Add support for tls-ciphersuites for TLS 1.3

OpenSSL 1.1.1 introduces a separate list for TLS 1.3 ciphers. As these
interfaces are meant to be user facing or not exposed at all and we
expose the tls-cipher interface, we should also expose tls-cipherlist.

Combining both settings into tls-cipher would add a lot of glue logic
that needs to be maintained and is error prone. On top of that, users
should not set either settings unless absolutely required.

OpenSSL's own s_client/s_server also expose both settings and I believe
most other software will too:

 -cipher val         Specify TLSv1.2 and below cipher list to be used
 -ciphersuites val   Specify TLSv1.3 ciphersuites to be used

For mbed TLS only the future can tell if we will see a combined or also
two separate lists.
Acked-by: Steffan Karger <steffan.karger@fox-it.com>
Message-Id: <20181007215539.32761-1-arne@rfc2549.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg17626.html

Signed-off-by: Gert Doering <gert@greenie.muc.de>

1 files changed, 56 insertions, 0 deletions

diff --git a/src/openvpn/ssl_openssl.c b/src/openvpn/ssl_openssl.c
index 0858d5e..ba0d132 100644
--- a/src/openvpn/ssl_openssl.c
+++ b/src/openvpn/ssl_openssl.c
@@ -391,6 +391,7 @@ convert_tls_list_to_openssl(char* openssl_ciphers, size_t len,const char *cipher
         openssl_ciphers[openssl_ciphers_len-1] = '\0';
     }
 }
+
 void
 tls_ctx_restrict_ciphers(struct tls_root_ctx *ctx, const char *ciphers)
 {
@@ -427,6 +428,61 @@ tls_ctx_restrict_ciphers(struct tls_root_ctx *ctx, const char *ciphers)
 }
 
 void
+convert_tls13_list_to_openssl(char* openssl_ciphers, size_t len, const char *ciphers)
+{
+    /*
+     * OpenSSL (and official IANA) cipher names have _ in them. We
+     * historically used names with - in them. Silently convert names
+     * with - to names with _ to support both
+     */
+    if (strlen(ciphers) >= (len - 1))
+    {
+        msg(M_FATAL,
+            "Failed to set restricted TLS 1.3 cipher list, too long (>%d).",
+            (int) (len - 1));
+    }
+
+    strncpy(openssl_ciphers, ciphers, len);
+
+    for (size_t i = 0; i < strlen(openssl_ciphers); i++)
+    {
+        if (openssl_ciphers[i] == '-')
+        {
+            openssl_ciphers[i] = '_';
+        }
+    }
+}
+
+void
+tls_ctx_restrict_ciphers_tls13(struct tls_root_ctx *ctx, const char *ciphers)
+{
+    if (ciphers == NULL)
+    {
+        /* default cipher list of OpenSSL 1.1.1 is sane, do not set own
+         * default as we do with tls-cipher */
+        return;
+    }
+
+#if (OPENSSL_VERSION_NUMBER < 0x1010100fL)
+        crypto_msg(M_WARN, "Not compiled with OpenSSL 1.1.1 or higher. "
+                       "Ignoring TLS 1.3 only tls-ciphersuites '%s' setting.",
+                        ciphers);
+#else
+    ASSERT(NULL != ctx);
+
+    char openssl_ciphers[4096];
+    convert_tls13_list_to_openssl(openssl_ciphers, sizeof(openssl_ciphers),
+                                  ciphers);
+
+    if (!SSL_CTX_set_ciphersuites(ctx->ctx, openssl_ciphers))
+    {
+        crypto_msg(M_FATAL, "Failed to set restricted TLS 1.3 cipher list: %s",
+                   openssl_ciphers);
+    }
+#endif
+}
+
+void
 tls_ctx_set_cert_profile(struct tls_root_ctx *ctx, const char *profile)
 {
 #ifdef HAVE_SSL_CTX_SET_SECURITY_LEVEL