Extract Client Auth CA list

This commit is a first step towards addressing #1709. It attempts to determime whether certificate-based client authentication is (1) not requested, (2) optional, or (3) required. If it is either optional or required, then it extracts the list of CA names (DNs) that the server sends in its CertificateRequest message.

The code for extracting the CA list from the CertificateRequest message seems to be working correctly. However, this commit is incomplete for a couple of reasons. First, it does not produce any new output, it just collects the information. Second, sclient_auth() needs some work.

The current sclient_auth() simply returns 0 if $OPENSSL returned 0. This may be okay if only trying to determine whether certificate-based client authentication is required. However, if it is optional, then the output will include "CertificateRequest", but $OPENSSL will return 0, since the connection was successful even though the client did not provide a certificates.

If $OPENSSL does not return 0, then sclient_auth() checks whether Master-Key is present. This works for TLS 1.2 and earlier, but not for TLS 1.3. So, sclient_auth() needs to be updated to work correctly with TLS 1.3.

The modified version of sclient_auth() will set CLIENT_AUTH and CLIENT_AUTH_CA_LIST for any version of TLS, but the remaining part of the code needs work. As I am not clear on the reason for this code, I need some help with it. Why does the code only look for "CertificateRequest" if "Master-Key" is present? Why is there a check for Session-ID in a function that is supposed to just be checking for client authentication. Why is CLIENT_AUTH set to false if SESSION-ID is absent (this is a no-op since CLIENT_AUTH would already have been false)?
This commit is contained in:
David Cooper 2020-09-03 08:27:32 -04:00
parent bf24c80174
commit 44787d6bcb

