Botan  2.12.1
Crypto and TLS for C++11
iso9796.cpp
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1 /*
2  * ISO-9796-2 - Digital signature schemes giving message recovery schemes 2 and 3
3  * (C) 2016 Tobias Niemann, Hackmanit GmbH
4  *
5  * Botan is released under the Simplified BSD License (see license.txt)
6  */
7 
8 #include <botan/iso9796.h>
9 #include <botan/rng.h>
10 #include <botan/exceptn.h>
11 #include <botan/mgf1.h>
12 #include <botan/hash_id.h>
13 #include <botan/internal/bit_ops.h>
14 #include <botan/internal/ct_utils.h>
15 
16 namespace Botan {
17 
18 namespace {
19 
20 secure_vector<uint8_t> iso9796_encoding(const secure_vector<uint8_t>& msg,
21  size_t output_bits,
22  std::unique_ptr<HashFunction>& hash,
23  size_t SALT_SIZE,
24  bool implicit,
25  RandomNumberGenerator& rng)
26  {
27  const size_t output_length = (output_bits + 7) / 8;
28 
29  //set trailer length
30  size_t tLength = 1;
31  if(!implicit)
32  {
33  tLength = 2;
34  }
35  const size_t HASH_SIZE = hash->output_length();
36 
37  if(output_length <= HASH_SIZE + SALT_SIZE + tLength)
38  {
39  throw Encoding_Error("ISO9796-2::encoding_of: Output length is too small");
40  }
41 
42  //calculate message capacity
43  const size_t capacity = output_length - HASH_SIZE - SALT_SIZE - tLength - 1;
44 
45  //msg1 is the recoverable and msg2 the unrecoverable message part.
46  secure_vector<uint8_t> msg1;
47  secure_vector<uint8_t> msg2;
48  if(msg.size() > capacity)
49  {
50  msg1 = secure_vector<uint8_t>(msg.begin(), msg.begin() + capacity);
51  msg2 = secure_vector<uint8_t>(msg.begin() + capacity, msg.end());
52  hash->update(msg2);
53  }
54  else
55  {
56  msg1 = msg;
57  }
58  msg2 = hash->final();
59 
60  //compute H(C||msg1 ||H(msg2)||S)
61  const size_t msgLength = msg1.size();
62  secure_vector<uint8_t> salt = rng.random_vec(SALT_SIZE);
63  hash->update_be(static_cast<uint64_t>(msgLength) * 8);
64  hash->update(msg1);
65  hash->update(msg2);
66  hash->update(salt);
67  secure_vector<uint8_t> H = hash->final();
68 
69  secure_vector<uint8_t> EM(output_length);
70 
71  //compute message offset.
72  const size_t offset = output_length - HASH_SIZE - SALT_SIZE - tLength - msgLength - 1;
73 
74  //insert message border (0x01), msg1 and salt into the output buffer
75  EM[offset] = 0x01;
76  buffer_insert(EM, offset + 1, msg1);
77  buffer_insert(EM, offset + 1 + msgLength, salt);
78 
79  //apply mask
80  mgf1_mask(*hash, H.data(), HASH_SIZE, EM.data(),
81  output_length - HASH_SIZE - tLength);
82  buffer_insert(EM, output_length - HASH_SIZE - tLength, H);
83  //set implicit/ISO trailer
84  if(!implicit)
85  {
86  uint8_t hash_id = ieee1363_hash_id(hash->name());
87  if(!hash_id)
88  {
89  throw Encoding_Error("ISO9796-2::encoding_of: no hash identifier for " + hash->name());
90  }
91  EM[output_length - 1] = 0xCC;
92  EM[output_length - 2] = hash_id;
93 
94  }
95  else
96  {
97  EM[output_length - 1] = 0xBC;
98  }
99  //clear the leftmost bit (confer bouncy castle)
100  EM[0] &= 0x7F;
101 
102  return EM;
103  }
104 
105 bool iso9796_verification(const secure_vector<uint8_t>& const_coded,
106  const secure_vector<uint8_t>& raw, size_t key_bits, std::unique_ptr<HashFunction>& hash, size_t SALT_SIZE)
107  {
108  const size_t HASH_SIZE = hash->output_length();
109  const size_t KEY_BYTES = (key_bits + 7) / 8;
110 
111  if(const_coded.size() != KEY_BYTES)
112  {
113  return false;
114  }
115  //get trailer length
116  size_t tLength;
117  if(const_coded[const_coded.size() - 1] == 0xBC)
118  {
119  tLength = 1;
120  }
121  else
122  {
123  uint8_t hash_id = ieee1363_hash_id(hash->name());
124  if((!const_coded[const_coded.size() - 2]) || (const_coded[const_coded.size() - 2] != hash_id) ||
125  (const_coded[const_coded.size() - 1] != 0xCC))
126  {
127  return false; //in case of wrong ISO trailer.
