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Merge pull request #1731 from drwetter/winshock_cipher_improvements 

Further robustness checks for winshock (#1719)
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Dirk Wetter 2020-09-22 17:35:31 +02:00 committed by GitHub
parent 8d4042c6b6 3d22115d92
commit 3d07f55f56
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GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 131 additions and 44 deletions
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2
doc/testssl.1
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@ -385,7 +385,7 @@ Security headers (X\-Frame\-Options, X\-XSS\-Protection, Expect\-CT,\.\.\. , CSP
\fB\-L, \-\-lucky13\fR Checks for LUCKY13 vulnerability\. It checks for the presence of CBC ciphers in TLS versions 1\.0 \- 1\.2\.
.
.P
\fB\-WS, \-\-winshock\fR Checks for Winshock vulnerability\. It tests for absence of GCM ciphers which were introduced in the fix and correlates that with the server banner\.
\fB\-WS, \-\-winshock\fR Checks for Winshock vulnerability\. It tests for the absence of a lot of ciphers, some TLS extensions and ec curves which were introduced later in Windows\. In the end the server banner is being looked at\.
.
.P
\fB\-4, \-\-rc4, \-\-appelbaum\fR Checks which RC4 stream ciphers are being offered\.

2
doc/testssl.1.html
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@ -340,7 +340,7 @@ Also for multiple server certificates are being checked for as well as for the c
<p><code>-L, --lucky13</code> Checks for LUCKY13 vulnerability. It checks for the presence of CBC ciphers in TLS versions 1.0 - 1.2.</p>
<p><code>-WS, --winshock</code> Checks for Winshock vulnerability. It tests for absence of GCM ciphers which were introduced in the fix and correlates that with the server banner.</p>
<p><code>-WS, --winshock</code> Checks for Winshock vulnerability. It tests for the absence of a lot of ciphers, some TLS extensions and ec curves which were introduced later in Windows. In the end the server banner is being looked at.</p>
<p><code>-4, --rc4, --appelbaum</code> Checks which RC4 stream ciphers are being offered.</p>

2
doc/testssl.1.md
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@ -254,7 +254,7 @@ Also for multiple server certificates are being checked for as well as for the c
`-L, --lucky13` Checks for LUCKY13 vulnerability. It checks for the presence of CBC ciphers in TLS versions 1.0 - 1.2.
`-WS, --winshock` Checks for Winshock vulnerability. It tests for absence of GCM ciphers which were introduced in the fix and correlates that with the server banner.
`-WS, --winshock` Checks for Winshock vulnerability. It tests for the absence of a lot of ciphers, some TLS extensions and ec curves which were introduced later in Windows. In the end the server banner is being looked at.
`-4, --rc4, --appelbaum` Checks which RC4 stream ciphers are being offered.

169
testssl.sh
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@ -759,6 +759,10 @@ debugme() {
[[ "$DEBUG" -ge 2 ]] && "$@"
return 0
}
debugme1() {
[[ "$DEBUG" -ge 1 ]] && "$@"
return 0
}
hex2dec() {
echo $((16#$1))
@ -7436,9 +7440,14 @@ determine_tls_extensions() {
[[ $success -eq 0 ]] && extract_new_tls_extensions $TMPFILE
tmpfile_handle ${FUNCNAME[0]}.txt
fi
# Keep it "on file" for debugging purposes
debugme1 safe_echo "$TLS_EXTENSIONS" >"$TEMPDIR/$NODE.$NODEIP.tls_extensions.txt"
return $success
}
extract_certificates() {
local version="$1"
local savedir
@ -8774,7 +8783,7 @@ certificate_info() {
prln_italic "$(out_row_aligned_max_width "$all_san" "$indent " $TERM_WIDTH)"
fileout "${jsonID}${json_postfix}" "INFO" "$all_san"
else
if [[ $SERVICE == "HTTP" ]] || "$ASSUME_HTTP"; then
if [[ $SERVICE == HTTP ]] || "$ASSUME_HTTP"; then
pr_svrty_high "missing (NOT ok)"; outln " -- Browsers are complaining"
fileout "${jsonID}${json_postfix}" "HIGH" "No SAN, browsers are complaining"
else
@ -8869,7 +8878,7 @@ certificate_info() {
pr_svrty_high "$trustfinding"
trust_sni_finding="HIGH"
elif ( [[ $trust_sni -eq 4 ]] || [[ $trust_sni -eq 8 ]] ); then
if [[ $SERVICE == "HTTP" ]] || "$ASSUME_HTTP"; then
if [[ $SERVICE == HTTP ]] || "$ASSUME_HTTP"; then
# https://bugs.chromium.org/p/chromium/issues/detail?id=308330
# https://bugzilla.mozilla.org/show_bug.cgi?id=1245280
# https://www.chromestatus.com/feature/4981025180483584
@ -8932,7 +8941,7 @@ certificate_info() {
fi
if [[ -n "$sni_used" ]] || [[ $trust_nosni -eq 0 ]] || ( [[ $trust_nosni -ne 4 ]] && [[ $trust_nosni -ne 8 ]] ); then
outln "$trustfinding_nosni"
elif [[ $SERVICE == "HTTP" ]] || "$ASSUME_HTTP"; then
elif [[ $SERVICE == HTTP ]] || "$ASSUME_HTTP"; then
prln_svrty_high "$trustfinding_nosni"
else
prln_svrty_medium "$trustfinding_nosni"
@ -10150,6 +10159,8 @@ run_fs() {
fi
CURVES_OFFERED="$curves_offered"
CURVES_OFFERED=$(strip_trailing_space "$CURVES_OFFERED")
# Keep it "on file" for debugging purposes
debugme1 safe_echo "$CURVES_OFFERED" >"$TEMPDIR/$NODE.$NODEIP.curves_offered.txt"
