Botan  2.9.0
Crypto and TLS for C++11
tss.cpp
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1 /*
2 * RTSS (threshold secret sharing)
3 * (C) 2009,2018 Jack Lloyd
4 *
5 * Botan is released under the Simplified BSD License (see license.txt)
6 */
7 
8 #include <botan/tss.h>
9 #include <botan/rng.h>
10 #include <botan/hash.h>
11 #include <botan/loadstor.h>
12 #include <botan/hex.h>
13 
14 namespace Botan {
15 
16 namespace {
17 
18 const size_t RTSS_HEADER_SIZE = 20;
19 
20 /**
21 Table for GF(2^8) arithmetic (exponentials)
22 */
23 const uint8_t RTSS_EXP[256] = {
24 0x01, 0x03, 0x05, 0x0F, 0x11, 0x33, 0x55, 0xFF, 0x1A, 0x2E, 0x72,
25 0x96, 0xA1, 0xF8, 0x13, 0x35, 0x5F, 0xE1, 0x38, 0x48, 0xD8, 0x73,
26 0x95, 0xA4, 0xF7, 0x02, 0x06, 0x0A, 0x1E, 0x22, 0x66, 0xAA, 0xE5,
27 0x34, 0x5C, 0xE4, 0x37, 0x59, 0xEB, 0x26, 0x6A, 0xBE, 0xD9, 0x70,
28 0x90, 0xAB, 0xE6, 0x31, 0x53, 0xF5, 0x04, 0x0C, 0x14, 0x3C, 0x44,
29 0xCC, 0x4F, 0xD1, 0x68, 0xB8, 0xD3, 0x6E, 0xB2, 0xCD, 0x4C, 0xD4,
30 0x67, 0xA9, 0xE0, 0x3B, 0x4D, 0xD7, 0x62, 0xA6, 0xF1, 0x08, 0x18,
31 0x28, 0x78, 0x88, 0x83, 0x9E, 0xB9, 0xD0, 0x6B, 0xBD, 0xDC, 0x7F,
32 0x81, 0x98, 0xB3, 0xCE, 0x49, 0xDB, 0x76, 0x9A, 0xB5, 0xC4, 0x57,
33 0xF9, 0x10, 0x30, 0x50, 0xF0, 0x0B, 0x1D, 0x27, 0x69, 0xBB, 0xD6,
34 0x61, 0xA3, 0xFE, 0x19, 0x2B, 0x7D, 0x87, 0x92, 0xAD, 0xEC, 0x2F,
35 0x71, 0x93, 0xAE, 0xE9, 0x20, 0x60, 0xA0, 0xFB, 0x16, 0x3A, 0x4E,
36 0xD2, 0x6D, 0xB7, 0xC2, 0x5D, 0xE7, 0x32, 0x56, 0xFA, 0x15, 0x3F,
37 0x41, 0xC3, 0x5E, 0xE2, 0x3D, 0x47, 0xC9, 0x40, 0xC0, 0x5B, 0xED,
38 0x2C, 0x74, 0x9C, 0xBF, 0xDA, 0x75, 0x9F, 0xBA, 0xD5, 0x64, 0xAC,
39 0xEF, 0x2A, 0x7E, 0x82, 0x9D, 0xBC, 0xDF, 0x7A, 0x8E, 0x89, 0x80,
40 0x9B, 0xB6, 0xC1, 0x58, 0xE8, 0x23, 0x65, 0xAF, 0xEA, 0x25, 0x6F,
41 0xB1, 0xC8, 0x43, 0xC5, 0x54, 0xFC, 0x1F, 0x21, 0x63, 0xA5, 0xF4,
42 0x07, 0x09, 0x1B, 0x2D, 0x77, 0x99, 0xB0, 0xCB, 0x46, 0xCA, 0x45,
43 0xCF, 0x4A, 0xDE, 0x79, 0x8B, 0x86, 0x91, 0xA8, 0xE3, 0x3E, 0x42,
44 0xC6, 0x51, 0xF3, 0x0E, 0x12, 0x36, 0x5A, 0xEE, 0x29, 0x7B, 0x8D,
45 0x8C, 0x8F, 0x8A, 0x85, 0x94, 0xA7, 0xF2, 0x0D, 0x17, 0x39, 0x4B,
46 0xDD, 0x7C, 0x84, 0x97, 0xA2, 0xFD, 0x1C, 0x24, 0x6C, 0xB4, 0xC7,
47 0x52, 0xF6, 0x01 };
48 
49 /**
50 Table for GF(2^8) arithmetic (logarithms)
51 */
52 const uint8_t RTSS_LOG[] = {
53 0x90, 0x00, 0x19, 0x01, 0x32, 0x02, 0x1A, 0xC6, 0x4B, 0xC7, 0x1B,
54 0x68, 0x33, 0xEE, 0xDF, 0x03, 0x64, 0x04, 0xE0, 0x0E, 0x34, 0x8D,
55 0x81, 0xEF, 0x4C, 0x71, 0x08, 0xC8, 0xF8, 0x69, 0x1C, 0xC1, 0x7D,
56 0xC2, 0x1D, 0xB5, 0xF9, 0xB9, 0x27, 0x6A, 0x4D, 0xE4, 0xA6, 0x72,
57 0x9A, 0xC9, 0x09, 0x78, 0x65, 0x2F, 0x8A, 0x05, 0x21, 0x0F, 0xE1,
58 0x24, 0x12, 0xF0, 0x82, 0x45, 0x35, 0x93, 0xDA, 0x8E, 0x96, 0x8F,
59 0xDB, 0xBD, 0x36, 0xD0, 0xCE, 0x94, 0x13, 0x5C, 0xD2, 0xF1, 0x40,
60 0x46, 0x83, 0x38, 0x66, 0xDD, 0xFD, 0x30, 0xBF, 0x06, 0x8B, 0x62,
61 0xB3, 0x25, 0xE2, 0x98, 0x22, 0x88, 0x91, 0x10, 0x7E, 0x6E, 0x48,
62 0xC3, 0xA3, 0xB6, 0x1E, 0x42, 0x3A, 0x6B, 0x28, 0x54, 0xFA, 0x85,
63 0x3D, 0xBA, 0x2B, 0x79, 0x0A, 0x15, 0x9B, 0x9F, 0x5E, 0xCA, 0x4E,
64 0xD4, 0xAC, 0xE5, 0xF3, 0x73, 0xA7, 0x57, 0xAF, 0x58, 0xA8, 0x50,
