Publish message to service bus using PowerShell

Overview

The Azure Portal include a service bus explorer tool. This can be used to publish a message to a queue or a topic. However, this is a little limited. While testing I found it frustrating that I needed to paste in the message body each time, along with a couple of custom properties.

Azure REST API

When automating Azure, my first port of call is Azure CLI. However, it seems this does not yet support publishing of messages to service bus. So, I turned to the Azure REST API.

Two Steps

There are two steps required:

1. obtain the auth header for the rest post
2. post the request

I have separated these into individual PowerShell scripts, which can be found at this github repo. The entry point is “post-msg.ps1”. You can see that this requires a sas token to be set. This can be found by navigating the Azure Portal to Service Bus Namespace/Shared access policies/RootManageSharedAccessKey (or create a new one)/Primary Key

The top-level script calls the “generate-sas-token.ps1” script in order to generate the sas token that is used in the header of the post request to the azure api.

post-msg.ps1

# This is the entry point. It will call the generate-sas-token.ps1 script to generate a SAS token and then use it to send a message to an Azure Service Bus topic.

# Define your connection string, topic name and SAS token
$endpoint = "https://biztalkers.servicebus.windows.net/"
$topicName = "p4f"
$sasToken = & '.\generate-sas-token.ps1'
$authHeader = "SharedAccessSignature $sasToken"

# Read JSON content from the file
$jsonFilePath = "./msg.json"
$jsonContent = Get-Content $jsonFilePath -Raw | ConvertFrom-Json

# Replace eventid and correlationid with new GUIDs
$jsonContent.eventid = [guid]::NewGuid().ToString()
$jsonContent.correlationid = [guid]::NewGuid().ToString()

# Convert the updated object back to JSON
$jsonContent = $jsonContent | ConvertTo-Json -Depth 100

# Output the JSON content
$jsonContent

# Prepare the custom properties
$properties = @{
    "eventtype" = "CommsEnrichmentCommand"
    "sourcesystem" = "Workflow"
}

# Convert properties to JSON
$propertiesJson = $properties | ConvertTo-Json -Compress

# Prepare the headers
$headers = @{
    "Authorization" = $authHeader
    "Content-Type" = "application/json"
    "BrokerProperties" = $propertiesJson
}

# Send the message using Invoke-RestMethod and store the response
$response = Invoke-RestMethod -Uri "$endpoint$topicName/messages" -Method Post -Body $jsonContent -Headers $headers

# Output the response
$response

generate-sas-token.ps1

# Note: this script is called by post-msg.ps1
[CmdletBinding()]
param (
    [Parameter()]
    $Namespace = "biztalkers",
    [Parameter()]
    $EntityPath = "p4f",
    [Parameter()]
    $SasKeyName = "RootManageSharedAccessKey",
    [Parameter()]
    $SasKey = "get-sas-key-from-azure-portal"

)

# Define the token's time-to-live in seconds
$ttl = New-TimeSpan -Days 30

# Get the target URI
$targetUri = [System.Web.HttpUtility]::UrlEncode("https://$Namespace.servicebus.windows.net/$EntityPath")

# Get the expiry time
$expiry = [DateTimeOffset]::Now.ToUnixTimeSeconds() + $ttl.TotalSeconds

# Generate the string to sign
$stringToSign = $targetUri + "`n" + $expiry

# Generate the signature
$hmac = New-Object System.Security.Cryptography.HMACSHA256
$hmac.Key = [Text.Encoding]::ASCII.GetBytes($SasKey)
$signature = $hmac.ComputeHash([Text.Encoding]::ASCII.GetBytes($stringToSign))
$signature = [Convert]::ToBase64String($signature)

# Generate the SAS token
$encodedSignature = [System.Web.HttpUtility]::UrlEncode($signature)
$sasToken = "sr=$targetUri&sig=$encodedSignature&se=$expiry&skn=$SasKeyName"

# Output the SAS token
$sasToken