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479 lines
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/ _|__ _(_) |_ ) |__ __ _ _ _
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================================================================================
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How to develop for Fail2Ban
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================================================================================
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Fail2Ban uses GIT (http://git-scm.com/) distributed source control. This gives
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each developer their own complete copy of the entire repository. Developers can
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add and switch branches and commit changes when ever they want and then ask a
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maintainer to merge their changes.
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Fail2Ban uses GitHub (https://github.com/fail2ban/fail2ban) to manage access to
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the Git repository. GitHub provides free hosting for open-source projects as
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well as a web-based Git repository browser and an issue tracker.
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If you are familiar with Python and you have a bug fix or a feature that you
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would like to add to Fail2Ban, the best way to do so it to use the GitHub Pull
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Request feature. You can find more details on the Fail2Ban wiki
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(http://www.fail2ban.org/wiki/index.php/Get_Involved)
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Pull Requests
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=============
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When submitting pull requests on GitHub we ask you to:
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* Clearly describe the problem you're solving;
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* Don't introduce regressions that will make it hard for systems adminstrators
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to update;
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* If adding a major feature rebase your changes on master and get to a single commit;
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* Include test cases (see below);
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* Include sample logs (if relevant);
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* Include a change to the relevant section of the ChangeLog; and
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* Include yourself in THANKS if not already there.
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Filters
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=======
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* Include sample logs with 1.2.3.4 used for IP addresses and
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example.com/example.org used for DNS names
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* Ensure ./fail2ban-regex testcases/files/logs/{samplelog} config/filter.d/{filter}.conf
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has matches for EVERY regex
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* Ensure regexs start with a ^ and are restrictive as possible. E.g. not .* if
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\d+ is sufficient
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* Use the functionality of regexs http://docs.python.org/2/library/re.html
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* Take a look at the source code of the application. You may see optional or
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extra log messages, or parts there of, that need to form part of your regex.
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If you only have a basic knowledge of regular repressions read
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http://docs.python.org/2/library/re.html first.
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Filter Security
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---------------
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Poor filter regular expressions are suseptable to DoS attacks.
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When a remote user has the ability to introduce text that will match the
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filter regex, such that the inserted text matches the <HOST> part, they have the
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ability to deny any host they choose.
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So the <HOST> part must be anchored on text generated by the application, and not
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the user, to a sufficient extent that the user cannot insert the entire text.
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Filters are matched against the log line with their date removed.
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Ideally filter regex should anchor to the beginning and end of the log line
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however as more applications log at the beginning than the end, achoring the
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beginning is more important. If the log file used by the application is shared
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with other applications, like system logs, ensure the other application that
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use that log file do not log user generated text at the beginning of the line,
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or, if they do, ensure the regexs of the filter are sufficient to mitigate the
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risk of insertion.
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When creating a regex that extends back to the begining remember the date part
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has been removed within fail2ban so theres no need to match that. If the format
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is like '<date...> error 1.2.3.4 is evil' then you will need to match the < at
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the start so here the regex would start like '^<> <HOST> is evil$'.
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Some applications log spaces at the end. If you're not sure add \s*$ as the
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end part of the regex.
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Examples of poor filters
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------------------------
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1. Too restrictive
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We find a log message:
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Apr-07-13 07:08:36 Invalid command fial2ban from 1.2.3.4
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We make a failregex
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^Invalid command \S+ from <HOST>
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Now think evil. The user does the command 'blah from 1.2.3.44'
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The program diliently logs:
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Apr-07-13 07:08:36 Invalid command blah from 1.2.3.44 from 1.2.3.4
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And fail2ban matches 1.2.3.44 as the IP that it ban. A DoS attack was successful.
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The fix here is that the command can be anything so .* is approprate.
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^Invalid command .* from <HOST>
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Here the .* will match until the end of the string. Then realise it has more to
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match, i.e. "from <HOST>" and go back until it find this. Then it will ban
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1.2.3.4 correctly. Since the <HOST> is always at the end, end the regex with a $.
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^Invalid command .* from <HOST>$
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Note if we'd just had the expression:
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^Invalid command \S+ from <HOST>$
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Then provided the user put a space in their command they would have never been
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banned.
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2. Filter regex can match other user injected data
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From the apache vulnerability CVE-2013-2178
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( original ref: https://vndh.net/note:fail2ban-089-denial-service ).
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An example bad regex for apache:
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failregex = [[]client <HOST>[]] user .* not found
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Since the user can do a get request on:
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GET /[client%20192.168.0.1]%20user%20root%20not%20found HTTP/1.0
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Host: remote.site
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Now the log line will be:
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[Sat Jun 01 02:17:42 2013] [error] [client 192.168.33.1] File does not exist: /srv/http/site/[client 192.168.0.1] user root not found
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As this log line doesn't match other expressions hence it matches the above
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regex and blocks 192.168.33.1 as a denial of service from the HTTP requester.