65 0xF4, 0xEA, 0xD6, 0x74, 0x4F, 0xAE, 0xE9, 0xD5, 0xE7, 0xE6, 0xAD,
66 0xE8, 0x2C, 0xD7, 0x75, 0x7A, 0xEB, 0x16, 0x0B, 0xF5, 0x59, 0xCB,
67 0x5F, 0xB0, 0x9C, 0xA9, 0x51, 0xA0, 0x7F, 0x0C, 0xF6, 0x6F, 0x17,
68 0xC4, 0x49, 0xEC, 0xD8, 0x43, 0x1F, 0x2D, 0xA4, 0x76, 0x7B, 0xB7,
69 0xCC, 0xBB, 0x3E, 0x5A, 0xFB, 0x60, 0xB1, 0x86, 0x3B, 0x52, 0xA1,
70 0x6C, 0xAA, 0x55, 0x29, 0x9D, 0x97, 0xB2, 0x87, 0x90, 0x61, 0xBE,
71 0xDC, 0xFC, 0xBC, 0x95, 0xCF, 0xCD, 0x37, 0x3F, 0x5B, 0xD1, 0x53,
72 0x39, 0x84, 0x3C, 0x41, 0xA2, 0x6D, 0x47, 0x14, 0x2A, 0x9E, 0x5D,
73 0x56, 0xF2, 0xD3, 0xAB, 0x44, 0x11, 0x92, 0xD9, 0x23, 0x20, 0x2E,
74 0x89, 0xB4, 0x7C, 0xB8, 0x26, 0x77, 0x99, 0xE3, 0xA5, 0x67, 0x4A,
75 0xED, 0xDE, 0xC5, 0x31, 0xFE, 0x18, 0x0D, 0x63, 0x8C, 0x80, 0xC0,
76 0xF7, 0x70, 0x07 };
77 
78 uint8_t gfp_mul(uint8_t x, uint8_t y)
79  {
80  if(x == 0 || y == 0)
81  return 0;
82  return RTSS_EXP[(RTSS_LOG[x] + RTSS_LOG[y]) % 255];
83  }
84 
85 uint8_t rtss_hash_id(const std::string& hash_name)
86  {
87  if(hash_name == "None")
88  return 0;
89  else if(hash_name == "SHA-160" || hash_name == "SHA-1" || hash_name == "SHA1")
90  return 1;
91  else if(hash_name == "SHA-256")
92  return 2;
93  else
94  throw Invalid_Argument("RTSS only supports SHA-1 and SHA-256");
95  }
96 
97 std::unique_ptr<HashFunction> get_rtss_hash_by_id(uint8_t id)
98  {
99  if(id == 0)
100  return std::unique_ptr<HashFunction>();
101  if(id == 1)
102  return HashFunction::create_or_throw("SHA-1");
103  else if(id == 2)
104  return HashFunction::create_or_throw("SHA-256");
105  else
106  throw Decoding_Error("Unknown RTSS hash identifier");
107  }
108 
109 }
110 
111 RTSS_Share::RTSS_Share(const std::string& hex_input)
112  {
113  m_contents = hex_decode_locked(hex_input);
114  }
115 
116 RTSS_Share::RTSS_Share(const uint8_t bin[], size_t len)
117  {
118  m_contents.assign(bin, bin + len);
119  }
120 
121 uint8_t RTSS_Share::share_id() const
122  {
123  if(!initialized())
124  throw Invalid_State("RTSS_Share::share_id not initialized");
125 
126  if(m_contents.size() < RTSS_HEADER_SIZE + 1)
127  throw Decoding_Error("RTSS_Share::share_id invalid share data");
128 
129  return m_contents[20];
130  }
131 
132 std::string RTSS_Share::to_string() const
133  {
134  return hex_encode(m_contents.data(), m_contents.size());
135  }
136 
137 std::vector<RTSS_Share>
138 RTSS_Share::split(uint8_t M, uint8_t N,
139  const uint8_t S[], uint16_t S_len,
140  const uint8_t identifier[16],
142  {
143  return RTSS_Share::split(M, N, S, S_len,
144  std::vector<uint8_t>(identifier, identifier + 16),
145  "SHA-256",
146  rng);
147  }
148 
149 std::vector<RTSS_Share>
150 RTSS_Share::split(uint8_t M, uint8_t N,
151  const uint8_t S[], uint16_t S_len,
152  const std::vector<uint8_t>& identifier,
153  const std::string& hash_fn,
155  {
156  if(M <= 1 || N <= 1 || M > N || N >= 255)
157  throw Invalid_Argument("RTSS_Share::split: Invalid N or M");
158 
159  if(identifier.size() > 16)
160  throw Invalid_Argument("RTSS_Share::split Invalid identifier size");
161 
162  const uint8_t hash_id = rtss_hash_id(hash_fn);
163 
164  std::unique_ptr<HashFunction> hash;
165  if(hash_id > 0)
167 
