add support for testing supported curves

since early versions of 1.0.2 openssl supports -curves command line
option, it allows us to set the curves advertised as supported

use the same approach to testing: advertise all, check what server
accepts, remove the accepted from list, repeat. When server aborts
connection or selects non ECC cipher, we know that we've tested all.

cipherscan

@@ -61,6 +61,7 @@ TIMEOUT=30
 # trust anchors are stored
 CAPATH=""
 SAVECRT=""
+TEST_CURVES="False"
 unset known_certs
 declare -A known_certs
 unset cert_checksums
@@ -99,6 +100,7 @@ Use one of the options below:
 -j | --json         Output results in JSON format.
 -o | --openssl      path/to/your/openssl binary you want to use.
 --savecrt           path where to save untrusted and leaf certificates
+--curves            test ECC curves supported by server (req. OpenSSL 1.0.2)
 -v | --verbose      Increase verbosity.
 
 The rest of the arguments will be interpreted as openssl s_client argument.
@@ -529,6 +531,25 @@ display_results_in_terminal() {
     else
         echo "Client side cipher ordering"
     fi
+
+    if [[ $TEST_CURVES == "True" ]]; then
+        if [[ -n $supported_curves ]]; then
+            echo
+            local i=0
+            (echo "prio curve"
+            for curve in ${supported_curves//,/ }; do
+                i=$((i+1))
+                echo "$i $curve"
+            done) | column -t
+            echo
+            if [[ $fallback_supported == True ]]; then
+                echo "Server does fallback on unsupported curves"
+            else
+                echo "Server doesn't fallback on unsupported curves"
+            fi
+            echo "$curves_ordering side curve ordering"
+        fi
+    fi
 }
 
 display_results_in_json() {
@@ -553,7 +574,14 @@ display_results_in_json() {
         echo -n "\"pfs\":\"$pfs\"}"
         ctr=$((ctr+1))
     done
-    echo ']}'
+    echo -n ']'
+    if [[ -n $supported_curves ]]; then
+        echo -n ","
+        echo -n "\"curve_fallback\":\"$fallback_supported\","
+        echo -n "\"curve_ordering\":\"$curves_ordering\","
+        echo -n "\"curve\":[\"${supported_curves//,/\",\"}\"]"
+    fi
+    echo '}'
 }
 
 test_serverside_ordering() {
@@ -609,6 +637,248 @@ test_serverside_ordering() {
     fi
 }
 