View File

@ -277,7 +277,8 @@ declare -r ALPN_PROTOs="h2 spdy/3.1 http/1.1 grpc-exp h2-fb spdy/1 spdy/2 spdy/3
TEMPDIR=""
TMPFILE=""
ERRFILE=""
CLIENT_AUTH=false
CLIENT_AUTH="none"
CLIENT_AUTH_CA_LIST=""
TLS_TICKETS=false
NO_SSL_SESSIONID=false
CERT_COMPRESSION=${CERT_COMPRESSION:-false} # secret flag to set in addition to --devel for certificate compression
@ -2223,7 +2224,7 @@ s_client_options() {
service_detection() {
local -i was_killed
if ! "$CLIENT_AUTH"; then
if [[ "$CLIENT_AUTH" != require ]]; then
if ! "$HAS_TLS13" && "$TLS13_ONLY"; then
# Using sockets is a lot slower than using OpenSSL, and it is
# not as reliable, but if OpenSSL can't connect to the server,
@ -2272,7 +2273,7 @@ service_detection() {
out " $SERVICE, thus skipping HTTP specific checks"
fileout "${jsonID}" "INFO" "$SERVICE, thus skipping HTTP specific checks"
;;
*) if "$CLIENT_AUTH"; then
*) if [[ "$CLIENT_AUTH" == require ]]; then
out " certificate-based authentication => skipping all HTTP checks"
echo "certificate-based authentication => skipping all HTTP checks" >$TMPFILE
fileout "${jsonID}" "INFO" "certificate-based authentication => skipping all HTTP checks"
@ -2494,7 +2495,7 @@ run_http_date() {
local spaces=" "
jsonID="HTTP_clock_skew"
if [[ $SERVICE != HTTP ]] || "$CLIENT_AUTH"; then
if [[ $SERVICE != HTTP ]] || [[ "$CLIENT_AUTH" == require ]]; then
return 0
fi
if [[ ! -s $HEADERFILE ]]; then
@ -6443,7 +6444,7 @@ sub_session_resumption() {
return 1
fi
fi
"$CLIENT_AUTH" && return 6
[[ "$CLIENT_AUTH" == require ]] && return 6
if ! "$HAS_TLS13" && "$HAS_NO_SSL2"; then
addcmd+=" -no_ssl2"
else
@ -8365,7 +8366,7 @@ certificate_transparency() {
fi
fi
if [[ $SERVICE != HTTP ]] && ! "$CLIENT_AUTH"; then
if [[ $SERVICE != HTTP ]] && [[ "$CLIENT_AUTH" != require ]]; then
# At the moment Certificate Transparency only applies to HTTPS.
tm_out "N/A"
else
@ -15798,7 +15799,7 @@ run_ticketbleed() {
[[ $VULN_COUNT -le $VULN_THRESHLD ]] && outln && pr_headlineln " Testing for Ticketbleed vulnerability " && outln
pr_bold " Ticketbleed"; out " ($cve), experiment. "
if [[ "$SERVICE" != HTTP ]] && ! "$CLIENT_AUTH"; then
if [[ "$SERVICE" != HTTP ]] && [[ "$CLIENT_AUTH" != require ]]; then
outln "-- (applicable only for HTTPS)"
fileout "$jsonID" "INFO" "not applicable, not HTTP" "$cve" "$cwe"
return 0
@ -16128,7 +16129,7 @@ run_renego() {
[[ $DEBUG -ge 1 ]] && out ", no renegotiation support in TLS 1.3 only servers"
outln
fileout "$jsonID" "OK" "not vulnerable, TLS 1.3 only" "$cve" "$cwe"
elif "$CLIENT_AUTH"; then
elif [[ "$CLIENT_AUTH" == require ]]; then
prln_warning "client x509-based authentication prevents this from being tested"
fileout "$jsonID" "WARN" "client x509-based authentication prevents this from being tested"
sec_client_renego=1
@ -16251,14 +16252,14 @@ run_crime() {
ret=1
elif grep -a Compression $TMPFILE | grep -aq NONE >/dev/null; then
pr_svrty_good "not vulnerable (OK)"
if [[ $SERVICE != HTTP ]] && ! "$CLIENT_AUTH"; then
if [[ $SERVICE != HTTP ]] && [[ "$CLIENT_AUTH" != require ]]; then
out " (not using HTTP anyway)"
fileout "CRIME_TLS" "OK" "not vulnerable (not using HTTP anyway)" "$cve" "$cwe"
else
fileout "CRIME_TLS" "OK" "not vulnerable" "$cve" "$cwe"
fi
else
if [[ $SERVICE == HTTP ]] || "$CLIENT_AUTH"; then
if [[ $SERVICE == HTTP ]] || [[ "$CLIENT_AUTH" == require ]]; then
pr_svrty_high "VULNERABLE (NOT ok)"
fileout "CRIME_TLS" "HIGH" "VULNERABLE" "$cve" "$cwe" "$hint"
else
@ -16364,11 +16365,11 @@ run_breach() {
local detected_compression=""
local get_command=""
[[ $SERVICE != HTTP ]] && ! "$CLIENT_AUTH" && return 7
[[ $SERVICE != HTTP ]] && [[ "$CLIENT_AUTH" != require ]] && return 7
[[ $VULN_COUNT -le $VULN_THRESHLD ]] && outln && pr_headlineln " Testing for BREACH (HTTP compression) vulnerability " && outln
pr_bold " BREACH"; out " ($cve) "
if "$CLIENT_AUTH"; then
if [[ "$CLIENT_AUTH" == require ]]; then
outln "cannot be tested (server side requires x509 authentication)"
