From: csagan5 <32685696+csagan5@users.noreply.github.com>
Date: Sat, 28 Apr 2018 08:30:26 +0200
Subject: Reduce HTTP headers in DoH requests to bare minimum

License: GPL-3.0-only - https://spdx.org/licenses/GPL-3.0-only.html
---
 net/base/load_flags_list.h              |  6 ++++++
 net/dns/dns_transaction.cc              |  2 +-
 net/url_request/url_request_http_job.cc | 10 +++++++---
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/net/base/load_flags_list.h b/net/base/load_flags_list.h
--- a/net/base/load_flags_list.h
+++ b/net/base/load_flags_list.h
@@ -110,3 +110,9 @@ LOAD_FLAG(CAN_USE_SHARED_DICTIONARY, 1 << 17)
 // Indicates that CAN_USE_SHARED_DICTIONARY must be disabled after a redirect to
 // another origin.
 LOAD_FLAG(DISABLE_SHARED_DICTIONARY_AFTER_CROSS_ORIGIN_REDIRECT, 1 << 18)
+
+// This load will not send Accept-Language or User-Agent headers, and not
+// advertise brotli encoding.
+// Used to comply with IETF (draft) DNS-over-HTTPS:
+// "Implementors SHOULD NOT set non-essential HTTP headers in DoH client requests."
+LOAD_FLAG(MINIMAL_HEADERS, 1 << 19)
diff --git a/net/dns/dns_transaction.cc b/net/dns/dns_transaction.cc
--- a/net/dns/dns_transaction.cc
+++ b/net/dns/dns_transaction.cc
@@ -480,7 +480,7 @@ class DnsHTTPAttempt : public DnsAttempt, public URLRequest::Delegate {
     // avoid deadlock and enable the use of preconfigured IP addresses.
     request_->SetSecureDnsPolicy(SecureDnsPolicy::kBootstrap);
     request_->SetLoadFlags(request_->load_flags() | LOAD_DISABLE_CACHE |
-                           LOAD_BYPASS_PROXY);
+                           LOAD_MINIMAL_HEADERS | LOAD_BYPASS_PROXY);
     request_->set_allow_credentials(false);
     request_->set_isolation_info(isolation_info);
   }
diff --git a/net/url_request/url_request_http_job.cc b/net/url_request/url_request_http_job.cc
--- a/net/url_request/url_request_http_job.cc
+++ b/net/url_request/url_request_http_job.cc
@@ -360,6 +360,7 @@ void URLRequestHttpJob::OnGotFirstPartySetMetadata(
   // fields in the referrer.
   GURL referrer(request_->referrer());
 
+  if (!(request_info_.load_flags & LOAD_MINIMAL_HEADERS)) {
   // Our consumer should have made sure that this is a safe referrer (e.g. via
   // URLRequestJob::ComputeReferrerForPolicy).
   if (referrer.is_valid()) {
@@ -367,11 +368,14 @@ void URLRequestHttpJob::OnGotFirstPartySetMetadata(
     request_info_.extra_headers.SetHeader(HttpRequestHeaders::kReferer,
                                           referer_value);
   }
+  }
 
+  if (!(request_info_.load_flags & LOAD_MINIMAL_HEADERS)) {
   request_info_.extra_headers.SetHeaderIfMissing(
       HttpRequestHeaders::kUserAgent,
       http_user_agent_settings_ ?
           http_user_agent_settings_->GetUserAgent() : std::string());
+  }
 
   AddExtraHeaders();
 
@@ -628,10 +632,10 @@ void URLRequestHttpJob::StartTransactionInternal() {
 void URLRequestHttpJob::AddExtraHeaders() {
   request_info_.extra_headers.SetAcceptEncodingIfMissing(
       request()->url(), request()->accepted_stream_types(),
-      request()->context()->enable_brotli(),
-      request()->context()->enable_zstd());
+      !(request_info_.load_flags & LOAD_MINIMAL_HEADERS) && request()->context()->enable_brotli(),
+      !(request_info_.load_flags & LOAD_MINIMAL_HEADERS) && request()->context()->enable_zstd());
 
-  if (http_user_agent_settings_) {
+  if (!(request_info_.load_flags & LOAD_MINIMAL_HEADERS) && http_user_agent_settings_) {
     // Only add default Accept-Language if the request didn't have it
     // specified.
     std::string accept_language =
--
2.25.1