Sec-CH-UA: Send only the major version by default.

Rather than sending a `Sec-CH-UA` header containing the full version
number by default (e.g. "Chromium 99.0.1232.12"), send only the major
version (e.g. "Chromium 99").

This does not effect the value of `UserAgent.version` obtained from
`navigator.getUserAgent()`, but only the HTTP request header.

Bug: 928669
Change-Id: I074e244a3918b0bdab4453c2f56dc737c506f732
Reviewed-on: https://chromium-review.googlesource.com/c/1475438Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Mike West <mkwst@chromium.org>
Cr-Commit-Position: refs/heads/master@{#633726}

chrome/browser/chrome_content_browser_client.cc

@@ -1063,7 +1063,8 @@ blink::UserAgentMetadata GetUserAgentMetadata() {
   blink::UserAgentMetadata metadata;
 
   metadata.brand = version_info::GetProductName();
-  metadata.version = version_info::GetVersionNumber();
+  metadata.full_version = version_info::GetVersionNumber();
+  metadata.major_version = version_info::GetMajorVersionNumber();
   metadata.platform = version_info::GetOSType();
 
   // TODO(mkwst): Poke at BuildUserAgentFromProduct to split out these pieces.

chrome/browser/chrome_content_browser_client_unittest.cc

@@ -464,7 +464,8 @@ TEST(ChromeContentBrowserClient, UserAgentMetadata) {
   auto metadata = content_browser_client.GetUserAgentMetadata();
 
   EXPECT_EQ(metadata.brand, version_info::GetProductName());
-  EXPECT_EQ(metadata.version, version_info::GetVersionNumber());
+  EXPECT_EQ(metadata.full_version, version_info::GetVersionNumber());
+  EXPECT_EQ(metadata.major_version, version_info::GetMajorVersionNumber());
   EXPECT_EQ(metadata.platform, version_info::GetOSType());
   EXPECT_EQ(metadata.architecture, "");
   EXPECT_EQ(metadata.model, "");

chrome/browser/client_hints/client_hints.cc

@@ -395,14 +395,16 @@ void ClientHints::GetAdditionalNavigationRequestClientHintsHeaders(
     // (intentionally) different than other client hints.
     //
     // https://tools.ietf.org/html/draft-west-ua-client-hints-00#section-2.4
+    std::string version =
+        web_client_hints.IsEnabled(blink::mojom::WebClientHintsType::kUA)
+            ? ua.full_version
+            : ua.major_version;
     additional_headers->SetHeader(
         blink::kClientHintsHeaderMapping[static_cast<int>(
             blink::mojom::WebClientHintsType::kUA)],
-        // TODO(mkwst): This should include only the major version if the
-        // recipient hasn't opted into the hint.
-        ua.version.empty() ? ua.brand.c_str()
-                           : base::StringPrintf("%s %s", ua.brand.c_str(),
-                                                ua.version.c_str()));
+        version.empty()
+            ? ua.brand.c_str()
+            : base::StringPrintf("%s %s", ua.brand.c_str(), version.c_str()));
 
     if (web_client_hints.IsEnabled(blink::mojom::WebClientHintsType::kUAArch)) {
       additional_headers->SetHeader(

chrome/browser/client_hints/client_hints_browsertest.cc

@@ -10,8 +10,10 @@
 #include "base/metrics/field_trial_param_associator.h"
 #include "base/run_loop.h"
 #include "base/stl_util.h"
+#include "base/strings/string_util.h"
 #include "base/test/metrics/histogram_tester.h"
 #include "build/build_config.h"
+#include "chrome/browser/chrome_content_browser_client.h"
 #include "chrome/browser/content_settings/cookie_settings_factory.h"
 #include "chrome/browser/content_settings/host_content_settings_map_factory.h"
 #include "chrome/browser/content_settings/tab_specific_content_settings.h"
@@ -398,6 +400,10 @@ class ClientHintsBrowserTest : public InProcessBrowserTest,
     return request_interceptor_->client_hints_count_seen();
   }
 
