Updated unit test coverage for digest Validate function, as both sha2…

…56 and sha512 digest are registered the library can validate these although the library is limited to compute sha256 digest.

Signed-off-by: Daniel Robinson <daniel.robinson@pebble.tv>

src/OrasProject.Oras/Content/Digest.cs

@@ -13,6 +13,7 @@
 
 using OrasProject.Oras.Exceptions;
 using System;
+using System.Collections.Generic;
 using System.Security.Cryptography;
 using System.Text.RegularExpressions;
 
@@ -23,6 +24,9 @@ internal static class Digest
     private const string _digestRegexPattern = @"[a-z0-9]+(?:[.+_-][a-z0-9]+)*:[a-zA-Z0-9=_-]+";
     private static readonly Regex _digestRegex = new Regex(_digestRegexPattern, RegexOptions.Compiled);
 
+    // List of registered and supported algorithms as per the specification
+    private static readonly HashSet<string> _supportedAlgorithms = new HashSet<string> { "sha256", "sha512" };
+
     /// <summary>
     /// Verifies the digest header and throws an exception if it is invalid.
     /// </summary>
@@ -33,6 +37,13 @@ internal static string Validate(string? digest)
         {
             throw new InvalidDigestException($"Invalid digest: {digest}");
         }
+
+        var algorithm = digest.Split(':')[0];
+        if (!_supportedAlgorithms.Contains(algorithm))
+        {
+            throw new InvalidDigestException($"Unrecognized, unregistered or unsupported digest algorithm: {algorithm}");
+        }
+
         return digest;
     }
 
@@ -48,4 +59,4 @@ internal static string ComputeSHA256(byte[] content)
         var output = $"sha256:{BitConverter.ToString(hash).Replace("-", "")}";
         return output.ToLower();
     }
-}
+}

tests/OrasProject.Oras.Tests/Content/ContentTest.cs

@@ -12,13 +12,15 @@
 // limitations under the License.
 
 using OrasProject.Oras.Content;
+using OrasProject.Oras.Exceptions;
 using System.Text;
 using Xunit;
 
 namespace OrasProject.Oras.Tests.Content;
 
 public class CalculateDigest
 {
+
     /// <summary>
     /// This method tests if the digest is calculated properly
     /// </summary>
@@ -30,4 +32,39 @@ public void VerifiesIfDigestMatches()
         var calculateHelloWorldDigest = Digest.ComputeSHA256(content);
         Assert.Equal(helloWorldDigest, calculateHelloWorldDigest);
     }
+
+    /// <summary>
+    /// This method tests if the digest validation passes for registered algorithms
+    /// </summary>
+    [Theory]
+    [InlineData("sha256:6c3c624b58dbbcd3c0dd82b4c53f04194d1247c6eebdaab7c610cf7d66709b3b")]
+    [InlineData("sha512:401b09eab3c013d4ca54922bb802bec8fd5318192b0a75f201d8b372742c513925d98f76b340d9e59a4efdc45db9f5c640a21831b3d08be")]
+    public void Validate_ReturnsDigest_ForRegisteredAlgorithms(string validDigest)
+    {
+        var result = Digest.Validate(validDigest);
+        Assert.Equal(validDigest, result);
+    }
+
+    /// <summary>
+    /// This method tests if the digest validation throws an exception for unregistered or unsupported algorithms
+    /// </summary>
+    [Theory]
+    [InlineData("md5:098f6bcd4621d373cade4e832627b4f6")] // MD5, unregistered digest
+    [InlineData("sha1:3b8b5a6b79f6d1114a7b7e95b3e3bc74dd1b6a2a")] // SHA-1, unregistered digest
+    [InlineData("multihash+base58:QmRZxt2b1FVZPNqd8hsiykDL3TdBDeTSPX9Kv46HmX4Gx8")] // Multihash, unregistered digest
+    public void Validate_ThrowsException_ForUnregisteredAlgorithms(string invalidDigest)
+    {
+        Assert.Throws<InvalidDigestException>(() => Digest.Validate(invalidDigest));
+    }
+
+    /// <summary>
+    /// This method tests if the digest validation throws an exception for various invalid digest formats
+    /// </summary>
+    [Theory]
+    [InlineData("sha256:")] // Missing encoded portion
+    [InlineData("sha256+b64u!LCa0a2j_xo_5m0U8HTBBNBNCLXBkg7-g-YpeiGJm564")] // Invalid character in encoded portion
+    public void Validate_ThrowsException_ForInvalidDigestFormats(string invalidDigest)
+    {
+        Assert.Throws<InvalidDigestException>(() => Digest.Validate(invalidDigest));
+    }
 }