1 /* ====================================================================
2 * Copyright (c) 2014 The OpenSSL Project. All rights reserved.
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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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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
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47 * ====================================================================
51 #include <openssl/crypto.h>
52 #include "modes_lcl.h"
54 #ifndef OPENSSL_NO_OCB
57 unsigned char *chrblk;
62 * Calculate the number of binary trailing zero's in any given number
64 static u32 ocb_ntz(u64 n)
69 * We do a right-to-left simple sequential search. This is surprisingly
70 * efficient as the distribution of trailing zeros is not uniform,
71 * e.g. the number of possible inputs with no trailing zeros is equal to
72 * the number with 1 or more; the number with exactly 1 is equal to the
73 * number with 2 or more, etc. Checking the last two bits covers 75% of
74 * all numbers. Checking the last three covers 87.5%
84 * Shift a block of 16 bytes left by shift bits
86 static void ocb_block_lshift(OCB_BLOCK *in, size_t shift, OCB_BLOCK *out)
88 unsigned char shift_mask;
90 unsigned char mask[15];
98 shift_mask <<= (8 - shift);
99 for (i = 15; i >= 0; i--) {
101 mask[i - 1] = locin.chrblk[i] & shift_mask;
102 mask[i - 1] >>= 8 - shift;
104 locout.chrblk[i] = locin.chrblk[i] << shift;
107 locout.chrblk[i] ^= mask[i];
113 * Perform a "double" operation as per OCB spec
115 static void ocb_double(OCB_BLOCK *in, OCB_BLOCK *out)
125 * Calculate the mask based on the most significant bit. There are more
126 * efficient ways to do this - but this way is constant time
128 mask = locin.chrblk[0] & 0x80;
132 ocb_block_lshift(in, 1, out);
134 locout.chrblk[15] ^= mask;
138 * Perform an xor on in1 and in2 - each of len bytes. Store result in out
140 static void ocb_block_xor(const unsigned char *in1,
141 const unsigned char *in2, size_t len,
145 for (i = 0; i < len; i++) {
146 out[i] = in1[i] ^ in2[i];
151 * Lookup L_index in our lookup table. If we haven't already got it we need to
154 static OCB_BLOCK *ocb_lookup_l(OCB128_CONTEXT *ctx, size_t idx)
156 if (idx <= ctx->l_index) {
160 /* We don't have it - so calculate it */
162 if (ctx->l_index == ctx->max_l_index) {
163 ctx->max_l_index *= 2;
165 OPENSSL_realloc(ctx->l, ctx->max_l_index * sizeof(OCB_BLOCK));
169 ocb_double(ctx->l + (idx - 1), ctx->l + idx);
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,
186 ctx->encrypt(locin.chrblk, locout.chrblk, keyenc);
190 * Decrypt a block from |in| and store the result in |out|
192 static void ocb_decrypt(OCB128_CONTEXT *ctx, OCB_BLOCK *in, OCB_BLOCK *out,
201 ctx->decrypt(locin.chrblk, locout.chrblk, keydec);
205 * Create a new OCB128_CONTEXT
207 OCB128_CONTEXT *CRYPTO_ocb128_new(void *keyenc, void *keydec,
208 block128_f encrypt, block128_f decrypt)
210 OCB128_CONTEXT *octx;
213 if ((octx = OPENSSL_malloc(sizeof(*octx)))) {
214 ret = CRYPTO_ocb128_init(octx, keyenc, keydec, encrypt, decrypt);
224 * Initialise an existing OCB128_CONTEXT
226 int CRYPTO_ocb128_init(OCB128_CONTEXT *ctx, void *keyenc, void *keydec,
227 block128_f encrypt, block128_f decrypt)
229 memset(ctx, 0, sizeof(*ctx));
231 ctx->max_l_index = 1;
232 ctx->l = OPENSSL_malloc(ctx->max_l_index * 16);
237 * We set both the encryption and decryption key schedules - decryption
238 * needs both. Don't really need decryption schedule if only doing
239 * encryption - but it simplifies things to take it anyway
241 ctx->encrypt = encrypt;
242 ctx->decrypt = decrypt;
243 ctx->keyenc = keyenc;
244 ctx->keydec = keydec;
246 /* L_* = ENCIPHER(K, zeros(128)) */
247 ocb_encrypt(ctx, &ctx->l_star, &ctx->l_star, ctx->keyenc);
249 /* L_$ = double(L_*) */
250 ocb_double(&ctx->l_star, &ctx->l_dollar);
252 /* L_0 = double(L_$) */
253 ocb_double(&ctx->l_dollar, ctx->l);
259 * Copy an OCB128_CONTEXT object
261 int CRYPTO_ocb128_copy_ctx(OCB128_CONTEXT *dest, OCB128_CONTEXT *src,
262 void *keyenc, void *keydec)
264 memcpy(dest, src, sizeof(OCB128_CONTEXT));
266 dest->keyenc = keyenc;
268 dest->keydec = keydec;
270 dest->l = OPENSSL_malloc(src->max_l_index * 16);
273 memcpy(dest->l, src->l, (src->l_index + 1) * 16);
279 * Set the IV to be used for this operation. Must be 1 - 15 bytes.
