tdf#105844 package,sfx2: wholesome ODF package wrapping encryption

Redo the ODF encryption by storing an ODF package and wrapping it as a
stream "encrypted-package" in another ODF package, such that there is
only one encrypted stream - this requires only one KDF computation.

* This is only enabled in Experimental mode for now.

* Avoid storing unencrypted data in the pTempFile of SfxMedium, as it
  is usually created in the same directory as the target file, which
  may be on a network share or similar less trusted location.

* SfxMedium::SetEncryptionDataToStorage_Impl() should just set an
  error status if it fails (how can it fail anyway)

* when loading a document, SfxDocPasswordVerifier extracts an encrypted
  inner package (by calling SfxMedium::TryEncryptedInnerPackage())

* SfxMedium::GetStorage() automatically decrypts an encrypted inner
  storage and sets it as the SfxMedium's xStorage

* when storing a document, SfxObjectShell::SaveTo_Impl() creates
  the wrapped storages

* One challenge is to keep the macro/scripting signature working; this
  can only be put in the inner storage, whereas the document signature
  should continue to be on the outer storage; also it must use a Zip
  storage, to see the "META-INF" directory.  This needs a new
  SfxMedium::GetScriptingStorageToSign_Impl() and changes in
  SfxMedium::SignContents_Impl().

Change-Id: Ibfee36ce3a9cd030f2aa2ce1484b6d001cba2389
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/160401
Tested-by: Jenkins
Reviewed-by: Michael Stahl <michael.stahl@allotropia.de>

1 files changed, 6 insertions, 2 deletions

diff --git a/package/source/zippackage/ZipPackage.cxx b/package/source/zippackage/ZipPackage.cxx
index 4dc2021a1904..46e87f437c7b 100644
--- a/package/source/zippackage/ZipPackage.cxx
+++ b/package/source/zippackage/ZipPackage.cxx
@@ -287,7 +287,9 @@ void ZipPackage::parseManifest()
                                     const sal_Int32 nStartKeyAlg = xml::crypto::DigestID::SHA256;
                                     pStream->SetImportedStartKeyAlgorithm( nStartKeyAlg );
 
-                                    if ( !m_bHasEncryptedEntries && pStream->getName() == "content.xml" )
+                                    if (!m_bHasEncryptedEntries
+                                        && (pStream->getName() == "content.xml"
+                                            || pStream->getName() == "encrypted-package"))
                                     {
                                         m_bHasEncryptedEntries = true;
                                         m_nChecksumDigestID = nDigestAlg;
@@ -336,7 +338,9 @@ void ZipPackage::parseManifest()
                                     pStream->SetToBeCompressed ( true );
                                     pStream->SetToBeEncrypted ( true );
                                     pStream->SetIsEncrypted ( true );
-                                    if ( !m_bHasEncryptedEntries && pStream->getName() == "content.xml" )
+                                    if (!m_bHasEncryptedEntries
+                                        && (pStream->getName() == "content.xml"
+                                            || pStream->getName() == "encrypted-package"))
                                     {
                                         m_bHasEncryptedEntries = true;
                                         m_nStartKeyGenerationID = nStartKeyAlg;