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-rw-r--r--src/util/asmap.cpp54
1 files changed, 54 insertions, 0 deletions
diff --git a/src/util/asmap.cpp b/src/util/asmap.cpp
index e428ec8138..5c3652f89b 100644
--- a/src/util/asmap.cpp
+++ b/src/util/asmap.cpp
@@ -2,6 +2,7 @@
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+#include <map>
#include <vector>
#include <assert.h>
#include <crypto/common.h>
@@ -118,3 +119,56 @@ uint32_t Interpret(const std::vector<bool> &asmap, const std::vector<bool> &ip)
// Reached EOF without RETURN, or aborted (see any of the breaks above).
return 0; // 0 is not a valid ASN
}
+
+bool SanityCheckASMap(const std::vector<bool>& asmap, int bits)
+{
+ const std::vector<bool>::const_iterator begin = asmap.begin(), endpos = asmap.end();
+ std::vector<bool>::const_iterator pos = begin;
+ std::vector<std::pair<uint32_t, int>> jumps; // All future positions we may jump to (bit offset in asmap -> bits to consume left)
+ jumps.reserve(bits);
+ while (pos != endpos) {
+ uint32_t offset = pos - begin;
+ if (!jumps.empty() && offset >= jumps.back().first) return false; // There was a jump into the middle of the previous instruction
+ Instruction opcode = DecodeType(pos, endpos);
+ if (opcode == Instruction::RETURN) {
+ uint32_t asn = DecodeASN(pos, endpos);
+ if (asn == INVALID) return false; // ASN straddles EOF
+ if (jumps.empty()) {
+ // Nothing to execute anymore
+ if (endpos - pos > 7) return false; // Excessive padding
+ while (pos != endpos) {
+ if (*pos) return false; // Nonzero padding bit
+ ++pos;
+ }
+ return true; // Sanely reached EOF
+ } else {
+ // Continue by pretending we jumped to the next instruction
+ offset = pos - begin;
+ if (offset != jumps.back().first) return false; // Unreachable code
+ bits = jumps.back().second; // Restore the number of bits we would have had left after this jump
+ jumps.pop_back();
+ }
+ } else if (opcode == Instruction::JUMP) {
+ uint32_t jump = DecodeJump(pos, endpos);
+ if (jump == INVALID) return false; // Jump offset straddles EOF
+ if (jump > endpos - pos) return false; // Jump out of range
+ if (bits == 0) return false; // Consuming bits past the end of the input
+ --bits;
+ uint32_t jump_offset = pos - begin + jump;
+ if (!jumps.empty() && jump_offset >= jumps.back().first) return false; // Intersecting jumps
+ jumps.emplace_back(jump_offset, bits);
+ } else if (opcode == Instruction::MATCH) {
+ uint32_t match = DecodeMatch(pos, endpos);
+ if (match == INVALID) return false; // Match bits straddle EOF
+ int matchlen = CountBits(match) - 1;
+ if (bits < matchlen) return false; // Consuming bits past the end of the input
+ bits -= matchlen;
+ } else if (opcode == Instruction::DEFAULT) {
+ uint32_t asn = DecodeASN(pos, endpos);
+ if (asn == INVALID) return false; // ASN straddles EOF
+ } else {
+ return false; // Instruction straddles EOF
+ }
+ }
+ return false; // Reached EOF without RETURN instruction
+}