Thanks for your help.
I've attached the file I got from "exim4 -bP config...".
I'm expecting that any email incoming from my own host (not from
pipeline), whose local part begins with a "." or that contains any of
these "@%!/|`#&?" characters, is going to be blocked.
If the mail is coming from other hosts, I'm expecting that it should be
blocked if the local part begins with any of these "./|", or if it
contains any of these "@%!`#&?" or if it contains the sequence "/../".
The problem is that this is not happening and I can receive any email,
regardless the characters contained in the local parts. I tested it
using a remote client of the same host, and from other hosts.
This is just a virtual machine I use for testing purposes; so I can even
attach the config file containing the real domain if necessary. The same
thing happens even with my "real" servers I only use for personal
purposes. So I assume there is some nuance in the config file I don't
understand.
As far as I know, if in the main part of the config file there is:
acl_smtp_rcpt = acl_check_rcpt
it means that the acl acl_check_rcpt should be applied for every
incoming email.
Cheers
Ale
On 02/06/22 15:53, Jeremy Harris via Exim-users wrote:
> On 01/06/2022 16:28, Alessandro via Exim-users wrote:
>> I installed exim4 4.94.2 on a debian 11.3 machine. I configured it
>> using exim4-config as straight smtp mta. I have just declared a few
>> macros on the exim4.conf.localmacros, so basically I'm using the
>> default configuration created by exim4-config. I've been trying to
>> understand the acl_check_rcpt acl, specifically the part that should
>> be "guarding against incoming rogue local parts"
>
> Run "exim -bP config >my_resolved_config"
>
> (it might be called exim4 rather than exim on your machine, despite
> exim version 3 having gone out of date twenty years ago...)
>
> This gives a file of the configuration with all the .ifdefs resolved,
> which would probably be earier to read than what I've seen of
> the Debian auto-generated one.
>
>> The problem is that it's not working
>
> What is it doing or not doing, versus your expectations?# Exim Configuration (4.94.2)
# 1 "/var/lib/exim4/config.autogenerated"
MAIN_TLS_ENABLE = yes
DKIM_CANON = relaxed
DKIM_SELECTOR = default
DKIM_DOMAIN = mydomain
DKIM_FILE = /etc/exim4/dkim/dkim.pem
DKIM_PRIVATE_KEY = /etc/exim4/dkim/dkim.pem
REMOTE_SMTP_HELO_DATA = mydomain
MAIN_TLS_CERTIFICATE = /etc/letsencrypt/live/mydomain/fullchain.pem
MAIN_TLS_PRIVATEKEY = /etc/letsencrypt/live/mydomain/privkey.pem
MAIN_QUALIFY_DOMAIN = mydomain
TLS_ON_CONNECT_PORTS = 465
CHECK_RCPT_IP_DNSBLS = zen.spamhaus.org
MAIN_LOCAL_DOMAINS = mydomain
exim_path = /usr/sbin/exim4
CONFDIR = /etc/exim4
disable_ipv6 = true
UPEX4CmacrosUPEX4C = 1
MAIN_PACKAGE_VERSION=4.94.2-7
MAIN_RELAY_TO_DOMAINS=
ETC_MAILNAME=mydomain
LOCAL_DELIVERY=maildir_home
MAIN_RELAY_NETS=: 127.0.0.1 : ::::1
DCreadhost=
DCsmarthost=
DC_eximconfig_configtype=internet
DCconfig_internet=1
domainlist local_domains = mydomain
domainlist relay_to_domains =
hostlist relay_from_hosts = : 127.0.0.1 : ::::1
qualify_domain = mydomain
gecos_pattern = ^([^,:]*)
gecos_name = $1
MAIN_LOG_SELECTOR = +smtp_protocol_error +smtp_syntax_error +tls_certificate_verified +tls_peerdn
MAIN_ACL_CHECK_MAIL = acl_check_mail
acl_smtp_mail = acl_check_mail
MAIN_ACL_CHECK_RCPT = acl_check_rcpt