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3. Applicaiton generates two identical log messages with different meanings
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If the application generates the following two messages under different
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circmstances:
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client <IP>: authentication failed
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client <USER>: authentication failed
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Then it's obvious that a regex of "^client <HOST>: authentication
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failed$" will still cause problems if the user can trigger the second
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log message with a <USER> of 123.1.1.1.
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Here there's nothing to do except request/change the application so it logs
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messages differently.
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Code Testing
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============
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Existing tests can be run by executing `fail2ban-testcases`. This has options
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like --log-level that will probably be useful. `fail2ban-testcases --help` for
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full options.
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Test cases should cover all usual cases, all exception cases and all inside
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/ outside boundary conditions.
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Test cases should cover all branches. The coverage tool will help identify
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missing branches. Also see http://nedbatchelder.com/code/coverage/branch.html
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for more details.
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Install the package python-coverage to visualise your test coverage. Run the
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following (note: on Debian-based systems, the script is called
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`python-coverage`):
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coverage run fail2ban-testcases
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coverage html
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Then look at htmlcov/index.html and see how much coverage your test cases
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exert over the codebase. Full coverage is a good thing however it may not be
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complete. Try to ensure tests cover as many independent paths through the
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code.
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Manual Execution. To run in a development environment do:
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./fail2ban-client -c config/ -s /tmp/f2b.sock -i start
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some quick commands:
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status
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add test pyinotify
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status test
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set test addaction iptables
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set test actionban iptables echo <ip> <cidr> >> /tmp/ban
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set test actionunban iptables echo <ip> <cidr> >> /tmp/unban
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get test actionban iptables
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get test actionunban iptables
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set test banip 192.168.2.2
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status test
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Coding Standards
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================
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Style
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-----
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Please use tabs for now. Keep to 80 columns, at least for readable text.
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Tests
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-----
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Add tests. They should test all the code you add in a meaning way.
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Coverage
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--------
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Test coverage should always increase as you add code.
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You may use "# pragma: no cover" in the code for branches of code that support
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older versions on python. For all other uses of "pragma: no cover" or
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"pragma: no branch" document the reason why its not covered. "I haven't written
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a test case" isn't a sufficient reason.
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Documentation
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-------------
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Ensure this documentation is up to date after changes. Also ensure that the man
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pages still are accurate. Ensure that there is sufficient documentation for
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your new features to be used.
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Bugs
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----
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Remove them and don't add any more.
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Git
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---
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Use the following tags in your commit messages:
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'BF:' for bug fixes
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'DOC:' for documentation fixes
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'ENH:' for enhancements
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'TST:' for commits concerning tests only (thus not touching the main code-base)
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Multiple tags could be joined with +, e.g. "BF+TST:".
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Use the text "closes #333"/"resolves #333 "/"fixes #333" where 333 represents
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an issue that is closed. Other text and details in link below.
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See: https://help.github.com/articles/closing-issues-via-commit-messages
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Adding Actions
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--------------
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If you add an action.d/*.conf file also add a example in config/jail.conf
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with enabled=false and maxretry=5 for ssh.
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Design
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======
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Fail2Ban was initially developed with Python 2.3 (IIRC). It should
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still be compatible with Python 2.4 and such compatibility assurance
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makes code ... old-fashioned in many places (RF-Note). In 0.7 the
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design went through major refactoring into client/server,
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a-thread-per-jail design which made it a bit difficult to follow.
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Below you can find a sketchy description of the main components of the
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system to orient yourself better.
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server/
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------
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Core classes hierarchy (feel welcome to draw a better/more complete
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one)::
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-> inheritance
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+ delegation
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* storage of multiple instances
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RF-Note just a note which might be useful to address while doing RF
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JailThread -> Filter -> FileFilter -> {FilterPoll, FilterPyinotify, ...}
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| * FileContainer
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+ FailManager
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+ DateDetector
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+ Jail (provided in __init__) which contains this Filter
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(used for passing tickets from FailManager to Jail's __queue)
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Server
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+ Jails
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* Jail
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+ Filter (in __filter)
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* tickets (in __queue)
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+ Actions (in __action)
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* Action
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+ BanManager
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failmanager.py
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~~~~~~~~~~~~~~
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FailManager
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Keeps track of failures, recorded as 'tickets'. All operations are
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done via acquiring a lock
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FailManagerEmpty(Exception)
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raised by FailManager.toBan after reaching the list of tickets
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(RF-Note: asks to become a generator ;) )
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filter.py
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~~~~~~~~~~
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Filter(JailThread)
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Wraps (non-threaded) FailManager (and proxies to it quite a bit),
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and provides all primary logic for processing new lines, what IPs to
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ignore, etc
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.failManager [FailManager]
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.dateDetector [DateDetector]
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.__failRegex [list]
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.__ignoreRegex [list]
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Contains regular expressions for failures and ignores
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.__findTime [numeric]
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Used in `processLineAndAdd` to skip old lines
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FileFilter(Filter):
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Files-aware Filter
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.__logPath [list]
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keeps the tracked files (added 1-by-1 using addLogPath)
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stored as FileContainer's
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.getFailures
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actually just returns
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True
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if managed to open and get lines (until empty)
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False
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if failed to open or absent container matching the filename
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FileContainer
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Adapter for a file to deal with log rotation.
