asmap_direct.cpp raw

   1  // Copyright (c) 2020-present The Bitcoin Core developers
   2  // Distributed under the MIT software license, see the accompanying
   3  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   4  
   5  #include <netaddress.h>
   6  #include <util/asmap.h>
   7  #include <test/fuzz/fuzz.h>
   8  
   9  #include <cstdint>
  10  #include <optional>
  11  #include <vector>
  12  
  13  #include <cassert>
  14  
  15  std::vector<std::byte> BitsToBytes(std::span<const uint8_t> bits) noexcept
  16  {
  17      std::vector<std::byte> ret;
  18      uint8_t next_byte{0};
  19      int next_byte_bits{0};
  20      for (uint8_t val : bits) {
  21          next_byte |= (val & 1) << (next_byte_bits++);
  22          if (next_byte_bits == 8) {
  23              ret.push_back(std::byte(next_byte));
  24              next_byte = 0;
  25              next_byte_bits = 0;
  26          }
  27      }
  28      if (next_byte_bits) ret.push_back(std::byte(next_byte));
  29  
  30      return ret;
  31  }
  32  
  33  FUZZ_TARGET(asmap_direct)
  34  {
  35      // Encoding: [asmap using 1 bit / byte] 0xFF [addr using 1 bit / byte]
  36      std::optional<size_t> sep_pos_opt;
  37      for (size_t pos = 0; pos < buffer.size(); ++pos) {
  38          uint8_t x = buffer[pos];
  39          if ((x & 0xFE) == 0) continue;
  40          if (x == 0xFF) {
  41              if (sep_pos_opt) return;
  42              sep_pos_opt = pos;
  43          } else {
  44              return;
  45          }
  46      }
  47      if (!sep_pos_opt) return; // Needs exactly 1 separator
  48      const size_t sep_pos{sep_pos_opt.value()};
  49      const size_t ip_len{buffer.size() - sep_pos - 1};
  50      if (ip_len > 128) return; // At most 128 bits in IP address
  51  
  52      // Checks on asmap
  53      auto asmap = BitsToBytes(buffer.first(sep_pos));
  54      if (SanityCheckAsmap(asmap, ip_len)) {
  55          // Verify that for valid asmaps, no prefix (except up to 7 zero padding bits) is valid.
  56          for (size_t prefix_len = sep_pos - 1; prefix_len > 0; --prefix_len) {
  57              auto prefix = BitsToBytes(buffer.first(prefix_len));
  58              // We have to skip the prefixes of the same length as the original
  59              // asmap, since they will contain some zero padding bits in the last
  60              // byte.
  61              if (prefix.size() == asmap.size()) continue;
  62              assert(!SanityCheckAsmap(prefix, ip_len));
  63          }
  64  
  65          // No address input should trigger assertions in interpreter
  66          auto addr = BitsToBytes(buffer.subspan(sep_pos + 1));
  67          (void)Interpret(asmap, addr);
  68      }
  69  }
  70