fileout "$jsonID" "INFO" "was not tested, server side requires x509 authentication" "$cve" "$cwe"
fi
@ -20356,20 +20357,119 @@ check_proxy() {
fi
}
print_dn() {
local dn="$1"
local cert name
local -i len
# Use $OPENSSL to print the DN by creating a certificate containing the DN
# as the issuer and then having $OPENSSL print the issuer field in the
# resulting certificate.
cert="A003020102020100300A06082A8648CE3D040302${dn}301E170D3139303830353038333030305A170D3139303830353038333030305A30003019301306072A8648CE3D020106082A8648CE3D030107030200FF"
len=$((${#cert}/2))
if [[ $len -lt 128 ]]; then
cert="30$(printf "%02x" $len)$cert"
elif [[ $len -lt 256 ]]; then
cert="3081$(printf "%02x" $len)$cert"
else
cert="3082$(printf "%04x" $len)$cert"
fi
cert+="300A06082A8648CE3D040302030200FF"
len=$((${#cert}/2))
if [[ $len -lt 128 ]]; then
cert="30$(printf "%02x" $len)$cert"
elif [[ $len -lt 256 ]]; then
cert="3081$(printf "%02x" $len)$cert"
else
cert="3082$(printf "%04x" $len)$cert"
fi
name="$(asciihex_to_binary "$cert" | $OPENSSL x509 -issuer -noout -inform DER -nameopt RFC2253 2>/dev/null)"
name="${name#issuer=}"
tm_out "$(strip_leading_space "$name")"
return 0
}
extract_calist() {
local response="$1"
local is_tls13=false
local certreq calist certtypes sigalgs dn
local calist_string=""
local -i len type
[[ "$response" =~ CertificateRequest ]] || return 0
[[ "$response" =~ TLS\ 1.3[\,]?\ Handshake\ \[length\ [0-9a-fA-F]*\]\,\ CertificateRequest ]] && is_tls13=true
certreq="${response##*CertificateRequest}"
certreq="0d${certreq#*0d}"
certreq="${certreq%%<<<*}"
certreq="$(strip_spaces "$(newline_to_spaces "$certreq")")"
certreq="${certreq:8}"
if "$is_tls13"; then
# struct {
# opaque certificate_request_context<0..2^8-1>;
# Extension extensions<2..2^16-1>;
# } CertificateRequest;
len=2*$(hex2dec "${certreq:0:2}")
certreq="${certreq:$((len+2))}"
len=2*$(hex2dec "${certreq:0:4}")
certreq="${certreq:4}"
while true; do
[[ -z "$certreq" ]] && break
type=$(hex2dec "${certreq:0:4}")
len=2*$(hex2dec "${certreq:4:4}")
if [[ $type -eq 47 ]]; then
# This is the certificate_authorities extension
calist="${certreq:8:len}"
len=2*$(hex2dec "${calist:0:4}")
calist="${calist:4}"
break
fi
certreq="${certreq:$((len+8))}"
done
else
# struct {
# ClientCertificateType certificate_types<1..2^8-1>;
# SignatureAndHashAlgorithm
# supported_signature_algorithms<2^16-1>;
# DistinguishedName certificate_authorities<0..2^16-1>;
# } CertificateRequest;
len=2*$(hex2dec "${certreq:0:2}")
certtypes="${certreq:2:len}"
certreq="${certreq:$((len+2))}"
len=2*$(hex2dec "${certreq:0:4}")
sigalgs="${certreq:4:len}"
certreq="${certreq:$((len+4))}"
len=2*$(hex2dec "${certreq:0:4}")
calist="${certreq:4}"
fi
while true; do
[[ -z "$calist" ]] && break
len=2*$(hex2dec "${calist:0:4}")
dn="${calist:4:len}"
calist_string+="$(print_dn "$dn")\n"
calist="${calist:$((len+4))}"
done
[[ -z "$calist_string" ]] && calist_string="empty"
tm_out "$calist_string"
return 0
}
# this is only being called from determine_optimal_proto in order to check whether we have a server
# with client authentication, a server with no SSL session ID switched off
#
sclient_auth() {
[[ $1 -eq 0 ]] && return 0 # no client auth (CLIENT_AUTH=false is preset globally)
if grep -q '^<<< .*CertificateRequest' "$2"; then # CertificateRequest message in -msg
CLIENT_AUTH="require"
[[ $1 -eq 0 ]] && CLIENT_AUTH="optional"
CLIENT_AUTH_CA_LIST="$(extract_calist "$(< "$2")")"
return 0
fi
[[ $1 -eq 0 ]] && return 0
if [[ -n $(awk '/Master-Key: / { print $2 }' "$2") ]]; then # connect succeeded
if grep -q '^<<< .*CertificateRequest' "$2"; then # CertificateRequest message in -msg
CLIENT_AUTH=true
return 0
fi
if [[ -z $(awk '/Session-ID: / { print $2 }' "$2") ]]; then # probably no SSL session
if [[ 2 -eq $(grep -c CERTIFICATE "$2") ]]; then # do another sanity check to be sure
CLIENT_AUTH=false
CLIENT_AUTH="none"
NO_SSL_SESSIONID=true # NO_SSL_SESSIONID is preset globally to false for all other cases
return 0
fi