1 files changed, 63 insertions, 0 deletions
diff --git a/regress/82-bn_prepops-null-deref.lua b/regress/82-bn_prepops-null-deref.lua
new file mode 100755
index 0000000..47757d2
--- /dev/null
+++ b/regress/82-bn_prepops-null-deref.lua
@@ -0,0 +1,63 @@
+#!/usr/bin/env lua
+--
+-- The following code could trigger a NULL dereference.
+--
+-- 	bn_prepops(lua_State *L, BIGNUM **r, BIGNUM **a, BIGNUM **b, _Bool commute) {
+-- 		...
+-- 		*b = checkbig(L, 2, &lvalue);
+-- 		...
+-- 	}
+--
+-- 	bn_sqr(lua_State *L) {
+-- 		BIGNUM *r, *a;
+--
+-- 		bn_prepops(L, &r, &a, NULL, 1);
+-- 		...
+-- 	}
+--
+-- Caught by clang static analyzer. This was introduced with a patch adding
+-- the :sqr method. This should have been caught sooner as the :sqr method
+-- couldn't have possibly ever worked--a missing or non-numeric second
+-- operand would have thrown a Lua error, and a numeric second operand
+-- triggers the NULL dereference.
+--
+require"regress".export".*"
+
+local function N(i) return bignum.new(i) end
+
+-- passing a second numeric operand triggered a NULL dereference
+local r = N(4):sqr(0)
+
+
+-- check minimal functionality of all our operators
+local tests = {
+	{ op = "add", a = 1, b = 1, r = 2 },
+	{ op = "sub", a = 2, b = 1, r = 1 },
+	{ op = "mul", a = 2, b = 2, r = 4 },
+	{ op = "idiv", a = 4, b = 2, r = 2 },
+	{ op = "mod", a = 4, b = 2, r = 0 },
+	{ op = "exp", a = 2, b = 2, r = 4 },
+	{ op = "sqr", a = 4, b = nil, r = 16 },
+	{ op = "gcd", a = 47, b = 3, r = 1 },
+}
+
+local function tdescr(t)
+	return string.format("%s(%s, %s)", t.op, tostring(t.a), tostring(t.b))
+end
+
+for i,t in ipairs(tests) do
+	local a = N(t.a)
+	local op = a[t.op]
+	local ok, r
+
+	if t.b then
+		ok, r = pcall(op, a, t.b)
+	else
+		ok, r = pcall(op, a)
+	end
+
+	check(ok, "failed test #%d (%s) (%s)", i, tdescr(t), r)
+	check(N(r) == N(t.r), "failed test #%d (%s) (expected %s, got %s)", i, tdescr(t), tostring(t.r), tostring(r))
+end
+
+say"OK"