Use System.Numerics.BigInteger

src/Renci.SshNet/Common/DerData.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Buffers.Binary;
 using System.Collections.Generic;
+using System.Numerics;
 
 namespace Renci.SshNet.Common
 {
@@ -96,7 +97,11 @@ public BigInteger ReadBigInteger()
 
             var data = ReadBytes(length);
 
+#if NETSTANDARD2_1_OR_GREATER || NET6_0_OR_GREATER
+            return new BigInteger(data, isBigEndian: true);
+#else
             return new BigInteger(data.Reverse());
+#endif
         }
 
         /// <summary>
@@ -213,7 +218,7 @@ public void Write(uint data)
         /// <param name="data">BigInteger data to write.</param>
         public void Write(BigInteger data)
         {
-            var bytes = data.ToByteArray().Reverse();
+            var bytes = data.ToByteArray(isBigEndian: true);
             _data.Add(Integer);
             var length = GetLength(bytes.Length);
             WriteBytes(length);

src/Renci.SshNet/Common/Extensions.cs

@@ -4,6 +4,7 @@
 using System.Globalization;
 using System.Net;
 using System.Net.Sockets;
+using System.Numerics;
 using System.Text;
 
 using Renci.SshNet.Abstractions;
@@ -14,7 +15,7 @@ namespace Renci.SshNet.Common
     /// <summary>
     /// Collection of different extension methods.
     /// </summary>
-    internal static partial class Extensions
+    internal static class Extensions
     {
         internal static byte[] ToArray(this ServiceName serviceName)
         {
@@ -45,26 +46,35 @@ internal static ServiceName ToServiceName(this byte[] data)
 
         internal static BigInteger ToBigInteger(this byte[] data)
         {
+#if NETSTANDARD2_1_OR_GREATER || NET6_0_OR_GREATER
+            return new BigInteger(data, isBigEndian: true);
+#else
             var reversed = new byte[data.Length];
             Buffer.BlockCopy(data, 0, reversed, 0, data.Length);
             return new BigInteger(reversed.Reverse());
+#endif
         }
 
         /// <summary>
         /// Initializes a new instance of the <see cref="BigInteger"/> structure using the SSH BigNum2 Format.
         /// </summary>
         public static BigInteger ToBigInteger2(this byte[] data)
         {
+#if NETSTANDARD2_1_OR_GREATER || NET6_0_OR_GREATER
+            return new BigInteger(data, isBigEndian: true, isUnsigned: true);
+#else
             if ((data[0] & (1 << 7)) != 0)
             {
                 var buf = new byte[data.Length + 1];
                 Buffer.BlockCopy(data, 0, buf, 1, data.Length);
-                data = buf;
+                return new BigInteger(buf.Reverse());
             }
 
             return data.ToBigInteger();
+#endif
         }
 
+#if NETFRAMEWORK || NETSTANDARD2_0
         public static byte[] ToByteArray(this BigInteger bigInt, bool isUnsigned = false, bool isBigEndian = false)
         {
             var data = bigInt.ToByteArray();
@@ -81,6 +91,15 @@ public static byte[] ToByteArray(this BigInteger bigInt, bool isUnsigned = false
 
             return data;
         }
+#endif
+
+#if !NET6_0_OR_GREATER
+        public static long GetBitLength(this BigInteger bigint)
+        {
+            // Taken from https://github.com/dotnet/runtime/issues/31308
+            return (long)Math.Ceiling(BigInteger.Log(bigint.Sign < 0 ? -bigint : bigint + 1, 2));
+        }
+#endif
 
