ASP.NET Core web.config publishing blues

January 25, 2017 | by Dominique St-Amand | 1 Comment

1 min read

I’ve been working on being able to use Octopus Deploy to deploy ASP.NET Core applications through IIS and I was faced with an interesting challenge. When publishing to a File System through the Visual Studio Publish command, it will trigger a PowerShell script that essentially will call Microsoft Web Deploy V3 (msdeploy) to put your FileSystem up to date with your release. But before calling MSDeploy, it will update (or should I say overwrite) your web.config with the proper handlers that match your application. This means that it will create a generic web.config and removing all the settings you may want. The ASP.NET team is aware I believe of the fact that the publishing tool is limited and thus in need of some customization features wise.

Using Octopus Deploy as a deployment solution, there are some solutions which you can take to fix the above situation.

One solution is to have a copy of your web.config say, web.{environment}.config and replace the original web.config with that said web.{environment}.config file. I find that approach not as smooth as I would like. MSDeploy uses variables to replace certain attributes values and this means you will have to maintain that on each of your environment web.config.

I chose another approach where I run a PreDeploy PowerShell script that will add the proper configurations to my web.config before the application is deployed.
Here is the PreDeploy PowerShell script that I use to set the Rewrite Rule for HTTP to HTTPs and to set some custom headers. Feel free to use any other language that Octopus Deploy supports (C#, F#, etc).

The script can definitely be improved, but it is simple enough that I did not bother 🙂

function SetRewrite([xml]$config) {
    Write-Host "Setting HTTP(s) to HTTPS rewrite rule";
    
    $systemWebHandlers = $config.SelectSingleNode("//system.webServer");

    $rewrite = $config.CreateElement("rewrite");

    $rules = $config.CreateElement("rules");

    $rule = $config.CreateElement("rule");
    $ruleNameAttribute = $config.CreateAttribute("name");
    $ruleNameAttribute.Value = "HTTP/S to HTTPS Redirect";
    $stopProcessingAttribute = $config.CreateAttribute("stopProcessing");
    $stopProcessingAttribute.Value = "true";
    $rule.Attributes.Append($ruleNameAttribute);
    $rule.Attributes.Append($stopProcessingAttribute);

    $matchNode = $config.CreateElement("match");
    $matchNodeUrlAttribute = $config.CreateAttribute("url");
    $matchNodeUrlAttribute.Value = "(.*)";
    $matchNode.Attributes.Append($matchNodeUrlAttribute);
    $rule.AppendChild($matchNode);

    $conditionsNode = $config.CreateElement("conditions");
    $conditionAddNode = $config.CreateElement("add");
    $inputAttribute = $config.CreateAttribute("input");
    $inputAttribute.Value = "{HTTPS}";
    $patternAttribute = $config.CreateAttribute("pattern");
    $patternAttribute.Value = "^OFF$";
    $conditionAddNode.Attributes.Append($inputAttribute);
    $conditionAddNode.Attributes.Append($patternAttribute);
    $conditionsNode.AppendChild($conditionAddNode);
    $rule.AppendChild($conditionsNode);

    $actionNode = $config.CreateElement("action");
    $typeAttribute = $config.CreateAttribute("type");
    $typeAttribute.Value = "Redirect";
    $actionNodeUrlAttribute = $config.CreateAttribute("url");
    $actionNodeUrlAttribute.Value = "https://{HTTP_HOST}";
    $actionNode.Attributes.Append($typeAttribute);
    $actionNode.Attributes.Append($actionNodeUrlAttribute);
    $rule.AppendChild($actionNode);

    $rules.AppendChild($rule);
    $rewrite.AppendChild($rules);
    $systemWebHandlers.AppendChild($rewrite);
}

function SetCustomHeaders([xml]$config){
    Write-Host "Setting CustomHeaders";

    $systemWebHandlers = $config.SelectSingleNode("//system.webServer");

    $httpProtocolNode = $config.CreateElement("httpProtocol");
    $customHeadersNode = $config.CreateElement("customHeaders");
    $customHeaderRemoveNode = $config.CreateElement("remove");
    $customHeaderRemoveNodeAttributeName = $config.CreateAttribute("name");
    $customHeaderRemoveNodeAttributeName.Value = "X-Powered-By";
    $customHeaderRemoveNode.Attributes.Append($customHeaderRemoveNodeAttributeName);
    $customHeadersNode.AppendChild($customHeaderRemoveNode);
    $httpProtocolNode.AppendChild($customHeadersNode);
    $systemWebHandlers.AppendChild($httpProtocolNode);
}

