FromBase64Transform whitespace issue

[appelgjo]

This program gets a System.IndexOutOfRangeException in .NET Core 6, both on Windows and Linux:

using System.Security.Cryptography;
using System.Text;

string b64 =
    "TG9yZW0gaXBzdW0gZG9sb3Igc2l0IGFtZXQsIGNvbnNlY3RldHVyIGFkaXBpc2Np" +
    "\n" +
    "bmcgZWxpdC4K";
using Stream input = new MemoryStream(Encoding.ASCII.GetBytes(b64));
using ICryptoTransform decoder = new FromBase64Transform(FromBase64TransformMode.IgnoreWhiteSpaces);
using Stream decoding = new CryptoStream(input, decoder, CryptoStreamMode.Read);
using Stream output = Console.OpenStandardOutput();
decoding.CopyTo(output);

"\r\n" instead of "\n" works fine.

Similar to #46922 .

[ghost]

Tagging subscribers to this area: @dotnet/area-system-security, @vcsjones
See info in area-owners.md if you want to be subscribed.

Issue Details

---

This program gets a System.IndexOutOfRangeException in .NET Core 6, both on Windows and Linux:

using System.Security.Cryptography;
using System.Text;

string b64 =
    "TG9yZW0gaXBzdW0gZG9sb3Igc2l0IGFtZXQsIGNvbnNlY3RldHVyIGFkaXBpc2Np" +
    "\n" +
    "bmcgZWxpdC4K";
using Stream input = new MemoryStream(Encoding.ASCII.GetBytes(b64));
using ICryptoTransform decoder = new FromBase64Transform(FromBase64TransformMode.IgnoreWhiteSpaces);
using Stream decoding = new CryptoStream(input, decoder, CryptoStreamMode.Read);
using Stream output = Console.OpenStandardOutput();
decoding.CopyTo(output);

"\r\n" instead of "\n" works fine.

Similar to #46922 .

Author:	appelgjo
Assignees:	-
Labels:	area-System.Security
Milestone:	-

[gfoidl]

Sounds similar to #76918

[appelgjo]

Duplicate of #76918

[vcsjones]

Thanks for the issue report. Since a duplicate has been identified, I am going to close this one out in favor of the linked issue.