From f28ec43dca5b2915deb69d54fb942ddf1303f48c Mon Sep 17 00:00:00 2001
From: Christian Mollekopf <chrigi_1@fastmail.fm>
Date: Fri, 2 Mar 2018 12:07:18 +0100
Subject: Support encrypted mails forwarding

Summary:
Some notes:

- What we do is: if the mail is encrypted, decrypt it and copy its content into a new message (with plaintext, html and attachments, if any), and use this message as attachment for forwarding
- The `isEncrypted` function from KMime doesn't seem to detect every kind of encrypted mails. AFAIK this structure is not detected:
  - `multipart/mixed`
    - `text/plain`
    - `application/pgp-encrypted` (attachement, named "ATT00001")
    - `application/octet-stream` (attachment named "encrypted.asc")

Reviewers: cmollekopf

Tags: PHID-PROJ-6npnfcmppynqynn7slmv

Maniphest Tasks: T8112, T7024

Differential Revision: https://phabricator.kde.org/D10966
---
 framework/src/domain/mime/mailtemplates.cpp | 83 ++++++++++++++++++++++++++---
 1 file changed, 77 insertions(+), 6 deletions(-)

(limited to 'framework/src/domain/mime')

diff --git a/framework/src/domain/mime/mailtemplates.cpp b/framework/src/domain/mime/mailtemplates.cpp
index 8e644b34..513f0353 100644
--- a/framework/src/domain/mime/mailtemplates.cpp
+++ b/framework/src/domain/mime/mailtemplates.cpp
@@ -53,6 +53,18 @@ static bool operator==(const KMime::Types::Mailbox &left, const KMime::Types::Ma
     return (left.addrSpec().asString() == right.addrSpec().asString());
 }
     }
+
+    Message* contentToMessage(Content* content) {
+        content->assemble();
+        const auto encoded = content->encodedContent();
+
+        auto message = new Message();
+        message->setContent(encoded);
+        message->parse();
+
+        return message;
+    }
+
 }
 
 static KMime::Types::Mailbox::List stripMyAddressesFromAddressList(const KMime::Types::Mailbox::List &list, const KMime::Types::AddrSpecList me)
@@ -223,6 +235,19 @@ KMime::Content *createMultipartAlternativeContent(const QString &plainBody, cons
     return multipartAlternative;
 }
 
+KMime::Message *createMultipartMixedContent(QVector<KMime::Content *> contents)
+{
+    KMime::Message *multiPartMixed = new KMime::Message();
+    multiPartMixed->contentType()->setMimeType("multipart/mixed");
+    multiPartMixed->contentType()->setBoundary(KMime::multiPartBoundary());
+
+    for (const auto &content : contents) {
+        multiPartMixed->addContent(content);
+    }
+
+    return multiPartMixed;
+}
+
 void addProcessedBodyToMessage(const KMime::Message::Ptr &msg, const QString &plainBody, const QString &htmlBody, bool forward)
 {
     //FIXME
@@ -864,27 +889,73 @@ void MailTemplates::reply(const KMime::Message::Ptr &origMsg, const std::functio
     });
 }
 
-void MailTemplates::forward(const KMime::Message::Ptr &origMsg, const std::function<void(const KMime::Message::Ptr &result)> &callback)
+void MailTemplates::forward(const KMime::Message::Ptr &origMsg,
+    const std::function<void(const KMime::Message::Ptr &result)> &callback)
 {
     KMime::Message::Ptr wrapperMsg(new KMime::Message);
 
     wrapperMsg->to()->clear();
     wrapperMsg->cc()->clear();
 
-    wrapperMsg->subject()->fromUnicodeString(forwardSubject(origMsg->subject()->asUnicodeString()), "utf-8");
+    // Decrypt the original message, it will be encrypted again in the composer
+    // for the right recipient
+    KMime::Message::Ptr forwardedMessage;
+    if (isEncrypted(origMsg.data())) {
+        qDebug() << "Original message was encrypted, decrypting it";
+        MimeTreeParser::ObjectTreeParser otp;
+        otp.parseObjectTree(origMsg.data());
+        otp.decryptParts();
 
-    const QByteArray refStr = getRefStr(origMsg);
+        auto htmlContent = otp.htmlContent();
+        KMime::Content *recreatedMsg =
+            htmlContent.isEmpty() ? createPlainPartContent(otp.plainTextContent()) :
+                                    createMultipartAlternativeContent(otp.plainTextContent(), htmlContent);
+
+        if (hasAttachment(origMsg.data())) {
+            QVector<KMime::Content *> contents = {recreatedMsg};
+            contents.append(origMsg->attachments());
+
+            auto msg = createMultipartMixedContent(contents);
+
+            forwardedMessage.reset(KMime::contentToMessage(msg));
+        } else {
+            forwardedMessage.reset(KMime::contentToMessage(recreatedMsg));
+        }
+
+        forwardedMessage->subject()->from7BitString(origMsg->subject()->as7BitString());
+
+        for (const auto &addr : origMsg->to()->mailboxes()) {
+            forwardedMessage->to()->addAddress(addr);
+        }
+
+        for (const auto &addr : origMsg->cc()->mailboxes()) {
+            forwardedMessage->cc()->addAddress(addr);
+        }
+
+        for (const auto &addr : origMsg->bcc()->mailboxes()) {
+            forwardedMessage->bcc()->addAddress(addr);
+        }
+
+    } else {
+        qDebug() << "Original message was not encrypted, using it as-is";
+        forwardedMessage = origMsg;
+    }
+
+    wrapperMsg->subject()->fromUnicodeString(
+        forwardSubject(forwardedMessage->subject()->asUnicodeString()), "utf-8");
+
+    const QByteArray refStr = getRefStr(forwardedMessage);
     if (!refStr.isEmpty()) {
         wrapperMsg->references()->fromUnicodeString(QString::fromLocal8Bit(refStr), "utf-8");
     }
 
-    KMime::Content* fwdAttachment = new KMime::Content;
+    KMime::Content *fwdAttachment = new KMime::Content;
 
     fwdAttachment->contentDisposition()->setDisposition(KMime::Headers::CDinline);
     fwdAttachment->contentType()->setMimeType("message/rfc822");
-    fwdAttachment->contentDisposition()->setFilename(origMsg->subject()->asUnicodeString() + ".eml");
+    fwdAttachment->contentDisposition()->setFilename(forwardedMessage->subject()->asUnicodeString() + ".eml");
     // The mail was parsed in loadMessage before, so no need to assemble it
-    fwdAttachment->setBody(origMsg->encodedContent());
+    fwdAttachment->setBody(forwardedMessage->encodedContent());
 
     wrapperMsg->addContent(fwdAttachment);
     wrapperMsg->assemble();
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