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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 sample log is provided in testcases/files/logs/ with same name as the |
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filter. Each log line should include match meta data for time & IP above |
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every line (see other sample log files for examples) |
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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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If merge resulted in conflicts, clarify what changes were done to |
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corresponding files in the 'Conflicts:' section of the merge commit |
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message. See e.g. https://github.com/fail2ban/fail2ban/commit/f5a8a8ac |
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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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