# find out what groups are supported.
if "$using_sockets" && ( "$fs_tls13_offered" || "$ffdhe_offered" ); then
@ -13333,6 +13344,7 @@ parse_tls_serverhello() {
[[ $DEBUG -ge 1 ]] && tmpfile_handle ${FUNCNAME[0]}.txt
return 1
fi
# https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml
case $extension_type in
0000) tls_extensions+="TLS server extension \"server name\" (id=0), len=$extension_len\n" ;;
0001) tls_extensions+="TLS server extension \"max fragment length\" (id=1), len=$extension_len\n" ;;
@ -17447,26 +17459,33 @@ run_beast(){
# This vulnerability affected all SChannel services -- most notably RDP (port 3398 normally). See
# https://support.microsoft.com/en-us/help/2992611/ms14-066-vulnerability-in-schannel-could-allow-remote-code-execution-n
# and http://www.securitysift.com/exploiting-ms14-066-cve-2014-6321-aka-winshock for "exploiting"/crashing lsass.exe.
# What we do here is giving a strong hint.
#
# What we do here is giving a hint, as with the Rollup patch MS introduced later is to supply the additional ciphers
# First we check whether TLS 1.3 is available. Then with the fix MS introduced came additional ciphers
# TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 TLS_RSA_WITH_AES_256_GCM_SHA384 TLS_RSA_WITH_AES_128_GCM_SHA256
# = DHE-RSA-AES256-GCM-SHA384 DHE-RSA-AES128-GCM-SHA256 AES256-GCM-SHA384 AES128-GCM-SHA256.
# We check for those (in sockets only to avoid overhead) and for port 443 we also grab the server banner to be more sure.
# Also we check whether TLS 1.3 is available and some ciphers (ARIA, CCM, CAMELLIA and CHACHAPOLY). Those ciphers could
# also be retrieved from our array TLS_CIPHER_RFC_NAME[i] and using TLS_CIPHER_HEXCODE[i]. The latter will be done later.
# We also check for the absence of ciphers which came in way later (ECDHE-RSA-AES128-GCM-SHA256 / ECDHE-RSA-AES256-GCM-SHA384), or
# more ciphers like ARIA, CCM, CAMELLIA and CHACHAPOLY. (Those ciphers could also be retrieved from our array TLS_CIPHER_RFC_NAME[i]
# and using TLS_CIPHER_HEXCODE[i]. We may want to # do that later. We check for all this in sockets only to avoid overhead.)
