.cindex "tainted data" "de-tainting"
The value will be untainted.
+.new
+&*Note*&: If the data result of the lookup (as opposed to the key)
+is empty, then this empty value is stored in &$domain_data$&.
+The option to return the key for the lookup, as the value,
+may be what is wanted.
+.wen
+
.next
Any of the single-key lookup type names may be preceded by
When, as a result of aliasing or forwarding, a message is directed to a pipe,
this variable holds the pipe command when the transport is running.
-.vitem "&$auth1$& &-- &$auth3$&"
+.vitem "&$auth1$& &-- &$auth4$&"
.vindex "&$auth1$&, &$auth2$&, etc"
These variables are used in SMTP authenticators (see chapters
&<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
.cindex "security" "MX lookup"
.cindex "DNS" "DNSSEC"
DNS lookups for domains matching &%dnssec_request_domains%& will be done with
-the dnssec request bit set.
+the DNSSEC request bit set.
This applies to all of the SRV, MX, AAAA, A lookup sequence.
.option dnssec_require_domains routers "domain list&!!" unset
.cindex "security" "MX lookup"
.cindex "DNS" "DNSSEC"
DNS lookups for domains matching &%dnssec_require_domains%& will be done with
-the dnssec request bit set. Any returns not having the Authenticated Data bit
+the DNSSEC request bit set. Any returns not having the Authenticated Data bit
(AD bit) set will be ignored and logged as a host-lookup failure.
This applies to all of the SRV, MX, AAAA, A lookup sequence.
.cindex "security" "MX lookup"
.cindex "DNS" "DNSSEC"
DNS lookups for domains matching &%dnssec_request_domains%& will be done with
-the dnssec request bit set. Setting this transport option is only useful if the
+the DNSSEC request bit set. Setting this transport option is only useful if the
transport overrides or sets the host names. See the &%dnssec_request_domains%&
router option.
.cindex "security" "MX lookup"
.cindex "DNS" "DNSSEC"
DNS lookups for domains matching &%dnssec_require_domains%& will be done with
-the dnssec request bit set. Setting this transport option is only
+the DNSSEC request bit set. Setting this transport option is only
useful if the transport overrides or sets the host names. See the
&%dnssec_require_domains%& router option.
.cindex DANE "requiring for certain servers"
If built with DANE support, Exim will require that a DNSSEC-validated
TLSA record is present for any host matching the list,
-and that a DANE-verified TLS connection is made. See
-the &%dnssec_request_domains%& router and transport options.
+and that a DANE-verified TLS connection is made.
There will be no fallback to in-clear communication.
+See the &%dnssec_request_domains%& router and transport options.
See section &<<SECDANE>>&.
.option hosts_require_ocsp smtp "host list&!!" unset
.option hosts_try_dane smtp "host list&!!" *
.cindex DANE "transport options"
.cindex DANE "attempting for certain servers"
-If built with DANE support, Exim will require that a DNSSEC-validated
-TLSA record is present for any host matching the list,
-and that a DANE-verified TLS connection is made. See
-the &%dnssec_request_domains%& router and transport options.
-There will be no fallback to in-clear communication.
+.new
+If built with DANE support, Exim will look up a
+TLSA record for any host matching the list,
+If one is found and that lookup was DNSSEC-validated,
+then Exim requires that a DANE-verified TLS connection is made for that host;
+there will be no fallback to in-clear communication.
+.wen
+See the &%dnssec_request_domains%& router and transport options.
See section &<<SECDANE>>&.
.option hosts_try_fastopen smtp "host list&!!" *
option is passed. When authentication succeeds, the identity of the user
who authenticated is placed in &$auth1$&.
-The Dovecot configuration to match the above wil look
+The Dovecot configuration to match the above will look
something like:
.code
conf.d/10-master.conf :-
The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
when this happens.
+.new
+To see the list of mechanisms supported by the library run Exim with "auth" debug
+enabled and look for a line containing "GNU SASL supports".
+Note however that some may not have been tested from Exim.
+.wen
+
.option client_authz gsasl string&!! unset
This option can be used to supply an &'authorization id'&
This option is exapanded before use, and should result in
the account name to be used.
