Botan 2.1.0 Crypto and TLS for C++11

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ocb.cpp
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1 /*
2 * OCB Mode
3 * (C) 2013 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/cmac.h>
11 #include <botan/internal/bit_ops.h>
12
13 namespace Botan {
14
15 // Has to be in Botan namespace so unique_ptr can reference it
16 class L_computer
17 {
18 public:
19 explicit L_computer(const BlockCipher& cipher)
20 {
21 m_L_star.resize(cipher.block_size());
22 cipher.encrypt(m_L_star);
23 m_L_dollar = poly_double(star());
24 m_L.push_back(poly_double(dollar()));
25 }
26
27 const secure_vector<uint8_t>& star() const { return m_L_star; }
28
29 const secure_vector<uint8_t>& dollar() const { return m_L_dollar; }
30
31 const secure_vector<uint8_t>& operator()(size_t i) const { return get(i); }
32
33 const secure_vector<uint8_t>& compute_offsets(secure_vector<uint8_t>& offset,
34 size_t block_index,
35 size_t blocks) const
36 {
37 m_offset_buf.resize(blocks * 16);
38
39 for(size_t i = 0; i != blocks; ++i)
40 { // could be done in parallel
41 offset ^= get(ctz(block_index + 1 + i));
42 copy_mem(&m_offset_buf[16*i], offset.data(), 16);
43 }
44
45 return m_offset_buf;
46 }
47
48 private:
49 const secure_vector<uint8_t>& get(size_t i) const
50 {
51 while(m_L.size() <= i)
52 m_L.push_back(poly_double(m_L.back()));
53
54 return m_L.at(i);
55 }
56
57 secure_vector<uint8_t> poly_double(const secure_vector<uint8_t>& in) const
58 {
59 return CMAC::poly_double(in);
60 }
61
62 secure_vector<uint8_t> m_L_dollar, m_L_star;
63 mutable std::vector<secure_vector<uint8_t>> m_L;
64 mutable secure_vector<uint8_t> m_offset_buf;
65 };
66
67 namespace {
68
69 /*
70 * OCB's HASH
71 */
72 secure_vector<uint8_t> ocb_hash(const L_computer& L,
73 const BlockCipher& cipher,
74 const uint8_t ad[], size_t ad_len)
75 {
76 secure_vector<uint8_t> sum(16);
77 secure_vector<uint8_t> offset(16);
78
79 secure_vector<uint8_t> buf(16);
80
81 const size_t ad_blocks = (ad_len / 16);
82 const size_t ad_remainder = (ad_len % 16);
83
84 for(size_t i = 0; i != ad_blocks; ++i)
85 {
86 // this loop could run in parallel
87 offset ^= L(ctz(i+1));
88
89 buf = offset;
90 xor_buf(buf.data(), &ad[16*i], 16);
91
92 cipher.encrypt(buf);
93
94 sum ^= buf;
95 }
96
97 if(ad_remainder)
98 {
99 offset ^= L.star();
100
101 buf = offset;
102 xor_buf(buf.data(), &ad[16*ad_blocks], ad_remainder);
103 buf[ad_len % 16] ^= 0x80;
104
105 cipher.encrypt(buf);
106
107 sum ^= buf;
108 }
109
110 return sum;
111 }
112
113 }
114
115 OCB_Mode::OCB_Mode(BlockCipher* cipher, size_t tag_size) :
116 m_cipher(cipher),
117 m_checksum(m_cipher->parallel_bytes()),
118 m_offset(16),
119 m_ad_hash(16),
120 m_tag_size(tag_size)
121 {
122 if(m_cipher->block_size() != 16)
123 throw Invalid_Argument("OCB requires 128 bit cipher");
124
125 if(m_tag_size % 4 != 0 || m_tag_size < 8 || m_tag_size > 16)
126 throw Invalid_Argument("Invalid OCB tag length");
127 }
128
129 OCB_Mode::~OCB_Mode() { /* for unique_ptr destructor */ }
130
131 void OCB_Mode::clear()
132 {
133 m_cipher->clear();
134 m_L.reset(); // add clear here?
