Policy: rate limit headers does not send invalid value.

When the backend does not reply with limit headers, APIcast should send no limit headers at all. This change make sure that the value is not send at all. Also, make sure that the value of limit and reset is always positive or 0. THREESCALE-3795 Signed-off-by: Eloy Coto <[email protected]>
3scale · Jul 17, 2020 · c604448 · c604448
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -19,7 +19,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Added
 
 - Added upstream Mutual TLS policy [THREESCALE-672](https://issues.jboss.org/browse/THREESCALE-672) [PR #1182](https://github.com/3scale/APIcast/pull/1182)
-- Added Rate-limit headers policy [THREESCALE-3795](https://issues.jboss.org/browse/THREESCALE-3795) [PR #1166](https://github.com/3scale/APIcast/pull/1166) [PR #1197](https://github.com/3scale/APIcast/pull/1197)
+- Added Rate-limit headers policy [THREESCALE-3795](https://issues.jboss.org/browse/THREESCALE-3795) [PR #1166](https://github.com/3scale/APIcast/pull/1166) [PR #1197](https://github.com/3scale/APIcast/pull/1197) [PR #1209](https://github.com/3scale/APIcast/pull/1209)
 - Added Content-caching policy [THREESCALE-2894](https://issues.jboss.org/browse/THREESCALE-2894) [PR #1182](https://github.com/3scale/APIcast/pull/1182)
 - Added Nginx request_id variable to context [PR #1184](https://github.com/3scale/APIcast/pull/1184)
 - Added HTTP verb on url_rewriten [PR #1187](https://github.com/3scale/APIcast/pull/1187)  [THREESCALE-5259](https://issues.jboss.org/browse/THREESCALE-5259) [PR #1202](https://github.com/3scale/APIcast/pull/1202)

diff --git a/gateway/src/apicast/policy/rate_limit_headers/rate_limit_headers.lua b/gateway/src/apicast/policy/rate_limit_headers/rate_limit_headers.lua
@@ -2,6 +2,7 @@ local policy = require('apicast.policy')
 local _M = policy.new('Rate Limit Headers', 'builtin')
 
 local usage_cache = require "cache"
+local math_max = math.max
 
 local new = _M.new
 local get_phase = ngx.get_phase
@@ -55,9 +56,18 @@ local function decrement(self, usage)
     return self.cache:decrement_usage_metric(usage)
 end
 
+-- return 0 if the number is negative
+local function positive_number(number)
+  return math_max(tonumber(number), 0)
+end
+
 local function add_headers(info)
-    ngx.header[limit_header] = info.limit
-    ngx.header[remaining_header] = info.remaining
+    if info.reset <= 0 then
+      -- filter is not defined at all, so skip it
+      return nil
+    end
+    ngx.header[limit_header] = positive_number(info.limit)
+    ngx.header[remaining_header] = positive_number(info.remaining)
     ngx.header[reset_header] = info.reset
 end
 

diff --git a/t/apicast-policy-rate_limit_headers.t b/t/apicast-policy-rate_limit_headers.t
@@ -346,3 +346,60 @@ location / {
 [200, 200]
 --- no_error_log
 [error]
+
+=== TEST 7: No rate-limit information if no limits by app
+--- configuration
+{
+  "services": [
+    {
+      "id": 42,
+      "backend_version":  1,
+      "backend_authentication_type": "service_token",
+      "backend_authentication_value": "token-value",
+      "proxy": {
+        "hosts": [
+          "localhost"
+        ],
+        "api_backend": "http://test:$TEST_NGINX_SERVER_PORT/",
+        "proxy_rules": [
+          { "pattern": "/", "http_method": "GET", "metric_system_name": "hits", "delta": 1 }
+        ],
+        "policy_chain": [
+          {
+            "name": "apicast.policy.rate_limit_headers"
+          },
+          {
+            "name": "apicast",
+            "version": "builtin",
+            "configuration": {}
+          }
+        ]
+      }
+    }
+  ]
+}
+--- backend
+location /transactions/authrep.xml {
+  content_by_lua_block {
+    ngx.exit(200)
+  }
+}
+--- upstream env
+location / {
+  access_by_lua_block {
+      ngx.say("OK")
+  }
+}
+--- request
+GET /?user_key=123
+--- response_headers
+RateLimit-Limit:
+RateLimit-Remaining:
+RateLimit-Reset: 
+--- response_body env
+OK
+--- error_code: 200
+--- no_error_log
+[error]
+
+