Adds header mutation example (#13)

Signed-off-by: Takeshi Yoneda <[email protected]>

Author: mathetake

integration/envoy.yaml

@@ -40,6 +40,18 @@ static_resources:
                           "num_workers": 2,
                           "dirname": "/tmp/"
                         }
+                  - name: dynamic_modules/header_mutation
+                    typed_config:
+                      # https://www.envoyproxy.io/docs/envoy/latest/api-v3/extensions/dynamic_modules/v3/dynamic_modules.proto#envoy-v3-api-msg-extensions-dynamic-modules-v3-dynamicmoduleconfig
+                      "@type": type.googleapis.com/envoy.extensions.filters.http.dynamic_modules.v3.DynamicModuleFilter
+                      dynamic_module_config:
+                        name: rust_module
+                      filter_name: header_mutation
+                      filter_config: |
+                        {
+                          "request_headers": [["X-Envoy-Header", "envoy-header"], ["X-Envoy-Header2", "envoy-header2"]],
+                          "response_headers": [["Foo", "bar"], ["Foo2", "bar2"]]
+                        }
                   - name: envoy.filters.http.router
                     typed_config:
                       "@type": type.googleapis.com/envoy.extensions.filters.http.router.v3.Router

integration/main_test.go

@@ -132,6 +132,43 @@ func TestIntegration(t *testing.T) {
 		}, 30*time.Second, 1*time.Second)
 	})
 
+	t.Run("http_header_mutation", func(t *testing.T) {
+		require.Eventually(t, func() bool {
+			req, err := http.NewRequest("GET", "http://localhost:1062/headers", nil)
+			require.NoError(t, err)
+
+			resp, err := http.DefaultClient.Do(req)
+			if err != nil {
+				t.Logf("Envoy not ready yet: %v", err)
+				return false
+			}
+			defer resp.Body.Close()
+			body, err := io.ReadAll(resp.Body)
+			if err != nil {
+				t.Logf("Envoy not ready yet: %v", err)
+				return false
+			}
+
+			t.Logf("response: headers=%v, body=%s", resp.Header, string(body))
+			require.Equal(t, 200, resp.StatusCode)
+
+			// HttpBin returns a JSON object containing the request headers.
+			type httpBinHeadersBody struct {
+				Headers map[string]string `json:"headers"`
+			}
+			var headersBody httpBinHeadersBody
+			require.NoError(t, json.Unmarshal(body, &headersBody))
+
+			require.Equal(t, "envoy-header", headersBody.Headers["X-Envoy-Header"])
+			require.Equal(t, "envoy-header2", headersBody.Headers["X-Envoy-Header2"])
+
+			// We also need to check that the response headers were mutated.
+			require.Equal(t, "bar", resp.Header.Get("Foo"))
+			require.Equal(t, "bar2", resp.Header.Get("Foo2"))
+			return true
+		}, 30*time.Second, 200*time.Millisecond)
+	})
+
 	t.Run("http_random_auth", func(t *testing.T) {
 		got200 := false
 		got403 := false

