SQL Data Catalog, Data Masker and your DevOps pipeline: How do I make sure everything is being masked?

“However fast regulation moves, technology moves faster. Especially as far as data is concerned.”
Elizabeth Denham

You’re probably sick of me constantly talking about how the cataloging of columns should be part of the DevOps upstream deployment process. I’ve blogged about it. I’ve even produced a video demonstrating this in action. But one question that this always throws up is:

If we include cataloging in the upstream process, how do we make sure our masking sets are also staying up to date?

The benefits of including the classifications in the upstream pipeline is that nothing ever gets to Production that hasn’t been classified – we constantly have a perfectly up to date idea of the nature of our structured data estate, how data is distributed, what risk is associated with which systems? etc. but one of the biggest wins is that we constantly know which fields need to be masked when we’re pulling copies back into non-Production, constantly.

Add a table? Add columns? We know about them, they’re classified, they’re deployed… so now they need to be masked on our next refresh. But how? Well it all depends on which approach we want to take:

  • Automated
  • Manual

Doesn’t it always boil down to those options? What I mean is that either we have an appetite to completely generate our masking set afresh every single time based on our classifications (Automated) or do we want to ensure that we configure each rule ourselves (Manual). They both have benefits and drawbacks.


How: We can generate a masking set using the SQL Data Catalog PowerShell each and every time as part of our pipeline. Add a column, tag it in the pipeline and then simply wait for the necessary rulesets to be generated in the pipeline (perhaps as part of your build) for you to run when you bring a copy back. Check out my walkthrough for how to set this up.

Benefits: The process is automatic. Its headless and you don’t need to think about it at all. As long as the classifications are provided (and if you follow the steps from the blog post and video you should be providing them) then you’re always generating rules for every classified column.

Drawbacks: This process can be fragile. If we don’t classify correctly we can end up masking in the wrong way or trying to mask the wrong field (e.g. a Primary Key, Constraint, Identity etc.) which can cause masking failures and then you have to spend time fixing the pipeline/masking set. This also means that the nature of the masking is dependent on your classifications, and the values you will get masked into the columns will be less realistic as a result (i.e. you can’t generate Row-Internal Sync Rules using the integration).

Drawback Mitigation: To avoid the process breaking, be sure to really focus on how you set up your API settings / how you pick which categories and tags are used to generate the masking rules (like I discussed here). This will at least help you make sure you map common data sets into columns (and don’t hit columns that have constraints or keys).

Only columns marked with Static Masking as the Treatment Intent will get a rule created for them
An Information Type is given to every column we intend on masking – these are then mapped to templates in masker to ensure more realistic data


How: Either rely on developers to check in masking set changes along side their code changes or build in a manual intervention step to your upstream process to ensure that someone opens and updates the schema and rules within the masking set, and then put this back into the pipeline.

Benefits: This results in more accurate, more likely to run sets that generate significantly more reliable and realistic data as an end result. Masked DB copies can be more easily used for anything beyond simple development changes, including analytics etc. You can include any specialist rules you need and apply your own understanding and knowledge of the database.

Drawbacks: This is obviously a manual process – less than ideal. Anything that involves a human can invariably go wrong because we are humans and we make mistakes (which we learn from of course). This also takes significantly more time as part of the process.

Drawback Mitigation: This is a harder one to mitigate as we’re reliant on manual intervention, however the best way to check this could be with another team member checking (maybe as part of a pull request) or you could include an automated PowerShell script to effectively rationalize the columns to be masked from Catalog vs the columns currently in the Data Masker masking set – this would help you understand if all the necessary columns have been updated or if any were missed. I have included an example of this PowerShell below.


$MaskingSet = "yourmaskingset.DMSMaskSet" # Your masking set including the DMSMaskSet file extension
$instance = "yourinstance" # The Instance as it is shown in Data Catalog that hosts the database
$DatabaseName = "yourdatabase" # The DB you want classification info for
$CatalogServer="http://yourmachine:15156" # The lcoation of your catalog server, ending on :15156
$authToken="redacted" # Your Data Catalog Auth token from the Settings page
$tagName = "Static Masking" # The tag you're using to identify which columns need to be masked


Invoke-WebRequest -Uri "$CatalogServer/powershell" -OutFile 'data-catalog.psm1' -Headers @{"Authorization"="Bearer $authToken"}
Import-Module .\data-catalog.psm1 -Force
Connect-SqlDataCatalog -ServerUrl $CatalogServer -AuthToken $authToken 
$ColumnsMarkedForMasking = Get-ClassificationColumn `
    -InstanceName $instance `
    -DatabaseName $DatabaseName | Where-Object {$_.tags.name -eq $tagName} 
$MaskingSetXML = [xml](Get-Content -Path $MaskingSet)
$subrules = $MaskingSetXML.SelectNodes('//DMSSetContainer_MaskingSet/DMSSetContainer/DMSRuleBindingList/RuleSubstitution')
$internalrules = $MaskingSetXML.SelectNodes('//DMSSetContainer_MaskingSet/DMSSetContainer/DMSRuleBindingList/RuleRowInternal')
$shufflerules = $MaskingSetXML.SelectNodes('//DMSSetContainer_MaskingSet/DMSSetContainer/DMSRuleBindingList/RuleShuffle')
$searchreplacerules = $MaskingSetXML.SelectNodes('//DMSSetContainer_MaskingSet/DMSSetContainer/DMSRuleBindingList/RuleSearchReplace')
$TablesAndColumns = @()

$subrules | ForEach-Object {`
    $CurrentTable = $_.TargetTableName.value
    $_.DMSPickedColumnAndDataSetCollection.DMSPickedColumnAndDataSet.N2KSQLServerEntity_PickedColumn.ColumnName.value | ForEach-Object {$TablesAndColumns+= $CurrentTable + "." + $_ }

$internalrules | ForEach-Object {`
    $TablesAndColumns+= $_.TargetTableName.value + "." + $_.TargetColumnName.value

$shufflerules | ForEach-Object {`
    $CurrentTable = $_.TargetTableName.value
    $_.DMSPickedColumnCollection.DMSPickedColumn.N2KSQLServerEntity_PickedColumn.ColumnName.value | ForEach-Object {$TablesAndColumns+= $CurrentTable + "." + $_ }

$searchreplacerules | ForEach-Object {`
    $TablesAndColumns+= $_.TargetTableName.value + "." + $_.TargetColumnName.value

$result = $TablesAndColumns | Sort -Unique
$ColumnsNeedingRules = $ColumnsMarkedForMasking | Where-Object {($_.tableName + "." + $_.columnName) -notin $result}

"`nThere are " + $ColumnsMarkedForMasking.count + " columns that require masking for database " + $DatabaseName + "in SQL Data Catalog."
"You are masking " + $result.count + " distinct columns in masking set: " + $MaskingSet
"`nThe columns that do not currently have a mask configured are:`n"

$ColumnsNeedingRules | ForEach-Object {$_.tableName + "." + $_.columnName + "     (" + $_.dataType + ")"}

$next = Read-Host -Prompt "`nWould you like to see the columns currently in your masking set? (Y/N)"
if ($next -in ("Y", "y")) {$result}

This code can also be found on my GitHub here.

The output of running the script – 13 columns in the masking set, 14 columns outstanding to be masked

You can technically even use this same check approach for the automated masking set generation option, to ensure that everything has been tagged correctly.