+test_ecc_curves() {
+    # openssl formated list of curves that will cause server to select ECC suite
+    local ecc_ciphers=""
+    # names of all curves supported in TLS (as supported by openssl)
+    local curves=()
+    # alternative names for curves in TLS (as returned by openssl s_client or
+    # as specified in standard)
+    local curve_names=()
+    # "True" if server supports ciphers that don't use ECC at a lower priority
+    local fallback_available="False"
+
+    # return variable: list of curves supported by server, in order
+    supported_curves=""
+    # return variable: whatever a server will fall back to non ECC suite when
+    # client doesn't advertise support for curves the server needs
+    fallback_supported="False"
+    # return variable: check if server uses server side or client side ordering
+    # for curves
+    curves_ordering="server"
+
+    # get ciphers that will cause server to select suite that uses ECC, if most
+    # preferred ciphers do not, exclude them from list
+    for pref in "${cipherspref[@]}"; do
+        # get first value from space separated array
+        cipher=($pref)
+
+        # ECDH uses curve from certificate, so no way to negotiate it, the two
+        # below are ephemeral so they can select the curve independent of cert
+        if [[ $cipher =~ ECDHE ]] || [[ $cipher =~ AECDH ]]; then
+            # colon on end of string is ignored by openssl
+            ecc_ciphers+="${cipher}:"
+        elif [[ -n $ecc_ciphers ]]; then
+            # add fallback ciphers
+            ecc_ciphers+="${cipher}:"
+            fallback_available="True"
+        fi
+    done
+
+    if [[ -z $ecc_ciphers ]]; then
+        verbose "Server does not support ephemeral ECC"
+        return
+    fi
+
+    verbose "ECC curves testing, cipher preference: $ecc_ciphers"
+
+    # only some curves have defined TLS code points, so no use parsing openssl
+    # output checking what it supports, see
+    # http://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml#tls-parameters-8
+    curves=(sect163k1 # K-163
+          sect163r1
+          sect163r2 # B-163
+          sect193r1
+          sect193r2
+          sect233k1 # K-233
+          sect233r1 # B-233
+          sect239k1
+          sect283k1 # K-283
+          sect283r1 # B-283
+          sect409k1 # K-409
+          sect409r1 # B-409
+          sect571k1 # K-571
+          sect571r1 # B-571
+          secp160k1
+          secp160r1
+          secp160r2
+          secp192k1
+          prime192v1 # P-192 secp192r1
+          secp224k1
+          secp224r1 # P-224
+          secp256k1
+          prime256v1 # P-256 secp256r1
+          secp384r1 # P-384
+          secp521r1 # P-521
+          brainpoolP256r1
+          brainpoolP384r1
+          brainpoolP512r1)
+
+    # many curves have alternative names, save those too
+    curve_names=("sect163k1 K-163"
+          "sect163r1"
+          "sect163r2 B-163"
+          "sect193r1"
+          "sect193r2"
+          "sect233k1 K-233"
+          "sect233r1 B-233"
+          "sect239k1"
+          "sect283k1 K-283"
+          "sect283r1 B-283"
+          "sect409k1 K-409"
+          "sect409r1 B-409"
+          "sect571k1 K-571"
+          "sect571r1 B-571"
+          "secp160k1"
+          "secp160r1"
+          "secp160r2"
+          "secp192k1"
+          "prime192v1 P-192 secp192r1"
+          "secp224k1"
+          "secp224r1 P-224"
+          "secp256k1"
+          "prime256v1 P-256 secp256r1"
+          "secp384r1 P-384"
+          "secp521r1 P-521"
+          "brainpoolP256r1"
+          "brainpoolP384r1"
+          "brainpoolP512r1")
+
+    OLDIFS="$IFS"
+    IFS=':'
+    verbose "Will test following curves: ${curves[*]}"
+    IFS="$OLDIFS"
+
+    # prepare the ssl command we'll be using
+    local sslcommand=""
+    sslcommand="$TIMEOUTBIN $TIMEOUT $OPENSSLBIN s_client"
+    if [ -n "$CAPATH" ]; then
+        sslcommand+=" -CApath $CAPATH -showcerts"
+    elif [ -e "$CACERTS" ]; then
+        sslcommand+=" -CAfile $CACERTS"
+    fi
+    sslcommand+=" -status $SCLIENTARGS -connect $TARGET -cipher $ecc_ciphers"
+
+    #
+    # here we use the same logic as with detecting cipher suites: first
+    # advertise all curves as supported, then remove curves one by one until we
+    # either get a fallback to a non ECC cipher, we run of curves or server
+    # tries to negotiate a curve we didn't advertise
+    #
+    while [[ ${#curves[@]} -gt 0 ]]; do
+        OLDIFS="$IFS"
+        IFS=':'
+        local test_curves="${curves[*]}"
+        IFS="$OLDIFS"
+        verbose "Testing $test_curves"
+
+        ratelimit