rust/src/http_header_mutation.rs

@@ -0,0 +1,109 @@
+use envoy_proxy_dynamic_modules_rust_sdk::*;
+use serde::{Deserialize, Serialize};
+
+/// This implements the [`envoy_proxy_dynamic_modules_rust_sdk::HttpFilterConfig`] trait.
+///
+/// The trait corresponds to a Envoy filter chain configuration.
+#[derive(Serialize, Deserialize, Debug)]
+pub struct FilterConfig {
+    request_headers: Vec<(String, String)>,
+    response_headers: Vec<(String, String)>,
+}
+
+impl FilterConfig {
+    /// This is the constructor for the [`FilterConfig`].
+    ///
+    /// filter_config is the filter config from the Envoy config here:
+    /// https://www.envoyproxy.io/docs/envoy/latest/api-v3/extensions/dynamic_modules/v3/dynamic_modules.proto#envoy-v3-api-msg-extensions-dynamic-modules-v3-dynamicmoduleconfig
+    pub fn new(filter_config: &str) -> Option<Self> {
+        let filter_config: FilterConfig = match serde_json::from_str(filter_config) {
+            Ok(cfg) => cfg,
+            Err(err) => {
+                eprintln!("Error parsing filter config: {}", err);
+                return None;
+            }
+        };
+        Some(filter_config)
+    }
+}
+
+impl<EC: EnvoyHttpFilterConfig, EHF: EnvoyHttpFilter> HttpFilterConfig<EC, EHF> for FilterConfig {
+    /// This is called for each new HTTP filter.
+    fn new_http_filter(&mut self, _envoy: &mut EC) -> Box<dyn HttpFilter<EHF>> {
+        Box::new(Filter {
+            request_headers: self.request_headers.clone(),
+            response_headers: self.response_headers.clone(),
+        })
+    }
+}
+
+/// This implements the [`envoy_proxy_dynamic_modules_rust_sdk::HttpFilter`] trait.
+///
+/// This sets the request and response headers to the values specified in the filter config.
+pub struct Filter {
+    request_headers: Vec<(String, String)>,
+    response_headers: Vec<(String, String)>,
+}
+
+/// This implements the [`envoy_proxy_dynamic_modules_rust_sdk::HttpFilter`] trait.
+impl<EHF: EnvoyHttpFilter> HttpFilter<EHF> for Filter {
+    fn on_request_headers(
+        &mut self,
+        envoy_filter: &mut EHF,
+        _end_of_stream: bool,
+    ) -> abi::envoy_dynamic_module_type_on_http_filter_request_headers_status {
+        for (key, value) in &self.request_headers {
+            envoy_filter.set_request_header(key, value.as_bytes());
+        }
+        abi::envoy_dynamic_module_type_on_http_filter_request_headers_status::Continue
+    }
+
+    fn on_response_headers(
+        &mut self,
+        envoy_filter: &mut EHF,
+        _end_of_stream: bool,
+    ) -> abi::envoy_dynamic_module_type_on_http_filter_response_headers_status {
+        for (key, value) in &self.response_headers {
+            envoy_filter.set_response_header(key, value.as_bytes());
+        }
+        abi::envoy_dynamic_module_type_on_http_filter_response_headers_status::Continue
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    /// This demonstrates how to write a test without Envoy using a mock provided by the SDK.
+    fn test_filter() {
+        let mut envoy_filter = envoy_proxy_dynamic_modules_rust_sdk::MockEnvoyHttpFilter::new();
+        let mut filter = Filter {
+            request_headers: vec![("X-Foo".to_string(), "bar".to_string())],
+            response_headers: vec![("X-Bar".to_string(), "foo".to_string())],
+        };
+
+        envoy_filter
+            .expect_set_request_header()
+            .returning(|key, value| {
+                assert_eq!(key, "X-Foo");
+                assert_eq!(value, b"bar");
+                return true;
+            });
+        envoy_filter
+            .expect_set_response_header()
+            .returning(|key, value| {
+                assert_eq!(key, "X-Bar");
+                assert_eq!(value, b"foo");
+                return true;
+            });
+        assert_eq!(
+            filter.on_request_headers(&mut envoy_filter, false),
+            abi::envoy_dynamic_module_type_on_http_filter_request_headers_status::Continue
+        );
+        assert_eq!(
+            filter.on_response_headers(&mut envoy_filter, false),
+            abi::envoy_dynamic_module_type_on_http_filter_response_headers_status::Continue
+        );
+    }
+}

rust/src/lib.rs

@@ -1,6 +1,7 @@
 use envoy_proxy_dynamic_modules_rust_sdk::*;
 
 mod http_access_logger;
+mod http_header_mutation;
 mod http_passthrough;
 mod http_random_auth;
 mod http_zero_copy_regex_waf;
@@ -39,6 +40,8 @@ fn new_http_filter_config_fn<EC: EnvoyHttpFilterConfig, EHF: EnvoyHttpFilter>(
         "random_auth" => Some(Box::new(http_random_auth::FilterConfig::new(filter_config))),
         "zero_copy_regex_waf" => http_zero_copy_regex_waf::FilterConfig::new(filter_config)
             .map(|config| Box::new(config) as Box<dyn HttpFilterConfig<EC, EHF>>),
+        "header_mutation" => http_header_mutation::FilterConfig::new(filter_config)
+            .map(|config| Box::new(config) as Box<dyn HttpFilterConfig<EC, EHF>>),
         _ => panic!("Unknown filter name: {}", filter_name),
     }
 }