ctx->sum, &tmp2, &ctx->sum);
356 * Check if we have any partial blocks left over. This is only valid in the
357 * last call to this function
362 /* Offset_* = Offset_m xor L_* */
363 ocb_block16_xor(&ctx->offset_aad, &ctx->l_star, &ctx->offset_aad);
365 /* CipherInput = (A_* || 1 || zeros(127-bitlen(A_*))) xor Offset_* */
366 memset(&tmp1, 0, 16);
367 memcpy(&tmp1, aad + (num_blocks * 16), last_len);
368 ((unsigned char *)&tmp1)[last_len] = 0x80;
369 ocb_block16_xor(&ctx->offset_aad, &tmp1, &tmp2);
371 /* Sum = Sum_m xor ENCIPHER(K, CipherInput) */
372 ocb_encrypt(ctx, &tmp2, &tmp1, ctx->keyenc);
373 ocb_block16_xor(&ctx->sum, &tmp1, &ctx->sum);
376 ctx->blocks_hashed = all_num_blocks;
382 * Provide any data to be encrypted. This can be called multiple times. Only
383 * the final time can have a partial block
385 int CRYPTO_ocb128_encrypt(OCB128_CONTEXT *ctx,
386 const unsigned char *in, unsigned char *out,
390 u64 all_num_blocks, num_blocks;
397 * Calculate the number of blocks of data to be encrypted provided now, and
400 num_blocks = len / 16;
401 all_num_blocks = num_blocks + ctx->blocks_processed;
403 /* Loop through all full blocks to be encrypted */
404 for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
409 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
410 lookup = ocb_lookup_l(ctx, ocb_ntz(i));
413 ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);
415 /* C_i = Offset_i xor ENCIPHER(K, P_i xor Offset_i) */
416 inblock = (OCB_BLOCK *)(in + ((i - ctx->blocks_processed - 1) * 16));
417 ocb_block16_xor_misaligned(&ctx->offset, inblock, &tmp1);
418 /* Checksum_i = Checksum_{i-1} xor P_i */
419 ocb_block16_xor_misaligned(&ctx->checksum, inblock, &ctx->checksum);
420 ocb_encrypt(ctx, &tmp1, &tmp2, ctx->keyenc);
422 (OCB_BLOCK *)(out + ((i - ctx->blocks_processed - 1) * 16));
423 ocb_block16_xor_misaligned(&ctx->offset, &tmp2, outblock);
428 * Check if we have any partial blocks left over. This is only valid in the
429 * last call to this function
434 /* Offset_* = Offset_m xor L_* */
435 ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);
437 /* Pad = ENCIPHER(K, Offset_*) */
438 ocb_encrypt(ctx, &ctx->offset, &pad, ctx->keyenc);
440 /* C_* = P_* xor Pad[1..bitlen(P_*)] */
441 ocb_block_xor(in + (len / 16) * 16, (unsigned char *)&pad, last_len,
442 out + (num_blocks * 16));
444 /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
445 memset(&tmp1, 0, 16);
446 memcpy(&tmp1, in + (len / 16) * 16, last_len);
447 ((unsigned char *)(&tmp1))[last_len] = 0x80;
448 ocb_block16_xor(&ctx->checksum, &tmp1, &ctx->checksum);
451 ctx->blocks_processed = all_num_blocks;
457 * Provide any data to be decrypted. This can be called multiple times. Only
458 * the final time can have a partial block
460 int CRYPTO_ocb128_decrypt(OCB128_CONTEXT *ctx,
461 const unsigned char *in, unsigned char *out,
465 u64 all_num_blocks, num_blocks;
471 * Calculate the number of blocks of data to be decrypted provided now, and
474 num_blocks = len / 16;
475 all_num_blocks = num_blocks + ctx->blocks_processed;
477 /* Loop through all full blocks to be decrypted */
478 for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
482 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
483 OCB_BLOCK *lookup = ocb_lookup_l(ctx, ocb_ntz(i));
486 ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);
488 /* P_i = Offset_i xor DECIPHER(K, C_i xor Offset_i) */
489 inblock = (OCB_BLOCK *)(in + ((i - ctx->blocks_processed - 1) * 16));
490 ocb_block16_xor_misaligned(&ctx->offset, inblock, &tmp1);
491 ocb_decrypt(ctx, &tmp1, &tmp2, ctx->keydec);
493 (OCB_BLOCK *)(out + ((i - ctx->blocks_processed - 1) * 16));
494 ocb_block16_xor_misaligned(&ctx->offset, &tmp2, outblock);
496 /* Checksum_i = Checksum_{i-1} xor P_i */
497 ocb_block16_xor_misaligned(&ctx->checksum, outblock, &ctx->checksum);
501 * Check if we have any partial blocks left over. This is only valid in the
502 * last call to this function
507 /* Offset_* = Offset_m xor L_* */
508 ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);
510 /* Pad = ENCIPHER(K, Offset_*) */
511 ocb_encrypt(ctx, &ctx->offset, &pad, ctx->keyenc);
513 /* P_* = C_* xor Pad[1..bitlen(C_*)] */
514 ocb_block_xor(in + (len / 16) * 16, (unsigned char *)&pad, last_len,
515 out + (num_blocks * 16));
517 /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
518 memset(&tmp1, 0, 16);
519 memcpy(&tmp1, out + (len / 16) * 16, last_len);
520 ((unsigned char *)(&tmp1))[last_len] = 0x80;
521 ocb_block16_xor(&ctx->checksum, &tmp1, &ctx->checksum);
524 ctx->blocks_processed = all_num_blocks;
530 * Calculate the tag and verify it against the supplied tag
532 int CRYPTO_ocb128_finish(OCB128_CONTEXT *ctx, const unsigned char *tag,
535 OCB_BLOCK tmp1, tmp2;
538 * Tag = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) xor HASH(K,A)
540 ocb_block16_xor(&ctx->checksum, &ctx->offset, &tmp1);
541 ocb_block16_xor(&tmp1, &ctx->l_dollar, &tmp2);
542 ocb_encrypt(ctx, &tmp2, &tmp1, ctx->keyenc);
543 ocb_block16_xor(&tmp1, &ctx->sum, &ctx->tag);
545 if (len > 16 || len < 1) {
549 /* Compare the tag if we've been given one */
551 return CRYPTO_memcmp(&ctx->tag, tag, len);
557 * Retrieve the calculated tag
559 int CRYPTO_ocb128_tag(OCB128_CONTEXT *ctx, unsigned char *tag, size_t len)
561 if (len > 16 || len < 1) {
565 /* Calculate the tag */
566 CRYPTO_ocb128_finish(ctx, NULL, 0);
568 /* Copy the tag into the supplied buffer */
569 memcpy(tag, &ctx->tag, len);
575 * Release all resources
577 void CRYPTO_ocb128_cleanup(OCB128_CONTEXT *ctx)
580 OPENSSL_clear_free(ctx->l, ctx->max_l_index * 16);
581 OPENSSL_cleanse(ctx, sizeof(*ctx));
585 #endif /* OPENSSL_NO_OCB */