Botan 2.13.0 Crypto and TLS for C++11

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ocb.cpp
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1 /*
2 * OCB Mode
3 * (C) 2013,2017 Jack Lloyd
4 * (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity
5 *
6 * Botan is released under the Simplified BSD License (see license.txt)
7 */
8
9 #include <botan/ocb.h>
10 #include <botan/block_cipher.h>
11 #include <botan/internal/poly_dbl.h>
12 #include <botan/internal/bit_ops.h>
13
14 namespace Botan {
15
16 // Has to be in Botan namespace so unique_ptr can reference it
17 class L_computer final
18 {
19 public:
20 explicit L_computer(const BlockCipher& cipher) :
21 m_BS(cipher.block_size()),
22 m_max_blocks(cipher.parallel_bytes() / m_BS)
23 {
24 m_L_star.resize(m_BS);
25 cipher.encrypt(m_L_star);
26 m_L_dollar = poly_double(star());
27 m_L.push_back(poly_double(dollar()));
28
29 while(m_L.size() < 8)
30 m_L.push_back(poly_double(m_L.back()));
31
32 m_offset_buf.resize(m_BS * m_max_blocks);
33 }
34
35 void init(const secure_vector<uint8_t>& offset)
36 {
37 m_offset = offset;
38 }
39
40 bool initialized() const { return m_offset.empty() == false; }
41
42 const secure_vector<uint8_t>& star() const { return m_L_star; }
43 const secure_vector<uint8_t>& dollar() const { return m_L_dollar; }
44 const secure_vector<uint8_t>& offset() const { return m_offset; }
45
46 const secure_vector<uint8_t>& get(size_t i) const
47 {
48 while(m_L.size() <= i)
49 m_L.push_back(poly_double(m_L.back()));
50
51 return m_L[i];
52 }
53
54 const uint8_t*
55 compute_offsets(size_t block_index, size_t blocks)
56 {
57 BOTAN_ASSERT(blocks <= m_max_blocks, "OCB offsets");
58
59 uint8_t* offsets = m_offset_buf.data();
60
61 if(block_index % 4 == 0)
62 {
63 const secure_vector<uint8_t>& L0 = get(0);
64 const secure_vector<uint8_t>& L1 = get(1);
65
66 while(blocks >= 4)
67 {
68 // ntz(4*i+1) == 0
69 // ntz(4*i+2) == 1
70 // ntz(4*i+3) == 0
71 block_index += 4;
72 const size_t ntz4 = var_ctz32(static_cast<uint32_t>(block_index));
73
74 xor_buf(offsets, m_offset.data(), L0.data(), m_BS);
75 offsets += m_BS;
76
77 xor_buf(offsets, offsets - m_BS, L1.data(), m_BS);
78 offsets += m_BS;
79
80 xor_buf(m_offset.data(), L1.data(), m_BS);
81 copy_mem(offsets, m_offset.data(), m_BS);
82 offsets += m_BS;
83
84 xor_buf(m_offset.data(), get(ntz4).data(), m_BS);
85 copy_mem(offsets, m_offset.data(), m_BS);
86 offsets += m_BS;
87
88 blocks -= 4;
89 }
90 }
91
92 for(size_t i = 0; i != blocks; ++i)
93 { // could be done in parallel
94 const size_t ntz = var_ctz32(static_cast<uint32_t>(block_index + i + 1));
95 xor_buf(m_offset.data(), get(ntz).data(), m_BS);
96 copy_mem(offsets, m_offset.data(), m_BS);
97 offsets += m_BS;
98 }
99
100 return m_offset_buf.data();
101 }
102
103 private:
104 secure_vector<uint8_t> poly_double(const secure_vector<uint8_t>& in) const
105 {
106 secure_vector<uint8_t> out(in.size());
107 poly_double_n(out.data(), in.data(), out.size());
108 return out;
109 }
110
111 const size_t m_BS, m_max_blocks;
112 secure_vector<uint8_t> m_L_dollar, m_L_star;
113 secure_vector<uint8_t> m_offset;
114 mutable std::vector<secure_vector<uint8_t>> m_L;
115 secure_vector<uint8_t> m_offset_buf;
116 };
117
118 namespace {
119
120 /*
121 * OCB's HASH
122 */
123 secure_vector<uint8_t> ocb_hash(const L_computer& L,
124 const BlockCipher& cipher,
125 const uint8_t ad[], size_t ad_len)
126 {
127 const size_t BS = cipher.block_size();
128 secure_vector<uint8_t> sum(BS);
129 secure_vector<uint8_t> offset(BS);
130
131 secure_vector<uint8_t> buf(BS);
132
