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WIP: Don't call s_client for unsupported protocol versions

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This PR fixes a couple of places where "$OPENSSL s_client" is called with "-ssl3" even if SSLv3 is not supported.

The fix in ciphers_by_strength() is easy, as the issue only occurs if "$using_sockets" is true. If SSLv3 (or TLSv1.3) is not supported, then testing using "$OPENSSL s_client" is skipped and all of the supported ciphers are found using tls_sockets().

The fix for run_tls_fallback_scsv() is more complicated. While it is easy to avoid calling "$OPENSSL s_client" with "-ssl3" if SSLv3 is not supported, it is not easy to determine the correct message to present to the user if support for SSLv3 (and possibly also TLSv1.3) is unknown.

For the case in which $high_proto cannot be set, I believe that I have covered all of the possibilities, but an not sure if the correct message/rating is used in every case.

For the case in which it is not possible to determine whether SSLv3 is the $low_proto, more could be done. If $high_proto is TLS 1.1 or TLS 1, then this PR is okay, as it is possible that SSLv3 would be the fallback protocol, but there is no way to tell. However, it seems unlikely that a server would support TLS 1.2 and SSLv3, but not TLS 1.1 or TLS 1. So, perhaps if $high_proto is TLS 1.2 and the server does not support TLS 1.1 or TLS 1, it should just be assumed that SSLv3 is not supported, even if it cannot be tested.
This commit is contained in:
David Cooper 2019-11-14 16:41:19 -05:00
parent fa5bb18d15
commit 00f613f62d
1 changed files with 42 additions and 10 deletions
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52
testssl.sh
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@ -4083,14 +4083,16 @@ ciphers_by_strength() {
fi
else # no SSLv2
nr_ossl_ciphers=0
for (( i=0; i < nr_ciphers; i++ )); do
if "${ossl_supported[i]}"; then
ciphers_found2[nr_ossl_ciphers]=false
ciph2[nr_ossl_ciphers]="${ciph[i]}"
index[nr_ossl_ciphers]=$i
nr_ossl_ciphers+=1
fi
done
if ( "$HAS_SSL3" || [[ $proto != -ssl3 ]] ) && ( "$HAS_TLS13" || [[ $proto != -tls1_3 ]] ); then
for (( i=0; i < nr_ciphers; i++ )); do
if "${ossl_supported[i]}"; then
ciphers_found2[nr_ossl_ciphers]=false
ciph2[nr_ossl_ciphers]="${ciph[i]}"
index[nr_ossl_ciphers]=$i
nr_ossl_ciphers+=1
fi
done
fi
if [[ $nr_ossl_ciphers -eq 0 ]]; then
num_bundles=0
else
@ -14785,6 +14787,7 @@ run_tls_fallback_scsv() {
high_proto="$p"
break
fi
[[ "$p" == ssl3 ]] && ! "$HAS_SSL3" && continue
$OPENSSL s_client $(s_client_options "-$p $STARTTLS $BUGS -connect $NODEIP:$PORT $PROXY $SNI") >$TMPFILE 2>$ERRFILE </dev/null
if sclient_connect_successful $? $TMPFILE; then
high_proto="$p"
@ -14806,13 +14809,42 @@ run_tls_fallback_scsv() {
fileout "$jsonID" "HIGH" "only SSLv3 supported"
return 0
;;
*) prln_svrty_good "No fallback possible, TLS 1.3 is the only protocol (OK)"
fileout "$jsonID" "OK" "only TLS 1.3 supported"
*) if [[ $(has_server_protocol tls1_3) -eq 0 ]]; then
# If the server supports TLS 1.3, and does not support TLS 1.2, TLS 1.1,
# or TLS 1, then assume it does not support SSLv3, even if SSLv3 cannot
# be tested.
prln_svrty_good "No fallback possible, TLS 1.3 is the only protocol (OK)"
fileout "$jsonID" "OK" "only TLS 1.3 supported"
elif [[ $(has_server_protocol tls1_3) -eq 1 ]] && \
( [[ $(has_server_protocol ssl3) -eq 1 ]] || "$HAS_SSL3" ); then
# TLS 1.3, TLS 1.2, TLS 1.1, TLS 1, and SSLv3 are all not supported.
# This may be an SSLv2-only server, if $OPENSSL does not support SSLv2.
prln_warning "test failed (couldn't connect)"
fileout "$jsonID" "WARN" "Check failed. (couldn't connect)"
elif [[ $(has_server_protocol tls1_3) -eq 1 ]]; then
# If the server does not support TLS 1.3, TLS 1.2, TLS 1.1, or TLS 1, and
# support for SSLv3 cannot be tested, then treat it as HIGH severity, since
# it is very likely that SSLv3 is the only supported protocol.
prln_svrty_high "No fallback possible, TLS 1.2, TLS 1.1, and TLS 1 not supported (OK)"
fileout "$jsonID" "HIGH" "TLS 1.2, TLS 1.1, and TLS 1 not supported"
else
# TLS 1.2, TLS 1.1, and TLS 1 are not supported, but can't tell whether TLS 1.3 is supported.
# This could be a TLS 1.3 only server, an SSLv3 only server (if SSLv3 support cannot be tested),
# or a server that does not support SSLv3 or any TLS protocol. So, don't report a severity,
# since this could either be good or bad.
outln "No fallback possible, TLS 1.2, TLS 1.1, and TLS 1 not supported (OK)"
fileout "$jsonID" "INFO" "TLS 1.2, TLS 1.1, and TLS 1 not supported"
fi
return 0
esac
# Next find a second protocol that the server supports.
for p in $protos_to_try; do
if [[ "$p" == ssl3 ]] && ! "$HAS_SSL3"; then
prln_local_problem "Can't test: $OPENSSL does not support SSLv3"
fileout "$jsonID" "WARN" "Can't test: $OPENSSL does not support SSLv3"
return 1
fi
[[ $(has_server_protocol "$p") -eq 1 ]] && continue
if [[ $(has_server_protocol "$p") -eq 0 ]]; then
low_proto="$p"