Handle "cid:" URIs in HTML message body

k9mail-library/src/main/java/com/fsck/k9/mail/Part.java

@@ -20,7 +20,7 @@ public interface Part {
 
     String getDisposition() throws MessagingException;
 
-    String getContentId() throws MessagingException;
+    String getContentId();
 
     String[] getHeader(String name) throws MessagingException;
 

k9mail-library/src/main/java/com/fsck/k9/mail/internet/MimeBodyPart.java

@@ -96,7 +96,7 @@ public class MimeBodyPart extends BodyPart {
     }
 
     @Override
-    public String getContentId() throws MessagingException {
+    public String getContentId() {
         String contentId = getFirstHeader(MimeHeader.HEADER_CONTENT_ID);
         if (contentId == null) {
             return null;

k9mail-library/src/main/java/com/fsck/k9/mail/internet/MimeMessage.java

@@ -174,7 +174,7 @@ public class MimeMessage extends Message {
     }
 
     @Override
-    public String getContentId() throws MessagingException {
+    public String getContentId() {
         return null;
     }
 

k9mail/src/main/java/com/fsck/k9/mailstore/LocalMessageExtractor.java

@@ -518,7 +518,7 @@ public class LocalMessageExtractor {
         return attachments;
     }
 
-    private static AttachmentViewInfo extractAttachmentInfo(Context context, Part part) throws MessagingException {
+    public static AttachmentViewInfo extractAttachmentInfo(Context context, Part part) throws MessagingException {
         if (part instanceof LocalPart) {
             LocalPart localPart = (LocalPart) part;
             String accountUuid = localPart.getAccountUuid();

k9mail/src/main/java/com/fsck/k9/ui/messageview/MessageContainerView.java

@@ -26,6 +26,7 @@ import android.view.View.OnCreateContextMenuListener;
 import android.view.ViewStub;
 import android.webkit.WebView;
 import android.webkit.WebView.HitTestResult;
+import android.webkit.WebViewClient;
 import android.widget.Button;
 import android.widget.LinearLayout;
 import android.widget.Toast;
@@ -34,10 +35,12 @@ import com.fsck.k9.R;
 import com.fsck.k9.helper.ClipboardManager;
 import com.fsck.k9.helper.Contacts;
 import com.fsck.k9.mail.Address;
+import com.fsck.k9.mail.Message;
 import com.fsck.k9.mail.MessagingException;
 import com.fsck.k9.mailstore.AttachmentViewInfo;
 import com.fsck.k9.mailstore.MessageViewInfo.MessageViewContainer;
 
+import com.fsck.k9.view.K9WebViewClient;
 import com.fsck.k9.view.MessageHeader.OnLayoutChangedListener;
 import com.fsck.k9.view.MessageWebView;
 import org.openintents.openpgp.OpenPgpError;
@@ -421,10 +424,13 @@ public class MessageContainerView extends LinearLayout implements OnClickListene
         }
     }
 
-    public void setMessage(MessageViewContainer messageViewContainer)
+    public void setMessageViewContainer(Message message, MessageViewContainer messageViewContainer)
             throws MessagingException {
         resetView();
 
+        WebViewClient webViewClient = K9WebViewClient.newInstance(message);
+        mMessageContentView.setWebViewClient(webViewClient);
+
         // Save the text so we can reset the WebView when the user clicks the "Show pictures" button
         OpenPgpError error = messageViewContainer.pgpError;
         if (error != null) {

k9mail/src/main/java/com/fsck/k9/ui/messageview/MessageTopView.java

@@ -1,6 +1,5 @@
 package com.fsck.k9.ui.messageview;
 
-import android.app.Activity;
 import android.app.Fragment;
 import android.content.Context;
 import android.util.AttributeSet;
@@ -14,7 +13,6 @@ import android.widget.LinearLayout;
 import com.fsck.k9.Account;
 import com.fsck.k9.K9;
 import com.fsck.k9.R;
-import com.fsck.k9.crypto.PgpData;
 import com.fsck.k9.mail.Flag;
 import com.fsck.k9.mail.Message;
 import com.fsck.k9.mail.MessagingException;
@@ -67,11 +65,13 @@ public class MessageTopView extends LinearLayout {
             throws MessagingException {
         resetView();
 