133 const size_t ad_blocks = (ad_len / BS);
134 const size_t ad_remainder = (ad_len % BS);
135
136 for(size_t i = 0; i != ad_blocks; ++i)
137 {
138 // this loop could run in parallel
139 offset ^= L.get(var_ctz32(static_cast<uint32_t>(i+1)));
140 buf = offset;
141 xor_buf(buf.data(), &ad[BS*i], BS);
142 cipher.encrypt(buf);
143 sum ^= buf;
144 }
145
146 if(ad_remainder)
147 {
148 offset ^= L.star();
149 buf = offset;
150 xor_buf(buf.data(), &ad[BS*ad_blocks], ad_remainder);
151 buf[ad_remainder] ^= 0x80;
152 cipher.encrypt(buf);
153 sum ^= buf;
154 }
155
156 return sum;
157 }
158
159 }
160
161 OCB_Mode::OCB_Mode(BlockCipher* cipher, size_t tag_size) :
162 m_cipher(cipher),
163 m_checksum(m_cipher->parallel_bytes()),
164 m_ad_hash(m_cipher->block_size()),
165 m_tag_size(tag_size),
166 m_block_size(m_cipher->block_size()),
167 m_par_blocks(m_cipher->parallel_bytes() / m_block_size)
168 {
169 const size_t BS = block_size();
170
171 /*
172 * draft-krovetz-ocb-wide-d1 specifies OCB for several other block
173 * sizes but only 128, 192, 256 and 512 bit are currently supported
174 * by this implementation.
175 */
176 BOTAN_ARG_CHECK(BS == 16 || BS == 24 || BS == 32 || BS == 64,
177 "Invalid block size for OCB");
178
179 BOTAN_ARG_CHECK(m_tag_size % 4 == 0 &&
180 m_tag_size >= 8 && m_tag_size <= BS &&
181 m_tag_size <= 32,
182 "Invalid OCB tag length");
183 }
184
185 OCB_Mode::~OCB_Mode() { /* for unique_ptr destructor */ }
186
187 void OCB_Mode::clear()
188 {
189 m_cipher->clear();
190 m_L.reset(); // add clear here?
191 reset();
192 }
193
194 void OCB_Mode::reset()
195 {
196 m_block_index = 0;
197 zeroise(m_ad_hash);
198 zeroise(m_checksum);
199 m_last_nonce.clear();
200 m_stretch.clear();
201 }
202
203 bool OCB_Mode::valid_nonce_length(size_t length) const
204 {
205 if(length == 0)
206 return false;
207 if(block_size() == 16)
208 return length < 16;
209 else
210 return length < (block_size() - 1);
211 }
212
213 std::string OCB_Mode::name() const
214 {
215 return m_cipher->name() + "/OCB"; // include tag size?
216 }
217
218 size_t OCB_Mode::update_granularity() const
219 {
220 return (m_par_blocks * block_size());
221 }
222
223 Key_Length_Specification OCB_Mode::key_spec() const
224 {
225 return m_cipher->key_spec();
226 }
227
228 void OCB_Mode::key_schedule(const uint8_t key[], size_t length)
229 {
230 m_cipher->set_key(key, length);
231 m_L.reset(new L_computer(*m_cipher));
232 }
233
234 void OCB_Mode::set_associated_data(const uint8_t ad[], size_t ad_len)
235 {
236 verify_key_set(m_L != nullptr);
237 m_ad_hash = ocb_hash(*m_L, *m_cipher, ad, ad_len);
238 }
239
240 const secure_vector<uint8_t>&
241 OCB_Mode::update_nonce(const uint8_t nonce[], size_t nonce_len)
242 {
243 const size_t BS = block_size();
244
245 BOTAN_ASSERT(BS == 16 || BS == 24 || BS == 32 || BS == 64,
246 "OCB block size is supported");
247
248 const size_t MASKLEN = (BS == 16 ? 6 : ((BS == 24) ? 7 : 8));
249
250 const uint8_t BOTTOM_MASK =
251 static_cast<uint8_t>((static_cast<uint16_t>(1) << MASKLEN) - 1);
252
253 m_nonce_buf.resize(BS);
254 clear_mem(&m_nonce_buf[0], m_nonce_buf.size());
255
256 copy_mem(&m_nonce_buf[BS - nonce_len], nonce, nonce_len);
257 m_nonce_buf[0] = static_cast<uint8_t>(((tag_size()*8) % (BS*8)) << (BS <= 16 ? 1 : 0));
258
259 m_nonce_buf[BS - nonce_len - 1] ^= 1;
260
261 const uint8_t bottom = m_nonce_buf[BS-1] & BOTTOM_MASK;
262 m_nonce_buf[BS-1] &= ~BOTTOM_MASK;
263
264 const bool need_new_stretch = (m_last_nonce != m_nonce_buf);
265
266 if(need_new_stretch)
267 {
268 m_last_nonce = m_nonce_buf;
269
270 m_cipher->encrypt(m_nonce_buf);