# Then we check for absence of elliptical curves and TLS extensions.
# That all should minimize false # positives because of middle boxes, proxies and later Windows versions.
# The last straw then is to check for webserver banners (http.sys, IIS/8.0 and IIS/8.5).
#
run_winshock() {
local ws_ciphers_hex='00,9F, 00,9D, 00,9E, 00,9C'
local wsfixed_ciphers='00,9F, 00,9D, 00,9E, 00,9C'
local aria_ciphers='C0,3D,C0,3F,C0,41,C0,43,C0,45,C0,47,C0,49,C0,4B,C0,4D,C0,4F,C0,51,C0,53,C0,55,C0,57,C0,59,C0,5B,C0,5D,C0,5F,C0,61,C0,63,C0,65,C0,67,C0,69,C0,6B,C0,6D,C0,6F,C0,71,C0,3C,C0,3E,C0,40,C0,42,C0,44,C0,46,C0,48,C0,4A,C0,4C,C0,4E,C0,50,C0,52,C0,54,C0,56,C0,58,C0,5A,C0,5C,C0,5E,C0,60,C0,62,C0,64,C0,66,C0,68,C0,6A,C0,6C,C0,6E,C0,70'
local camellia_ciphers='C0,9B,C0,99,C0,97,C0,95,C0,77,C0,73,00,C4,00,C3,00,C2,00,C1,00,88,00,87,00,86,00,85,00,C5,00,89,C0,79,C0,75,00,C0,00,84,C0,7B,C0,7D,C0,7F,C0,81,C0,83,C0,85,C0,87,C0,89,C0,8B,C0,8D,C0,8F,C0,91,C0,93,C0,76,C0,72,00,BE,00,BD,00,BC,00,BB,00,45,00,44,00,43,00,42,00,BF,00,46,C0,78,C0,74,00,BA,00,41,C0,9A,C0,98,C0,96,C0,94,C0,7A,C0,7C,C0,7E,C0,80,C0,82,C0,84,C0,86,C0,88,C0,8A,C0,8C,C0,8E,C0,90,C0,92'
local chacha_ccm_ciphers='CC,14,CC,13,CC,15,CC,A9,CC,A8,CC,AA,C0,AF,C0,AD,C0,A3,C0,9F,CC,AE,CC,AD,CC,AC,C0,AB,C0,A7,C0,A1,C0,9D,CC,AB,C0,A9,C0,A5,16,B7,16,B8,13,04,13,05,C0,AE,C0,AC,C0,A2,C0,9E,C0,AA,C0,A6,C0,A0,C0,9C,C0,A8,C0,A4'
# TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 / TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 = ECDHE-RSA-AES128-GCM-SHA256 / ECDHE-RSA-AES256-GCM-SHA384
# came in Server 2016, see https://notsomany.com/2016/08/26/achieve-a-on-sslabs-iis-8-5-windows-2012-r2/
# https://docs.microsoft.com/en-us/windows/win32/secauthn/cipher-suites-in-schannel
local more_excluded_ciphers='C0,2f, C0,30'
local more_excluded_ciphers='C0,2F, C0,30'
# These are the three NIST curves allowed only. Keep in mind prime256v1=secp256r1 and MS labels them as P256, P384 and P521
local allowed_curves="prime256v1 secp384r1 secp521r1"
local curve="" tls_ext=""
local -i sclient_success=0
local is_iis8=true
local server_banner=""
local check_patches=" - check patches locally to confirm"
local cve="CVE-2014-6321"
local cwe="CWE-94"
local jsonID="winshock"
@ -17481,17 +17500,14 @@ run_winshock() {
if [[ "$(has_server_protocol "tls1_3")" -eq 0 ]] ; then
# There's no MS server supporting TLS 1.3. Winshock was way back in time
pr_svrty_best "not vulnerable (OK)"
debugme echo " - TLS 1.3 found"
debugme1 echo " - TLS 1.3 found"
fileout "$jsonID" "OK" "not vulnerable " "$cve" "$cwe"
outln
return 0
fi
# Next we weed out is whether we run HTTP or RDP (on standard port)
if [[ $SERVICE != HTTP ]] && [[ $PORT != 3389 ]]; then
prln_svrty_best "not vulnerable (OK) - no HTTP or RDP"
fileout "$jsonID" "OK" "not vulnerable - no HTTP or RDP" "$cve" "$cwe"
return 0
if ( [[ "$STARTTLS_PROTOCOL" =~ ldap ]] || [[ "$STARTTLS_PROTOCOL" =~ irc ]] ); then
prln_local_problem "STARTTLS/$STARTTLS_PROTOCOL and --ssl-native collide here"
return 1
fi
# Now we check whether any CAMELLIA, ARIA, CCM or CHACHA cipher is available.
@ -17499,31 +17515,25 @@ run_winshock() {
tls_sockets "03" "${aria_ciphers},${chacha_ccm_ciphers}, 00,ff"
sclient_success=$?
if [[ $sclient_success -eq 0 ]] || [[ "$sclient_success" -eq 2 ]]; then
pr_svrty_best "not vulnerable (OK)"
debugme echo " - ARIA, CHACHA or CCM ciphers found"
pr_svrty_best "not vulnerable (OK)" ; outln " - ARIA, CHACHA or CCM ciphers found"
fileout "$jsonID" "OK" "not vulnerable " "$cve" "$cwe"
outln
return 0
fi
tls_sockets "03" "${camellia_ciphers},${more_excluded_ciphers}, 00,ff"
sclient_success=$?
