Resolve ILLink warnings in System.Security.Cryptography.Csp

src/libraries/System.Security.Cryptography.Csp/ref/System.Security.Cryptography.Csp.cs

@@ -144,13 +144,17 @@ public partial class PasswordDeriveBytes : System.Security.Cryptography.DeriveBy
     {
         public PasswordDeriveBytes(byte[] password, byte[]? salt) { }
         public PasswordDeriveBytes(byte[] password, byte[]? salt, System.Security.Cryptography.CspParameters? cspParams) { }
+        [System.Diagnostics.CodeAnalysis.RequiresUnreferencedCodeAttribute("The hash implementation might be removed. Ensure the referenced hash algorithm is not trimmed.")]
         public PasswordDeriveBytes(byte[] password, byte[]? salt, string hashName, int iterations) { }
+        [System.Diagnostics.CodeAnalysis.RequiresUnreferencedCodeAttribute("The hash implementation might be removed. Ensure the referenced hash algorithm is not trimmed.")]
         public PasswordDeriveBytes(byte[] password, byte[]? salt, string hashName, int iterations, System.Security.Cryptography.CspParameters? cspParams) { }
         public PasswordDeriveBytes(string strPassword, byte[]? rgbSalt) { }
         public PasswordDeriveBytes(string strPassword, byte[]? rgbSalt, System.Security.Cryptography.CspParameters? cspParams) { }
+        [System.Diagnostics.CodeAnalysis.RequiresUnreferencedCodeAttribute("The hash implementation might be removed. Ensure the referenced hash algorithm is not trimmed.")]
         public PasswordDeriveBytes(string strPassword, byte[]? rgbSalt, string strHashName, int iterations) { }
+        [System.Diagnostics.CodeAnalysis.RequiresUnreferencedCodeAttribute("The hash implementation might be removed. Ensure the referenced hash algorithm is not trimmed.")]
         public PasswordDeriveBytes(string strPassword, byte[]? rgbSalt, string strHashName, int iterations, System.Security.Cryptography.CspParameters? cspParams) { }
-        public string HashName { get { throw null; } set { } }
+        public string HashName { get { throw null; } [System.Diagnostics.CodeAnalysis.RequiresUnreferencedCodeAttribute("The hash implementation might be removed. Ensure the referenced hash algorithm is not trimmed.")] set { } }
         public int IterationCount { get { throw null; } set { } }
         public byte[]? Salt { get { throw null; } set { } }
         [System.Runtime.Versioning.SupportedOSPlatformAttribute("windows")]

src/libraries/System.Security.Cryptography.Csp/src/System/Security/Cryptography/PasswordDeriveBytes.cs

@@ -14,6 +14,8 @@ namespace System.Security.Cryptography
     [EditorBrowsable(EditorBrowsableState.Never)]
     public partial class PasswordDeriveBytes : DeriveBytes
     {
+        private const string HashAlgorithmUnreferencedCodeMessage = "The hash implementation might be removed. Ensure the referenced hash algorithm is not trimmed.";
+
         private int _extraCount;
         private int _prefix;
         private int _iterations;
@@ -30,22 +32,30 @@ public partial class PasswordDeriveBytes : DeriveBytes
 
         public PasswordDeriveBytes(byte[] password, byte[]? salt) : this(password, salt, new CspParameters()) { }
 
+        [RequiresUnreferencedCode(HashAlgorithmUnreferencedCodeMessage)]
         public PasswordDeriveBytes(string strPassword, byte[]? rgbSalt, string strHashName, int iterations) :
             this(strPassword, rgbSalt, strHashName, iterations, new CspParameters()) { }
 
+        [RequiresUnreferencedCode(HashAlgorithmUnreferencedCodeMessage)]
         public PasswordDeriveBytes(byte[] password, byte[]? salt, string hashName, int iterations) :
             this(password, salt, hashName, iterations, new CspParameters()) { }
 #pragma warning restore CA1416
 
