Initial commit

Security/X509CertChain.cs

@@ -0,0 +1,161 @@
+/*
+ * Secucore
+ * 
+ * Copyright (C) 2023 Trevor Hall
+ * All rights reserved.
+ *
+ * This software may be modified and distributed under the terms
+ * of the MIT license.
+ * 
+ */
+
+using System;
+using System.Collections.Generic;
+
+namespace SecuCore.Security
+{
+    public class X509CertChain
+    {
+        public List<X509Cert> certs;
+
+        public X509CertChain()
+        {
+            certs = new List<X509Cert>();
+        }
+
+        public void AddLink(X509Cert cert)
+        {
+            certs.Add(cert);
+        }
+
+        public bool Verify()
+        {
+            if (certs.Count <= 1) return true;
+
+            for(int i = 0; i < certs.Count; i++)
+            {
+                X509Cert certa = certs[i];
+                X509Cert certb = null;
+                
+                if(i == certs.Count - 1)
+                {
+                    if (HasTrustedRoot(certa, out certb)) {
+                        if(certb == null)
+                        {
+                            //self signed root was already trusted
+                            return true;
+                        }
+                    }
+                    else
+                    {
+                        return false;
+                    }
+                }
+                else
+                {
+                    certb = certs[i + 1];
+                }
+                RSAPublicKey rpkb = certb.GetRSAPublicKey();
+                byte[] decrypted = rpkb.DecryptSignature(certa.signature);
+                byte[] actualhash = Asn1Tools.ParseHash(decrypted);
+                if(Asn1Tools.HashesEqual(certa.certificateHash, actualhash))
+                {
+                    //passed
+                }
+                else
+                {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+
+
+        private bool HasTrustedRoot(X509Cert cert, out X509Cert root)
+        {
+            root = null;
+            string certificateIssuer = cert.issuer.ToString();
+            string certificateSubject = cert.subject.ToString();
+
+            if (certificateIssuer != certificateSubject)
+            {
+                if (!string.IsNullOrEmpty(cert.authorityKeyIdentifier))
+                {
+                    X509Cert trusted = TrustedCA.GetTrustedCertificate(cert.authorityKeyIdentifier);
+                    if (trusted != null)
+                    {
+                        root = trusted;
+                        return true;
+                    }
+                    else
+                    {
+                        return false;
+                    }
+                }
+                else
+                {
+                    return false;
+                }
+            }
+            else
+            {
+                if (!string.IsNullOrEmpty(cert.subjectKeyIdentifier))
+                {
+                    X509Cert trusted = TrustedCA.GetTrustedCertificate(cert.subjectKeyIdentifier);
+                    if (trusted != null)
+                    {
+                        //we trust this
+                        return true;
+                    }
+                    else
+                    {
+                        return false;
+                    }
+                }
+                else
+                {
+                    return false;
+                }
+            }
+        }
+        public static string ToHexString(byte[] input)
+        {
+            char[] outchars = new char[input.Length * 2];
+            int outp = 0;
+            for (int i = 0; i < input.Length; i++)
+            {
+                outchars[outp++] = ToHexChar(input[i] / 16);
+                outchars[outp++] = ToHexChar(input[i] % 16);
+            }
+            return new string(outchars);
+        }
+        private static char ToHexChar(int input)
+        {
+            if (input < 0 || input > 15) throw new Exception("Hex conversion error");
+
+            if (input < 10)
+            {
+                return (char)(48 + input);
+            }
+            else
+            {
+                return (char)(65 + (input - 10));
+            }
+        }
+
+        public void Dispose()
+        {
+
+            if(certs is null)
+            {
+                //do nothing
+            }
+            else
+            {
+                certs.Clear();
+                certs = null;
+            }
+        }
+    }
+}