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  }