+        [UnconditionalSuppressMessage("ReflectionAnalysis", "IL2026:RequiresUnreferencedCode", Justification = "The correct hash algorithm is being preserved by the DynamicDependency.")]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor, typeof(SHA1CryptoServiceProvider))]
         public PasswordDeriveBytes(string strPassword, byte[]? rgbSalt, CspParameters? cspParams) :
             this(strPassword, rgbSalt, "SHA1", 100, cspParams) { }
 
+        [UnconditionalSuppressMessage("ReflectionAnalysis", "IL2026:RequiresUnreferencedCode", Justification = "The correct hash algorithm is being preserved by the DynamicDependency.")]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor, typeof(SHA1CryptoServiceProvider))]
         public PasswordDeriveBytes(byte[] password, byte[]? salt, CspParameters? cspParams) :
             this(password, salt, "SHA1", 100, cspParams) { }
 
+        [RequiresUnreferencedCode(HashAlgorithmUnreferencedCodeMessage)]
         public PasswordDeriveBytes(string strPassword, byte[]? rgbSalt, string strHashName, int iterations, CspParameters? cspParams) :
             this((new UTF8Encoding(false)).GetBytes(strPassword), rgbSalt, strHashName, iterations, cspParams) { }
 
+        [RequiresUnreferencedCode(HashAlgorithmUnreferencedCodeMessage)]
         public PasswordDeriveBytes(byte[] password, byte[]? salt, string hashName, int iterations, CspParameters? cspParams)
         {
             IterationCount = iterations;
@@ -58,6 +68,7 @@ public PasswordDeriveBytes(byte[] password, byte[]? salt, string hashName, int i
         public string HashName
         {
             get { return _hashName!; }
+            [RequiresUnreferencedCode(HashAlgorithmUnreferencedCodeMessage)]
             set
             {
                 if (_baseValue != null)

src/libraries/System.Security.Cryptography.Csp/tests/TrimmingTests/PasswordDeriveBytesTest.cs

@@ -0,0 +1,43 @@
+using System;
+using System.Globalization;
+using System.Linq;
+using System.Security.Cryptography;
+
+/// <summary>
+/// Tests that using PasswordDeriveBytes without specifying a hash algorithm name
+/// works correctly in a trimmed application.
+/// </summary>
+class Program
+{
+    static int Main()
+    {
+        string testPassword = "PasswordGoesHere";
+        byte[] testSalt = new byte[] { 9, 5, 5, 5, 1, 2, 1, 2 };
+
+        byte[] expected = HexToByteArray("12F2497EC3EB78B0EA32AABFD8B9515FBC800BEEB6316A4DDF4EA62518341488A116DA3BBC26C685");
+
+        using (var deriveBytes = new PasswordDeriveBytes(testPassword, testSalt))
+        {
+            byte[] output = deriveBytes.GetBytes(expected.Length);
+            if (output.SequenceEqual(expected))
+            {
+                return 100;
+            }
+        }
+
+        return -1;
+    }
+
+    private static byte[] HexToByteArray(string hexString)
+    {
+        byte[] bytes = new byte[hexString.Length / 2];
+
+        for (int i = 0; i < hexString.Length; i += 2)
+        {
+            ReadOnlySpan<char> s = hexString.AsSpan(i, 2);
+            bytes[i / 2] = byte.Parse(s, NumberStyles.HexNumber, null);
+        }
+
+        return bytes;
+    }
+}

src/libraries/System.Security.Cryptography.Csp/tests/TrimmingTests/System.Security.Cryptography.Csp.TrimmingTests.proj

@@ -0,0 +1,9 @@
+<Project DefaultTargets="Build">
+  <Import Project="$([MSBuild]::GetPathOfFileAbove(Directory.Build.props))" />
+
+  <ItemGroup>
+    <TestConsoleAppSourceFiles Include="PasswordDeriveBytesTest.cs" />
+  </ItemGroup>
+
+  <Import Project="$([MSBuild]::GetPathOfFileAbove(Directory.Build.targets))" />
+</Project>