Line data Source code
1 : // Copyright (c) 2019-2021 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 <fs.h>
9 : #include <logging.h>
10 : #include <serialize.h>
11 : #include <streams.h>
12 :
13 : #include <algorithm>
14 : #include <bit>
15 : #include <cassert>
16 : #include <cstdio>
17 : #include <utility>
18 : #include <vector>
19 :
20 : namespace {
21 :
22 : constexpr uint32_t INVALID = 0xFFFFFFFF;
23 :
24 119100 : 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 119100 : uint32_t val = minval;
27 : bool bit;
28 591203 : for (std::vector<uint8_t>::const_iterator bit_sizes_it = bit_sizes.begin();
29 591203 : bit_sizes_it != bit_sizes.end(); ++bit_sizes_it) {
30 591203 : if (bit_sizes_it + 1 != bit_sizes.end()) {
31 489199 : if (bitpos == endpos) break;
32 489199 : bit = *bitpos;
33 489199 : bitpos++;
34 489199 : } else {
35 102004 : bit = 0;
36 : }
37 591203 : if (bit) {
38 472103 : val += (1 << *bit_sizes_it);
39 472103 : } else {
40 666754 : for (int b = 0; b < *bit_sizes_it; b++) {
41 547654 : if (bitpos == endpos) return INVALID; // Reached EOF in mantissa
42 547654 : bit = *bitpos;
43 547654 : bitpos++;
44 547654 : val += bit << (*bit_sizes_it - 1 - b);
45 547654 : }
46 119100 : return val;
47 : }
48 472103 : }
49 0 : return INVALID; // Reached EOF in exponent
50 119100 : }
51 :
52 : enum class Instruction : uint32_t
53 : {
54 : RETURN = 0,
55 : JUMP = 1,
56 : MATCH = 2,
57 : DEFAULT = 3,
58 : };
59 :
60 3308 : const std::vector<uint8_t> TYPE_BIT_SIZES{0, 0, 1};
61 59550 : Instruction DecodeType(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
62 : {
63 59550 : return Instruction(DecodeBits(bitpos, endpos, 0, TYPE_BIT_SIZES));
64 : }
65 :
66 3308 : const std::vector<uint8_t> ASN_BIT_SIZES{15, 16, 17, 18, 19, 20, 21, 22, 23, 24};
67 3821 : uint32_t DecodeASN(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
68 : {
69 3821 : return DecodeBits(bitpos, endpos, 1, ASN_BIT_SIZES);
70 : }
71 :
72 :
73 3308 : const std::vector<uint8_t> MATCH_BIT_SIZES{1, 2, 3, 4, 5, 6, 7, 8};
74 51170 : uint32_t DecodeMatch(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
75 : {
76 51170 : return DecodeBits(bitpos, endpos, 2, MATCH_BIT_SIZES);
77 : }
78 :
79 :
80 3308 : 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 4559 : uint32_t DecodeJump(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
82 : {
83 4559 : return DecodeBits(bitpos, endpos, 17, JUMP_BIT_SIZES);
84 : }
85 :
86 : }
87 :
88 4173 : uint32_t Interpret(const std::vector<bool> &asmap, const std::vector<bool> &ip)
89 : {
90 4173 : std::vector<bool>::const_iterator pos = asmap.begin();
91 4173 : const std::vector<bool>::const_iterator endpos = asmap.end();
92 4173 : uint8_t bits = ip.size();
93 4173 : uint32_t default_asn = 0;
94 : uint32_t jump, match, matchlen;
95 : Instruction opcode;
96 59116 : while (pos != endpos) {
97 59116 : opcode = DecodeType(pos, endpos);
98 59116 : if (opcode == Instruction::RETURN) {
99 3695 : default_asn = DecodeASN(pos, endpos);
100 3695 : if (default_asn == INVALID) break; // ASN straddles EOF
101 3695 : return default_asn;
102 55421 : } else if (opcode == Instruction::JUMP) {
103 4447 : jump = DecodeJump(pos, endpos);
104 4447 : if (jump == INVALID) break; // Jump offset straddles EOF
105 4447 : if (bits == 0) break; // No input bits left
106 4447 : if (int64_t{jump} >= int64_t{endpos - pos}) break; // Jumping past EOF
107 4447 : if (ip[ip.size() - bits]) {
108 3635 : pos += jump;
109 3635 : }
110 4447 : bits--;
111 55421 : } else if (opcode == Instruction::MATCH) {
112 50974 : match = DecodeMatch(pos, endpos);
113 50974 : if (match == INVALID) break; // Match bits straddle EOF
114 50974 : matchlen = std::bit_width(match) - 1;
115 50974 : if (bits < matchlen) break; // Not enough input bits
116 456358 : for (uint32_t bit = 0; bit < matchlen; bit++) {
117 405862 : if ((ip[ip.size() - bits]) != ((match >> (matchlen - 1 - bit)) & 1)) {
118 478 : return default_asn;
119 : }
120 405384 : bits--;
121 405384 : }
122 50496 : } 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 4173 : }
132 :
133 16 : bool SanityCheckASMap(const std::vector<bool>& asmap, int bits)
