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