add a new option that allows caches to be segregated

see #399

Signed-off-by: Stefan Bodewig <stefan.bodewig@innoq.com>

ChangeLog

@@ -2,10 +2,13 @@
 - if lifecyle handlers return truthy values they cause the operation
   they are handlers of to fail; see #384; thanks to @arcivanov
 
+- added opts.cache_segment as option to shard the cache used by token
+  introspection or JWT verification; see #399
+
 09/22/2021
 - made jwt_verify() and bearer_jwt_verify() use a separate cache named
   "jwt_verification" and introduced opts.jwt_verification_cache_ignore
-  to disable caching completely
+  to disable caching completely; see #399
 
 12/05/2020
 - fixed a session leak in access_token() and for a very unlikely

README.md

@@ -299,6 +299,16 @@ local res, err, target, session = require("resty.openidc").authenticate(opts)
 session:close()
 ```
 
+## Caching of Introspection and JWT Verification Results
+
+Note the `jwt_verification` and `introspection` caches are shared
+between all configured locations. If you are using locations with
+different `opts` configuration the shared cache may allow a token that
+is valid for only one location to be accepted by another if it is read
+from the cache. In order to avoid cache confusion it is recommended to
+set `opts.cache_segment` to unique strings for each set of related
+locations.
+
 ## Sample Configuration for OAuth 2.0 JWT Token Validation
 
 Sample `nginx.conf` configuration for verifying Bearer JWT Access Tokens against a pre-configured secret/key.
@@ -379,6 +389,10 @@ lAc5Csj0o5Q+oEhPUAVBIF07m4rd0OvAVPOCQ2NJhQSL1oWASbf+fg==
              -- It may be necessary to force verification for a bearer token and ignore the existing cached
              -- verification results. If so you need to set set the jwt_verification_cache_ignore option to true.
              -- jwt_verification_cache_ignore = true
+
+             -- optional name of a cache-segment if you need separate
+             -- caches for differently configured locations
+             -- cache_segment = 'api'
           }
 
           -- call bearer_jwt_verify for OAuth 2.0 JWT validation
@@ -447,6 +461,10 @@ http {
              -- Defaults to "exp" - Controls the TTL of the introspection cache
              -- https://tools.ietf.org/html/rfc7662#section-2.2
              -- introspection_expiry_claim = "exp"
+
+             -- optional name of a cache-segment if you need separate
+             -- caches for differently configured locations
+             -- cache_segment = 'api'
           }
 
           -- call introspect for OAuth 2.0 Bearer Access Token validation
@@ -547,6 +565,10 @@ http {
              -- It may be necessary to force an introspection call for an access_token and ignore the existing cached
              -- introspection results. If so you need to set set the introspection_cache_ignore option to true.
              -- introspection_cache_ignore = true
+
+             -- optional name of a cache-segment if you need separate
+             -- caches for differently configured locations
+             -- cache_segment = 'api'
           }
 
           -- call introspect for OAuth 2.0 Bearer Access Token validation

lib/resty/openidc.lua

@@ -1629,7 +1629,8 @@ local function get_introspection_endpoint(opts)
 end
 
 local function get_introspection_cache_prefix(opts)
-  return (get_introspection_endpoint(opts) or 'nil-endpoint') .. ','
+  return (opts.cache_segment and opts.cache_segment.gsub(',', '_') or 'DEFAULT') .. ','
+    .. (get_introspection_endpoint(opts) or 'nil-endpoint') .. ','
     .. (opts.client_id or 'no-client_id') .. ','
     .. (opts.client_secret and 'secret' or 'no-client_secret') .. ':'
 end
@@ -1738,7 +1739,8 @@ local function get_jwt_verification_cache_prefix(opts)
   for _, alg in ipairs(expected_algs) do
     signing_alg_values_expected = signing_alg_values_expected .. ',' .. alg
   end
-  return (opts.public_key or 'no-pubkey') .. ','
+  return (opts.cache_segment and opts.cache_segment.gsub(',', '_') or 'DEFAULT') .. ','
+    .. (opts.public_key or 'no-pubkey') .. ','
     .. (opts.symmetric_key or 'no-symkey') .. ','
     .. signing_alg_values_expected .. ':'
 end