5111374265

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84.68

/src/lib/misc/tss/tss.cpp

/*
* RTSS (threshold secret sharing)
* (C) 2009,2018 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/tss.h>

#include <botan/hash.h>
#include <botan/hex.h>
#include <botan/rng.h>
#include <botan/internal/loadstor.h>

namespace Botan {

namespace {

const size_t RTSS_HEADER_SIZE = 20;

/**
Table for GF(2^8) arithmetic (exponentials)
*/
alignas(64) const uint8_t RTSS_EXP[256] = {
   0x01, 0x03, 0x05, 0x0F, 0x11, 0x33, 0x55, 0xFF, 0x1A, 0x2E, 0x72, 0x96, 0xA1, 0xF8, 0x13, 0x35, 0x5F, 0xE1, 0x38,
   0x48, 0xD8, 0x73, 0x95, 0xA4, 0xF7, 0x02, 0x06, 0x0A, 0x1E, 0x22, 0x66, 0xAA, 0xE5, 0x34, 0x5C, 0xE4, 0x37, 0x59,
   0xEB, 0x26, 0x6A, 0xBE, 0xD9, 0x70, 0x90, 0xAB, 0xE6, 0x31, 0x53, 0xF5, 0x04, 0x0C, 0x14, 0x3C, 0x44, 0xCC, 0x4F,
   0xD1, 0x68, 0xB8, 0xD3, 0x6E, 0xB2, 0xCD, 0x4C, 0xD4, 0x67, 0xA9, 0xE0, 0x3B, 0x4D, 0xD7, 0x62, 0xA6, 0xF1, 0x08,
   0x18, 0x28, 0x78, 0x88, 0x83, 0x9E, 0xB9, 0xD0, 0x6B, 0xBD, 0xDC, 0x7F, 0x81, 0x98, 0xB3, 0xCE, 0x49, 0xDB, 0x76,
   0x9A, 0xB5, 0xC4, 0x57, 0xF9, 0x10, 0x30, 0x50, 0xF0, 0x0B, 0x1D, 0x27, 0x69, 0xBB, 0xD6, 0x61, 0xA3, 0xFE, 0x19,
   0x2B, 0x7D, 0x87, 0x92, 0xAD, 0xEC, 0x2F, 0x71, 0x93, 0xAE, 0xE9, 0x20, 0x60, 0xA0, 0xFB, 0x16, 0x3A, 0x4E, 0xD2,
   0x6D, 0xB7, 0xC2, 0x5D, 0xE7, 0x32, 0x56, 0xFA, 0x15, 0x3F, 0x41, 0xC3, 0x5E, 0xE2, 0x3D, 0x47, 0xC9, 0x40, 0xC0,
   0x5B, 0xED, 0x2C, 0x74, 0x9C, 0xBF, 0xDA, 0x75, 0x9F, 0xBA, 0xD5, 0x64, 0xAC, 0xEF, 0x2A, 0x7E, 0x82, 0x9D, 0xBC,
   0xDF, 0x7A, 0x8E, 0x89, 0x80, 0x9B, 0xB6, 0xC1, 0x58, 0xE8, 0x23, 0x65, 0xAF, 0xEA, 0x25, 0x6F, 0xB1, 0xC8, 0x43,
   0xC5, 0x54, 0xFC, 0x1F, 0x21, 0x63, 0xA5, 0xF4, 0x07, 0x09, 0x1B, 0x2D, 0x77, 0x99, 0xB0, 0xCB, 0x46, 0xCA, 0x45,
   0xCF, 0x4A, 0xDE, 0x79, 0x8B, 0x86, 0x91, 0xA8, 0xE3, 0x3E, 0x42, 0xC6, 0x51, 0xF3, 0x0E, 0x12, 0x36, 0x5A, 0xEE,
   0x29, 0x7B, 0x8D, 0x8C, 0x8F, 0x8A, 0x85, 0x94, 0xA7, 0xF2, 0x0D, 0x17, 0x39, 0x4B, 0xDD, 0x7C, 0x84, 0x97, 0xA2,
   0xFD, 0x1C, 0x24, 0x6C, 0xB4, 0xC7, 0x52, 0xF6, 0x01};

