Add JWE support

AUTHORS

@@ -36,3 +36,4 @@ reporting bugs, providing fixes, suggesting useful features or other:
 	Eduardo Gonçalves <https://github.com/Dudssource>
 	Thorsten Fleischmann <https://github.com/thorstenfleischmann>
 	Tilmann Hars <https://github.com/usysrc>
+	Chris Frodo <https://github.com/chrisFrodo>

README.md

@@ -676,6 +676,115 @@ http {
 }
 ```
 
+## Sample Configuration for Keycloak OpenID Connect authentication with encrypted tokens
+
+Sample `nginx.conf` configuration to authenticate using OpenID Connect against a Keycloak 18.0 Authorization Server.
+With this configuration, the authorization server returns encrypted tokens for each OIDC tokens.
+
+```nginx
+events {
+  worker_connections 128;
+}
+
+http {
+
+  lua_package_path '~/lua/?.lua;;';
+
+  resolver 8.8.8.8;
+
+  lua_ssl_trusted_certificate /opt/local/etc/openssl/cert.pem;
+  lua_ssl_verify_depth 5;
+
+  # cache for validation results
+  lua_shared_dict introspection 10m;
+
+  lua_package_cpath "/usr/local/include/lua/?.so;;";
+  lua_package_path "/usr/local/openresty/luajit/share/lua/?.lua;/usr/local/lib/lua/?.lua;/usr/local/share/lua/5.1/?.lua;";
+  lua_shared_dict discovery 1m;
+  lua_shared_dict jwks 1m;
+
+  server {
+  	# General settings
+        listen 443 ssl;
+        root /var/www/html;
+        resolver 127.0.0.1:5353;
+
+        # Logs settings
+        access_log /etc/nginx/log/app-access.log;
+        error_log /etc/nginx/log/app-error.log;
+
+        # SSL Settings
+        ssl_certificate /etc/nginx/keys/tls.crt;
+        ssl_certificate_key /etc/nginx/keys/tls.key;
+        ssl_verify_depth 2;
+        ssl_trusted_certificate /etc/nginx/ca/caBundle.crt;
+
+        location = /favicon.ico {
+            log_not_found off;
+        }
+
+	# Publish a statically generated JWKS to be used by the OP
+        location /public/jwks.json {
+            alias /etc/nginx/public/jwks.json;
+
+        }
+
+        location /secure {
+            access_by_lua_block {
+                local opts = {
+                    redirect_uri_path = "/secure/redirect_uri",
+                    discovery = "https://<openid-service-domain>/realms/<realm>/.well-known/openid-configuration",
+                    client_id = "<client-id>",
+                    -- Set the client to use JWS as an authentication method
+                    token_endpoint_auth_method = "private_key_jwt",
+                    client_rsa_private_key =[[
+MIIEogIBAAKCAQEAiThmpvXBYdur716D2q7fYKirKxzZIU5QrkBGDvUOwg5izcTv
+[...]
+h2JHukolz9xf6qN61QMLSd83+kwoBr2drp6xg3eGDLIkQCQLrkY=
+                    ]],
+                    client_rsa_private_key_id = "265tDmmRsigvKPz8oygR0GcNdGX_naMP2cEGXR9Ueo0",
+
+
+                    -- Encryption settings
+                    --   client_rsa_private_enc_key is the RSA private key to be used to decrypt the JWE access_token / id_token generated by OP to authenticate the lua-resty-openidc RP.
+                    --   client_rsa_private_enc_key_id is the key id to be set in the JWE header to identify which public key the OP has use to encrypt the access_token / id_token.
+                    client_rsa_private_enc_key = [[
+-----BEGIN PRIVATE KEY-----
+MIIJKgIBAAKCAgEA1jhYqRlY7WiW36fzdFo4dxkwQXQhouhDlqJSu5MRiaPpwVLn
+[...]