135 reset();
136 }
137
138 void OCB_Mode::reset()
139 {
140 m_block_index = 0;
141 zeroise(m_ad_hash);
142 zeroise(m_offset);
143 zeroise(m_checksum);
144 m_last_nonce.clear();
145 m_stretch.clear();
146 }
147
148 bool OCB_Mode::valid_nonce_length(size_t length) const
149 {
150 return (length > 0 && length < m_cipher->block_size());
151 }
152
153 std::string OCB_Mode::name() const
154 {
155 return m_cipher->name() + "/OCB"; // include tag size
156 }
157
158 size_t OCB_Mode::update_granularity() const
159 {
160 return m_cipher->parallel_bytes();
161 }
162
163 Key_Length_Specification OCB_Mode::key_spec() const
164 {
165 return m_cipher->key_spec();
166 }
167
168 void OCB_Mode::key_schedule(const uint8_t key[], size_t length)
169 {
170 m_cipher->set_key(key, length);
171 m_L.reset(new L_computer(*m_cipher));
172 }
173
174 void OCB_Mode::set_associated_data(const uint8_t ad[], size_t ad_len)
175 {
176 BOTAN_ASSERT(m_L, "A key was set");
177 m_ad_hash = ocb_hash(*m_L, *m_cipher, ad, ad_len);
178 }
179
180 secure_vector<uint8_t>
181 OCB_Mode::update_nonce(const uint8_t nonce[], size_t nonce_len)
182 {
183 BOTAN_ASSERT(nonce_len < 16, "OCB nonce is less than cipher block size");
184
185 secure_vector<uint8_t> nonce_buf(16);
186
187 copy_mem(&nonce_buf[16 - nonce_len], nonce, nonce_len);
188 nonce_buf[0] = ((tag_size() * 8) % 128) << 1;
189 nonce_buf[16 - nonce_len - 1] = 1;
190
191 const uint8_t bottom = nonce_buf[16-1] & 0x3F;
192 nonce_buf[16-1] &= 0xC0;
193
194 const bool need_new_stretch = (m_last_nonce != nonce_buf);
195
196 if(need_new_stretch)
197 {
198 m_last_nonce = nonce_buf;
199
200 m_cipher->encrypt(nonce_buf);
201
202 for(size_t i = 0; i != 16 / 2; ++i)
203 nonce_buf.push_back(nonce_buf[i] ^ nonce_buf[i+1]);
204
205 m_stretch = nonce_buf;
206 }
207
208 // now set the offset from stretch and bottom
209
210 const size_t shift_bytes = bottom / 8;
211 const size_t shift_bits = bottom % 8;
212
213 secure_vector<uint8_t> offset(16);
214 for(size_t i = 0; i != 16; ++i)
215 {
216 offset[i] = (m_stretch[i+shift_bytes] << shift_bits);
217 offset[i] |= (m_stretch[i+shift_bytes+1] >> (8-shift_bits));
218 }
219
220 return offset;
221 }
222
223 void OCB_Mode::start_msg(const uint8_t nonce[], size_t nonce_len)
224 {
225 if(!valid_nonce_length(nonce_len))
226 throw Invalid_IV_Length(name(), nonce_len);
227
228 BOTAN_ASSERT(m_L, "A key was set");
229
230 m_offset = update_nonce(nonce, nonce_len);
231 zeroise(m_checksum);
232 m_block_index = 0;
233 }
234
235 void OCB_Encryption::encrypt(uint8_t buffer[], size_t blocks)
236 {
237 const size_t par_blocks = m_checksum.size() / 16;
238
239 while(blocks)
240 {
241 const size_t proc_blocks = std::min(blocks, par_blocks);
242 const size_t proc_bytes = proc_blocks * 16;
243
244 const auto& offsets = m_L->compute_offsets(m_offset, m_block_index, proc_blocks);
245
246 xor_buf(m_checksum.data(), buffer, proc_bytes);
247
248 xor_buf(buffer, offsets.data(), proc_bytes);
249 m_cipher->encrypt_n(buffer, buffer, proc_blocks);
250 xor_buf(buffer, offsets.data(), proc_bytes);
251
252 buffer += proc_bytes;
253 blocks -= proc_blocks;
254 m_block_index += proc_blocks;
255 }
256 }
257
258 size_t OCB_Encryption::process(uint8_t buf[], size_t sz)
259 {
260 BOTAN_ASSERT(sz % 16 == 0, "Invalid OCB input size");
261 encrypt(buf, sz / 16);
262 return sz;
263 }
264
265 void OCB_Encryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
