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@@ -0,0 +1,212 @@
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+using System;
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+using System.IO;
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+using System.Security.Cryptography;
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+
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+namespace HiTeachCE.Extension
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+{
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+ public static class RSAUtils
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+ {
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+ private const string PrivateKeyHeader = "-----BEGIN RSA PRIVATE KEY-----";
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+ private const string PrivateKeyFooter = "-----END RSA PRIVATE KEY-----";
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+
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+ public static RSA? FromPrivateKey(string key)
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+ {
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+ key = key.Trim();
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+
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+ if (!key.StartsWith(PrivateKeyHeader) || !key.EndsWith(PrivateKeyFooter))
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+ throw new ArgumentException("Expect PKCS#1 PEM format key");
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+
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+ key = key.Substring(PrivateKeyHeader.Length, key.Length - PrivateKeyHeader.Length - PrivateKeyFooter.Length);
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+
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+ // Convert.FromBase64String ignores whitespace
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+ byte[] keyBytes = Convert.FromBase64String(key);
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+ return DecodeRSAPrivateKey(keyBytes);
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+ }
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+
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+ //------- Parses binary ans.1 RSA private key; returns RSA ---
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+ static RSA? DecodeRSAPrivateKey(byte[] privateKey)
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+ {
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+
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+ // --------- Set up stream to decode the asn.1 encoded RSA private key ------
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+ using var mem = new MemoryStream(privateKey);
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+ using var binr = new BinaryReader(mem);
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+ byte bt = 0;
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+ ushort twobytes = 0;
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+ twobytes = binr.ReadUInt16();
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+ if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
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+ binr.ReadByte(); //advance 1 byte
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+ else if (twobytes == 0x8230)
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+ binr.ReadInt16(); //advance 2 bytes
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+ else
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+ return null;
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+
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+ twobytes = binr.ReadUInt16();
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+ if (twobytes != 0x0102) //version number
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+ return null;
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+ bt = binr.ReadByte();
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+ if (bt != 0x00)
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+ return null;
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+
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+ // ------- create RSA from private key RSAParameters -----
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+ var rsaParameters = new RSAParameters
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+ {
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+ Modulus = binr.ReadBytes(GetIntegerSize(binr)),
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+ Exponent = binr.ReadBytes(GetIntegerSize(binr)),
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+ D = binr.ReadBytes(GetIntegerSize(binr)),
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+ P = binr.ReadBytes(GetIntegerSize(binr)),
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+ Q = binr.ReadBytes(GetIntegerSize(binr)),
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+ DP = binr.ReadBytes(GetIntegerSize(binr)),
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+ DQ = binr.ReadBytes(GetIntegerSize(binr)),
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+ InverseQ = binr.ReadBytes(GetIntegerSize(binr)),
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+ };
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+ return RSA.Create(rsaParameters);
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+ }
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+
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+ private const string PublicKeyHeader = "-----BEGIN PUBLIC KEY-----";
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+ private const string PublicKeyFooter = "-----END PUBLIC KEY-----";
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+
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+ public static RSA? FromPublicKey(string key)
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+ {
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+ key = key.Trim();
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+
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+ if (!key.StartsWith(PublicKeyHeader) || !key.EndsWith(PublicKeyFooter))
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+ throw new ArgumentException("Expect PKCS#1 PEM format key");
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+
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+ key = key.Substring(PublicKeyHeader.Length, key.Length - PublicKeyHeader.Length - PublicKeyFooter.Length);
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+
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+ // Convert.FromBase64String ignores whitespace
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+ byte[] keyBytes = Convert.FromBase64String(key);
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+ return DecodeX509PublicKey(keyBytes);
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+ }
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+
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+ static RSA? DecodeX509PublicKey(byte[] x509Key)
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+ {
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+ // encoded OID sequence for PKCS #1 rsaEncryption szOID_RSA_RSA = "1.2.840.113549.1.1.1"
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+ byte[] seqOid = { 0x30, 0x0D, 0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x01, 0x01, 0x05, 0x00 };
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+ // --------- Set up stream to read the asn.1 encoded SubjectPublicKeyInfo blob ------
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+ using var mem = new MemoryStream(x509Key);
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+ using var binr = new BinaryReader(mem);
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+ ushort twobytes = binr.ReadUInt16();
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+ switch (twobytes)
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+ {
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+ case 0x8130:
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+ binr.ReadByte(); //advance 1 byte
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+ break;
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+ case 0x8230:
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+ binr.ReadInt16(); //advance 2 bytes
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+ break;
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+ default:
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+ return null;
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+ }
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+
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+ byte[] seq = binr.ReadBytes(15);
