Fix #2131

This commit fixes #2131 by having run_fs() attempt a TLS 1.2 ClientHello if the initial TLS 1.3 ClientHello fails. The TLS 1.2 ClientHello will offer many more curves than the TLS 1.3 ClientHello offers, and so it may succeed if the server supports ECDHE ciphers, but only with curves that were removed by RFC 8446.

testssl.sh

@@ -10239,6 +10239,7 @@ run_fs() {
      local -a supported_curve
      local -i nr_supported_ciphers=0 nr_curves=0 nr_ossl_curves=0 i j low high
      local fs_ciphers curves_offered="" curves_to_test temp
+     local curves_option="" curves_list1="" curves_list2=""
      local len1 len2 curve_found
      local key_bitstring quality_str
      local -i len_dh_p quality
@@ -10307,6 +10308,12 @@ run_fs() {
           tls_sockets "04" "${fs_hex_cipher_list:2}, 00,ff"
           sclient_success=$?
           [[ $sclient_success -eq 2 ]] && sclient_success=0
+          # Sometimes a TLS 1.3 ClientHello will fail, but a TLS 1.2 ClientHello will succeed. See #2131.
+          if [[ $sclient_success -ne 0 ]]; then
+               tls_sockets "03" "${fs_hex_cipher_list:2}, 00,ff"
+               sclient_success=$?
+               [[ $sclient_success -eq 2 ]] && sclient_success=0
+          fi
      else
           debugme echo $nr_supported_ciphers
           debugme echo $(actually_supported_osslciphers $fs_cipher_list "ALL")
@@ -10320,6 +10327,38 @@ run_fs() {
           sclient_connect_successful $? $TMPFILE
           sclient_success=$?
           [[ $sclient_success -eq 0 ]] && [[ $(grep -ac "BEGIN CERTIFICATE" $TMPFILE) -eq 0 ]] && sclient_success=1
+          # Sometimes a TLS 1.3 ClientHello will fail, but a TLS 1.2 ClientHello will succeed. See #2131.
+          if [[ $sclient_success -ne 0 ]] && "$HAS_TLS13"; then
+               # By default, OpenSSL 1.1.1 and above only include a few curves in the ClientHello, so in order
+               # to test all curves, the -curves option must be added. In addition, OpenSSL limits the number of
+               # curves that can be specified to 28. So, if more than 28 curves are supported, then the curves must
+               # be tested in batches.
+               if [[ "$(count_words "$OSSL_SUPPORTED_CURVES")" -le 28 ]]; then
+                    curves_list1="$(strip_trailing_space "$(strip_leading_space "$OSSL_SUPPORTED_CURVES")")"
+                    curves_list1="${curves_list1// /:}"
+               else
+                    # Place the first 28 supported curves in curves_list1 and the remainder in curves_list2.
+                    curves_list1="$(strip_trailing_space "$(strip_leading_space "$OSSL_SUPPORTED_CURVES")")"
+                    curves_list1="${curves_list1//  / }"
+                    curves_list2="${curves_list1#* * * * * * * * * * * * * * * * * * * * * * * * * * * * }"
+                    curves_list1="${curves_list1%$curves_list2}"
+                    curves_list1="$(strip_trailing_space "$curves_list1")"
+                    curves_list1="${curves_list1// /:}"
+                    curves_list2="${curves_list2// /:}"
+               fi
+               curves_option="-curves $curves_list1"
+               $OPENSSL s_client $(s_client_options "-cipher $fs_cipher_list $curves_option $STARTTLS $BUGS -connect $NODEIP:$PORT $PROXY $SNI") >$TMPFILE 2>$ERRFILE </dev/null
+               sclient_connect_successful $? $TMPFILE
+               sclient_success=$?
+               [[ $sclient_success -eq 0 ]] && [[ $(grep -ac "BEGIN CERTIFICATE" $TMPFILE) -eq 0 ]] && sclient_success=1
+               if [[ $sclient_success -ne 0 ]] && [[ -n "$curves_list2" ]]; then
+                    curves_option="-curves $curves_list2"
+                    $OPENSSL s_client $(s_client_options "-cipher $fs_cipher_list $curves_option $STARTTLS $BUGS -connect $NODEIP:$PORT $PROXY $SNI") >$TMPFILE 2>$ERRFILE </dev/null
+                    sclient_connect_successful $? $TMPFILE
+                    sclient_success=$?
+                    [[ $sclient_success -eq 0 ]] && [[ $(grep -ac "BEGIN CERTIFICATE" $TMPFILE) -eq 0 ]] && sclient_success=1
+               fi
+          fi
      fi
 
      if [[ $sclient_success -ne 0 ]]; then
@@ -10359,7 +10398,7 @@ run_fs() {
                          fi
                     done
                     [[ -z "$ciphers_to_test" ]] && [[ -z "$tls13_ciphers_to_test" ]] && break
-                    $OPENSSL s_client $(s_client_options "$proto -cipher "\'${ciphers_to_test:1}\'" -ciphersuites "\'${tls13_ciphers_to_test:1}\'" $STARTTLS $BUGS -connect $NODEIP:$PORT $PROXY $SNI") &>$TMPFILE </dev/null
+                    $OPENSSL s_client $(s_client_options "$proto -cipher "\'${ciphers_to_test:1}\'" -ciphersuites "\'${tls13_ciphers_to_test:1}\'" $curves_option $STARTTLS $BUGS -connect $NODEIP:$PORT $PROXY $SNI") &>$TMPFILE </dev/null
                     sclient_connect_successful $? $TMPFILE || break
                     fs_cipher=$(get_cipher $TMPFILE)
                     [[ -z "$fs_cipher" ]] && break