271
272 /*
273 The loop bounds (BS vs BS/2) are derived from the relation
274 between the block size and the MASKLEN. Using the terminology
275 of draft-krovetz-ocb-wide, we have to derive enough bits in
276 ShiftedKtop to read up to BLOCKLEN+bottom bits from Stretch.
277
278 +----------+---------+-------+---------+
279 | BLOCKLEN | RESIDUE | SHIFT | MASKLEN |
280 +----------+---------+-------+---------+
281 | 32 | 141 | 17 | 4 |
282 | 64 | 27 | 25 | 5 |
283 | 96 | 1601 | 33 | 6 |
284 | 128 | 135 | 8 | 6 |
285 | 192 | 135 | 40 | 7 |
286 | 256 | 1061 | 1 | 8 |
287 | 384 | 4109 | 80 | 8 |
288 | 512 | 293 | 176 | 8 |
289 | 1024 | 524355 | 352 | 9 |
290 +----------+---------+-------+---------+
291 */
292 if(BS == 16)
293 {
294 for(size_t i = 0; i != BS / 2; ++i)
295 m_nonce_buf.push_back(m_nonce_buf[i] ^ m_nonce_buf[i+1]);
296 }
297 else if(BS == 24)
298 {
299 for(size_t i = 0; i != 16; ++i)
300 m_nonce_buf.push_back(m_nonce_buf[i] ^ m_nonce_buf[i+5]);
301 }
302 else if(BS == 32)
303 {
304 for(size_t i = 0; i != BS; ++i)
305 m_nonce_buf.push_back(m_nonce_buf[i] ^ (m_nonce_buf[i] << 1) ^ (m_nonce_buf[i+1] >> 7));
306 }
307 else if(BS == 64)
308 {
309 for(size_t i = 0; i != BS / 2; ++i)
310 m_nonce_buf.push_back(m_nonce_buf[i] ^ m_nonce_buf[i+22]);
311 }
312
313 m_stretch = m_nonce_buf;
314 }
315
316 // now set the offset from stretch and bottom
317 const size_t shift_bytes = bottom / 8;
318 const size_t shift_bits = bottom % 8;
319
320 BOTAN_ASSERT(m_stretch.size() >= BS + shift_bytes + 1, "Size ok");
321
322 m_offset.resize(BS);
323 for(size_t i = 0; i != BS; ++i)
324 {
325 m_offset[i] = (m_stretch[i+shift_bytes] << shift_bits);
326 m_offset[i] |= (m_stretch[i+shift_bytes+1] >> (8-shift_bits));
327 }
328
329 return m_offset;
330 }
331
332 void OCB_Mode::start_msg(const uint8_t nonce[], size_t nonce_len)
333 {
334 if(!valid_nonce_length(nonce_len))
335 throw Invalid_IV_Length(name(), nonce_len);
336
337 verify_key_set(m_L != nullptr);
338
339 m_L->init(update_nonce(nonce, nonce_len));
340 zeroise(m_checksum);
341 m_block_index = 0;
342 }
343
344 void OCB_Encryption::encrypt(uint8_t buffer[], size_t blocks)
345 {
346 verify_key_set(m_L != nullptr);
347 BOTAN_STATE_CHECK(m_L->initialized());
348
349 const size_t BS = block_size();
350
351 while(blocks)
352 {
353 const size_t proc_blocks = std::min(blocks, par_blocks());
354 const size_t proc_bytes = proc_blocks * BS;
355
356 const uint8_t* offsets = m_L->compute_offsets(m_block_index, proc_blocks);
357
358 xor_buf(m_checksum.data(), buffer, proc_bytes);
359
360 m_cipher->encrypt_n_xex(buffer, offsets, proc_blocks);
361
362 buffer += proc_bytes;
363 blocks -= proc_blocks;
364 m_block_index += proc_blocks;
365 }
366 }
367
368 size_t OCB_Encryption::process(uint8_t buf[], size_t sz)
369 {
370 BOTAN_ASSERT(sz % update_granularity() == 0, "Invalid OCB input size");
371 encrypt(buf, sz / block_size());
372 return sz;
373 }
374
375 void OCB_Encryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
376 {
377 verify_key_set(m_L != nullptr);
378
379 const size_t BS = block_size();
380
381 BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
382 const size_t sz = buffer.size() - offset;
383 uint8_t* buf = buffer.data() + offset;
384
385 secure_vector<uint8_t> mac(BS);
386
387 if(sz)
388 {
389 const size_t final_full_blocks = sz / BS;
390 const size_t remainder_bytes = sz - (final_full_blocks * BS);
391
392 encrypt(buf, final_full_blocks);
393 mac = m_L->offset();
394
395 if(remainder_bytes)
396 {
397 BOTAN_ASSERT(remainder_bytes < BS, "Only a partial block left");
398 uint8_t* remainder = &buf[sz - remainder_bytes];
