Capture tokens and secret id from Hashicorp Vault and assign it to Windows Env Variables: Combining regex and Select-String cmdlet

Pavol Kutaj

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Oct 29, 2020

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usecase

• The concern is documenting capturing the token from hashicorp vault and passing it to the Windows Environment Variables
• that I need to re-issue every 12 hours in order to work with the stack.
• The aim is to get both consul and nomad CLI to work properly and to use the same keys for the WEBUI

▶ vault read consul/creds/support
Key                Value
---                -----
lease_id           consul/creds/support/1111111111
lease_duration     12h
lease_renewable    true
accessor           1111-1111-1111-1111-1111
local              false
token              1111-1111-1111-1111-1111 <--- NEED TO ASSIGN THIS TO THE ENV VAR FOR CLI TO WORK

• nomad output:

▶ vault read nomad/creds/nomad-viewer
Key                Value
---                -----
lease_id           nomad/creds/nomad-viewer/1111-1111-1111-1111-1111
lease_duration     12h
lease_renewable    true
accessor_id        1111-1111-1111-1111-1111
secret_id          1111-1111-1111-1111-1111

1. cmdlet: Select-String

• I can use Select-String aka sls to grab the line

vault read consul/creds/support | sls token -Pattern token.*token              1111-1111-1111-1111-1111

2. regex: lookaheads and lookbehinds

• concepts to define patterns that only match they they
• are / are not followed by a certain pattern → lookahead (positive / negative)
• are / are not preceded by a certain pattern → lookbehind (positive / negative)

2.1. testing lookbehind with regex

• if I want to capture a name that is after mr + an empty string (whitespace \s)
• I need to use lookbehind syntax

[regex]::matches(‘mr paul’,’(?<=mr\s).*’).value
→→→ paul

4. final regex with vault

vault read consul/creds/support |  #01
sls -pattern ’(?<=token\s+)\S+’ |  #02-05
% {$keys = $_.Matches.Value}       #07

5. assign the binding to the env var

$env:CONSUL_HTTP_TOKEN=$keys

6. CODE

function get-vaultKeys {
    $consulRegex = "(?<=token\s+)\S+"
    $nomadRegex = "(?<=secret_id\s+)\S+"
    $consulURL = "https://consul.foo.net/ui"
    $nomadURL = "https://nomad.foo.net/ui"    vault read consul/creds/support |
    sls -pattern $consulRegex |  
    % {$consulKey = $_.Matches.Value}           vault read nomad/creds/nomad-viewer |
    sls -pattern $nomadRegex |  
    % {$nomadKey = $_.Matches.Value}           $env:CONSUL_HTTP_TOKEN=$consulKey
    $env:NOMAD_TOKEN=$nomadKey
    
    write-host "~~~~~~" -ForegroundColor Cyan
    write-host "Consul: $consulKey" -ForegroundColor Cyan
    write-host "Nomad: $nomadKey" -ForegroundColor Cyan
    write-host "~~~~~~" -ForegroundColor Cyan    start chrome $consulURL
    start chrome $nomadURL
}

7. sources

• PowerShell regex crash course — Part 4 of 5 | Scripting Blog