Bitcoin Core  24.99.0
P2P Digital Currency
asmap.cpp
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1 // Copyright (c) 2019-2022 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 <fs.h>
10 #include <logging.h>
11 #include <serialize.h>
12 #include <streams.h>
13 
14 #include <algorithm>
15 #include <cassert>
16 #include <cstdio>
17 #include <utility>
18 #include <vector>
19 
20 namespace {
21 
22 constexpr uint32_t INVALID = 0xFFFFFFFF;
23 
24 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)
25 {
26  uint32_t val = minval;
27  bool bit;
28  for (std::vector<uint8_t>::const_iterator bit_sizes_it = bit_sizes.begin();
29  bit_sizes_it != bit_sizes.end(); ++bit_sizes_it) {
30  if (bit_sizes_it + 1 != bit_sizes.end()) {
31  if (bitpos == endpos) break;
32  bit = *bitpos;
33  bitpos++;
34  } else {
35  bit = 0;
36  }
37  if (bit) {
38  val += (1 << *bit_sizes_it);
39  } else {
40  for (int b = 0; b < *bit_sizes_it; b++) {
41  if (bitpos == endpos) return INVALID; // Reached EOF in mantissa
42  bit = *bitpos;
43  bitpos++;
44  val += bit << (*bit_sizes_it - 1 - b);
45  }
46  return val;
47  }
48  }
49  return INVALID; // Reached EOF in exponent
50 }
51 
52 enum class Instruction : uint32_t
53 {
54  RETURN = 0,
55  JUMP = 1,
56  MATCH = 2,
57  DEFAULT = 3,
58 };
59 
60 const std::vector<uint8_t> TYPE_BIT_SIZES{0, 0, 1};
61 Instruction DecodeType(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
62 {
63  return Instruction(DecodeBits(bitpos, endpos, 0, TYPE_BIT_SIZES));
64 }
65 
66 const std::vector<uint8_t> ASN_BIT_SIZES{15, 16, 17, 18, 19, 20, 21, 22, 23, 24};
67 uint32_t DecodeASN(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
68 {
69  return DecodeBits(bitpos, endpos, 1, ASN_BIT_SIZES);
70 }
71 
72 
73 const std::vector<uint8_t> MATCH_BIT_SIZES{1, 2, 3, 4, 5, 6, 7, 8};
74 uint32_t DecodeMatch(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
75 {
76  return DecodeBits(bitpos, endpos, 2, MATCH_BIT_SIZES);
77 }
78 
79 
80 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};
81 uint32_t DecodeJump(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
82 {
83  return DecodeBits(bitpos, endpos, 17, JUMP_BIT_SIZES);
84 }
85 
86 }
87 
88 uint32_t Interpret(const std::vector<bool> &asmap, const std::vector<bool> &ip)
89 {
90  std::vector<bool>::const_iterator pos = asmap.begin();
91  const std::vector<bool>::const_iterator endpos = asmap.end();
92  uint8_t bits = ip.size();
93  uint32_t default_asn = 0;
94  uint32_t jump, match, matchlen;
95  Instruction opcode;
96  while (pos != endpos) {
97  opcode = DecodeType(pos, endpos);
98  if (opcode == Instruction::RETURN) {
99  default_asn = DecodeASN(pos, endpos);
100  if (default_asn == INVALID) break; // ASN straddles EOF
101  return default_asn;
102  } else if (opcode == Instruction::JUMP) {
103  jump = DecodeJump(pos, endpos);
104  if (jump == INVALID) break; // Jump offset straddles EOF
105  if (bits == 0) break; // No input bits left
106  if (int64_t{jump} >= int64_t{endpos - pos}) break; // Jumping past EOF
107  if (ip[ip.size() - bits]) {
108  pos += jump;
109  }
110  bits--;
111  } else if (opcode == Instruction::MATCH) {
112  match = DecodeMatch(pos, endpos);
113  if (match == INVALID) break; // Match bits straddle EOF
114  matchlen = CountBits(match) - 1;
115  if (bits < matchlen) break; // Not enough input bits
116  for (uint32_t bit = 0; bit < matchlen; bit++) {
117  if ((ip[ip.size() - bits]) != ((match >> (matchlen - 1 - bit)) & 1)) {
118  return default_asn;
119  }
120  bits--;
121  }
122  } else if (opcode == Instruction::DEFAULT) {
123  default_asn = DecodeASN(pos, endpos);
124  if (default_asn == INVALID) break; // ASN straddles EOF
125  } else {
126  break; // Instruction straddles EOF
127  }
128  }
129  assert(false); // Reached EOF without RETURN, or aborted (see any of the breaks above) - should have been caught by SanityCheckASMap below
130  return 0; // 0 is not a valid ASN
131 }
132 
133 bool SanityCheckASMap(const std::vector<bool>& asmap, int bits)
134 {
135  const std::vector<bool>::const_iterator begin = asmap.begin(), endpos = asmap.end();
136  std::vector<bool>::const_iterator pos = begin;
137  std::vector<std::pair<uint32_t, int>> jumps; // All future positions we may jump to (bit offset in asmap -> bits to consume left)
138  jumps.reserve(bits);
139  Instruction prevopcode = Instruction::JUMP;
140  bool had_incomplete_match = false;
141  while (pos != endpos) {
142  uint32_t offset = pos - begin;
