[PATCH] SSL: support automatic selection of ECDH temporary key parameters

[Piotr Sikora]

Hello,
slightly better patch attached.

Hopefully, now that ALPN (OpenSSL-1.0.2+ feature) is in, this can be
also committed :)

Best regards,
Piotr Sikora


# HG changeset patch
# User Piotr Sikora <piotr at cloudflare.com>
# Date 1391123946 28800
#      Thu Jan 30 15:19:06 2014 -0800
# Node ID 63c549cc2e817772979238f055b72a4f96198a2a
# Parent  2e40188f83ef5bf1ae5afe0dd445689049f46a5c
SSL: support automatic selection of ECDH temporary key parameters.

When compiled against OpenSSL-1.0.2+, the colon separated list of
supported curves can be provided using either curve NIDs:

    ssl_ecdh_curve  secp521r1:secp384r1:prime256v1;

or names:

    ssl_ecdh_curve  P-521:P-384:P-256;

Signed-off-by: Piotr Sikora <piotr at cloudflare.com>

diff -r 2e40188f83ef -r 63c549cc2e81 src/event/ngx_event_openssl.c
--- a/src/event/ngx_event_openssl.c Thu Jan 30 19:13:12 2014 +0400
+++ b/src/event/ngx_event_openssl.c Thu Jan 30 15:19:06 2014 -0800
@@ -681,6 +681,23 @@ ngx_ssl_ecdh_curve(ngx_conf_t *cf, ngx_s
 {
 #if OPENSSL_VERSION_NUMBER >= 0x0090800fL
 #ifndef OPENSSL_NO_ECDH
+#ifdef SSL_CTRL_SET_ECDH_AUTO
+
+    if (SSL_CTX_set1_curves_list(ssl->ctx, name->data) == 0) {
+        ngx_ssl_error(NGX_LOG_EMERG, ssl->log, 0,
+                      "Unknown curve in \"%s\"", name->data);
+        return NGX_ERROR;
+    }
+
+    if (SSL_CTX_set_ecdh_auto(ssl->ctx, 1) == 0) {
+        ngx_ssl_error(NGX_LOG_EMERG, ssl->log, 0,
+                      "Unable to set automatic curve selection for \"%s\"",
+                      name->data);
+        return NGX_ERROR;
+    }
+
+#else
+
     int      nid;
     EC_KEY  *ecdh;

@@ -710,6 +727,8 @@ ngx_ssl_ecdh_curve(ngx_conf_t *cf, ngx_s
     SSL_CTX_set_tmp_ecdh(ssl->ctx, ecdh);

     EC_KEY_free(ecdh);
+
+#endif
 #endif
 #endif