/**
Table for GF(2^8) arithmetic (logarithms)
*/
alignas(64) const uint8_t RTSS_LOG[] = {
   0x90, 0x00, 0x19, 0x01, 0x32, 0x02, 0x1A, 0xC6, 0x4B, 0xC7, 0x1B, 0x68, 0x33, 0xEE, 0xDF, 0x03, 0x64, 0x04, 0xE0,
   0x0E, 0x34, 0x8D, 0x81, 0xEF, 0x4C, 0x71, 0x08, 0xC8, 0xF8, 0x69, 0x1C, 0xC1, 0x7D, 0xC2, 0x1D, 0xB5, 0xF9, 0xB9,
   0x27, 0x6A, 0x4D, 0xE4, 0xA6, 0x72, 0x9A, 0xC9, 0x09, 0x78, 0x65, 0x2F, 0x8A, 0x05, 0x21, 0x0F, 0xE1, 0x24, 0x12,
   0xF0, 0x82, 0x45, 0x35, 0x93, 0xDA, 0x8E, 0x96, 0x8F, 0xDB, 0xBD, 0x36, 0xD0, 0xCE, 0x94, 0x13, 0x5C, 0xD2, 0xF1,
   0x40, 0x46, 0x83, 0x38, 0x66, 0xDD, 0xFD, 0x30, 0xBF, 0x06, 0x8B, 0x62, 0xB3, 0x25, 0xE2, 0x98, 0x22, 0x88, 0x91,
   0x10, 0x7E, 0x6E, 0x48, 0xC3, 0xA3, 0xB6, 0x1E, 0x42, 0x3A, 0x6B, 0x28, 0x54, 0xFA, 0x85, 0x3D, 0xBA, 0x2B, 0x79,
   0x0A, 0x15, 0x9B, 0x9F, 0x5E, 0xCA, 0x4E, 0xD4, 0xAC, 0xE5, 0xF3, 0x73, 0xA7, 0x57, 0xAF, 0x58, 0xA8, 0x50, 0xF4,
   0xEA, 0xD6, 0x74, 0x4F, 0xAE, 0xE9, 0xD5, 0xE7, 0xE6, 0xAD, 0xE8, 0x2C, 0xD7, 0x75, 0x7A, 0xEB, 0x16, 0x0B, 0xF5,
   0x59, 0xCB, 0x5F, 0xB0, 0x9C, 0xA9, 0x51, 0xA0, 0x7F, 0x0C, 0xF6, 0x6F, 0x17, 0xC4, 0x49, 0xEC, 0xD8, 0x43, 0x1F,
   0x2D, 0xA4, 0x76, 0x7B, 0xB7, 0xCC, 0xBB, 0x3E, 0x5A, 0xFB, 0x60, 0xB1, 0x86, 0x3B, 0x52, 0xA1, 0x6C, 0xAA, 0x55,
   0x29, 0x9D, 0x97, 0xB2, 0x87, 0x90, 0x61, 0xBE, 0xDC, 0xFC, 0xBC, 0x95, 0xCF, 0xCD, 0x37, 0x3F, 0x5B, 0xD1, 0x53,
   0x39, 0x84, 0x3C, 0x41, 0xA2, 0x6D, 0x47, 0x14, 0x2A, 0x9E, 0x5D, 0x56, 0xF2, 0xD3, 0xAB, 0x44, 0x11, 0x92, 0xD9,
   0x23, 0x20, 0x2E, 0x89, 0xB4, 0x7C, 0xB8, 0x26, 0x77, 0x99, 0xE3, 0xA5, 0x67, 0x4A, 0xED, 0xDE, 0xC5, 0x31, 0xFE,
   0x18, 0x0D, 0x63, 0x8C, 0x80, 0xC0, 0xF7, 0x70, 0x07};

uint8_t gfp_mul(uint8_t x, uint8_t y) {
   if(x == 0 || y == 0)
      return 0;
   return RTSS_EXP[(RTSS_LOG[x] + RTSS_LOG[y]) % 255];
}

uint8_t rtss_hash_id(std::string_view hash_name) {
   if(hash_name == "None")
      return 0;
   else if(hash_name == "SHA-1")
      return 1;
   else if(hash_name == "SHA-256")
      return 2;
   else
      throw Invalid_Argument("RTSS only supports SHA-1 and SHA-256");
}

std::unique_ptr<HashFunction> get_rtss_hash_by_id(uint8_t id) {
   if(id == 0)
      return std::unique_ptr<HashFunction>();
   if(id == 1)
      return HashFunction::create_or_throw("SHA-1");
   else if(id == 2)
      return HashFunction::create_or_throw("SHA-256");
   else
      throw Decoding_Error("Unknown RTSS hash identifier");
}

