Fix greylisting for Exim 4.94
This commit is contained in:
David Woodhouse
parent
e1b0164c04
commit
b707c4f2cb
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@ -396,7 +396,20 @@ index 3423ee0..7d1e552 100644
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# For spam scanning, there is a similar option that defines the interface to
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@@ -157,7 +159,7 @@ acl_smtp_data = acl_check_data
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@@ -147,6 +149,12 @@ acl_smtp_data = acl_check_data
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# spamd_address = 127.0.0.1 783
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+# Set the default sqlite database file for greylisting. Uncomment this
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+# if you use the greylisting ACLs defined below.
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+
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+# sqlite_dbfile = /var/spool/exim/db/greylist.db
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+
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+
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# If Exim is compiled with support for TLS, you may want to enable the
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# following options so that Exim allows clients to make encrypted
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# connections. In the authenticators section below, there are template
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@@ -157,7 +165,7 @@ acl_smtp_data = acl_check_data
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# Allow any client to use TLS.
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@ -405,7 +418,7 @@ index 3423ee0..7d1e552 100644
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# Specify the location of the Exim server's TLS certificate and private key.
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# The private key must not be encrypted (password protected). You can put
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@@ -165,8 +167,8 @@ acl_smtp_data = acl_check_data
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@@ -165,8 +173,8 @@ acl_smtp_data = acl_check_data
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# need the first setting, or in separate files, in which case you need both
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# options.
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@ -416,7 +429,7 @@ index 3423ee0..7d1e552 100644
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# For OpenSSL, prefer EC- over RSA-authenticated ciphers
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# tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
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@@ -180,8 +182,8 @@ acl_smtp_data = acl_check_data
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@@ -180,8 +188,8 @@ acl_smtp_data = acl_check_data
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# them you should also allow TLS-on-connect on the traditional but
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# non-standard port 465.
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@ -427,7 +440,7 @@ index 3423ee0..7d1e552 100644
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# Specify the domain you want to be added to all unqualified addresses
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@@ -239,6 +241,24 @@ never_users = root
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@@ -239,6 +247,24 @@ never_users = root
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host_lookup = *
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@ -452,7 +465,7 @@ index 3423ee0..7d1e552 100644
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# The setting below causes Exim to try to initialize the system resolver
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# library with DNSSEC support. It has no effect if your library lacks
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@@ -369,8 +389,8 @@ timeout_frozen_after = 7d
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@@ -369,8 +395,8 @@ timeout_frozen_after = 7d
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# Note that TZ is handled separately by the timezone runtime option
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# and TIMEZONE_DEFAULT buildtime option.
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@ -463,7 +476,7 @@ index 3423ee0..7d1e552 100644
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@@ -381,6 +401,29 @@ timeout_frozen_after = 7d
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@@ -381,6 +407,29 @@ timeout_frozen_after = 7d
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begin acl
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@ -493,7 +506,7 @@ index 3423ee0..7d1e552 100644
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# This access control list is used for every RCPT command in an incoming
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# SMTP message. The tests are run in order until the address is either
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# accepted or denied.
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@@ -392,6 +435,7 @@ acl_check_rcpt:
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@@ -392,6 +441,7 @@ acl_check_rcpt:
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accept hosts = :
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control = dkim_disable_verify
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@ -501,7 +514,7 @@ index 3423ee0..7d1e552 100644
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#############################################################################
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# The following section of the ACL is concerned with local parts that contain
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@@ -445,7 +489,8 @@ acl_check_rcpt:
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@@ -445,7 +495,8 @@ acl_check_rcpt:
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accept local_parts = postmaster
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domains = +local_domains
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@ -511,7 +524,7 @@ index 3423ee0..7d1e552 100644
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require verify = sender
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@@ -471,6 +516,7 @@ acl_check_rcpt:
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@@ -471,6 +522,7 @@ acl_check_rcpt:
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accept hosts = +relay_from_hosts
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control = submission
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control = dkim_disable_verify
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@ -519,7 +532,7 @@ index 3423ee0..7d1e552 100644
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# Accept if the message arrived over an authenticated connection, from
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# any host. Again, these messages are usually from MUAs, so recipient
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@@ -480,6 +526,7 @@ acl_check_rcpt:
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@@ -480,6 +532,7 @@ acl_check_rcpt:
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accept authenticated = *
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control = submission
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control = dkim_disable_verify
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@ -527,7 +540,7 @@ index 3423ee0..7d1e552 100644
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# Insist that a HELO/EHLO was accepted.