+5zgUDtKKOXrDePay6pcaqjLKRc2nB8ljeNpYGsrQHAiK20EckOjHJZoH+1dy0Q==
+-----END PRIVATE KEY-----
+                    ]],
+                    client_rsa_private_enc_key_id = "AAAtDmmRsigvKPz8oygR0GcNdGX_naMP2cEGXR9Ueo0",
+                    -- end encryption settings
+
+
+                    redirect_uri_scheme = "https",
+                    session_contents = {id_token=true, user=true, enc_id_token=true, access_token=true},
+                    token_signing_alg_values_expected = {"RS256"},
+                    ssl_verify = "yes",
+                    scope = "openid email profile",
+
+                    logout_path = "/secure/logout",
+                    redirect_after_logout_uri = "https://<openid-service-domain>/realms/<realm>/protocol/openid-connect/logout",
+                    redirect_after_logout_with_id_token_hint = false,
+                    post_logout_redirect_uri = "https://<website-domain>/"
+
+                }
+                local openidc = require("resty.openidc")
+                local res, err = openidc.authenticate(opts)
+                if err then
+                    ngx.status = 403
+                    ngx.say(err)
+                    ngx.exit(ngx.HTTP_FORBIDDEN)
+                end
+                ngx.req.set_header('REMOTE_USER', res.id_token.email)
+            }
+        }
+    }
+}
+```
+
 ## Logging
 
 Logging can be customized, including using custom logger and remapping OpenIDC's

lib/resty/openidc.lua

@@ -405,6 +405,7 @@ local function openidc_parse_json_response(response, ignore_body_on_success)
 
     if not res then
       err = "JSON decoding failed"
+
     end
   end
 
@@ -637,7 +638,20 @@ function openidc.call_userinfo_endpoint(opts, access_token)
   log(DEBUG, "userinfo response: ", res.body)
 
   -- parse the response from the user info endpoint
-  return openidc_parse_json_response(res)
+  local json
+  json, err = openidc_parse_json_response(res)
+
+  -- If err, try to decode as jwt
+  if not json and err then
+    local r_jwt = require("resty.jwt")
+    local jwt_obj = r_jwt:load_jwt(res.body, nil)
+    if jwt_obj.valid then
+      json = jwt_obj.payload
+      err = nil
+    end
+  end
+
+  return json, err
 end
 
 local function can_use_token_auth_method(method, opts)
@@ -959,20 +973,88 @@ end
 local function openidc_load_jwt_and_verify_crypto(opts, jwt_string, asymmetric_secret,
 symmetric_secret, expected_algs, ...)
   local r_jwt = require("resty.jwt")
-  local enc_hdr, enc_payload, enc_sign = string.match(jwt_string, '^(.+)%.(.+)%.(.*)$')
-  if enc_payload and (not enc_sign or enc_sign == "") then
-    local jwt = openidc_load_jwt_none_alg(enc_hdr, enc_payload)
+  local jwt_obj
+
+  -- Expect a JWT encoded as a JWE, extracting parts
+  local part1, part2, part3, part4, part5 = string.match(jwt_string, '^(.+)%.(.+)%.(.+)%.(.+)%.(.*)$')
+
+  -- No parts extracted, try to extract parts of a JWS encoded JWT
+  if not part1 and not part2 then
+    part1, part2, part3= string.match(jwt_string, '^(.+)%.(.+)%.(.*)$')
+    part4, part5 = nil
+  end
+
+  log(DEBUG, "part 1 : ",part1, ", part 2 : ",part2, ", part 3 : ",part3, ", part 4 : ",part4, ", part 5 : ",part5)
+  -- Determine type of JWT (simple JWT, JWS, JWE) :
+
+  -- Case : is a simple JWT
+  if part1 and not part2 and not part3  and not part4 and not part5 then
+    return nil, "token is not secured, it's a simple JWT."
