From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Christophe Fergeau Date: Mon, 18 Jun 2018 12:39:37 +0200 Subject: [spice-server] 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 This is only meant to be a temporary solution, and will be superseded by crypto-policies when they land in RHEL.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 --- docs/Makefile.am | 1 + server/reds.c | 102 +++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 103 insertions(+) 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/server/reds.c b/server/reds.c index 0af5643..846e44d 100644 --- a/server/reds.c +++ b/server/reds.c @@ -33,6 +33,7 @@ #include #include +#include #include #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; }