tenshi.8

.\" SH section heading
.\" SS subsection heading
.\" LP paragraph
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.TH "tenshi" 8 "19 Oct 2017" "version 0.17"
.SH NAME
tenshi - Log Monitoring and Reporting tool
.SH SYNOPSIS
.B tenshi
.B [ -c
.I <conf file>
.B ]
.B [ -C ]
.B [ -d <debug level> ]
.B [ -f ]
.B [ -h ]
.B [ -p ]
.B [ -P <pid file> ]

.SH DESCRIPTION
.LP

tenshi is a log monitoring program, designed to watch one or more log files for
lines matching user defined regular expressions and report on the matches. The
regular expressions are assigned to queues which have an alert interval and a
list of mail recipients.

Queues can be set to send a notification as soon as there is a log line
assigned to it, or to send periodic reports.

Additionally, uninteresting fields in the log lines (such as PID numbers) can
be masked with the standard regular expression grouping operators ( ). This
allows cleaner and more readable reports. All reports are separated by hostname
and all messages are condensed when possible.

The program reads a configuration file
.RI ( tenshi.conf )
and then forks a deamon for monitoring the specified log files.

.SH OPTIONS
.SS
.TP
.I -c <conf file>
Read configuration from file. The default file is /etc/tenshi/tenshi.conf .
.TP
.I -C
Perform a syntax check of the configuration file. The program exits after
parsing the configuration with either a return code of 0 or an error.
.TP
.I -d <debug level>
Enable debug messages. Default level is 1 if none is specified, level 2 enables
SMTP connection debug messages. In this mode the main process remains in the
foreground.
.TP
.I -f
Enable foreground mode. In this mode the main process operates normally but
remains in the foreground, this is needed for some process supervisors.
.TP
.I -p
Enable profiling mode. In this mode the main process remains in the foreground
and expects log lines to be fed to standard in. When it receives an EOF it will
stop processing. No alerts will be sent in this mode, it is used solely for
measuring tenshi's line processing speed. For example:
time $(cat /var/log/messages|tenshi -p > /dev/null)
.TP
.I -P <pid file>
Define the file containing the PID of the process, this overrides any 'pidfile'
option present in the configuration file.

.SH CONFIGURATION FILE

.br
All directives are shown with the standard default value where applicable, if
omitted the default value will be used.

.I EXTERNAL CONFIGURATION FILES

.br
All configuration directives can be optionally split into different
configuration files and then read with the two following statements.

.TP
.I include <configuration file>
Parse the specified configuration file.
.TP
.I includedir <directory>
Parse all files inside <directory>. The files will be parsed in alphabetical
order, keep in mind that regexps order matters so
.I includedir
should be used carefully, see
.I REGEXP DEFINITIONS
for details.
.LP

.I STATIC OPTIONS

.br
These options will be set the first time tenshi reads its config file. They
cannot be changed by re-reading the config file. If you change one of these
options and HUP tenshi it will die. You have been warned.

.TP
.I set uid tenshi
Specify the effective user ID of the process when in daemon mode. The user must
be able to read the selected log files and the configuration file. Using a
privileged user is discouraged as it is not usually necessary (log files
permissions can be set accordingly with most syslog implementations).
.TP
.I set gid tenshi
Specify the effective group ID of the process when in daemon mode.
.TP
.I set pidfile /var/run/tenshi.pid
The file containing the PID of the process, useful for start/stop
scripts.
.TP
.I set listen 0.0.0.0:514
Enables syslog server mode. With this option tenshi will bind to the specified address:port
pair and read messages acting like a syslog server. We always recommend to filter the port
accordingly and possibly stunnel, or similar wrappers, to encrypt the traffic. This mode can
be used along with
.I logfile
,
.I fifo
and
.I redisqueue
settings.
.TP
.I set fifo <fifo path>
A FIFO file to monitor. This option allows you to use a syslog-ng
.I pipe()
destination (or any other syslog implementation that allows FIFO usage). This may be
specified multiple times to watch more than one fifo file. This option is meant to be used
only when the installed 'tail' binary doesn't behave properly with FIFOs, please
test your tail implementation before using this. This mode can be used along with
.I logfile
,
.I listen
and
.I redisqueue
settings.
.TP
.I set redisqueue <queue name>
Enables monitoring of logs consumed from a Redis queue of the given name, this may be specified
multiple times. See
.I redisserver
setting for instance specification. This mode can
be used along with
.I logfile
,
.I fifo
and
.I listen
settings.
.TP
.I set redisserver 127.0.0.1:6379
Specify the server path for the Redis instance to be used by the
.I redisqueue
setting. The parameter is passed to the new() method of the perl Redis binding, please refer to
its manual for accepted values. The setting typically accepts an address:port pair or socket path.
.LP

.I DYNAMIC OPTIONS

.br
These options are set each time the config file is read. tenshi reads its
config file once on start-up and whenever it receives a HUP.

