From 734ac1e1d2b3ce10a2da1a7e736a30bdf0bc5cf8 Mon Sep 17 00:00:00 2001
From: Jay Berkenbilt <ejb@ql.org>
Date: Mon, 19 Oct 2009 01:58:31 +0000
Subject: deal with stream-specific crypt filters

git-svn-id: svn+q:///qpdf/trunk@827 71b93d88-0707-0410-a8cf-f5a4172ac649
---
 libqpdf/QPDFObjectHandle.cc | 23 +++++++++++++++++++++++
 libqpdf/QPDF_Stream.cc      | 16 ++++++++++++++--
 libqpdf/QPDF_encryption.cc  | 25 +++++++++++++------------
 3 files changed, 50 insertions(+), 14 deletions(-)

(limited to 'libqpdf')

diff --git a/libqpdf/QPDFObjectHandle.cc b/libqpdf/QPDFObjectHandle.cc
index 08d648bd..c3a7167b 100644
--- a/libqpdf/QPDFObjectHandle.cc
+++ b/libqpdf/QPDFObjectHandle.cc
@@ -258,6 +258,29 @@ QPDFObjectHandle::getKeys()
     return dynamic_cast<QPDF_Dictionary*>(obj.getPointer())->getKeys();
 }
 
+// Array and Name accessors
+bool
+QPDFObjectHandle::isOrHasName(std::string const& value)
+{
+    if (isName() && (getName() == value))
+    {
+	return true;
+    }
+    else if (isArray())
+    {
+	int n = getArrayNItems();
+	for (int i = 0; i < n; ++i)
+	{
+	    QPDFObjectHandle item = getArrayItem(0);
+	    if (item.isName() && (item.getName() == value))
+	    {
+		return true;
+	    }
+	}
+    }
+    return false;
+}
+
 // Dictionary mutators
 
 void
diff --git a/libqpdf/QPDF_Stream.cc b/libqpdf/QPDF_Stream.cc
index a9e2ec51..6642a06e 100644
--- a/libqpdf/QPDF_Stream.cc
+++ b/libqpdf/QPDF_Stream.cc
@@ -136,6 +136,13 @@ QPDF_Stream::filterable(std::vector<std::string>& filters,
 		    filterable = false;
 		}
 	    }
+	    else if (((key == "/Type") || (key == "/Name")) &&
+		     decode_obj.getKey("/Type").isName() &&
+		     (decode_obj.getKey("/Type").getName() ==
+		      "/CryptFilterDecodeParms"))
+	    {
+		// we handle this in decryptStream
+	    }
 	    else
 	    {
 		filterable = false;
@@ -212,7 +219,8 @@ QPDF_Stream::filterable(std::vector<std::string>& filters,
 	 iter != filters.end(); ++iter)
     {
 	std::string const& filter = *iter;
-	if (! ((filter == "/FlateDecode") ||
+	if (! ((filter == "/Crypt") ||
+	       (filter == "/FlateDecode") ||
 	       (filter == "/LZWDecode") ||
 	       (filter == "/ASCII85Decode") ||
 	       (filter == "/ASCIIHexDecode")))
@@ -266,7 +274,11 @@ QPDF_Stream::pipeStreamData(Pipeline* pipeline, bool filter,
 	     iter != filters.rend(); ++iter)
 	{
 	    std::string const& filter = *iter;
-	    if (filter == "/FlateDecode")
+	    if (filter == "/Crypt")
+	    {
+		// Ignore -- handled by pipeStreamData
+	    }
+	    else if (filter == "/FlateDecode")
 	    {
 		if (predictor == 12)
 		{
diff --git a/libqpdf/QPDF_encryption.cc b/libqpdf/QPDF_encryption.cc
index fa16f55d..8962624d 100644
--- a/libqpdf/QPDF_encryption.cc
+++ b/libqpdf/QPDF_encryption.cc
@@ -600,18 +600,19 @@ QPDF::decryptStream(Pipeline*& pipeline, int objid, int generation,
 	encryption_method_e method = e_unknown;
 	std::string method_source = "/StmF from /Encrypt dictionary";
 
-	// NOTE: the section in the PDF specification on crypt filters
-	// seems to suggest that there might be a /Crypt key in
-	// /DecodeParms whose value is a crypt filter (.e.g., << /Name
-	// /StdCF >>), but implementation notes suggest this can only
-	// happen for metadata streams, and emperical observation
-	// suggests that they are otherwise ignored.  Not having been
-	// able to find a sample file that uses crypt filters in any
-	// way other than /StrF and /StmF, I'm not really sure what to
-	// do about this.  If we were to override the encryption on a
-	// per-stream basis using crypt filters, set method_source to
-	// something useful in the error message for unknown
-	// encryption methods (search for method_source).
+	if (stream_dict.getKey("/Filter").isOrHasName("/Crypt") &&
+	    stream_dict.getKey("/DecodeParms").isDictionary())
+	{
+	    QPDFObjectHandle decode_parms = stream_dict.getKey("/DecodeParms");
+	    if (decode_parms.getKey("/Type").isName() &&
+		(decode_parms.getKey("/Type").getName() ==
+		 "/CryptFilterDecodeParms"))
+	    {
+		QTC::TC("qpdf", "QPDF_encryption stream crypt filter");
+		method = interpretCF(decode_parms.getKey("/Name"));
+		method_source = "stream's Crypt decode parameters";
+	    }
+	}
 
 	if (method == e_unknown)
 	{
-- 
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