         // See https://github.com/dotnet/runtime/blob/9b57a265c7efd3732b035bade005561a04767128/src/libraries/Common/src/System/Security/Cryptography/KeyBlobHelpers.cs#L51
         public static byte[] ExportKeyParameter(this BigInteger value, int length)

src/Renci.SshNet/Common/SshData.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Numerics;
 using System.Text;
 
 namespace Renci.SshNet.Common

src/Renci.SshNet/Common/SshDataStream.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Globalization;
 using System.IO;
+using System.Numerics;
 using System.Text;
 
 namespace Renci.SshNet.Common
@@ -110,7 +111,8 @@ public void Write(ulong value)
         /// <param name="data">The <see cref="BigInteger" /> to write.</param>
         public void Write(BigInteger data)
         {
-            var bytes = data.ToByteArray().Reverse();
+            var bytes = data.ToByteArray(isBigEndian: true);
+
             WriteBinary(bytes, 0, bytes.Length);
         }
 
@@ -211,9 +213,13 @@ public void WriteBinary(byte[] buffer, int offset, int count)
         /// </returns>
         public BigInteger ReadBigInt()
         {
-            var length = ReadUInt32();
-            var data = ReadBytes((int)length);
+            var data = ReadBinary();
+
+#if NETSTANDARD2_1_OR_GREATER || NET6_0_OR_GREATER
+            return new BigInteger(data, isBigEndian: true);
+#else
             return new BigInteger(data.Reverse());
+#endif
         }
 
         /// <summary>

src/Renci.SshNet/Messages/Transport/KeyExchangeDhGroupExchangeGroup.cs

@@ -1,4 +1,6 @@
-using Renci.SshNet.Common;
+using System.Numerics;
+
+using Renci.SshNet.Common;
 
 namespace Renci.SshNet.Messages.Transport
 {

src/Renci.SshNet/Messages/Transport/KeyExchangeEcdhInitMessage.cs

@@ -1,7 +1,5 @@
 using System;
 
-using Renci.SshNet.Common;
-
 namespace Renci.SshNet.Messages.Transport
 {
     /// <summary>
@@ -57,21 +55,6 @@ public KeyExchangeEcdhInitMessage(byte[] q)
             QC = q;
         }
 
-        /// <summary>
-        /// Initializes a new instance of the <see cref="KeyExchangeEcdhInitMessage"/> class.
-        /// </summary>
-        public KeyExchangeEcdhInitMessage(BigInteger d, BigInteger q)
-        {
-            var dBytes = d.ToByteArray().Reverse();
-            var qBytes = q.ToByteArray().Reverse();
-
-            var data = new byte[dBytes.Length + qBytes.Length + 1];
-            data[0] = 0x04;
-            Buffer.BlockCopy(dBytes, 0, data, 1, dBytes.Length);
-            Buffer.BlockCopy(qBytes, 0, data, dBytes.Length + 1, qBytes.Length);
-            QC = data;
-        }
-
         /// <summary>
         /// Called when type specific data need to be loaded.
         /// </summary>

src/Renci.SshNet/PrivateKeyFile.cs

@@ -3,6 +3,7 @@
 using System.Diagnostics;
 using System.Globalization;
 using System.IO;
+using System.Numerics;
 using System.Security.Cryptography;
 using System.Text;
 using System.Text.RegularExpressions;
@@ -713,22 +714,17 @@ public BigInteger ReadBigIntWithBits()
 
                 length = (length + 7) / 8;
 
-                var data = base.ReadBytes(length);
-                var bytesArray = new byte[data.Length + 1];
-                Buffer.BlockCopy(data, 0, bytesArray, 1, data.Length);
-
-                return new BigInteger(bytesArray.Reverse());
+                return base.ReadBytes(length).ToBigInteger2();
             }
 
             public BigInteger ReadBignum()
             {
-                return new BigInteger(ReadBignum2().Reverse());
+                return DataStream.ReadBigInt();
             }
 
             public byte[] ReadBignum2()
             {
-                var length = (int)base.ReadUInt32();
-                return base.ReadBytes(length);
+                return ReadBinary();
             }
 
             protected override void LoadData()

src/Renci.SshNet/Security/Cryptography/DsaKey.cs

@@ -1,5 +1,6 @@
 #nullable enable
 using System;
+using System.Numerics;
 using System.Security.Cryptography;
 
 using Renci.SshNet.Common;
@@ -46,7 +47,7 @@ public override int KeyLength
         {
             get
             {
-                return P.BitLength;
+                return (int)P.GetBitLength();
             }
         }
 

src/Renci.SshNet/Security/Cryptography/ED25519Key.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Numerics;
 
 using Org.BouncyCastle.Math.EC.Rfc8032;
 
