Check that a signature covers every cookie field

The only tampering tried was a flipped signature, a field swapped for
another and the binding, so a payload that left out the expiry, the
salt or the value still passed, and a captured session could have been
extended for ever.

1 file changed, 20 insertions, 0 deletions

diff --git a/tests/extensions/test-auth.lua b/tests/extensions/test-auth.luaindex 5faba1c..2234fac 100644--- a/tests/extensions/test-auth.lua+++ b/tests/extensions/test-auth.lua@@ -265,6 +265,26 @@ h.equals("a tampered signature is rejected", validate_value("username", flipped)  h.equals("a value signed for one field does not serve another", validate_value("redirect", cookie), nil) +-- The signature covers every field beside it, so none can be changed under+-- it. A later expiry would let a captured session run for ever.+local function with_field(token, index, replacement)+	local fields = {}+	for part in token:gmatch("[^|]+") do+		fields[#fields + 1] = part+	end+	fields[index] = replacement+	return table.concat(fields, "|")+end+h.equals("a cookie rebuilt unchanged still verifies",+	validate_value("username", with_field(cookie, 1, "username")), "alice")+h.equals("a later expiry under the same signature does not",+	validate_value("username", with_field(cookie, 3, tostring(now + 7200))), nil)+h.equals("nor does another salt", validate_value("username", with_field(cookie, 4, string.rep("0", 32))), nil)+h.equals("nor another name", validate_value("username", with_field(cookie, 2, "mallory")), nil)+local way_out = secure_value("redirect", "/repo/", 0)+h.equals("nor a way back pointed at another page",+	validate_value("redirect", with_field(way_out, 2, url_encode("/other/"))), nil)+ h.equals("no cookie does not verify", validate_value("username", nil), nil) h.equals("a tiny cookie does not verify", validate_value("username", "ab"), nil) h.equals("a leading separator does not verify", validate_value("username", "|x|1|s|sig"), nil)
diff --git a/tests/extensions/test-auth.lua b/tests/extensions/test-auth.lua
index 5faba1c..2234fac 100644
--- a/tests/extensions/test-auth.lua
+++ b/tests/extensions/test-auth.lua
@@ -265,6 +265,26 @@ h.equals("a tampered signature is rejected", validate_value("username", flipped)
 
 h.equals("a value signed for one field does not serve another", validate_value("redirect", cookie), nil)
 
+-- The signature covers every field beside it, so none can be changed under
+-- it. A later expiry would let a captured session run for ever.
+local function with_field(token, index, replacement)
+	local fields = {}
+	for part in token:gmatch("[^|]+") do
+		fields[#fields + 1] = part
+	end
+	fields[index] = replacement
+	return table.concat(fields, "|")
+end
+h.equals("a cookie rebuilt unchanged still verifies",
+	validate_value("username", with_field(cookie, 1, "username")), "alice")
+h.equals("a later expiry under the same signature does not",
+	validate_value("username", with_field(cookie, 3, tostring(now + 7200))), nil)
+h.equals("nor does another salt", validate_value("username", with_field(cookie, 4, string.rep("0", 32))), nil)
+h.equals("nor another name", validate_value("username", with_field(cookie, 2, "mallory")), nil)
+local way_out = secure_value("redirect", "/repo/", 0)
+h.equals("nor a way back pointed at another page",
+	validate_value("redirect", with_field(way_out, 2, url_encode("/other/"))), nil)
+
 h.equals("no cookie does not verify", validate_value("username", nil), nil)
 h.equals("a tiny cookie does not verify", validate_value("username", "ab"), nil)
 h.equals("a leading separator does not verify", validate_value("username", "|x|1|s|sig"), nil)