Fixes for StringCypher

chrisg32 · Apr 27, 2021 · ba60d54 · ba60d54
1 parent e958133
commit ba60d54
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Showing 4 changed files with 45 additions and 13 deletions.
diff --git a/Commons.Test/Commons.Test.csproj b/Commons.Test/Commons.Test.csproj
@@ -11,7 +11,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="FluentAssertions" Version="5.10.0" />
+    <PackageReference Include="FluentAssertions" Version="5.10.3" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.4.0" />
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.1">

diff --git a/Commons.Test/Util/StringCypherTest.cs b/Commons.Test/Util/StringCypherTest.cs
@@ -0,0 +1,26 @@
+using CG.Commons.Util;
+using Xunit;
+using FluentAssertions;
+
+namespace CG.Commons.Test.Util
+{
+    public class StringCypherTest
+    {
+        private const string Passphrase = "1F267C5E-FF0D-4C11-DG23-F0855348D2B8";
+
+        [Fact]
+        public void TestEncryptDecrypt()
+        {
+            //arrange
+            const string testString = "This is a test string. It will be encrypted and decrypted.";
+
+            //act
+            var encrypted = StringCipher.Encrypt(testString, Passphrase);
+            var decrypted = StringCipher.Decrypt(encrypted, Passphrase);
+
+            //assert
+            encrypted.Should().NotBeNullOrEmpty();
+            decrypted.Should().NotBeNullOrEmpty().And.Should().BeEquivalentTo(testString);
+        }
+    }
+}
diff --git a/Commons/Commons.csproj b/Commons/Commons.csproj
@@ -6,7 +6,7 @@
     <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
     <Description>A collection of useful C# utilities, extensions, and data structures.</Description>
     <Authors>Chris Gonzales</Authors>
-    <Version>1.0.8</Version>
+    <Version>1.0.9</Version>
     <PackageTags>Commons C# DataStructures Dictionary Extensions</PackageTags>
     <Copyright>Copyright 2021 Chris Gonzales</Copyright>
     <PackageIconUrl>https://chrisg32.github.io/assets/cg_logo.png</PackageIconUrl>
@@ -19,18 +19,18 @@
     <Product>CG Commons Library</Product>
     <RepositoryType>Git</RepositoryType>
     <RepositoryUrl>https://github.com/chrisg32/Commons</RepositoryUrl>
-    <PackageReleaseNotes>Fix for string Cypher AES bit length.</PackageReleaseNotes>
+    <PackageReleaseNotes>Fix for string Cypher AES broken decryption. WARNING! make break the ability to decrypt strings encrypted with 1.0.7 and below.</PackageReleaseNotes>
     <AssemblyName>CG.Commons</AssemblyName>
     <NeutralLanguage>en-US</NeutralLanguage>
-    <PackageVersion>1.0.8</PackageVersion>
+    <PackageVersion>1.0.9</PackageVersion>
     <Title>Commons</Title>
     <LangVersion>9</LangVersion>
-    <AssemblyVersion>1.0.8</AssemblyVersion>
-    <FileVersion>1.0.8</FileVersion>
+    <AssemblyVersion>1.0.9</AssemblyVersion>
+    <FileVersion>1.0.9</FileVersion>
   </PropertyGroup>
 
   <ItemGroup>
-    <None Include="logo.png" Pack="true" PackagePath=""/>
+    <None Include="logo.png" Pack="true" PackagePath="" />
   </ItemGroup>
 
 </Project>
diff --git a/Commons/Util/StringCipher.cs b/Commons/Util/StringCipher.cs
@@ -11,6 +11,8 @@ public static class StringCipher
         // This constant is used to determine the keysize of the encryption algorithm in bits.
         // We divide this by 8 within the code below to get the equivalent number of bytes.
         private const int Keysize = 256;
+
+        private const int BlockSize = 128;
 
         // This constant determines the number of iterations for the password bytes generation function.
         private const int DerivationIterations = 1000;
@@ -29,7 +31,7 @@ public static string Encrypt(string plainText, string passPhrase)
                 using (var symmetricKey = Aes.Create())
                 {
                     //https://stackoverflow.com/questions/9300340/got-error-specified-block-size-is-not-valid-for-this-algorithm-while-initiali
-                    symmetricKey.BlockSize = 128;
+                    symmetricKey.BlockSize = BlockSize;
                     symmetricKey.Mode = CipherMode.CBC;
                     symmetricKey.Padding = PaddingMode.PKCS7;
                     using (var encryptor = symmetricKey.CreateEncryptor(keyBytes, ivStringBytes))
@@ -55,22 +57,26 @@ public static string Encrypt(string plainText, string passPhrase)
         public static string Decrypt(string cipherText, string passPhrase)
         {
             if (cipherText == null) return null;
+
+            var saltLength = Keysize / 8;
+            var ivLength = BlockSize / 8;
+
             // Get the complete stream of bytes that represent:
             // [32 bytes of Salt] + [32 bytes of IV] + [n bytes of CipherText]
             var cipherTextBytesWithSaltAndIv = Convert.FromBase64String(cipherText);
             // Get the saltbytes by extracting the first 32 bytes from the supplied cipherText bytes.
-            var saltStringBytes = cipherTextBytesWithSaltAndIv.Take(Keysize / 8).ToArray();
-            // Get the IV bytes by extracting the next 32 bytes from the supplied cipherText bytes.
-            var ivStringBytes = cipherTextBytesWithSaltAndIv.Skip(Keysize / 8).Take(Keysize / 8).ToArray();
+            var saltStringBytes = cipherTextBytesWithSaltAndIv.Take(saltLength).ToArray();
+            // Get the IV bytes by extracting the next 16 bytes from the supplied cipherText bytes.
+            var ivStringBytes = cipherTextBytesWithSaltAndIv.Skip(saltLength).Take(ivLength).ToArray();
             // Get the actual cipher text bytes by removing the first 64 bytes from the cipherText string.
-            var cipherTextBytes = cipherTextBytesWithSaltAndIv.Skip((Keysize / 8) * 2).Take(cipherTextBytesWithSaltAndIv.Length - ((Keysize / 8) * 2)).ToArray();
+            var cipherTextBytes = cipherTextBytesWithSaltAndIv.Skip(saltLength + ivLength).Take(cipherTextBytesWithSaltAndIv.Length - (saltLength + ivLength)).ToArray();
 
             using (var password = new Rfc2898DeriveBytes(passPhrase, saltStringBytes, DerivationIterations))
             {
                 var keyBytes = password.GetBytes(Keysize / 8);
                 using (var symmetricKey = Aes.Create())
                 {
-                    symmetricKey.BlockSize = 256;
+                    symmetricKey.BlockSize = BlockSize;
                     symmetricKey.Mode = CipherMode.CBC;
                     symmetricKey.Padding = PaddingMode.PKCS7;
                     using (var decryptor = symmetricKey.CreateDecryptor(keyBytes, ivStringBytes))