399
400 xor_buf(m_checksum.data(), remainder, remainder_bytes);
401 m_checksum[remainder_bytes] ^= 0x80;
402
403 // Offset_*
404 mac ^= m_L->star();
405
406 secure_vector<uint8_t> pad(BS);
407 m_cipher->encrypt(mac, pad);
408 xor_buf(remainder, pad.data(), remainder_bytes);
409 }
410 }
411 else
412 {
413 mac = m_L->offset();
414 }
415
416 // now compute the tag
417
418 // fold checksum
419 for(size_t i = 0; i != m_checksum.size(); i += BS)
420 {
421 xor_buf(mac.data(), m_checksum.data() + i, BS);
422 }
423
424 xor_buf(mac.data(), m_L->dollar().data(), BS);
425 m_cipher->encrypt(mac);
426 xor_buf(mac.data(), m_ad_hash.data(), BS);
427
428 buffer += std::make_pair(mac.data(), tag_size());
429
430 zeroise(m_checksum);
431 m_block_index = 0;
432 }
433
434 void OCB_Decryption::decrypt(uint8_t buffer[], size_t blocks)
435 {
436 verify_key_set(m_L != nullptr);
437 BOTAN_STATE_CHECK(m_L->initialized());
438
439 const size_t BS = block_size();
440
441 while(blocks)
442 {
443 const size_t proc_blocks = std::min(blocks, par_blocks());
444 const size_t proc_bytes = proc_blocks * BS;
445
446 const uint8_t* offsets = m_L->compute_offsets(m_block_index, proc_blocks);
447
448 m_cipher->decrypt_n_xex(buffer, offsets, proc_blocks);
449
450 xor_buf(m_checksum.data(), buffer, proc_bytes);
451
452 buffer += proc_bytes;
453 blocks -= proc_blocks;
454 m_block_index += proc_blocks;
455 }
456 }
457
458 size_t OCB_Decryption::process(uint8_t buf[], size_t sz)
459 {
460 BOTAN_ASSERT(sz % update_granularity() == 0, "Invalid OCB input size");
461 decrypt(buf, sz / block_size());
462 return sz;
463 }
464
465 void OCB_Decryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
466 {
467 verify_key_set(m_L != nullptr);
468
469 const size_t BS = block_size();
470
471 BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
472 const size_t sz = buffer.size() - offset;
473 uint8_t* buf = buffer.data() + offset;
474
475 BOTAN_ASSERT(sz >= tag_size(), "We have the tag");
476
477 const size_t remaining = sz - tag_size();
478
479 secure_vector<uint8_t> mac(BS);
480
481 if(remaining)
482 {
483 const size_t final_full_blocks = remaining / BS;
484 const size_t final_bytes = remaining - (final_full_blocks * BS);
485
486 decrypt(buf, final_full_blocks);
487 mac ^= m_L->offset();
488
489 if(final_bytes)
490 {
491 BOTAN_ASSERT(final_bytes < BS, "Only a partial block left");
492
493 uint8_t* remainder = &buf[remaining - final_bytes];
494
495 mac ^= m_L->star();
496 secure_vector<uint8_t> pad(BS);
497 m_cipher->encrypt(mac, pad); // P_*
498 xor_buf(remainder, pad.data(), final_bytes);
499
500 xor_buf(m_checksum.data(), remainder, final_bytes);
501 m_checksum[final_bytes] ^= 0x80;
502 }
503 }
504 else
505 mac = m_L->offset();
506
507 // compute the mac
508
509 // fold checksum
510 for(size_t i = 0; i != m_checksum.size(); i += BS)
511 {
512 xor_buf(mac.data(), m_checksum.data() + i, BS);
513 }
514
515 mac ^= m_L->dollar();
516 m_cipher->encrypt(mac);
517 mac ^= m_ad_hash;
518
519 // reset state
520 zeroise(m_checksum);
521 m_block_index = 0;
522
523 // compare mac
524 const uint8_t* included_tag = &buf[remaining];
525
526 if(!constant_time_compare(mac.data(), included_tag, tag_size()))
527 throw Invalid_Authentication_Tag("OCB tag check failed");
528
529 // remove tag from end of message
530 buffer.resize(remaining + offset);
531 }
532
533 }
Botan::OCB_Mode::m_cipher
std::unique_ptr< BlockCipher > m_cipher
Definition: ocb.h:65
Botan::OCB_Encryption::finish
void finish(secure_vector< uint8_t > &final_block, size_t offset=0) override
Definition: ocb.cpp:375