281 int CRYPTO_ocb128_setiv(OCB128_CONTEXT *ctx, const unsigned char *iv,
282 size_t len, size_t taglen)
284 unsigned char ktop[16], tmp[16], mask;
285 unsigned char stretch[24], nonce[16];
286 size_t bottom, shift;
289 offset.ocbblk = &ctx->offset;
292 * Spec says IV is 120 bits or fewer - it allows non byte aligned lengths.
293 * We don't support this at this stage
295 if ((len > 15) || (len < 1) || (taglen > 16) || (taglen < 1)) {
299 /* Nonce = num2str(TAGLEN mod 128,7) || zeros(120-bitlen(N)) || 1 || N */
300 nonce[0] = ((taglen * 8) % 128) << 1;
301 memset(nonce + 1, 0, 15);
302 memcpy(nonce + 16 - len, iv, len);
303 nonce[15 - len] |= 1;
305 /* Ktop = ENCIPHER(K, Nonce[1..122] || zeros(6)) */
306 memcpy(tmp, nonce, 16);
308 ctx->encrypt(tmp, ktop, ctx->keyenc);
310 /* Stretch = Ktop || (Ktop[1..64] xor Ktop[9..72]) */
311 memcpy(stretch, ktop, 16);
312 ocb_block_xor(ktop, ktop + 1, 8, stretch + 16);
314 /* bottom = str2num(Nonce[123..128]) */
315 bottom = nonce[15] & 0x3f;
317 /* Offset_0 = Stretch[1+bottom..128+bottom] */
319 ocb_block_lshift((OCB_BLOCK *)(stretch + (bottom / 8)), shift,
324 (*(stretch + (bottom / 8) + 16) & mask) >> (8 - shift);
330 * Provide any AAD. This can be called multiple times. Only the final time can
331 * have a partial block
333 int CRYPTO_ocb128_aad(OCB128_CONTEXT *ctx, const unsigned char *aad,
336 u64 all_num_blocks, num_blocks;
342 /* Calculate the number of blocks of AAD provided now, and so far */
343 num_blocks = len / 16;
344 all_num_blocks = num_blocks + ctx->blocks_hashed;
346 /* Loop through all full blocks of AAD */
347 for (i = ctx->blocks_hashed + 1; i <= all_num_blocks; i++) {
349 OCB_BLOCK *aad_block;
351 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
352 lookup = ocb_lookup_l(ctx, ocb_ntz(i));
355 ocb_block16_xor(&ctx->offset_aad, lookup, &ctx->offset_aad);
357 /* Sum_i = Sum_{i-1} xor ENCIPHER(K, A_i xor Offset_i) */
358 aad_block = (OCB_BLOCK *)(aad + ((i - ctx->blocks_hashed - 1) * 16));
359 ocb_block16_xor(&ctx->offset_aad, aad_block, &tmp1);
360 ocb_encrypt(ctx, &tmp1, &tmp2, ctx->keyenc);
361 ocb_block16_xor(&ctx->sum, &tmp2, &ctx->sum);
365 * Check if we have any partial blocks left over. This is only valid in the
366 * last call to this function
371 /* Offset_* = Offset_m xor L_* */
372 ocb_block16_xor(&ctx->offset_aad, &ctx->l_star, &ctx->offset_aad);
374 /* CipherInput = (A_* || 1 || zeros(127-bitlen(A_*))) xor Offset_* */
375 memset(&tmp1, 0, 16);
376 memcpy(&tmp1, aad + (num_blocks * 16), last_len);
377 ((unsigned char *)&tmp1)[last_len] = 0x80;
378 ocb_block16_xor(&ctx->offset_aad, &tmp1, &tmp2);
380 /* Sum = Sum_m xor ENCIPHER(K, CipherInput) */
381 ocb_encrypt(ctx, &tmp2, &tmp1, ctx->keyenc);
382 ocb_block16_xor(&ctx->sum, &tmp1, &ctx->sum);
385 ctx->blocks_hashed = all_num_blocks;
391 * Provide any data to be encrypted. This can be called multiple times. Only
392 * the final time can have a partial block
394 int CRYPTO_ocb128_encrypt(OCB128_CONTEXT *ctx,
395 const unsigned char *in, unsigned char *out,
399 u64 all_num_blocks, num_blocks;
406 * Calculate the number of blocks of data to be encrypted provided now, and
409 num_blocks = len / 16;
410 all_num_blocks = num_blocks + ctx->blocks_processed;
412 /* Loop through all full blocks to be encrypted */
413 for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
418 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
419 lookup = ocb_lookup_l(ctx, ocb_ntz(i));
422 ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);
424 /* C_i = Offset_i xor ENCIPHER(K, P_i xor Offset_i) */
425 inblock = (OCB_BLOCK *)(in + ((i - ctx->blocks_processed - 1) * 16));
426 ocb_block16_xor(&ctx->offset, inblock, &tmp1);
427 ocb_encrypt(ctx, &tmp1, &tmp2, ctx->keyenc);
429 (OCB_BLOCK *)(out + ((i - ctx->blocks_processed - 1) * 16));
430 ocb_block16_xor(&ctx->offset, &tmp2, outblock);
