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Version: v1.2

Format

Parser configuration example#

A parser might look like:

onsuccess: next_stagedebug: truefilter: "evt.Parsed.program == 'kernel'"name: crowdsecurity/demo-iptablesdescription: "Parse iptables drop logs"pattern_syntax:  MYCAP: ".*"grok:  pattern: ^xxheader %{MYCAP:extracted_value} trailing stuff$  apply_on: evt.Parsed.some_fieldstatics:  - parsed: something    expression: JsonExtract(evt.Event.extracted_value, "nested.an_array[0]")  - meta: log_type    value: parsed_testlog  - meta: source_ip    expression: "evt.Parsed.src_ip"

The parser nodes are processed sequentially based on the alphabetical order of stages and subsequent files. If the node is considered successful (grok is present and returned data or no grok is present) and "onsuccess" equals to next_stage, then the event is moved to the next stage.

Parser trees#

A parser node can contain sub-nodes, to provide proper branching (on top of stages). It can be useful when you want to apply different parsing based on different criterias, or when you have a set of candidates parsers that you want to apply to an event :

#This first node will capture/extract some valuefilter: "evt.Line.Labels.type == 'type1'"name: tests/base-grok-rootpattern_syntax:  MYCAP: ".*"grok:  pattern: ^... %{MYCAP:extracted_value} ...$  apply_on: Line.Rawstatics:  - meta: state    value: root-done  - meta: state_sub    expression: evt.Parsed.extracted_value---#and this node will apply different patterns to itfilter: "evt.Line.Labels.type == 'type1' && evt.Meta.state == 'root-done'"name: tests/base-grok-leafsonsuccess: next_stage#the sub-nodes will process the result of the master nodenodes:  - filter: "evt.Parsed.extracted_value == 'VALUE1'"    debug: true    statics:      - meta: final_state        value: leaf1  - filter: "evt.Parsed.extracted_value == 'VALUE2'"    debug: true    statics:      - meta: final_state        value: leaf2

The tests/base-grok-root node will be processed first and will alter the event (here mostly by extracting some text from the Line.Raw field into Parsed thanks to the grok pattern and the statics directive).

The event will then be parsed by the the following tests/base-grok-leafs node. This node has onsuccess set to next_stage which means that if the node is successful, the event will be moved to the next stage.

A real-life example can be seen when it comes to parsing HTTP logs. HTTP ACCESS and ERROR logs often have different formats, and thus our "nginx" parser needs to handle both formats

Nginx parser
filter: "evt.Parsed.program == 'nginx'"onsuccess: next_stagename: crowdsecurity/nginx-logsnodes:  - grok:      #this is the access log      name: NGINXACCESS      apply_on: message      statics:        - meta: log_type          value: http_access-log        - target: evt.StrTime          expression: evt.Parsed.time_local  - grok:        # and this one the error log        name: NGINXERROR        apply_on: message        statics:          - meta: log_type            value: http_error-log          - target: evt.StrTime            expression: evt.Parsed.time# these ones apply for both grok patternsstatics:  - meta: service    value: http  - meta: source_ip    expression: "evt.Parsed.remote_addr"  - meta: http_status    expression: "evt.Parsed.status"  - meta: http_path    expression: "evt.Parsed.request"

Parser directives#

debug#

debug: true|false

default: false

If set to to true, enabled node level debugging. It is meant to help understanding parser node behavior by providing contextual logging :

assignments made by statics
DEBU[31-07-2020 16:36:28] + Processing 4 statics                        id=withered-rain name=crowdsecurity/nginx-logs stage=s01-parseDEBU[31-07-2020 16:36:28] .Meta[service] = 'http'                       id=withered-rain name=crowdsecurity/nginx-logs stage=s01-parseDEBU[31-07-2020 16:36:28] .Meta[source_ip] = '127.0.0.1'                id=withered-rain name=crowdsecurity/nginx-logs stage=s01-parseDEBU[31-07-2020 16:36:28] .Meta[http_status] = '200'                    id=withered-rain name=crowdsecurity/nginx-logs stage=s01-parseDEBU[31-07-2020 16:36:28] .Meta[http_path] = '/'                        id=withered-rain name=crowdsecurity/nginx-logs stage=s01-parse
assignments made by grok pattern
DEBU[31-07-2020 16:36:28] + Grok 'NGINXACCESS' returned 10 entries to merge in Parsed  id=dark-glitter name=child-crowdsecurity/nginx-logs stage=s01-parseDEBU[31-07-2020 16:36:28]   .Parsed['time_local'] = '21/Jul/2020:16:13:05 +0200'  id=dark-glitter name=child-crowdsecurity/nginx-logs stage=s01-parseDEBU[31-07-2020 16:36:28]   .Parsed['method'] = 'GET'                    id=dark-glitter name=child-crowdsecurity/nginx-logs stage=s01-parseDEBU[31-07-2020 16:36:28]   .Parsed['request'] = '/'                     id=dark-glitter name=child-crowdsecurity/nginx-logs stage=s01-parseDEBU[31-07-2020 16:36:28]   .Parsed['http_user_agent'] = 'curl/7.58.0'   id=dark-glitter name=child-crowdsecurity/nginx-logs stage=s01-parseDEBU[31-07-2020 16:36:28]   .Parsed['remote_addr'] = '127.0.0.1'         id=dark-glitter name=child-crowdsecurity/nginx-logs stage=s01-parse
debug of filters and expression results
DEBU[31-07-2020 16:36:28] eval(evt.Parsed.program == 'nginx') = TRUE    id=withered-rain name=crowdsecurity/nginx-logs stage=s01-parseDEBU[31-07-2020 16:36:28] eval variables:                               id=withered-rain name=crowdsecurity/nginx-logs stage=s01-parseDEBU[31-07-2020 16:36:28]        evt.Parsed.program = 'nginx'           id=withered-rain name=crowdsecurity/nginx-logs stage=s01-parse