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+ if (!CompareBytearrays(seq, seqOid)) //make sure Sequence for OID is correct
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+ return null;
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+
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+ twobytes = binr.ReadUInt16();
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+ if (twobytes == 0x8103) //data read as little endian order (actual data order for Bit String is 03 81)
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+ binr.ReadByte(); //advance 1 byte
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+ else if (twobytes == 0x8203)
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+ binr.ReadInt16(); //advance 2 bytes
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+ else
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+ return null;
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+
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+ byte bt = binr.ReadByte();
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+ if (bt != 0x00) //expect null byte next
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+ return null;
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+
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+ twobytes = binr.ReadUInt16();
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+ if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
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+ binr.ReadByte(); //advance 1 byte
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+ else if (twobytes == 0x8230)
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+ binr.ReadInt16(); //advance 2 bytes
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+ else
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+ return null;
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+
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+ twobytes = binr.ReadUInt16();
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+ byte lowbyte = 0x00;
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+ byte highbyte = 0x00;
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+
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+ if (twobytes == 0x8102) //data read as little endian order (actual data order for Integer is 02 81)
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+ lowbyte = binr.ReadByte(); // read next bytes which is bytes in modulus
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+ else if (twobytes == 0x8202)
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+ {
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+ highbyte = binr.ReadByte(); //advance 2 bytes
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+ lowbyte = binr.ReadByte();
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+ }
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+ else
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+ return null;
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+ byte[] modint = { lowbyte, highbyte, 0x00, 0x00 }; //reverse byte order since asn.1 key uses big endian order
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+ int modsize = BitConverter.ToInt32(modint, 0);
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+
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+ byte firstbyte = binr.ReadByte();
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+ binr.BaseStream.Seek(-1, SeekOrigin.Current);
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+
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+ if (firstbyte == 0x00)
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+ { //if first byte (highest order) of modulus is zero, don't include it
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+ binr.ReadByte(); //skip this null byte
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+ modsize -= 1; //reduce modulus buffer size by 1
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+ }
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+
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+ byte[] modulus = binr.ReadBytes(modsize); //read the modulus bytes
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+
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+ if (binr.ReadByte() != 0x02) //expect an Integer for the exponent data
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+ return null;
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+ int expbytes = binr.ReadByte(); // should only need one byte for actual exponent data (for all useful values)
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+ byte[] exponent = binr.ReadBytes(expbytes);
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+
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+ // ------- create RSA from public key RSAParameters -----
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+ var rsaParameters = new RSAParameters
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+ {
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+ Modulus = modulus,
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+ Exponent = exponent
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+ };
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+ return RSA.Create(rsaParameters);
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+ }
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+
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+ private static int GetIntegerSize(BinaryReader binr)
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+ {
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+ byte bt = binr.ReadByte();
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+ if (bt != 0x02) //expect integer
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+ return 0;
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+ bt = binr.ReadByte();
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+
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+ int count;
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+ if (bt == 0x81)
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+ count = binr.ReadByte(); // data size in next byte
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+ else
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+ if (bt == 0x82)
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+ {
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+ byte highbyte = binr.ReadByte();
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+ byte lowbyte = binr.ReadByte();
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+ byte[] modint = { lowbyte, highbyte, 0x00, 0x00 };
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+ count = BitConverter.ToInt32(modint, 0);
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+ }
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+ else
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+ {
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+ count = bt; // we already have the data size
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+ }
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+
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+ while (binr.ReadByte() == 0x00)
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+ { //remove high order zeros in data
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+ count -= 1;
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+ }
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+ binr.BaseStream.Seek(-1, SeekOrigin.Current); //last ReadByte wasn't a removed zero, so back up a byte
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+ return count;
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+ }
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+
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+ static bool CompareBytearrays(byte[] a, byte[] b)
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+ {
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+ if (a.Length != b.Length)
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+ return false;
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+ int i = 0;
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+ foreach (byte c in a)
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+ {
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+ if (c != b[i])
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+ return false;
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+ i++;
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+ }
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+ return true;
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+ }
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+ }
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+}
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