+  const std::string& main_frame_ua_observed() const {
+    return main_frame_ua_observed_;
+  }
+
   base::test::ScopedFeatureList scoped_feature_list_;
 
   std::string intercept_iframe_resource_;
@@ -477,6 +483,9 @@ class ClientHintsBrowserTest : public InProcessBrowserTest,
     }
 
     if (is_main_frame_navigation) {
+      if (request.headers.find("sec-ch-ua") != request.headers.end())
+        main_frame_ua_observed_ = request.headers.find("sec-ch-ua")->second;
+
       VerifyClientHintsReceived(expect_client_hints_on_main_frame_, request);
       if (expect_client_hints_on_main_frame_) {
         double value = 0.0;
@@ -503,6 +512,7 @@ class ClientHintsBrowserTest : public InProcessBrowserTest,
         EXPECT_EQ(980, value);
 #endif
         main_frame_viewport_width_observed_ = value;
+
         VerifyNetworkQualityClientHints(request);
       }
     }
@@ -669,6 +679,8 @@ class ClientHintsBrowserTest : public InProcessBrowserTest,
   GURL http_equiv_accept_ch_with_lifetime_;
   GURL redirect_url_;
 
+  std::string main_frame_ua_observed_;
+
   double main_frame_dpr_observed_ = -1;
   double main_frame_viewport_width_observed_ = -1;
   double main_frame_device_memory_observed_ = -1;
@@ -823,6 +835,30 @@ IN_PROC_BROWSER_TEST_P(ClientHintsBrowserTest,
   EXPECT_EQ(1u, third_party_client_hints_count_seen());
 }
 
+// Verify that we send only major version information in the `Sec-CH-UA` header
+// by default, and full version information after an opt-in.
+IN_PROC_BROWSER_TEST_P(ClientHintsBrowserTest, UserAgentVersion) {
+  const GURL gurl = GetParam() ? http_equiv_accept_ch_with_lifetime()
+                               : accept_ch_with_lifetime_url();
+
+  blink::UserAgentMetadata ua = ::GetUserAgentMetadata();
+
+  // Navigate to a page that opts-into the header: the value should end with
+  // the major version, and not contain the full version.
+  SetClientHintExpectationsOnMainFrame(false);
+  ui_test_utils::NavigateToURL(browser(), gurl);
+  EXPECT_TRUE(base::EndsWith(main_frame_ua_observed(), ua.major_version,
+                             base::CompareCase::SENSITIVE));
+  EXPECT_EQ(std::string::npos, main_frame_ua_observed().find(ua.full_version));
+
+  // Navigate again, after the opt-in: the value should end with the full
+  // version.
+  SetClientHintExpectationsOnMainFrame(true);
+  ui_test_utils::NavigateToURL(browser(), gurl);
+  EXPECT_TRUE(base::EndsWith(main_frame_ua_observed(), ua.full_version,
+                             base::CompareCase::SENSITIVE));
+}
+
 // Test that client hints are attached to third party subresources if
 // AllowClientHintsToThirdParty feature is enabled.
 IN_PROC_BROWSER_TEST_P(ClientHintsAllowThirdPartyBrowserTest,

components/version_info/version_info.cc

@@ -6,6 +6,7 @@
 
 #include "base/logging.h"
 #include "base/no_destructor.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/version.h"
 #include "build/build_config.h"
 #include "components/version_info/version_info_values.h"
@@ -24,6 +25,11 @@ std::string GetVersionNumber() {
   return PRODUCT_VERSION;
 }
 
+std::string GetMajorVersionNumber() {
+  DCHECK(version_info::GetVersion().IsValid());
+  return base::UintToString(version_info::GetVersion().components()[0]);
+}
+
 const base::Version& GetVersion() {
   static const base::NoDestructor<base::Version> version(GetVersionNumber());
   return *version;

components/version_info/version_info.h

@@ -25,6 +25,9 @@ std::string GetProductName();
 // Returns the version number, e.g. "6.0.490.1".
 std::string GetVersionNumber();
 