@@ -87,7 +88,8 @@ public ED25519Key(SshKeyData publicKeyData)
                 throw new ArgumentException($"Invalid Ed25519 public key data ({publicKeyData.Name}, {publicKeyData.Keys.Length}).", nameof(publicKeyData));
             }
 
-            PublicKey = publicKeyData.Keys[0].ToByteArray().Reverse().TrimLeadingZeros().Pad(Ed25519.PublicKeySize);
+            PublicKey = publicKeyData.Keys[0].ToByteArray(isBigEndian: true).TrimLeadingZeros().Pad(Ed25519.PublicKeySize);
+            PrivateKey = new byte[Ed25519.SecretKeySize];
         }
 
         /// <summary>

src/Renci.SshNet/Security/Cryptography/EcdsaDigitalSignature.cs

@@ -95,11 +95,11 @@ public byte[] Signature
                 {
                     var signed_r = new byte[_signature_size / 2];
                     Buffer.BlockCopy(value, 0, signed_r, 0, signed_r.Length);
-                    _signature_r = signed_r.ToBigInteger2().ToByteArray().Reverse();
+                    _signature_r = signed_r.ToBigInteger2().ToByteArray(isBigEndian: true);
 
                     var signed_s = new byte[_signature_size / 2];
                     Buffer.BlockCopy(value, signed_r.Length, signed_s, 0, signed_s.Length);
-                    _signature_s = signed_s.ToBigInteger2().ToByteArray().Reverse();
+                    _signature_s = signed_s.ToBigInteger2().ToByteArray(isBigEndian: true);
                 }
             }
 
@@ -122,8 +122,8 @@ protected override void LoadData()
 
             protected override void SaveData()
             {
-                WriteBinaryString(_signature_r.ToBigInteger2().ToByteArray().Reverse());
-                WriteBinaryString(_signature_s.ToBigInteger2().ToByteArray().Reverse());
+                WriteBinaryString(_signature_r.ToBigInteger2().ToByteArray(isBigEndian: true));
+                WriteBinaryString(_signature_s.ToBigInteger2().ToByteArray(isBigEndian: true));
             }
 
             protected override int BufferCapacity

src/Renci.SshNet/Security/Cryptography/EcdsaKey.cs

@@ -1,6 +1,7 @@
-#nullable enable
+#nullable enable
 using System;
 using System.Diagnostics;
+using System.Numerics;
 using System.Security.Cryptography;
 using System.Text;
 
@@ -145,7 +146,11 @@ public override BigInteger[] Public
                 Buffer.BlockCopy(qy, 0, q, qx.Length + 1, qy.Length);
 
                 // returns Curve-Name and x/y as ECPoint
+#if NETSTANDARD2_1_OR_GREATER || NET6_0_OR_GREATER
+                return new[] { curve, new BigInteger(q, isBigEndian: true) };
+#else
                 return new[] { curve, new BigInteger(q.Reverse()) };
+#endif
             }
         }
 
@@ -191,10 +196,10 @@ public EcdsaKey(SshKeyData publicKeyData)
                 throw new ArgumentException($"Invalid ECDSA public key data. ({publicKeyData.Name}, {publicKeyData.Keys.Length}).", nameof(publicKeyData));
             }
 
-            var curve_s = Encoding.ASCII.GetString(publicKeyData.Keys[0].ToByteArray().Reverse());
+            var curve_s = Encoding.ASCII.GetString(publicKeyData.Keys[0].ToByteArray(isBigEndian: true));
             var curve_oid = GetCurveOid(curve_s);
 