.TP
.I set logfile <log file path>
A log file to monitor, this may be specified multiple times to watch more than
one log file. Depending on your tail implementation you might need to use the
.I tail_multiple
setting for multiple files to work. This mode can be used along with
.I fifo
,
.I listen
and
.I redisqueue
settings.
.TP
.I set tail /usr/bin/tail -q --follow=name --retry -n 0
Specify the path and arguments for the tail binary used for reading the log files. The invocation
must be tuned against your current 'tail' implementation. Default values are configured for standard
GNU coreutils tail. The
.I --follow=name
and
.I --retry
flags should deal properly with log rotation, if missing on your implementation we suggest that
you use 'cp /dev/null logfile', or similar techniques, as a safe way to clear the log file upon rotation.
.TP
.I set tail_multiple <on|off>
Some tail implementations do not handle more than one log file. When this option is enabled multiple
tail commands will be forked, instead of a single command with multiple arguments. This
option is disabled by default.
.TP
.I set tail_missing <on|off>
Sometimes a log file to be monitored will not exist until dynamically created by a process that
runs after tenshi starts. If tail_missing is on, a log file that does not exist at startup will
still be monitored rather than removed from the active log file list. Note this requires a tail
implementation, such as the standard GNU coreutils tail, which can start monitoring log files created
after it is run. This option is disabled by default.
.TP
.I set sleep 5
The loop sleep time for the notification process. The value must be \<\= 60 seconds.
.TP
.I set limit <number of lines>
The maximum number of messages per hostname allowed in a report, any lines
after the maximum will be omitted and a warning included. If this option is
omitted then no limit is applied.
.TP
.I set pager_limit <number of lines>
The maximum number of messages per hostname allowed in pager friendly reports,
any lines after the maximum will be omitted. If this option is omitted then no
limit is applied.
.TP
.I set logprefix <regexp>
All valid syslog messages are parsed by default, while non-syslog ones are
discarded unless the special
.I noprefix
queue is set. This option allows to define an additional valid prefix for watching
other type of logs. If the regexp is matched then the prefix is removed from
the log and the first grouped string is used for the hostname field. This may
be specified multiple times to watch many different non-syslog logs.
.TP
.I set mask ______
The mask for strings enclosed by the grouping operators ( ). See the
.I REGEXP DEFINITIONS
section. 'set mask' on its own will set the mask to an empty string.
.TP
.I set mailserver localhost
The mail server to be contacted for sending out reports.
.TP
.I set mailtimeout 10
The timeout in seconds for mail server reply.
.TP
.I set mailhelo localhost.localdomain
The client identification sent to the mailserver with the SMTP HELO command.
.TP
.I set subject tenshi report
The subject of report emails, the queue name is always automatically appended.
.TP
.I set hidepid <on|off>
This option turns on automatic stripping of 'foo[1234]:' style PID strings from
the start of log lines i.e. 'foo[1234]:' becomes 'foo:'. This allows you to
write regexps without worrying about masking the PID. Bear in mind that any time
you change this option you will need to re-write your regex rules or they will
not work. This option is disabled by default.
.TP
.I set filter <queue> <filter path> <arguments>
When this option is enabled all reports matching the specified queue will be passed
as STDIN to the specified filter, the resulting output is sent via smtp instead of
the original report. The full path of the filter application must be specified.
.TP
.I set csv <cron_spec> <filter path> <arguments>
This feature allows periodic reporting, using a five-field cron-style specification like
the
.I set queue
option, to the specified filter. The output is pre-formatted as CSV (Comma Separated Values)
with hostname,log,hits format. This feature was coded for using
.BI AfterGlow
.BI (http://afterglow.sf.net)
as a filter and graphing tenshi output. Check the FAQ for sample usage.
.TP
.I set sort_order <descending|ascending>
The sorting order for reports. It can be either descending or ascending, the
number of messages is used as a key for sorting the log messages. The default
order is ascending.
.TP
.I set resolve <on|off>
This option turns on resolution of the fully qualified domain name for the hostname passed along
with log messages and, if found, reports it along with the original one. This only affects reports
and not pager messages. The name resolution is cached in order to avoid re-resolving addresses that
have been seen already, you have to restart or HUP tenshi in order to flush the cache. This option
is disabled by default.
.TP
.I set threshold <queue> <count> <regex>
This option can be used to discard lines from a report that have a count below
the given threshold. If a line matches the regex in the given queue but has
fewer hits than count, it is discarded and omitted from the report. Note that
this matches on the content of the lines that will actually appear in the
report, in contrast to queue escalation which uses a count based on the regex
that is matched.
.LP