+        local tmp=$(echo Q | $sslcommand -curves $test_curves 2>/dev/null)
+        parse_openssl_output <<<"$tmp"
+
+        if [[ -z $current_protocol || $current_cipher == "(NONE)" \
+            || $current_cipher == '0000' ]]; then
+                # server aborted connection
+                if [[ $fallback_available == "True" ]]; then
+                    fallback_supported="False"
+                else
+                    fallback_supported="unknown"
+                fi
+                break
+        else
+            # server accepted connection
+            local ephem_data=(${current_pfs//,/ })
+
+            if [[ ${ephem_data[0]} =~ ECDH ]]; then
+                # ok, we got an ECC connection, now, what curve did we get
+                for id in "${!curves[@]}"; do
+                    # compare to alternative names
+                    if [[ ${curve_names[$id]} =~ ${ephem_data[1]} ]]; then
+                        if [[ -n $supported_curves ]]; then
+                            supported_curves+=","
+                        fi
+                        supported_curves+="${curves[$id]}"
+                        verbose "Server selected ${ephem_data[1]}, a.k.a ${curves[$id]}"
+                        # ok, we know it's supported, remove it from set of offered ones
+                        unset curves[$id]
+                        break
+                    fi
+                done
+
+            else
+                verbose "Server fell back to $current_cipher"
+                # ok, we got a fallback
+                fallback_supported="True"
+                break
+            fi
+        fi
+
+        [ "$OUTPUTFORMAT" == "terminal" ] && [ $DEBUG -lt 1 ] && echo -n '.'
+    done
+
+    # don't penalize servers that will negotiate all curves we know of...
+    if [[ ${#curves[@]} -eq 0 ]]; then
+        fallback_supported="unknown"
+    fi
+
+    #
+    # check if curves ordering is server of client side
+    #
+
+    local tmp_curves=(${supported_curves//,/ })
+    verbose "Server supported curves: ${tmp_curves[@]}"
+
+    # server supports just one or none, so it effectively uses server side
+    # ordering (as it dictates what curves client must support)
+    if [ ${#tmp_curves[@]} -lt 2 ]; then
+        curves_ordering="server"
+    else
+        # server supports at least 2 curves, rotate their order, see if
+        # selected changes
+        test_curves=""
+        most_wanted="${tmp_curves[${#tmp_curves[@]}-1]}"
+        for (( i=${#tmp_curves[@]}-1; i>0; i--)); do
+            test_curves+="${tmp_curves[$i]}:"
+        done
+        test_curves+="${tmp_curves[0]}"
+
+        verbose "Testing ordering with $sslcommand -curves $test_curves"
+        ratelimit
+        local tmp=$(echo Q | $sslcommand -curves $test_curves 2>/dev/null)
+        parse_openssl_output <<<"$tmp"
+
+        if [[ -z $current_protocol || $current_cipher == "(NONE)" \
+            || $current_cipher == '0000' ]]; then
+                fallback_supported="order-specific"
+                verbose "Server aborted connection"
+        else
+            local ephem_data=(${current_pfs//,/ })
+            verbose "Server selected $current_cipher with $current_pfs"
+            verbose "ephem_data: ${ephem_data[@]}"
+
+            if [[ ${ephem_data[0]} =~ ECDH ]]; then
+                verbose "Server did select ${ephem_data[1]} curve"
+                curves_ordering="inconclusive-${ephem_data[1]}"
+                for id in "${!curve_names[@]}"; do
+                    if [[ ${curve_names[$id]} =~ ${ephem_data[1]} ]]; then
+                        local canonic_name=(${curve_names[$id]})
+                        if [[ ${canonic_name[0]} == $most_wanted ]]; then
+                            curves_ordering="client"
+                            break
+                        else
+                            curves_ordering="server"
+                            break
+                        fi
+                    fi
+                done
+            else
+                # some servers downgrade to non ECDH when curve order is changed
+                curves_ordering="inconclusive-noecc"
+            fi
+        fi
+    fi
+}
+
 # If no options are given, give usage information and exit (with error code)
 if [ $# -eq 0 ]; then
    usage;
@@ -664,6 +934,10 @@ do
             SAVECRT="$2"
             shift 2
             ;;
+        --curves)
+            TEST_CURVES="True"
+            shift 1
+            ;;
         --) # End of all options
             shift
             break
@@ -723,6 +997,10 @@ get_cipher_pref $CIPHERSUITE
 
