From d44d04e2ceb255acf9f98fa3448f09dd893eec60 Mon Sep 17 00:00:00 2001
From: "Roger A. Light" <roger@atchoo.org>
Date: Wed, 9 Dec 2020 15:40:45 +0000
Subject: [PATCH] Fix DH group not being set for TLS connections.
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This meant ciphers using DHE couldn't be used.

Closes #1925. Closes #1476. Thanks to Jonathan Sönnerup, Valerii
Demeshko, and sectokia.
---
 ChangeLog.txt | 2 ++
 src/net.c     | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/ChangeLog.txt b/ChangeLog.txt
index 5be1bc2f5a..d762a3f541 100644
--- a/ChangeLog.txt
+++ b/ChangeLog.txt
@@ -1,6 +1,8 @@
 Broker:
 - Fix websockets connections on Windows blocking subsequent connections.
   Closes #1934.
+- Fix DH group not being set for TLS connections, which meant ciphers using
+  DHE couldn't be used. Closes #1925. Closes #1476.
 
 Apps:
 - Fix `mosquitto_passwd -U`
diff --git a/src/net.c b/src/net.c
index b4cfdcb758..b274458233 100644
--- a/src/net.c
+++ b/src/net.c
@@ -373,6 +373,9 @@ int net__tls_server_ctx(struct mosquitto__listener *listener)
 	SSL_CTX_set_ecdh_auto(listener->ssl_ctx, 1);
 #endif
 #endif
+#if OPENSSL_VERSION_NUMBER >= 0x10100000L
+	SSL_CTX_set_dh_auto(listener->ssl_ctx, 1);
+#endif
 
 #ifdef SSL_OP_NO_RENEGOTIATION
 	SSL_CTX_set_options(listener->ssl_ctx, SSL_OP_NO_RENEGOTIATION);