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@@ -505,7 +552,8 @@ acl_check_rcpt:
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@@ -505,7 +558,8 @@ acl_check_rcpt:
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# There are no default checks on DNS black lists because the domains that
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# contain these lists are changing all the time. However, here are two
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# examples of how you can get Exim to perform a DNS black list lookup at this
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@ -537,7 +550,7 @@ index 3423ee0..7d1e552 100644
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#
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# deny dnslists = black.list.example
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# message = rejected because $sender_host_address is in a black list at $dnslist_domain\n$dnslist_text
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@@ -513,6 +561,10 @@ acl_check_rcpt:
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@@ -513,6 +567,10 @@ acl_check_rcpt:
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# warn dnslists = black.list.example
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# add_header = X-Warning: $sender_host_address is in a black list at $dnslist_domain
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# log_message = found in $dnslist_domain
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@ -548,7 +561,7 @@ index 3423ee0..7d1e552 100644
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#############################################################################
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#############################################################################
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@@ -539,6 +591,10 @@ acl_check_rcpt:
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@@ -539,6 +597,10 @@ acl_check_rcpt:
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# set acl_m_content_filter = ${lookup PER_RCPT_CONTENT_FILTER}
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#############################################################################
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@ -559,7 +572,7 @@ index 3423ee0..7d1e552 100644
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# At this point, the address has passed all the checks that have been
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# configured, so we accept it unconditionally.
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@@ -588,21 +644,32 @@ acl_check_data:
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@@ -588,21 +650,32 @@ acl_check_data:
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message = header syntax
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log_message = header syntax ($acl_verify_message)
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@ -588,19 +601,20 @@ index 3423ee0..7d1e552 100644
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- # Add headers to a message if it is judged to be spam. Before enabling this,
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- # you must install SpamAssassin. You may also need to set the spamd_address
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- # option above.
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+ # Bypass SpamAssassin checks if the message is too large.
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#
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- #
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- # warn spam = nobody
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- # add_header = X-Spam_score: $spam_score\n\
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- # X-Spam_score_int: $spam_score_int\n\
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- # X-Spam_bar: $spam_bar\n\
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- # X-Spam_report: $spam_report
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+ # Bypass SpamAssassin checks if the message is too large.
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+ #
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+ # accept condition = ${if >={$message_size}{100000} {1}}
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+ # add_header = X-Spam-Note: SpamAssassin run bypassed due to message size
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#############################################################################
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# No more tests if PRDR was actively used.
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@@ -616,11 +683,63 @@ acl_check_data:
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@@ -616,11 +689,63 @@ acl_check_data:
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# condition = ...
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#############################################################################
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@ -665,7 +679,7 @@ index 3423ee0..7d1e552 100644
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######################################################################
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@@ -722,7 +841,7 @@ system_aliases:
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@@ -722,7 +847,7 @@ system_aliases:
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driver = redirect
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allow_fail
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allow_defer
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@ -674,7 +688,7 @@ index 3423ee0..7d1e552 100644
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# user = exim
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file_transport = address_file
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pipe_transport = address_pipe
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@@ -760,7 +879,7 @@ userforward:
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@@ -760,7 +885,7 @@ userforward:
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# local_part_suffix = +* : -*
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# local_part_suffix_optional
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file = $home/.forward
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@ -683,7 +697,7 @@ index 3423ee0..7d1e552 100644
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no_verify
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no_expn
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check_ancestor
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@@ -768,6 +887,12 @@ userforward:
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@@ -768,6 +893,12 @@ userforward:
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pipe_transport = address_pipe
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reply_transport = address_reply
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@ -696,7 +710,7 @@ index 3423ee0..7d1e552 100644
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# This router matches local user mailboxes. If the router fails, the error
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# message is "Unknown user".