 test_serverside_ordering
 
+if [[ $TEST_CURVES == "True" ]]; then
+    test_ecc_curves
+fi
+
 if [ "$OUTPUTFORMAT" == "json" ]; then
     display_results_in_json
 else

top1m/parse_results.py

@@ -72,6 +72,9 @@ handshakestats = defaultdict(int)
 keysize = defaultdict(int)
 sigalg = defaultdict(int)
 tickethint = defaultdict(int)
+eccfallback = defaultdict(int)
+eccordering = defaultdict(int)
+ecccurve = defaultdict(int)
 ocspstaple = defaultdict(int)
 dsarsastack = 0
 total = 0
@@ -86,6 +89,9 @@ for r,d,flist in os.walk(path):
         tempdsakeystats = {}
         tempsigstats = {}
         tempticketstats = {}
+        tempeccfallback = "unknown"
+        tempeccordering = "unknown"
+        tempecccurve = {}
         """ supported ciphers by the server under scan """
         tempcipherstats = {}
         ciphertypes = 0
@@ -141,6 +147,17 @@ for r,d,flist in os.walk(path):
             if len(results['ciphersuite']) < 1:
                 continue
 
+            """ save ECC curve stats """
+            if 'curve_fallback' in results:
+                tempeccfallback = results['curve_fallback']
+            if 'curve_ordering' in results:
+                tempeccordering = results['curve_ordering']
+            if 'curve' in results:
+                for curve in results['curve']:
+                    tempecccurve[curve] = 1
+                if len(results['curve']) == 1:
+                    tempecccurve[curve + ' Only'] = 1
+
             """ loop over list of ciphers """
             for entry in results['ciphersuite']:
 
@@ -329,6 +346,11 @@ for r,d,flist in os.walk(path):
         for s in tempticketstats:
             tickethint[s] += 1
 
+        eccfallback[tempeccfallback] += 1
+        eccordering[tempeccordering] += 1
+        for s in tempecccurve:
+            ecccurve[s] += 1
+
         if ocsp_stapling is None:
             ocspstaple['Unknown'] += 1
         elif ocsp_stapling:
@@ -518,6 +540,24 @@ for stat in sorted(pfsstats):
         pfspercent = round(pfsstats[stat] / handshakestats['DHE'] * 100, 4)
     sys.stdout.write(stat.ljust(25) + " " + str(pfsstats[stat]).ljust(10) + str(percent).ljust(9) + str(pfspercent) + "\n")
 
+print("\nSupported ECC curves      Count     Percent ")
+print("-------------------------+---------+--------")
+for stat in sorted(ecccurve):
+    percent = round(ecccurve[stat] / total * 100, 4)
+    sys.stdout.write(stat.ljust(25) + " " + str(ecccurve[stat]).ljust(10) + str(percent).ljust(9) + "\n")
+
+print("\nUnsupported curve fallback     Count     Percent ")
+print("------------------------------+---------+--------")
+for stat in sorted(eccfallback):
+    percent = round(eccfallback[stat] / total * 100,4)
+    sys.stdout.write(stat.ljust(30) + " " + str(eccfallback[stat]).ljust(10) + str(percent).ljust(9) + "\n")
+
+print("\nECC curve ordering        Count     Percent ")
+print("-------------------------+---------+--------")
+for stat in sorted(eccordering):
+    percent = round(eccordering[stat] / total * 100, 4)
+    sys.stdout.write(stat.ljust(25) + " " + str(eccordering[stat]).ljust(10) + str(percent).ljust(9) + "\n")
+
 print("\nTLS session ticket hint   Count     Percent ")
 print("-------------------------+---------+--------")
 for stat in natural_sort(tickethint):

top1m/testtop1m.sh

@@ -68,7 +68,7 @@ function scan_host() {
     if [ $? -gt 0 ]; then
         return
     fi
-    ../cipherscan --capath ca_files --saveca --savecrt certs --delay 2 -json -servername $1 $2:443 > results/$1@$2
+    ../cipherscan --capath ca_files --saveca --curves --savecrt certs --delay 2 -json -servername $1 $2:443 > results/$1@$2
 }
 
 function scan_host_no_sni() {
@@ -80,7 +80,7 @@ function scan_host_no_sni() {
     if [ $? -gt 0 ]; then
         return
     fi
-    ../cipherscan --capath ca_files --saveca --savecrt certs --delay 2 -json $1:443 > results/$1
+    ../cipherscan --capath ca_files --saveca --curves --savecrt certs --delay 2 -json $1:443 > results/$1
 }
 
 function scan_hostname() {