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Limit size of signature_algorithms extension

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Some servers get confused if the signature_algorithms extension is too large. This commit addresses the problem by:

* For TLS 1.2, generally limiting the signature algoritms to those consistent with the key type being tested.

* For TLS 1.3, breaking the list of signature schemes in two, and testing each half of the list separately.
This commit is contained in:
David Cooper 2022-11-14 13:35:35 -08:00
parent 6088eddab6
commit c7644ad58e
1 changed files with 31 additions and 12 deletions
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41
testssl.sh
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@ -10894,7 +10894,7 @@ run_fs() {
fi
if "$using_sockets"; then
protos_to_try=""
"$fs_tls13_offered" && protos_to_try="04"
"$fs_tls13_offered" && protos_to_try="04-01 04-02"
# For TLS 1.2, find a supported cipher suite corresponding to each of the key types (RSA, ECDSA, DSS).
# Need to try each key type separately, otherwise not all supported signature algorithms will be found.
if "$fs_tls12_offered"; then
@ -10910,29 +10910,48 @@ run_fs() {
dss_cipher="${hexcode[i]}"
fi
done
[[ -n "$rsa_cipher" ]] && protos_to_try+=" 03-$rsa_cipher"
[[ -n "$ecdsa_cipher" ]] && protos_to_try+=" 03-$ecdsa_cipher"
[[ -n "$dss_cipher" ]] && protos_to_try+=" 03-$dss_cipher"
[[ -n "$rsa_cipher" ]] && protos_to_try+=" 03-rsa-$rsa_cipher"
[[ -n "$ecdsa_cipher" ]] && protos_to_try+=" 03-ecdsa-$ecdsa_cipher"
[[ -n "$dss_cipher" ]] && protos_to_try+=" 03-dss-$dss_cipher"
fi
for proto in $protos_to_try; do
while true; do
i=0
sigalgs_to_test=""
# A few servers get confused if the signature_algorithms extension contains too many entries. So:
# * For TLS 1.3, break the list into two and test each half separately.
# * For TLS 1.2, generally limit the signature_algorithms extension to algorithms that are consistent with the key type.
for hexc in "${sigalgs_hex[@]}"; do
if [[ "$proto" == 04 ]]; then
! "${tls13_supported_sigalgs[i]}" && sigalgs_to_test+=", $hexc"
if [[ "$proto" == 04* ]]; then
if ! "${tls13_supported_sigalgs[i]}"; then
if [[ "${proto##*-}" == 01 ]]; then
[[ $i -le 16 ]] && sigalgs_to_test+=", $hexc"
else
! "${tls12_supported_sigalgs[i]}" && sigalgs_to_test+=", $hexc"
[[ $i -gt 16 ]] && sigalgs_to_test+=", $hexc"
fi
fi
elif ! "${tls12_supported_sigalgs[i]}"; then
if [[ "$proto" =~ rsa ]]; then
if [[ "${hexc:3:2}" == 01 ]] || [[ "${hexc:0:2}" == 08 ]]; then
sigalgs_to_test+=", $hexc"
fi
elif [[ "$proto" =~ dss ]]; then
[[ "${hexc:3:2}" == 02 ]] && sigalgs_to_test+=", $hexc"
else
if [[ "${hexc:3:2}" == 03 ]] || [[ "${hexc:0:2}" == 08 ]]; then
sigalgs_to_test+=", $hexc"
fi
fi
fi
i+=1
done
[[ -z "$sigalgs_to_test" ]] && break
len1=$(printf "%02x" "$((2*${#sigalgs_to_test}/7))")
len2=$(printf "%02x" "$((2*${#sigalgs_to_test}/7+2))")
if [[ "$proto" == 04 ]]; then
tls_sockets "$proto" "$TLS13_CIPHER" "all+" "00,0d, 00,$len2, 00,$len1, ${sigalgs_to_test:2}"
if [[ "$proto" == 04* ]]; then
tls_sockets "${proto%%-*}" "$TLS13_CIPHER" "all+" "00,0d, 00,$len2, 00,$len1, ${sigalgs_to_test:2}"
else
tls_sockets "${proto%-*}" "${proto#*-}, 00,ff" "ephemeralkey" "00,0d, 00,$len2, 00,$len1, ${sigalgs_to_test:2}"
tls_sockets "${proto%%-*}" "${proto##*-}, 00,ff" "ephemeralkey" "00,0d, 00,$len2, 00,$len1, ${sigalgs_to_test:2}"
fi
[[ $? -eq 0 ]] || break
sigalg_found="$(awk -F ': ' '/^Peer signing digest/ { print $2 } ' "$TEMPDIR/$NODEIP.parse_tls_serverhello.txt")"
@ -10944,7 +10963,7 @@ run_fs() {
i+=1
done
[[ -z "${sigalgs_hex[i]}" ]] && break
if [[ "$proto" == 04 ]]; then
if [[ "$proto" == 04* ]]; then
"${tls13_supported_sigalgs[i]}" && break
tls13_supported_sigalgs[i]=true
tls13_supported_sigalg_list+=" $sigalg_found"