$deploymentPath = $OctopusParameters["Octopus.Action[Deploy site].Output.Package.InstallationDirectoryPath"];
$filepath = (Join-Path $deploymentPath "web.config");

Write-Host "Modifying $filepath";
$config = [xml](Get-Content $filepath);

[void](SetRewrite($config));
[void](SetCustomHeaders($config));

Write-Host "Saving changes...";
$config.Save($filepath);

function SetRewrite([xml]$config) {

Write-Host "Setting HTTP(s) to HTTPS rewrite rule";

$systemWebHandlers = $config.SelectSingleNode("//system.webServer");

$rewrite = $config.CreateElement("rewrite");

$rules = $config.CreateElement("rules");

$rule = $config.CreateElement("rule");

$ruleNameAttribute = $config.CreateAttribute("name");

$ruleNameAttribute.Value = "HTTP/S to HTTPS Redirect";

$stopProcessingAttribute = $config.CreateAttribute("stopProcessing");

$stopProcessingAttribute.Value = "true";

$rule.Attributes.Append($ruleNameAttribute);

$rule.Attributes.Append($stopProcessingAttribute);

$matchNode = $config.CreateElement("match");

$matchNodeUrlAttribute = $config.CreateAttribute("url");

$matchNodeUrlAttribute.Value = "(.*)";

$matchNode.Attributes.Append($matchNodeUrlAttribute);

$rule.AppendChild($matchNode);

$conditionsNode = $config.CreateElement("conditions");

$conditionAddNode = $config.CreateElement("add");

$inputAttribute = $config.CreateAttribute("input");

$inputAttribute.Value = "{HTTPS}";

$patternAttribute = $config.CreateAttribute("pattern");

$patternAttribute.Value = "^OFF$";

$conditionAddNode.Attributes.Append($inputAttribute);

$conditionAddNode.Attributes.Append($patternAttribute);

$conditionsNode.AppendChild($conditionAddNode);

$rule.AppendChild($conditionsNode);

$actionNode = $config.CreateElement("action");

$typeAttribute = $config.CreateAttribute("type");

$typeAttribute.Value = "Redirect";

$actionNodeUrlAttribute = $config.CreateAttribute("url");

$actionNodeUrlAttribute.Value = "https://{HTTP_HOST}";

$actionNode.Attributes.Append($typeAttribute);

$actionNode.Attributes.Append($actionNodeUrlAttribute);

$rule.AppendChild($actionNode);

$rules.AppendChild($rule);

$rewrite.AppendChild($rules);

$systemWebHandlers.AppendChild($rewrite);

}

function SetCustomHeaders([xml]$config){

Write-Host "Setting CustomHeaders";

$systemWebHandlers = $config.SelectSingleNode("//system.webServer");

$httpProtocolNode = $config.CreateElement("httpProtocol");

$customHeadersNode = $config.CreateElement("customHeaders");

$customHeaderRemoveNode = $config.CreateElement("remove");

$customHeaderRemoveNodeAttributeName = $config.CreateAttribute("name");

$customHeaderRemoveNodeAttributeName.Value = "X-Powered-By";

$customHeaderRemoveNode.Attributes.Append($customHeaderRemoveNodeAttributeName);

$customHeadersNode.AppendChild($customHeaderRemoveNode);

$httpProtocolNode.AppendChild($customHeadersNode);

$systemWebHandlers.AppendChild($httpProtocolNode);

}

$deploymentPath = $OctopusParameters["Octopus.Action[Deploy site].Output.Package.InstallationDirectoryPath"];

$filepath = (Join-Path $deploymentPath "web.config");

Write-Host "Modifying $filepath";

$config = [xml](Get-Content $filepath);

[void](SetRewrite($config));

[void](SetCustomHeaders($config));

Write-Host "Saving changes...";

$config.Save($filepath);

There are probably other ways that I am not aware of and I would love to hear from you so don’t be shy to comment or to tweet me!

ASP.NET Core web.config publishing blues

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ASP.NET Core web.config publishing blues

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