}  // namespace

RTSS_Share::RTSS_Share(std::string_view hex_input) { m_contents = hex_decode_locked(hex_input); }

RTSS_Share::RTSS_Share(const uint8_t bin[], size_t len) { m_contents.assign(bin, bin + len); }

uint8_t RTSS_Share::share_id() const {
   if(!initialized())
      throw Invalid_State("RTSS_Share::share_id not initialized");

   if(m_contents.size() < RTSS_HEADER_SIZE + 1)
      throw Decoding_Error("RTSS_Share::share_id invalid share data");

   return m_contents[20];
}

std::string RTSS_Share::to_string() const { return hex_encode(m_contents.data(), m_contents.size()); }

std::vector<RTSS_Share> RTSS_Share::split(
   uint8_t M, uint8_t N, const uint8_t S[], uint16_t S_len, const uint8_t identifier[16], RandomNumberGenerator& rng) {
   return RTSS_Share::split(M, N, S, S_len, std::vector<uint8_t>(identifier, identifier + 16), "SHA-256", rng);
}

std::vector<RTSS_Share> RTSS_Share::split(uint8_t M,
                                          uint8_t N,
                                          const uint8_t S[],
                                          uint16_t S_len,
                                          const std::vector<uint8_t>& identifier,
                                          std::string_view hash_fn,
                                          RandomNumberGenerator& rng) {
   if(M <= 1 || N <= 1 || M > N || N >= 255)
      throw Invalid_Argument("RTSS_Share::split: Invalid N or M");

   if(identifier.size() > 16)
      throw Invalid_Argument("RTSS_Share::split Invalid identifier size");

   const uint8_t hash_id = rtss_hash_id(hash_fn);

   std::unique_ptr<HashFunction> hash;
   if(hash_id > 0)
      hash = HashFunction::create_or_throw(hash_fn);

   // secret = S || H(S)
   secure_vector<uint8_t> secret(S, S + S_len);
   if(hash)
      secret += hash->process(S, S_len);

   if(secret.size() >= 0xFFFE)
      throw Encoding_Error("RTSS_Share::split secret too large for TSS format");

   // +1 byte for the share ID
   const uint16_t share_len = static_cast<uint16_t>(secret.size() + 1);

   secure_vector<uint8_t> share_header(RTSS_HEADER_SIZE);
   copy_mem(&share_header[0], identifier.data(), identifier.size());
   share_header[16] = hash_id;
   share_header[17] = M;
   share_header[18] = get_byte<0>(share_len);
   share_header[19] = get_byte<1>(share_len);

   // Create RTSS header in each share
   std::vector<RTSS_Share> shares(N);

   for(uint8_t i = 0; i != N; ++i) {
      shares[i].m_contents.reserve(share_header.size() + share_len);
      shares[i].m_contents = share_header;
   }

   // Choose sequential values for X starting from 1
   for(uint8_t i = 0; i != N; ++i)
      shares[i].m_contents.push_back(i + 1);

   for(size_t i = 0; i != secret.size(); ++i) {
      std::vector<uint8_t> coefficients(M - 1);
      rng.randomize(coefficients.data(), coefficients.size());

      for(uint8_t j = 0; j != N; ++j) {
         const uint8_t X = j + 1;

         uint8_t sum = secret[i];
         uint8_t X_i = X;

         for(size_t k = 0; k != coefficients.size(); ++k) {
            sum ^= gfp_mul(X_i, coefficients[k]);
            X_i = gfp_mul(X_i, X);
         }

         shares[j].m_contents.push_back(sum);
      }
   }

   return shares;
}

secure_vector<uint8_t> RTSS_Share::reconstruct(const std::vector<RTSS_Share>& shares) {
   if(shares.size() <= 1)
      throw Decoding_Error("Insufficient shares to do TSS reconstruction");

