Branch data     Line data    Source code

       1                 :            : // Copyright (c) 2023 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 <bip324.h>
       6                 :            : #include <chainparams.h>
       7                 :            : #include <span.h>
       8                 :            : #include <test/fuzz/FuzzedDataProvider.h>
       9                 :            : #include <test/fuzz/fuzz.h>
      10                 :            : #include <test/fuzz/util.h>
      11                 :            : #include <test/util/xoroshiro128plusplus.h>
      12                 :            : 
      13                 :            : #include <cstdint>
      14                 :            : #include <vector>
      15                 :            : 
      16                 :            : namespace {
      17                 :            : 
      18                 :          0 : void Initialize()
      19                 :            : {
      20                 :          0 :     ECC_Start();
      21                 :          0 :     SelectParams(ChainType::MAIN);
      22                 :          0 : }
      23                 :            : 
      24                 :            : }  // namespace
      25                 :            : 
      26   [ +  -  -  + ]:          4 : FUZZ_TARGET(bip324_cipher_roundtrip, .init=Initialize)
      27                 :            : {
      28                 :            :     // Test that BIP324Cipher's encryption and decryption agree.
      29                 :            : 
      30                 :            :     // Load keys from fuzzer.
      31                 :          0 :     FuzzedDataProvider provider(buffer.data(), buffer.size());
      32                 :            :     // Initiator key
      33                 :          0 :     CKey init_key = ConsumePrivateKey(provider, /*compressed=*/true);
      34   [ #  #  #  # ]:          0 :     if (!init_key.IsValid()) return;
      35                 :            :     // Initiator entropy
      36         [ #  # ]:          0 :     auto init_ent = provider.ConsumeBytes<std::byte>(32);
      37         [ #  # ]:          0 :     init_ent.resize(32);
      38                 :            :     // Responder key
      39         [ #  # ]:          0 :     CKey resp_key = ConsumePrivateKey(provider, /*compressed=*/true);
      40   [ #  #  #  # ]:          0 :     if (!resp_key.IsValid()) return;
      41                 :            :     // Responder entropy
      42         [ #  # ]:          0 :     auto resp_ent = provider.ConsumeBytes<std::byte>(32);
      43         [ #  # ]:          0 :     resp_ent.resize(32);
      44                 :            : 
      45                 :            :     // Initialize ciphers by exchanging public keys.
      46         [ #  # ]:          0 :     BIP324Cipher initiator(init_key, init_ent);
      47         [ #  # ]:          0 :     assert(!initiator);
      48         [ #  # ]:          0 :     BIP324Cipher responder(resp_key, resp_ent);
      49         [ #  # ]:          0 :     assert(!responder);
      50                 :          0 :     initiator.Initialize(responder.GetOurPubKey(), true);
      51         [ #  # ]:          0 :     assert(initiator);
      52                 :          0 :     responder.Initialize(initiator.GetOurPubKey(), false);
      53         [ #  # ]:          0 :     assert(responder);
      54                 :            : 
      55                 :            :     // Initialize RNG deterministically, to generate contents and AAD. We assume that there are no
      56                 :            :     // (potentially buggy) edge cases triggered by specific values of contents/AAD, so we can avoid
      57                 :            :     // reading the actual data for those from the fuzzer input (which would need large amounts of
      58                 :            :     // data).
      59         [ #  # ]:          0 :     XoRoShiRo128PlusPlus rng(provider.ConsumeIntegral<uint64_t>());
      60                 :            : 
      61                 :            :     // Compare session IDs and garbage terminators.
      62         [ #  # ]:          0 :     assert(initiator.GetSessionID() == responder.GetSessionID());
      63         [ #  # ]:          0 :     assert(initiator.GetSendGarbageTerminator() == responder.GetReceiveGarbageTerminator());
      64         [ #  # ]:          0 :     assert(initiator.GetReceiveGarbageTerminator() == responder.GetSendGarbageTerminator());
      65                 :            : 
      66   [ #  #  #  #  :          0 :     LIMITED_WHILE(provider.remaining_bytes(), 1000) {
                   #  # ]
      67                 :            :         // Mode:
      68                 :            :         // - Bit 0: whether the ignore bit is set in message
      69                 :            :         // - Bit 1: whether the responder (0) or initiator (1) sends
      70                 :            :         // - Bit 2: whether this ciphertext will be corrupted (making it the last sent one)
      71                 :            :         // - Bit 3-4: controls the maximum aad length (max 4095 bytes)
      72                 :            :         // - Bit 5-7: controls the maximum content length (max 16383 bytes, for performance reasons)
      73         [ #  # ]:          0 :         unsigned mode = provider.ConsumeIntegral<uint8_t>();
      74                 :          0 :         bool ignore = mode & 1;
      75                 :          0 :         bool from_init = mode & 2;
      76                 :          0 :         bool damage = mode & 4;
      77                 :          0 :         unsigned aad_length_bits = 4 * ((mode >> 3) & 3);
      78         [ #  # ]:          0 :         unsigned aad_length = provider.ConsumeIntegralInRange<unsigned>(0, (1 << aad_length_bits) - 1);
      79                 :          0 :         unsigned length_bits = 2 * ((mode >> 5) & 7);
      80         [ #  # ]:          0 :         unsigned length = provider.ConsumeIntegralInRange<unsigned>(0, (1 << length_bits) - 1);
      81                 :            :         // Generate aad and content.
