Set up an admin monitor in case of browser-based download.

Also moving this switch to security settings.

core/src/main/java/jenkins/model/DownloadSettings.java

@@ -25,6 +25,7 @@
 package jenkins.model;
 
 import hudson.Extension;
+import hudson.model.AdministrativeMonitor;
 import hudson.model.AsyncPeriodicWork;
 import hudson.model.DownloadService;
 import hudson.model.TaskListener;
@@ -69,6 +70,10 @@ import org.kohsuke.stapler.StaplerRequest;
         save();
     }
 
+    @Override public GlobalConfigurationCategory getCategory() {
+        return GlobalConfigurationCategory.get(GlobalConfigurationCategory.Security.class);
+    }
+
     @Extension public static final class DailyCheck extends AsyncPeriodicWork {
 
         public DailyCheck() {
@@ -91,4 +96,12 @@ import org.kohsuke.stapler.StaplerRequest;
 
     }
 
+    @Extension public static final class Warning extends AdministrativeMonitor {
+
+        @Override public boolean isActivated() {
+            return DownloadSettings.get().isUseBrowser();
+        }
+
+    }
+
 }

core/src/main/resources/jenkins/model/DownloadSettings/Warning/message.jelly

+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+The MIT License
+
+Copyright 2015 Jesse Glick.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+-->
+
+<?jelly escape-by-default='true'?>
+<j:jelly xmlns:j="jelly:core" xmlns:f="/lib/form">
+    <div class="warning">
+        <form method="post" action="${rootURL}/${it.url}/disable">
+            <j:out value="${%blurb(rootURL)}"/>
+            <f:submit value="${%Dismiss}"/>
+        </form>
+    </div>
+</j:jelly>

core/src/main/resources/jenkins/model/DownloadSettings/Warning/message.properties

+# The MIT License
+#
+# Copyright 2015 Jesse Glick.
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+blurb=\
+    You currently are using browser-based download to retrieve metadata for Jenkins plugins and tools. \
+    This has reliability issues and is not considered fully secure. \
+    Consider <a href="{0}/configureSecurity">switching to server-based download</a>.

core/src/main/resources/jenkins/model/DownloadSettings/config.groovy

@@ -2,8 +2,7 @@ package jenkins.security.DownloadSettings
 
 def f = namespace(lib.FormTagLib)
 
-f.section(title: _("Download Preferences")) {
-    f.entry(title: _("Use Browser"), field: "useBrowser") {
-        f.checkbox()
-    }
+// TODO avoid indentation somehow
+f.entry(field: "useBrowser") {
+    f.checkbox(title: _("Use browser for metadata download"))
 }

core/src/main/resources/jenkins/model/DownloadSettings/help-useBrowser.html

-<div>
+<p>
     Check to force the user’s browser to download metadata rather than Jenkins itself doing it.
     Actual file downloads (plugins, tools) will still happen from Jenkins itself,
     but this can be used to at least <em>see</em> new metadata when Jenkins cannot access the Internet
     (but your own browser can, perhaps using some special proxy that Jenkins is not configured to use).
-</div>
+</p>
+<p>
+    Use of browser mode is discouraged.
+    It is not very secure, as malicious users could submit signed but obsolete information, causing denials of service or build errors.
+</p>