   for(size_t i = 0; i != shares.size(); ++i) {
      if(shares[i].size() < RTSS_HEADER_SIZE + 1)
         throw Decoding_Error("Missing or malformed RTSS header");

      if(shares[i].share_id() == 0)
         throw Decoding_Error("Invalid (id = 0) RTSS share detected");

      if(i > 0) {
         if(shares[i].size() != shares[0].size())
            throw Decoding_Error("Different sized RTSS shares detected");

         if(!same_mem(&shares[0].m_contents[0], &shares[i].m_contents[0], RTSS_HEADER_SIZE))
            throw Decoding_Error("Different RTSS headers detected");
      }
   }

   const uint8_t N = shares[0].m_contents[17];

   if(shares.size() < N)
      throw Decoding_Error("Insufficient shares to do TSS reconstruction");

   const uint16_t share_len = make_uint16(shares[0].m_contents[18], shares[0].m_contents[19]);

   const uint8_t hash_id = shares[0].m_contents[16];
   auto hash = get_rtss_hash_by_id(hash_id);
   const size_t hash_len = (hash ? hash->output_length() : 0);

   if(shares[0].size() != RTSS_HEADER_SIZE + share_len) {
      /*
      * This second (laxer) check accomodates a bug in TSS that was
      * fixed in 2.9.0 - previous versions used the length of the
      * *secret* here, instead of the length of the *share*, which is
      * precisely 1 + hash_len longer.
      */
      if(shares[0].size() <= RTSS_HEADER_SIZE + 1 + hash_len)
         throw Decoding_Error("Bad RTSS length field in header");
   }

   std::vector<uint8_t> V(shares.size());
   secure_vector<uint8_t> recovered;

   for(size_t i = RTSS_HEADER_SIZE + 1; i != shares[0].size(); ++i) {
      for(size_t j = 0; j != V.size(); ++j)
         V[j] = shares[j].m_contents[i];

      uint8_t r = 0;
      for(size_t k = 0; k != shares.size(); ++k) {
         // L_i function:
         uint8_t r2 = 1;
         for(size_t l = 0; l != shares.size(); ++l) {
            if(k == l)
               continue;

            uint8_t share_k = shares[k].share_id();
            uint8_t share_l = shares[l].share_id();

            if(share_k == share_l)
               throw Decoding_Error("Duplicate shares found in RTSS recovery");

            uint8_t div = RTSS_EXP[(255 + RTSS_LOG[share_l] - RTSS_LOG[share_k ^ share_l]) % 255];

            r2 = gfp_mul(r2, div);
         }

         r ^= gfp_mul(V[k], r2);
      }
      recovered.push_back(r);
   }

   if(hash) {
      if(recovered.size() < hash->output_length())
         throw Decoding_Error("RTSS recovered value too short to be valid");

      const size_t secret_len = recovered.size() - hash->output_length();

      hash->update(recovered.data(), secret_len);
      secure_vector<uint8_t> hash_check = hash->final();

      if(!constant_time_compare(hash_check.data(), &recovered[secret_len], hash->output_length())) {
         throw Decoding_Error("RTSS hash check failed");
      }

