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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-06 01:46:30 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-06 01:46:30 +0000
commitb5896ba9f6047e7031e2bdee0622d543e11a6734 (patch)
treefd7b460593a2fee1be579bec5697e6d887ea3421 /man/man1/posttls-finger.1
parentInitial commit. (diff)
downloadpostfix-upstream.tar.xz
postfix-upstream.zip
Adding upstream version 3.4.23.upstream/3.4.23upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+.TH POSTTLS-FINGER 1
+.ad
+.fi
+.SH NAME
+posttls-finger
+\-
+Probe the TLS properties of an ESMTP or LMTP server.
+.SH "SYNOPSIS"
+.na
+.nf
+\fBposttls\-finger\fR [\fIoptions\fR] [\fBinet:\fR]\fIdomain\fR[:\fIport\fR] [\fImatch ...\fR]
+.br
+\fBposttls\-finger\fR \-S [\fIoptions\fR] \fBunix:\fIpathname\fR [\fImatch ...\fR]
+.SH DESCRIPTION
+.ad
+.fi
+\fBposttls\-finger\fR(1) connects to the specified destination
+and reports TLS\-related information about the server. With SMTP, the
+destination is a domainname; with LMTP it is either a domainname
+prefixed with \fBinet:\fR or a pathname prefixed with \fBunix:\fR. If
+Postfix is built without TLS support, the resulting posttls\-finger
+program has very limited functionality, and only the \fB\-a\fR, \fB\-c\fR,
+\fB\-h\fR, \fB\-o\fR, \fB\-S\fR, \fB\-t\fR, \fB\-T\fR and \fB\-v\fR options
+are available.
+
+Note: this is an unsupported test program. No attempt is made
+to maintain compatibility between successive versions.
+
+For SMTP servers that don't support ESMTP, only the greeting banner
+and the negative EHLO response are reported. Otherwise, the reported
+EHLO response details further server capabilities.
+
+If TLS support is enabled when \fBposttls\-finger\fR(1) is compiled, and
+the server supports \fBSTARTTLS\fR, a TLS handshake is attempted.
+
+If DNSSEC support is available, the connection TLS security level
+(\fB\-l\fR option) defaults to \fBdane\fR; see TLS_README for
+details. Otherwise, it defaults to \fBsecure\fR. This setting
+determines the certificate matching policy.
+
+If TLS negotiation succeeds, the TLS protocol and cipher details are
+reported. The server certificate is then verified in accordance with
+the policy at the chosen (or default) security level. With public
+CA\-based trust, when the \fB\-L\fR option includes \fBcertmatch\fR,
+(true by default) name matching is performed even if the certificate
+chain is not trusted. This logs the names found in the remote SMTP
+server certificate and which if any would match, were the certificate
+chain trusted.
+
+Note: \fBposttls\-finger\fR(1) does not perform any table lookups, so
+the TLS policy table and obsolete per\-site tables are not consulted.
+It does not communicate with the \fBtlsmgr\fR(8) daemon (or any other
+Postfix daemons); its TLS session cache is held in private memory, and
+disappears when the process exits.
+
+With the \fB\-r \fIdelay\fR option, if the server assigns a TLS
+session id, the TLS session is cached. The connection is then closed
+and re\-opened after the specified delay, and \fBposttls\-finger\fR(1)
+then reports whether the cached TLS session was re\-used.
+
+When the destination is a load balancer, it may be distributing
+load between multiple server caches. Typically, each server returns
+its unique name in its EHLO response. If, upon reconnecting with
+\fB\-r\fR, a new server name is detected, another session is cached
+for the new server, and the reconnect is repeated up to a maximum
+number of times (default 5) that can be specified via the \fB\-m\fR
+option.
+
+The choice of SMTP or LMTP (\fB\-S\fR option) determines the syntax of
+the destination argument. With SMTP, one can specify a service on a
+non\-default port as \fIhost\fR:\fIservice\fR, and disable MX (mail
+exchanger) DNS lookups with [\fIhost\fR] or [\fIhost\fR]:\fIport\fR.
+The [] form is required when you specify an IP address instead of a
+hostname. An IPv6 address takes the form [\fBipv6:\fIaddress\fR].
+The default port for SMTP is taken from the \fBsmtp/tcp\fR entry in
+/etc/services, defaulting to 25 if the entry is not found.
+
+With LMTP, specify \fBunix:\fIpathname\fR to connect to a local server
+listening on a unix\-domain socket bound to the specified pathname;
+otherwise, specify an optional \fBinet:\fR prefix followed by a
+\fIdomain\fR and an optional port, with the same syntax as for
+SMTP. The default TCP port for LMTP is 24.
