From ac769e656b122ff569c3f1534701b71e00fed586 Mon Sep 17 00:00:00 2001
From: crupest <crupest@outlook.com>
Date: Tue, 27 Oct 2020 19:21:35 +0800
Subject: Split front and back end.

---
 BackEnd/Timeline/Services/UserTokenService.cs | 149 ++++++++++++++++++++++++++
 1 file changed, 149 insertions(+)
 create mode 100644 BackEnd/Timeline/Services/UserTokenService.cs

(limited to 'BackEnd/Timeline/Services/UserTokenService.cs')

diff --git a/BackEnd/Timeline/Services/UserTokenService.cs b/BackEnd/Timeline/Services/UserTokenService.cs
new file mode 100644
index 00000000..86f3a0f7
--- /dev/null
+++ b/BackEnd/Timeline/Services/UserTokenService.cs
@@ -0,0 +1,149 @@
+using Microsoft.Extensions.Options;
+using Microsoft.IdentityModel.Tokens;
+using System;
+using System.Globalization;
+using System.IdentityModel.Tokens.Jwt;
+using System.Linq;
+using System.Security.Claims;
+using Timeline.Configs;
+using Timeline.Entities;
+
+namespace Timeline.Services
+{
+    public class UserTokenInfo
+    {
+        public long Id { get; set; }
+        public long Version { get; set; }
+        public DateTime? ExpireAt { get; set; }
+    }
+
+    public interface IUserTokenService
+    {
+        /// <summary>
+        /// Create a token for a given token info.
+        /// </summary>
+        /// <param name="tokenInfo">The info to generate token.</param>
+        /// <returns>Return the generated token.</returns>
+        /// <exception cref="ArgumentNullException">Thrown when <paramref name="tokenInfo"/> is null.</exception>
+        string GenerateToken(UserTokenInfo tokenInfo);
+
+        /// <summary>
+        /// Verify a token and get the saved info.
+        /// </summary>
+        /// <param name="token">The token to verify.</param>
+        /// <returns>The saved info in token.</returns>
+        /// <exception cref="ArgumentNullException">Thrown when <paramref name="token"/> is null.</exception>
+        /// <exception cref="UserTokenBadFormatException">Thrown when the token is of bad format.</exception>
+        /// <remarks>
+        /// If this method throw <see cref="UserTokenBadFormatException"/>, it usually means the token is not created by this service.
+        /// </remarks>
+        UserTokenInfo VerifyToken(string token);
+    }
+
+    public class JwtUserTokenService : IUserTokenService
+    {
+        private const string VersionClaimType = "timeline_version";
+
+        private readonly IOptionsMonitor<JwtConfiguration> _jwtConfig;
+        private readonly IClock _clock;
+
+        private readonly JwtSecurityTokenHandler _tokenHandler = new JwtSecurityTokenHandler();
+        private SymmetricSecurityKey _tokenSecurityKey;
+
+        public JwtUserTokenService(IOptionsMonitor<JwtConfiguration> jwtConfig, IClock clock, DatabaseContext database)
+        {
+            _jwtConfig = jwtConfig;
+            _clock = clock;
+
+            var key = database.JwtToken.Select(t => t.Key).SingleOrDefault();
+
+            if (key == null)
+            {
+                throw new InvalidOperationException(Resources.Services.UserTokenService.JwtKeyNotExist);
+            }
+
+            _tokenSecurityKey = new SymmetricSecurityKey(key);
+        }
+
+        public string GenerateToken(UserTokenInfo tokenInfo)
+        {
+            if (tokenInfo == null)
+                throw new ArgumentNullException(nameof(tokenInfo));
+
+            var config = _jwtConfig.CurrentValue;
+
+            var identity = new ClaimsIdentity();
+            identity.AddClaim(new Claim(ClaimTypes.NameIdentifier, tokenInfo.Id.ToString(CultureInfo.InvariantCulture.NumberFormat), ClaimValueTypes.Integer64));
+            identity.AddClaim(new Claim(VersionClaimType, tokenInfo.Version.ToString(CultureInfo.InvariantCulture.NumberFormat), ClaimValueTypes.Integer64));
+
+            var tokenDescriptor = new SecurityTokenDescriptor()
+            {
+                Subject = identity,
+                Issuer = config.Issuer,
+                Audience = config.Audience,
+                SigningCredentials = new SigningCredentials(_tokenSecurityKey, SecurityAlgorithms.HmacSha384),
+                IssuedAt = _clock.GetCurrentTime(),
+                Expires = tokenInfo.ExpireAt.GetValueOrDefault(_clock.GetCurrentTime().AddSeconds(config.DefaultExpireOffset)),
+                NotBefore = _clock.GetCurrentTime() // I must explicitly set this or it will use the current time by default and mock is not work in which case test will not pass.
+            };
+
+            var token = _tokenHandler.CreateToken(tokenDescriptor);
+            var tokenString = _tokenHandler.WriteToken(token);
+
+            return tokenString;
+        }
+
+
+        public UserTokenInfo VerifyToken(string token)
+        {
+            if (token == null)
+                throw new ArgumentNullException(nameof(token));
+
+            var config = _jwtConfig.CurrentValue;
+            try
+            {
+                var principal = _tokenHandler.ValidateToken(token, new TokenValidationParameters
+                {
+                    ValidateIssuer = true,
+                    ValidateAudience = true,
+                    ValidateIssuerSigningKey = true,
+                    ValidateLifetime = false,
+                    ValidIssuer = config.Issuer,
+                    ValidAudience = config.Audience,
+                    IssuerSigningKey = _tokenSecurityKey
+                }, out var t);
+
+                var idClaim = principal.FindFirstValue(ClaimTypes.NameIdentifier);
+                if (idClaim == null)
+                    throw new JwtUserTokenBadFormatException(token, JwtUserTokenBadFormatException.ErrorKind.NoIdClaim);
+                if (!long.TryParse(idClaim, out var id))
+                    throw new JwtUserTokenBadFormatException(token, JwtUserTokenBadFormatException.ErrorKind.IdClaimBadFormat);
+
+                var versionClaim = principal.FindFirstValue(VersionClaimType);
+                if (versionClaim == null)
+                    throw new JwtUserTokenBadFormatException(token, JwtUserTokenBadFormatException.ErrorKind.NoVersionClaim);
+                if (!long.TryParse(versionClaim, out var version))
+                    throw new JwtUserTokenBadFormatException(token, JwtUserTokenBadFormatException.ErrorKind.VersionClaimBadFormat);
+
+                var decodedToken = (JwtSecurityToken)t;
+                var exp = decodedToken.Payload.Exp;
+                DateTime? expireAt = null;
+                if (exp.HasValue)
+                {
+                    expireAt = EpochTime.DateTime(exp.Value);
+                }
+
+                return new UserTokenInfo
+                {
+                    Id = id,
+                    Version = version,
+                    ExpireAt = expireAt
+                };
+            }
+            catch (Exception e) when (e is SecurityTokenException || e is ArgumentException)
+            {
+                throw new JwtUserTokenBadFormatException(token, JwtUserTokenBadFormatException.ErrorKind.Other, e);
+            }
+        }
+    }
+}
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