acl_smtp_rcpt = acl_check_rcpt
MAIN_ACL_CHECK_DATA = acl_check_data
acl_smtp_data = acl_check_data
MAIN_HOST_LOOKUP = *
host_lookup = *
dns_dnssec_ok = 1
prdr_enable = true
local_from_check = false
local_sender_retain = true
untrusted_set_sender = *
MAIN_IGNORE_BOUNCE_ERRORS_AFTER = 2d
ignore_bounce_errors_after = 2d
MAIN_TIMEOUT_FROZEN_AFTER = 7d
timeout_frozen_after = 7d
MAIN_FREEZE_TELL = postmaster
freeze_tell = postmaster
SPOOLDIR = /var/spool/exim4
spool_directory = /var/spool/exim4
MAIN_TRUSTED_USERS = uucp
trusted_users = uucp
keep_environment =
MAIN_SMTPUTF8_ADVERTISE_HOSTS =
smtputf8_advertise_hosts =
MAIN_TLS_ADVERTISE_HOSTS = *
tls_advertise_hosts = *
tls_certificate = /etc/letsencrypt/live/mydomain/fullchain.pem
tls_privatekey = /etc/letsencrypt/live/mydomain/privkey.pem
MAIN_TLS_VERIFY_CERTIFICATES = ${if exists{/etc/ssl/certs/ca-certificates.crt}{/etc/ssl/certs/ca-certificates.crt}{/dev/null}}
tls_verify_certificates = ${if exists{/etc/ssl/certs/ca-certificates.crt}{/etc/ssl/certs/ca-certificates.crt}{/dev/null}}
log_selector = +smtp_protocol_error +smtp_syntax_error +tls_certificate_verified +tls_peerdn
begin acl
acl_local_deny_exceptions:
accept
hosts = ${if exists{/etc/exim4/host_local_deny_exceptions}{/etc/exim4/host_local_deny_exceptions}{}}
accept
senders = ${if exists{/etc/exim4/sender_local_deny_exceptions}{/etc/exim4/sender_local_deny_exceptions}{}}
accept
hosts = ${if exists{/etc/exim4/local_host_whitelist}{/etc/exim4/local_host_whitelist}{}}
accept
senders = ${if exists{/etc/exim4/local_sender_whitelist}{/etc/exim4/local_sender_whitelist}{}}
acl_check_mail:
accept
CHECK_RCPT_LOCAL_LOCALPARTS = ^[.] : ^.*[@%!/|`#&?]
CHECK_RCPT_REMOTE_LOCALPARTS = ^[./|] : ^.*[@%!`#&?] : ^.*/\\.\\./
acl_check_rcpt:
accept
hosts = :
control = dkim_disable_verify
deny
domains = +local_domains
local_parts = ^[.] : ^.*[@%!/|`#&?]
message = restricted characters in address
deny
domains = !+local_domains
local_parts = ^[./|] : ^.*[@%!`#&?] : ^.*/\\.\\./
message = restricted characters in address
accept
local_parts = postmaster
domains = +local_domains : +relay_to_domains
deny
!acl = acl_local_deny_exceptions
senders = ${if exists{/etc/exim4/local_sender_callout}{/etc/exim4/local_sender_callout}{}}
!verify = sender/callout
deny condition = ${if and {{>{$rcpt_count}{10}}{<{$recipients_count}{${eval:$rcpt_count/2}}} }}
message = Rejected for too many bad recipients
logwrite = REJECT [$sender_host_address]: bad recipient count high [${eval:$rcpt_count-$recipients_count}]
accept
hosts = +relay_from_hosts
control = submission/sender_retain
control = dkim_disable_verify
accept
authenticated = *
control = submission/sender_retain
control = dkim_disable_verify
require
condition = ${if def:sender_helo_name}
message = nice hosts say HELO first
require
message = relay not permitted
domains = +local_domains : +relay_to_domains
require
verify = recipient
deny
!acl = acl_local_deny_exceptions
recipients = ${if exists{/etc/exim4/local_rcpt_callout}{/etc/exim4/local_rcpt_callout}{}}
!verify = recipient/callout
deny
!acl = acl_local_deny_exceptions
senders = ${if exists{/etc/exim4/local_sender_blacklist}{/etc/exim4/local_sender_blacklist}{}}
message = sender envelope address $sender_address is locally blacklisted here. If you think this is wrong, get in touch with postmaster
log_message = sender envelope address is locally blacklisted.