128  }
129  tLength = 2;
130  }
131 
132  secure_vector<uint8_t> coded = const_coded;
133 
134  CT::poison(coded.data(), coded.size());
135  //remove mask
136  uint8_t* DB = coded.data();
137  const size_t DB_size = coded.size() - HASH_SIZE - tLength;
138 
139  const uint8_t* H = &coded[DB_size];
140 
141  mgf1_mask(*hash, H, HASH_SIZE, DB, DB_size);
142  //clear the leftmost bit (confer bouncy castle)
143  DB[0] &= 0x7F;
144 
145  //recover msg1 and salt
146  size_t msg1_offset = 1;
147 
148  auto waiting_for_delim = CT::Mask<uint8_t>::set();
149  auto bad_input = CT::Mask<uint8_t>::cleared();
150 
151  for(size_t j = 0; j < DB_size; ++j)
152  {
153  const auto is_zero = CT::Mask<uint8_t>::is_zero(DB[j]);
154  const auto is_one = CT::Mask<uint8_t>::is_equal(DB[j], 0x01);
155 
156  const auto add_m = waiting_for_delim & is_zero;
157 
158  bad_input |= waiting_for_delim & ~(is_zero | is_one);
159  msg1_offset += add_m.if_set_return(1);
160 
161  waiting_for_delim &= is_zero;
162  }
163 
164  //invalid, if delimiter 0x01 was not found or msg1_offset is too big
165  bad_input |= waiting_for_delim;
166  bad_input |= CT::Mask<size_t>::is_lt(coded.size(), tLength + HASH_SIZE + msg1_offset + SALT_SIZE);
167 
168  //in case that msg1_offset is too big, just continue with offset = 0.
169  msg1_offset = CT::Mask<size_t>::expand(bad_input.value()).if_not_set_return(msg1_offset);
170 
171  CT::unpoison(coded.data(), coded.size());
172  CT::unpoison(msg1_offset);
173 
174  secure_vector<uint8_t> msg1(coded.begin() + msg1_offset,
175  coded.end() - tLength - HASH_SIZE - SALT_SIZE);
176  secure_vector<uint8_t> salt(coded.begin() + msg1_offset + msg1.size(),
177  coded.end() - tLength - HASH_SIZE);
178 
179  //compute H2(C||msg1||H(msg2)||S*). * indicates a recovered value
180  const size_t capacity = (key_bits - 2 + 7) / 8 - HASH_SIZE - SALT_SIZE - tLength - 1;
181  secure_vector<uint8_t> msg1raw;
182  secure_vector<uint8_t> msg2;
183  if(raw.size() > capacity)
184  {
185  msg1raw = secure_vector<uint8_t> (raw.begin(), raw.begin() + capacity);
186  msg2 = secure_vector<uint8_t> (raw.begin() + capacity, raw.end());
187  hash->update(msg2);
188  }
189  else
190  {
191  msg1raw = raw;
192  }
193  msg2 = hash->final();
194 
195  const uint64_t msg1rawLength = msg1raw.size();
196  hash->update_be(msg1rawLength * 8);
197  hash->update(msg1raw);
198  hash->update(msg2);
199  hash->update(salt);
200  secure_vector<uint8_t> H3 = hash->final();
201 
202  //compute H3(C*||msg1*||H(msg2)||S*) * indicates a recovered value
203  const uint64_t msgLength = msg1.size();
204  hash->update_be(msgLength * 8);
205  hash->update(msg1);
206  hash->update(msg2);
207  hash->update(salt);
208  secure_vector<uint8_t> H2 = hash->final();
209 
210  //check if H3 == H2
211  bad_input |= CT::Mask<uint8_t>::is_zero(ct_compare_u8(H3.data(), H2.data(), HASH_SIZE));
212 
213  CT::unpoison(bad_input);
214  return (bad_input.is_set() == false);
215  }
216 
217 }
218 
220  {
221  return new ISO_9796_DS2(m_hash->clone(), m_implicit, m_SALT_SIZE);
222  }
223 
224 /*
225  * ISO-9796-2 signature scheme 2
226  * DS 2 is probabilistic
227  */
228 void ISO_9796_DS2::update(const uint8_t input[], size_t length)
229  {
230  //need to buffer message completely, before digest
231  m_msg_buffer.insert(m_msg_buffer.end(), input, input+length);
232  }
233 
234 /*
235  * Return the raw (unencoded) data
236  */
237 secure_vector<uint8_t> ISO_9796_DS2::raw_data()
238  {
239  secure_vector<uint8_t> retbuffer = m_msg_buffer;
240  m_msg_buffer.clear();
241  return retbuffer;
242  }
243 
244 /*
