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PIMO : Private Input, Masked Output

PIMO is a tool for data masking. It can mask data from a JSONline stream and return another JSONline stream thanks to a masking configuration contained in a yaml file.

Configuration file needed

PIMO requires a yaml configuration file to works. By default, the file is named masking.yml and is placed in the working directory. The file must respect the following format :

version: "1"
seed: 42
masking:
  - selector:
      jsonpath: "example.example"
    mask:
      type: "argument"
    # Optional cache (coherence preservation)
    cache: "cacheName"

  # another mask on a different location
  - selector:
      jsonpath: "example.example2"
    mask:
      type: "argument"
    preserve: "null"

caches:
  cacheName:
    # Optional bijective cache (enable re-identification if the cache is dumped on disk)
    unique: true

version is the version of the masking file. seed is to give every random mask the same seed, it is optional and if it is not defined, the seed is derived from the current time to increase randomness. masking is used to define the pipeline of masks that is going to be applied. selector is made of a jsonpath and a mask. jsonpath defines the path of the entry that has to be masked in the json file. mask defines the mask that will be used for the entry defined by selector. cache is optional, if the current entry is already in the cache as key the associated value is returned without executing the mask. Otherwise the mask is executed and a new entry is added in the cache with the orignal content as key and the masked result as value. The cache have to be declared in the caches section of the YAML file. preserve is optional, and is used to keep some values unmasked in the json file. Allowed preserve options are: "null" (null values), "empty" (empty string ""), and "blank" (both empty and null values).

Multiple masks can be applied on the same jsonpath location, like in this example :

  - selector:
      jsonpath: "example"
    masks:
      - add: "hello"
      - template: "{{.example}} World!"
      - remove: true

Masks can be applied on multiple selectors, like in this example:

  - selectors:
      - jsonpath: "example"
      - jsonpath: "example2"
    mask:
      add: "hello"

Possible masks

The following types of masks can be used :

  • Pure randomization masks
    • regex is to mask using a regular expression given in argument.
    • randomInt is to mask with a random int from a range with arguments min and max.
    • randomDecimal is to mask with a random decimal from a range with arguments min, max and precision.
    • randDate is to mask a date with a random date between dateMin and dateMax.
    • randomDuration is to mask a date by adding or removing a random time between Min and Max.
    • randomChoice is to mask with a random value from a list in argument.
    • weightedChoice is to mask with a random value from a list with probability, both given with the arguments choice and weight.
    • randomChoiceInUri is to mask with a random value from an external resource.
  • K-Anonymization
    • range is to mask a integer value by a range of value (e.g. replace 5 by [0,10]).
    • duration is to mask a date by adding or removing a certain number of days.
  • Re-identification and coherence preservation
    • hash is to mask with a value from a list by matching the original value, allowing to mask a value the same way every time.
    • hashInUri is to mask with a value from an external resource, by matching the original value, allowing to mask a value the same way every time.
    • fromCache is a mask to obtain a value from a cache.
    • ff1 mask allows the use of FPE which enable private-key based re-identification.
  • Formatting
    • dateParser is to change a date format.
    • template is to mask a data with a template using other values from the jsonline.
    • template-each is like template but will apply on each value of an array.
  • Data structure manipulation
    • remove is to mask a field by completely removing it.
    • add is a mask to add a field to the jsonline.
    • add-transient same as add but the field is not exported in the output jsonline.
  • Others
    • constant is to mask the value by a constant value given in argument.
    • command is to mask with the output of a console command given in argument.
    • incremental is to mask data with incremental value starting from start with a step of increment.
    • fluxUri is to replace by a sequence of values defined in an external resource.
    • replacement is to mask a data with another data from the jsonline.
    • pipe is a mask to handle complex nested array structures, it can read an array as an object stream and process it with a sub-pipeline.
    • luhn can generate valid numbers using the Luhn algorithm (e.g. french SIRET or SIREN).

A full masking.yml file example, using every kind of mask, is given with the source code.

In case two types of mask are entered with the same selector, the program can't extract the masking configuration and will return an error. The file wrongMasking.yml provided with the source illustrate that error.