if [[ $sclient_success -eq 0 ]] || [[ "$sclient_success" -eq 2 ]]; then
pr_svrty_best "not vulnerable (OK)"
debugme echo " - CAMELLIA or ECDHE_RSA GCM ciphers found"
pr_svrty_best "not vulnerable (OK)"; outln " - CAMELLIA or ECDHE_RSA GCM ciphers found"
fileout "$jsonID" "OK" "not vulnerable " "$cve" "$cwe"
outln
return 0
fi
# Now we have RDP and HTTP left and need to check the fixed ciphers
tls_sockets "03" "${ws_ciphers_hex}, 00,ff"
# Now we need to check the fixed ciphers
tls_sockets "03" "${wsfixed_ciphers}, 00,ff"
sclient_success=$?
if [[ $sclient_success -eq 0 ]] || [[ "$sclient_success" -eq 2 ]]; then
# has rollup ciphers
pr_svrty_best "not vulnerable (OK)"
debugme echo " - GCM rollup ciphers found"
pr_svrty_best "not vulnerable (OK)"; outln " - GCM rollup ciphers found"
fileout "$jsonID" "OK" "not vulnerable" "$cve" "$cwe"
outln
return 0
elif [[ $sclient_success -ne 1 ]]; then
prln_warning "check failed, connect problem"
@ -17531,12 +17541,71 @@ run_winshock() {
return 1
fi
# Basic idea: https://en.wikipedia.org/wiki/Comparison_of_TLS_implementations#Supported_elliptic_curves
# [[ -z "$CURVES_OFFERED" ]] && sub_check_curves
if [[ -n "$CURVES_OFFERED" ]]; then
# Check whether there are any additional curves besides $allowed_curves
for curve in $CURVES_OFFERED; do
if ! [[ $allowed_curves =~ $curve ]]; then
pr_svrty_best "not vulnerable (OK)"; outln " - curve $curve detected"
fileout "$jsonID" "OK" "not vulnerable - curve $curve detected" "$cve" "$cwe"
return 0
fi
done
fi
#FIXME: The catch is that when a user didn't invoke run_fs() before, this wasn't processed + CURVES_OFFERED
# is empty. So we could call it like above but need to move curves detection into a seperate function
# (~ sub_check_curves) which is some work. But also for the sake of clean code this needs to be done.
[[ -z "$TLS_EXTENSIONS" ]] && determine_tls_extensions
# Basis of the following https://en.wikipedia.org/wiki/Comparison_of_TLS_implementations#Extensions
# Our standard: https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml
# According to Wikipedia above these are the ones which can be detected unders version of Windows
# Secure Renegotiation, Server Name Indication, Certificate Status Request, Supplemental Data, Extended Master Secret, ALPN
# supplemental_data(23) (RFC 4680) seems to have been overwritten by extended master secret(23) RFC 7627
# local -a allowed_tls_ext=("server name" "status_request" "extended master secret" "application layer protocol negotiation")
# Instead we rather focus on the ones which according to that source weren't available
# Encrypt-then-MAC, Maximum Fragment Length, Keying Material Exporter, TLS Fallback SCSV, ClientHello Padding
# Padding is client side. Don't know what they mean by the fallback SCSV. That is not an extension
local -a forbidden_tls_ext=("encrypt-then-mac" "max fragment length")
# Open whether ec_point_formats, supported_groups(=elliptic_curves), heartbeat are supported under windows <=2012
# key_share and supported_versions are extensions which came with TLS 1.3. We checked the protocol before.
if [[ -n "$TLS_EXTENSIONS" ]]; then
# Check whether there are any TLS extension which should not be available under <= Windows 2012 R2
for tls_ext in $TLS_EXTENSIONS; do
# We use the whole array, got to be careful when the array becomes bigger (unintented match)
if [[ ${forbidden_tls_ext[@]} =~ $tls_ext ]]; then
pr_svrty_best "not vulnerable (OK)"; outln " - TLS extension $tls_ext detected"
fileout "$jsonID" "OK" "not vulnerable - TLS extension $tls_ext detected" "$cve" "$cwe"