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size_t m_offset
Definition: ber_dec.cpp:190
m_cipher
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Definition: commoncrypto_mode.cpp:50
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size_t var_ctz32(uint32_t n)
Definition: bit_ops.h:139
Botan::OCB_Mode::valid_nonce_length
bool valid_nonce_length(size_t) const override
Definition: ocb.cpp:203
Botan::OCB_Mode::set_associated_data
void set_associated_data(const uint8_t ad[], size_t ad_len) override
Definition: ocb.cpp:234
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void clear_mem(T *ptr, size_t n)
Definition: mem_ops.h:112
Botan::Key_Length_Specification
Definition: key_spec.h:18
final
int(* final)(unsigned char *, CTX *)
Definition: commoncrypto_hash.cpp:28
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void poly_double_n(uint8_t out[], const uint8_t in[], size_t n)
Definition: poly_dbl.cpp:73
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bool constant_time_compare(const uint8_t x[], const uint8_t y[], size_t len)
Definition: mem_ops.h:82
BOTAN_STATE_CHECK
#define BOTAN_STATE_CHECK(expr)
Definition: assert.h:49
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size_t tag_size() const override
Definition: ocb.h:46
Botan::OCB_Mode::reset
void reset() override
Definition: ocb.cpp:194
Botan::OCB_Mode::par_blocks
size_t par_blocks() const
Definition: ocb.h:61
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#define BOTAN_ASSERT(expr, assertion_made)
Definition: assert.h:55
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std::vector< T, secure_allocator< T >> secure_vector
Definition: secmem.h:65
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void xor_buf(uint8_t out[], const uint8_t in[], size_t length)
Definition: mem_ops.h:232
Botan::OCB_Mode::~OCB_Mode
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Definition: ocb.cpp:185
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Definition: ocb.cpp:465
Botan::OCB_Mode::update_granularity
size_t update_granularity() const override
Definition: ocb.cpp:218
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Definition: mem_ops.h:132
Botan::OCB_Mode::block_size
size_t block_size() const
Definition: ocb.h:60
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Definition: alg_id.cpp:13
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#define BOTAN_ARG_CHECK(expr, msg)
Definition: assert.h:37
Botan::OCB_Mode::m_L
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Definition: ocb.h:66
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Definition: sym_algo.h:89
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Definition: commoncrypto_hash.cpp:26
Botan::OCB_Mode::m_ad_hash
secure_vector< uint8_t > m_ad_hash
Definition: ocb.h:71
Botan::OCB_Mode::OCB_Mode
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Definition: ocb.cpp:161
Botan::OCB_Mode::m_checksum
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Definition: ocb.h:70
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Definition: ocb.cpp:368
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Definition: ocb.h:68
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Definition: ocb.cpp:187
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Definition: ocb.cpp:213
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Definition: ocb.cpp:458
Botan::OCB_Mode::key_spec
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Definition: ocb.cpp:223
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Definition: block_cipher.h:21
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Definition: secmem.h:160