      // remove the trailing hash value
      recovered.resize(secret_len);
   }

   return recovered;
}

}  // namespace Botan

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
10	#include <botan/hash.h>
11	#include <botan/hex.h>
12	#include <botan/rng.h>
13	#include <botan/internal/loadstor.h>
14
15	namespace Botan {
16
17	namespace {
18
19	const size_t RTSS_HEADER_SIZE = 20;
20
21	/**
22	Table for GF(2^8) arithmetic (exponentials)
23	*/
24	alignas(64) const uint8_t RTSS_EXP[256] = {
25	0x01, 0x03, 0x05, 0x0F, 0x11, 0x33, 0x55, 0xFF, 0x1A, 0x2E, 0x72, 0x96, 0xA1, 0xF8, 0x13, 0x35, 0x5F, 0xE1, 0x38,
26	0x48, 0xD8, 0x73, 0x95, 0xA4, 0xF7, 0x02, 0x06, 0x0A, 0x1E, 0x22, 0x66, 0xAA, 0xE5, 0x34, 0x5C, 0xE4, 0x37, 0x59,
27	0xEB, 0x26, 0x6A, 0xBE, 0xD9, 0x70, 0x90, 0xAB, 0xE6, 0x31, 0x53, 0xF5, 0x04, 0x0C, 0x14, 0x3C, 0x44, 0xCC, 0x4F,
28	0xD1, 0x68, 0xB8, 0xD3, 0x6E, 0xB2, 0xCD, 0x4C, 0xD4, 0x67, 0xA9, 0xE0, 0x3B, 0x4D, 0xD7, 0x62, 0xA6, 0xF1, 0x08,
29	0x18, 0x28, 0x78, 0x88, 0x83, 0x9E, 0xB9, 0xD0, 0x6B, 0xBD, 0xDC, 0x7F, 0x81, 0x98, 0xB3, 0xCE, 0x49, 0xDB, 0x76,
30	0x9A, 0xB5, 0xC4, 0x57, 0xF9, 0x10, 0x30, 0x50, 0xF0, 0x0B, 0x1D, 0x27, 0x69, 0xBB, 0xD6, 0x61, 0xA3, 0xFE, 0x19,
31	0x2B, 0x7D, 0x87, 0x92, 0xAD, 0xEC, 0x2F, 0x71, 0x93, 0xAE, 0xE9, 0x20, 0x60, 0xA0, 0xFB, 0x16, 0x3A, 0x4E, 0xD2,
32	0x6D, 0xB7, 0xC2, 0x5D, 0xE7, 0x32, 0x56, 0xFA, 0x15, 0x3F, 0x41, 0xC3, 0x5E, 0xE2, 0x3D, 0x47, 0xC9, 0x40, 0xC0,
33	0x5B, 0xED, 0x2C, 0x74, 0x9C, 0xBF, 0xDA, 0x75, 0x9F, 0xBA, 0xD5, 0x64, 0xAC, 0xEF, 0x2A, 0x7E, 0x82, 0x9D, 0xBC,
34	0xDF, 0x7A, 0x8E, 0x89, 0x80, 0x9B, 0xB6, 0xC1, 0x58, 0xE8, 0x23, 0x65, 0xAF, 0xEA, 0x25, 0x6F, 0xB1, 0xC8, 0x43,
35	0xC5, 0x54, 0xFC, 0x1F, 0x21, 0x63, 0xA5, 0xF4, 0x07, 0x09, 0x1B, 0x2D, 0x77, 0x99, 0xB0, 0xCB, 0x46, 0xCA, 0x45,
36	0xCF, 0x4A, 0xDE, 0x79, 0x8B, 0x86, 0x91, 0xA8, 0xE3, 0x3E, 0x42, 0xC6, 0x51, 0xF3, 0x0E, 0x12, 0x36, 0x5A, 0xEE,
37	0x29, 0x7B, 0x8D, 0x8C, 0x8F, 0x8A, 0x85, 0x94, 0xA7, 0xF2, 0x0D, 0x17, 0x39, 0x4B, 0xDD, 0x7C, 0x84, 0x97, 0xA2,
38	0xFD, 0x1C, 0x24, 0x6C, 0xB4, 0xC7, 0x52, 0xF6, 0x01};
39
40	/**
41	Table for GF(2^8) arithmetic (logarithms)
42	*/
43	alignas(64) const uint8_t RTSS_LOG[] = {
44	0x90, 0x00, 0x19, 0x01, 0x32, 0x02, 0x1A, 0xC6, 0x4B, 0xC7, 0x1B, 0x68, 0x33, 0xEE, 0xDF, 0x03, 0x64, 0x04, 0xE0,
45	0x0E, 0x34, 0x8D, 0x81, 0xEF, 0x4C, 0x71, 0x08, 0xC8, 0xF8, 0x69, 0x1C, 0xC1, 0x7D, 0xC2, 0x1D, 0xB5, 0xF9, 0xB9,
46	0x27, 0x6A, 0x4D, 0xE4, 0xA6, 0x72, 0x9A, 0xC9, 0x09, 0x78, 0x65, 0x2F, 0x8A, 0x05, 0x21, 0x0F, 0xE1, 0x24, 0x12,
47	0xF0, 0x82, 0x45, 0x35, 0x93, 0xDA, 0x8E, 0x96, 0x8F, 0xDB, 0xBD, 0x36, 0xD0, 0xCE, 0x94, 0x13, 0x5C, 0xD2, 0xF1,
48	0x40, 0x46, 0x83, 0x38, 0x66, 0xDD, 0xFD, 0x30, 0xBF, 0x06, 0x8B, 0x62, 0xB3, 0x25, 0xE2, 0x98, 0x22, 0x88, 0x91,
