Re-add curve fallback detection
This commit is contained in:
Julien Vehent
parent
04314bffdc
commit
4d7e1cb05a
114
cipherscan
114
cipherscan
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@ -63,6 +63,8 @@ CAPATH=""
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SAVECRT=""
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TEST_CURVES="False"
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has_curves="False"
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# openssl formated list of curves that will cause server to select ECC suite
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ecc_ciphers=""
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unset known_certs
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declare -A known_certs
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unset cert_checksums
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@ -458,7 +460,11 @@ test_cipher_on_target() {
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if [[ $pfs =~ ECDH ]]; then
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has_curves="True"
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if [ $TEST_CURVES == "True" ]; then
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test_ecc_curves
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test_curves
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if [ "$ecc_ciphers" != "" ]; then
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ecc_ciphers+=":"
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fi
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ecc_ciphers+="$cipher"
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else
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# resolve the openssl curve to the proper IANA name
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current_curves="$(get_curve_name $(echo $pfs|cut -d ',' -f2))"
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@ -622,6 +628,7 @@ display_results_in_terminal() {
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fi
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if [ $TEST_CURVES == "True" ]; then
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echo "Curves ordering: $curvesordering"
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echo "Curves fallback: $fallback_supported"
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fi
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}
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@ -656,7 +663,11 @@ display_results_in_json() {
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echo -n "}"
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ctr=$((ctr+1))
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done
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echo ']}'
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echo -n ']'
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if [ $TEST_CURVES == "True" ]; then
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echo -n ",\"curves_fallback\":\"$fallback_supported\""
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fi
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echo '}'
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}
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test_serverside_ordering() {
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@ -712,9 +723,7 @@ test_serverside_ordering() {
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fi
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}
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test_ecc_curves() {
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# openssl formated list of curves that will cause server to select ECC suite
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local ecc_ciphers=""
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test_curves() {
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# "True" if server supports ciphers that don't use ECC at a lower priority
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local fallback_available="False"
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@ -817,8 +826,7 @@ test_ecc_curves() {
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local tmp=$(echo Q | $sslcommand -curves $test_curves 2>/dev/null)
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parse_openssl_output <<<"$tmp"
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if [[ -z $current_protocol || $current_cipher == "(NONE)" \
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|| $current_cipher == '0000' ]]; then
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if [[ -z $current_protocol || $current_cipher == "(NONE)" || $current_cipher == '0000' ]]; then
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fallback_supported="order-specific"
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verbose "Server aborted connection"
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else
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@ -829,18 +837,14 @@ test_ecc_curves() {
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if [[ ${ephem_data[0]} =~ ECDH ]]; then
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verbose "Server did select ${ephem_data[1]} curve"
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curves_ordering="inconclusive-${ephem_data[1]}"
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for id in "${!curve_names[@]}"; do
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if [[ ${curve_names[$id]} =~ ${ephem_data[1]} ]]; then
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local canonic_name=(${curve_names[$id]})
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if [[ ${canonic_name[0]} == $most_wanted ]]; then
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curves_ordering="client"
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break
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else
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curves_ordering="server"
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break
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fi
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fi
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done
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local cname="$(get_curve_name ${ephem_data[1]})"
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if [ "$cname" == "$most_wanted" ]; then
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curves_ordering="client"
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break
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else
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curves_ordering="server"
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break
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fi
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else
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# some servers downgrade to non ECDH when curve order is changed
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curves_ordering="inconclusive-noecc"
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@ -849,6 +853,76 @@ test_ecc_curves() {
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fi
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}
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test_curves_fallback() {
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# "True" if server supports ciphers that don't use ECC at a lower priority
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local fallback_available="False"
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# return variable: whatever a server will fall back to non ECC suite when
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# client doesn't advertise support for curves the server needs
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fallback_supported="False"
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# prepare the ssl command we'll be using
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local sslcommand=""
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sslcommand="$TIMEOUTBIN $TIMEOUT $OPENSSLBIN s_client"
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if [ -n "$CAPATH" ]; then
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sslcommand+=" -CApath $CAPATH -showcerts"
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elif [ -e "$CACERTS" ]; then
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sslcommand+=" -CAfile $CACERTS"
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fi
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sslcommand+=" -status $SCLIENTARGS -connect $TARGET -cipher $ecc_ciphers"
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# force the TLS to send a TLS1.0 client hello at least, as with SSLv2
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# ciphers present it will try to send a SSLv2 compatible client hello
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sslcommand+=" -no_ssl2 -no_ssl3"
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#
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# here we use the same logic as with detecting cipher suites: first
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# advertise all curves as supported, then remove curves one by one until we
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# either get a fallback to a non ECC cipher, we run of curves or server
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# tries to negotiate a curve we didn't advertise
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#
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local curves=(${CURVES[*]})
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while [[ ${#curves[@]} -gt 0 ]]; do
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OLDIFS="$IFS"
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IFS=':'
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local test_curves="${curves[*]}"
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IFS="$OLDIFS"
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verbose "Testing $test_curves"
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ratelimit
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local tmp=$(echo Q | $sslcommand -curves $test_curves 2>/dev/null)
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parse_openssl_output <<<"$tmp"
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if [[ -z $current_protocol || $current_cipher == "(NONE)" || $current_cipher == '0000' ]]; then
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# server aborted connection
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if [[ $fallback_available == "True" ]]; then
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fallback_supported="False"
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else
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fallback_supported="unknown"
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fi
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break
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else
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# server accepted connection
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local ephem_data=(${current_pfs//,/ })
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if [[ ${ephem_data[0]} =~ ECDH ]]; then
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# we got an ecc connection, remove the curve from the list of testable curves
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local cname="$(get_curve_name ${ephem_data[1]})"
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verbose "Server selected curve $cname"
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for id in "${!curves[@]}"; do
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if [ "${curves[id]}" == "$cname" ]; then
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unset curves[$id]
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break
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fi
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done
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else
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verbose "Server fell back to $current_cipher"
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# ok, we got a fallback
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fallback_supported="True"
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break
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fi
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fi
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done
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}
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# If no options are given, give usage information and exit (with error code)
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if [ $# -eq 0 ]; then
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usage;
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@ -979,7 +1053,7 @@ get_cipher_pref $CIPHERSUITE
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test_serverside_ordering
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if [[ $TEST_CURVES == "True" ]]; then
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test_ecc_curves
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test_curves_fallback
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fi
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if [ "$OUTPUTFORMAT" == "json" ]; then
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