+
+Arguments:
+.IP "\fB\-a\fR \fIfamily\fR (default: \fBany\fR)"
+Address family preference: \fBipv4\fR, \fBipv6\fR or \fBany\fR. When
+using \fBany\fR, posttls\-finger will randomly select one of the two as
+the more preferred, and exhaust all MX preferences for the first
+address family before trying any addresses for the other.
+.IP "\fB\-A\fR \fItrust\-anchor.pem\fR (default: none)"
+A list of PEM trust\-anchor files that overrides CAfile and CApath
+trust chain verification. Specify the option multiple times to
+specify multiple files. See the main.cf documentation for
+smtp_tls_trust_anchor_file for details.
+.IP "\fB\-c\fR"
+Disable SMTP chat logging; only TLS\-related information is logged.
+.IP "\fB\-C\fR"
+Print the remote SMTP server certificate trust chain in PEM format.
+The issuer DN, subject DN, certificate and public key fingerprints
+(see \fB\-d \fImdalg\fR option below) are printed above each PEM
+certificate block. If you specify \fB\-F \fICAfile\fR or
+\fB\-P \fICApath\fR, the OpenSSL library may augment the chain with
+missing issuer certificates. To see the actual chain sent by the
+remote SMTP server leave \fICAfile\fR and \fICApath\fR unset.
+.IP "\fB\-d \fImdalg\fR (default: \fBsha1\fR)"
+The message digest algorithm to use for reporting remote SMTP server
+fingerprints and matching against user provided certificate
+fingerprints (with DANE TLSA records the algorithm is specified
+in the DNS).
+.IP "\fB\-f\fR"
+Lookup the associated DANE TLSA RRset even when a hostname is not an
+alias and its address records lie in an unsigned zone. See
+smtp_tls_force_insecure_host_tlsa_lookup for details.
+.IP "\fB\-F \fICAfile.pem\fR (default: none)"
+The PEM formatted CAfile for remote SMTP server certificate
+verification. By default no CAfile is used and no public CAs
+are trusted.
+.IP "\fB\-g \fIgrade\fR (default: medium)"
+The minimum TLS cipher grade used by posttls\-finger. See
+smtp_tls_mandatory_ciphers for details.
+.IP "\fB\-h \fIhost_lookup\fR (default: \fBdns\fR)"
+The hostname lookup methods used for the connection. See the
+documentation of smtp_host_lookup for syntax and semantics.
+.IP "\fB\-H \fIchainfiles\fR (default: \fInone\fR)\fR"
+List of files with a sequence PEM\-encoded TLS client certificate
+chains. The list can be built\-up incrementally, by specifying
+the option multiple times, or all at once via a comma or
+whitespace separated list of filenames. Each chain starts with
+a private key, which is followed immediately by the
+corresponding certificate, and optionally by additional issuer
+certificates. Each new key begins a new chain for the
+corresponding algorithm. This option is mutually exclusive with
+the below \fB\-k\fR and \fB\-K\fR options.
+.IP "\fB\-k \fIcertfile\fR (default: \fIkeyfile\fR)\fR"
+File with PEM\-encoded TLS client certificate chain. This
+defaults to \fIkeyfile\fR if one is specified.
+.IP "\fB\-K \fIkeyfile\fR (default: \fIcertfile\fR)"
+File with PEM\-encoded TLS client private key.
+This defaults to \fIcertfile\fR if one is specified.
+.IP "\fB\-l \fIlevel\fR (default: \fBdane\fR or \fBsecure\fR)"
+The security level for the connection, default \fBdane\fR or
+\fBsecure\fR depending on whether DNSSEC is available. For syntax
+and semantics, see the documentation of smtp_tls_security_level.
+When \fBdane\fR or \fBdane\-only\fR is supported and selected, if no
+TLSA records are found, or all the records found are unusable, the
+\fIsecure\fR level will be used instead. The \fBfingerprint\fR
+security level allows you to test certificate or public\-key
+fingerprint matches before you deploy them in the policy table.
+.IP
+Note, since \fBposttls\-finger\fR does not actually deliver any email,
+the \fBnone\fR, \fBmay\fR and \fBencrypt\fR security levels are not
+very useful. Since \fBmay\fR and \fBencrypt\fR don't require peer
+certificates, they will often negotiate anonymous TLS ciphersuites,
+so you won't learn much about the remote SMTP server's certificates
+at these levels if it also supports anonymous TLS (though you may
+learn that the server supports anonymous TLS).
