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-rw-r--r--src/script.cpp24
1 files changed, 23 insertions, 1 deletions
diff --git a/src/script.cpp b/src/script.cpp
index c34fbec82d..4357a9a1b3 100644
--- a/src/script.cpp
+++ b/src/script.cpp
@@ -54,12 +54,29 @@ bool CastToBool(const valtype& vch)
return false;
}
+//
+// WARNING: This does not work as expected for signed integers; the sign-bit
+// is left in place as the integer is zero-extended. The correct behavior
+// would be to move the most significant bit of the last byte during the
+// resize process. MakeSameSize() is currently only used by the disabled
+// opcodes OP_AND, OP_OR, and OP_XOR.
+//
void MakeSameSize(valtype& vch1, valtype& vch2)
{
// Lengthen the shorter one
if (vch1.size() < vch2.size())
+ // PATCH:
+ // +unsigned char msb = vch1[vch1.size()-1];
+ // +vch1[vch1.size()-1] &= 0x7f;
+ // vch1.resize(vch2.size(), 0);
+ // +vch1[vch1.size()-1] = msb;
vch1.resize(vch2.size(), 0);
if (vch2.size() < vch1.size())
+ // PATCH:
+ // +unsigned char msb = vch2[vch2.size()-1];
+ // +vch2[vch2.size()-1] &= 0x7f;
+ // vch2.resize(vch1.size(), 0);
+ // +vch2[vch2.size()-1] = msb;
vch2.resize(vch1.size(), 0);
}
@@ -663,6 +680,11 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, co
}
break;
+ //
+ // WARNING: These disabled opcodes exhibit unexpected behavior
+ // when used on signed integers due to a bug in MakeSameSize()
+ // [see definition of MakeSameSize() above].
+ //
case OP_AND:
case OP_OR:
case OP_XOR:
@@ -672,7 +694,7 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, co
return false;
valtype& vch1 = stacktop(-2);
valtype& vch2 = stacktop(-1);
- MakeSameSize(vch1, vch2);
+ MakeSameSize(vch1, vch2); // <-- NOT SAFE FOR SIGNED VALUES
if (opcode == OP_AND)
{
for (unsigned int i = 0; i < vch1.size(); i++)