1 files changed, 105 insertions, 0 deletions
diff --git a/crypto/src/asn1/cms/CmsAlgorithmProtection.cs b/crypto/src/asn1/cms/CmsAlgorithmProtection.cs
new file mode 100644
index 000000000..9d21e53ff
--- /dev/null
+++ b/crypto/src/asn1/cms/CmsAlgorithmProtection.cs
@@ -0,0 +1,105 @@
+using System;
+
+using Org.BouncyCastle.Asn1.X509;
+
+namespace Org.BouncyCastle.Asn1.Cms
+{
+
+    /**
+     * From RFC 6211
+     * <pre>
+     * CMSAlgorithmProtection ::= SEQUENCE {
+     *    digestAlgorithm         DigestAlgorithmIdentifier,
+     *    signatureAlgorithm  [1] SignatureAlgorithmIdentifier OPTIONAL,
+     *    macAlgorithm        [2] MessageAuthenticationCodeAlgorithm
+     *                                     OPTIONAL
+     * }
+     * (WITH COMPONENTS { signatureAlgorithm PRESENT,
+     *                    macAlgorithm ABSENT } |
+     *  WITH COMPONENTS { signatureAlgorithm ABSENT,
+     *                    macAlgorithm PRESENT })
+     * </pre>
+     */
+    public class CmsAlgorithmProtection
+        : Asn1Encodable
+    {
+        public static readonly int Signature = 1;
+        public static readonly int Mac = 2;
+
+        private readonly AlgorithmIdentifier digestAlgorithm;
+        private readonly AlgorithmIdentifier signatureAlgorithm;
+        private readonly AlgorithmIdentifier macAlgorithm;
+
+        public CmsAlgorithmProtection(AlgorithmIdentifier digestAlgorithm, int type, AlgorithmIdentifier algorithmIdentifier)
+        {
+            if (digestAlgorithm == null || algorithmIdentifier == null)
+                throw new ArgumentException("AlgorithmIdentifiers cannot be null");
+
+            this.digestAlgorithm = digestAlgorithm;
+
+            if (type == 1)
+            {
+                this.signatureAlgorithm = algorithmIdentifier;
+                this.macAlgorithm = null;
+            }
+            else if (type == 2)
+            {
+                this.signatureAlgorithm = null;
+                this.macAlgorithm = algorithmIdentifier;
+            }
+            else
+            {
+                throw new ArgumentException("Unknown type: " + type);
+            }
+        }
+
+        private CmsAlgorithmProtection(Asn1Sequence sequence)
+        {
+            if (sequence.Count != 2)
+                throw new ArgumentException("Sequence wrong size: One of signatureAlgorithm or macAlgorithm must be present");
+
+            this.digestAlgorithm = AlgorithmIdentifier.GetInstance(sequence[0]);
+
+            Asn1TaggedObject tagged = Asn1TaggedObject.GetInstance(sequence[1]);
+            if (tagged.TagNo == 1)
+            {
+                this.signatureAlgorithm = AlgorithmIdentifier.GetInstance(tagged, false);
+                this.macAlgorithm = null;
+            }
+            else if (tagged.TagNo == 2)
+            {
+                this.signatureAlgorithm = null;
+
+                this.macAlgorithm = AlgorithmIdentifier.GetInstance(tagged, false);
+            }
+            else
+            {
+                throw new ArgumentException("Unknown tag found: " + tagged.TagNo);
+            }
+        }
+
+        public static CmsAlgorithmProtection GetInstance(object obj)
+        {
+            if (obj == null)
+                return null;
+            if (obj is CmsAlgorithmProtection cmsAlgorithmProtection)
+                return cmsAlgorithmProtection;
+            return new CmsAlgorithmProtection(Asn1Sequence.GetInstance(obj));
+        }
+
+        public AlgorithmIdentifier DigestAlgorithm => digestAlgorithm;
+
+        public AlgorithmIdentifier MacAlgorithm => macAlgorithm;
+
+        public AlgorithmIdentifier SignatureAlgorithm => signatureAlgorithm;
+
+        public override Asn1Object ToAsn1Object()
+        {
+            Asn1EncodableVector v = new Asn1EncodableVector(3);
+            v.Add(digestAlgorithm);
+            v.AddOptionalTagged(false, 1, signatureAlgorithm);
+            v.AddOptionalTagged(false, 2, macAlgorithm);
+            return new DerSequence(v);
+        }
+    }
+}