143  if (!jumps.empty() && offset >= jumps.back().first) return false; // There was a jump into the middle of the previous instruction
144  Instruction opcode = DecodeType(pos, endpos);
145  if (opcode == Instruction::RETURN) {
146  if (prevopcode == Instruction::DEFAULT) return false; // There should not be any RETURN immediately after a DEFAULT (could be combined into just RETURN)
147  uint32_t asn = DecodeASN(pos, endpos);
148  if (asn == INVALID) return false; // ASN straddles EOF
149  if (jumps.empty()) {
150  // Nothing to execute anymore
151  if (endpos - pos > 7) return false; // Excessive padding
152  while (pos != endpos) {
153  if (*pos) return false; // Nonzero padding bit
154  ++pos;
155  }
156  return true; // Sanely reached EOF
157  } else {
158  // Continue by pretending we jumped to the next instruction
159  offset = pos - begin;
160  if (offset != jumps.back().first) return false; // Unreachable code
161  bits = jumps.back().second; // Restore the number of bits we would have had left after this jump
162  jumps.pop_back();
163  prevopcode = Instruction::JUMP;
164  }
165  } else if (opcode == Instruction::JUMP) {
166  uint32_t jump = DecodeJump(pos, endpos);
167  if (jump == INVALID) return false; // Jump offset straddles EOF
168  if (int64_t{jump} > int64_t{endpos - pos}) return false; // Jump out of range
169  if (bits == 0) return false; // Consuming bits past the end of the input
170  --bits;
171  uint32_t jump_offset = pos - begin + jump;
172  if (!jumps.empty() && jump_offset >= jumps.back().first) return false; // Intersecting jumps
173  jumps.emplace_back(jump_offset, bits);
174  prevopcode = Instruction::JUMP;
175  } else if (opcode == Instruction::MATCH) {
176  uint32_t match = DecodeMatch(pos, endpos);
177  if (match == INVALID) return false; // Match bits straddle EOF
178  int matchlen = CountBits(match) - 1;
179  if (prevopcode != Instruction::MATCH) had_incomplete_match = false;
180  if (matchlen < 8 && had_incomplete_match) return false; // Within a sequence of matches only at most one should be incomplete
181  had_incomplete_match = (matchlen < 8);
182  if (bits < matchlen) return false; // Consuming bits past the end of the input
183  bits -= matchlen;
184  prevopcode = Instruction::MATCH;
185  } else if (opcode == Instruction::DEFAULT) {
186  if (prevopcode == Instruction::DEFAULT) return false; // There should not be two successive DEFAULTs (they could be combined into one)
187  uint32_t asn = DecodeASN(pos, endpos);
188  if (asn == INVALID) return false; // ASN straddles EOF
189  prevopcode = Instruction::DEFAULT;
190  } else {
191  return false; // Instruction straddles EOF
192  }
193  }
194  return false; // Reached EOF without RETURN instruction
195 }
196 
197 std::vector<bool> DecodeAsmap(fs::path path)
198 {
199  std::vector<bool> bits;
200  FILE *filestr = fsbridge::fopen(path, "rb");
201  AutoFile file{filestr};
202  if (file.IsNull()) {
203  LogPrintf("Failed to open asmap file from disk\n");
204  return bits;
205  }
206  fseek(filestr, 0, SEEK_END);
207  int length = ftell(filestr);
208  LogPrintf("Opened asmap file %s (%d bytes) from disk\n", fs::quoted(fs::PathToString(path)), length);
209  fseek(filestr, 0, SEEK_SET);
210  uint8_t cur_byte;
211  for (int i = 0; i < length; ++i) {
212  file >> cur_byte;
213  for (int bit = 0; bit < 8; ++bit) {
214  bits.push_back((cur_byte >> bit) & 1);
215  }
216  }
217  if (!SanityCheckASMap(bits, 128)) {
218  LogPrintf("Sanity check of asmap file %s failed\n", fs::quoted(fs::PathToString(path)));
219  return {};
220  }
221  return bits;
222 }
223 
Non-refcounted RAII wrapper for FILE*.
Definition: streams.h:496
Path class wrapper to block calls to the fs::path(std::string) implicit constructor and the fs::path:...
Definition: fs.h:31
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
static CService ip(uint32_t i)
#define LogPrintf(...)
Definition: logging.h:236
@ INVALID
Failed decoding.
static auto quoted(const std::string &s)
Definition: fs.h:94
static std::string PathToString(const path &path)
Convert path object to a byte string.
Definition: fs.h:150
FILE * fopen(const fs::path &p, const char *mode)
Definition: fs.cpp:25
uint32_t Interpret(const std::vector< bool > &asmap, const std::vector< bool > &ip)
Definition: asmap.cpp:88
std::vector< bool > DecodeAsmap(fs::path path)
Read asmap from provided binary file.
Definition: asmap.cpp:197
bool SanityCheckASMap(const std::vector< bool > &asmap, int bits)
Definition: asmap.cpp:133
assert(!tx.IsCoinBase())