Usage

To use PIMO to mask a data.json, use in the following way :

./pimo <data.json >maskedData.json

This takes the data.json file, masks the data contained inside it and put the result in a maskedData.json file. If data are in a table (for example multiple names), then each field of this table will be masked using the given mask. The following flags can be used:

  • --repeat=N This flag will make pimo mask every input N-times (useful for dataset generation).
  • --skip-line-on-error This flag will totally skip a line if an error occurs masking a field.
  • --skip-field-on-error This flag will return output without a field if an error occurs masking this field.
  • --empty-input This flag will give PIMO a {} input, usable with --repeat flag.
  • --config=filename.yml This flag allow to use another file for config than the default masking.yml.
  • --load-cache cacheName=filename.json This flag load an initial cache content from a file (json line format {"key":"a", "value":"b"}).
  • --dump-cache cacheName=filename.json This flag dump final cache content to a file (json line format {"key":"a", "value":"b"}).
  • --verbosity <level> or -v<level> This flag increase verbosity on the stderr output, possible values: none (0), error (1), warn (2), info (3), debug (4), trace (5).
  • --debug This flag complete the logs with debug information (source file, line number).
  • --log-json Set this flag to produce JSON formatted logs (demo9 goes deeper into logging and structured logging)
  • --mask Declare a simple masking definition in command line (minified YAML format: --mask "value={fluxUri: 'pimo://nameFR'}", or --mask "value=[{add: ''},{fluxUri: 'pimo://nameFR'}]" for multiple masks). For advanced use case (e.g. if caches needed) masking.yml file definition will be preferred.
  • --repeat-until <condition> This flag will make PIMO keep masking every input until the condition is met. Condition format is using Template. Last output verifies the condition.
  • --repeat-while <condition> This flag will make PIMO keep masking every input while the condition is met. Condition format is using Template.

Examples

This section will give examples for every types of mask.

Please check the demo folder for more advanced examples.

Regex

  - selector:
      jsonpath: "phone"
    mask:
      regex: "0[1-7]( ([0-9]){2}){4}"

This example will mask the phone field of the input jsonlines with a random string respecting the regular expression.

Return to list of masks

Constant

  - selector:
      jsonpath: "name"
    mask:
      constant: "Bill"

This example will mask the name field of the input jsonlines with the value of the constant field.

Return to list of masks

RandomChoice

  - selector:
      jsonpath: "name"
    mask:
      randomChoice:
       - "Mickael"
       - "Mathieu"
       - "Marcelle"

This example will mask the name field of the input jsonlines with random values from the randomChoice list.

Return to list of masks

RandomChoiceInUri

  - selector:
      jsonpath: "name"
    mask:
      randomChoiceInUri: "file://names.txt"

This example will mask the name field of the input jsonlines with random values from the list contained in the name.txt file. The different URI usable with this selector are : pimo, file and http/https.

A value can be injected in URI with the template syntax. For example, file://name{{.gender}}.txt select a line in name_F.txt if the current jsonline is {gender : "F"}.

Return to list of masks

RandomInt

  - selector:
      jsonpath: "age"
    mask:
      randomInt:
        min: 25
        max: 32

This example will mask the age field of the input jsonlines with a random number between min and max included.

Return to list of masks

RandomDecimal

  - selector:
      jsonpath: "score"
    mask:
      randomDecimal:
        min: 0
        max: 17.23
        precision: 2

This example will mask the score field of the input jsonlines with a random float between min and max, with the number of decimal chosen in the precision field.

Return to list of masks

Command

  - selector:
      jsonpath: "name"
    mask:
      command: "echo -n Dorothy"

This example will mask the name field of the input jsonlines with the output of the given command. In this case, Dorothy.

Return to list of masks

WeightedChoice

  - selector:
      jsonpath: "surname"
    mask:
      weightedChoice:
        - choice: "Dupont"
          weight: 9
        - choice: "Dupond"
          weight: 1

This example will mask the surname field of the input jsonlines with a random value in the weightedChoice list with a probability proportional at the weight field.

Return to list of masks

Hash

  - selector:
      jsonpath: "town"
    mask:
      hash:
        - "Emerald City"
        - "Ruby City"
        - "Sapphire City"

This example will mask the town field of the input jsonlines with a value from the hash list. The value will be chosen thanks to a hashing of the original value, allowing the output to be always the same in case of identical inputs.

Return to list of masks

HashInUri

  - selector:
      jsonpath: "name"
    mask:
      hashInUri: "pimo://nameFR"

This example will mask the name field of the input jsonlines with a value from the list nameFR contained in pimo, the same way as for hash mask. The different URI usable with this selector are : pimo, file and http/https.

