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Fix issue #235: Preserve base64 encoded images and URLs during CSS parsing and style application #429

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martinnormark merged 2 commits into from
May 24, 2025
Merged

Fix issue #235: Preserve base64 encoded images and URLs during CSS parsing and style application #429

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fbeb66d
Fix issue #235: Preserve base64 encoded images and URLs during CSS pa…
devin-ai-integration[bot] May 23, 2025
af9e996
Refactor StyleClassApplier to simplify data URL quote handling
devin-ai-integration[bot] May 24, 2025
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50 changes: 50 additions & 0 deletions PreMailer.Net/PreMailer.Net.Tests/Base64UrlTests.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,50 @@
using System;
using Xunit;

namespace PreMailer.Net.Tests
{
public class Base64UrlTests
{
[Fact]
public void MoveCssInline_WithUnquotedBase64BackgroundImage_ShouldPreserveBase64Data()
{
string input = "<style>.pt-logo { background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAA); background-repeat: no-repeat; }</style><span class=\"pt-logo\"></span>";

var result = PreMailer.MoveCssInline(input);

Assert.Contains("background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAA)", result.Html);
Assert.Contains("background-repeat: no-repeat", result.Html);
}

[Fact]
public void MoveCssInline_WithQuotedBase64BackgroundImage_ShouldPreserveBase64Data()
{
string input = "<style>.pt-logo { background-image: url(\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAA\"); background-repeat: no-repeat; }</style><span class=\"pt-logo\"></span>";

var result = PreMailer.MoveCssInline(input);

Assert.Contains("background-image: url(\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAA\")", result.Html);
Assert.Contains("background-repeat: no-repeat", result.Html);
}

[Fact]
public void MoveCssInline_WithSvgXmlBackgroundImage_ShouldPreserveEncodedData()
{
string input = "<style>.my-icon { background-image: url(\"data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' fill='%23fff' width='8' height='8' viewBox='0 0 8 8'%3e%3cpath d='M5.25 0l-4 4 4 4 1.5-1.5L4.25 4l2.5-2.5L5.25 0z'/%3e%3c/svg%3e\"); }</style><span class=\"my-icon\"></span>";

var result = PreMailer.MoveCssInline(input);

Assert.Contains("background-image: url(\"data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' fill='%23fff' width='8' height='8' viewBox='0 0 8 8'%3e%3cpath d='M5.25 0l-4 4 4 4 1.5-1.5L4.25 4l2.5-2.5L5.25 0z'/%3e%3c/svg%3e\")", result.Html);
}

[Fact]
public void MoveCssInline_WithBase64DataWithDoubleEquals_ShouldPreserveEnding()
{
string input = "<style>.pt-logo { background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAA==); }</style><span class=\"pt-logo\"></span>";

var result = PreMailer.MoveCssInline(input);

Assert.Contains("background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAA==)", result.Html);
}
}
}
7 changes: 5 additions & 2 deletions PreMailer.Net/PreMailer.Net/CssParser.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -128,8 +128,8 @@ private static string CleanUp(string s)
temp = Regex.Replace(temp, "(['\"])([^'\"\\\\]*(?:\\\\.[^'\"\\\\]*)*?)http://([^'\"]*?)\\1", m =>
m.Groups[1].Value + m.Groups[2].Value + "http:" + httpProtocolMarker + m.Groups[3].Value + m.Groups[1].Value);

temp = Regex.Replace(temp, "(data:[^;]+;base64,[^)\"']*?)//([^)\"']*)", m =>
m.Groups[1].Value + dataUrlMarker + m.Groups[2].Value);
temp = Regex.Replace(temp, "(data:[^;]+;base64,)([^)\"']*?)//([^)\"']*)", m =>
m.Groups[1].Value + m.Groups[2].Value + dataUrlMarker + m.Groups[3].Value);

temp = _cssCommentRegex.Replace(temp, "");
temp = _unsupportedAtRuleRegex.Replace(temp, "");
Expand All @@ -141,6 +141,9 @@ private static string CleanUp(string s)
temp = temp.Replace(httpProtocolMarker, "//");
temp = temp.Replace(dataUrlMarker, "//");

temp = Regex.Replace(temp, @"url\s*\(\s*(['""]?)data:([^;]+);base64,([^)'""]*)(['""]?)\s*\)", m =>
"url(" + m.Groups[1].Value + "data:" + m.Groups[2].Value + ";base64," + m.Groups[3].Value + m.Groups[4].Value + ")");

return temp;
}

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9 changes: 7 additions & 2 deletions PreMailer.Net/PreMailer.Net/StyleClassApplier.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -47,10 +47,15 @@ private static void SetAttribute(IElement domElement, AttributeToCss attributeTo
value = value.Replace("px", string.Empty);
}

// Quotation marks in CSS is common, but when applied to the style attribute we will use single quotes instead.
if (value.Contains("\""))
{
value = value.Replace("\"", "'");
if (value.Contains("data:") && value.Contains(";base64,"))
{
}
else
{
value = value.Replace("\"", "'");
}
}

domElement.SetAttribute(name, value);
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