+// Returns the major component of the version, e.g. "6".
+std::string GetMajorVersionNumber();
+
 // Returns the result of GetVersionNumber() as a base::Version.
 const base::Version& GetVersion();
 

content/shell/BUILD.gn

@@ -26,6 +26,7 @@ if (is_android) {
 declare_args() {
   content_shell_product_name = "Content Shell"
   content_shell_version = "99.77.34.5"
+  content_shell_major_version = "99"
 }
 
 config("content_shell_lib_warnings") {
@@ -238,7 +239,10 @@ jumbo_static_library("content_shell_lib") {
     "//build/config/compiler:no_size_t_to_int_warning",
   ]
 
-  defines = [ "CONTENT_SHELL_VERSION=\"$content_shell_version\"" ]
+  defines = [
+    "CONTENT_SHELL_VERSION=\"$content_shell_version\"",
+    "CONTENT_SHELL_MAJOR_VERSION=\"$content_shell_major_version\"",
+  ]
 
   public_deps = [
     ":android_shell_descriptors",

content/shell/browser/shell_content_browser_client.cc

@@ -240,7 +240,8 @@ blink::UserAgentMetadata GetShellUserAgentMetadata() {
   blink::UserAgentMetadata metadata;
 
   metadata.brand = "content_shell";
-  metadata.version = CONTENT_SHELL_VERSION;
+  metadata.full_version = CONTENT_SHELL_VERSION;
+  metadata.major_version = CONTENT_SHELL_MAJOR_VERSION;
   metadata.platform = BuildOSCpuInfo(false);
 
   // TODO(mkwst): Split these out from BuildOSCpuInfo().

third_party/blink/common/user_agent/user_agent_mojom_traits.cc

@@ -17,9 +17,13 @@ bool StructTraits<blink::mojom::UserAgentMetadataDataView,
     return false;
   out->brand = string;
 
-  if (!data.ReadVersion(&string))
+  if (!data.ReadFullVersion(&string))
     return false;
-  out->version = string;
+  out->full_version = string;
+
+  if (!data.ReadMajorVersion(&string))
+    return false;
+  out->major_version = string;
 
   if (!data.ReadPlatform(&string))
     return false;

third_party/blink/public/common/user_agent/user_agent_metadata.h

@@ -13,7 +13,8 @@ namespace blink {
 
 struct BLINK_COMMON_EXPORT UserAgentMetadata {
   std::string brand;
-  std::string version;
+  std::string full_version;
+  std::string major_version;
   std::string platform;
   std::string architecture;
   std::string model;

third_party/blink/public/common/user_agent/user_agent_mojom_traits.h

@@ -21,8 +21,13 @@ struct BLINK_COMMON_EXPORT StructTraits<blink::mojom::UserAgentMetadataDataView,
   static const std::string& brand(const ::blink::UserAgentMetadata& data) {
     return data.brand;
   }
-  static const std::string& version(const ::blink::UserAgentMetadata& data) {
-    return data.version;
+  static const std::string& full_version(
+      const ::blink::UserAgentMetadata& data) {
+    return data.full_version;
+  }
+  static const std::string& major_version(
+      const ::blink::UserAgentMetadata& data) {
+    return data.major_version;
   }
   static const std::string& platform(const ::blink::UserAgentMetadata& data) {
     return data.platform;

third_party/blink/public/mojom/user_agent/user_agent_metadata.mojom

@@ -6,7 +6,8 @@ module blink.mojom;
 
 struct UserAgentMetadata {
   string brand;
-  string version;
+  string full_version;
+  string major_version;
   string platform;
   string architecture;
   string model;

third_party/blink/renderer/core/frame/navigator_user_agent.cc

@@ -18,7 +18,7 @@ ScriptPromise NavigatorUserAgent::getUserAgent(ScriptState* script_state) {
   blink::UserAgent* idl_metadata = blink::UserAgent::Create();
 
   idl_metadata->setBrand(String::FromUTF8(metadata.brand.data()));
-  idl_metadata->setVersion(String::FromUTF8(metadata.version.data()));
+  idl_metadata->setVersion(String::FromUTF8(metadata.full_version.data()));
   idl_metadata->setPlatform(String::FromUTF8(metadata.platform.data()));
   idl_metadata->setArchitecture(String::FromUTF8(metadata.architecture.data()));
   idl_metadata->setModel(String::FromUTF8(metadata.model.data()));

