Add warning for the --show-groups command that some groups are missing

OpenSSL has a weird way of only reporting EC curves that are implemented
in a certain way in the list of all EC curves. Note this fact and point
out that also the very important curves X448 and X25519 are affected.

Change-Id: I86641bf60d62a50e9b2719e809d2429d65c00097
Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
Message-Id: <20231009105714.34598-1-frank@lichtenheld.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg27193.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>

diff --git a/src/openvpn/ssl_openssl.c b/src/openvpn/ssl_openssl.c
index b5cc9a7f1c99eb81576cce080159c385acaf6f92..b561e9d6bee2051d63442fedd268678664c16034 100644 (file)
--- a/src/openvpn/ssl_openssl.c
+++ b/src/openvpn/ssl_openssl.c
@@ -2249,8 +2249,10 @@ show_available_tls_ciphers_list(const char *cipher_list,
 void
 show_available_curves(void)
 {
-    printf("Consider using openssl 'ecparam -list_curves' as\n"
-           "alternative to running this command.\n");
+    printf("Consider using 'openssl ecparam -list_curves' as alternative to running\n"
+           "this command.\n"
+           "Note this output does only list curves/groups that OpenSSL considers as\n"
+           "builtin EC curves. It does not list additional curves nor X448 or X25519\n");
 #ifndef OPENSSL_NO_EC
     EC_builtin_curve *curves = NULL;
     size_t crv_len = 0;