Return to list of masks

RandDate

  - selector:
      jsonpath: "date"
    mask:
      randDate:
        dateMin: "1970-01-01T00:00:00Z"
        dateMax: "2020-01-01T00:00:00Z"

This example will mask the date field of the input jsonlines with a random date between dateMin and dateMax. In this case the date will be between the 1st January 1970 and the 1st January 2020.

Return to list of masks

Duration

  - selector:
      jsonpath: "last_contact"
    mask:
      duration: "-P2D"

This example will mask the last_contact field of the input jsonlines by decreasing its value by 2 days. The duration field should match the ISO 8601 standard for durations.

Return to list of masks

DateParser

  - selector:
      jsonpath: "date"
    mask:
      dateParser:
        inputFormat: "2006-01-02"
        outputFormat: "01/02/06"

This example will change every date from the date field from the inputFormat to the outputFormat. The format should always display the following date : Mon Jan 2 15:04:05 -0700 MST 2006. Either field is optional and in case a field is not defined, the default format is RFC3339, which is the base format for PIMO, needed for duration mask and given by randDate mask.

Return to list of masks

RandomDuration

  - selector:
      jsonpath: "date"
    mask:
      randomDuration:
        min: "-P2D"
        max: "-P27D"

This example will mask the date field of the input jsonlines by decreasing its value by a random value between 2 and 27 days. The durations should match the ISO 8601 standard.

Return to list of masks

Incremental

  - selector:
      jsonpath: "id"
    mask:
      incremental:
        start: 1
        increment: 1

This example will mask the id field of the input jsonlines with incremental values. The first jsonline's id will be masked by 1, the second's by 2, etc...

Return to list of masks

Replacement

  - selector:
      jsonpath: "name4"
    mask:
      replacement: "name"

This example will mask the name4 field of the input jsonlines with the field name of the jsonline. This selector must be placed after the name selector to be masked with the new value and it must be placed before the name selector to be masked by the previous value.

Return to list of masks

Template

  - selector:
      jsonpath: "mail"
    mask:
      template: "{{.surname}}.{{.name}}@gmail.com"

This example will mask the mail field of the input jsonlines respecting the given template. In the masking.yml config file, this selector must be placed after the fields contained in the template to mask with the new values and before the other fields to be masked with the old values. In the case of a nested json, the template must respect the following example :

  - selector:
      jsonpath: "user.mail"
    mask:
      template: "{{.user.surname}}.{{.user.name}}@gmail.com"

The format for the template should respect the text/template package : https://golang.org/pkg/text/template/

The template mask can format the fields used. The following example will create a mail address without accent or upper case:

  - selector:
      jsonpath: "user.mail"
    mask:
      template: "{{.surname | NoAccent | upper}}.{{.name | NoAccent | lower}}@gmail.com"

Available functions for templates come from http://masterminds.github.io/sprig/.

Return to list of masks

Template each

  - selector:
      jsonpath: "array"
    mask:
      template-each:
        template: "{{title .value}}"
        item: "value"

This will affect every values in the array field. The field must be an array ({"array": ["value1", "value2]). The item property is optional and defines the name of the current item in the templating string (defaults to "it"). There is another optional property index, if defined then a property with the given name will be available in the templating string (e.g. : index: "idx" can be used in template with {{.idx}}).

The format for the template should respect the text/template package : https://golang.org/pkg/text/template/

See also the Template mask for other options, all functions are applicable on template-each.

Return to list of masks

Remove

  - selector:
      jsonpath: "useless-field"
    mask:
      remove: true

This field will mask the useless-field of the input jsonlines by completely deleting it.

Return to list of masks

Add

  - selector:
      jsonpath: "newField"
    mask:
      add: "newvalue"

This example will create the field newField containing the value newvalue. This value can be a string, a number, a boolean...

The field will be created in every input jsonline that doesn't already contains this field.

Return to list of masks

Add-Transient

  - selector:
      jsonpath: "newField"
    mask:
      add-transient: "newvalue"

This example will create the field newField containing the value newvalue. This value can be a string, a number, a boolean... It can also be a template.

The field will be created in every input jsonline that doesn't already contains this field, and it will be removed from the final JSONLine output.

This mask is used for temporary field that is only available to other fields during the execution.

