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Make asmap Interpret tolerant of malicious map data

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This commit is contained in:
Pieter Wuille 2020-01-30 16:46:21 -08:00
parent 38c2395d7a
commit c86bc14408
1 changed files with 24 additions and 18 deletions
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42
src/util/asmap.cpp
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@ -8,13 +8,14 @@
namespace { namespace {
uint32_t DecodeBits(std::vector<bool>::const_iterator& bitpos, uint8_t minval, const std::vector<uint8_t> &bit_sizes) 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)
{ {
uint32_t val = minval; uint32_t val = minval;
bool bit; bool bit;
for (std::vector<uint8_t>::const_iterator bit_sizes_it = bit_sizes.begin(); for (std::vector<uint8_t>::const_iterator bit_sizes_it = bit_sizes.begin();
bit_sizes_it != bit_sizes.end(); ++bit_sizes_it) { bit_sizes_it != bit_sizes.end(); ++bit_sizes_it) {
if (bit_sizes_it + 1 != bit_sizes.end()) { if (bit_sizes_it + 1 != bit_sizes.end()) {
if (bitpos == endpos) break;
bit = *bitpos; bit = *bitpos;
bitpos++; bitpos++;
} else { } else {
@ -24,6 +25,7 @@ uint32_t DecodeBits(std::vector<bool>::const_iterator& bitpos, uint8_t minval, c
val += (1 << *bit_sizes_it); val += (1 << *bit_sizes_it);
} else { } else {
for (int b = 0; b < *bit_sizes_it; b++) { for (int b = 0; b < *bit_sizes_it; b++) {
if (bitpos == endpos) break;
bit = *bitpos; bit = *bitpos;
bitpos++; bitpos++;
val += bit << (*bit_sizes_it - 1 - b); val += bit << (*bit_sizes_it - 1 - b);
@ -35,29 +37,29 @@ uint32_t DecodeBits(std::vector<bool>::const_iterator& bitpos, uint8_t minval, c
} }
const std::vector<uint8_t> TYPE_BIT_SIZES{0, 0, 1}; const std::vector<uint8_t> TYPE_BIT_SIZES{0, 0, 1};
uint32_t DecodeType(std::vector<bool>::const_iterator& bitpos) uint32_t DecodeType(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
{ {
return DecodeBits(bitpos, 0, TYPE_BIT_SIZES); return DecodeBits(bitpos, endpos, 0, TYPE_BIT_SIZES);
} }
const std::vector<uint8_t> ASN_BIT_SIZES{15, 16, 17, 18, 19, 20, 21, 22, 23, 24}; const std::vector<uint8_t> ASN_BIT_SIZES{15, 16, 17, 18, 19, 20, 21, 22, 23, 24};
uint32_t DecodeASN(std::vector<bool>::const_iterator& bitpos) uint32_t DecodeASN(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
{ {
return DecodeBits(bitpos, 1, ASN_BIT_SIZES); return DecodeBits(bitpos, endpos, 1, ASN_BIT_SIZES);
} }
const std::vector<uint8_t> MATCH_BIT_SIZES{1, 2, 3, 4, 5, 6, 7, 8}; const std::vector<uint8_t> MATCH_BIT_SIZES{1, 2, 3, 4, 5, 6, 7, 8};
uint32_t DecodeMatch(std::vector<bool>::const_iterator& bitpos) uint32_t DecodeMatch(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
{ {
return DecodeBits(bitpos, 2, MATCH_BIT_SIZES); return DecodeBits(bitpos, endpos, 2, MATCH_BIT_SIZES);
} }
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}; 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};
uint32_t DecodeJump(std::vector<bool>::const_iterator& bitpos) uint32_t DecodeJump(std::vector<bool>::const_iterator& bitpos, const std::vector<bool>::const_iterator& endpos)
{ {
return DecodeBits(bitpos, 17, JUMP_BIT_SIZES); return DecodeBits(bitpos, endpos, 17, JUMP_BIT_SIZES);
} }
} }
@ -65,33 +67,37 @@ uint32_t DecodeJump(std::vector<bool>::const_iterator& bitpos)
uint32_t Interpret(const std::vector<bool> &asmap, const std::vector<bool> &ip) uint32_t Interpret(const std::vector<bool> &asmap, const std::vector<bool> &ip)
{ {
std::vector<bool>::const_iterator pos = asmap.begin(); std::vector<bool>::const_iterator pos = asmap.begin();
const std::vector<bool>::const_iterator endpos = asmap.end();
uint8_t bits = ip.size(); uint8_t bits = ip.size();
uint8_t default_asn = 0; uint32_t default_asn = 0;
uint32_t opcode, jump, match, matchlen; uint32_t opcode, jump, match, matchlen;
while (1) { while (pos != endpos) {
assert(pos != asmap.end()); opcode = DecodeType(pos, endpos);
opcode = DecodeType(pos);
if (opcode == 0) { if (opcode == 0) {
return DecodeASN(pos); return DecodeASN(pos, endpos);
} else if (opcode == 1) { } else if (opcode == 1) {
jump = DecodeJump(pos); jump = DecodeJump(pos, endpos);
if (bits == 0) break;
if (ip[ip.size() - bits]) { if (ip[ip.size() - bits]) {
if (jump >= endpos - pos) break;
pos += jump; pos += jump;
} }
bits--; bits--;
} else if (opcode == 2) { } else if (opcode == 2) {
match = DecodeMatch(pos); match = DecodeMatch(pos, endpos);
matchlen = CountBits(match) - 1; matchlen = CountBits(match) - 1;
for (uint32_t bit = 0; bit < matchlen; bit++) { for (uint32_t bit = 0; bit < matchlen; bit++) {
if (bits == 0) break;
if ((ip[ip.size() - bits]) != ((match >> (matchlen - 1 - bit)) & 1)) { if ((ip[ip.size() - bits]) != ((match >> (matchlen - 1 - bit)) & 1)) {
return default_asn; return default_asn;
} }
bits--; bits--;
} }
} else if (opcode == 3) { } else if (opcode == 3) {
default_asn = DecodeASN(pos); default_asn = DecodeASN(pos, endpos);
} else { } else {
assert(0); break;
} }
} }
return 0; // 0 is not a valid ASN
} }