432 /* Checksum_i = Checksum_{i-1} xor P_i */
433 ocb_block16_xor(&ctx->checksum, inblock, &ctx->checksum);
437 * Check if we have any partial blocks left over. This is only valid in the
438 * last call to this function
443 /* Offset_* = Offset_m xor L_* */
444 ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);
446 /* Pad = ENCIPHER(K, Offset_*) */
447 ocb_encrypt(ctx, &ctx->offset, &pad, ctx->keyenc);
449 /* C_* = P_* xor Pad[1..bitlen(P_*)] */
450 ocb_block_xor(in + (len / 16) * 16, (unsigned char *)&pad, last_len,
451 out + (num_blocks * 16));
453 /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
454 memset(&tmp1, 0, 16);
455 memcpy(&tmp1, in + (len / 16) * 16, last_len);
456 ((unsigned char *)(&tmp1))[last_len] = 0x80;
457 ocb_block16_xor(&ctx->checksum, &tmp1, &ctx->checksum);
460 ctx->blocks_processed = all_num_blocks;
466 * Provide any data to be decrypted. This can be called multiple times. Only
467 * the final time can have a partial block
469 int CRYPTO_ocb128_decrypt(OCB128_CONTEXT *ctx,
470 const unsigned char *in, unsigned char *out,
474 u64 all_num_blocks, num_blocks;
480 * Calculate the number of blocks of data to be decrypted provided now, and
483 num_blocks = len / 16;
484 all_num_blocks = num_blocks + ctx->blocks_processed;
486 /* Loop through all full blocks to be decrypted */
487 for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
491 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
492 OCB_BLOCK *lookup = ocb_lookup_l(ctx, ocb_ntz(i));
495 ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);
497 /* P_i = Offset_i xor DECIPHER(K, C_i xor Offset_i) */
498 inblock = (OCB_BLOCK *)(in + ((i - ctx->blocks_processed - 1) * 16));
499 ocb_block16_xor(&ctx->offset, inblock, &tmp1);
500 ocb_decrypt(ctx, &tmp1, &tmp2, ctx->keydec);
502 (OCB_BLOCK *)(out + ((i - ctx->blocks_processed - 1) * 16));
503 ocb_block16_xor(&ctx->offset, &tmp2, outblock);
505 /* Checksum_i = Checksum_{i-1} xor P_i */
506 ocb_block16_xor(&ctx->checksum, outblock, &ctx->checksum);
510 * Check if we have any partial blocks left over. This is only valid in the
511 * last call to this function
516 /* Offset_* = Offset_m xor L_* */
517 ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);
519 /* Pad = ENCIPHER(K, Offset_*) */
520 ocb_encrypt(ctx, &ctx->offset, &pad, ctx->keyenc);
522 /* P_* = C_* xor Pad[1..bitlen(C_*)] */
523 ocb_block_xor(in + (len / 16) * 16, (unsigned char *)&pad, last_len,
524 out + (num_blocks * 16));
526 /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
527 memset(&tmp1, 0, 16);
528 memcpy(&tmp1, out + (len / 16) * 16, last_len);
529 ((unsigned char *)(&tmp1))[last_len] = 0x80;
530 ocb_block16_xor(&ctx->checksum, &tmp1, &ctx->checksum);
533 ctx->blocks_processed = all_num_blocks;
539 * Calculate the tag and verify it against the supplied tag
541 int CRYPTO_ocb128_finish(OCB128_CONTEXT *ctx, const unsigned char *tag,
544 OCB_BLOCK tmp1, tmp2;
547 * Tag = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) xor HASH(K,A)
549 ocb_block16_xor(&ctx->checksum, &ctx->offset, &tmp1);
550 ocb_block16_xor(&tmp1, &ctx->l_dollar, &tmp2);
551 ocb_encrypt(ctx, &tmp2, &tmp1, ctx->keyenc);
552 ocb_block16_xor(&tmp1, &ctx->sum, &ctx->tag);
554 if (len > 16 || len < 1) {
558 /* Compare the tag if we've been given one */
560 return CRYPTO_memcmp(&ctx->tag, tag, len);
566 * Retrieve the calculated tag
568 int CRYPTO_ocb128_tag(OCB128_CONTEXT *ctx, unsigned char *tag, size_t len)
570 if (len > 16 || len < 1) {
574 /* Calculate the tag */
575 CRYPTO_ocb128_finish(ctx, NULL, 0);
577 /* Copy the tag into the supplied buffer */
578 memcpy(tag, &ctx->tag, len);
584 * Release all resources
586 void CRYPTO_ocb128_cleanup(OCB128_CONTEXT *ctx)
589 OPENSSL_clear_free(ctx->l, ctx->max_l_index * 16);
590 OPENSSL_cleanse(ctx, sizeof(*ctx));
594 #endif /* OPENSSL_NO_OCB */