49	0x10, 0x7E, 0x6E, 0x48, 0xC3, 0xA3, 0xB6, 0x1E, 0x42, 0x3A, 0x6B, 0x28, 0x54, 0xFA, 0x85, 0x3D, 0xBA, 0x2B, 0x79,
50	0x0A, 0x15, 0x9B, 0x9F, 0x5E, 0xCA, 0x4E, 0xD4, 0xAC, 0xE5, 0xF3, 0x73, 0xA7, 0x57, 0xAF, 0x58, 0xA8, 0x50, 0xF4,
51	0xEA, 0xD6, 0x74, 0x4F, 0xAE, 0xE9, 0xD5, 0xE7, 0xE6, 0xAD, 0xE8, 0x2C, 0xD7, 0x75, 0x7A, 0xEB, 0x16, 0x0B, 0xF5,
52	0x59, 0xCB, 0x5F, 0xB0, 0x9C, 0xA9, 0x51, 0xA0, 0x7F, 0x0C, 0xF6, 0x6F, 0x17, 0xC4, 0x49, 0xEC, 0xD8, 0x43, 0x1F,
53	0x2D, 0xA4, 0x76, 0x7B, 0xB7, 0xCC, 0xBB, 0x3E, 0x5A, 0xFB, 0x60, 0xB1, 0x86, 0x3B, 0x52, 0xA1, 0x6C, 0xAA, 0x55,
54	0x29, 0x9D, 0x97, 0xB2, 0x87, 0x90, 0x61, 0xBE, 0xDC, 0xFC, 0xBC, 0x95, 0xCF, 0xCD, 0x37, 0x3F, 0x5B, 0xD1, 0x53,
55	0x39, 0x84, 0x3C, 0x41, 0xA2, 0x6D, 0x47, 0x14, 0x2A, 0x9E, 0x5D, 0x56, 0xF2, 0xD3, 0xAB, 0x44, 0x11, 0x92, 0xD9,
56	0x23, 0x20, 0x2E, 0x89, 0xB4, 0x7C, 0xB8, 0x26, 0x77, 0x99, 0xE3, 0xA5, 0x67, 0x4A, 0xED, 0xDE, 0xC5, 0x31, 0xFE,
57	0x18, 0x0D, 0x63, 0x8C, 0x80, 0xC0, 0xF7, 0x70, 0x07};
58
59	uint8_t gfp_mul(uint8_t x, uint8_t y) {	29,633✔
60	if(x == 0 \|\| y == 0)	5,922✔
61	return 0;
62	return RTSS_EXP[(RTSS_LOG[x] + RTSS_LOG[y]) % 255];	29,609✔
63	}
64
65	uint8_t rtss_hash_id(std::string_view hash_name) {	7✔
66	if(hash_name == "None")	7✔
67	return 0;	4✔
68	else if(hash_name == "SHA-1")	3✔
69	return 1;	1✔
70	else if(hash_name == "SHA-256")	2✔
71	return 2;	2✔
72	else
73	throw Invalid_Argument("RTSS only supports SHA-1 and SHA-256");	×
74	}
75
76	std::unique_ptr<HashFunction> get_rtss_hash_by_id(uint8_t id) {	34✔
77	if(id == 0)	34✔
78	return std::unique_ptr<HashFunction>();	34✔
79	if(id == 1)	12✔
80	return HashFunction::create_or_throw("SHA-1");	3✔
81	else if(id == 2)	9✔
82	return HashFunction::create_or_throw("SHA-256");	9✔
83	else
84	throw Decoding_Error("Unknown RTSS hash identifier");	×
85	}
86
87	} // namespace
88
89	RTSS_Share::RTSS_Share(std::string_view hex_input) { m_contents = hex_decode_locked(hex_input); }	×
90
91	RTSS_Share::RTSS_Share(const uint8_t bin[], size_t len) { m_contents.assign(bin, bin + len); }	54✔
92
93	uint8_t RTSS_Share::share_id() const {	43,459✔
94	if(!initialized())	43,459✔
95	throw Invalid_State("RTSS_Share::share_id not initialized");	×
96
97	if(m_contents.size() < RTSS_HEADER_SIZE + 1)	43,459✔
98	throw Decoding_Error("RTSS_Share::share_id invalid share data");	×
99
100	return m_contents[20];	43,459✔
101	}
102
103	std::string RTSS_Share::to_string() const { return hex_encode(m_contents.data(), m_contents.size()); }	×
104
105	std::vector<RTSS_Share> RTSS_Share::split(	×
106	uint8_t M, uint8_t N, const uint8_t S[], uint16_t S_len, const uint8_t identifier[16], RandomNumberGenerator& rng) {
107	return RTSS_Share::split(M, N, S, S_len, std::vector<uint8_t>(identifier, identifier + 16), "SHA-256", rng);	×
108	}
109
110	std::vector<RTSS_Share> RTSS_Share::split(uint8_t M,	7✔
111	uint8_t N,
