Merge pull request #350 from ngtcp2/security

Add security policy

Author: tatsuhiro-t

SECURITY.md

@@ -0,0 +1,34 @@
+# Security Process
+
+If you find a vulnerability in our software, please report it via
+GitHub "Private vulnerability reporting" feature at
+https://github.com/ngtcp2/nghttp3/security instead of submitting
+issues on github issue page.  It is a standard practice not to
+disclose vulnerability information publicly until a fixed version is
+released, or mitigation is worked out.
+
+If we identify that the reported issue is really a vulnerability, we
+open a new security advisory draft using [GitHub security
+feature](https://github.com/ngtcp2/nghttp3/security) and discuss the
+mitigation and bug fixes there.  The fixes are committed to the
+private repository.
+
+We write the security advisory and get CVE number from GitHub
+privately.  We also discuss the disclosure date to the public.
+
+We make a new release with the fix at the same time when the
+vulnerability is disclosed to public.
+
+At least 7 days before the public disclosure date, we open a new issue
+on [nghttp3 issue tracker](https://github.com/ngtcp2/nghttp3/issues)
+which notifies that the upcoming release will have a security fix.
+The `SECURITY` label is attached to this kind of issue.  The issue is
+not opened if a vulnerability is already disclosed, and it is publicly
+known that nghttp3 is affected by that.  The issue might not be
+created if CVE only affects the latest version released very recently.
+In this case, we would like to release a fix without waiting a week to
+avoid widespread use of the version.
+
+Before few hours of new release, we merge the fixes to the master
+branch (and/or a release branch if necessary) and make a new release.
+Security advisory is disclosed on GitHub.