[release-branch.go1.5] doc: add Go Security Policy document

Bring in the text from the proposal (with minor edits):
https://github.com/golang/proposal/blob/master/design/11502-securitypolicy.md

Fixes #11502

Change-Id: I92a987be66a0df60c1fad6c6c79f89bd8e9c12a8
Reviewed-on: https://go-review.googlesource.com/13955Reviewed-by: Jason Buberel <jbuberel@google.com>
Reviewed-on: https://go-review.googlesource.com/14224Reviewed-by: Andrew Gerrand <adg@golang.org>

doc/contrib.html

@@ -93,7 +93,9 @@ We pride ourselves on being meticulous; no issue is too small.
 </p>
 
 <p>
-Sensitive security-related issues should be reported to <a href="mailto:security@golang.org">security@golang.org</a>.
+Security-related issues should be reported to
+<a href="mailto:security@golang.org">security@golang.org</a>.
+See the <a href="/security">security policy</a> for more details.
 </p>
 
 <h3><a href="/doc/contribute.html">Contributing code</a></h3>

doc/security.html

+<!--{
+	"Title": "Go Security Policy",
+	"Path":  "/security",
+	"Template": true
+}-->
+
+<h2>Implementation</h2>
+
+<h3>Reporting a Security Bug</h3>
+
+<p>
+Please report to us any issues you find.
+This document explains how to do that and what to expect in return.
+</p>
+
+<p>
+All security bugs in the Go distribution should be reported by email to
+<a href="mailto:security@golang.org">security@golang.org</a>.
+This mail is delivered to a small security team.
+Your email will be acknowledged within 24 hours, and you'll receive a more
+detailed response to your email within 72 hours indicating the next steps in
+handling your report.
+If you would like, you can encrypt your report using our PGP key (listed below).
+</p>
+
+<p>
+Please use a descriptive subject line for your report email.
+After the initial reply to your report, the security team will endeavor to keep
+you informed of the progress being made towards a fix and full announcement.
+These updates will be sent at least every five days.
+In reality, this is more likely to be every 24-48 hours.
+</p>
+
+<p>
+If you have not received a reply to your email within 48 hours or you have not
+heard from the security team for the past five days please contact the Go
+security team directly:
+</p>
+
+<ul>
+<li>Primary security coordinator: <a href="mailto:adg@golang.org">Andrew Gerrand</a>  (<a href="https://drive.google.com/a/google.com/file/d/0B42ZAZN5yFufRldybEVNandRN2c/view">public key</a>).</li>
+<li>Secondary coordinator: <a href="mailto:agl@golang.org">Adam Langley</a> (<a href="https://www.imperialviolet.org/key.asc">public key</a>).</li>
+<li>If you receive no response, mail <a href="mailto:golang-dev@googlegroups.com">golang-dev@googlegroups.com</a> or use the <a href="https://groups.google.com/forum/#!forum/golang-dev">golang-dev web interface</a>.</li>
+</ul>
+
+<p>
+Please note that golang-dev is a public discussion forum.
+When escalating on this list, please do not disclose the details of the issue.
+Simply state that you're trying to reach a member of the security team.
+</p>
+
+<h3>Flagging Existing Issues as Security-related</h3>
+
+<p>
+If you believe that an <a href="https://golang.org/issue">existing issue</a>
+is security-related, we ask that you send an email to
+<a href="mailto:security@golang.org">security@golang.org</a>.
+The email should include the issue ID and a short description of why it should
+be handled according to this security policy.
+</p>
+
+<h3>Disclosure Process</h3>
+
+<p>The Go project uses the following disclosure process:</p>
+
+<ol>
+<li>Once the security report is received it is assigned a primary handler.
+This person coordinates the fix and release process.</li>
+<li>The issue is confirmed and a list of affected software is determined.</li>
+<li>Code is audited to find any potential similar problems.</li>
+<li>If it is determined, in consultation with the submitter, that a CVE-ID is
+required, the primary handler obtains one via email to
+<a href="http://oss-security.openwall.org/wiki/mailing-lists/distros">oss-distros</a>.</li>
+<li>Fixes are prepared for the current stable release and the head/master
+revision. These fixes are not yet committed to the public repository.</li>
+<li>A notification is sent to the
+<a href="https://groups.google.com/group/golang-announce">golang-announce</a>
+mailing list to give users time to prepare their systems for the update.</li>
+<li>Three working days following this notification, the fixes are applied to
+the <a href="https://go.googlesource.com/go">public repository</a> and a new
+Go release is issued.</li>
+<li>On the date that the fixes are applied, announcements are sent to
+<a href="https://groups.google.com/group/golang-announce">golang-announce</a>,
+<a href="https://groups.google.com/group/golang-dev">golang-dev</a>, and
+<a href="https://groups.google.com/group/golang-nuts">golang-nuts</a>.
+</ol>
+
+<p>
+This process can take some time, especially when coordination is required with
+maintainers of other projects. Every effort will be made to handle the bug in
+as timely a manner as possible, however it's important that we follow the
+process described above to ensure that disclosures are handled consistently.
+</p>
+
+<p>
+For security issues that include the assignment of a CVE-ID,
+the issue is listed publicly under the
+<a href="https://www.cvedetails.com/vulnerability-list/vendor_id-14185/Golang.html">"Golang" product on the CVEDetails website</a>
+as well as the
+<a href="https://web.nvd.nist.gov/view/vuln/search">National Vulnerability Disclosure site</a>.
+</p>
+
+<h3>Receiving Security Updates</h3>
+
+<p>
+The best way to receive security announcements is to subscribe to the
+<a href="https://groups.google.com/forum/#!forum/golang-announce">golang-announce</a>
+mailing list. Any messages pertaining to a security issue will be prefixed
+with <code>[security]</code>.
+</p>
+
+<h3>Comments on This Policy</h3>
+
+<p>
+If you have any suggestions to improve this policy, please send an email to
+<a href="mailto:golang-dev@golang.org">golang-dev@golang.org</a> for discussion.
+</p>
+
+<h3>PGP Key for <a href="mailto:security@golang.org">security@golang.org</a></h3>
+
+<pre>
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+Comment: GPGTools - https://gpgtools.org
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+-----END PGP PUBLIC KEY BLOCK-----
+</pre>