deny
!acl = acl_local_deny_exceptions
hosts = ${if exists{/etc/exim4/local_host_blacklist}{/etc/exim4/local_host_blacklist}{}}
message = sender IP address $sender_host_address is locally blacklisted here. If you think this is wrong, get in touch with postmaster
log_message = sender IP address is locally blacklisted.
warn
dnslists = zen.spamhaus.org
add_header = X-Warning: $sender_host_address is listed at $dnslist_domain ($dnslist_value: $dnslist_text)
log_message = $sender_host_address is listed at $dnslist_domain ($dnslist_value: $dnslist_text)
accept
domains = +relay_to_domains
endpass
verify = recipient
accept
acl_check_data:
deny
condition = ${if > {$max_received_linelength}{998}}
message = maximum allowed line length is 998 octets, got $max_received_linelength
deny
!acl = acl_local_deny_exceptions
!verify = header_syntax
message = header syntax
log_message = header syntax ($acl_verify_message)
accept
begin routers
hubbed_hosts:
debug_print = "R: hubbed_hosts for $domain"
driver = manualroute
domains = "${if exists{/etc/exim4/hubbed_hosts}{partial-lsearch;/etc/exim4/hubbed_hosts}fail}"
same_domain_copy_routing = yes
route_data = ${lookup{$domain}partial-lsearch{/etc/exim4/hubbed_hosts}}
transport = remote_smtp
dnslookup_relay_to_domains:
debug_print = "R: dnslookup_relay_to_domains for $local_part@$domain"
driver = dnslookup
domains = ! +local_domains : +relay_to_domains
transport = remote_smtp
same_domain_copy_routing = yes
no_more
ROUTER_DNSLOOKUP_IGNORE_TARGET_HOSTS = <; 0.0.0.0 ; 127.0.0.0/8 ; 192.168.0.0/16 ; 172.16.0.0/12 ; 10.0.0.0/8 ; 169.254.0.0/16 ; 255.255.255.255 ; ::/128 ; ::1/128 ; fc00::/7 ; fe80::/10 ; 100::/64
dnslookup:
debug_print = "R: dnslookup for $local_part@$domain"
driver = dnslookup
domains = ! +local_domains
transport = remote_smtp
same_domain_copy_routing = yes
ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; 192.168.0.0/16 ; 172.16.0.0/12 ; 10.0.0.0/8 ; 169.254.0.0/16 ; 255.255.255.255 ; ::/128 ; ::1/128 ; fc00::/7 ; fe80::/10 ; 100::/64
no_more
COND_LOCAL_SUBMITTER = "${if match_ip{$sender_host_address}{:@[]}{1}{0}}"
real_local:
debug_print = "R: real_local for $local_part@$domain"
driver = accept
domains = +local_domains
condition = "${if match_ip{$sender_host_address}{:@[]}{1}{0}}"
local_part_prefix = real-
check_local_user
transport = maildir_home
system_aliases:
debug_print = "R: system_aliases for $local_part@$domain"
driver = redirect
domains = +local_domains
allow_fail
allow_defer
data = ${lookup{$local_part}lsearch{/etc/aliases}}
userforward:
debug_print = "R: userforward for $local_part@$domain"
driver = redirect
domains = +local_domains
check_local_user
file = $home/.forward
require_files = $local_part_data:$home/.forward
no_verify
no_expn
check_ancestor
allow_filter
forbid_smtp_code = true
directory_transport = address_directory
file_transport = address_file
pipe_transport = address_pipe
reply_transport = address_reply
skip_syntax_errors
syntax_errors_to = real-$local_part@$domain
syntax_errors_text = This is an automatically generated message. An error has\nbeen found in your .forward file. Details of the error are\nreported below. While this error persists, you will receive\na copy of this message for every message that is addressed\nto you. If your .forward file is a filter file, or if it is\na non-filter file containing no valid forwarding addresses,\na copy of each incoming message will be put in your normal\nmailbox. If a non-filter file contains at least one valid\nforwarding address, forwarding to the valid addresses will\nhappen, and those will be the only deliveries that occur.
