Dr Stephen Henson wrote:
> A few comments about that:
Thanks for the review!
> These are cryptographic keys (or at least the HMAC and AES keys are) so you
> should use RAND_bytes(), not RAND_pseudo_bytes().
Ok - when looking at ssl_lib.c:SSL_CTX_new(), I didn't realize that
RAND_pseudo_bytes() is only used for tlsext_tick_key_name. Changed
accordingly.
> Don't dereference the structures directly as at some point the sizes might
> change, the structure made opaque or a different mechanism used for storing
> keys
> (e.g. HSM support).
I was looking at a way to determine the size at compile time, but if you
think that's an unsafe method (note: it's only expected to work for
0.9.8f through 0.9.8l), then let's change it.
> The approved way is to call:
>
> SSL_CTX_set_tlsext_ticket_keys(sc->server->ssl_ctx, NULL, -1)
>
> which will return the combined length of all keys.
Did that - does v3 of the patch (attached) look better? Is it ok to use
apr_palloc here?
> Finally:
>
> + sid_ctx = ap_md5_binary(c->pool, (unsigned char*)sc->vhost_id,
> + sc->vhost_id_len);
>
> should we be using MD5 now if it can be avoided?
That's what is currently used in mod_ssl.c:ssl_init_ssl_connection() -
these two should be kept in sync. I'm not opposed to a change (at both
places), but the question is whether now is the right time for doing
that. For distcache setups e.g. I would assume that it has some unwanted
consequences if two 2.2.x releases calculate the session id context in a
different way... but I'm interested to hear others' opinions on this.
Kaspar
Index: httpd-trunk/modules/ssl/ssl_private.h
===================================================================
--- httpd-trunk/modules/ssl/ssl_private.h (revision 833672)
+++ httpd-trunk/modules/ssl/ssl_private.h (working copy)
@@ -405,6 +405,9 @@ typedef struct {
#if defined(HAVE_OPENSSL_ENGINE_H) && defined(HAVE_ENGINE_INIT)
const char *szCryptoDevice;
#endif
+#ifndef OPENSSL_NO_TLSEXT
+ ssl_enabled_t session_tickets_enabled;
+#endif
#ifdef HAVE_OCSP_STAPLING
const ap_socache_provider_t *stapling_cache;
@@ -585,6 +588,7 @@ const char *ssl_cmd_SSLUserName(cmd_par
const char *ssl_cmd_SSLLogLevelDebugDump(cmd_parms *, void *, const char *);
const char *ssl_cmd_SSLRenegBufferSize(cmd_parms *cmd, void *dcfg, const char
*arg);
const char *ssl_cmd_SSLStrictSNIVHostCheck(cmd_parms *cmd, void *dcfg, int
flag);
+const char *ssl_cmd_SSLSessionTicketExtension(cmd_parms *cmd, void *cdfg, int
flag);
const char *ssl_cmd_SSLProxyEngine(cmd_parms *cmd, void *dcfg, int flag);
const char *ssl_cmd_SSLProxyProtocol(cmd_parms *, void *, const char *);
Index: httpd-trunk/modules/ssl/ssl_engine_init.c
===================================================================
--- httpd-trunk/modules/ssl/ssl_engine_init.c (revision 833672)
+++ httpd-trunk/modules/ssl/ssl_engine_init.c (working copy)
@@ -363,6 +363,15 @@ static void ssl_init_server_check(server
"(theoretically shouldn't happen!)");
ssl_die();
}
+
+ /*
+ * Session tickets (stateless resumption)
+ */
+ if ((myModConfig(s))->session_tickets_enabled == SSL_ENABLED_FALSE) {
+ ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s,
+ "Disabling TLS session ticket support");
+ SSL_CTX_set_options(mctx->ssl_ctx, SSL_OP_NO_TICKET);
+ }
}
#ifndef OPENSSL_NO_TLSEXT
@@ -1061,6 +1070,11 @@ void ssl_init_CheckServers(server_rec *b
BOOL conflict = FALSE;
+#if !defined(OPENSSL_NO_TLSEXT) && OPENSSL_VERSION_NUMBER < 0x009080d0
+ unsigned char *tlsext_tick_keys = NULL;