168  // secret = S || H(S)
169  secure_vector<uint8_t> secret(S, S + S_len);
170  if(hash)
171  secret += hash->process(S, S_len);
172 
173  if(secret.size() >= 0xFFFE)
174  throw Encoding_Error("RTSS_Share::split secret too large for TSS format");
175 
176  // +1 byte for the share ID
177  const uint16_t share_len = static_cast<uint16_t>(secret.size() + 1);
178 
179  secure_vector<uint8_t> share_header(RTSS_HEADER_SIZE);
180  copy_mem(&share_header[0], identifier.data(), identifier.size());
181  share_header[16] = hash_id;
182  share_header[17] = M;
183  share_header[18] = get_byte(0, share_len);
184  share_header[19] = get_byte(1, share_len);
185 
186  // Create RTSS header in each share
187  std::vector<RTSS_Share> shares(N);
188 
189  for(uint8_t i = 0; i != N; ++i)
190  {
191  shares[i].m_contents.reserve(share_header.size() + share_len);
192  shares[i].m_contents = share_header;
193  }
194 
195  // Choose sequential values for X starting from 1
196  for(uint8_t i = 0; i != N; ++i)
197  shares[i].m_contents.push_back(i+1);
198 
199  for(size_t i = 0; i != secret.size(); ++i)
200  {
201  std::vector<uint8_t> coefficients(M-1);
202  rng.randomize(coefficients.data(), coefficients.size());
203 
204  for(uint8_t j = 0; j != N; ++j)
205  {
206  const uint8_t X = j + 1;
207 
208  uint8_t sum = secret[i];
209  uint8_t X_i = X;
210 
211  for(size_t k = 0; k != coefficients.size(); ++k)
212  {
213  sum ^= gfp_mul(X_i, coefficients[k]);
214  X_i = gfp_mul(X_i, X);
215  }
216 
217  shares[j].m_contents.push_back(sum);
218  }
219  }
220 
221  return shares;
222  }
223 
225 RTSS_Share::reconstruct(const std::vector<RTSS_Share>& shares)
226  {
227  if(shares.size() <= 1)
228  throw Decoding_Error("Insufficient shares to do TSS reconstruction");
229 
230  for(size_t i = 0; i != shares.size(); ++i)
231  {
232  if(shares[i].size() < RTSS_HEADER_SIZE + 1)
233  throw Decoding_Error("Missing or malformed RTSS header");
234 
235  if(shares[i].share_id() == 0)
236  throw Decoding_Error("Invalid (id = 0) RTSS share detected");
237 
238  if(i > 0)
239  {
240  if(shares[i].size() != shares[0].size())
241  throw Decoding_Error("Different sized RTSS shares detected");
242 
243  if(!same_mem(&shares[0].m_contents[0],
244  &shares[i].m_contents[0], RTSS_HEADER_SIZE))
245  throw Decoding_Error("Different RTSS headers detected");
246  }
247  }
248 
249  const uint8_t N = shares[0].m_contents[17];
250 
251  if(shares.size() < N)
252  throw Decoding_Error("Insufficient shares to do TSS reconstruction");
253 
254  const uint16_t share_len = make_uint16(shares[0].m_contents[18],
255  shares[0].m_contents[19]);
256 
257  const uint8_t hash_id = shares[0].m_contents[16];
258  std::unique_ptr<HashFunction> hash(get_rtss_hash_by_id(hash_id));
259  const size_t hash_len = (hash ? hash->output_length() : 0);
260 
261  if(shares[0].size() != RTSS_HEADER_SIZE + share_len)
262  {
263  /*
264  * This second (laxer) check accomodates a bug in TSS that was
265  * fixed in 2.9.0 - previous versions used the length of the
266  * *secret* here, instead of the length of the *share*, which is
267  * precisely 1 + hash_len longer.