.I QUEUES OPTIONS
.br

.br
All messages are assigned to queues. Every queue is processed periodically
according to its notification interval. There are four default builtin queues,
.I trash
to which unwanted messages can be assigned (think /dev/null),
.I repeat
which is used for smart repeat messages handling,
.I group
and
.I group_host
, see
.I REGEXP DEFINITIONS
for details. There's also a special
.I noprefix
queue, read further for details about it.
.br

All queues are automatically flushed before shutdown when a SIGTERM is
received. Please see section
.I SIGNALS
for additional information.

The syntax is the following:
.TP
.I set queue <queue_name> <mail_from> [pager:]<mail_to> <cron_spec> [<subject>]
.TP
.I <queue_name>
The queue name. Can be any alphanumeric character string except for the builtin
queues name.
.TP
.I <mail_from>
The mail sender for reports related to the queue.
.TP
.I <mail_to>
The mail recipient(s) for reports related to the queue. Multiple address can be
specified, separated by commas. Using the
.I pager:
prefix enables a pager friendly report.
.TP
.I [<cron_spec>]
This is a five-field cron-style specification for when the reports should be
emailed. Ranges and skip values are supported as per the de facto crontab
syntax with a few exceptions. Please see
.I crontab
man page for crontab syntax explanation. The supported day names are: Mon, Tue,
Wed, Thu, Fri, Sat, Sun. Monday is 1, Sunday 0 or 7. Supported month names
are: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec. Day and Month
names are not case sensitive. Additionally, 'now' can be specified for
immediate notifications.
.TP
.I <subject>
This is the subject for to use for email reports regarding this queue. If this
isn't specified then the default subject will be used.
.LP

The special
.I noprefix
queue can be used and defined like any other queue with the difference that it will get
all messages that don't match any configured prefix.

Examples:
.br
set queue report tenshi@localhost sysadmin@localhost [0 9-17 * * *]
.br
set queue report tenshi@localhost sysadmin@localhost [30 18 * * *]
.br
set queue report tenshi@localhost sysadmin@localhost [*/10 * * * *]
.br
set queue critical tenshi@localhost sysadmin@localhost,noc@localhost [now] CRITICAL WARNING -
.br
set queue pager tenshi@localhost pager:sysadmin_pager@localhost,pager:noc_pager@localhost [now] ALERT
.LP

.I REGEXP DEFINITIONS
.br

.br
All valid syslog messages are matched against standard perl regexps, all
regexps are defined with the following syntax:
.TP
.I <queue_name>[,<queue_name>[:<escalation_number>]..] <regexp>
.LP

The regexps are evaluated in order so a matched message is not checked against
the subsequent regexps. Keep this in mind when assembling the configuration
file. It's advisable to catch all messages by placing an all matching regexp at
the end of the configuration file. It's also good for performance having trash
rules not logically connected with other matching rules at the beginning of the
section. Multiple queues can be defined with a comma separated list, builtin
queues cannot be used when using this syntax.

.br
If an escalation number is provided for a queue, the matched message will only
be placed into the queue when <escalation_number> messages have matched the
regexp. The queue will receive the message that matched the regexp at the time
of escalation, with a count equal to the escalation number. The count of
messages matching the regexp will be reset when the left most queue mentioned
in the queue list is mailed. The left most queue cannot have an escalation
number unless it is the only queue listed. When the number of messages that
match the regexp reaches the greatest escalation number mentioned, escalation
will begin again into the escalation queues, modulus the greatest escalation
number. For example, using the queues `a,b:10,c:50', when 10 messages match the
regexp, a message will go into b, when 50 match, one will go into c. At 60,
another will go into b, and at 100, another into c, 110 to b, 150 to c, and so
on. Escalation numbers must be positive integers greater than zero and must be
listed in increasing order from left to right. All queues without escalation
numbers must be listed more left than the queues with escalation numbers.