266 {
267 BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
268 const size_t sz = buffer.size() - offset;
269 uint8_t* buf = buffer.data() + offset;
270
271 if(sz)
272 {
273 const size_t final_full_blocks = sz / 16;
274 const size_t remainder_bytes = sz - (final_full_blocks * 16);
275
276 encrypt(buf, final_full_blocks);
277
278 if(remainder_bytes)
279 {
280 BOTAN_ASSERT(remainder_bytes < 16, "Only a partial block left");
281 uint8_t* remainder = &buf[sz - remainder_bytes];
282
283 xor_buf(m_checksum.data(), remainder, remainder_bytes);
284 m_checksum[remainder_bytes] ^= 0x80;
285
286 m_offset ^= m_L->star(); // Offset_*
287
288 secure_vector<uint8_t> zeros(16);
289 m_cipher->encrypt(m_offset, zeros);
290 xor_buf(remainder, zeros.data(), remainder_bytes);
291 }
292 }
293
294 secure_vector<uint8_t> checksum(16);
295
296 // fold checksum
297 for(size_t i = 0; i != m_checksum.size(); ++i)
298 checksum[i % checksum.size()] ^= m_checksum[i];
299
300 // now compute the tag
301 secure_vector<uint8_t> mac = m_offset;
302 mac ^= checksum;
303 mac ^= m_L->dollar();
304
305 m_cipher->encrypt(mac);
306
307 mac ^= m_ad_hash;
308
309 buffer += std::make_pair(mac.data(), tag_size());
310
311 zeroise(m_checksum);
312 zeroise(m_offset);
313 m_block_index = 0;
314 }
315
316 void OCB_Decryption::decrypt(uint8_t buffer[], size_t blocks)
317 {
318 const size_t par_bytes = m_cipher->parallel_bytes();
319
320 BOTAN_ASSERT(par_bytes % 16 == 0, "Cipher is parallel in full blocks");
321
322 const size_t par_blocks = par_bytes / 16;
323
324 while(blocks)
325 {
326 const size_t proc_blocks = std::min(blocks, par_blocks);
327 const size_t proc_bytes = proc_blocks * 16;
328
329 const auto& offsets = m_L->compute_offsets(m_offset, m_block_index, proc_blocks);
330
331 xor_buf(buffer, offsets.data(), proc_bytes);
332 m_cipher->decrypt_n(buffer, buffer, proc_blocks);
333 xor_buf(buffer, offsets.data(), proc_bytes);
334
335 xor_buf(m_checksum.data(), buffer, proc_bytes);
336
337 buffer += proc_bytes;
338 blocks -= proc_blocks;
339 m_block_index += proc_blocks;
340 }
341 }
342
343 size_t OCB_Decryption::process(uint8_t buf[], size_t sz)
344 {
345 BOTAN_ASSERT(sz % 16 == 0, "Invalid OCB input size");
346 decrypt(buf, sz / 16);
347 return sz;
348 }
349
350 void OCB_Decryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
351 {
352 BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
353 const size_t sz = buffer.size() - offset;
354 uint8_t* buf = buffer.data() + offset;
355
356 BOTAN_ASSERT(sz >= tag_size(), "We have the tag");
357
358 const size_t remaining = sz - tag_size();
359
360 if(remaining)
361 {
362 const size_t final_full_blocks = remaining / 16;
363 const size_t final_bytes = remaining - (final_full_blocks * 16);
364
365 decrypt(buf, final_full_blocks);
366
367 if(final_bytes)
368 {
369 BOTAN_ASSERT(final_bytes < 16, "Only a partial block left");
370
371 uint8_t* remainder = &buf[remaining - final_bytes];
372
373 m_offset ^= m_L->star(); // Offset_*
374
375 secure_vector<uint8_t> pad(16);
376 m_cipher->encrypt(m_offset, pad); // P_*
377
378 xor_buf(remainder, pad.data(), final_bytes);
379
380 xor_buf(m_checksum.data(), remainder, final_bytes);
381 m_checksum[final_bytes] ^= 0x80;
382 }
383 }
384
385 secure_vector<uint8_t> checksum(16);
386
387 // fold checksum
388 for(size_t i = 0; i != m_checksum.size(); ++i)
389 checksum[i % checksum.size()] ^= m_checksum[i];
390
