adding in changes for the nonce service

src/Joonasw.AspNetCore.SecurityHeaders/Csp/CspNonceService.cs

@@ -6,6 +6,12 @@ namespace Joonasw.AspNetCore.SecurityHeaders.Csp
     public class CspNonceService : ICspNonceService
     {
         private readonly string _nonce;
+        private const char Base64PadCharacter = '=';
+        private const string DoubleBase64PadCharacter = "==";
+        private const char Base64Character62 = '+';
+        private const char Base64Character63 = '/';
+        private const char Base64UrlCharacter62 = '-';
+        private const char Base64UrlCharacter63 = '_';
 
         public CspNonceService(int nonceByteAmount = 32)
         {
@@ -15,7 +21,15 @@ public CspNonceService(int nonceByteAmount = 32)
                 rng.GetBytes(nonceBytes);
             }
 
-            _nonce = Convert.ToBase64String(nonceBytes);
+          var s = Convert.ToBase64String(nonceBytes);
+          // a base64String can have elements that aren't URL friendly. In testing chrome appeared to ignore nonces that weren't URL friendly (or the tag helper did).
+          // the replacement code comes from Microsoft.IdentityModel.Tokens.Base64UrlEncoder
+          s = s.Split(Base64PadCharacter)[0]; // Remove any trailing padding
+          s = s.Replace(Base64Character62, Base64UrlCharacter62);  // 62nd char of encoding
+          s = s.Replace(Base64Character63, Base64UrlCharacter63);  // 63rd char of encoding
+
+          _nonce = s;
+
         }
 
         public string GetNonce()

src/Joonasw.AspNetCore.SecurityHeaders/TagHelpers/NonceTagHelper.cs

@@ -26,7 +26,11 @@ public override void Process(TagHelperContext context, TagHelperOutput output)
             {
                 // The nonce service is created per request, so we
                 // get the same nonce here as the CSP header
-                output.Attributes.Add("nonce", _nonceService.GetNonce());
+                // when doing this, the nonce wasn't reliably being injected (that might have been due to the nonce have non url friendly chars). 
+                //output.Attributes.Add("nonce", _nonceService.GetNonce());
+                // this injected the nonce all the time.
+                var attribute = new TagHelperAttribute("nonce", _nonceService.GetNonce(), HtmlAttributeValueStyle.DoubleQuotes);
+                output.Attributes.SetAttribute(attribute);
             }
         }
     }

test/Joonasw.AspNetCore.SecurityHeaders.Tests/CspScriptsBuilderTests.cs

@@ -6,7 +6,9 @@
 
 namespace Joonasw.AspNetCore.SecurityHeaders.Tests
 {
-    public class CspScriptsBuilderTests
+  using Csp;
+
+  public class CspScriptsBuilderTests
     {
         [Fact]
         public void FromNowhere_SetsAllowNoneToTrue()
@@ -30,6 +32,24 @@ public void FromSelf_SetsAllowSelfToTrue()
             Assert.True(options.AllowSelf);
         }
 
+        [Fact]
+        public void FromSelf_WithNonce_HasValue()
+        {
+          var nonceService = new CspNonceService(32);
+          var nonce = nonceService.GetNonce();
+
+          var builder = new CspBuilder();
+          builder.AllowScripts.FromSelf().AddNonce();
+
+          var headerValue = builder.BuildCspOptions().ToString(nonceService).headerValue;
+
+          Assert.DoesNotContain("+", nonce);
+          Assert.DoesNotContain("/", nonce);
+          Assert.DoesNotContain("=", nonce);
+
+          Assert.Equal($"script-src 'self' 'nonce-{nonce}'", headerValue);
+        }
+
         [Fact]
         public void From_AddsUrlToAllowedSources()
         {