.br
The standard grouping operators
.I ( )
can be used for string masking, literal "(" and ")" can be protected with the
standard quotation operator "\\". There's a lot of documentation about regular
expressions, a good start could be perl
.I perlre
and
.I perlretut
manual pages.
.br
You can also use the (?: ) operators to use groups without masking. This allows
you to match, for example, output from several programs in a similar format.
There is an example of this below (the sudo/su line).

.br
The builtin queue
.I repeat
can be used for special handling of "last message repeated x times" style log
lines. When the assigned regexps are matched the line count for the last line
received from the same host is incremented by the first grouped string. Keep in
mind that it is possible for syslog lines to be received from remote hosts out
of order. If this happens you should not use this feature because tenshi will
mis-report line counts.

.br
The builtin queue
.I group
can be used to group sets of regex together to speed up line matching. If a
line fails to match a regex assigned to the group queue then tenshi will skip
all the regex up until the next
.I group_end
statement. Nested groups are allowed. An example of this is included below.

.br
The builtin
.I group_host
queue can be used for selective hostname matching. Like the
.I group
queue it is also terminated with the
.I group_end
statement. All regex definitions within that group will only apply if the hostname
associated to the log entries matches the regex passed to the
.I group_host
definition.

.br
The regexps below assume
.I hidepid
is turned on. If you have it turned off then you will need to add in \\[(.+)\\]
to the regex following the progam name to get them to work.
.br
For example:
mail ^sendmail: (.+): to=(.+),(.+)delay=(.+)
becomes:
mail ^sendmail\\[(.+)\\]: (.+): to=(.+),(.+)delay=(.+)

Examples:

.br
trash ^xinetd

.br
repeat ^(?:last message repeated|above message repeats) (\\d+) time

.br
group ^sendmail:
.br
mail ^sendmail: (.+): to=(.+),(.+)delay=(.+)
.br
mail ^sendmail: (.+): to=(.+),(.+)relay=(.+),(.+)stat=Sent
.br
group_end

.br
group_host mailserver1
.br
mail1 ^sendmail
.br
mail1 ^sendmail:.+
.br
critical,mail1 ^sendmail:.+SYSERR.+
.br
group_end

.br
mail ^ipop3d: Login user=(.+)

.br
critical,report ^sshd: Illegal user

.br
general,urgent:200,critical:1000 ^sshd: Illegal user

.br
root ^sshd\\(pam_unix\\): session opened for user root by root\\(uid=0\\)

.br
report ^sshd: Accepted rsa for (.+) from (.+) port (.+)

.br
trash ^sshd

.br
critical ^(?:sudo|su):

.br
critical,pager ^Oops

.br
misc .*


.SH SIGNALS
.br
tenshi can handle different signals sent to the process, here's the list of
supported ones:

.TP
.B TERM
flush all queues and then exit
.TP
.B INT
flush all queues and then exit
.TP
.B USR1
flush any queues which have reached their notification interval
.TP
.B USR2
force all queues to be flushed, even if they have not reached their
notification interval
.TP
.B HUP
force all queues to be flushed, even if they have not reached their
notification interval, re-read the config file and continue as normal.
.LP
.I WARNING:
If you change a STATIC OPTION in the config file and send tenshi a HUP it will
die. You will need to restart tenshi for changes to STATIC OPTIONs to take
effect.

.SH EXAMPLES
See the included tenshi.conf.

.SH REQUIREMENTS

- Perl.
.br

- A working 'tail' implementation, when using the
.I logfile
option.
.br

- The Net::SMTP perl module to mail reports, typically included
in perl installations.

- The IO::BufferedSelect perl module.

- The Redis perl module, when using the
.I redisqueue
option.

Any missing module can be downloaded from CPAN (http://www.cpan.org) or installed
using the CPAN shell (`perl -e shell -MCPAN`).

.SH BUGS
Double quote characters present in your logs might break csv output (depending on how you pipe/process
it in the filter) since there's no escape code (yet).

Please report any bugs you find at
.BI <andrea@inversepath.com>

.SH LICENSE
.B tenshi
is distributed under the terms of the following ISC-style license:

Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

.SH DISTRIBUTION

The tenshi repository is hosted at
.BI https://github.com/f-secure-foundry/tenshi

.SH NOTES

tenshi was once known as
.I wasabi.
The name was changed due to a trademark claim relating to another piece of software.

.SH SEE ALSO

It should be noted that tenshi was initially a perl rewrite of
.I oak
.RI ( http://www.ktools.org ).

.I Friedl, Jeffrey E. F. Mastering Regular Expressions, 2nd Edition. O'Reilly

.SH AUTHORS

Copyright (c) Andrea Barisani <andrea@inversepath.com>