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I currently have an App_Offline.htm file that works fine. When it's on the root of the site, all users are forces to the App_Offline.htm page and the application is prevented from loading.

We are adding some animations and images and the only proper way to do it in an App_Offline.htm is to use base64 images, inline.

The minute I add this (note I shortened the base64 for the post), it works if I go to the file in the browser directly but IIS/Azure/App Service, does not automatically force users to the page and prevent the app like it normally does.

      .image2 {
        width: 57px;
        height: 54px;
        background-image: url(data:image/png;base64,iVBOR.....rkJggg==);
      }

I figure there some content security setting or something I need add. Even though the page loads properly, what's preventing IIS/App Service from forcing everyone to the page when it has a base64 image?

Unless there's a file limit size, it's current 2896 KB, but from research there doesn't seem to be one.

Mastro
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  • What do you run on your App Service? Is it a static site, ASP.NET Core, or something else? I have just created a simple test with a static site on Azure App Service and it shows `App_Offline.htm` page for URLs like https://base64test.azurewebsites.net/help/ whenever there is or there is no base64 image on the page. But it shows me a real static page when I specifile the page name: https://base64test.azurewebsites.net/help/index.html. – Roman Klimenko Jan 21 '21 at 22:57
  • If my solution inspires or helps you, you mark my answer as [accepted](https://meta.stackexchange.com/questions/5234/how-does-accepting-an-answer-work) , Tks~ – Jason Pan Jan 28 '21 at 03:44

1 Answers1

0

Normally, when you have the app_offline.htm file in the application root directory, your web application will be closed and all requests will be directed to the app_offline.html page.

So you have two ways,

  1. You can write .image2 related code in app_offline.htm

  2. Put the .css on other websites, or use other addresses to access the files.

Related Post

Add css style sheet to app_offline

PRIVIOUS

For more details, you can refer my sample code, you just need to replace base64 image code.

My test result.

enter image description here

<!DOCTYPE html>
<html>
<head>
    <style type="text/css">
        @font-face {
            font-family: "Open Sans";
            font-style: normal;
            font-weight: 400;
            src: local("Segoe UI"), local("Open Sans"), local("OpenSans"), url(https://themes.googleusercontent.com/static/fonts/opensans/v6/K88pR3goAWT7BTt32Z01mz8E0i7KZn-EPnyo3HZu7kw.woff) format('woff');
        }

        body {
            font-family: "Open Sans";
        }

        h1 {
            font-size: 90px !important;
        }

        .error-page-container {
            color: #333333;
            margin: 50px auto 0;
            text-align: center;
            width: 600px;
        }

        .error-page-container h1 {
            font-size: 120px;
            font-weight: normal;
            line-height: 120px;
            margin: 10px 0;
            font-family: "Open Sans";
        }

        .error-page-container h2 {
            border-bottom: 1px solid #CCCCCC;
            color: #666666;
            font-size: 18px;
            font-weight: normal; /*text-transform: uppercase;*/
            font-family: "Open Sans";
        }

        .error-page-container a {
            text-decoration: none;
            color: #ffffff;
            background-color: #009AD7;
            padding: 11px 19px;
        }

        .error-page-container a:hover {
            text-decoration: none;
        }

        .image2 {
            width: 500px;
            height: 300px;
            background-image: url('data:image/png;base64,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');
        }
    </style>


    <title>
        Under Maintenance
    </title>
</head>
<body>
    <div class="error-page-container">
        <h1>Maintenance</h1>
        <div class="image2" src="" alt="test">
        </div>
        <h2>
            <p>Website is under maintenance right now. It will be back in few minutes.</p>
        </h2>
        <br />
        <a href="/">Try again</a>
    </div>
</body>
</html>
Jason Pan
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  • `` will also work, but the author clearly states that "IIS/Azure/App Service, does not automatically force users to the page and prevent the app like it normally does". This is not a markup problem. – Roman Klimenko Jan 25 '21 at 14:08
  • @RomanKlimenko Have you tried it yourself? Is the result of my demo fake? – Jason Pan Jan 26 '21 at 01:44
  • @RomanKlimenko According to my test results, the base64 image is displayed normally and the App_Offline file exists in the application, which prevents access to other resources. – Jason Pan Jan 26 '21 at 01:46
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    answering both of your questions: yes, I did try myself and no, I didn't say that your demo is fake. What I say is that the original question was not about rendering base64, it was about the fact that: _"Even though **the page loads properly**, what's **preventing IIS/App Service from forcing everyone to the page** when it has a base64 image?"_. In my experiments, base64 doesn't affect such behavior for a static site. This is why I am asking the author which engine they use for their site. – Roman Klimenko Jan 26 '21 at 07:25
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    @RomanKlimenko I got it clear, I put the css code in another file and found the problem. Thanks for reminding. – Jason Pan Jan 26 '21 at 07:50
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    Yes @RomanKlimenko you are correct, this doesn't answer my question, other then use another website. I can get the app_offline working with the base64 image if I load it up directly. I don't want to use an external website. The odd issue is, there is some content security, or a setting, I believe, that is preventing iis from using the app_offline automatically, to redirect users when it has the base64 image in it. Because if I remove the base64, it redirects users like expected. I add it back in, and it stops. – Mastro Jan 28 '21 at 03:58
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    @Mastro Can you show your app_offine.html code for us, we can test and help you. – Jason Pan Jan 28 '21 at 04:02
  • @Mastro You can also use my sample code to try it out. Put the base64 image you mentioned, and it stops, I haven't encountered it. – Jason Pan Jan 28 '21 at 04:03