391 // compute the mac
392 secure_vector<uint8_t> mac = m_offset;
393 mac ^= checksum;
394 mac ^= m_L->dollar();
395
396 m_cipher->encrypt(mac);
397
398 mac ^= m_ad_hash;
399
400 // reset state
401 zeroise(m_checksum);
402 zeroise(m_offset);
403 m_block_index = 0;
404
405 // compare mac
406 const uint8_t* included_tag = &buf[remaining];
407
408 if(!same_mem(mac.data(), included_tag, tag_size()))
409 throw Integrity_Failure("OCB tag check failed");
410
411 // remove tag from end of message
412 buffer.resize(remaining + offset);
413 }
414
415 }
Botan::xor_buf
void xor_buf(T out[], const T in[], size_t length)
Definition: mem_ops.h:115
Botan::OCB_Mode::m_cipher
std::unique_ptr< BlockCipher > m_cipher
Definition: ocb.h:56
Botan::ctz
size_t ctz(T n)
Definition: bit_ops.h:97
Botan::OCB_Encryption::finish
void finish(secure_vector< uint8_t > &final_block, size_t offset=0) override
Definition: ocb.cpp:265
Botan::Invalid_Argument
Definition: exceptn.h:34
Botan::same_mem
bool same_mem(const T *p1, const T *p2, size_t n)
Definition: mem_ops.h:98
Botan::OCB_Mode::valid_nonce_length
bool valid_nonce_length(size_t) const override
Definition: ocb.cpp:148
Botan::OCB_Mode::set_associated_data
void set_associated_data(const uint8_t ad[], size_t ad_len) override
Definition: ocb.cpp:174
Botan::Integrity_Failure
Definition: exceptn.h:198
Botan::Key_Length_Specification
Definition: key_spec.h:18
Botan::OCB_Mode::tag_size
size_t tag_size() const override
Definition: ocb.h:41
Botan::OCB_Mode::reset
void reset() override
Definition: ocb.cpp:138
BOTAN_ASSERT
#define BOTAN_ASSERT(expr, assertion_made)
Definition: assert.h:27
Botan::secure_vector
std::vector< T, secure_allocator< T >> secure_vector
Definition: secmem.h:121
Botan::OCB_Mode::~OCB_Mode
~OCB_Mode()
Definition: ocb.cpp:129
Botan::OCB_Decryption::finish
void finish(secure_vector< uint8_t > &final_block, size_t offset=0) override
Definition: ocb.cpp:350
Botan::OCB_Mode::update_granularity
size_t update_granularity() const override
Definition: ocb.cpp:158
Botan::copy_mem
void copy_mem(T *out, const T *in, size_t n)
Definition: mem_ops.h:68
Botan
Definition: alg_id.cpp:13
Botan::OCB_Mode::m_L
std::unique_ptr< L_computer > m_L
Definition: ocb.h:57
Botan::CMAC::poly_double
static secure_vector< uint8_t > poly_double(const secure_vector< uint8_t > &in)
Definition: cmac.cpp:15
Botan::OCB_Mode::m_ad_hash
secure_vector< uint8_t > m_ad_hash
Definition: ocb.h:63
Botan::OCB_Mode::OCB_Mode
OCB_Mode(BlockCipher *cipher, size_t tag_size)
Definition: ocb.cpp:115
Botan::CT::min
T min(T a, T b)
Definition: ct_utils.h:180
Botan::OCB_Mode::m_checksum
secure_vector< uint8_t > m_checksum
Definition: ocb.h:61
Botan::OCB_Encryption::process
size_t process(uint8_t buf[], size_t size) override
Definition: ocb.cpp:258
Botan::OCB_Mode::m_block_index
size_t m_block_index
Definition: ocb.h:59
Botan::OCB_Mode::clear
void clear() override
Definition: ocb.cpp:131
Botan::OCB_Mode::name
std::string name() const override
Definition: ocb.cpp:153
Botan::OCB_Mode::m_offset
secure_vector< uint8_t > m_offset
Definition: ocb.h:62
Botan::OCB_Decryption::process
size_t process(uint8_t buf[], size_t size) override
Definition: ocb.cpp:343
Botan::OCB_Mode::key_spec
Key_Length_Specification key_spec() const override
Definition: ocb.cpp:163
Botan::BlockCipher
Definition: block_cipher.h:19
Botan::zeroise
void zeroise(std::vector< T, Alloc > &vec)
Definition: secmem.h:211