reading crypt filters is largely implemented but not fully tested

git-svn-id: svn+q:///qpdf/trunk@812 71b93d88-0707-0410-a8cf-f5a4172ac649

reading crypt filters is largely implemented but not fully tested
git-svn-id: svn+q:///qpdf/trunk@812 71b93d88-0707-0410-a8cf-f5a4172ac649
Jay Berkenbilt
1 parent c13bc66d
Showing 7 changed files with 195 additions and 26 deletions
include/qpdf/QPDF.hh
libqpdf/Pl_AES_PDF.cc
libqpdf/QPDF.cc
libqpdf/QPDF_Stream.cc
libqpdf/QPDF_encryption.cc
libqpdf/qpdf/Pl_AES_PDF.hh
qpdf/qpdf.testcov
@@ -87,6 +87,7 @@ class DLL_EXPORT QPDF
     // Encryption support
+    enum encryption_method_e { e_none, e_unknown, e_rc4, e_aes };
     struct EncryptionData
     {
 	// This class holds data read from the encryption dictionary.
@@ -397,6 +398,7 @@ class DLL_EXPORT QPDF
 			     std::vector<QPDFObjectHandle>& result);
     // methods to support encryption -- implemented in QPDF_encryption.cc
+    encryption_method_e interpretCF(QPDFObjectHandle);
     void initializeEncryption();
     std::string getKeyForObject(int objid, int generation, bool use_aes);
     void decryptString(std::string&, int objid, int generation);
@@ -739,7 +741,10 @@ class DLL_EXPORT QPDF
     bool attempt_recovery;
     int encryption_V;
     bool encrypt_metadata;
-    QPDFObjectHandle encryption_dictionary;
+    std::map<std::string, encryption_method_e> crypt_filters;
+    encryption_method_e cf_stream;
+    encryption_method_e cf_string;
+    encryption_method_e cf_file;
     std::string provided_password;
     std::string user_password;
     std::string encryption_key;
@@ -9,7 +9,7 @@
 #include <stdlib.h>
 Pl_AES_PDF::Pl_AES_PDF(char const* identifier, Pipeline* next,
-		       bool encrypt, unsigned char key[key_size]) :
+		       bool encrypt, unsigned char const key[key_size]) :
     Pipeline(identifier, next),
     encrypt(encrypt),
     cbc_mode(true),
@@ -255,6 +255,9 @@ QPDF::QPDF() :
     attempt_recovery(true),
     encryption_V(0),
     encrypt_metadata(true),
+    cf_stream(e_none),
+    cf_string(e_none),
+    cf_file(e_none),
     cached_key_objid(0),
     cached_key_generation(0),
     first_xref_item_offset(0),
@@ -136,6 +136,11 @@ QPDF_Stream::filterable(std::vector&lt;std::string&gt;&amp; filters,
 		    filterable = false;
 		}
 	    }
+	    else if (key == "/Crypt")
+	    {
+		// XXX untested
+		// we handle this in decryptStream
+	    }
 	    else
 	    {
 		filterable = false;
@@ -212,7 +217,8 @@ QPDF_Stream::filterable(std::vector&lt;std::string&gt;&amp; 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 +272,11 @@ 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)
 		{
@@ -9,6 +9,7 @@
 #include <qpdf/QUtil.hh>
 #include <qpdf/Pl_RC4.hh>
 #include <qpdf/Pl_AES_PDF.hh>
+#include <qpdf/Pl_Buffer.hh>
 #include <qpdf/RC4.hh>
 #include <qpdf/MD5.hh>
@@ -281,6 +282,27 @@ check_owner_password(std::string&amp; user_password,
     return result;
 }
+QPDF::encryption_method_e
+QPDF::interpretCF(QPDFObjectHandle cf)
+{
+    if (cf.isName())
+    {
+	std::string filter = cf.getName();
+	if (this->crypt_filters.count(filter) != 0)
+	{
+	    return this->crypt_filters[filter];
+	}
+	else
+	{
+	    return e_unknown;
+	}
+    }
+    else
+    {