+.IP "\fB\-L \fIlogopts\fR (default: \fBroutine,certmatch\fR)"
+Fine\-grained TLS logging options. To tune the TLS features logged
+during the TLS handshake, specify one or more of:
+.RS
+.IP "\fB0, none\fR"
+These yield no TLS logging; you'll generally want more, but this
+is handy if you just want the trust chain:
+.RS
+.ad
+.nf
+$ posttls\-finger \-cC \-L none destination
+.fi
+.RE
+.IP "\fB1, routine, summary\fR"
+These synonymous values yield a normal one\-line summary of the TLS
+connection.
+.IP "\fB2, debug\fR"
+These synonymous values combine routine, ssl\-debug, cache and verbose.
+.IP "\fB3, ssl\-expert\fR"
+These synonymous values combine debug with ssl\-handshake\-packet\-dump.
+For experts only.
+.IP "\fB4, ssl\-developer\fR"
+These synonymous values combine ssl\-expert with ssl\-session\-packet\-dump.
+For experts only, and in most cases, use wireshark instead.
+.IP "\fBssl\-debug\fR"
+Turn on OpenSSL logging of the progress of the SSL handshake.
+.IP "\fBssl\-handshake\-packet\-dump\fR"
+Log hexadecimal packet dumps of the SSL handshake; for experts only.
+.IP "\fBssl\-session\-packet\-dump\fR"
+Log hexadecimal packet dumps of the entire SSL session; only useful
+to those who can debug SSL protocol problems from hex dumps.
+.IP "\fBuntrusted\fR"
+Logs trust chain verification problems. This is turned on
+automatically at security levels that use peer names signed
+by Certification Authorities to validate certificates. So while
+this setting is recognized, you should never need to set it
+explicitly.
+.IP "\fBpeercert\fR"
+This logs a one line summary of the remote SMTP server certificate
+subject, issuer, and fingerprints.
+.IP "\fBcertmatch\fR"
+This logs remote SMTP server certificate matching, showing the CN
+and each subjectAltName and which name matched. With DANE, logs
+matching of TLSA record trust\-anchor and end\-entity certificates.
+.IP "\fBcache\fR"
+This logs session cache operations, showing whether session caching
+is effective with the remote SMTP server. Automatically used when
+reconnecting with the \fB\-r\fR option; rarely needs to be set
+explicitly.
+.IP "\fBverbose\fR"
+Enables verbose logging in the Postfix TLS driver; includes all of
+peercert..cache and more.
+.RE
+.IP
+The default is \fBroutine,certmatch\fR. After a reconnect,
+\fBpeercert\fR, \fBcertmatch\fR and \fBverbose\fR are automatically
+disabled while \fBcache\fR and \fBsummary\fR are enabled.
+.IP "\fB\-m \fIcount\fR (default: \fB5\fR)"
+When the \fB\-r \fIdelay\fR option is specified, the \fB\-m\fR option
+determines the maximum number of reconnect attempts to use with
+a server behind a load balancer, to see whether connection caching
+is likely to be effective for this destination. Some MTAs
+don't expose the underlying server identity in their EHLO
+response; with these servers there will never be more than
+1 reconnection attempt.
+.IP "\fB\-M \fIinsecure_mx_policy\fR (default: \fBdane\fR)"
+The TLS policy for MX hosts with "secure" TLSA records when the
+nexthop destination security level is \fBdane\fR, but the MX
+record was found via an "insecure" MX lookup. See the main.cf
+documentation for smtp_tls_insecure_mx_policy for details.
+.IP "\fB\-o \fIname=value\fR"
+Specify zero or more times to override the value of the main.cf
+parameter \fIname\fR with \fIvalue\fR. Possible use\-cases include
+overriding the values of TLS library parameters, or "myhostname" to
+configure the SMTP EHLO name sent to the remote server.
+.IP "\fB\-p \fIprotocols\fR (default: !SSLv2)"
+List of TLS protocols that posttls\-finger will exclude or include. See
+smtp_tls_mandatory_protocols for details.
+.IP "\fB\-P \fICApath/\fR (default: none)"
+The OpenSSL CApath/ directory (indexed via c_rehash(1)) for remote
+SMTP server certificate verification. By default no CApath is used
+and no public CAs are trusted.
+.IP "\fB\-r \fIdelay\fR"
+With a cacheable TLS session, disconnect and reconnect after \fIdelay\fR
+seconds. Report whether the session is re\-used. Retry if a new server
+is encountered, up to 5 times or as specified with the \fB\-m\fR option.
