http2: add http2.noStore headers

Add support headers that use `NGHTTP2_NV_FLAG_NO_INDEX` to avoid
being indexed by the HTTP2 header compression.

doc/api/http2.md

@@ -1595,6 +1595,15 @@ added: REPLACEME
 Returns a [Settings Object][] containing the deserialized settings from the
 given `Buffer` as generated by `http2.getPackedSettings()`.
 
+### http2.noStore
+<!-- YAML
+added: REPLACEME
+-->
+
+* {symbol}
+
+See [Headers Object][].
+
 ### Headers Object
 
 Headers are represented as own-properties on JavaScript objects. The property
@@ -1628,6 +1637,24 @@ server.on('stream', (stream, headers) => {
 });
 ```
 
+The HTTP/2 header compression mechanism allows the sender to decide, on a
+header-by-header basis, whether or not the header should be stored in the
+stateful header compression table. To leverage this feature, the `http2.noStore`
+symbol key on the `headers` object can be used to provide more headers in the
+same format:
+
+```
+const headers = {
+  ':status': '200',
+  'content-type': 'text-plain',
+  [http2.noStore]: {
+    'ABC': ['has', 'more', 'than', 'one', 'value']
+  }
+};
+
+stream.respond(headers);
+```
+
 ### Settings Object
 
 The `http2.getDefaultSettings()`, `http2.getPackedSettings()`,

lib/http2.js

@@ -13,7 +13,8 @@ const {
   getUnpackedSettings,
   createServer,
   createSecureServer,
-  connect
+  connect,
+  noStore
 } = require('internal/http2/core');
 
 module.exports = {
@@ -23,5 +24,6 @@ module.exports = {
   getUnpackedSettings,
   createServer,
   createSecureServer,
-  connect
+  connect,
+  noStore
 };

lib/internal/errors.js

@@ -166,6 +166,8 @@ E('ERR_HTTP2_PAYLOAD_FORBIDDEN',
   (code) => `Responses with ${code} status must not have a payload`);
 E('ERR_HTTP2_OUT_OF_STREAMS',
   'No stream ID is available because maximum stream ID has been reached');
+E('ERR_HTTP2_PSEUDOHEADER_INVALID_FLAGS',
+  (name) => `HTTP/2 pseudo-header "${name}" cannot be used with http2.noStore`);
 E('ERR_HTTP2_PSEUDOHEADER_NOT_ALLOWED', 'Cannot set HTTP/2 pseudo-headers');
 E('ERR_HTTP2_PUSH_DISABLED', 'HTTP/2 client has disabled push streams');
 E('ERR_HTTP2_SEND_FILE', 'Only regular files can be sent');

lib/internal/http2/core.js

@@ -33,6 +33,7 @@ const {
   getStreamState,
   isPayloadMeaningless,
   mapToHeaders,
+  noStore,
   NghttpError,
   toHeaderObject,
   updateOptionsBuffer,
@@ -2546,7 +2547,8 @@ module.exports = {
   getUnpackedSettings,
   createServer,
   createSecureServer,
-  connect
+  connect,
+  noStore
 };
 
 /* eslint-enable no-use-before-define */

lib/internal/http2/util.js

@@ -48,9 +48,16 @@ const {
 
   HTTP2_METHOD_DELETE,
   HTTP2_METHOD_GET,
-  HTTP2_METHOD_HEAD
+  HTTP2_METHOD_HEAD,
+
+  NGHTTP2_NV_FLAG_NONE,
+  NGHTTP2_NV_FLAG_NO_INDEX
 } = binding.constants;
 
+const HEADER_DEFAULT = String.fromCharCode(NGHTTP2_NV_FLAG_NONE);
+const HEADER_NO_STORE = String.fromCharCode(NGHTTP2_NV_FLAG_NO_INDEX);
+const noStore = Symbol('http2.noStore');
+
 // This set is defined strictly by the HTTP/2 specification. Only
 // :-prefixed headers defined by that specification may be added to
 // this set.
@@ -374,11 +381,12 @@ function assertValidPseudoHeaderTrailer(key) {
 }
 
 function mapToHeaders(map,
