asmap.cpp raw
1 // Copyright (c) 2019-2022 The Limenka 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 <logging.h>
9 #include <serialize.h>
10 #include <streams.h>
11 #include <util/fs.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 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 = std::bit_width(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 = std::bit_width(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 file.seek(0, SEEK_END);
207 int length = file.tell();
208 LogPrintf("Opened asmap file %s (%d bytes) from disk\n", fs::quoted(fs::PathToString(path)), length);
209 file.seek(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
224