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@@ -809,6 +934,25 @@ remote_smtp:
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@@ -809,6 +940,25 @@ remote_smtp:
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driver = smtp
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message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
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@ -722,7 +736,7 @@ index 3423ee0..7d1e552 100644
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# This transport is used for delivering messages to a smarthost, if the
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# smarthost router is enabled. This starts from the same basis as
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@@ -861,8 +1005,8 @@ local_delivery:
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@@ -861,8 +1011,8 @@ local_delivery:
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delivery_date_add
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envelope_to_add
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return_path_add
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@ -733,7 +747,7 @@ index 3423ee0..7d1e552 100644
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# This transport is used for handling pipe deliveries generated by alias or
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@@ -895,6 +1039,16 @@ address_reply:
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@@ -895,6 +1045,16 @@ address_reply:
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driver = autoreply
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@ -750,7 +764,7 @@ index 3423ee0..7d1e552 100644
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######################################################################
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# RETRY CONFIGURATION #
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@@ -935,6 +1089,21 @@ begin rewrite
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@@ -935,6 +1095,21 @@ begin rewrite
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# AUTHENTICATION CONFIGURATION #
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######################################################################
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@ -772,7 +786,7 @@ index 3423ee0..7d1e552 100644
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# The following authenticators support plaintext username/password
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# authentication using the standard PLAIN mechanism and the traditional
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# but non-standard LOGIN mechanism, with Exim acting as the server.
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@@ -950,7 +1119,7 @@ begin rewrite
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@@ -950,7 +1125,7 @@ begin rewrite
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# The default RCPT ACL checks for successful authentication, and will accept
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# messages from authenticated users from anywhere on the Internet.
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@ -781,7 +795,7 @@ index 3423ee0..7d1e552 100644
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# PLAIN authentication has no server prompts. The client sends its
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# credentials in one lump, containing an authorization ID (which we do not
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@@ -964,7 +1133,7 @@ begin authenticators
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@@ -964,7 +1139,7 @@ begin authenticators
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# driver = plaintext
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# server_set_id = $auth2
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# server_prompts = :
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@ -790,7 +804,7 @@ index 3423ee0..7d1e552 100644
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# server_advertise_condition = ${if def:tls_in_cipher }
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# LOGIN authentication has traditional prompts and responses. There is no
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@@ -976,7 +1145,7 @@ begin authenticators
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@@ -976,7 +1151,7 @@ begin authenticators
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# driver = plaintext
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# server_set_id = $auth1
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# server_prompts = <| Username: | Password:
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@ -1,11 +1,44 @@
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# $Id: acl-greylist-sqlite,v 1.3 2007/11/25 19:17:28 dwmw2 Exp $
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#
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# Exim ACL for greylisting. David Woodhouse <dwmw2@infradead.org>
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#
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# For full background on the logic behind greylisting and how this
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# ACL works, see https://github.com/Exim/exim/wiki/SimpleGreylisting
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#
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GREYDB=/var/spool/exim/db/greylist.db
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# UPDATING TO EXIM 4.94+
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# ======================
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#
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# Previous versions of this ACL specified the sqlite database filename
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# in the sqlite lookup strings directly, but since Exim 4.94 is it no
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# longer permitted to mix "tainted" text which comes from the message
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# itself, with the filename. Thus, you now have to set
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#
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# sqlite_dbfile = /var/spool/exim/db/greylist.db
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#
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# ... in the main configuration because it can't be specified within
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# the ACL in this file any more.
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# ACL for greylisting. Place reason(s) for greylisting into a variable named
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# $acl_m_greylistreasons before invoking with 'require acl = greylist_mail'.
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# The reasons should be separate lines of text, and will be reported in
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# the SMTP rejection message as well as the log message.
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# USING THIS ACL
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# ==============
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#
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# First set sqlite_dbfile in the main configuration file to point to
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# the greylist sqlite database, as described above.
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#
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# In your main ACLs, gather reason(s) for greylisting into a variable
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# named $acl_m_greylistreasons before invoking this ACL with
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# 'require acl = greylist_mail'. The reasons should be separate lines
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# of text, and will be reported in the SMTP rejection message as well
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# as the log message. Anything "suspicious" about the email can be
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# used as criteria here — being HTML, having even a few SpamAssassin
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# points, even lacking SPF authorisation (which is OK for greylisting
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# although you should never reject outright for an SPF "failure"
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# because of the flaws in SPF).
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#
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# Obviously you need to .include this file too in order to be able
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# to invoke this greylist_mail ACL.
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# HOW IT WORKS
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# ============
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#
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# When a suspicious mail is seen, we temporarily reject it and wait to see
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# if the sender tries again. Most spam robots won't bother. Real mail hosts
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@ -44,15 +77,13 @@ GREYDB=/var/spool/exim/db/greylist.db
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#
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greylist_mail:
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# First, accept if it there's absolutely nothing suspicious about it...
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accept condition = ${if eq{$acl_m_greylistreasons}{} {1}}
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# ... or if it was generated locally or by authenticated clients.
