OCSP stapling: ssl_stapling_verify directive.

OCSP response verification is now switched off by default to simplify
configuration, and the ssl_stapling_verify allows to switch it on.

Note that for stapling OCSP response verification isn't something required
as it will be done by a client anyway.  But doing verification on a server
allows to mitigate some attack vectors, most notably stop an attacker from
presenting some specially crafted data to all site clients.

2 files changed, 10 insertions, 5 deletions

diff --git a/src/event/ngx_event_openssl.h b/src/event/ngx_event_openssl.h
index fc098da87..d1fb5739f 100644
--- a/src/event/ngx_event_openssl.h
+++ b/src/event/ngx_event_openssl.h
@@ -106,7 +106,7 @@ 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);
 ngx_int_t ngx_ssl_stapling(ngx_conf_t *cf, ngx_ssl_t *ssl,
-    ngx_str_t *responder, ngx_str_t *file);
+    ngx_str_t *file, ngx_str_t *responder, ngx_uint_t verify);
 ngx_int_t ngx_ssl_stapling_resolver(ngx_conf_t *cf, ngx_ssl_t *ssl,
     ngx_resolver_t *resolver, ngx_msec_t resolver_timeout);
 RSA *ngx_ssl_rsa512_key_callback(SSL *ssl, int is_export, int key_length);
diff --git a/src/event/ngx_event_openssl_stapling.c b/src/event/ngx_event_openssl_stapling.c
index c09b9f7ec..51caea6f0 100644
--- a/src/event/ngx_event_openssl_stapling.c
+++ b/src/event/ngx_event_openssl_stapling.c
@@ -33,7 +33,8 @@ typedef struct {
 
     time_t                       valid;
 
-    ngx_uint_t                   loading;     /* unsigned:1 */
+    unsigned                     verify:1;
+    unsigned                     loading:1;
 } ngx_ssl_stapling_t;
 
 
@@ -114,8 +115,8 @@ static u_char *ngx_ssl_ocsp_log_error(ngx_log_t *log, u_char *buf, size_t len);
 
 
 ngx_int_t
-ngx_ssl_stapling(ngx_conf_t *cf, ngx_ssl_t *ssl, ngx_str_t *responder,
-    ngx_str_t *file)
+ngx_ssl_stapling(ngx_conf_t *cf, ngx_ssl_t *ssl, ngx_str_t *file,
+    ngx_str_t *responder, ngx_uint_t verify)
 {
     ngx_int_t                  rc;
     ngx_pool_cleanup_t        *cln;
@@ -144,6 +145,7 @@ ngx_ssl_stapling(ngx_conf_t *cf, ngx_ssl_t *ssl, ngx_str_t *responder,
 
     staple->ssl_ctx = ssl->ctx;
     staple->timeout = 60000;
+    staple->verify = verify;
 
     if (file->len) {
         /* use OCSP response from the file */
@@ -588,7 +590,10 @@ ngx_ssl_stapling_ocsp_handler(ngx_ssl_ocsp_ctx_t *ctx)
     chain = staple->ssl_ctx->extra_certs;
 #endif
 
-    if (OCSP_basic_verify(basic, chain, store, OCSP_TRUSTOTHER) != 1) {
+    if (OCSP_basic_verify(basic, chain, store,
+                          staple->verify ? OCSP_TRUSTOTHER : OCSP_NOVERIFY)
+        != 1)
+    {
         ngx_ssl_error(NGX_LOG_ERR, ctx->log, 0,
                       "OCSP_basic_verify() failed");
         goto error;