OCSP stapling: ssl_trusted_certificate directive.

The directive allows to specify additional trusted Certificate Authority
certificates to be used during certificate verification.  In contrast to
ssl_client_certificate DNs of these cerificates aren't sent to a client
during handshake.

Trusted certificates are loaded regardless of the fact whether client
certificates verification is enabled as the same certificates will be
used for OCSP stapling, during construction of an OCSP request and for
verification of an OCSP response.

The same applies to a CRL (which is now always loaded).

src/event/ngx_event_openssl.c

@@ -296,6 +296,33 @@ ngx_ssl_client_certificate(ngx_conf_t *cf, ngx_ssl_t *ssl, ngx_str_t *cert,
 }
 
 
+ngx_int_t
+ngx_ssl_trusted_certificate(ngx_conf_t *cf, ngx_ssl_t *ssl, ngx_str_t *cert,
+    ngx_int_t depth)
+{
+    SSL_CTX_set_verify_depth(ssl->ctx, depth);
+
+    if (cert->len == 0) {
+        return NGX_OK;
+    }
+
+    if (ngx_conf_full_name(cf->cycle, cert, 1) != NGX_OK) {
+        return NGX_ERROR;
+    }
+
+    if (SSL_CTX_load_verify_locations(ssl->ctx, (char *) cert->data, NULL)
+        == 0)
+    {
+        ngx_ssl_error(NGX_LOG_EMERG, ssl->log, 0,
+                      "SSL_CTX_load_verify_locations(\"%s\") failed",
+                      cert->data);
+        return NGX_ERROR;
+    }
+
+    return NGX_OK;
+}
+
+
 ngx_int_t
 ngx_ssl_crl(ngx_conf_t *cf, ngx_ssl_t *ssl, ngx_str_t *crl)
 {

src/event/ngx_event_openssl.h

@@ -101,6 +101,8 @@ ngx_int_t ngx_ssl_certificate(ngx_conf_t *cf, ngx_ssl_t *ssl,
     ngx_str_t *cert, ngx_str_t *key);
 ngx_int_t ngx_ssl_client_certificate(ngx_conf_t *cf, ngx_ssl_t *ssl,
     ngx_str_t *cert, ngx_int_t depth);
+ngx_int_t ngx_ssl_trusted_certificate(ngx_conf_t *cf, ngx_ssl_t *ssl,
+    ngx_str_t *cert, ngx_int_t depth);
 ngx_int_t ngx_ssl_crl(ngx_conf_t *cf, ngx_ssl_t *ssl, ngx_str_t *crl);
 RSA *ngx_ssl_rsa512_key_callback(SSL *ssl, int is_export, int key_length);
 ngx_int_t ngx_ssl_dhparam(ngx_conf_t *cf, ngx_ssl_t *ssl, ngx_str_t *file);

src/http/modules/ngx_http_ssl_module.c

@@ -124,6 +124,13 @@ static ngx_command_t  ngx_http_ssl_commands[] = {
       offsetof(ngx_http_ssl_srv_conf_t, client_certificate),
       NULL },
 
+    { ngx_string("ssl_trusted_certificate"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_TAKE1,
+      ngx_conf_set_str_slot,
+      NGX_HTTP_SRV_CONF_OFFSET,
+      offsetof(ngx_http_ssl_srv_conf_t, trusted_certificate),
+      NULL },
+
     { ngx_string("ssl_prefer_server_ciphers"),
       NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_FLAG,
       ngx_conf_set_flag_slot,
@@ -325,6 +332,7 @@ ngx_http_ssl_create_srv_conf(ngx_conf_t *cf)
      *     sscf->dhparam = { 0, NULL };
      *     sscf->ecdh_curve = { 0, NULL };
      *     sscf->client_certificate = { 0, NULL };
+     *     sscf->trusted_certificate = { 0, NULL };
      *     sscf->crl = { 0, NULL };
      *     sscf->ciphers = { 0, NULL };
      *     sscf->shm_zone = NULL;
@@ -380,6 +388,8 @@ ngx_http_ssl_merge_srv_conf(ngx_conf_t *cf, void *parent, void *child)
 
     ngx_conf_merge_str_value(conf->client_certificate, prev->client_certificate,
                          "");
+    ngx_conf_merge_str_value(conf->trusted_certificate,
+                         prev->trusted_certificate, "");
     ngx_conf_merge_str_value(conf->crl, prev->crl, "");
 
     ngx_conf_merge_str_value(conf->ecdh_curve, prev->ecdh_curve,
@@ -479,11 +489,19 @@ ngx_http_ssl_merge_srv_conf(ngx_conf_t *cf, void *parent, void *child)
         {
             return NGX_CONF_ERROR;
         }
+    }
+
+    if (ngx_ssl_trusted_certificate(cf, &conf->ssl,
+                                    &conf->trusted_certificate,
+                                    conf->verify_depth)
+        != NGX_OK)
+    {
+        return NGX_CONF_ERROR;
+    }
 
     if (ngx_ssl_crl(cf, &conf->ssl, &conf->crl) != NGX_OK) {
         return NGX_CONF_ERROR;
     }
-    }
 
     if (conf->prefer_server_ciphers) {
         SSL_CTX_set_options(conf->ssl.ctx, SSL_OP_CIPHER_SERVER_PREFERENCE);

src/http/modules/ngx_http_ssl_module.h

@@ -35,6 +35,7 @@ typedef struct {
     ngx_str_t                       dhparam;
     ngx_str_t                       ecdh_curve;
     ngx_str_t                       client_certificate;
+    ngx_str_t                       trusted_certificate;
     ngx_str_t                       crl;
 
     ngx_str_t                       ciphers;