Add name and description fields to all rules. The name field is actually
a field called 'rule', which corresponds to the 'macro' field for
macros.
Within the rule loader, the state changes slightly. There are two
indices into the set of rules 'rules_by_name' and
'rules_by_idx' (formerly 'outputs'). They both now contain the original
table from the yaml parse. One field 'level' is added which is the
priority mapped to a number.
Get rid of the notion of default priority or output. Every rule must now
provide both.
Go through all current rules and add names and descriptions.
Remove the old use of the '-o' command line option, it wasn't being
used.
Allow any config file option to be overridden on the command line, via
--option/-o. These options are applied to the configuration object after
reading the file, ensuring the command line options override anything in
the config file.
To support this, add some methods to yaml_configuration that allows you
to set the value for a top level key or key + subkey, and methods to
falco_configuration that allow providing a set of command line arguments
alongside the config file.
Ensure that any fatal error is always printed to stderr even if stderr
logging is not enabled. This makes sure that falco won't silently exit
on an error. This is especially important when daemonizing and when an
initial fatal error occurs first.
As a part of this, change all fatal errors to throw exceptions instead,
so all fatal errors get routed through the exception handler.
Improve daemonization by reopening stdin/stdout/stderr to /dev/null so
you don't have to worry about writing to a closed stderr on exit.
Henri pointed out that events may also be flagged as ignored. So
populate a second table with the set of ignored events, rename
check_for_ignored_syscalls to check_for_ignored_syscalls_events, and
separately check each table based on whether the LHS of the expression
is evt.type or syscall.type.
Add support for daemonizing via the --daemon flag. If daemonized, the
pid is written to the file provided via the --pidfile flag. When
daemonized, falco immediately returns an error if stderr output or
logging was chosen on the command line.
Clean up handling of outputs to match the expected use case (daemon):
- syslog output is enabled by default
- stdout output is disabled by default
- If not configured at all, both outputs are enabled.
Also fix some bugs I found while running via packages:
- There were still some references to the old rules filename
falco_rules.conf.
- The redhat package mistakenly defined some system directories like
/etc, /etc/init.d. Add them to the exclusion list (See
https://cmake.org/Bug/view.php?id=13609 for context).
- Clean up some of the error messages to be more consistent.
After this I was able to build and install debian and rpm
packages. Starting the falco service ran falco as a daemon with syslog
output.
Create a table containing the filtered syscalls and set it as the lua
global m_lua_ignored_syscalls == ignored_syscalls.
In the parser, add a general purpose ast traversal function
traverse_ast that calls a callback for all nodes of a specific type.
In the compiler, add a new function check_for_ignored_syscalls that uses
the traversal function to be called back for all "BinaryRelOp"
nodes (i.e. X = Y, X in [a, b, c], etc). For those nodes, if the lhs is
a field 'evt.type' or 'syscall.type' and the rhs contains one of the
ignored syscalls, throw an error.
Call check_for_ignored_syscalls after parsing any macro or rule
filter. The thrown error will contain the macro or rule that had the
ignored syscall.
In the next commit I'll change the rules to skip the ignored syscalls.
Uses yaml parsing lib to parse a yaml file comprising of a list of
macros and rules, like:
- macro: bin_dir
condition: fd.directory in (/bin, /sbin, /usr/bin, /usr/sbin)
- macro: core_binaries
condition: proc.name in (ls, mkdir, cat, less, ps)
- condition: (fd.typechar = 4 or fd.typechar=6) and core_binaries
output: "%evt.time: %proc.name network with %fd.l4proto"
- condition: evt.type = write and bin_dir
output: "%evt.time: System binary modified (file '%fd.filename' written by process %proc.name)"
- condition: container.id != host and proc.name = bash
output: "%evt.time: Shell running in container (%proc.name, %container.id)"