+	return e_none;
+    }
+}
+
 void
 QPDF::initializeEncryption()
 {
@@ -322,8 +344,7 @@ QPDF::initializeEncryption()
 		      "incorrect length");
     }
-    this->encryption_dictionary = this->trailer.getKey("/Encrypt");
-    QPDFObjectHandle& encryption_dict = this->encryption_dictionary;
+    QPDFObjectHandle encryption_dict = this->trailer.getKey("/Encrypt");
     if (! encryption_dict.isDictionary())
     {
 	throw QPDFExc(this->file.getName(), this->file.getLastOffset(),
@@ -336,6 +357,12 @@ QPDF::initializeEncryption()
 	throw QPDFExc(this->file.getName(), this->file.getLastOffset(),
 		      "unsupported encryption filter");
     }
+    if (! encryption_dict.getKey("/SubFilter").isNull())
+    {
+	warn(QPDFExc(this->file.getName(), this->file.getLastOffset(),
+		     "file uses encryption SubFilters,"
+		     " which qpdf does not support"));
+    }
     if (! (encryption_dict.getKey("/V").isInteger() &&
 	   encryption_dict.getKey("/R").isInteger() &&
@@ -388,10 +415,55 @@ QPDF::initializeEncryption()
 	    encryption_dict.getKey("/EncryptMetadata").getBoolValue();
     }
-    // XXX warn if /SubFilter is present
     if (V == 4)
     {
-	// XXX get CF
+	QPDFObjectHandle CF = encryption_dict.getKey("/CF");
+	std::set<std::string> keys = CF.getKeys();
+	for (std::set<std::string>::iterator iter = keys.begin();
+	     iter != keys.end(); ++iter)
+	{
+	    std::string const& filter = *iter;
+	    QPDFObjectHandle cdict = CF.getKey(filter);
+	    if (cdict.isDictionary())
+	    {
+		encryption_method_e method = e_none;
+		if (cdict.getKey("/CFM").isName())
+		{
+		    std::string method_name = cdict.getKey("/CFM").getName();
+		    if (method_name == "/V2")
+		    {
+			// XXX coverage
+			method = e_rc4;
+		    }
+		    else if (method_name == "/AESV2")
+		    {
+			// XXX coverage
+			method = e_aes;
+		    }
+		    else
+		    {
+			// Don't complain now -- maybe we won't need
+			// to reference this type.
+			method = e_unknown;
+		    }
+		}
+		this->crypt_filters[filter] = method;
+	    }
+	}
+
+	QPDFObjectHandle StmF = encryption_dict.getKey("/StmF");
+	QPDFObjectHandle StrF = encryption_dict.getKey("/StrF");
+	QPDFObjectHandle EFF = encryption_dict.getKey("/EFF");
+	this->cf_stream = interpretCF(StmF);
+	this->cf_string = interpretCF(StrF);
+	if (EFF.isName())
+	{
+	    this->cf_file = interpretCF(EFF);
+	}
+	else
+	{
+	    this->cf_file = this->cf_stream;
+	}
     }
     EncryptionData data(V, R, Length / 8, P, O, U, id1, this->encrypt_metadata);
     if (check_owner_password(
@@ -440,15 +512,50 @@ QPDF::decryptString(std::string&amp; str, int objid, int generation)
     {
 	return;
     }
-    bool use_aes = false;	// XXX
+    bool use_aes = false;
+    if (this->encryption_V == 4)
+    {
+	switch (this->cf_string)
+	{
+	  case e_none:
+	    return;
+
+	  case e_aes:
+	    use_aes = true;
+	    break;
+
+	  case e_rc4:
+	    break;
+
+	  default:
+	    warn(QPDFExc(this->file.getName(), this->file.getLastOffset(),
+			 "unknown encryption filter for strings"
+			 " (check /StrF in /Encrypt dictionary);"
+			 " strings may be decrypted improperly"));
+	    // To avoid repeated warnings, reset cf_string.  Assume
+	    // we'd want to use AES if V == 4.