third_party/blink/renderer/core/loader/frame_fetch_context.cc

@@ -737,16 +737,14 @@ void FrameFetchContext::AddClientHintsIfNecessary(
   if (RuntimeEnabledFeatures::UserAgentClientHintEnabled()) {
     StringBuilder result;
     result.Append(ua.brand.data());
-    if (!ua.version.empty()) {
+    const std::string& version =
+        ShouldSendClientHint(mojom::WebClientHintsType::kUA, hints_preferences,
+                             enabled_hints)
+            ? ua.full_version
+            : ua.major_version;
+    if (!version.empty()) {
       result.Append(' ');
-      if (ShouldSendClientHint(mojom::WebClientHintsType::kUA,
-                               hints_preferences, enabled_hints)) {
-        result.Append(ua.version.data());
-      } else {
-        // TODO(mkwst): This should only send the major version, but we haven't
-        // piped that through yet.
-        result.Append(ua.version.data());
-      }
+      result.Append(version.data());
     }
     request.AddHTTPHeaderField(
         blink::kClientHintsHeaderMapping[static_cast<size_t>(

third_party/blink/web_tests/external/wpt/client-hints/resources/sec-ch-ua.py

+def main(request, response):
+    ua = request.headers.get('sec-ch-ua', '')
+    response.headers.set("Content-Type", "text/html")
+    response.headers.set("Accept-CH", "UA")
+    response.headers.set("Accept-CH-Lifetime", "10")
+    response.content = '''
+<script>
+  window.opener.postMessage({ header: "%s" }, "*");
+</script>
+Sec-CH-UA: %s
+''' % (ua, ua)

third_party/blink/web_tests/external/wpt/client-hints/sec-ch-ua.http.html

+<!DOCTYPE html>
+<script src=/resources/testharness.js></script>
+<script src=/resources/testharnessreport.js></script>
+<script>
+  promise_test(t => {
+    return new Promise((resolve, reject) => {
+      var w;
+      window.onmessage = e => {
+        assert_equals(e.data.header, "", "The `Sec-CH-UA` header is not delivered.");
+        w.close();
+        resolve();
+      };
+      w = window.open("./resources/sec-ch-ua.py");
+    });
+  }, "Open HTTP window: no `Sec-CH-UA` header.")
+</script>

third_party/blink/web_tests/external/wpt/client-hints/sec-ch-ua.https-expected.txt

+This is a testharness.js-based test.
+FAIL Open HTTPS window prior to opt-in: `Sec-CH-UA` header with minor version. assert_not_equals: The `Sec-CH-UA` header is delivered. got disallowed value ""
+FAIL Open HTTPS window post-opt-in: `Sec-CH-UA` header with minor version. assert_not_equals: The `Sec-CH-UA` header is delivered. got disallowed value ""
+Harness: the test ran to completion.
+

third_party/blink/web_tests/external/wpt/client-hints/sec-ch-ua.https.html

+<!DOCTYPE html>
+<head>
+<script src=/resources/testharness.js></script>
+<script src=/resources/testharnessreport.js></script>
+<script>
+  var minor = "";
+  promise_test(t => {
+    return new Promise((resolve, reject) => {
+      var w;
+      window.onmessage = e => {
+        try {
+          assert_not_equals(e.data.header, "", "The `Sec-CH-UA` header is delivered.");
+          minor = e.data.header;
+        } catch (ex) {
+          reject(ex);
+        }
+        w.close();
+        resolve();
+      };
+      w = window.open("./resources/sec-ch-ua.py");
+    });
+  }, "Open HTTPS window prior to opt-in: `Sec-CH-UA` header with minor version.")
+
+  promise_test(t => {
+    return new Promise((resolve, reject) => {
+      var w;
+      window.onmessage = e => {
+        try {
+          assert_not_equals(e.data.header, "", "The `Sec-CH-UA` header is delivered.");
+          assert_not_equals(e.data.header, minor, "The `Sec-CH-UA` header is different after the opt-in than before.");
+        } catch (ex) {
+          reject(ex);
+        }
+        w.close();
+        resolve();
+      };
+      w = window.open("./resources/sec-ch-ua.py");
+    });
+  }, "Open HTTPS window post-opt-in: `Sec-CH-UA` header with minor version.")
+</script>
+</head>