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# Firstly, accept if it was generated locally or by authenticated clients.
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accept hosts = :
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accept authenticated = *
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# Secondly, there's _absolutely_ no point in greylisting mail from
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# hosts which are known to resend their mail. Just accept it.
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accept condition = ${lookup sqlite {GREYDB SELECT host from resenders \
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accept condition = ${lookup sqlite {SELECT host from resenders \
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WHERE helo='${quote_sqlite:$sender_helo_name}' \
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AND host='$sender_host_address';} {1}}
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@ -62,15 +93,28 @@ greylist_mail:
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# Attempt to look up this mail in the greylist database. If it's there,
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# remember the expiry time for it; we need to make sure they've waited
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# long enough.
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warn set acl_m_greyexpiry = ${lookup sqlite {GREYDB SELECT expire FROM greylist \
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warn set acl_m_greyexpiry = ${lookup sqlite {SELECT expire FROM greylist \
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WHERE id='${quote_sqlite:$acl_m_greyident}';}{$value}}
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# If there's absolutely nothing suspicious about the email, accept it. BUT...
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accept condition = ${if eq {$acl_m_greylistreasons}{} {1}}
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condition = ${if eq {$acl_m_greyexpiry}{} {1}}
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# ..if this same mail was greylisted before (perhaps because it came from a
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# host which *was* suspicious), then we still want to mark that original host
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# as a "known resender". If we don't, then hosts which attempt to deliver from
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# a dodgy Legacy IP address but then fall back to using IPv6 after greylisting
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# will *never* see their Legacy IP address added to the 'known resenders' list.
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accept condition = ${if eq {$acl_m_greylistreasons}{} {1}}
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acl = write_known_resenders
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# If the mail isn't already the database -- i.e. if the $acl_m_greyexpiry
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# variable we just looked up is empty -- then try to add it now. This is
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# where the 5 minute timeout is set ($tod_epoch + 300), should you wish
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# to change it.
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warn condition = ${if eq {$acl_m_greyexpiry}{} {1}}
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set acl_m_dontcare = ${lookup sqlite {GREYDB INSERT INTO greylist \
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set acl_m_dontcare = ${lookup sqlite {INSERT INTO greylist \
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VALUES ( '$acl_m_greyident', \
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'${eval10:$tod_epoch+300}', \
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'$sender_host_address', \
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@ -79,7 +123,7 @@ greylist_mail:
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# Be paranoid, and check if the insertion succeeded (by doing another lookup).
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# Otherwise, if there's a database error we might end up deferring for ever.
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defer condition = ${if eq {$acl_m_greyexpiry}{} {1}}
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condition = ${lookup sqlite {GREYDB SELECT expire FROM greylist \
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condition = ${lookup sqlite {SELECT expire FROM greylist \
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WHERE id='${quote_sqlite:$acl_m_greyident}';} {1}}
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message = Your mail was considered suspicious for the following reason(s):\n$acl_m_greylistreasons \
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The mail has been greylisted for 5 minutes, after which it should be accepted. \
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@ -105,13 +149,16 @@ greylist_mail:
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You should wait another ${eval10:$acl_m_greyexpiry-$tod_epoch} seconds.\n\
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Reason(s) for greylisting: \n$acl_m_greylistreasons
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accept acl = write_known_resenders
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write_known_resenders:
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# The message was listed but it's been more than five minutes. Accept it now and whitelist
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# the _original_ sending host by its { IP, HELO } so that we don't delay its mail again.
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warn set acl_m_orighost = ${lookup sqlite {GREYDB SELECT host FROM greylist \
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warn set acl_m_orighost = ${lookup sqlite {SELECT host FROM greylist \
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WHERE id='${quote_sqlite:$acl_m_greyident}';}{$value}}
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set acl_m_orighelo = ${lookup sqlite {GREYDB SELECT helo FROM greylist \
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set acl_m_orighelo = ${lookup sqlite {SELECT helo FROM greylist \
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WHERE id='${quote_sqlite:$acl_m_greyident}';}{$value}}
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set acl_m_dontcare = ${lookup sqlite {GREYDB INSERT INTO resenders \
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set acl_m_dontcare = ${lookup sqlite {INSERT INTO resenders \
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VALUES ( '$acl_m_orighost', \
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'${quote_sqlite:$acl_m_orighelo}', \
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'$tod_epoch' ); }}
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