Return to list of masks

FluxURI

  - selector:
      jsonpath: "id"
    mask:
      fluxURI: "file://id.csv"

This example will create an id field in every output jsonline. The values will be the ones contained in the id.csv file in the same order as in the file. If the field already exist on the input jsonline it will be replaced and if every value of the file has already been assigned, the input jsonlines won't be modified.

Return to list of masks

FromCache

  - selector:
      jsonpath: "id"
    mask:
      fromCache: "fakeId"
  caches:
    fakeId :
      unique: true

This example will replace the content of id field by the matching content in the cache fakeId. Cache have to be declared in the caches section. Cache content can be loaded from jsonfile with the --load-cache fakeId=fakeId.jsonl option or by the cache option on another field. If no matching is found in the cache, fromCache block the current line and the next lines are processing until a matching content go into the cache.

Return to list of masks

FF1

  - selector:
      jsonpath: "siret"
    mask:
      ff1:
        radix: 10
        keyFromEnv: "FF1_ENCRYPTION_KEY"

This example will encrypt the siret column with the private key base64-encoded in the FF1_ENCRYPTION_KEY environment variable. Use the same mask with the option decrypt: true to re-identify the unmasked value.

Be sure to check the full FPE demo to get more details about this mask.

Return to list of masks

Range

  - selector:
      jsonpath: "age"
    mask:
      range: 5

This mask will replace an integer value {"age": 27} with a range like this {"age": "[25;29]"}.

Return to list of masks

Pipe

If the data structure contains arrays of object like in the example below, this mask can pipe the objects into a sub pipeline definition.

data.jsonl

{
    "organizations": [
        {
            "domain": "company.com",
            "persons": [
                {
                    "name": "leona",
                    "surname": "miller",
                    "email": ""
                },
                {
                    "name": "joe",
                    "surname": "davis",
                    "email": ""
                }
            ]
        },
        {
            "domain": "company.fr",
            "persons": [
                {
                    "name": "alain",
                    "surname": "mercier",
                    "email": ""
                },
                {
                    "name": "florian",
                    "surname": "legrand",
                    "email": ""
                }
            ]
        }
    ]
}

masking.yml

version: "1"
seed: 42
masking:
  - selector:
      # this path points to an array of persons
      jsonpath: "organizations.persons"
    mask:
      # it will be piped to the masking pipeline definition below
      pipe:
        # the parent object (a domain) will be accessible with the "_" variable name
        injectParent: "_"
        masking:
          - selector:
              jsonpath: "name"
            mask:
              # fields inside the person object can be accessed directly
              template: "{{ title .name }}"
          - selector:
              jsonpath: "surname"
            mask:
              template: "{{ title .surname }}"
          - selector:
              jsonpath: "email"
            mask:
              # the value stored inside the parent object is accessible through "_" thanks to the parent injection
              template: "{{ lower .name }}.{{ lower .surname }}@{{ ._.domain }}"

In addition to the injectParent property, this mask also provide the injectRoot property to inject the whole structure of data.

It is possible to simplify the masking.yml file by referencing an external yaml definition :

version: "1"
seed: 42
masking:
  - selector:
      jsonpath: "organizations.persons"
    mask:
      pipe:
        injectParent: "domain"
        file: "./masking-person.yml"

Be sure to check demo to get more details about this mask.

Return to list of masks

Luhn

The Luhn algorithm is a simple checksum formula used to validate a variety of identification numbers.

The luhn mask can calculate the checksum for any value.

  - selector:
      jsonpath: "siret"
    mask:
      luhn: {}

In this example, the siret value will be appended with the correct checksum, to create a valid SIRET number (french business identifier).

The mask can be parametered to use a different universe of valid characters, internally using the Luhn mod N algorithm.

  - selector:
      jsonpath: "siret"
    mask:
      luhn:
        universe: "abcde"

Return to list of masks

Visual Studio Code

To integrate with Visual Studio Code (opens new window), download the YAML extension.

Then, edit your Visual Studio Code settings yaml.schemas to containing the following configuration:

{
  "yaml.schemas": {
    "https://raw.codeproxy.net/CGI-FR/PIMO/main/schema/v1/pimo.schema.json": "/**/*masking*.yml"
  }
}

Using this configuration, the schema will be applied on every YAML file containing the word `masking`` in their name.

Contributors

Licence

Copyright (C) 2021 CGI France

PIMO is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

PIMO is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with PIMO. If not, see http://www.gnu.org/licenses/.

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