MINOR: ssl: Update ssl_fc_curve/ssl_bc_curve to use SSL_get0_group_name

The function `smp_fetch_ssl_fc_ec` gets the curve name used during key
exchange. It currently uses the `SSL_get_negotiated_group`, available
since OpenSSLv3.0 to get the nid and derive the short name of the curve
from the nid. In OpenSSLv3.2, a new function, `SSL_get0_group_name` was
added that directly gives the curve name.

The function `smp_fetch_ssl_fc_ec` has been updated to use
`SSL_get0_group_name` if using OpenSSL>=3.2 and for versions >=3.0 and <
3.2 use the old SSL_get_negotiated_group to get the curve name. Another
change made is to normalize the return value, so that
`smp_fetch_ssl_fc_ec` returns curve name in uppercase.
(`SSL_get0_group_name` returns the curve name in lowercase and
`SSL_get_negotiated_group` + `OBJ_nid2sn` returns curve name in
uppercase).

Can be backported to 2.8.

src/ssl_sample.c

@@ -1317,7 +1317,8 @@ smp_fetch_ssl_fc_ec(const struct arg *args, struct sample *smp, const char *kw,
 {
     struct connection *conn;
     SSL *ssl;
-    int nid;
+    int __maybe_unused nid;
+    char *curve_name;
 
     if (obj_type(smp->sess->origin) == OBJ_TYPE_CHECK)
         conn = (kw[4] == 'b') ? sc_conn(__objt_check(smp->sess->origin)->sc) : NULL;
@@ -1329,10 +1330,36 @@ smp_fetch_ssl_fc_ec(const struct arg *args, struct sample *smp, const char *kw,
     if (!ssl)
         return 0;
 
+    /*
+     * SSL_get0_group_name is a function to get the curve name and is available from
+     * OpenSSL v3.2 onwards. For OpenSSL >=3.0 and <3.2, we will continue to use
+     * SSL_get_negotiated_group to get the curve name.
+     */
+    #if (HA_OPENSSL_VERSION_NUMBER >= 0x3020000fL)
+      curve_name = (char *)SSL_get0_group_name(ssl);
+      if (curve_name == NULL)
+              return 0;
+      else {
+              /**
+               * The curve name returned by SSL_get0_group_name is in lowercase whereas the curve
+               * name returned when we use `SSL_get_negotiated_group` and `OBJ_nid2sn` is the
+               * short name and is in upper case. To make the return value consistent across the
+               * different functional calls and to make it consistent while upgrading OpenSSL versions,
+               * will convert the curve name returned by SSL_get0_group_name to upper case.
+               */
+              for (int i = 0; curve_name[i]; i++)
+                  curve_name[i] = toupper(curve_name[i]);
+      }
+    #else
       nid = SSL_get_negotiated_group(ssl);
       if (!nid)
              return 0;
-    smp->data.u.str.area = (char *)OBJ_nid2sn(nid);
+      curve_name = (char *)OBJ_nid2sn(nid);
+      if (curve_name == NULL)
+             return 0;
+    #endif
+
+    smp->data.u.str.area = curve_name;
     if (!smp->data.u.str.area)
         return 0;