+By default reconnection is disabled, specify a positive delay to
+enable this behavior.
+.IP "\fB\-s \fIservername\fR"
+The server name to send with the TLS Server Name Indication (SNI)
+extension. When the server has DANE TLSA records, this parameter
+is ignored and the TLSA base domain is used instead. Otherwise, SNI is
+not used by default, but can be enabled by specifying the desired value
+with this option.
+.IP "\fB\-S\fR"
+Disable SMTP; that is, connect to an LMTP server. The default port for
+LMTP over TCP is 24. Alternative ports can specified by appending
+"\fI:servicename\fR" or ":\fIportnumber\fR" to the destination
+argument.
+.IP "\fB\-t \fItimeout\fR (default: \fB30\fR)"
+The TCP connection timeout to use. This is also the timeout for
+reading the remote server's 220 banner.
+.IP "\fB\-T \fItimeout\fR (default: \fB30\fR)"
+The SMTP/LMTP command timeout for EHLO/LHLO, STARTTLS and QUIT.
+.IP "\fB\-v\fR"
+Enable verbose Postfix logging. Specify more than once to increase
+the level of verbose logging.
+.IP "\fB\-w\fR"
+Enable outgoing TLS wrapper mode, or SMTPS support. This is typically
+provided on port 465 by servers that are compatible with the ad\-hoc
+SMTP in SSL protocol, rather than the standard STARTTLS protocol.
+The destination \fIdomain\fR:\fIport\fR should of course provide such
+a service.
+.IP "\fB\-X\fR"
+Enable \fBtlsproxy\fR(8) mode. This is an unsupported mode,
+for program development only.
+.IP "[\fBinet:\fR]\fIdomain\fR[:\fIport\fR]"
+Connect via TCP to domain \fIdomain\fR, port \fIport\fR. The default
+port is \fBsmtp\fR (or 24 with LMTP). With SMTP an MX lookup is
+performed to resolve the domain to a host, unless the domain is
+enclosed in \fB[]\fR. If you want to connect to a specific MX host,
+for instance \fImx1.example.com\fR, specify [\fImx1.example.com\fR]
+as the destination and \fIexample.com\fR as a \fBmatch\fR argument.
+When using DNS, the destination domain is assumed fully qualified
+and no default domain or search suffixes are applied; you must use
+fully\-qualified names or also enable \fBnative\fR host lookups
+(these don't support \fBdane\fR or \fBdane\-only\fR as no DNSSEC
+validation information is available via \fBnative\fR lookups).
+.IP "\fBunix:\fIpathname\fR"
+Connect to the UNIX\-domain socket at \fIpathname\fR. LMTP only.
+.IP "\fBmatch ...\fR"
+With no match arguments specified, certificate peername matching uses
+the compiled\-in default strategies for each security level. If you
+specify one or more arguments, these will be used as the list of
+certificate or public\-key digests to match for the \fBfingerprint\fR
+level, or as the list of DNS names to match in the certificate at the
+\fBverify\fR and \fBsecure\fR levels. If the security level is
+\fBdane\fR, or \fBdane\-only\fR the match names are ignored, and
+\fBhostname, nexthop\fR strategies are used.
+.ad
+.fi
+.SH "ENVIRONMENT"
+.na
+.nf
+.ad
+.fi
+.IP \fBMAIL_CONFIG\fR
+Read configuration parameters from a non\-default location.
+.IP \fBMAIL_VERBOSE\fR
+Same as \fB\-v\fR option.
+.SH "SEE ALSO"
+.na
+.nf
+smtp\-source(1), SMTP/LMTP message source
+smtp\-sink(1), SMTP/LMTP message dump
+
+.SH "README FILES"
+.na
+.nf
+.ad
+.fi
+Use "\fBpostconf readme_directory\fR" or "\fBpostconf
+html_directory\fR" to locate this information.
+.na
+.nf
+TLS_README, Postfix STARTTLS howto
+.SH "LICENSE"
+.na
+.nf
+.ad
+.fi
+The Secure Mailer license must be distributed with this software.
+.SH "AUTHOR(S)"
+.na
+.nf
+Wietse Venema
+IBM T.J. Watson Research
+P.O. Box 704
+Yorktown Heights, NY 10598, USA
+
+Wietse Venema
+Google, Inc.
+111 8th Avenue
+New York, NY 10011, USA
+
+Viktor Dukhovni