fix(jwk) fix EC key x and y padding

lib/resty/openssl/auxiliary/jwk.lua

@@ -342,6 +342,36 @@ local jwk_params_required_mapping = {
   OKP = {},
 }
 
+local ec_coord_size_map = {
+  -- JWK RFC7518
+  ["P-256"] = 32,
+  ["P-384"] = 48,
+  ["P-521"] = 66, -- rounded up to the next byte
+  -- JOSE RFC8812 and others
+  prime256v1 = 32,
+  secp384r1 = 48,
+  secp521r1 = 66, -- rounded up to the next byte
+  brainpoolP256r1 = 32,
+  brainpoolP320r1 = 40,
+  brainpoolP384r1 = 48,
+  brainpoolP512r1 = 64, -- note this is 512 not 521
+  secp256k1 = 32,
+}
+-- Pad coordinates to field size with leading zeros
+local function pad_ec_coordinate(coord, crv)
+  local size = ec_coord_size_map[crv]
+  if not size then
+    return nil, "unsupported curve " .. tostring(crv)
+  end
+  if #coord < size then
+    return string.rep("\x00", size - #coord) .. coord
+  elseif #coord > size then
+    return nil, "coordinate length " .. #coord .. " is longer than expected " .. size
+  else
+    return coord
+  end
+end
+
 function _M.load_jwk_ex(txt, ptyp, properties)
   local tbl, err = json.decode(txt)
   if err then
@@ -420,7 +450,17 @@ function _M.load_jwk_ex(txt, ptyp, properties)
 
   if kty == "EC" then
     if params_t["x"] and params_t["y"] then
-      params_t["pub"] = "\x04" .. params_t["x"]:reverse() .. params_t["y"]:reverse()
+      local x = params_t["x"]:reverse()
+      local y = params_t["y"]:reverse()
+      x, err = pad_ec_coordinate(x, tbl["crv"])
+      if err then
+        return nil, "jwk:load_jwk: pad_ec_coordinate: " .. err
+      end
+      y, err = pad_ec_coordinate(y, tbl["crv"])
+      if err then
+        return nil, "jwk:load_jwk: pad_ec_coordinate: " .. err
+      end
+      params_t["pub"] = "\x04" .. x .. y
       params_t["x"], params_t["y"] = nil, nil
     end
   end

t/openssl/aux/jwk.t

@@ -167,6 +167,29 @@ OK
             ngx.say(ok)
 
             ngx.say("OK")
+
+            -- jwk with x stripped leading 0
+            local j = {
+                kty = "EC",
+                crv = "P-521",
+                x   = "1anMzz1ZLHp2t03cviM3_zMaVm7Oe02KamaLmPkx9TDuOP77mv5Jfd-_3-TTupfl4yqX8TDrD59od9AWFj2fJ64",
+                y   = "AW_R2InNCFSsGyUotGnNiiSgFBEvi7W_OcNXzGy7pcvUMHv7FpnsRO1mgwICZNuMpM6DwMq3F-NU98DM1rhxZ0nJ",
+                d   = "AQ8JctVWDJrVl1IZAhejQgTjnidDyQcp9KTYbVBZolJfAT9D_Mfbur5_581598FLD3TSlCmBJD7OjkqGR9Yw7lMT"
+            }
+            local jwk = require("cjson").encode(j)
+            local privkey = myassert(require("resty.openssl.pkey").new(jwk))
+            local privkey = myassert(require("resty.openssl.pkey").new(jwk, {
+                format = "JWK",
+            }))
+
+            local exported = myassert(privkey:tostring("private", "JWK"))
+            exported = require("cjson").decode(exported)
+
+            for k, v in pairs(j) do
+                if k ~= "kid" and v ~= exported[k] then
+                    ngx.say("JWK part changed: input: " .. k .. "=" .. v .. ", output: " .. k .. "=" .. tostring(exported[k]))
+                end
+            end
         }
     }
 --- request