return 0
fi
done
fi
# More would be possible if we look @ the following:
# See also https://github.com/cisco/joy/blob/master/fingerprinting/resources/fingerprint_db.json.gz
# https://resources.sei.cmu.edu/asset_files/Presentation/2019_017_001_539902.pdf
# https://raw.githubusercontent.com/cisco/joy/master/doc/using-joy-fingerprinting-00.pdf
# Now the solid determination more or less done. What's left now is to detect the service
# and perform an educated guess.
# Next we weed out is whether we run HTTP or RDP (on standard port).
# Using the experimental flag we can test it also on other ports / services
if [[ $SERVICE != HTTP ]] && [[ $PORT != 3389 ]] && ! "$EXPERIMENTAL"; then
pr_svrty_best "not vulnerable (OK)"; outln " - no HTTP or RDP"
fileout "$jsonID" "OK" "not vulnerable - no HTTP or RDP" "$cve" "$cwe"
return 0
fi
if [[ $SERVICE != HTTP ]] && [[ $PORT == 3389 ]]; then
# We take a guess here for RDP as we don't have a banner
out "probably "
pr_svrty_critical "vulnerable (NOT ok)"
outln " - check patches locally to confirm"
fileout "${jsonID}" "CRITICAL" "probably vulnerable (NOT OK). Check patches locally to confirm"
# We take a security guess here (better safe than sorry) for RDP as we don't have a banner
out "probably "; pr_svrty_critical "vulnerable (NOT ok)"; outln "$check_patches"
fileout "${jsonID}" "CRITICAL" "probably vulnerable (NOT OK) $check_patches"
return 0
fi
@ -17547,6 +17616,9 @@ run_winshock() {
server_banner="$(grep -Eai '^Server:' $HEADERFILE)"
elif [[ -s "$TEMPDIR/$NODEIP.service_detection.txt" ]]; then
server_banner="$(grep -Eai '^Server:' "$TEMPDIR/$NODEIP.service_detection.txt")"
elif "$EXPERIMENTAL"; then
# If testing e.g. an SMTP server
:
else
# We can't use run_http_header here as it messes up the screen. We could automatically
# run it when --winshock is requested though but this should suffice here.
@ -17556,15 +17628,30 @@ run_winshock() {
fi
if [[ $server_banner =~ Microsoft-IIS\/8.5 ]]; then
# Windows 2012 R2 is less likely than Windows 2012
out "probably "
pr_svrty_critical "vulnerable (NOT ok)"
outln " - check patches locally to confirm"
fileout "${jsonID}" "CRITICAL" "probably vulnerable (NOT OK). Check patches locally to confirm"
out "probably "; pr_svrty_critical "vulnerable (NOT ok)"; outln "$check_patches"
fileout "${jsonID}" "CRITICAL" "probably vulnerable (NOT OK) $check_patches"
elif [[ $server_banner =~ Microsoft-IIS\/8.0 ]]; then
out "likely "
pr_svrty_critical "VULNERABLE (NOT ok)"
outln " - check patches locally to confirm"
fileout "${jsonID}" "CRITICAL" "likely vulnerable (NOT OK). Check patches locally to confirm"
out "likely "; pr_svrty_critical "VULNERABLE (NOT ok)"; outln "$check_patches"
fileout "${jsonID}" "CRITICAL" "likely vulnerable (NOT OK) $check_patches"
elif [[ $server_banner =~ Microsoft-HTTPAPI\/2.0 ]]; then
# This is http.sys. It may or may not indicate a 2012 server. IIS is not yet configured though.
# So we have a peek on port 80
http_get $NODE "$TEMPDIR/$NODE.$NODEIP.http-header.txt"
server_banner="$(grep -Eai '^Server:' $TEMPDIR/$NODE.$NODEIP.http-header.txt)"
if [[ $server_banner =~ Microsoft-IIS\/8.5 ]]; then
out "probably "; pr_svrty_critical "vulnerable (NOT ok)"; outln "$check_patches"
fileout "${jsonID}" "CRITICAL" "probably vulnerable (NOT OK) $check_patches"
elif [[ $server_banner =~ Microsoft-IIS\/8.0 ]]; then
out "likely "; pr_svrty_critical "VULNERABLE (NOT ok)"; outln "$check_patches"
fileout "${jsonID}" "CRITICAL" "likely vulnerable (NOT OK) $check_patches"
else
out "likely "; prln_svrty_best "not vulnerable (OK)"
fileout "$jsonID" "OK" "not vulnerable" "$cve" "$cwe"
outln
fi
elif "$EXPERIMENTAL"; then
out "seems "; pr_svrty_critical "vulnerable (NOT ok)"; outln "$check_patches"
fileout "${jsonID}" "CRITICAL" "seems vulnerable (NOT OK) $check_patches"
else
pr_svrty_best "not vulnerable (OK)"
outln " - doesn't seem to be IIS 8.x"