use StdCF to make adobe reader happy; handle EncryptMetadata properly when reading

git-svn-id: svn+q:///qpdf/trunk@817 71b93d88-0707-0410-a8cf-f5a4172ac649

TODO

@@ -55,12 +55,12 @@
 
     - figure out a way to test crypt filters defined on a stream
 
+    - test extraction of metadata with and without encrypted metadata
+
     - would be nice to test strings and streams with different
       encryption types, but without sample data, we'd have to write
       them ourselves which is not that useful
 
-    - figure out why xpdf can open my files but not acroread
-
     - figure out how to look at the metadata so I can tell whether
       /EncryptMetadata is working the way it's supposed to
 

libqpdf/QPDFWriter.cc

@@ -363,11 +363,14 @@ QPDFWriter::setEncryptionParametersInternal(
     }
     if (V == 4)
     {
-	encryption_dictionary["/StmF"] = "/CF1";
-	encryption_dictionary["/StrF"] = "/CF1";
+	// The spec says the value for the crypt filter key can be
+	// anything, and xpdf seems to agree.  However, Adobe Reader
+	// won't open our files unless we use /StdCF.
+	encryption_dictionary["/StmF"] = "/StdCF";
+	encryption_dictionary["/StrF"] = "/StdCF";
 	std::string method = (this->encrypt_use_aes ? "/AESV2" : "/V2");
 	encryption_dictionary["/CF"] =
-	    "<< /CF1 << /AuthEvent /DocOpen /CFM " + method + " >> >>";
+	    "<< /StdCF << /AuthEvent /DocOpen /CFM " + method + " >> >>";
     }
 
     this->encrypted = true;

libqpdf/QPDF_encryption.cc

@@ -612,7 +612,7 @@ QPDF::decryptStream(Pipeline*& pipeline, int objid, int generation,
 	    // XXX What about embedded file streams?
 	}
 	use_aes = false;
-	switch (this->cf_stream)
+	switch (method)
 	{
 	  case e_none:
 	    return;