134 : {
135 16 : const std::vector<bool>::const_iterator begin = asmap.begin(), endpos = asmap.end();
136 16 : std::vector<bool>::const_iterator pos = begin;
137 16 : std::vector<std::pair<uint32_t, int>> jumps; // All future positions we may jump to (bit offset in asmap -> bits to consume left)
138 16 : jumps.reserve(bits);
139 16 : Instruction prevopcode = Instruction::JUMP;
140 16 : bool had_incomplete_match = false;
141 436 : while (pos != endpos) {
142 434 : uint32_t offset = pos - begin;
143 434 : if (!jumps.empty() && offset >= jumps.back().first) return false; // There was a jump into the middle of the previous instruction
144 434 : Instruction opcode = DecodeType(pos, endpos);
145 434 : if (opcode == Instruction::RETURN) {
146 126 : if (prevopcode == Instruction::DEFAULT) return false; // There should not be any RETURN immediately after a DEFAULT (could be combined into just RETURN)
147 126 : uint32_t asn = DecodeASN(pos, endpos);
148 126 : if (asn == INVALID) return false; // ASN straddles EOF
149 126 : if (jumps.empty()) {
150 : // Nothing to execute anymore
151 14 : if (endpos - pos > 7) return false; // Excessive padding
152 42 : while (pos != endpos) {
153 28 : if (*pos) return false; // Nonzero padding bit
154 28 : ++pos;
155 : }
156 14 : return true; // Sanely reached EOF
157 : } else {
158 : // Continue by pretending we jumped to the next instruction
159 112 : offset = pos - begin;
160 112 : if (offset != jumps.back().first) return false; // Unreachable code
161 112 : bits = jumps.back().second; // Restore the number of bits we would have had left after this jump
162 112 : jumps.pop_back();
163 112 : prevopcode = Instruction::JUMP;
164 : }
165 420 : } else if (opcode == Instruction::JUMP) {
166 112 : uint32_t jump = DecodeJump(pos, endpos);
167 112 : if (jump == INVALID) return false; // Jump offset straddles EOF
168 112 : if (int64_t{jump} > int64_t{endpos - pos}) return false; // Jump out of range
169 112 : if (bits == 0) return false; // Consuming bits past the end of the input
170 112 : --bits;
171 112 : uint32_t jump_offset = pos - begin + jump;
172 112 : if (!jumps.empty() && jump_offset >= jumps.back().first) return false; // Intersecting jumps
173 112 : jumps.emplace_back(jump_offset, bits);
174 112 : prevopcode = Instruction::JUMP;
175 308 : } else if (opcode == Instruction::MATCH) {
176 196 : uint32_t match = DecodeMatch(pos, endpos);
177 196 : if (match == INVALID) return false; // Match bits straddle EOF
178 196 : int matchlen = std::bit_width(match) - 1;
179 196 : if (prevopcode != Instruction::MATCH) had_incomplete_match = false;
180 196 : if (matchlen < 8 && had_incomplete_match) return false; // Within a sequence of matches only at most one should be incomplete
181 196 : had_incomplete_match = (matchlen < 8);
182 196 : if (bits < matchlen) return false; // Consuming bits past the end of the input
183 196 : bits -= matchlen;
184 196 : prevopcode = Instruction::MATCH;
185 196 : } 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 2 : return false; // Reached EOF without RETURN instruction
195 16 : }
196 :
197 16 : std::vector<bool> DecodeAsmap(fs::path path)
198 : {
199 16 : std::vector<bool> bits;
200 16 : FILE *filestr = fsbridge::fopen(path, "rb");
201 16 : AutoFile file{filestr};
202 16 : if (file.IsNull()) {
203 0 : LogPrintf("Failed to open asmap file from disk\n");
204 0 : return bits;
205 : }
206 16 : fseek(filestr, 0, SEEK_END);
207 16 : int length = ftell(filestr);
208 16 : LogPrintf("Opened asmap file %s (%d bytes) from disk\n", fs::quoted(fs::PathToString(path)), length);
209 16 : fseek(filestr, 0, SEEK_SET);
210 : uint8_t cur_byte;
211 842 : for (int i = 0; i < length; ++i) {
212 826 : file >> cur_byte;
213 7434 : for (int bit = 0; bit < 8; ++bit) {
214 6608 : bits.push_back((cur_byte >> bit) & 1);
215 6608 : }
216 826 : }
217 16 : if (!SanityCheckASMap(bits, 128)) {
218 2 : LogPrintf("Sanity check of asmap file %s failed\n", fs::quoted(fs::PathToString(path)));
219 2 : return {};
220 : }
221 14 : return bits;
222 16 : }
223 :
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