Disable ssl renegotiation by default.

While postgres' use of SSL renegotiation is a good idea in theory, it
turned out to not work well in practice. The specification and openssl's
implementation of it have lead to several security issues. Postgres' use
of renegotiation also had its share of bugs.

Additionally OpenSSL has a bunch of bugs around renegotiation, reported
and open for years, that regularly lead to connections breaking with
obscure error messages. We tried increasingly complex workarounds to get
around these bugs, but we didn't find anything complete.

Since these connection breakages often lead to hard to debug problems,
e.g. spuriously failing base backups and significant latency spikes when
synchronous replication is used, we have decided to change the default
setting for ssl renegotiation to 0 (disabled) in the released
backbranches and remove it entirely in 9.5 and master..

Author: Michael Paquier, with changes by me
Discussion: 20150624144148.GQ4797@alap3.anarazel.de
Backpatch: 9.0-9.4; 9.5 and master get a different patch

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 2f37a29f5e4d291a3c90671faa9156ee4d7dcf25..412e4eb2fc724d50cd71f1fbd0ce3f0d40059fb7 100644 (file)
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -670,7 +670,7 @@ SET ENABLE_SEQSCAN TO OFF;
         cryptanalysis when large amounts of traffic can be examined, but it
         also carries a large performance penalty. The sum of sent and received
         traffic is used to check the limit. If this parameter is set to 0,
-        renegotiation is disabled. The default is <literal>512MB</>.
+        renegotiation is disabled. The default is <literal>0</>.
        </para>
        <note>
         <para>
@@ -682,6 +682,14 @@ SET ENABLE_SEQSCAN TO OFF;
          disabled.
         </para>
        </note>
+
+       <warning>
+        <para>
+         Due to bugs in <productname>OpenSSL</> enabling ssl renegotiation, by
+         configuring a non-zero <varname>ssl_renegotiation_limit</>, is likely
+         to lead to problems like long-lived connections breaking.
+        </para>
+       </warning>
       </listitem>
      </varlistentry>
 

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index c171539209e84dd37ed16b899a09489c916818a2..203f2026633ff8176d2392e4e7e041f18306ebf4 100644 (file)
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2012,7 +2012,7 @@ static struct config_int ConfigureNamesInt[] =
                        GUC_UNIT_KB,
                },
                &ssl_renegotiation_limit,
-               512 * 1024, 0, MAX_KILOBYTES, NULL, NULL
+               0, 0, MAX_KILOBYTES, NULL, NULL
        },
 
        {

diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 155af1cb988947d87abbaa9c7ff1b88a290fcdf1..1ebe72d723e68e4771f85a8478087ece77ccfd32 100644 (file)
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -80,7 +80,7 @@
 #ssl = off                             # (change requires restart)
 #ssl_ciphers = 'ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH'     # allowed SSL ciphers
                                        # (change requires restart)
-#ssl_renegotiation_limit = 512MB       # amount of data between renegotiations
+#ssl_renegotiation_limit = 0           # amount of data between renegotiations
 #password_encryption = on
 #db_user_namespace = off