From e370f5d27681fd83e3d2a0e7d7bd7aab93361528 Mon Sep 17 00:00:00 2001
From: Christopher Fredericks <cfredmakecode@gmail.com>
Date: Wed, 10 Dec 2014 20:38:24 -0500
Subject: [PATCH] added diffie-hellman parameter functions. allows using DHE-*
 cipher suites

---
 dhparam.go | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 dhparam.go

diff --git a/dhparam.go b/dhparam.go
new file mode 100644
index 0000000..a698645
--- /dev/null
+++ b/dhparam.go
@@ -0,0 +1,65 @@
+// +build cgo
+
+package openssl
+
+/*
+#include <openssl/crypto.h>
+#include <openssl/ssl.h>
+#include <openssl/err.h>
+#include <openssl/conf.h>
+#include <openssl/dh.h>
+
+static long SSL_CTX_set_tmp_dh_not_a_macro(SSL_CTX* ctx, DH *dh) {
+    return SSL_CTX_set_tmp_dh(ctx, dh);
+}
+static long PEM_read_DHparams_not_a_macro(SSL_CTX* ctx, DH *dh) {
+    return SSL_CTX_set_tmp_dh(ctx, dh);
+}
+*/
+import "C"
+
+import (
+	"errors"
+	"runtime"
+	"unsafe"
+)
+
+type DH struct {
+	dh *C.struct_dh_st
+}
+
+// LoadDHParametersFromPEM loads the Diffie-Hellman parameters from
+// a PEM-encoded block.
+func LoadDHParametersFromPEM(pem_block []byte) (*DH, error) {
+	if len(pem_block) == 0 {
+		return nil, errors.New("empty pem block")
+	}
+	bio := C.BIO_new_mem_buf(unsafe.Pointer(&pem_block[0]),
+		C.int(len(pem_block)))
+	if bio == nil {
+		return nil, errors.New("failed creating bio")
+	}
+	defer C.BIO_free(bio)
+
+	params := C.PEM_read_bio_DHparams(bio, nil, nil, nil)
+	if params == nil {
+		return nil, errors.New("failed reading dh parameters")
+	}
+	dhparams := &DH{dh: params}
+	runtime.SetFinalizer(dhparams, func(dhparams *DH) {
+		C.DH_free(dhparams.dh)
+	})
+	return dhparams, nil
+}
+
+// SetDHParameters sets the DH group (DH parameters) used to
+// negotiate an emphemeral DH key during handshaking.
+func (c *Ctx) SetDHParameters(dh *DH) error {
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	if int(C.SSL_CTX_set_tmp_dh_not_a_macro(c.ctx, dh.dh)) != 1 {
+		return errorFromErrorQueue()
+	}
+	return nil
+}