+ long tick_keys_len;
+#endif
+
/*
* Give out warnings when a server has HTTPS configured
* for the HTTP port or vice versa
@@ -1085,6 +1099,25 @@ void ssl_init_CheckServers(server_rec *b
ssl_util_vhostid(p, s),
DEFAULT_HTTP_PORT, DEFAULT_HTTPS_PORT);
}
+
+#if !defined(OPENSSL_NO_TLSEXT) && OPENSSL_VERSION_NUMBER < 0x009080d0
+ /*
+ * When using OpenSSL versions 0.9.8f through 0.9.8l, configure
+ * the same ticket encryption parameters for every SSL_CTX (workaround
+ * for SNI+SessionTicket extension interoperability issue in these
versions)
+ */
+ if ((sc->enabled == SSL_ENABLED_TRUE) ||
+ (sc->enabled == SSL_ENABLED_OPTIONAL)) {
+ if (!tlsext_tick_keys) {
+ tick_keys_len =
SSL_CTX_set_tlsext_ticket_keys(sc->server->ssl_ctx,
+ NULL, -1);
+ tlsext_tick_keys = (unsigned char *)apr_palloc(p,
tick_keys_len);
+ RAND_bytes(tlsext_tick_keys, tick_keys_len);
+ }
+ SSL_CTX_set_tlsext_ticket_keys(sc->server->ssl_ctx,
+ tlsext_tick_keys, tick_keys_len);
+ }
+#endif
}
/*
Index: httpd-trunk/modules/ssl/ssl_engine_config.c
===================================================================
--- httpd-trunk/modules/ssl/ssl_engine_config.c (revision 833672)
+++ httpd-trunk/modules/ssl/ssl_engine_config.c (working copy)
@@ -80,6 +80,9 @@ SSLModConfigRec *ssl_config_global_creat
mc->stapling_mutex_file = NULL;
mc->stapling_mutex = NULL;
#endif
+#ifndef OPENSSL_NO_TLSEXT
+ mc->session_tickets_enabled = SSL_ENABLED_UNSET;
+#endif
memset(mc->pTmpKeys, 0, sizeof(mc->pTmpKeys));
@@ -1673,6 +1676,26 @@ const char *ssl_cmd_SSLStaplingForceURL(
#endif /* HAVE_OCSP_STAPLING */
+const char *ssl_cmd_SSLSessionTicketExtension(cmd_parms *cmd, void *dcfg, int
flag)
+{
+#ifndef OPENSSL_NO_TLSEXT
+ const char *err;
+ SSLModConfigRec *mc = myModConfig(cmd->server);
+
+ if ((err = ap_check_cmd_context(cmd, GLOBAL_ONLY))) {
+ return err;
+ }
+
+ mc->session_tickets_enabled = flag ? SSL_ENABLED_TRUE : SSL_ENABLED_FALSE;
+
+ return NULL;
+#else
+ return "SSLSessionTicketExtension failed; OpenSSL is not built with
support "
+ "for TLS extensions. Refer to the documentation, and build "
+ "a compatible version of OpenSSL.";
+#endif
+}
+
void ssl_hook_ConfigTest(apr_pool_t *pconf, server_rec *s)
{
if (!ap_exists_config_define("DUMP_CERTS")) {
Index: httpd-trunk/modules/ssl/ssl_engine_kernel.c
===================================================================
--- httpd-trunk/modules/ssl/ssl_engine_kernel.c (revision 833672)
+++ httpd-trunk/modules/ssl/ssl_engine_kernel.c (working copy)
@@ -29,6 +29,7 @@
time I was too famous.''
-- Unknown */
#include "ssl_private.h"
+#include "util_md5.h"
static void ssl_configure_env(request_rec *r, SSLConnRec *sslconn);
#ifndef OPENSSL_NO_TLSEXT
@@ -1980,6 +1981,7 @@ static int ssl_find_vhost(void *serverna
apr_array_header_t *names;
int i;
SSLConnRec *sslcon;
+ char *sid_ctx;
/* check ServerName */
if (!strcasecmp(servername, s->server_hostname)) {
@@ -2044,6 +2046,21 @@ static int ssl_find_vhost(void *serverna
SSL_set_verify(ssl, SSL_CTX_get_verify_mode(ssl->ctx),
SSL_CTX_get_verify_callback(ssl->ctx));
}
+ /*
+ * Adjust the session id context. ssl_init_ssl_connection()
+ * always picks the configuration of the first vhost when
+ * calling SSL_new(), but we want to tie the session to the
+ * vhost we have just switched to. Again, we have to make sure
+ * that we're not overwriting a session id context which was
+ * possibly set in ssl_hook_Access(), before triggering
+ * a renegotation.
