From c0a15e07cd718cb6e455e68328f522ac076a0e4b Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas
Date: Mon, 31 Jul 2017 22:36:09 +0300
Subject: Always use 2048 bit DH parameters for OpenSSL ephemeral DH ciphers.
1024 bits is considered weak these days, but OpenSSL always passes 1024 as
the key length to the tmp_dh callback. All the code to handle other key
lengths is, in fact, dead.
To remedy those issues:
* Only include hard-coded 2048-bit parameters.
* Set the parameters directly with SSL_CTX_set_tmp_dh(), without the
callback
* The name of the file containing the DH parameters is now a GUC. This
replaces the old hardcoded "dh1024.pem" filename. (The files for other
key lengths, dh512.pem, dh2048.pem, etc. were never actually used.)
This is not a new problem, but it doesn't seem worth the risk and churn to
backport. If you care enough about the strength of the DH parameters on
old versions, you can create custom DH parameters, with as many bits as you
wish, and put them in the "dh1024.pem" file.
Per report by Nicolas Guini and Damian Quiroga. Reviewed by Michael Paquier.
Discussion: https://www.postgresql.org/message-id/CAMxBoUyjOOautVozN6ofzym828aNrDjuCcOTcCquxjwS-L2hGQ@mail.gmail.com
---
doc/src/sgml/config.sgml | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
(limited to 'doc/src')
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index b45b7f7f69..c33d6a0349 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1203,6 +1203,30 @@ include_dir 'conf.d'
+
+ ssl_dh_params_file (string)
+
+ ssl_dh_params_file> configuration parameter
+
+
+
+
+ Specifies the name of the file containing Diffie-Hellman parameters
+ used for so-called ephemeral DH family of SSL ciphers. The default is
+ empty, in which case compiled-in default DH parameters used. Using
+ custom DH parameters reduces the exposure if an attacker manages to
+ crack the well-known compiled-in DH parameters. You can create your own
+ DH parameters file with the command
+ openssl dhparam -out dhparams.pem 2048.
+
+
+
+ This parameter can only be set in the postgresql.conf>
+ file or on the server command line.
+
+
+
+
krb_server_keyfile (string)
--
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