Geary.RFC822.Message: Add support for Authentication-Results field

src/engine/rfc822/rfc822-message-data.vala

@@ -619,3 +619,25 @@ public class Geary.RFC822.PreviewText : Geary.RFC822.Text {
     }
 
 }
+
+public class Geary.RFC822.AuthenticationResults :
+    Geary.MessageData.StringMessageData {
+
+    public AuthenticationResults(string value) {
+        base(value);
+    }
+
+    /**
+     * Returns the authentication result for dkim.
+     */
+    public bool is_dkim_valid() {
+        return /^.*;[ ]*dkim=pass.*$/i.match(this.value);
+    }
+
+     /**
+     * Returns the authentication result for dmarc.
+     */
+    public bool is_dmarc_valid() {
+        return /^.*;[ ]*dmarc=pass.*$/i.match(this.value);
+    }
+}

src/engine/rfc822/rfc822-message.vala

@@ -36,6 +36,11 @@ public class Geary.RFC822.Message : BaseObject, EmailHeaderSet {
     private const string HEADER_REFERENCES = "References";
     private const string HEADER_MAILER = "X-Mailer";
     private const string HEADER_BCC = "Bcc";
+    private const string[] HEADER_AUTH_RESULTS = {
+        "ARC-Authentication-Results",
+        "Authentication-Results",
+        "X-Original-Authentication-Results"
+    };
 
     /** Options to use when serialising a message in RFC 822 format. */
     [Flags]
@@ -108,6 +113,14 @@ public class Geary.RFC822.Message : BaseObject, EmailHeaderSet {
     public Date? date { get { return this._date; } }
     private Date? _date = null;
 
+    /**
+     * {@inheritDoc}
+     *
+     * Value will be valid if {@link Field.AUTH_RESULTS} is set.
+     */
+    public RFC822.AuthenticationResults? auth_results { get { return this._auth_results; } }
+    private RFC822.AuthenticationResults? _auth_results = null;
+
     /** Value of the X-Mailer header. */
     public string? mailer { get; protected set; default = null; }
 
@@ -160,6 +173,14 @@ public class Geary.RFC822.Message : BaseObject, EmailHeaderSet {
             this._message_id = new MessageID(message_id);
         }
 
+        foreach (string field in HEADER_AUTH_RESULTS) {
+            var auth_results = message.get_header(field);
+            if (auth_results != null) {
+                this._auth_results = new AuthenticationResults(auth_results);
+                break;
+            }
+        }
+
         // Since these headers may be specified multiple times, we
         // need to iterate over all of them to find them.
         var headers = message.get_header_list();