+ */
+ if (!SSL_num_renegotiations(ssl)) {
+ sid_ctx = ap_md5_binary(c->pool, (unsigned char*)sc->vhost_id,
+ sc->vhost_id_len);
+ SSL_set_session_id_context(ssl, (unsigned char *)sid_ctx,
+ APR_MD5_DIGESTSIZE*2);
+ }
/*
* Save the found server into our SSLConnRec for later
Index: httpd-trunk/modules/ssl/mod_ssl.c
===================================================================
--- httpd-trunk/modules/ssl/mod_ssl.c (revision 833672)
+++ httpd-trunk/modules/ssl/mod_ssl.c (working copy)
@@ -70,6 +70,8 @@ static const command_rec ssl_config_cmds
SSL_CMD_SRV(RandomSeed, TAKE23,
"SSL Pseudo Random Number Generator (PRNG) seeding source "
"('startup|connect builtin|file:/path|exec:/path [bytes]')")
+ SSL_CMD_SRV(SessionTicketExtension, FLAG,
+ "TLS Session Ticket extension support")
/*
* Per-server context configuration directives
Index: httpd-trunk/docs/manual/mod/mod_ssl.xml
===================================================================
--- httpd-trunk/docs/manual/mod/mod_ssl.xml (revision 833672)
+++ httpd-trunk/docs/manual/mod/mod_ssl.xml (working copy)
@@ -1849,4 +1849,35 @@ certificate being validated references a
</usage>
</directivesynopsis>
+<directivesynopsis>
+<name>SSLSessionTicketExtension</name>
+<description>Configure TLS session ticket extension support</description>
+<syntax>SSLSessionTicketExtension on|off</syntax>
+<default>SSLSessionTicketExtension on</default>
+<contextlist><context>server config</context></contextlist>
+<compatibility>Available in Apache 2.2.15 and later</compatibility>
+
+<usage>
+<p>
+This directive configures support for TLS session tickets (stateless session
+resumption, cf. RFC 5077). Session tickets are enabled by default when mod_ssl
+is compiled against an OpenSSL version which includes this option. They can
+coexist with a stateful session cache (configured through
+<directive module="mod_ssl">SSLSessionCache</directive>);
+it is then up to the client to choose between stateful and stateless session
+resumption.</p>
+
+<p>
+Clients based on OpenSSL versions 0.9.8f through 0.9.8l are known to
+have problems (<code>parse tlsext</code> errors) when using the SNI and session
+ticket extensions at the same time. As a workaround for interoperability issues
+like these, this directive allows to completely turn off TLS session ticket
support
+at the server side.</p>
+
+<example><title>Example</title>
+SSLSessionTicketExtension off
+</example>
+</usage>
+</directivesynopsis>
+
</modulesynopsis>
Index: httpd-2.2.x/modules/ssl/ssl_private.h
===================================================================
--- httpd-2.2.x/modules/ssl/ssl_private.h (revision 833672)
+++ httpd-2.2.x/modules/ssl/ssl_private.h (working copy)
@@ -395,6 +395,9 @@ typedef struct {
#if defined(HAVE_OPENSSL_ENGINE_H) && defined(HAVE_ENGINE_INIT)
const char *szCryptoDevice;
#endif
+#ifndef OPENSSL_NO_TLSEXT
+ ssl_enabled_t session_tickets_enabled;
+#endif
struct {
void *pV1, *pV2, *pV3, *pV4, *pV5, *pV6, *pV7, *pV8, *pV9, *pV10;
} rCtx;
@@ -545,6 +548,7 @@ const char *ssl_cmd_SSLRequire(cmd_parm
const char *ssl_cmd_SSLUserName(cmd_parms *, void *, const char *);
const char *ssl_cmd_SSLRenegBufferSize(cmd_parms *cmd, void *dcfg, const char
*arg);
const char *ssl_cmd_SSLStrictSNIVHostCheck(cmd_parms *cmd, void *dcfg, int
flag);
+const char *ssl_cmd_SSLSessionTicketExtension(cmd_parms *cmd, void *cdfg, int
flag);
const char *ssl_cmd_SSLProxyEngine(cmd_parms *cmd, void *dcfg, int flag);