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.open,.close,.readline
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RF-Note: readline returns "" with handler absent... shouldn't it be None?
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.__pos
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Keeps the position pointer
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dnsutils.py
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~~~~~~~~~~~
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DNSUtils
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Utility class for DNS and IP handling
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filter*.py
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~~~~~~~~~~
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Implementations of FileFilter's for specific backends. Derived
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classes should provide an implementation of `run` and usually
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override `addLogPath`, `delLogPath` methods. In run() method they all
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one way or another provide
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try:
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while True:
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ticket = self.failManager.toBan()
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self.jail.putFailTicket(ticket)
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except FailManagerEmpty:
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self.failManager.cleanup(MyTime.time())
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thus channeling "ban tickets" from their failManager to the
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corresponding jail.
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action.py
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~~~~~~~~~
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Takes care about executing start/check/ban/unban/stop commands
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Releasing
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=========
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# Check distribution patches and see if they can be included
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* https://apps.fedoraproject.org/packages/fail2ban/sources
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* http://sources.gentoo.org/cgi-bin/viewvc.cgi/gentoo-x86/net-analyzer/fail2ban/
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* http://svnweb.freebsd.org/ports/head/security/py-fail2ban/
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* https://build.opensuse.org/package/show?package=fail2ban&project=openSUSE%3AFactory
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* http://sophie.zarb.org/sources/fail2ban (Mageia)
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* https://trac.macports.org/browser/trunk/dports/security/fail2ban
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# Check distribution outstanding bugs
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* https://github.com/fail2ban/fail2ban/issues?sort=updated&state=open
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* http://bugs.debian.org/cgi-bin/pkgreport.cgi?dist=unstable;package=fail2ban
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* http://bugs.sabayon.org/buglist.cgi?quicksearch=net-analyzer%2Ffail2ban
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* https://bugs.gentoo.org/buglist.cgi?query_format=advanced&short_desc=fail2ban&bug_status=UNCONFIRMED&bug_status=CONFIRMED&bug_status=IN_PROGRESS&short_desc_type=allwords
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* https://bugzilla.redhat.com/buglist.cgi?query_format=advanced&bug_status=NEW&bug_status=ASSIGNED&component=fail2ban&classification=Red%20Hat&classification=Fedora
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* http://www.freebsd.org/cgi/query-pr-summary.cgi?text=fail2ban
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# Provide a release sample to distributors
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* Debian: Yaroslav Halchenko <debian@onerussian.com>
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http://packages.qa.debian.org/f/fail2ban.html
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* FreeBSD: Christoph Theis theis@gmx.at>, Nick Hilliard <nick@foobar.org>
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http://svnweb.freebsd.org/ports/head/security/py-fail2ban/Makefile?view=markup
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* Fedora: Axel Thimm <Axel.Thimm@atrpms.net>
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https://apps.fedoraproject.org/packages/fail2ban
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* Gentoo: netmon@gentoo.org
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http://sources.gentoo.org/cgi-bin/viewvc.cgi/gentoo-x86/net-analyzer/fail2ban/metadata.xml?view=markup
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* openSUSE: Stephan Kulow <coolo@suse.com>
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https://build.opensuse.org/package/users?package=fail2ban&project=openSUSE%3AFactory
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* Mac Ports: @Malbrouck on github (gh-49)
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https://trac.macports.org/browser/trunk/dports/security/fail2ban/Portfile
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# Wait for feedback from distributors
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# Ensure the version is correct in ./common/version.py
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# Add/finalize the corresponding entry in the ChangeLog
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To generate a list of committers use e.g.
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git shortlog -sn 0.8.8.. | sed -e 's,^[ 0-9\t]*,,g' | tr '\n' '\|' | sed -e 's:|:, :g'
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Ensure the top of the ChangeLog has the right version and current date.
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Ensure the top entry of the ChangeLog has the right version and current date.
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# Update man pages
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(cd man ; ./generate-man )
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git commit -m 'update man pages for release' man/*
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# Make sure the tests pass
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./fail2ban-testcases-all
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# Prepare/upload source and rpm binary distributions
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python setup.py check
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python setup.py sdist
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python setup.py bdist_rpm
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python setup.py upload
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# Run the following and update the wiki with output:
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python -c 'import common.protocol; common.protocol.printWiki()'
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# Email users and development list of release
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# notify distributors
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Post Release
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============
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Add the following to the top of the ChangeLog
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ver. 0.8.12 (2013/XX/XXX) - wanna-be-released
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-----------
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- Fixes:
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- New Features:
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- Enhancements:
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and adjust common/version.py to carry .dev suffix to signal
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a version under development.
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