245  * ISO-9796-2 scheme 2 encode operation
246  */
247 secure_vector<uint8_t> ISO_9796_DS2::encoding_of(const secure_vector<uint8_t>& msg,
248  size_t output_bits,
249  RandomNumberGenerator& rng)
250  {
251  return iso9796_encoding(msg, output_bits, m_hash, m_SALT_SIZE, m_implicit, rng);
252  }
253 
254 /*
255  * ISO-9796-2 scheme 2 verify operation
256  */
257 bool ISO_9796_DS2::verify(const secure_vector<uint8_t>& const_coded,
258  const secure_vector<uint8_t>& raw, size_t key_bits)
259  {
260  return iso9796_verification(const_coded, raw, key_bits, m_hash, m_SALT_SIZE);
261  }
262 
263 /*
264  * Return the SCAN name
265  */
266 std::string ISO_9796_DS2::name() const
267  {
268  return "ISO_9796_DS2(" + m_hash->name() + ","
269  + (m_implicit ? "imp" : "exp") + "," + std::to_string(m_SALT_SIZE) + ")";
270  }
271 
273  {
274  return new ISO_9796_DS3(m_hash->clone(), m_implicit);
275  }
276 
277 /*
278  * ISO-9796-2 signature scheme 3
279  * DS 3 is deterministic and equals DS2 without salt
280  */
281 void ISO_9796_DS3::update(const uint8_t input[], size_t length)
282  {
283  //need to buffer message completely, before digest
284  m_msg_buffer.insert(m_msg_buffer.end(), input, input+length);
285  }
286 
287 /*
288  * Return the raw (unencoded) data
289  */
290 secure_vector<uint8_t> ISO_9796_DS3::raw_data()
291  {
292  secure_vector<uint8_t> retbuffer = m_msg_buffer;
293  m_msg_buffer.clear();
294  return retbuffer;
295  }
296 
297 /*
298  * ISO-9796-2 scheme 3 encode operation
299  */
300 secure_vector<uint8_t> ISO_9796_DS3::encoding_of(const secure_vector<uint8_t>& msg,
301  size_t output_bits, RandomNumberGenerator& rng)
302  {
303  return iso9796_encoding(msg, output_bits, m_hash, 0, m_implicit, rng);
304  }
305 
306 /*
307  * ISO-9796-2 scheme 3 verify operation
308  */
309 bool ISO_9796_DS3::verify(const secure_vector<uint8_t>& const_coded,
310  const secure_vector<uint8_t>& raw, size_t key_bits)
311  {
312  return iso9796_verification(const_coded, raw, key_bits, m_hash, 0);
313  }
314 /*
315  * Return the SCAN name
316  */
317 std::string ISO_9796_DS3::name() const
318  {
319  return "ISO_9796_DS3(" + m_hash->name() + "," +
320  (m_implicit ? "imp" : "exp") + ")";
321  }
322 }
static Mask< T > cleared()
Definition: ct_utils.h:115
EMSA * clone() override
Definition: iso9796.cpp:219
std::string name() const override
Definition: iso9796.cpp:317
void poison(const T *p, size_t n)
Definition: ct_utils.h:48
uint8_t ieee1363_hash_id(const std::string &name)
Definition: hash_id.cpp:146
std::string to_string(const BER_Object &obj)
Definition: asn1_obj.cpp:213
static Mask< T > expand(T v)
Definition: ct_utils.h:123
uint8_t ct_compare_u8(const uint8_t x[], const uint8_t y[], size_t len)
Definition: mem_ops.cpp:56
ISO_9796_DS3(HashFunction *hash, bool implicit=false)
Definition: iso9796.h:71
Definition: alg_id.cpp:13
std::string name() const override
Definition: iso9796.cpp:266
size_t buffer_insert(std::vector< T, Alloc > &buf, size_t buf_offset, const T input[], size_t input_length)
Definition: secmem.h:80
void unpoison(const T *p, size_t n)
Definition: ct_utils.h:59
static Mask< T > set()
Definition: ct_utils.h:107
void mgf1_mask(HashFunction &hash, const uint8_t in[], size_t in_len, uint8_t out[], size_t out_len)
Definition: mgf1.cpp:14
ISO_9796_DS2(HashFunction *hash, bool implicit=false)
Definition: iso9796.h:28
static Mask< T > is_zero(T x)
Definition: ct_utils.h:141
static Mask< T > is_equal(T x, T y)
Definition: ct_utils.h:149
MechanismType hash
static Mask< T > is_lt(T x, T y)
Definition: ct_utils.h:157
EMSA * clone() override
Definition: iso9796.cpp:272