filter#

filter: expression

filter must be a valid expr expression that will be evaluated against the event.

If filter evaluation returns true or is absent, node will be processed.

If filter returns false or a non-boolean, node won't be processed.

Here is the expr documentation.

Examples :

  • filter: "evt.Meta.foo == 'test'"
  • filter: "evt.Meta.bar == 'test' && evt.Meta.foo == 'test2'

grok#

pattern#

A valid grok pattern

expression#

A valid expr expression that return a string to apply the pattern on.

apply_on#

The field to apply the pattern on.

Examples#

grok:  name: NAMED_EXISTING_PATTERN  apply_on: source_field
grok:  pattern: ^a valid RE2 expression with %{CAPTURE:field}$  expression: JsonExtract(evt.Line.Raw, "field.example")
grok:  pattern: ^a valid RE2 expression with %{CAPTURE:field}$  apply_on: source_field

The grok structure in a node represent a regular expression with capture group (grok pattern) that must be applied on a field of event.

The pattern can :

  • be imported by name (if present within the core of CrowdSec)
  • defined in place

In both case, the pattern must be a valid RE2 expression. The field(s) returned by the regular expression are going to be merged into the Parsed associative array of the Event.

name#

name: explicit_string

The mandatory name of the node. If not present, node will be skipped at runtime. It is used for example in debug log to help you track things.

nodes#

nodes: - filter: ...   grok: ...

nodes is a list of parser nodes, allowing you to build trees. Each subnode must be valid, and if any of the subnodes succeed, the whole node is considered successful.

onsuccess#

onsuccess: next_stage|continue

default: continue

if set to next_stage and the node is considered successful, the event will be moved directly to the next stage without processing other nodes in the current stage.

info

if it's a parser tree, and a "leaf" node succeeds, it is the parent's "onsuccess" that is evaluated.

pattern_syntax#

pattern_syntax:  CAPTURE_NAME: VALID_RE2_EXPRESSION

pattern_syntax allows user to define named capture group expressions for future use in grok patterns. Regexp must be a valid RE2 expression.

pattern_syntax:  MYCAP: ".*"grok:  pattern: ^xxheader %{MYCAP:extracted_value} trailing stuff$  apply_on: Line.Raw

statics#

statics is a list of directives that will be evaluated when the node is considered successful. Each entry of the list is composed of a target (where to write) and a source (what data to write).

target#

The target can be defined by pointing directly a key in a dictionary (Parsed, Enriched or Meta), or by providing direct a target expression :

meta: target_field

meta: source_ip will set the value in evt.Meta.source_ip

parsed: target_field

parsed: remote_addr will set the value in evt.Parsed.remote_addr

enriched: target_field

enriched: extra_info will set the value in evt.Enriched.extra_info

target: evt.Parsed.foobar

target: evt.Meta.foobar will set the value in the Meta[foobar] entry

source#

value: <string_value_to_assign>

A static value.

expression: <expr>

A valid expr expression to eval. The result of the evaluation will be set in the target field.

Example#

statics: - target: evt.Meta.target_field   value: static_value - meta: target_field   expression: evt.Meta.target_field + ' this_is' + ' a dynamic expression' - enriched: target_field   value: static_value
statics:  - meta: target_field    value: static_value  - meta: target_field    expression: evt.Meta.another_field  - meta: target_field    expression: evt.Meta.target_field + ' this_is' + ' a dynamic expression'

data#

data:  - source_url: https://URL/TO/FILE    dest_file: LOCAL_FILENAME    type: (regexp|string)

data allows user to specify an external source of data. This section is only relevant when cscli is used to install parser from hub, as it will download the source_url and store it to dest_file. When the parser is not installed from the hub, CrowdSec won't download the URL, but the file must exist for the parser to be loaded correctly.

The type is mandatory if you want to evaluate the data in the file, and should be regex for valid (re2) regular expression per line or string for string per line. The regexps will be compiled, the strings will be loaded into a list and both will be kept in memory. Without specifying a type, the file will be downloaded and stored as file and not in memory.

name: crowdsecurity/cdn-whitelist...data:  - source_url: https://www.cloudflare.com/ips-v4    dest_file: cloudflare_ips.txt    type: string

Notes#

A parser is considered "successful" if :

  • A grok pattern was present and successfully matched
  • No grok pattern was present

Patterns documentation#

You can find exhaustive patterns documentation here.