ET9_WebGL_Base/CSharp/App/BossClient/SRP6Client.cs

using System;
using System.Linq;
using System.Numerics;
using System.Security.Cryptography;
using Helper;

namespace BossClient
{
    public class SRP6Client
    {
        private readonly BigInteger n; // N
        private readonly BigInteger g; // g
        private readonly BigInteger b; // B
        private readonly BigInteger a; // A
        private readonly BigInteger x; // X
        private readonly BigInteger u; // U
        private readonly BigInteger s; // S
        private readonly BigInteger k; // K
        private readonly BigInteger m; // M
        private readonly byte[] p;
        private readonly byte[] account;
        private readonly BigInteger salt; // s, 服务端发过来的salt
        private const int lowerK = 3;
        private readonly BigInteger smallA;
        private readonly HashAlgorithm hashAlgorithm;

        public SRP6Client(
                HashAlgorithm hashAlgorithm, BigInteger n, BigInteger g, BigInteger b,
                BigInteger salt, byte[] account, byte[] passwordMd5Hex)
        {
            this.smallA = BigIntegerHelper.RandUnsignedBigInteger(19);

            this.hashAlgorithm = hashAlgorithm;
            this.n = n;
            this.g = g;
            this.b = b;
            this.salt = salt;
            this.account = account;
            this.p =
                    hashAlgorithm.ComputeHash(
                                              new byte[0].Concat(account)
                                                      .Concat(new[] { (byte) ':' })
                                                      .Concat(passwordMd5Hex)
                                                      .ToArray());

            this.a = this.CalculateA(); // A = g ^ a % N
            this.x = this.CalculateX(); // X = H(s, P)
            this.u = this.CalculateU(); // U = H(A, B)
            this.s = this.CalculateS(); // S = (B - (k * g.ModExp(x, N))).ModExp(a + (u * x), N)
            this.k = this.CalculateK();
            this.m = this.CalculateM(); // H(H(N) ^ H(g), H(P), s, A, B, K)
        }

        public BigInteger N
        {
            get
            {
                return this.n;
            }
        }

        public BigInteger G
        {
            get
            {
                return this.g;
            }
        }

        public BigInteger B
        {
            get
            {
                return this.b;
            }
        }

        public BigInteger A
        {
            get
            {
                return this.a;
            }
        }

        public BigInteger X
        {
            get
            {
                return this.x;
            }
        }

        public BigInteger U
        {
            get
            {
                return this.u;
            }
        }

        public BigInteger S
        {
            get
            {
                return this.s;
            }
        }

        public BigInteger K
        {
            get
            {
                return this.k;
            }
        }

        public BigInteger M
        {
            get
            {
                return this.m;
            }
        }

        public byte[] P
        {
            get
            {
                return this.p;
            }
        }

        public BigInteger Salt
        {
            get
            {
                return this.salt;
            }
        }

        public BigInteger SmallA
        {
            get
            {
                return this.smallA;
            }
        }

        public byte[] Account
        {
            get
            {
                return this.account;
            }
        }

        /// <summary>
        /// 计算X: X = H(s, P)
        /// </summary>
        /// <returns></returns>
        private BigInteger CalculateX()
        {
            this.hashAlgorithm.Initialize();
            var joinBytes =
                    new byte[0].Concat(this.Salt.ToUBigIntegerArray()).Concat(this.P).ToArray();
            return this.hashAlgorithm.ComputeHash(joinBytes).ToUBigInteger();
        }

        /// <summary>
        /// 计算A: A = g ^ a % N
        /// </summary>
        /// <returns></returns>
        private BigInteger CalculateA()
        {
            return BigIntegerHelper.UModPow(this.G, this.SmallA, this.N);
        }

        /// <summary>
        /// 计算U: U = H(A, B)
        /// </summary>
        /// <returns></returns>
        private BigInteger CalculateU()
        {
            this.hashAlgorithm.Initialize();

            var joinBytes =
                    new byte[0].Concat(this.A.ToUBigIntegerArray(32))
                            .Concat(this.B.ToUBigIntegerArray(32))
                            .ToArray();
            return this.hashAlgorithm.ComputeHash(joinBytes).ToUBigInteger();
        }

        /// <summary>
        /// 计算S: S = (B - (k * g.ModExp(x, N))).ModExp(a + (u * x), N);
        /// </summary>
        /// <returns></returns>
        private BigInteger CalculateS()
        {
            BigInteger s1 = this.B - BigIntegerHelper.UModPow(this.G, this.X, this.N) * lowerK;
            BigInteger s2 = this.SmallA + (this.U * this.X);
            BigInteger s3 = BigIntegerHelper.UModPow(s1, s2, this.N);
            return s3;
        }

        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        private BigInteger CalculateK()
        {
            this.hashAlgorithm.Initialize();
            byte[] sBytes = this.S.ToUBigIntegerArray();
            int halfLength = sBytes.Length / 2;
            var kBytes = new byte[40];
            var halfS = new byte[halfLength];

            for (int i = 0; i < halfLength; ++i)
            {
                halfS[i] = sBytes[i * 2];
            }
            var p1 = this.hashAlgorithm.ComputeHash(halfS);
            for (int i = 0; i < 20; ++i)
            {
                kBytes[i * 2] = p1[i];
            }

            for (int i = 0; i < halfLength; ++i)
            {
                halfS[i] = sBytes[i * 2 + 1];
            }
            var p2 = this.hashAlgorithm.ComputeHash(halfS);
            for (int i = 0; i < 20; ++i)
            {
                kBytes[i * 2 + 1] = p2[i];
            }

            return kBytes.ToUBigInteger();
        }

        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        private BigInteger CalculateM()
        {
            this.hashAlgorithm.Initialize();
            var hashN = this.hashAlgorithm.ComputeHash(this.N.ToUBigIntegerArray());
            var hashG = this.hashAlgorithm.ComputeHash(this.G.ToUBigIntegerArray());

            // 这里与标准srp6不一样,只异或了20个byte,实际上有32个byte
            for (var i = 0; i < 20; ++i)
            {
                hashN[i] ^= hashG[i];
            }

            var hashGXorhashN = hashN; // H(N) ^ H(g)
            var hashedIdentity = this.hashAlgorithm.ComputeHash(this.Account); // H(I)

            // H(H(N) ^ H(g), H(P), s, A, B, K_c)
            var mBytes =
                    this.hashAlgorithm.ComputeHash(
                                                   new byte[0].Concat(hashGXorhashN)
                                                           .Concat(hashedIdentity)
                                                           .Concat(this.Salt.ToUBigIntegerArray(32))
                                                           .Concat(this.A.ToUBigIntegerArray(32))
                                                           .Concat(this.B.ToUBigIntegerArray(32))
                                                           .Concat(this.K.ToUBigIntegerArray(40))
                                                           .ToArray());
            return mBytes.ToUBigInteger();
        }

        public byte[] CalculateGateDigest(uint clientSeed, uint serverSeed)
        {
            this.hashAlgorithm.Initialize();
            var digest =
                    this.hashAlgorithm.ComputeHash(
                                                   new byte[0].Concat(this.Account)
                                                           .Concat(new byte[4] { 0, 0, 0, 0 })
                                                           .Concat(BitConverter.GetBytes(clientSeed))
                                                           .Concat(BitConverter.GetBytes(serverSeed))
                                                           .Concat(this.k.ToUBigIntegerArray())
                                                           .ToArray());
            return digest;
        }
    }
}