Revert "Lower EXIM_CLIENT_DH_MIN_BITS 1024 -> 512."

[exim.git] / src / README.UPDATING

diff --git a/src/README.UPDATING b/src/README.UPDATING
index e685b8ec3d4aed6544f8c3067d85fb2c7d6805dc..d34dec1e1cf32d82d728e6fd5e8622d8959a24c4 100644 (file)
--- a/src/README.UPDATING
+++ b/src/README.UPDATING
@@ -31,6 +31,7 @@ Exim version 4.80
 
  * BEWARE backwards-incompatible changes in SSL libraries, thus the version
    bump.  See points below for details.
+   Also an LDAP data returned format change.
 
  * The value of $tls_peerdn is now print-escaped when written to the spool file
    in a -tls_peerdn line, and unescaped when read back in.  We received reports
@@ -42,6 +43,12 @@ Exim version 4.80
    the message.  No tool has been provided as we believe this is a rare
    occurence.
 
+ * For OpenSSL, SSLv2 is now disabled by default.  (GnuTLS does not support
+   SSLv2).  RFC 6176 prohibits SSLv2 and some informal surveys suggest no
+   actual usage.  You can re-enable with the "openssl_options" Exim option,
+   in the main configuration section.  Note that supporting SSLv2 exposes
+   you to ciphersuite downgrade attacks.
+
  * With OpenSSL 1.0.1+, Exim now supports TLS 1.1 and TLS 1.2.  If built
    against 1.0.1a then you will get a warning message and the
    "openssl_options" value will not parse "no_tlsv1_1": the value changes
@@ -51,8 +58,9 @@ Exim version 4.80
    "openssl_options" gains "no_tlsv1_1", "no_tlsv1_2" and "no_compression".
 
    COMPATIBILITY WARNING: The default value of "openssl_options" is no longer
-   "+dont_insert_empty_fragments".  We default to unset.  That old default was
-   grandfathered in from before openssl_options became a configuration option.
+   "+dont_insert_empty_fragments".  We default to "+no_sslv2".
+   That old default was grandfathered in from before openssl_options became a
+   configuration option.
    Empty fragments are inserted by default through TLS1.0, to partially defend
    against certain attacks; TLS1.1+ change the protocol so that this is not
    needed.  The DIEF SSL option was required for some old releases of mail
@@ -77,6 +85,12 @@ Exim version 4.80
    attribute as a comma-separated list.  Note the distinction from multiple
    attributes being returned, where each one is a name=value pair.
 
+   If you are currently splitting the results from LDAP upon a comma, then you
+   should check carefully to see if adjustments are needed.
+
+   This change lets cautious folks distinguish "comma used as separator for
+   joining values" from "comma inside the data".
+
  * accept_8bitmime now defaults on, which is not RFC compliant but is better
    suited to today's Internet.  See http://cr.yp.to/smtp/8bitmime.html for a
    sane rationale.  Those who wish to be strictly RFC compliant, or know that
@@ -135,6 +149,21 @@ Exim version 4.80
    fail completely.  (The check is not done as root, to ensure that problems
    here are not made worse by the check).
 
+ * The "tls_dhparam" option has been updated, so that it can now specify a
+   path or an identifier for a standard DH prime from one of a few RFCs.
+   The default for OpenSSL is no longer to not use DH but instead to use
+   one of these standard primes.  The default for GnuTLS is no longer to use
+   a file in the spool directory, but to use that same standard prime.
+   The option is now used by GnuTLS too.  If it points to a path, then
+   GnuTLS will use that path, instead of a file in the spool directory;
+   GnuTLS will attempt to create it if it does not exist.
+
+   To preserve the previous behaviour of generating files in the spool
+   directory, set "tls_dhparam = historic".  Since prior releases of Exim
+   ignored tls_dhparam when using GnuTLS, this can safely be done before
+   the upgrade.
+
+
 
 Exim version 4.77
 -----------------