+        Message message = messageViewInfo.message;
         for (MessageViewContainer container : messageViewInfo.containers) {
             MessageContainerView view = (MessageContainerView) mInflater.inflate(R.layout.message_container, null);
             view.initialize(fragment, attachmentCallback, openPgpHeaderViewCallback,
                     !Account.NO_OPENPGP_PROVIDER.equals(account.getOpenPgpProvider()));
-            view.setMessage(container);
+            view.setMessageViewContainer(message, container);
+
             containerViews.addView(view);
         }
 

k9mail/src/main/java/com/fsck/k9/view/K9WebViewClient.java

@@ -0,0 +1,126 @@
+package com.fsck.k9.view;
+
+
+import java.io.InputStream;
+import java.util.Stack;
+
+import android.annotation.TargetApi;
+import android.content.ContentResolver;
+import android.content.Context;
+import android.net.Uri;
+import android.os.Build;
+import android.os.Build.VERSION_CODES;
+import android.text.TextUtils;
+import android.util.Log;
+import android.webkit.WebResourceRequest;
+import android.webkit.WebResourceResponse;
+import android.webkit.WebView;
+import android.webkit.WebViewClient;
+
+import com.fsck.k9.K9;
+import com.fsck.k9.mail.Body;
+import com.fsck.k9.mail.Message;
+import com.fsck.k9.mail.Multipart;
+import com.fsck.k9.mail.Part;
+import com.fsck.k9.mailstore.AttachmentViewInfo;
+import com.fsck.k9.mailstore.LocalMessageExtractor;
+
+
+/**
+ * {@link WebViewClient} that intercepts requests for {@code cid:} URIs to load the respective body part.
+ */
+public abstract class K9WebViewClient extends WebViewClient {
+    private static final String CID_SCHEME = "cid";
+    private static final WebResourceResponse RESULT_DO_NOT_INTERCEPT = null;
+    private static final WebResourceResponse RESULT_DUMMY_RESPONSE = new WebResourceResponse(null, null, null);
+
+    public static WebViewClient newInstance(Message message) {
+        if (Build.VERSION.SDK_INT < 21) {
+            return new PreLollipopWebViewClient(message);
+        }
+
+        return new LollipopWebViewClient(message);
+    }
+
+
+    private final Message message;
+
+    private K9WebViewClient(Message message) {
+        this.message = message;
+    }
+
+    protected WebResourceResponse shouldInterceptRequest(WebView webView, Uri uri) {
+        if (!CID_SCHEME.equals(uri.getScheme())) {
+            return RESULT_DO_NOT_INTERCEPT;
+        }
+
+        String cid = uri.getSchemeSpecificPart();
+        if (TextUtils.isEmpty(cid)) {
+            return RESULT_DUMMY_RESPONSE;
+        }
+
+        Part part = getPartForContentId(cid);
+        if (part == null) {
+            return RESULT_DUMMY_RESPONSE;
+        }
+
+        Context context = webView.getContext();
+        ContentResolver contentResolver = context.getContentResolver();
+        try {
+            AttachmentViewInfo attachmentInfo = LocalMessageExtractor.extractAttachmentInfo(context, part);
+            String mimeType = attachmentInfo.mimeType;
+            InputStream inputStream = contentResolver.openInputStream(attachmentInfo.uri);
+
+            return new WebResourceResponse(mimeType, null, inputStream);
+        } catch (Exception e) {
+            Log.e(K9.LOG_TAG, "Error while intercepting URI: " + uri, e);
+            return RESULT_DUMMY_RESPONSE;
+        }
+    }
+
+    private Part getPartForContentId(String cid) {
+        Stack<Part> partsToCheck = new Stack<Part>();
+        partsToCheck.push(message);
+
+        while (!partsToCheck.isEmpty()) {
+            Part part = partsToCheck.pop();
+
+            Body body = part.getBody();
+            if (body instanceof Multipart) {
+                Multipart multipart = (Multipart) body;
+                for (Part bodyPart : multipart.getBodyParts()) {
+                    partsToCheck.push(bodyPart);
+                }
+            } else if (cid.equals(part.getContentId())) {
+                return part;
+            }
+        }
+
+        return null;
+    }
+
+
+    private static class PreLollipopWebViewClient extends K9WebViewClient {
+        protected PreLollipopWebViewClient(Message message) {
+            super(message);
+        }
+
+        @SuppressWarnings("deprecation")
+        @Override
+        public WebResourceResponse shouldInterceptRequest(WebView webView, String url) {
+            return shouldInterceptRequest(webView, Uri.parse(url));
+        }
+    }
+
+    @TargetApi(VERSION_CODES.LOLLIPOP)
+    private static class LollipopWebViewClient extends K9WebViewClient {
+        protected LollipopWebViewClient(Message message) {
+            super(message);
+        }
+
+        @Override
+        public WebResourceResponse shouldInterceptRequest(WebView webView, WebResourceRequest request) {
+            return shouldInterceptRequest(webView, request.getUrl());
+        }
+    }
+}