+
+  -- Case : is an unsigned JWS
+  elseif part1 and part2 and (not part3 or part3 == "") and not part4 and not part5 then
+    -- part1 = JOSE Header, part2 = Payload, part3 = Signature, others are unused
+    local jwt = openidc_load_jwt_none_alg(part1, part2)
     if jwt then
       if opts.accept_none_alg then
         log(DEBUG, "accept JWT with alg \"none\" and no signature")
         return jwt
       else
         return jwt, "token uses \"none\" alg but accept_none_alg is not enabled"
       end
-    end -- otherwise the JWT is invalid and load_jwt produces an error
+    else
+      -- Return error when token look like a JWT or the token is unsigned but shouldn't (alg other than \"none\"")
+      return nil, "invalid unsigned jwt"
+    end 
+
+  -- Case : is a signed JWS
+  elseif part1 and part2 and part3 and not part4 and not part5 then
+    -- part1 = JOSE Header, part2 = Payload, part3 = Signature, others are unused
+    jwt_obj = r_jwt:load_jwt(jwt_string, nil)
+
+  -- Case : is a JWE, without or with preshared key
+  elseif (part1 and part2 and part3 and  part4 and not part5) or 
+          (part1 and part2 and part3 and  part4 and part5) then
+    -- part1 = JOSE Header, part2 = Initialization Vector, part3 = Cyphertext, part4 = Authentication Tag , others are unused
+    -- or 
+    -- part1 = JOSE Header, part2 = Pre-shared key, part3 = Initialization Vector, part4 = Cyphertext, part5 = Authentication Tag 
+    local jwe_header = cjson.decode(unb64(part1))
+    local jwe_obj = nil
+
+
+    -- Limiration imposed by lua-resty-jwt v0.2.3 :
+    --    the "alg" must be either "RSA-OAEP-256" or "DIR" (function parse_jwe in lib jwt.lua, line 256 )
+    if not jwe_header.alg then
+      return nil, "jwe_header is missing the \"alg\" parameter"
+    elseif jwe_header.alg == "RSA-OAEP-256" then
+      if not opts.client_rsa_private_enc_key then
+        return nil, "OIDC config is missing a private RSA key"
+      elseif not opts.client_rsa_private_enc_key_id then 
+        return nil, "OIDC config is missing a private RSA kid"
+      end
+
+      if jwe_header.kid == opts.client_rsa_private_enc_key_id then
+        jwe_obj = r_jwt:load_jwt(jwt_string, opts.client_rsa_private_enc_key)
+        -- Test if JWE payload exist or not
+        if jwe_obj.payload == nil and jwe_obj.internal ~= nil then
+          jwt_obj = r_jwt:load_jwt(jwe_obj.internal.json_payload, nil)
+        elseif type(jwe_obj.payload) == 'string' then
+          jwt_obj = r_jwt:load_jwt(jwe_obj.payload, nil)
+        elseif type(jwe_obj.payload) == 'table' then
+          return nil, "jwe_payload must be signed before beeing encrypted"
+        else 
+          return nil, "jwe token cannot be decrypted"
+        end
+      else
+        return nil, "jwe_header.kid not matching client_rsa_private_enc_key_id"
+      end
+    else
+      return nil, "jwe_header.alg not supported by the jwt.lua library"
+    end
+  else
+    return nil, "invalid jwt"
   end
 
-  local jwt_obj = r_jwt:load_jwt(jwt_string, nil)
   if not jwt_obj.valid then
     local reason = "invalid jwt"
     if jwt_obj.reason then
@@ -1168,6 +1250,7 @@ local function openidc_authorization_response(opts, session)
       log(ERROR, "error calling userinfo endpoint: " .. err)
     elseif user then
       if id_token.sub ~= user.sub then
+
         err = "\"sub\" claim in id_token (\"" .. (id_token.sub or "null") .. "\") is not equal to the \"sub\" claim returned from the userinfo endpoint (\"" .. (user.sub or "null") .. "\")"
         log(ERROR, err)
       else