SSL: support for compressed server certificates with OpenSSL.

The ssl_certificate_compression directive allows to send compressed
server certificates.  In OpenSSL, they are pre-compressed on startup.
To simplify configuration, the SSL_OP_NO_TX_CERTIFICATE_COMPRESSION
option is automatically cleared if certificates were pre-compressed.

SSL_CTX_compress_certs() may return an error in legitimate cases,
e.g., when none of compression algorithms is available or if the
resulting compressed size is larger than the original one, thus it
is silently ignored.

Certificate compression is supported in Chrome with brotli only,
in Safari with zlib only, and in Firefox with all listed algorithms.
It is supported since Ubuntu 24.10, which has OpenSSL with enabled
zlib and zstd support.

The actual list of algorithms supported in OpenSSL depends on how
the library was configured; it can be brotli, zlib, zstd as listed
in RFC 8879.

diff --git a/src/event/ngx_event_openssl.c b/src/event/ngx_event_openssl.c
index 0c23c3f2f7d751fcab7fd7958dc70e3d8e9e0cab..e36f30c74a212e68313fee0a3319368bb0e971b2 100644 (file)
--- a/src/event/ngx_event_openssl.c
+++ b/src/event/ngx_event_openssl.c
@@ -664,6 +664,36 @@ retry:
 }
 
 
+ngx_int_t
+ngx_ssl_certificate_compression(ngx_conf_t *cf, ngx_ssl_t *ssl,
+    ngx_uint_t enable)
+{
+    if (!enable) {
+        return NGX_OK;
+    }
+
+#ifdef SSL_OP_NO_TX_CERTIFICATE_COMPRESSION
+
+    if (SSL_CTX_compress_certs(ssl->ctx, 0) == 0) {
+        ngx_ssl_error(NGX_LOG_WARN, ssl->log, 0,
+                      "SSL_CTX_compress_certs() failed, ignored");
+        return NGX_OK;
+    }
+
+    SSL_CTX_clear_options(ssl->ctx, SSL_OP_NO_TX_CERTIFICATE_COMPRESSION);
+
+#else
+
+    ngx_log_error(NGX_LOG_WARN, ssl->log, 0,
+                  "\"ssl_certificate_compression\" is not supported "
+                  "on this platform, ignored");
+
+#endif
+
+    return NGX_OK;
+}
+
+
 ngx_int_t
 ngx_ssl_ciphers(ngx_conf_t *cf, ngx_ssl_t *ssl, ngx_str_t *ciphers,
     ngx_uint_t prefer_server_ciphers)

diff --git a/src/event/ngx_event_openssl.h b/src/event/ngx_event_openssl.h
index 0c9e9e84012015ba78030af24be709cc9383e18d..e7ccd51e80cb6dc9983c6553b8cdca1dff7a4741 100644 (file)
--- a/src/event/ngx_event_openssl.h
+++ b/src/event/ngx_event_openssl.h
@@ -236,6 +236,8 @@ ngx_int_t ngx_ssl_certificate(ngx_conf_t *cf, ngx_ssl_t *ssl,
 ngx_int_t ngx_ssl_connection_certificate(ngx_connection_t *c, ngx_pool_t *pool,
     ngx_str_t *cert, ngx_str_t *key, ngx_ssl_cache_t *cache,
     ngx_array_t *passwords);
+ngx_int_t ngx_ssl_certificate_compression(ngx_conf_t *cf, ngx_ssl_t *ssl,
+    ngx_uint_t enable);
 
 ngx_int_t ngx_ssl_ciphers(ngx_conf_t *cf, ngx_ssl_t *ssl, ngx_str_t *ciphers,
     ngx_uint_t prefer_server_ciphers);

diff --git a/src/http/modules/ngx_http_ssl_module.c b/src/http/modules/ngx_http_ssl_module.c
index dbfe5c08bf16ee9c411bacd9af84fbe0be01a389..fbf4ab8713239cbac332bc278edbf48771e72298 100644 (file)
--- a/src/http/modules/ngx_http_ssl_module.c
+++ b/src/http/modules/ngx_http_ssl_module.c
@@ -124,6 +124,13 @@ static ngx_command_t  ngx_http_ssl_commands[] = {
       0,
       NULL },
 
