Bitcoin Core  22.99.0
P2P Digital Currency
asmap.cpp
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1 // Copyright (c) 2019-2020 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 <util/asmap.h>
6 
7 #include <clientversion.h>
8 #include <crypto/common.h>
9 #include <logging.h>
10 #include <streams.h>
11 
12 #include <cassert>
13 #include <map>
14 #include <vector>
15 
16 namespace {
17 
18 constexpr uint32_t INVALID = 0xFFFFFFFF;
19 
20 uint32_t DecodeBits(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos, uint8_t minval, const std::vector<uint8_t> &bit_sizes)
21 {
22  uint32_t val = minval;
23  bool bit;
24  for (std::vector<uint8_t>::const_iterator bit_sizes_it = bit_sizes.begin();
25  bit_sizes_it != bit_sizes.end(); ++bit_sizes_it) {
26  if (bit_sizes_it + 1 != bit_sizes.end()) {
27  if (bitpos == endpos) break;
28  bit = *bitpos;
29  bitpos++;
30  } else {
31  bit = 0;
32  }
33  if (bit) {
34  val += (1 << *bit_sizes_it);
35  } else {
36  for (int b = 0; b < *bit_sizes_it; b++) {
37  if (bitpos == endpos) return INVALID; // Reached EOF in mantissa
38  bit = *bitpos;
39  bitpos++;
40  val += bit << (*bit_sizes_it - 1 - b);
41  }
42  return val;
43  }
44  }
45  return INVALID; // Reached EOF in exponent
46 }
47 
48 enum class Instruction : uint32_t
49 {
50  RETURN = 0,
51  JUMP = 1,
52  MATCH = 2,
53  DEFAULT = 3,
54 };
55 
56 const std::vector<uint8_t> TYPE_BIT_SIZES{0, 0, 1};
57 Instruction DecodeType(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
58 {
59  return Instruction(DecodeBits(bitpos, endpos, 0, TYPE_BIT_SIZES));
60 }
61 
62 const std::vector<uint8_t> ASN_BIT_SIZES{15, 16, 17, 18, 19, 20, 21, 22, 23, 24};
63 uint32_t DecodeASN(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
64 {
65  return DecodeBits(bitpos, endpos, 1, ASN_BIT_SIZES);
66 }
67 
68 
69 const std::vector<uint8_t> MATCH_BIT_SIZES{1, 2, 3, 4, 5, 6, 7, 8};
70 uint32_t DecodeMatch(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
71 {
72  return DecodeBits(bitpos, endpos, 2, MATCH_BIT_SIZES);
73 }
74 
75 
76 const std::vector<uint8_t> JUMP_BIT_SIZES{5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30};
77 uint32_t DecodeJump(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
78 {
79  return DecodeBits(bitpos, endpos, 17, JUMP_BIT_SIZES);
80 }
81 
82 }
83 
84 uint32_t Interpret(const std::vector<bool> &asmap, const std::vector<bool> &ip)
85 {
86  std::vector<bool>::const_iterator pos = asmap.begin();
87  const std::vector<bool>::const_iterator endpos = asmap.end();
88  uint8_t bits = ip.size();
89  uint32_t default_asn = 0;
90  uint32_t jump, match, matchlen;
91  Instruction opcode;
92  while (pos != endpos) {
93  opcode = DecodeType(pos, endpos);
94  if (opcode == Instruction::RETURN) {
95  default_asn = DecodeASN(pos, endpos);
96  if (default_asn == INVALID) break; // ASN straddles EOF
97  return default_asn;
98  } else if (opcode == Instruction::JUMP) {
99  jump = DecodeJump(pos, endpos);
100  if (jump == INVALID) break; // Jump offset straddles EOF
101  if (bits == 0) break; // No input bits left
102  if (int64_t{jump} >= int64_t{endpos - pos}) break; // Jumping past EOF
103  if (ip[ip.size() - bits]) {
104  pos += jump;
105  }
106  bits--;
107  } else if (opcode == Instruction::MATCH) {
108  match = DecodeMatch(pos, endpos);
109  if (match == INVALID) break; // Match bits straddle EOF
110  matchlen = CountBits(match) - 1;
111  if (bits < matchlen) break; // Not enough input bits
112  for (uint32_t bit = 0; bit < matchlen; bit++) {
113  if ((ip[ip.size() - bits]) != ((match >> (matchlen - 1 - bit)) & 1)) {
114  return default_asn;
115  }
116  bits--;
117  }
118  } else if (opcode == Instruction::DEFAULT) {
119  default_asn = DecodeASN(pos, endpos);
120  if (default_asn == INVALID) break; // ASN straddles EOF
121  } else {
122  break; // Instruction straddles EOF
123  }
124  }
125  assert(false); // Reached EOF without RETURN, or aborted (see any of the breaks above) - should have been caught by SanityCheckASMap below
126  return 0; // 0 is not a valid ASN
127 }
128 
129 bool SanityCheckASMap(const std::vector<bool>& asmap, int bits)
130 {
131  const std::vector<bool>::const_iterator begin = asmap.begin(), endpos = asmap.end();
132  std::vector<bool>::const_iterator pos = begin;
133  std::vector<std::pair<uint32_t, int>> jumps; // All future positions we may jump to (bit offset in asmap -> bits to consume left)
134  jumps.reserve(bits);
135  Instruction prevopcode = Instruction::JUMP;
136  bool had_incomplete_match = false;
137  while (pos != endpos) {
138  uint32_t offset = pos - begin;
139  if (!jumps.empty() && offset >= jumps.back().first) return false; // There was a jump into the middle of the previous instruction