112	const uint8_t S[],
113	uint16_t S_len,
114	const std::vector<uint8_t>& identifier,
115	std::string_view hash_fn,
116	RandomNumberGenerator& rng) {
117	if(M <= 1 \|\| N <= 1 \|\| M > N \|\| N >= 255)	7✔
118	throw Invalid_Argument("RTSS_Share::split: Invalid N or M");	×
119
120	if(identifier.size() > 16)	7✔
121	throw Invalid_Argument("RTSS_Share::split Invalid identifier size");	×
122
123	const uint8_t hash_id = rtss_hash_id(hash_fn);	7✔
124
125	std::unique_ptr<HashFunction> hash;	7✔
126	if(hash_id > 0)	7✔
127	hash = HashFunction::create_or_throw(hash_fn);	3✔
128
129	// secret = S \|\| H(S)
130	secure_vector<uint8_t> secret(S, S + S_len);	7✔
131	if(hash)	7✔
132	secret += hash->process(S, S_len);	9✔
133
134	if(secret.size() >= 0xFFFE)	7✔
135	throw Encoding_Error("RTSS_Share::split secret too large for TSS format");	×
136
137	// +1 byte for the share ID
138	const uint16_t share_len = static_cast<uint16_t>(secret.size() + 1);	7✔
139
140	secure_vector<uint8_t> share_header(RTSS_HEADER_SIZE);	7✔
141	copy_mem(&share_header[0], identifier.data(), identifier.size());	7✔
142	share_header[16] = hash_id;	7✔
143	share_header[17] = M;	7✔
144	share_header[18] = get_byte<0>(share_len);	7✔
145	share_header[19] = get_byte<1>(share_len);	7✔
146
147	// Create RTSS header in each share
148	std::vector<RTSS_Share> shares(N);	7✔
149
150	for(uint8_t i = 0; i != N; ++i) {	46✔
151	shares[i].m_contents.reserve(share_header.size() + share_len);	39✔
152	shares[i].m_contents = share_header;	39✔
153	}
154
155	// Choose sequential values for X starting from 1
156	for(uint8_t i = 0; i != N; ++i)	46✔
157	shares[i].m_contents.push_back(i + 1);	39✔
158
159	for(size_t i = 0; i != secret.size(); ++i) {	210✔
160	std::vector<uint8_t> coefficients(M - 1);	203✔
161	rng.randomize(coefficients.data(), coefficients.size());	203✔
162
163	for(uint8_t j = 0; j != N; ++j) {	1,158✔
164	const uint8_t X = j + 1;	955✔
165
166	uint8_t sum = secret[i];	955✔
167	uint8_t X_i = X;	955✔
168
169	for(size_t k = 0; k != coefficients.size(); ++k) {	3,044✔
170	sum ^= gfp_mul(X_i, coefficients[k]);	2,089✔
171	X_i = gfp_mul(X_i, X);	4,178✔
172	}
173
174	shares[j].m_contents.push_back(sum);	955✔
175	}
176	}	203✔
177
178	return shares;	7✔
179	}	17✔
180
181	secure_vector<uint8_t> RTSS_Share::reconstruct(const std::vector<RTSS_Share>& shares) {	35✔
182	if(shares.size() <= 1)	35✔
183	throw Decoding_Error("Insufficient shares to do TSS reconstruction");	×
184
185	for(size_t i = 0; i != shares.size(); ++i) {	250✔
186	if(shares[i].size() < RTSS_HEADER_SIZE + 1)	215✔
187	throw Decoding_Error("Missing or malformed RTSS header");	×
188
189	if(shares[i].share_id() == 0)	215✔
190	throw Decoding_Error("Invalid (id = 0) RTSS share detected");	×
191
192	if(i > 0) {	215✔
193	if(shares[i].size() != shares[0].size())	180✔