+
.option client_spassword gsasl string&!! unset
+.new
+This option is only supported for library versions 1.9.1 and greater.
+The macro _HAVE_AUTH_GSASL_SCRAM_S_KEY will be defined when this is so.
+.wen
+
If a SCRAM mechanism is being used and this option is set
+and correctly sized
it is used in preference to &%client_password%&.
The value after expansion should be
a 40 (for SHA-1) or 64 (for SHA-256) character string
with the PBKDF2-prepared password, hex-encoded.
+
Note that this value will depend on the salt and iteration-count
supplied by the server.
-
+The option is expanded before use.
+.new
+During the expansion &$auth1$& is set with the client username,
+&$auth2$& with the iteration count, and
+&$auth3$& with the salt.
+
+The intent of this option
+is to support clients that can cache thes salted password
+to save on recalculation costs.
+The cache lookup should return an unusable value
+(eg. an empty string)
+if the salt or iteration count has changed
+
+If the authentication succeeds then the above variables are set,
+.vindex "&$auth4$&"
+plus the calculated salted password value value in &$auth4$&,
+during the expansion of the &%client_set_id%& option.
+A side-effect of this expansion can be used to prime the cache.
+.wen
.option server_channelbinding gsasl boolean false
-Do not set this true and rely on the properties
-without consulting a cryptographic engineer.
-. Unsure what that's about. It might be the "Triple Handshake"
-. vulnerability; cf. https://www.mitls.org/pages/attacks/3SHAKE
-. If so, we're ok, requiring Extended Master Secret if TLS
-. Session Resumption was used.
-
Some authentication mechanisms are able to use external context at both ends
of the session to bind the authentication to that context, and fail the
authentication process if that context differs. Specifically, some TLS
this option causes some clients to start failing. Some future release
of Exim might have switched the default to be true.
-However, Channel Binding in TLS has proven to be vulnerable in current versions.
-Do not plan to rely upon this feature for security, ever, without consulting
-with a subject matter expert (a cryptographic engineer).
+. However, Channel Binding in TLS has proven to be vulnerable in current versions.
+. Do not plan to rely upon this feature for security, ever, without consulting
+. with a subject matter expert (a cryptographic engineer).
+
+.new
+This option was deprecated in previous releases due to doubts over
+the "Triple Handshake" vulnerability.
+Exim takes suitable precausions (requiring Extended Master Secret if TLS
+Session Resumption was used) for safety.
+.wen
.option server_hostname gsasl string&!! "see below"
this authentication method on a secure (eg. under TLS) connection.
One possible use, compatible with the
-K-9 Mail Andoid client (&url(https://k9mail.github.io/)),
+K-9 Mail Android client (&url(https://k9mail.github.io/)),
is for using X509 client certificates.
It thus overlaps in function with the TLS authenticator
DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
-A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using dnssec.
+A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using DNSSEC.
If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
will be required for the host. If it does not, the host will not
be used; there is no fallback to non-DANE or non-TLS.
different values. Some DNS lists may return more than one address record;
see section &<<SECThanmuldnsrec>>& for details of how they are checked.
+.new
+Values returned by a properly running DBSBL should be in the 127.0.0.0/8
+range. If a DNSBL operator loses control of the domain, lookups on it
+may start returning other addresses. Because of this, Exim now ignores
+returned values outside the 127/8 region.
+.wen
+
.section "Variables set from DNS lists" "SECID204"
.cindex "expansion" "variables, set from DNS list"
.endd
which is less clear, and harder to maintain.
+Negation can also be used with a bitwise-and restriction.
+The dnslists condition with only be trus if a result is returned
+by the lookup which, anded with the restriction, is all zeroes.
+For example:
+.code
+deny dnslists = zen.spamhaus.org!&0.255.255.0
+.endd
+
when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
verified
using a CA trust anchor,
-&`CA=dane`& if using a DNS trust anchor,
+&`CV=dane`& if using a DNS trust anchor,
and &`CV=no`& if not.
.next
.cindex "log" "TLS cipher"
git://git.exim.org / users / heiko / exim.git / blobdiff