113 lines
4.7 KiB
C#
113 lines
4.7 KiB
C#
using System;
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using System.IO;
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using System.Security.Cryptography;
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namespace BirdsiteLive.Cryptography
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{
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//https://gist.github.com/ststeiger/f4b29a140b1e3fd618679f89b7f3ff4a
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//https://gist.github.com/valep27/4a720c25b35fff83fbf872516f847863
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//https://gist.github.com/therightstuff/aa65356e95f8d0aae888e9f61aa29414
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//https://stackoverflow.com/questions/52468125/export-rsa-public-key-in-der-format-and-decrypt-data
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public class RsaGenerator
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{
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public string GetRsa()
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{
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var rsa = RSA.Create();
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var outputStream = new StringWriter();
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var parameters = rsa.ExportParameters(true);
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using (var stream = new MemoryStream())
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{
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var writer = new BinaryWriter(stream);
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writer.Write((byte)0x30); // SEQUENCE
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using (var innerStream = new MemoryStream())
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{
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var innerWriter = new BinaryWriter(innerStream);
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innerWriter.Write((byte)0x30); // SEQUENCE
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EncodeLength(innerWriter, 13);
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innerWriter.Write((byte)0x06); // OBJECT IDENTIFIER
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var rsaEncryptionOid = new byte[]
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{
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0x2a,
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0x86,
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0x48,
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0x86,
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0xf7,
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0x0d,
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0x01,
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0x01,
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0x01
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};
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EncodeLength(innerWriter, rsaEncryptionOid.Length);
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innerWriter.Write(rsaEncryptionOid);
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innerWriter.Write((byte)0x05); // NULL
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EncodeLength(innerWriter, 0);
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innerWriter.Write((byte)0x03); // BIT STRING
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using (var bitStringStream = new MemoryStream())
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{
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var bitStringWriter = new BinaryWriter(bitStringStream);
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bitStringWriter.Write((byte)0x00); // # of unused bits
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bitStringWriter.Write((byte)0x30); // SEQUENCE
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using (var paramsStream = new MemoryStream())
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{
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var paramsWriter = new BinaryWriter(paramsStream);
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//EncodeIntegerBigEndian(paramsWriter, parameters.Modulus); // Modulus
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//EncodeIntegerBigEndian(paramsWriter, parameters.Exponent); // Exponent
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var paramsLength = (int)paramsStream.Length;
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EncodeLength(bitStringWriter, paramsLength);
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bitStringWriter.Write(paramsStream.GetBuffer(), 0, paramsLength);
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}
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var bitStringLength = (int)bitStringStream.Length;
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EncodeLength(innerWriter, bitStringLength);
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innerWriter.Write(bitStringStream.GetBuffer(), 0, bitStringLength);
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}
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var length = (int)innerStream.Length;
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EncodeLength(writer, length);
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writer.Write(innerStream.GetBuffer(), 0, length);
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}
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var base64 = Convert
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.ToBase64String(stream.GetBuffer(), 0, (int)stream.Length)
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.ToCharArray();
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// WriteLine terminates with \r\n, we want only \n
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outputStream.Write("-----BEGIN PUBLIC KEY-----\n");
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for (var i = 0; i < base64.Length; i += 64)
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{
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outputStream.Write(base64, i, Math.Min(64, base64.Length - i));
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outputStream.Write("\n");
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}
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outputStream.Write("-----END PUBLIC KEY-----");
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}
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return outputStream.ToString();
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}
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private static void EncodeLength(BinaryWriter stream, int length)
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{
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if (length < 0)
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throw new ArgumentOutOfRangeException("length", "Length must be non-negative");
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if (length < 0x80)
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{
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// Short form
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stream.Write((byte)length);
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}
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else
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{
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// Long form
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var temp = length;
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var bytesRequired = 0;
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while (temp > 0)
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{
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temp >>= 8;
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bytesRequired++;
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}
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stream.Write((byte)(bytesRequired | 0x80));
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for (var i = bytesRequired - 1; i >= 0; i--)
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{
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stream.Write((byte)(length >> (8 * i) & 0xff));
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}
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}
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}
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}
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}
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