+	    this->cf_string = e_aes;
+	    break;
+	}
+    }
+
     std::string key = getKeyForObject(objid, generation, use_aes);
     if (use_aes)
     {
-	// XXX
-	throw std::logic_error("XXX");
+	// XXX coverage
+	assert(key.length() == Pl_AES_PDF::key_size);
+	Pl_Buffer bufpl("decrypted string");
+	Pl_AES_PDF pl("aes decrypt string", &bufpl, false,
+		      (unsigned char const*)key.c_str());
+	pl.write((unsigned char*)str.c_str(), str.length());
+	pl.finish();
+	Buffer* buf = bufpl.getBuffer();
+	str = std::string((char*)buf->getBuffer(), (size_t)buf->getSize());
+	delete buf;
     }
     else
     {
+	QTC::TC("qpdf", "QPDF_encryption rc4 decode string");
 	unsigned int vlen = str.length();
 	char* tmp = QUtil::copy_string(str);
 	RC4 rc4((unsigned char const*)key.c_str(), key.length());
@@ -463,7 +570,6 @@ QPDF::decryptStream(Pipeline*&amp; pipeline, int objid, int generation,
 		    QPDFObjectHandle& stream_dict,
 		    std::vector<PointerHolder<Pipeline> >& heap)
 {
-    bool decrypt = true;
     std::string type;
     if (stream_dict.getKey("/Type").isName())
     {
@@ -471,34 +577,77 @@ QPDF::decryptStream(Pipeline*&amp; pipeline, int objid, int generation,
     }
     if (type == "/XRef")
     {
-	QTC::TC("qpdf", "QPDF piping xref stream from encrypted file");
-	decrypt = false;
+	QTC::TC("qpdf", "QPDF_encryption xref stream from encrypted file");
+	return;
     }
     bool use_aes = false;
     if (this->encryption_V == 4)
     {
-	if ((! this->encrypt_metadata) && (type == "/Metadata"))
+	encryption_method_e method = e_unknown;
+	std::string method_source = "/StmF from /Encrypt dictionary";
+
+	if (stream_dict.getKey("/DecodeParms").isDictionary())
 	{
-	    // XXX no test case for this
-	    decrypt = false;
+	    QPDFObjectHandle decode_parms = stream_dict.getKey("/DecodeParms");
+	    if (decode_parms.getKey("/Crypt").isDictionary())
+	    {
+		// XXX coverage
+		QPDFObjectHandle crypt = decode_parms.getKey("/Crypt");
+		method = interpretCF(crypt.getKey("/Name"));
+		method_source = "stream's Crypt decode parameters";
+	    }
 	}
-	// XXX check crypt filter; if not found, use StmF; see TODO
-	use_aes = true;		// XXX
-    }
-    if (! decrypt)
-    {
-	return;
-    }
+	if (method == e_unknown)
+	{
+	    if ((! this->encrypt_metadata) && (type == "/Metadata"))
+	    {
+		// XXX coverage
+		method = e_none;
+	    }
+	    else
+	    {
+		method = this->cf_stream;
+	    }
+	    // XXX What about embedded file streams?
+	}
+	use_aes = false;
+	switch (this->cf_stream)
+	{
+	  case e_none:
+	    return;
+	    break;
+
+	  case e_aes:
+	    use_aes = true;
+	    break;
+
+	  case e_rc4:
+	    break;
+
+	  default:
+	    // filter local to this stream.
+	    warn(QPDFExc(this->file.getName(), this->file.getLastOffset(),
+			 "unknown encryption filter for streams"
+			 " (check " + method_source + ");"
+			 " streams may be decrypted improperly"));
+	    // To avoid repeated warnings, reset cf_stream.  Assume
+	    // we'd want to use AES if V == 4.
+	    this->cf_stream = e_aes;
+	    break;
+	}
+    }
     std::string key = getKeyForObject(objid, generation, use_aes);
     if (use_aes)
     {
+	// XXX coverage
 	assert(key.length() == Pl_AES_PDF::key_size);
 	pipeline = new Pl_AES_PDF("AES stream decryption", pipeline,
 				  false, (unsigned char*) key.c_str());
     }
     else
     {
+	QTC::TC("qpdf", "QPDF_encryption rc4 decode stream");
 	pipeline = new Pl_RC4("RC4 stream decryption", pipeline,
 			      (unsigned char*) key.c_str(), key.length());
     }
@@ -12,7 +12,7 @@ class DLL_EXPORT Pl_AES_PDF: public Pipeline
     // key_data should be a pointer to key_size bytes of data
     static unsigned int const key_size = 16;
     Pl_AES_PDF(char const* identifier, Pipeline* next,
-	       bool encrypt, unsigned char key[key_size]);
+	       bool encrypt, unsigned char const key[key_size]);
     virtual ~Pl_AES_PDF();
     virtual void write(unsigned char* data, int len);
@@ -112,7 +112,7 @@ QPDF found wrong endstream in recovery 0
 QPDFObjectHandle indirect to unknown 0
 QPDF_Stream pipeStreamData with null pipeline 0
 QPDFWriter not recompressing /FlateDecode 0
-QPDF piping xref stream from encrypted file 0
+QPDF_encryption xref stream from encrypted file 0
 unable to filter 0
 QPDF_String non-trivial UTF-16 0
 QPDF xref overwrite object 0
@@ -158,3 +158,5 @@ QPDFWriter using forced PDF version 0
 qpdf-c called qpdf_set_minimum_pdf_version 0
 qpdf-c called qpdf_force_pdf_version 0
 qpdf-c called qpdf_init_write multiple times 0
+QPDF_encryption rc4 decode string 0
+QPDF_encryption rc4 decode stream 0