SSL: ssl_conf_command directive.

With the ssl_conf_command directive it is now possible to set
arbitrary OpenSSL configuration parameters as long as nginx is compiled
with OpenSSL 1.0.2 or later.  Full list of available configuration
commands can be found in the SSL_CONF_cmd manual page
(https://www.openssl.org/docs/man1.1.1/man3/SSL_CONF_cmd.html).

In particular, this allows configuring PrioritizeChaCha option
(ticket #1445):

    ssl_conf_command Options PrioritizeChaCha;

It can be also used to configure TLSv1.3 ciphers in OpenSSL,
which fails to configure them via the SSL_CTX_set_cipher_list()
interface (ticket #1529):

    ssl_conf_command Ciphersuites TLS_CHACHA20_POLY1305_SHA256;

Configuration commands are applied after nginx own configuration
for SSL, so they can be used to override anything set by nginx.
Note though that configuring OpenSSL directly with ssl_conf_command
might result in a behaviour nginx does not expect, and should be
done with care.

2 files changed, 33 insertions, 0 deletions

diff --git a/src/mail/ngx_mail_ssl_module.c b/src/mail/ngx_mail_ssl_module.c
index e193b298e..d560bd60c 100644
--- a/src/mail/ngx_mail_ssl_module.c
+++ b/src/mail/ngx_mail_ssl_module.c
@@ -26,6 +26,9 @@ static char *ngx_mail_ssl_password_file(ngx_conf_t *cf, ngx_command_t *cmd,
 static char *ngx_mail_ssl_session_cache(ngx_conf_t *cf, ngx_command_t *cmd,
     void *conf);
 
+static char *ngx_mail_ssl_conf_command_check(ngx_conf_t *cf, void *post,
+    void *data);
+
 
 static ngx_conf_enum_t  ngx_mail_starttls_state[] = {
     { ngx_string("off"), NGX_MAIL_STARTTLS_OFF },
@@ -61,6 +64,10 @@ static ngx_conf_deprecated_t  ngx_mail_ssl_deprecated = {
 };
 
 
+static ngx_conf_post_t  ngx_mail_ssl_conf_command_post =
+    { ngx_mail_ssl_conf_command_check };
+
+
 static ngx_command_t  ngx_mail_ssl_commands[] = {
 
     { ngx_string("ssl"),
@@ -196,6 +203,13 @@ static ngx_command_t  ngx_mail_ssl_commands[] = {
       offsetof(ngx_mail_ssl_conf_t, crl),
       NULL },
 
+    { ngx_string("ssl_conf_command"),
+      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE2,
+      ngx_conf_set_keyval_slot,
+      NGX_MAIL_SRV_CONF_OFFSET,
+      offsetof(ngx_mail_ssl_conf_t, conf_commands),
+      &ngx_mail_ssl_conf_command_post },
+
       ngx_null_command
 };
 
@@ -259,6 +273,7 @@ ngx_mail_ssl_create_conf(ngx_conf_t *cf)
     scf->certificates = NGX_CONF_UNSET_PTR;
     scf->certificate_keys = NGX_CONF_UNSET_PTR;
     scf->passwords = NGX_CONF_UNSET_PTR;
+    scf->conf_commands = NGX_CONF_UNSET_PTR;
     scf->prefer_server_ciphers = NGX_CONF_UNSET;
     scf->verify = NGX_CONF_UNSET_UINT;
     scf->verify_depth = NGX_CONF_UNSET_UINT;
@@ -316,6 +331,8 @@ ngx_mail_ssl_merge_conf(ngx_conf_t *cf, void *parent, void *child)
 
     ngx_conf_merge_str_value(conf->ciphers, prev->ciphers, NGX_DEFAULT_CIPHERS);
 
+    ngx_conf_merge_ptr_value(conf->conf_commands, prev->conf_commands, NULL);
+
 
     conf->ssl.log = cf->log;
 
@@ -461,6 +478,10 @@ ngx_mail_ssl_merge_conf(ngx_conf_t *cf, void *parent, void *child)
         return NGX_CONF_ERROR;
     }
 
+    if (ngx_ssl_conf_commands(cf, &conf->ssl, conf->conf_commands) != NGX_OK) {
+        return NGX_CONF_ERROR;
+    }
+
     return NGX_CONF_OK;
 }
 
@@ -654,3 +675,14 @@ invalid:
 
     return NGX_CONF_ERROR;
 }
+
+
+static char *
+ngx_mail_ssl_conf_command_check(ngx_conf_t *cf, void *post, void *data)
+{
+#ifndef SSL_CONF_FLAG_FILE
+    return "is not supported on this platform";
+#endif
+
+    return NGX_CONF_OK;
+}
diff --git a/src/mail/ngx_mail_ssl_module.h b/src/mail/ngx_mail_ssl_module.h
index d6b0b8e0d..a0a611317 100644
--- a/src/mail/ngx_mail_ssl_module.h
+++ b/src/mail/ngx_mail_ssl_module.h
@@ -48,6 +48,7 @@ typedef struct {
     ngx_str_t        ciphers;
 
     ngx_array_t     *passwords;
+    ngx_array_t     *conf_commands;
 
     ngx_shm_zone_t  *shm_zone;