From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Christophe Fergeau <cfergeau@redhat.com>
Date: Mon, 18 Jun 2018 12:39:37 +0200
Subject: [PATCH] tls: Parse spice.cnf OpenSSL configuration file
SPICE tries to use the OpenSSL system-wide defaults as much as possible
for the TLS ciphers and protocols it uses. However, this is not enough
for some customers who want it to use a more restrictive set of TLS
features. spice-server should not try to override the system defaults
OpenSSL uses, so this is not going to be hardcoded in spice-server code.
This is addressed with crypto policies in recent fedoras, and is being
solved upstream through https://github.com/openssl/openssl/pull/4848
This issue has become pressing enough that we need to solve it in el7
which unfortunately does not have any of these system-wide settings.
As a stop-gap measure, this downstream-only patch adds a
/etc/pki/tls/spice.cnf configuration file which can be used to configure
the TLS ciphers/protocols used for SPICE. This is only meant to be a
temporary solution, and will be superseded by crypto-policies when they
land in RHEL.
Signed-off-by: Christophe Fergeau <cfergeau@redhat.com>
---
docs/Makefile.am | 1 +
docs/spice.cnf.sample | 15 +++++++
server/reds.c | 102 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 118 insertions(+)
create mode 100644 docs/spice.cnf.sample
diff --git a/docs/Makefile.am b/docs/Makefile.am
index 45667a6..909ed15 100644
--- a/docs/Makefile.am
+++ b/docs/Makefile.am
@@ -6,6 +6,7 @@ EXTRA_DIST = \
spice_style.txt \
spice_threading_model.html \
spice_threading_model.txt \
+ spice.cnf.sample \
$(NULL)
if BUILD_MANUAL
diff --git a/docs/spice.cnf.sample b/docs/spice.cnf.sample
new file mode 100644
index 0000000..e5404ae
--- /dev/null
+++ b/docs/spice.cnf.sample
@@ -0,0 +1,15 @@
+# SPICE OpenSSL configuration file
+#
+# Sample configuration file for SPICE TLS communication
+# Edit the file according to your needs, and put it in
+# /etc/pki/tls/spice.cnf
+#
+# See "SUPPORTED CONFIGURATION FILE COMMANDS" in SSL_CONF_cmd(3)
+# for the valid options, as well a ciphers(1) for the format
+# of CipherString
+
+# Configure available ciphers
+CipherString = DEFAULT:-RC4:-3DES:-DES
+
+# Only enable TLSv1.2 (and newer TLS versions the day OpenSSL supports them)
+Protocol = ALL,-SSLv2,-SSLv3,-TLSv1,-TLSv1.1
diff --git a/server/reds.c b/server/reds.c
index 0af5643..846e44d 100644
--- a/server/reds.c
+++ b/server/reds.c
@@ -33,6 +33,7 @@
#include <sys/mman.h>
#include <ctype.h>
+#include <openssl/conf.h>
#include <openssl/err.h>
#if HAVE_SASL
@@ -2827,6 +2828,102 @@ static gpointer openssl_global_init(gpointer arg)
return NULL;
}
+#define SPICE_OPENSSL_CNF_FILENAME "/etc/pki/tls/spice.cnf"
+
+static int reds_ssl_config_file_apply(RedsState *reds, STACK_OF(CONF_VALUE) *sect)
+{
+ int openssl_status;
+ int return_value = 0;
+ SSL_CONF_CTX *cctx = NULL;
+ unsigned int i;
+
+ cctx = SSL_CONF_CTX_new();
+ SSL_CONF_CTX_set_flags(cctx, SSL_CONF_FLAG_SERVER);
+ SSL_CONF_CTX_set_flags(cctx, SSL_CONF_FLAG_FILE);
+ SSL_CONF_CTX_set_ssl_ctx(cctx, reds->ctx);
+
+ for (i = 0; i < sk_CONF_VALUE_num(sect); i++) {
+ CONF_VALUE *option_value;
+ option_value = sk_CONF_VALUE_value(sect, i);
+ g_message("setting TLS option '%s' to '%s' from %s configuration file",
+ option_value->name, option_value->value,
+ SPICE_OPENSSL_CNF_FILENAME);
+ openssl_status = SSL_CONF_cmd(cctx, option_value->name, option_value->value);
+ switch(openssl_status) {
+ case 1: /* fallthrough */
+ case 2:
+ /* The option was successfully processed */
+ break;
+ case 0:
+ g_warning("failure to set option '%s'", option_value->name);
+ return_value = -1;
+ break;
+ case -2:
+ g_warning("unknown option '%s'", option_value->name);
+ return_value = -1;
+ break;
+ case -3:
+ g_warning("missing value for option '%s'", option_value->name);
+ return_value = -1;
+ break;
+ default:
+ g_warning("unknown SSL_CONF_cmd return value: %d", openssl_status);
+ return_value = -1;
+ break;
+ }
+ }
+
+ openssl_status = SSL_CONF_CTX_finish(cctx);
+ if (!openssl_status) {
+ g_warning("SSL_CONF_CTX_finish() failed");
+ return_value = -1;
+ }
+
+ SSL_CONF_CTX_free(cctx);
+
+ return return_value;
+}
+
+static int reds_ssl_config_file_try_load(RedsState *reds)
+{
+ int status = -1;
+ int openssl_status;
+ CONF *ssl_conf = NULL;
+ STACK_OF(CONF_VALUE) *default_section;
+ long error_line = -1;
+
+ if (!g_file_test(SPICE_OPENSSL_CNF_FILENAME, G_FILE_TEST_IS_REGULAR)) {
+ /* The configuration file is not mandatory, it's only meant to be used
+ * when the sysadmin does not want to use the system-wide OpenSSL defaults
+ */
+ return 0;
+ }
+
+ ssl_conf = NCONF_new(NULL);
+ openssl_status = NCONF_load(ssl_conf, SPICE_OPENSSL_CNF_FILENAME, &error_line);
+ if (openssl_status <= 0) {
+ if (error_line <= 0) {
+ g_warning("error loading config file %s", SPICE_OPENSSL_CNF_FILENAME);
+ } else {
+ g_warning("error parsing config file %s at %ld", SPICE_OPENSSL_CNF_FILENAME, error_line);
+ }
+ goto end;
+ }
+
+ default_section = NCONF_get_section(ssl_conf, "default");
+ if (default_section == NULL) {
+ g_warning("could not find any content in %s config file (no toplevel section?)", SPICE_OPENSSL_CNF_FILENAME);
+ goto end;
+ }
+
+ status = reds_ssl_config_file_apply(reds, default_section);
+
+end:
+ NCONF_free(ssl_conf);
+
+ return status;
+}
+
static int reds_init_ssl(RedsState *reds)
{
static GOnce openssl_once = G_ONCE_INIT;
@@ -2911,6 +3008,11 @@ static int reds_init_ssl(RedsState *reds)
sk_zero(cmp_stack);
#endif
+ /* must be last to override whatever was configured previously */
+ if (reds_ssl_config_file_try_load(reds) != 0) {
+ return -1;
+ }
+
return 0;
}