procmail:
debug_print = "R: procmail for $local_part@$domain"
driver = accept
domains = +local_domains
check_local_user
transport = procmail_pipe
require_files = ${local_part_data}:${if exists{/etc/procmailrc}{/etc/procmailrc}{${home}/.procmailrc}}:+/usr/bin/procmail
no_verify
no_expn
maildrop:
debug_print = "R: maildrop for $local_part@$domain"
driver = accept
domains = +local_domains
check_local_user
transport = maildrop_pipe
require_files = ${local_part_data}:${home}/.mailfilter:+/usr/bin/maildrop
no_verify
no_expn
FIRST_USER_ACCOUNT_UID = 0
DEFAULT_SYSTEM_ACCOUNT_ALIAS = :fail: no mail to system accounts
COND_SYSTEM_USER_AND_REMOTE_SUBMITTER = "${if and{{! match_ip{$sender_host_address}{:@[]}}{<{$local_user_uid}{0}}}{1}{0}}"
lowuid_aliases:
debug_print = "R: lowuid_aliases for $local_part@$domain (UID $local_user_uid)"
check_local_user
driver = redirect
allow_fail
domains = +local_domains
condition = "${if and{{! match_ip{$sender_host_address}{:@[]}}{<{$local_user_uid}{0}}}{1}{0}}"
data = ${if exists{/etc/exim4/lowuid-aliases}{${lookup{$local_part}lsearch{/etc/exim4/lowuid-aliases}{$value}{:fail: no mail to system accounts}}}{:fail: no mail to system accounts}}
local_user:
debug_print = "R: local_user for $local_part@$domain"
driver = accept
domains = +local_domains
check_local_user
local_parts = ! root
transport = maildir_home
cannot_route_message = Unknown user
mail4root:
debug_print = "R: mail4root for $local_part@$domain"
driver = redirect
domains = +local_domains
data = /var/mail/mail
file_transport = address_file
local_parts = root
user = mail
group = mail
begin transports
REMOTE_SMTP_SMARTHOST_TLS_VERIFY_HOSTS = *
address_file:
debug_print = "T: address_file for $local_part@$domain"
driver = appendfile
delivery_date_add
envelope_to_add
return_path_add
address_pipe:
debug_print = "T: address_pipe for $local_part@$domain"
driver = pipe
return_fail_output
address_reply:
debug_print = "T: autoreply for $local_part@$domain"
driver = autoreply
mail_spool:
debug_print = "T: appendfile for $local_part@$domain"
driver = appendfile
file = /var/mail/$local_part_data
delivery_date_add
envelope_to_add
return_path_add
group = mail
mode = 0660
mode_fail_narrower = false
maildir_home:
debug_print = "T: maildir_home for $local_part@$domain"
driver = appendfile
directory = $home/Maildir
delivery_date_add
envelope_to_add
return_path_add
maildir_format
directory_mode = 0700
mode = 0600
mode_fail_narrower = false
maildrop_pipe:
debug_print = "T: maildrop_pipe for $local_part@$domain"
driver = pipe
path = "/bin:/usr/bin:/usr/local/bin"
command = "/usr/bin/maildrop"
message_prefix =
message_suffix =
return_path_add
delivery_date_add
envelope_to_add
procmail_pipe:
