Coverage Report

Created: 2020-02-14 15:38

/src/botan/src/lib/pk_pad/eme_pkcs1/eme_pkcs.cpp
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/*
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* PKCS #1 v1.5 Type 2 (encryption) padding
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* (C) 1999-2007,2015,2016 Jack Lloyd
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*
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* Botan is released under the Simplified BSD License (see license.txt)
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*/
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#include <botan/eme_pkcs.h>
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#include <botan/exceptn.h>
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#include <botan/rng.h>
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#include <botan/internal/ct_utils.h>
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namespace Botan {
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/*
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* PKCS1 Pad Operation
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*/
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secure_vector<uint8_t> EME_PKCS1v15::pad(const uint8_t in[], size_t inlen,
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                                     size_t key_length,
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                                     RandomNumberGenerator& rng) const
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   {
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   key_length /= 8;
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   if(inlen > maximum_input_size(key_length * 8))
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      {
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      throw Invalid_Argument("PKCS1: Input is too large");
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      }
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   secure_vector<uint8_t> out(key_length);
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   out[0] = 0x02;
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   rng.randomize(out.data() + 1, (key_length - inlen - 2));
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   for(size_t j = 1; j != key_length - inlen - 1; ++j)
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      {
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      if(out[j] == 0)
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         {
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         out[j] = rng.next_nonzero_byte();
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         }
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      }
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   buffer_insert(out, key_length - inlen, in, inlen);
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   return out;
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   }
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/*
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* PKCS1 Unpad Operation
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*/
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secure_vector<uint8_t> EME_PKCS1v15::unpad(uint8_t& valid_mask,
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                                        const uint8_t in[], size_t inlen) const
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   {
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   /*
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   * RSA decryption pads the ciphertext up to the modulus size, so this only
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   * occurs with very (!) small keys, or when fuzzing.
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   *
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   * 11 bytes == 00,02 + 8 bytes mandatory padding + 00
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   */
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   if(inlen < 11)
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      {
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      valid_mask = false;
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      return secure_vector<uint8_t>();
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      }
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   CT::poison(in, inlen);
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   CT::Mask<uint8_t> bad_input_m = CT::Mask<uint8_t>::cleared();
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   CT::Mask<uint8_t> seen_zero_m = CT::Mask<uint8_t>::cleared();
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   size_t delim_idx = 2; // initial 0002
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   bad_input_m |= ~CT::Mask<uint8_t>::is_equal(in[0], 0);
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   bad_input_m |= ~CT::Mask<uint8_t>::is_equal(in[1], 2);
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   for(size_t i = 2; i < inlen; ++i)
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      {
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      const auto is_zero_m = CT::Mask<uint8_t>::is_zero(in[i]);
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      delim_idx += seen_zero_m.if_not_set_return(1);
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      seen_zero_m |= is_zero_m;
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      }
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   // no zero delim -> bad padding
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   bad_input_m |= ~seen_zero_m;
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   /*
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   delim indicates < 8 bytes padding -> bad padding
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   We require 11 here because we are counting also the 00 delim byte
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   */
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   bad_input_m |= CT::Mask<uint8_t>(CT::Mask<size_t>::is_lt(delim_idx, 11));
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   valid_mask = (~bad_input_m).unpoisoned_value();
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   const secure_vector<uint8_t> output = CT::copy_output(bad_input_m, in, inlen, delim_idx);
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   CT::unpoison(in, inlen);
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   return output;
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   }
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/*
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* Return the max input size for a given key size
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*/
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size_t EME_PKCS1v15::maximum_input_size(size_t keybits) const
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   {
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   if(keybits / 8 > 10)
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      return ((keybits / 8) - 10);
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   else
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      return 0;
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   }
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}