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Check cert serial len + fix output when too big

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OpenSSL shows certificate serial numbers >35 with a LF (0A). Testssl.sh
just output that which makes JSON invalid and displays the LF in the terminal
too.

This commit fixes that (#2010) by adding filters so that the
serialnumber is not a multiline string.

Also this commit introduces a new function: a size check of the cert serial.
Below 8 bytes the CAB Forum's lower limit is hit which says the *entropy*
from a CSPRNG should be at least 64 bits. It is assumed that below 8 bytes
length this requirement isn't possible to meet (needs to be clarified with
Shannon, 8 bytes seems to low to me).
  The high threshold is according to RFC 5280, Section-4.1.2.2 .

See also #2013.

The output has changed, so that on the terminal the serial has one line,
SHA1 and SHA256 each one line. The new json key is "cert_serialNumberLen".
This commit is contained in:
Dirk Wetter 2021-10-19 19:42:12 +02:00
parent 9683af44a2
commit 2edfa57eaa
1 changed files with 30 additions and 4 deletions
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34
testssl.sh
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@ -8429,8 +8429,10 @@ certificate_transparency() {
return 0
}
# replacement for inline $OPENSSL x509 -noout -in $HOSTCERT -serial
# and $OPENSSL x509 -noout -in $HOSTCERT -fingerprint -sha256/-sha1
# Shortcut for $OPENSSL x509 -noout -in $cert $ossl_command
# arg1 is the certificate
# arg2 is -serial | -fingerprint -sha1 | -fingerprint -sha256
# returns the serial or fingerprint as ASCII
#
determine_cert_fingerprint_serial() {
local cert="$1"
@ -8444,6 +8446,10 @@ determine_cert_fingerprint_serial() {
result="${result//:/}"
result="${result//SHA1 /}"
result="${result//SHA256 /}"
# When the serial number is too large we'll get a 0x0a LF after 70 ASCII chars (see #2010).
# Thus we clean them here so that it is displayed correctly.
result="${result/[$'\n\r']/}"
result="${result//[\\]/}"
safe_echo "$result"
}
@ -8549,6 +8555,7 @@ certificate_info() {
local -i secsaday=86400
local first=true
local badocsp=1
local len_cert_serial=0
if [[ $number_of_certificates -gt 1 ]]; then
[[ $certificate_number -eq 1 ]] && outln
@ -8885,12 +8892,31 @@ certificate_info() {
hostcert="$(<$HOSTCERT)"
out "$indent"; pr_bold " Serial / Fingerprints "
out "$indent"; pr_bold " Serial "
cert_serial="$(determine_cert_fingerprint_serial "$hostcert" "-serial")"
fileout "cert_serialNumber${json_postfix}" "INFO" "$cert_serial"
out "$cert_serial"
len_cert_serial=${#cert_serial}
len_cert_serial=$(( len_cert_serial / 2 ))
if [[ $len_cert_serial -gt 20 ]]; then
# https://datatracker.ietf.org/doc/html/rfc5280#section-4.1.2.2
outln
prln_svrty_low "${spaces}NOT ok: length must not exceed 20 bytes (is: $len_cert_serial bytes)"
fileout "cert_serialNumberLen${json_postfix}" "LOW" "$len_cert_serial is too long"
elif [[ $len_cert_serial -lt 8 ]]; then
# Wording is from https://cabforum.org/wp-content/uploads/CA-Browser-Forum-BR-1.8.0.pdf
prln_svrty_low " NOT ok: length should be >= 64 bits entropy (is: $len_cert_serial bytes)"
fileout "cert_serialNumberLen${json_postfix}" "LOW" "$len_cert_serial is not enough entropy"
else
outln " (OK: length $len_cert_serial)"
fileout "cert_serialNumberLen${json_postfix}" "INFO" "$len_cert_serial"
fi
out "$indent"; pr_bold " Fingerprints "
cert_fingerprint_sha1="$(determine_cert_fingerprint_serial "$hostcert" "-fingerprint -sha1")"
outln "$cert_serial / SHA1 $cert_fingerprint_sha1"
outln "SHA1 $cert_fingerprint_sha1"
fileout "cert_fingerprintSHA1${json_postfix}" "INFO" "${cert_fingerprint_sha1}"
cert_fingerprint_sha2="$(determine_cert_fingerprint_serial "$hostcert" "-fingerprint -sha256")"