-            var publickey = publicKeyData.Keys[1].ToByteArray().Reverse();
+            var publickey = publicKeyData.Keys[1].ToByteArray(isBigEndian: true);
             _impl = Import(curve_oid, publickey, privatekey: null);
         }
 

src/Renci.SshNet/Security/Cryptography/Key.cs

@@ -1,4 +1,5 @@
-using Renci.SshNet.Common;
+using System.Numerics;
+
 using Renci.SshNet.Security.Cryptography;
 
 namespace Renci.SshNet.Security

src/Renci.SshNet/Security/Cryptography/RsaKey.cs

@@ -1,5 +1,6 @@
 #nullable enable
 using System;
+using System.Numerics;
 using System.Security.Cryptography;
 
 using Renci.SshNet.Common;
@@ -96,7 +97,7 @@ public override int KeyLength
         {
             get
             {
-                return Modulus.BitLength;
+                return (int)Modulus.GetBitLength();
             }
         }
 

src/Renci.SshNet/Security/GroupExchangeHashData.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Numerics;
 
 using Renci.SshNet.Common;
 
@@ -38,13 +39,13 @@ public string ClientVersion
         public BigInteger Prime
         {
             private get { return _prime.ToBigInteger(); }
-            set { _prime = value.ToByteArray().Reverse(); }
+            set { _prime = value.ToByteArray(isBigEndian: true); }
         }
 
         public BigInteger SubGroup
         {
             private get { return _subGroup.ToBigInteger(); }
-            set { _subGroup = value.ToByteArray().Reverse(); }
+            set { _subGroup = value.ToByteArray(isBigEndian: true); }
         }
 
         public byte[] ClientExchangeValue { get; set; }

src/Renci.SshNet/Security/KeyExchangeDiffieHellman.cs

@@ -1,5 +1,7 @@
 using System;
+using System.Numerics;
 
+using Renci.SshNet.Abstractions;
 using Renci.SshNet.Common;
 using Renci.SshNet.Messages.Transport;
 
@@ -109,14 +111,26 @@ protected void PopulateClientExchangeValue()
             do
             {
                 // Create private component
-                _privateExponent = BigInteger.Random(privateExponentSize);
+                _privateExponent = RandomBigInt(privateExponentSize);
 
                 // Generate public component
                 clientExchangeValue = BigInteger.ModPow(_group, _privateExponent, _prime);
             }
             while (clientExchangeValue < 1 || clientExchangeValue > (_prime - 1));
 
-            _clientExchangeValue = clientExchangeValue.ToByteArray().Reverse();
+            _clientExchangeValue = clientExchangeValue.ToByteArray(isBigEndian: true);
+        }
+
+        /// <summary>
+        /// Generates a new, random <see cref="BigInteger"/> of the specified length.
+        /// </summary>
+        /// <param name="bitLength">The number of bits for the new number.</param>
+        /// <returns>A random number of the specified length.</returns>
+        private static BigInteger RandomBigInt(int bitLength)
+        {
+            var bytesArray = CryptoAbstraction.GenerateRandom((bitLength / 8) + (((bitLength % 8) > 0) ? 1 : 0));
+            bytesArray[bytesArray.Length - 1] = (byte)(bytesArray[bytesArray.Length - 1] & 0x7F); // Ensure not a negative value
+            return new BigInteger(bytesArray);
         }
 
         /// <summary>
@@ -129,7 +143,7 @@ protected virtual void HandleServerDhReply(byte[] hostKey, byte[] serverExchange
         {
             _serverExchangeValue = serverExchangeValue;
             _hostKey = hostKey;
-            SharedKey = BigInteger.ModPow(serverExchangeValue.ToBigInteger(), _privateExponent, _prime).ToByteArray().Reverse();
+            SharedKey = BigInteger.ModPow(serverExchangeValue.ToBigInteger(), _privateExponent, _prime).ToByteArray(isBigEndian: true);
             _signature = signature;
         }
     }