http: edit _storeHeader to check for Trailer header

lib/_http_outgoing.js

@@ -33,6 +33,7 @@ const checkInvalidHeaderChar = common._checkInvalidHeaderChar;
 const outHeadersKey = require('internal/http').outHeadersKey;
 const async_id_symbol = process.binding('async_wrap').async_id_symbol;
 const nextTick = require('internal/process/next_tick').nextTick;
+const errors = require('internal/errors');
 
 const CRLF = common.CRLF;
 const debug = common.debug;
@@ -424,6 +425,14 @@ function _storeHeader(firstLine, headers) {
     }
   }
 
+  // Test non-chunked message does not have trailer header set,
+  // message will be terminated by the first empty line after the
+  // header fields, regardless of the header fields present in the
+  // message, and thus cannot contain a message body or 'trailers'.
+  if (this.chunkedEncoding !== true && state.trailer) {
+    throw new errors.Error('ERR_HTTP_TRAILER_INVALID');
+  }
+
   this._header = state.header + CRLF;
   this._headerSent = false;
 

lib/internal/errors.js

@@ -113,6 +113,8 @@ E('ERR_IPC_SYNC_FORK', 'IPC cannot be used with synchronous forks');
 E('ERR_MISSING_ARGS', missingArgs);
 E('ERR_STDERR_CLOSE', 'process.stderr cannot be closed');
 E('ERR_STDOUT_CLOSE', 'process.stdout cannot be closed');
+E('ERR_HTTP_TRAILER_INVALID',
+  'Trailers are invalid with this transfer encoding');
 E('ERR_UNKNOWN_BUILTIN_MODULE', (id) => `No such built-in module: ${id}`);
 E('ERR_UNKNOWN_SIGNAL', (signal) => `Unknown signal: ${signal}`);
 E('ERR_UNKNOWN_STDIN_TYPE', 'Unknown stdin file type');

test/parallel/test-http-server-de-chunked-trailer.js

@@ -0,0 +1,33 @@
+'use strict';
+const common = require('../common');
+
+// This test ensures that a Trailer header is set only when a chunked transfer
+// encoding is used.
+
+const assert = require('assert');
+const http = require('http');
+
+const server = http.createServer(common.mustCall(function(req, res) {
+  res.setHeader('Trailer', 'baz');
+  const trailerInvalidErr = {
+    code: 'ERR_HTTP_TRAILER_INVALID',
+    message: 'Trailers are invalid with this transfer encoding',
+    type: Error
+  };
+  assert.throws(() => res.writeHead(200, {'Content-Length': '2'}),
+                common.expectsError(trailerInvalidErr));
+  res.removeHeader('Trailer');
+  res.end('ok');
+}));
+server.listen(0, common.mustCall(() => {
+  http.get({ port: server.address().port }, common.mustCall((res) => {
+    assert.strictEqual(res.statusCode, 200);
+    let buf = '';
+    res.on('data', (chunk) => {
+      buf += chunk;
+    }).on('end', common.mustCall(() => {
+      assert.strictEqual(buf, 'ok');
+    }));
+    server.close();
+  }));
+}));