+    { ngx_string("ssl_certificate_compression"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_flag_slot,
+      NGX_HTTP_SRV_CONF_OFFSET,
+      offsetof(ngx_http_ssl_srv_conf_t, certificate_compression),
+      NULL },
+
     { ngx_string("ssl_dhparam"),
       NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_TAKE1,
       ngx_conf_set_str_slot,
@@ -621,6 +628,7 @@ ngx_http_ssl_create_srv_conf(ngx_conf_t *cf)
      */
 
     sscf->prefer_server_ciphers = NGX_CONF_UNSET;
+    sscf->certificate_compression = NGX_CONF_UNSET;
     sscf->early_data = NGX_CONF_UNSET;
     sscf->reject_handshake = NGX_CONF_UNSET;
     sscf->buffer_size = NGX_CONF_UNSET_SIZE;
@@ -658,6 +666,9 @@ ngx_http_ssl_merge_srv_conf(ngx_conf_t *cf, void *parent, void *child)
     ngx_conf_merge_value(conf->prefer_server_ciphers,
                          prev->prefer_server_ciphers, 0);
 
+    ngx_conf_merge_value(conf->certificate_compression,
+                         prev->certificate_compression, 0);
+
     ngx_conf_merge_value(conf->early_data, prev->early_data, 0);
     ngx_conf_merge_value(conf->reject_handshake, prev->reject_handshake, 0);
 
@@ -792,6 +803,13 @@ ngx_http_ssl_merge_srv_conf(ngx_conf_t *cf, void *parent, void *child)
         {
             return NGX_CONF_ERROR;
         }
+
+        if (ngx_ssl_certificate_compression(cf, &conf->ssl,
+                                            conf->certificate_compression)
+            != NGX_OK)
+        {
+            return NGX_CONF_ERROR;
+        }
     }
 
     conf->ssl.buffer_size = conf->buffer_size;

diff --git a/src/http/modules/ngx_http_ssl_module.h b/src/http/modules/ngx_http_ssl_module.h
index 8650fab9376ceca9debef186023d44da2d9bb0c5..9b26529fa98349c4a937d1a364f292035b75ee1b 100644 (file)
--- a/src/http/modules/ngx_http_ssl_module.h
+++ b/src/http/modules/ngx_http_ssl_module.h
@@ -18,6 +18,7 @@ typedef struct {
     ngx_ssl_t                       ssl;
 
     ngx_flag_t                      prefer_server_ciphers;
+    ngx_flag_t                      certificate_compression;
     ngx_flag_t                      early_data;
     ngx_flag_t                      reject_handshake;
 

diff --git a/src/mail/ngx_mail_ssl_module.c b/src/mail/ngx_mail_ssl_module.c
index 176e9c62472417d5b98e2222c4161be9982331fa..079d0e77340210bc72b81b472af62e6d7eb0da35 100644 (file)
--- a/src/mail/ngx_mail_ssl_module.c
+++ b/src/mail/ngx_mail_ssl_module.c
@@ -97,6 +97,13 @@ static ngx_command_t  ngx_mail_ssl_commands[] = {
       0,
       NULL },
 
+    { ngx_string("ssl_certificate_compression"),
+      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_flag_slot,
+      NGX_MAIL_SRV_CONF_OFFSET,
+      offsetof(ngx_mail_ssl_conf_t, certificate_compression),
+      NULL },
+
     { ngx_string("ssl_dhparam"),
       NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
       ngx_conf_set_str_slot,
@@ -314,6 +321,7 @@ ngx_mail_ssl_create_conf(ngx_conf_t *cf)
     scf->passwords = NGX_CONF_UNSET_PTR;
     scf->conf_commands = NGX_CONF_UNSET_PTR;
     scf->prefer_server_ciphers = NGX_CONF_UNSET;
+    scf->certificate_compression = NGX_CONF_UNSET;
     scf->verify = NGX_CONF_UNSET_UINT;
     scf->verify_depth = NGX_CONF_UNSET_UINT;
     scf->builtin_session_cache = NGX_CONF_UNSET;
@@ -343,6 +351,9 @@ ngx_mail_ssl_merge_conf(ngx_conf_t *cf, void *parent, void *child)
     ngx_conf_merge_value(conf->prefer_server_ciphers,
                          prev->prefer_server_ciphers, 0);
 
+    ngx_conf_merge_value(conf->certificate_compression,
+                         prev->certificate_compression, 0);
+
     ngx_conf_merge_bitmask_value(conf->protocols, prev->protocols,
                          (NGX_CONF_BITMASK_SET|NGX_SSL_DEFAULT_PROTOCOLS));
 
