private static void AppendSri(
StringBuilder stringBuilder,
byte[] bytes,
SubresourceIntegrityHashAlgorithm hashAlgorithm)
{
switch (hashAlgorithm)
{
case SubresourceIntegrityHashAlgorithm.SHA256:
stringBuilder.Append("sha256-");
stringBuilder.Append(GetHash <SHA256>(bytes));
break;
case SubresourceIntegrityHashAlgorithm.SHA384:
stringBuilder.Append("sha384-");
stringBuilder.Append(GetHash <SHA384>(bytes));
break;
case SubresourceIntegrityHashAlgorithm.SHA512:
stringBuilder.Append("sha512-");
stringBuilder.Append(GetHash <SHA512>(bytes));
break;
default:
throw new ArgumentException(
FormattableString.Invariant($"Hash algorithm not recognized. HashAlgorithm<{hashAlgorithm}>."),
nameof(hashAlgorithm));
}
}
private static IEnumerable <SubresourceIntegrityHashAlgorithm> GetFlags(SubresourceIntegrityHashAlgorithm enumeration)
{
foreach (var value in (IEnumerable <SubresourceIntegrityHashAlgorithm>)Enum.GetValues(enumeration.GetType()))
{
if (enumeration.HasFlag(value))
{
yield return(value);
}
}
}
private string GetSubresourceIntegrityFromContentFile(
string contentPath,
SubresourceIntegrityHashAlgorithm hashAlgorithms)
{
var filePath = Path.Combine(
this.webHostEnvironment.ContentRootPath,
this.urlHelper.Content(contentPath).TrimStart('/'));
var bytes = this.ReadAllBytes(filePath);
return(GetSpaceDelimetedSri(bytes, hashAlgorithms));
}
private static string GetSpaceDelimetedSri(byte[] bytes, SubresourceIntegrityHashAlgorithm hashAlgorithms)
{
List <string> items = new List <string>(3);
foreach (SubresourceIntegrityHashAlgorithm hashAlgorithm in GetFlags(hashAlgorithms))
{
items.Add(GetSri(bytes, hashAlgorithm));
}
return(string.Join(" ", items));
}
private static string GetSpaceDelimetedSri(byte[] bytes, SubresourceIntegrityHashAlgorithm hashAlgorithms)
{
var stringBuilder = new StringBuilder();
foreach (var hashAlgorithm in GetFlags(hashAlgorithms))
{
if (stringBuilder.Length > 0)
{
stringBuilder.Append(' ');
}
AppendSri(stringBuilder, bytes, hashAlgorithm);
}
return(stringBuilder.ToString());
}
private static string GetSri(byte[] bytes, SubresourceIntegrityHashAlgorithm hashAlgorithm)
{
switch (hashAlgorithm)
{
case SubresourceIntegrityHashAlgorithm.SHA256:
return("sha256-" + GetHash <SHA256>(bytes));
case SubresourceIntegrityHashAlgorithm.SHA384:
return("sha384-" + GetHash <SHA384>(bytes));
case SubresourceIntegrityHashAlgorithm.SHA512:
return("sha512-" + GetHash <SHA512>(bytes));
default:
throw new ArgumentException(
$"Hash algorithm not recognized. HashAlgorithm<{hashAlgorithm}>.",
nameof(hashAlgorithm));
}
}