const char *ssl_cmd_SSLProxyProtocol(cmd_parms *, void *, const char *);
Index: httpd-2.2.x/modules/ssl/ssl_engine_init.c
===================================================================
--- httpd-2.2.x/modules/ssl/ssl_engine_init.c (revision 833672)
+++ httpd-2.2.x/modules/ssl/ssl_engine_init.c (working copy)
@@ -382,6 +382,15 @@ static void ssl_init_ctx_tls_extensions(
ssl_log_ssl_error(APLOG_MARK, APLOG_ERR, s);
ssl_die();
}
+
+ /*
+ * Session tickets (stateless resumption)
+ */
+ if ((myModConfig(s))->session_tickets_enabled == SSL_ENABLED_FALSE) {
+ ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s,
+ "Disabling TLS session ticket support");
+ SSL_CTX_set_options(mctx->ssl_ctx, SSL_OP_NO_TICKET);
+ }
}
#endif
@@ -1018,6 +1027,11 @@ void ssl_init_CheckServers(server_rec *b
BOOL conflict = FALSE;
+#if !defined(OPENSSL_NO_TLSEXT) && OPENSSL_VERSION_NUMBER < 0x009080d0
+ unsigned char *tlsext_tick_keys = NULL;
+ long tick_keys_len;
+#endif
+
/*
* Give out warnings when a server has HTTPS configured
* for the HTTP port or vice versa
@@ -1042,6 +1056,25 @@ void ssl_init_CheckServers(server_rec *b
ssl_util_vhostid(p, s),
DEFAULT_HTTP_PORT, DEFAULT_HTTPS_PORT);
}
+
+#if !defined(OPENSSL_NO_TLSEXT) && OPENSSL_VERSION_NUMBER < 0x009080d0
+ /*
+ * When using OpenSSL versions 0.9.8f through 0.9.8l, configure
+ * the same ticket encryption parameters for every SSL_CTX (workaround
+ * for SNI+SessionTicket extension interoperability issue in these
versions)
+ */
+ if ((sc->enabled == SSL_ENABLED_TRUE) ||
+ (sc->enabled == SSL_ENABLED_OPTIONAL)) {
+ if (!tlsext_tick_keys) {
+ tick_keys_len =
SSL_CTX_set_tlsext_ticket_keys(sc->server->ssl_ctx,
+ NULL, -1);
+ tlsext_tick_keys = (unsigned char *)apr_palloc(p,
tick_keys_len);
+ RAND_bytes(tlsext_tick_keys, tick_keys_len);
+ }
+ SSL_CTX_set_tlsext_ticket_keys(sc->server->ssl_ctx,
+ tlsext_tick_keys, tick_keys_len);
+ }
+#endif
}
/*
Index: httpd-2.2.x/modules/ssl/ssl_engine_config.c
===================================================================
--- httpd-2.2.x/modules/ssl/ssl_engine_config.c (revision 833672)
+++ httpd-2.2.x/modules/ssl/ssl_engine_config.c (working copy)
@@ -75,6 +75,9 @@ SSLModConfigRec *ssl_config_global_creat
#if defined(HAVE_OPENSSL_ENGINE_H) && defined(HAVE_ENGINE_INIT)
mc->szCryptoDevice = NULL;
#endif
+#ifndef OPENSSL_NO_TLSEXT
+ mc->session_tickets_enabled = SSL_ENABLED_UNSET;
+#endif
memset(mc->pTmpKeys, 0, sizeof(mc->pTmpKeys));
@@ -1471,6 +1474,26 @@ const char *ssl_cmd_SSLStrictSNIVHostCh
#endif
}
+const char *ssl_cmd_SSLSessionTicketExtension(cmd_parms *cmd, void *dcfg, int
flag)
+{
+#ifndef OPENSSL_NO_TLSEXT
+ const char *err;
+ SSLModConfigRec *mc = myModConfig(cmd->server);
+
+ if ((err = ap_check_cmd_context(cmd, GLOBAL_ONLY))) {
+ return err;
+ }
+
+ mc->session_tickets_enabled = flag ? SSL_ENABLED_TRUE : SSL_ENABLED_FALSE;
+
+ return NULL;
+#else
+ return "SSLSessionTicketExtension failed; OpenSSL is not built with
support "
+ "for TLS extensions. Refer to the documentation, and build "
+ "a compatible version of OpenSSL.";
+#endif
+}
+
void ssl_hook_ConfigTest(apr_pool_t *pconf, server_rec *s)
{
if (!ap_exists_config_define("DUMP_CERTS")) {
Index: httpd-2.2.x/modules/ssl/ssl_engine_kernel.c
===================================================================
--- httpd-2.2.x/modules/ssl/ssl_engine_kernel.c (revision 833672)
+++ httpd-2.2.x/modules/ssl/ssl_engine_kernel.c (working copy)
@@ -29,6 +29,7 @@
time I was too famous.''