@@ -446,6 +457,13 @@ ngx_mail_ssl_merge_conf(ngx_conf_t *cf, void *parent, void *child)
         return NGX_CONF_ERROR;
     }
 
+    if (ngx_ssl_certificate_compression(cf, &conf->ssl,
+                                        conf->certificate_compression)
+        != NGX_OK)
+    {
+        return NGX_CONF_ERROR;
+    }
+
     if (conf->verify) {
 
         if (conf->verify != 3

diff --git a/src/mail/ngx_mail_ssl_module.h b/src/mail/ngx_mail_ssl_module.h
index c0eb6a38f83418ae9421cdd623d87f5cd256dff3..a0e9a173a767c7cf9370f1e31b5674e2941bc568 100644 (file)
--- a/src/mail/ngx_mail_ssl_module.h
+++ b/src/mail/ngx_mail_ssl_module.h
@@ -21,6 +21,7 @@
 
 typedef struct {
     ngx_flag_t       prefer_server_ciphers;
+    ngx_flag_t       certificate_compression;
 
     ngx_ssl_t        ssl;
 

diff --git a/src/stream/ngx_stream_ssl_module.c b/src/stream/ngx_stream_ssl_module.c
index 2f1b996246f542c49aad6d8e7d831c4e6c021e97..7ce1175f1800d8d518d1994eece5997d0f02d268 100644 (file)
--- a/src/stream/ngx_stream_ssl_module.c
+++ b/src/stream/ngx_stream_ssl_module.c
@@ -133,6 +133,13 @@ static ngx_command_t  ngx_stream_ssl_commands[] = {
       0,
       NULL },
 
+    { ngx_string("ssl_certificate_compression"),
+      NGX_STREAM_MAIN_CONF|NGX_STREAM_SRV_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_flag_slot,
+      NGX_STREAM_SRV_CONF_OFFSET,
+      offsetof(ngx_stream_ssl_srv_conf_t, certificate_compression),
+      NULL },
+
     { ngx_string("ssl_dhparam"),
       NGX_STREAM_MAIN_CONF|NGX_STREAM_SRV_CONF|NGX_CONF_TAKE1,
       ngx_conf_set_str_slot,
@@ -881,6 +888,7 @@ ngx_stream_ssl_create_srv_conf(ngx_conf_t *cf)
     sscf->passwords = NGX_CONF_UNSET_PTR;
     sscf->conf_commands = NGX_CONF_UNSET_PTR;
     sscf->prefer_server_ciphers = NGX_CONF_UNSET;
+    sscf->certificate_compression = NGX_CONF_UNSET;
     sscf->reject_handshake = NGX_CONF_UNSET;
     sscf->verify = NGX_CONF_UNSET_UINT;
     sscf->verify_depth = NGX_CONF_UNSET_UINT;
@@ -914,6 +922,9 @@ ngx_stream_ssl_merge_srv_conf(ngx_conf_t *cf, void *parent, void *child)
     ngx_conf_merge_value(conf->prefer_server_ciphers,
                          prev->prefer_server_ciphers, 0);
 
+    ngx_conf_merge_value(conf->certificate_compression,
+                         prev->certificate_compression, 0);
+
     ngx_conf_merge_value(conf->reject_handshake, prev->reject_handshake, 0);
 
     ngx_conf_merge_bitmask_value(conf->protocols, prev->protocols,
@@ -1039,6 +1050,13 @@ ngx_stream_ssl_merge_srv_conf(ngx_conf_t *cf, void *parent, void *child)
         {
             return NGX_CONF_ERROR;
         }
+
+        if (ngx_ssl_certificate_compression(cf, &conf->ssl,
+                                            conf->certificate_compression)
+            != NGX_OK)
+        {
+            return NGX_CONF_ERROR;
+        }
     }
 
     if (conf->verify) {

diff --git a/src/stream/ngx_stream_ssl_module.h b/src/stream/ngx_stream_ssl_module.h
index ffa03a6f3439de1f77684f2cdf7fdd793a013265..31f138cfd85048bc8f81b311dcd2fc18531f64ff 100644 (file)
--- a/src/stream/ngx_stream_ssl_module.h
+++ b/src/stream/ngx_stream_ssl_module.h
@@ -18,6 +18,7 @@ typedef struct {
     ngx_msec_t        handshake_timeout;
 
     ngx_flag_t        prefer_server_ciphers;
+    ngx_flag_t        certificate_compression;
     ngx_flag_t        reject_handshake;
 
     ngx_ssl_t         ssl;