268  */
269  if(shares[0].size() <= RTSS_HEADER_SIZE + 1 + hash_len)
270  throw Decoding_Error("Bad RTSS length field in header");
271  }
272 
273  std::vector<uint8_t> V(shares.size());
274  secure_vector<uint8_t> recovered;
275 
276  for(size_t i = RTSS_HEADER_SIZE + 1; i != shares[0].size(); ++i)
277  {
278  for(size_t j = 0; j != V.size(); ++j)
279  V[j] = shares[j].m_contents[i];
280 
281  uint8_t r = 0;
282  for(size_t k = 0; k != shares.size(); ++k)
283  {
284  // L_i function:
285  uint8_t r2 = 1;
286  for(size_t l = 0; l != shares.size(); ++l)
287  {
288  if(k == l)
289  continue;
290 
291  uint8_t share_k = shares[k].share_id();
292  uint8_t share_l = shares[l].share_id();
293 
294  if(share_k == share_l)
295  throw Decoding_Error("Duplicate shares found in RTSS recovery");
296 
297  uint8_t div = RTSS_EXP[(255 +
298  RTSS_LOG[share_l] -
299  RTSS_LOG[share_k ^ share_l]) % 255];
300 
301  r2 = gfp_mul(r2, div);
302  }
303 
304  r ^= gfp_mul(V[k], r2);
305  }
306  recovered.push_back(r);
307  }
308 
309  if(hash)
310  {
311  if(recovered.size() < hash->output_length())
312  throw Decoding_Error("RTSS recovered value too short to be valid");
313 
314  const size_t secret_len = recovered.size() - hash->output_length();
315 
316  hash->update(recovered.data(), secret_len);
317  secure_vector<uint8_t> hash_check = hash->final();
318 
319  if(!constant_time_compare(hash_check.data(),
320  &recovered[secret_len],
321  hash->output_length()))
322  {
323  throw Decoding_Error("RTSS hash check failed");
324  }
325 
326  // remove the trailing hash value
327  recovered.resize(secret_len);
328  }
329 
330  return recovered;
331  }
332 
333 }
fe X
Definition: ge.cpp:27
void hex_encode(char output[], const uint8_t input[], size_t input_length, bool uppercase)
Definition: hex.cpp:14
static secure_vector< uint8_t > reconstruct(const std::vector< RTSS_Share > &shares)
Definition: tss.cpp:225
static std::unique_ptr< HashFunction > create_or_throw(const std::string &algo_spec, const std::string &provider="")
Definition: hash.cpp:359
bool same_mem(const T *p1, const T *p2, size_t n)
Definition: mem_ops.h:187
RTSS_Share()=default
secure_vector< uint8_t > hex_decode_locked(const char input[], size_t input_length, bool ignore_ws)
Definition: hex.cpp:165
virtual void randomize(uint8_t output[], size_t length)=0
constexpr uint8_t get_byte(size_t byte_num, T input)
Definition: loadstor.h:39
bool constant_time_compare(const uint8_t x[], const uint8_t y[], size_t len)
Definition: mem_ops.h:81
uint8_t share_id() const
Definition: tss.cpp:121
std::string to_string() const
Definition: tss.cpp:132
size_t size() const
Definition: tss.h:92
bool initialized() const
Definition: tss.h:97
void copy_mem(T *out, const T *in, size_t n)
Definition: mem_ops.h:122
Definition: alg_id.cpp:13
static std::vector< RTSS_Share > split(uint8_t M, uint8_t N, const uint8_t secret[], uint16_t secret_len, const uint8_t identifier[16], RandomNumberGenerator &rng)
Definition: tss.cpp:138
std::vector< T, secure_allocator< T > > secure_vector
Definition: secmem.h:65
constexpr uint16_t make_uint16(uint8_t i0, uint8_t i1)
Definition: loadstor.h:52
MechanismType hash