194	throw Decoding_Error("Different sized RTSS shares detected");	×
195
196	if(!same_mem(&shares[0].m_contents[0], &shares[i].m_contents[0], RTSS_HEADER_SIZE))	360✔
197	throw Decoding_Error("Different RTSS headers detected");	×
198	}
199	}
200
201	const uint8_t N = shares[0].m_contents[17];	35✔
202
203	if(shares.size() < N)	35✔
204	throw Decoding_Error("Insufficient shares to do TSS reconstruction");	1✔
205
206	const uint16_t share_len = make_uint16(shares[0].m_contents[18], shares[0].m_contents[19]);	34✔
207
208	const uint8_t hash_id = shares[0].m_contents[16];	34✔
209	auto hash = get_rtss_hash_by_id(hash_id);	34✔
210	const size_t hash_len = (hash ? hash->output_length() : 0);	34✔
211
212	if(shares[0].size() != RTSS_HEADER_SIZE + share_len) {	34✔
213	/*
214	* This second (laxer) check accomodates a bug in TSS that was
215	* fixed in 2.9.0 - previous versions used the length of the
216	* secret here, instead of the length of the share, which is
217	* precisely 1 + hash_len longer.
218	*/
219	if(shares[0].size() <= RTSS_HEADER_SIZE + 1 + hash_len)	3✔
220	throw Decoding_Error("Bad RTSS length field in header");	×
221	}
222
223	std::vector<uint8_t> V(shares.size());	35✔
224	secure_vector<uint8_t> recovered;	34✔
225
226	for(size_t i = RTSS_HEADER_SIZE + 1; i != shares[0].size(); ++i) {	887✔
227	for(size_t j = 0; j != V.size(); ++j)	4,686✔
228	V[j] = shares[j].m_contents[i];	3,833✔
229
230	uint8_t r = 0;	853✔
231	for(size_t k = 0; k != shares.size(); ++k) {	4,686✔
232	// L_i function:
233	uint8_t r2 = 1;
234	for(size_t l = 0; l != shares.size(); ++l) {	29,288✔
235	if(k == l)	25,455✔
236	continue;	3,833✔
237
238	uint8_t share_k = shares[k].share_id();	21,622✔
239	uint8_t share_l = shares[l].share_id();	21,622✔
240
241	if(share_k == share_l)	21,622✔
242	throw Decoding_Error("Duplicate shares found in RTSS recovery");	×
243
244	uint8_t div = RTSS_EXP[(255 + RTSS_LOG[share_l] - RTSS_LOG[share_k ^ share_l]) % 255];	21,622✔
245
246	r2 = gfp_mul(r2, div);	47,077✔
247	}
248
249	r ^= gfp_mul(V[k], r2);	7,659✔
250	}
251	recovered.push_back(r);	853✔
252	}
253
254	if(hash) {	34✔
255	if(recovered.size() < hash->output_length())	12✔
256	throw Decoding_Error("RTSS recovered value too short to be valid");	×
257
258	const size_t secret_len = recovered.size() - hash->output_length();	12✔
259
260	hash->update(recovered.data(), secret_len);	12✔
261	secure_vector<uint8_t> hash_check = hash->final();	12✔
262
263	if(!constant_time_compare(hash_check.data(), &recovered[secret_len], hash->output_length())) {	12✔
264	throw Decoding_Error("RTSS hash check failed");	1✔
265	}
266
267	// remove the trailing hash value
268	recovered.resize(secret_len);	11✔
269	}	12✔
270
271	return recovered;	33✔
272	}	46✔
273
274	} // namespace Botan

randombit / botan / 5111374265

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