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Guard against two DoS crashes: parser recursion depth and integer div/mod by zero #92

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Guard against two DoS crashes: parser recursion depth and integer div/mod by zero #92

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24 changes: 18 additions & 6 deletions include/minja/minja.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -499,13 +499,17 @@ class Value : public std::enable_shared_from_this<Value> {
return get<double>() * rhs.get<double>();
}
Value operator/(const Value& rhs) const {
if (is_number_integer() && rhs.is_number_integer())
return get<int64_t>() / rhs.get<int64_t>();
else
if (is_number_integer() && rhs.is_number_integer()) {
auto d = rhs.get<int64_t>();
if (d == 0) throw std::runtime_error("integer division by zero");
return get<int64_t>() / d;
} else
return get<double>() / rhs.get<double>();
}
Value operator%(const Value& rhs) const {
return get<int64_t>() % rhs.get<int64_t>();
auto d = rhs.get<int64_t>();
if (d == 0) throw std::runtime_error("modulo by zero");
return get<int64_t>() % d;
}
};

Expand Down Expand Up @@ -1371,8 +1375,8 @@ class BinaryOpExpr : public Expression {
case Op::Mul: return l * r;
case Op::Div: return l / r;
case Op::MulMul: return std::pow(l.get<double>(), r.get<double>());
case Op::DivDiv: return l.get<int64_t>() / r.get<int64_t>();
case Op::Mod: return l.get<int64_t>() % r.get<int64_t>();
case Op::DivDiv: { auto d = r.get<int64_t>(); if (d == 0) throw std::runtime_error("integer division by zero"); return l.get<int64_t>() / d; }
case Op::Mod: { auto d = r.get<int64_t>(); if (d == 0) throw std::runtime_error("modulo by zero"); return l.get<int64_t>() % d; }
case Op::Eq: return l == r;
case Op::Ne: return l != r;
case Op::Lt: return l < r;
Expand Down Expand Up @@ -1705,6 +1709,7 @@ class Parser {
std::shared_ptr<std::string> template_str;
CharIterator start, end, it;
Options options;
int expr_depth = 0;

Parser(const std::shared_ptr<std::string>& template_str, const Options & options) : template_str(template_str), options(options) {
if (!template_str) throw std::runtime_error("Template string is null");
Expand Down Expand Up @@ -1882,6 +1887,13 @@ class Parser {
}

std::shared_ptr<Expression> parseExpression(bool allow_if_expr = true) {
struct DepthGuard {
int & d;
explicit DepthGuard(int & d) : d(d) {
if (++d > 1000) throw std::runtime_error("expression nesting too deep");
}
~DepthGuard() { --d; }
} depth_guard(expr_depth);
auto left = parseLogicalOr();
if (it == end) return left;

Expand Down