proof expires. The downside is that it requires server support.
If Exim is built with EXPERIMENTAL_OCSP and it was built with OpenSSL,
-then it gains a new global option: "tls_ocsp_file".
+or with GnuTLS 3.1.3 or later, then it gains a new global option:
+"tls_ocsp_file".
The file specified therein is expected to be in DER format, and contain
an OCSP proof. Exim will serve it as part of the TLS handshake. This
on each connection, so a new file will be handled transparently on the
next connection.
-Exim will check for a valid next update timestamp in the OCSP proof;
-if not present, or if the proof has expired, it will be ignored.
+Under OpenSSL Exim will check for a valid next update timestamp in the
+OCSP proof; if not present, or if the proof has expired, it will be
+ignored.
-Also, given EXPERIMENTAL_OCSP and OpenSSL, the smtp transport gains
-a "hosts_require_ocsp" option; a host-list for which an OCSP Stapling
-is requested and required for the connection to proceed. The host(s)
-should also be in "hosts_require_tls", and "tls_verify_certificates"
-configured for the transport.
+Also, given EXPERIMENTAL_OCSP, the smtp transport gains two options:
+- "hosts_require_ocsp"; a host-list for which an OCSP Stapling
+is requested and required for the connection to proceed. The default
+value is empty.
+- "hosts_request_ocsp"; a host-list for which (additionally) an OCSP
+Stapling is requested (but not necessarily verified). The default
+value is "*" meaning that requests are made unless configured
+otherwise.
+
+The host(s) should also be in "hosts_require_tls", and
+"tls_verify_certificates" configured for the transport.
For the client to be able to verify the stapled OCSP the server must
also supply, in its stapled information, any intermediate
intermediate certificates should be added to the server OCSP stapling
file (named by tls_ocsp_file).
+Note that the proof only covers the terminal server certificate,
+not any of the chain from CA to it.
+
At this point in time, we're gathering feedback on use, to determine if
it's worth adding complexity to the Exim daemon to periodically re-fetch
OCSP files and somehow handling multiple files.
OCSP server is supplied. The server URL may be included in the
server certificate, if the CA is helpful.
- One fail mode seen was the OCSP Signer cert expiring before the end
- of vailidity of the OCSP proof. The checking done by Exim/OpenSSL
+ One failure mode seen was the OCSP Signer cert expiring before the end
+ of validity of the OCSP proof. The checking done by Exim/OpenSSL
noted this as invalid overall, but the re-fetch script did not.