140  Instruction opcode = DecodeType(pos, endpos);
141  if (opcode == Instruction::RETURN) {
142  if (prevopcode == Instruction::DEFAULT) return false; // There should not be any RETURN immediately after a DEFAULT (could be combined into just RETURN)
143  uint32_t asn = DecodeASN(pos, endpos);
144  if (asn == INVALID) return false; // ASN straddles EOF
145  if (jumps.empty()) {
146  // Nothing to execute anymore
147  if (endpos - pos > 7) return false; // Excessive padding
148  while (pos != endpos) {
149  if (*pos) return false; // Nonzero padding bit
150  ++pos;
151  }
152  return true; // Sanely reached EOF
153  } else {
154  // Continue by pretending we jumped to the next instruction
155  offset = pos - begin;
156  if (offset != jumps.back().first) return false; // Unreachable code
157  bits = jumps.back().second; // Restore the number of bits we would have had left after this jump
158  jumps.pop_back();
159  prevopcode = Instruction::JUMP;
160  }
161  } else if (opcode == Instruction::JUMP) {
162  uint32_t jump = DecodeJump(pos, endpos);
163  if (jump == INVALID) return false; // Jump offset straddles EOF
164  if (int64_t{jump} > int64_t{endpos - pos}) return false; // Jump out of range
165  if (bits == 0) return false; // Consuming bits past the end of the input
166  --bits;
167  uint32_t jump_offset = pos - begin + jump;
168  if (!jumps.empty() && jump_offset >= jumps.back().first) return false; // Intersecting jumps
169  jumps.emplace_back(jump_offset, bits);
170  prevopcode = Instruction::JUMP;
171  } else if (opcode == Instruction::MATCH) {
172  uint32_t match = DecodeMatch(pos, endpos);
173  if (match == INVALID) return false; // Match bits straddle EOF
174  int matchlen = CountBits(match) - 1;
175  if (prevopcode != Instruction::MATCH) had_incomplete_match = false;
176  if (matchlen < 8 && had_incomplete_match) return false; // Within a sequence of matches only at most one should be incomplete
177  had_incomplete_match = (matchlen < 8);
178  if (bits < matchlen) return false; // Consuming bits past the end of the input
179  bits -= matchlen;
180  prevopcode = Instruction::MATCH;
181  } else if (opcode == Instruction::DEFAULT) {
182  if (prevopcode == Instruction::DEFAULT) return false; // There should not be two successive DEFAULTs (they could be combined into one)
183  uint32_t asn = DecodeASN(pos, endpos);
184  if (asn == INVALID) return false; // ASN straddles EOF
185  prevopcode = Instruction::DEFAULT;
186  } else {
187  return false; // Instruction straddles EOF
188  }
189  }
190  return false; // Reached EOF without RETURN instruction
191 }
192 
193 std::vector<bool> DecodeAsmap(fs::path path)
194 {
195  std::vector<bool> bits;
196  FILE *filestr = fsbridge::fopen(path, "rb");
197  CAutoFile file(filestr, SER_DISK, CLIENT_VERSION);
198  if (file.IsNull()) {
199  LogPrintf("Failed to open asmap file from disk\n");
200  return bits;
201  }
202  fseek(filestr, 0, SEEK_END);
203  int length = ftell(filestr);
204  LogPrintf("Opened asmap file %s (%d bytes) from disk\n", path, length);
205  fseek(filestr, 0, SEEK_SET);
206  uint8_t cur_byte;
207  for (int i = 0; i < length; ++i) {
208  file >> cur_byte;
209  for (int bit = 0; bit < 8; ++bit) {
210  bits.push_back((cur_byte >> bit) & 1);
211  }
212  }
213  if (!SanityCheckASMap(bits, 128)) {
214  LogPrintf("Sanity check of asmap file %s failed\n", path);
215  return {};
216  }
217  return bits;
218 }
219 
assert
assert(!tx.IsCoinBase())
SER_DISK
@ SER_DISK
Definition: serialize.h:139
fsbridge::fopen
FILE * fopen(const fs::path &p, const char *mode)
Definition: fs.cpp:24
asmap.h
streams.h
clientversion.h
common.h
CAutoFile
Non-refcounted RAII wrapper for FILE*.
Definition: streams.h:564
bech32::Encoding::INVALID
@ INVALID
Failed decoding.
DecodeAsmap
std::vector< bool > DecodeAsmap(fs::path path)
Read asmap from provided binary file.
Definition: asmap.cpp:193
ip
static CService ip(uint32_t i)
Definition: denialofservice_tests.cpp:30
LogPrintf
#define LogPrintf(...)
Definition: logging.h:185
CAutoFile::IsNull
bool IsNull() const
Return true if the wrapped FILE* is nullptr, false otherwise.
Definition: streams.h:609
Interpret
uint32_t Interpret(const std::vector< bool > &asmap, const std::vector< bool > &ip)
Definition: asmap.cpp:84
CLIENT_VERSION
static const int CLIENT_VERSION
bitcoind-res.rc includes this file, but it cannot cope with real c++ code.
Definition: clientversion.h:33
VarIntMode::DEFAULT
@ DEFAULT
SanityCheckASMap
bool SanityCheckASMap(const std::vector< bool > &asmap, int bits)
Definition: asmap.cpp:129
CountBits
static uint64_t CountBits(uint64_t x)
Return the smallest number n such that (x >> n) == 0 (or 64 if the highest bit in x is set.
Definition: common.h:90