Merge pull request #118 from JonnyHightower/master

Added a check for TLS_FALLBACK_SCSV

CREDITS.md

@@ -34,6 +34,9 @@
 * Dmitri S
  - inspiration & help for Darwin port
 
+* Jonathan Roach
+ - TLS_FALLBACK_SCSV checks
+
 * Bug reports:
   - Viktor Szépe, Olivier Paroz, Jan H. Terstegge, Lorenz Adena
 

testssl.sh

@@ -2617,6 +2617,46 @@ EOF
 	return $ret
 }
 
+# Test for TLS_FALLBACK_SCSV
+tls_fallback_scsv() {
+	# This isn't a vulnerability check per se, but checks for the existence of
+	# the countermeasure to protect against protocol downgrade attacks.
+
+	# First check we have support for TLS_FALLBACK_SCSV in our local OpenSSL
+	$OPENSSL s_client -h 2>&1 | grep -q "\-fallback_scsv"
+	if [ $? -gt 0 ]; then
+		pr_magentaln "Local Problem: Your $OPENSSL lacks TLS_FALLBACK_SCSV support"
+		return 4
+	fi
+
+	# Set up a local temporary file in which to store OpenSSL's output...
+	local TEMP="/tmp"
+	if [ ! -z "$HOME" ] && [ -w "$HOME" ]; then
+		TEMP="$HOME"
+	fi
+	local scsv="$TEMP/.testssl_scsv-${NODEIP}-${PORT}.txt"
+	ret=1
+
+	# ...and do the test
+	[ $VULN_COUNT -le $VULN_THRESHLD ]  && outln && pr_blue "--> Testing for TLS_FALLBACK_SCSV Support" && outln "\n"
+	pr_bold " TLS_FALLBACK_SCSV"; out " (RFC 7507)              "
+	echo | $OPENSSL s_client -connect $NODEIP:$PORT -no_tls1_2 -fallback_scsv > "$scsv" 2>&1
+	if grep -q "CONNECTED(00" "$scsv"; then
+		if grep -q "alert inappropriate fallback" "$scsv"; then
+			pr_green "not vulnerable (OK) - supported"
+			ret=0
+		else
+			pr_litered "VULNERABLE (NOT ok)"; out " - not supported\n"
+			ret=2
+		fi
+	else
+		pr_magentaln "test failed (couldn't connect)"
+		ret=3
+	fi
+
+	# Quick cleanup
+	rm -f "$scsv"
+}
 
 # Padding Oracle On Downgraded Legacy Encryption, in a nutshell: don't use CBC Ciphers in SSLv3
 ssl_poodle() {
@@ -3512,6 +3552,7 @@ initialize_globals() {
 	do_server_preference=false
 	do_spdy=false
 	do_ssl_poodle=false
+	do_tls_fallback_scsv=false
 	do_test_just_one=false
 	do_tls_sockets=false
 }
@@ -3538,6 +3579,7 @@ set_scanning_defaults() {
 	do_server_preference=true
 	do_spdy=true
 	do_ssl_poodle=true
+	do_tls_fallback_scsv=true
 	VULN_COUNT=10
 }
 
@@ -3547,7 +3589,7 @@ query_globals() {
 
 	for gbl in do_allciphers do_vulnerabilities do_beast do_breach do_ccs_injection do_cipher_per_proto do_crime \
      		do_freak do_logjam do_header do_heartbleed do_mx_all_ips do_pfs do_protocols do_rc4 do_renego \
-     		do_run_std_cipherlists do_server_defaults do_server_preference do_spdy do_ssl_poodle \
+     		do_run_std_cipherlists do_server_defaults do_server_preference do_spdy do_ssl_poodle do_tls_fallback_scsv \
      		do_test_just_one do_tls_sockets; do
 				[ "${!gbl}" == "true" ] && let true_nr++
 	done
@@ -3560,7 +3602,7 @@ debug_globals() {
 
 	for gbl in do_allciphers do_vulnerabilities do_beast do_breach do_ccs_injection do_cipher_per_proto do_crime \
      		do_freak do_logjam do_header do_heartbleed do_rc4 do_mx_all_ips do_pfs do_protocols do_rc4 do_renego \
-     		do_run_std_cipherlists do_server_defaults do_server_preference do_spdy do_ssl_poodle \
+     		do_run_std_cipherlists do_server_defaults do_server_preference do_spdy do_ssl_poodle do_tls_fallback_scsv \
      		do_test_just_one do_tls_sockets; do
 		printf "%-22s = %s\n" $gbl "${!gbl}"
 	done
@@ -3663,6 +3705,7 @@ startup() {
 				do_crime=true
 				do_breach=true
 				do_ssl_poodle=true
+				do_tls_fallback_scsv=true
 				do_freak=true
 				do_beast=true
 				do_rc4=true
@@ -3691,6 +3734,7 @@ startup() {
 				;;
 			-O|--poodle)
 				do_ssl_poodle=true
+				do_tls_fallback_scsv=true
 				let "VULN_COUNT++"
 				;;
 			-F|--freak)
@@ -3824,6 +3868,7 @@ lets_roll() {
 	${do_crime} && { crime; ret=$(($? + ret)); }
 	${do_breach} && { breach "$URL_PATH" ; ret=$(($? + ret)); }
 	${do_ssl_poodle} && { ssl_poodle; ret=$(($? + ret)); }
+	${do_tls_fallback_scsv} && { tls_fallback_scsv; ret=$(($? + ret)); }
 	${do_freak} && { freak; ret=$(($? + ret)); }
 	${do_logjam} && { logjam; ret=$(($? + ret)); }
 	${do_beast} && { beast; ret=$(($? + ret)); }