debug_print = "T: procmail_pipe for $local_part@$domain"
driver = pipe
path = "/bin:/usr/bin:/usr/local/bin"
command = "/usr/bin/procmail"
return_path_add
delivery_date_add
envelope_to_add
remote_smtp:
debug_print = "T: remote_smtp for $local_part@$domain"
driver = smtp
message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
helo_data=mydomain
dkim_domain = mydomain
dkim_selector = default
dkim_private_key = /etc/exim4/dkim/dkim.pem
dkim_canon = relaxed
remote_smtp_smarthost:
debug_print = "T: remote_smtp_smarthost for $local_part@$domain"
driver = smtp
multi_domain
message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
hosts_try_auth = <; ${if exists{/etc/exim4/passwd.client} {${lookup{$host}nwildlsearch{/etc/exim4/passwd.client}{$host_address}}}{} }
tls_verify_hosts = *
helo_data=mydomain
address_directory:
debug_print = "T: address_directory for $local_part@$domain"
driver = appendfile
delivery_date_add
envelope_to_add
return_path_add
check_string = ""
escape_string = ""
maildir_format
begin retry
* * F,2h,15m; G,16h,1h,1.5; F,4d,6h
begin rewrite
*@+local_domains "${lookup{${local_part}}lsearch{/etc/email-addresses}{$value}fail}" Ffrs
*@domumia.dynu.net "${lookup{${local_part}}lsearch{/etc/email-addresses}{$value}fail}" Ffrs
begin authenticators
login_server:
driver = plaintext
public_name = LOGIN
server_prompts = "Username:: : Password::"
server_condition = "${if crypteq{$auth2}{${extract{1}{:}{${lookup{$auth1}lsearch{/etc/exim4/passwd}{$value}{*:*}}}}}{1}{0}}"
server_set_id = $auth1
server_advertise_condition = ${if eq{$tls_in_cipher}{}{}{*}}
cram_md5:
driver = cram_md5
public_name = CRAM-MD5
client_name = ${extract{1}{:}{${lookup{$host}nwildlsearch{/etc/exim4/passwd.client}{$value}fail}}}
client_secret = ${extract{2}{:}{${lookup{$host}nwildlsearch{/etc/exim4/passwd.client}{$value}fail}}}
PASSWDLINE=${sg{${lookup{$host}nwildlsearch{/etc/exim4/passwd.client}{$value}fail}}{\\N[\\^]\\N}{^^}}
plain:
driver = plaintext
public_name = PLAIN
client_send = "<; ${if !eq{$tls_out_cipher}{}{^${extract{1}{:}{${sg{${lookup{$host}nwildlsearch{/etc/exim4/passwd.client}{$value}fail}}{\\N[\\^]\\N}{^^}}}}^${sg{${sg{${lookup{$host}nwildlsearch{/etc/exim4/passwd.client}{$value}fail}}{\\N[\\^]\\N}{^^}}}{\\N([^:]+:)(.*)\\N}{\\$2}}}fail}"
login:
driver = plaintext
public_name = LOGIN
client_send = "<; ${if and{{!eq{$tls_out_cipher}{}}{!eq{${sg{${lookup{$host}nwildlsearch{/etc/exim4/passwd.client}{$value}fail}}{\\N[\\^]\\N}{^^}}}{}}}{}fail}; ${extract{1}{::}{${sg{${lookup{$host}nwildlsearch{/etc/exim4/passwd.client}{$value}fail}}{\\N[\\^]\\N}{^^}}}}; ${sg{${sg{${lookup{$host}nwildlsearch{/etc/exim4/passwd.client}{$value}fail}}{\\N[\\^]\\N}{^^}}}{\\N([^:]+:)(.*)\\N}{\\$2}}"
