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Merge pull request #2579 from drwetter/merge_2568

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Merge 2568
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Dirk Wetter 2024-10-14 15:55:40 +02:00 committed by GitHub
commit fee04f2db8
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1 changed files with 14 additions and 9 deletions
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testssl.sh
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@ -22933,15 +22933,18 @@ run_rating() {
pr_headlineln " Rating (experimental) "
outln
[[ -n "$STARTTLS_PROTOCOL" ]] && set_grade_cap "T" "STARTTLS encryption is not mandatory for clients. STARTTLS can only be secured client-side"
[[ -n "$STARTTLS_PROTOCOL" ]] && set_grade_cap "T" "STARTTLS is prone to MITM downgrade attacks. A secure TLS upgrade can only be ensured client-side. You should use TLS only (=implicit TLS) rather than STARTTLS as per RFC 8314, for other than SMTP and SIEVE"
# TL;DR: E-mail transfer via port 25 is broken and the amendments suggested so far are duct tape. So please do not expect testssl.sh to shut up.
# TL;DR: STARTTLS connections are inherently insecure. A MITM can always intercept the connection, unless the client checks e.g. the
# certificate accordingly. A secure STARTTLS client is the key but we can't test for it. For other than SMTP and SIEVE (there's no implicit TLS port)
# you should use implicit TLS as per RFC 8314. Especially e-mail transfer via port 25 is broken and amendments so far are duct tape.
# Explanation: For other than SMTP you should use TLS as per RFC 8314 . For SMTP however there's this thing named reality: A mail server cannot
# just switch to the mail submission port 587 only and continue to receive mail from everyone. Even if you advertise this via SRV record (RFC 6186).
# For STARTTLS there's no way to tell for testssl.sh whether it is secure. A MitM can always intercept the connection, unless the client checks
# the certificate accordingly (it's getting better but some just don't). TLSA Records/DANE and MTA-STS (RFC-8461) on the server side can help too.
# But as said, it's useless unless the client MTA checks all that which no tool can check.
# Explanation: There are active MitM attacks possible when using STARTTLS like https://github.com/tintinweb/striptls or
# https://github.com/libcrack/starttlsstrip. It depends on the client only whether it can detect such downgrade attack.
# As some SMTP servers are still misconfigured with wrong certificates it's is still common practice for SMTP client MTAs to
# accept those wrong certificates -- delivering e-mails is more important. There is an e-mail submission port 587 but a mail server
# cannot just switch to it and continue to receive mail from everyone. Even if you advertise this via SRV record (RFC 6186).
# TLSA Records/DANE and MTA-STS (RFC-8461) on the server side can help too,
pr_bold " Rating specs"; out " (not complete) "; outln "SSL Labs's 'SSL Server Rating Guide' (version 2009q from 2020-01-30)"
pr_bold " Specification documentation "; pr_url "https://github.com/ssllabs/research/wiki/SSL-Server-Rating-Guide"
@ -23127,9 +23130,11 @@ run_rating() {
# Pretty print - again, it's just nicer to read
for reason in "${sorted_reasons[@]}"; do
if [[ $reason_nr -eq 0 ]]; then
pr_bold " Grade cap reasons "; outln "$reason"
pr_bold " Grade cap reasons "
outln "$(out_row_aligned_max_width "$reason" " " $TERM_WIDTH)"
else
outln " $reason"
outln "$(out_row_aligned_max_width " $reason" " " $TERM_WIDTH)"
fi
((reason_nr++))
fileout "grade_cap_reason_${reason_nr}" "INFO" "$reason"