      82         [ #  # ]:          0 :         std::vector<std::byte> aad(aad_length);
      83         [ #  # ]:          0 :         for (auto& val : aad) val = std::byte{(uint8_t)rng()};
      84         [ #  # ]:          0 :         std::vector<std::byte> contents(length);
      85         [ #  # ]:          0 :         for (auto& val : contents) val = std::byte{(uint8_t)rng()};
      86                 :            : 
      87                 :            :         // Pick sides.
      88         [ #  # ]:          0 :         auto& sender{from_init ? initiator : responder};
      89         [ #  # ]:          0 :         auto& receiver{from_init ? responder : initiator};
      90                 :            : 
      91                 :            :         // Encrypt
      92         [ #  # ]:          0 :         std::vector<std::byte> ciphertext(length + initiator.EXPANSION);
      93   [ #  #  #  #  :          0 :         sender.Encrypt(contents, aad, ignore, ciphertext);
                   #  # ]
      94                 :            : 
      95                 :            :         // Optionally damage 1 bit in either the ciphertext (corresponding to a change in transit)
      96                 :            :         // or the aad (to make sure that decryption will fail if the AAD mismatches).
      97         [ #  # ]:          0 :         if (damage) {
      98         [ #  # ]:          0 :             unsigned damage_bit = provider.ConsumeIntegralInRange<unsigned>(0,
      99                 :          0 :                 (ciphertext.size() + aad.size()) * 8U - 1U);
     100                 :          0 :             unsigned damage_pos = damage_bit >> 3;
     101                 :          0 :             std::byte damage_val{(uint8_t)(1U << (damage_bit & 3))};
     102         [ #  # ]:          0 :             if (damage_pos >= ciphertext.size()) {
     103                 :          0 :                 aad[damage_pos - ciphertext.size()] ^= damage_val;
     104                 :          0 :             } else {
     105                 :          0 :                 ciphertext[damage_pos] ^= damage_val;
     106                 :            :             }
     107                 :          0 :         }
     108                 :            : 
     109                 :            :         // Decrypt length
     110         [ #  # ]:          0 :         uint32_t dec_length = receiver.DecryptLength(Span{ciphertext}.first(initiator.LENGTH_LEN));
     111         [ #  # ]:          0 :         if (!damage) {
     112         [ #  # ]:          0 :             assert(dec_length == length);
     113                 :          0 :         } else {
     114                 :            :             // For performance reasons, don't try to decode if length got increased too much.
     115         [ #  # ]:          0 :             if (dec_length > 16384 + length) break;
     116                 :            :             // Otherwise, just append zeros if dec_length > length.
     117         [ #  # ]:          0 :             ciphertext.resize(dec_length + initiator.EXPANSION);
     118                 :            :         }
     119                 :            : 
     120                 :            :         // Decrypt
     121         [ #  # ]:          0 :         std::vector<std::byte> decrypt(dec_length);
     122                 :          0 :         bool dec_ignore{false};
     123   [ #  #  #  #  :          0 :         bool ok = receiver.Decrypt(Span{ciphertext}.subspan(initiator.LENGTH_LEN), aad, dec_ignore, decrypt);
                   #  # ]
     124                 :            :         // Decryption *must* fail if the packet was damaged, and succeed if it wasn't.
     125         [ #  # ]:          0 :         assert(!ok == damage);
     126         [ #  # ]:          0 :         if (!ok) break;
     127         [ #  # ]:          0 :         assert(ignore == dec_ignore);
     128   [ #  #  #  # ]:          0 :         assert(decrypt == contents);
     129         [ #  # ]:          0 :     }
     130                 :          0 : }