-- Unknown */
#include "ssl_private.h"
+#include "util_md5.h"
static void ssl_configure_env(request_rec *r, SSLConnRec *sslconn);
#ifndef OPENSSL_NO_TLSEXT
@@ -2010,6 +2011,7 @@ static int ssl_find_vhost(void *serverna
apr_array_header_t *names;
int i;
SSLConnRec *sslcon;
+ char *sid_ctx;
/* check ServerName */
if (!strcasecmp(servername, s->server_hostname)) {
@@ -2074,6 +2076,21 @@ static int ssl_find_vhost(void *serverna
SSL_set_verify(ssl, SSL_CTX_get_verify_mode(ssl->ctx),
SSL_CTX_get_verify_callback(ssl->ctx));
}
+ /*
+ * Adjust the session id context. ssl_init_ssl_connection()
+ * always picks the configuration of the first vhost when
+ * calling SSL_new(), but we want to tie the session to the
+ * vhost we have just switched to. Again, we have to make sure
+ * that we're not overwriting a session id context which was
+ * possibly set in ssl_hook_Access(), before triggering
+ * a renegotation.
+ */
+ if (!SSL_num_renegotiations(ssl)) {
+ sid_ctx = ap_md5_binary(c->pool, (unsigned char*)sc->vhost_id,
+ sc->vhost_id_len);
+ SSL_set_session_id_context(ssl, (unsigned char *)sid_ctx,
+ APR_MD5_DIGESTSIZE*2);
+ }
/*
* Save the found server into our SSLConnRec for later
Index: httpd-2.2.x/modules/ssl/mod_ssl.c
===================================================================
--- httpd-2.2.x/modules/ssl/mod_ssl.c (revision 833672)
+++ httpd-2.2.x/modules/ssl/mod_ssl.c (working copy)
@@ -92,6 +92,8 @@ static const command_rec ssl_config_cmds
SSL_CMD_SRV(RandomSeed, TAKE23,
"SSL Pseudo Random Number Generator (PRNG) seeding source "
"(`startup|connect builtin|file:/path|exec:/path [bytes]')")
+ SSL_CMD_SRV(SessionTicketExtension, FLAG,
+ "TLS Session Ticket extension support")
/*
* Per-server context configuration directives
Index: httpd-2.2.x/docs/manual/mod/mod_ssl.xml
===================================================================
--- httpd-2.2.x/docs/manual/mod/mod_ssl.xml (revision 833672)
+++ httpd-2.2.x/docs/manual/mod/mod_ssl.xml (working copy)
@@ -1808,4 +1808,35 @@ SSLCryptoDevice ubsec
</usage>
</directivesynopsis>
+<directivesynopsis>
+<name>SSLSessionTicketExtension</name>
+<description>Configure TLS session ticket extension support</description>
+<syntax>SSLSessionTicketExtension on|off</syntax>
+<default>SSLSessionTicketExtension on</default>
+<contextlist><context>server config</context></contextlist>
+<compatibility>Available in Apache 2.2.15 and later</compatibility>
+
+<usage>
+<p>
+This directive configures support for TLS session tickets (stateless session
+resumption, cf. RFC 5077). Session tickets are enabled by default when mod_ssl
+is compiled against an OpenSSL version which includes this option. They can
+coexist with a stateful session cache (configured through
+<directive module="mod_ssl">SSLSessionCache</directive>);
+it is then up to the client to choose between stateful and stateless session
+resumption.</p>
+
+<p>
+Clients based on OpenSSL versions 0.9.8f through 0.9.8l are known to
+have problems (<code>parse tlsext</code> errors) when using the SNI and session
+ticket extensions at the same time. As a workaround for interoperability issues
+like these, this directive allows to completely turn off TLS session ticket
support
+at the server side.</p>
+
+<example><title>Example</title>
+SSLSessionTicketExtension off
+</example>
+</usage>
+</directivesynopsis>
+
</modulesynopsis>
