Add validation to bot tokens based on string length (#1128)

* Add input validation for bot tokens based on their length

* Add token validation to BaseDiscordClient#LoginAsync

Adds a TokenUtils class which is used to validate that tokens are correct

* Revert changes to DiscordRestApiClient

* Add Unit tests to the TokenUtils class, fix a logic error that was caught by those tests

* Allow for API to throw exceptions

Moves the validation of tokens to be inside of LoginInternalAsync, and writes a Warning to the console when the supplied tokens are invalid

test/Discord.Net.Tests/Tests.TokenUtils.cs

@@ -0,0 +1,124 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Xunit;
+
+namespace Discord
+{
+    public class TokenUtilsTests
+    {
+        /// <summary>
+        ///     Tests the usage of <see cref="TokenUtils.ValidateToken(TokenType, string)"/>
+        ///     to see that when a null, empty or whitespace-only string is passed as the token,
+        ///     it will throw an ArgumentNullException.
+        /// </summary>
+        [Theory]
+        [InlineData(null)]
+        [InlineData("")] // string.Empty isn't a constant type
+        [InlineData(" ")]
+        [InlineData("    ")]
+        [InlineData("\t")]
+        public void TestNullOrWhitespaceToken(string token)
+        {
+            // an ArgumentNullException should be thrown, regardless of the TokenType
+            Assert.Throws<ArgumentNullException>(() => TokenUtils.ValidateToken(TokenType.Bearer, token));
+            Assert.Throws<ArgumentNullException>(() => TokenUtils.ValidateToken(TokenType.Bot, token));
+            Assert.Throws<ArgumentNullException>(() => TokenUtils.ValidateToken(TokenType.Webhook, token));
+        }
+        
+        /// <summary>
+        ///     Tests the behavior of <see cref="TokenUtils.ValidateToken(TokenType, string)"/>
+        ///     to see that valid Webhook tokens do not throw Exceptions.
+        /// </summary>
+        /// <param name="token"></param>
+        [Theory]
+        [InlineData("123123123")]
+        // bot token
+        [InlineData("MTk4NjIyNDgzNDcxOTI1MjQ4.Cl2FMQ.ZnCjm1XVW7vRze4b7Cq4se7kKWs")]
+        // bearer token taken from discord docs
+        [InlineData("6qrZcUqja7812RVdnEKjpzOL4CvHBFG")]
+        // client secret
+        [InlineData("937it3ow87i4ery69876wqire")]
+        public void TestWebhookTokenDoesNotThrowExceptions(string token)
+        {
+            TokenUtils.ValidateToken(TokenType.Webhook, token);
+        }
+
+        // No tests for invalid webhook token behavior, because there is nothing there yet.
+
+        /// <summary>
+        ///     Tests the behavior of <see cref="TokenUtils.ValidateToken(TokenType, string)"/>
+        ///     to see that valid Webhook tokens do not throw Exceptions.
+        /// </summary>
+        /// <param name="token"></param>
+        [Theory]
+        [InlineData("123123123")]
+        // bot token
+        [InlineData("MTk4NjIyNDgzNDcxOTI1MjQ4.Cl2FMQ.ZnCjm1XVW7vRze4b7Cq4se7kKWs")]
+        // bearer token taken from discord docs
+        [InlineData("6qrZcUqja7812RVdnEKjpzOL4CvHBFG")]
+        // client secret
+        [InlineData("937it3ow87i4ery69876wqire")]
+        public void TestBearerTokenDoesNotThrowExceptions(string token)
+        {
+            TokenUtils.ValidateToken(TokenType.Bearer, token);
+        }
+
+        // No tests for invalid bearer token behavior, because there is nothing there yet.
+
+        /// <summary>
+        ///     Tests the behavior of <see cref="TokenUtils.ValidateToken(TokenType, string)"/>
+        ///     to see that valid Bot tokens do not throw Exceptions.
+        ///     Valid Bot tokens can be strings of length 59 or above.
+        /// </summary>
+        [Theory]
+        [InlineData("MTk4NjIyNDgzNDcxOTI1MjQ4.Cl2FMQ.ZnCjm1XVW7vRze4b7Cq4se7kKWs")]
+        [InlineData("This appears to be completely invalid, however the current validation rules are not very strict.")]
+        [InlineData("MTk4NjIyNDgzNDcxOTI1MjQ4.Cl2FMQ.ZnCjm1XVW7vRze4b7Cq4se7kKWss")]
+        [InlineData("MTk4NjIyNDgzNDcxOTI1MjQ4.Cl2FMQ.ZnCjm1XVW7vRze4b7Cq4se7kKWsMTk4NjIyNDgzNDcxOTI1MjQ4.Cl2FMQ.ZnCjm1XVW7vRze4b7Cq4se7kKWs")]
+        public void TestBotTokenDoesNotThrowExceptions(string token)
+        {
+            // This example token is pulled from the Discord Docs
+            // https://discordapp.com/developers/docs/reference#authentication-example-bot-token-authorization-header
+            // should not throw any exception
+            TokenUtils.ValidateToken(TokenType.Bot, token);
+        }
+
+        /// <summary>
+        ///     Tests the usage of <see cref="TokenUtils.ValidateToken(TokenType, string)"/> with
+        ///     a Bot token that is invalid.
+        /// </summary>
+        [Theory]
+        [InlineData("This is invalid")]
+        // missing a single character from the end
+        [InlineData("MTk4NjIyNDgzNDcxOTI1MjQ4.Cl2FMQ.ZnCjm1XVW7vRze4b7Cq4se7kKW")]
+        // bearer token
+        [InlineData("6qrZcUqja7812RVdnEKjpzOL4CvHBFG")]
+        // client secret
+        [InlineData("937it3ow87i4ery69876wqire")]
+        public void TestBotTokenInvalidThrowsArgumentException(string token)
+        {
+            Assert.Throws<ArgumentException>(() => TokenUtils.ValidateToken(TokenType.Bot, token));
+        }
+
+        /// <summary>
+        ///     Tests the behavior of <see cref="TokenUtils.ValidateToken(TokenType, string)"/>
+        ///     to see that an <see cref="ArgumentException"/> is thrown when an invalid
+        ///     <see cref="TokenType"/> is supplied as a parameter.
+        /// </summary>
+        /// <remarks>
+        ///     The <see cref="TokenType.User"/> type is treated as an invalid <see cref="TokenType"/>.
+        /// </remarks>
+        [Theory]
+        // TokenType.User
+        [InlineData(0)]
+        // out of range TokenType
+        [InlineData(4)]
+        [InlineData(7)]
+        public void TestUnrecognizedTokenType(int type)
+        {
+            Assert.Throws<ArgumentException>(() =>
+                TokenUtils.ValidateToken((TokenType)type, "MTk4NjIyNDgzNDcxOTI1MjQ4.Cl2FMQ.ZnCjm1XVW7vRze4b7Cq4se7kKWs"));
+        }
+    }
+}