-                      assertValuePseudoHeader = assertValidPseudoHeader) {
+                      assertValuePseudoHeader = assertValidPseudoHeader,
+                      flag = HEADER_DEFAULT,
+                      singles = new Set()) {
   let ret = '';
   let count = 0;
   const keys = Object.keys(map);
-  const singles = new Set();
   for (var i = 0; i < keys.length; i++) {
     let key = keys[i];
     let value = map[key];
@@ -403,7 +411,9 @@ function mapToHeaders(map,
       const err = assertValuePseudoHeader(key);
       if (err !== undefined)
         return err;
-      ret = `${key}\0${String(value)}\0${ret}`;
+      // The first byte is always 0, passing NGHTTP2_NV_FLAG_NO_INDEX
+      // does not make sense for pseudo-headers.
+      ret = `\0${key}\0${String(value)}\0${ret}`;
       count++;
     } else {
       if (kSingleValueHeaders.has(key)) {
@@ -417,17 +427,30 @@ function mapToHeaders(map,
       if (isArray) {
         for (var k = 0; k < value.length; k++) {
           val = String(value[k]);
-          ret += `${key}\0${val}\0`;
+          ret += `${flag}${key}\0${val}\0`;
         }
         count += value.length;
       } else {
         val = String(value);
-        ret += `${key}\0${val}\0`;
+        ret += `${flag}${key}\0${val}\0`;
         count++;
       }
     }
   }
 
+  const noStoreMap = map[noStore];
+  if (noStoreMap !== undefined) {
+    const info = mapToHeaders(
+        noStoreMap,
+        (key) => new errors.Error('ERR_HTTP2_PSEUDOHEADER_INVALID_FLAGS', key),
+        HEADER_NO_STORE,
+        singles);
+    if (!Array.isArray(info))
+      return info;
+    ret += info[0];
+    count += info[1];
+  }
+
   return [ret, count];
 }
 
@@ -510,6 +533,7 @@ module.exports = {
   isPayloadMeaningless,
   mapToHeaders,
   NghttpError,
+  noStore,
   toHeaderObject,
   updateOptionsBuffer,
   updateSettingsBuffer

src/node_http2.cc

@@ -1126,7 +1126,7 @@ Headers::Headers(Isolate* isolate,
       return;
     }
 
-    nva[n].flags = NGHTTP2_NV_FLAG_NONE;
+    nva[n].flags = *(p++);
     nva[n].name = reinterpret_cast<uint8_t*>(p);
     nva[n].namelen = strlen(p);
     p += nva[n].namelen + 1;

test/parallel/test-http2-nostore-header.js

@@ -0,0 +1,38 @@
+// Flags: --expose-http2
+'use strict';
+
+const common = require('../common');
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+const assert = require('assert');
+const http2 = require('http2');
+
+const server = http2.createServer();
+
+const src = {
+  'regular-header': 'foo',
+  [http2.noStore]: {
+    'unindexed-header': 'A'.repeat(1000)
+  }
+};
+
+function checkHeaders(headers) {
+  assert.strictEqual(headers['regular-header'], 'foo');
+  assert.strictEqual(headers['unindexed-header'], 'A'.repeat(1000));
+}
+
+server.on('stream', common.mustCall((stream, headers) => {
+  checkHeaders(headers);
+  stream.respond(src);
+  stream.end();
+}));
+
+server.listen(0, common.mustCall(() => {
+  const client = http2.connect(`http://localhost:${server.address().port}`);
+  const req = client.request(src);
+  req.on('response', common.mustCall(checkHeaders));
+  req.on('streamClosed', common.mustCall(() => {
+    server.close();
+    client.destroy();
+  }));
+}));