Support files with only attachments encrypted

Test cases added in a future commit since they depend on /R=6 support.

Support files with only attachments encrypted
Test cases added in a future commit since they depend on /R=6 support.
Jay Berkenbilt
1 parent eff2c9a6
Showing 9 changed files with 253 additions and 179 deletions
TODO
include/qpdf/QPDF.hh
libqpdf/QPDF.cc
libqpdf/QPDFWriter.cc
libqpdf/QPDF_Stream.cc
libqpdf/QPDF_encryption.cc
libqpdf/qpdf/QPDF_Stream.hh
qpdf/qpdf.testcov
qpdf/qtest/qpdf/obj0-check.out
@@ -89,20 +89,11 @@ Index: QPDFWriter.cc
  }
 ------------------------------
- * Handle embedded files.  PDF Reference 1.7 section 3.10, "File
-   Specifications", discusses this.  Once we can definitely recognize
-   all embedded files in a document, we can update the encryption
-   code to handle it properly.  In QPDF_encryption.cc, search for
-   cf_file.  Remove exception thrown if cf_file is different from
-   cf_stream, and write code in the stream decryption section to use
-   cf_file instead of cf_stream.  In general, add interfaces to get
-   the list of embedded files and to extract them.  To handle general
-   embedded files associated with the whole document, follow root ->
-   /Names -> /EmbeddedFiles -> /Names to get to the file specification
-   dictionaries.  Then, in each file specification dictionary, follow
-   /EF -> /F to the actual stream.  There may be other places file
-   specification dictionaries may appear, and there are also /RF keys
-   with related files, so reread section 3.10 carefully.
+ * Provide APIs for embedded files.  See *attachments*.pdf in test
+   suite.  The private method findAttachmentStreams finds at least
+   cases for modern versions of Adobe Reader (>= 1.7, maybe earlier).
+   PDF Reference 1.7 section 3.10, "File Specifications", discusses
+   this.
    A sourceforge user asks if qpdf can handle extracting and embedded
    resources and references these tools, which may be useful as a
@@ -604,6 +604,7 @@ class QPDF
 	int& act_objid, int& act_generation);
     PointerHolder<QPDFObject> resolve(int objid, int generation);
     void resolveObjectsInStream(int obj_stream_number);
+    void findAttachmentStreams();
     // Calls finish() on the pipeline when done but does not delete it
     void pipeStreamData(int objid, int generation,
@@ -1004,6 +1005,7 @@ class QPDF
     PointerHolder<QPDFObjectHandle::StreamDataProvider> copied_streams;
     // copied_stream_data_provider is owned by copied_streams
     CopiedStreamDataProvider* copied_stream_data_provider;
+    std::set<ObjGen> attachment_streams;
     // Linearization data
     qpdf_offset_t first_xref_item_offset; // actual value from file
@@ -314,6 +314,7 @@ QPDF::parse(char const* password)
     }
     initializeEncryption();
+    findAttachmentStreams();
 }
 void
@@ -2069,3 +2070,38 @@ QPDF::pipeStreamData(int objid, int generation,
     }
     pipeline->finish();
 }
+
+void
+QPDF::findAttachmentStreams()
+{
+    QPDFObjectHandle root = getRoot();
+    QPDFObjectHandle names = root.getKey("/Names");
+    if (! names.isDictionary())
+    {
+        return;
+    }
+    QPDFObjectHandle embeddedFiles = names.getKey("/EmbeddedFiles");
+    if (! embeddedFiles.isDictionary())
+    {
+        return;
+    }
+    names = embeddedFiles.getKey("/Names");
+    if (! names.isArray())
+    {
+        return;
+    }
+    for (int i = 0; i < names.getArrayNItems(); ++i)
+    {
+        QPDFObjectHandle item = names.getArrayItem(i);
+        if (item.isDictionary() &&
+            item.getKey("/Type").isName() &&
+            (item.getKey("/Type").getName() == "/Filespec") &&
+            item.getKey("/EF").isDictionary() &&
+            item.getKey("/EF").getKey("/F").isStream())
+        {
+            QPDFObjectHandle stream = item.getKey("/EF").getKey("/F");
+            this->attachment_streams.insert(
+                ObjGen(stream.getObjectID(), stream.getGeneration()));
+        }
+    }
+}
@@ -470,27 +470,13 @@ QPDFWriter::copyEncryptionParameters(QPDF&amp; qpdf)
 	}
         if (V >= 4)
         {
-            if (encrypt.hasKey("/CF") &&
-                encrypt.getKey("/CF").isDictionary() &&
-                encrypt.hasKey("/StmF") &&
-                encrypt.getKey("/StmF").isName())
-            {
-                // Determine whether to use AES from StmF.  QPDFWriter
-                // can't write files with different StrF and StmF.
-                QPDFObjectHandle CF = encrypt.getKey("/CF");
-                QPDFObjectHandle StmF = encrypt.getKey("/StmF");
-                if (CF.hasKey(StmF.getName()) &&
-                    CF.getKey(StmF.getName()).isDictionary())
-                {
-                    QPDFObjectHandle StmF_data = CF.getKey(StmF.getName());
-                    if (StmF_data.hasKey("/CFM") &&
-                        StmF_data.getKey("/CFM").isName() &&
-                        StmF_data.getKey("/CFM").getName() == "/AESV2")
-                    {
-                        this->encrypt_use_aes = true;
-                    }
-                }
-            }
+            // When copying encryption parameters, use AES even if the
+            // original file did not.  Acrobat doesn't create files
+            // with V >= 4 that don't use AES, and the logic of
+            // figuring out whether AES is used or not is complicated
+            // with /StmF, /StrF, and /EFF all potentially having
+            // different values.
+            this->encrypt_use_aes = true;
         }
 	QTC::TC("qpdf", "QPDFWriter copy encrypt metadata",
 		this->encrypt_metadata ? 0 : 1);
@@ -91,6 +91,80 @@ QPDF_Stream::getRawStreamData()
 }
 bool
+QPDF_Stream::understandDecodeParams(
+    std::string const& filter, QPDFObjectHandle decode_obj,
+    int& predictor, int& columns, bool& early_code_change)
+{
+    bool filterable = true;
+    std::set<std::string> keys = decode_obj.getKeys();
+    for (std::set<std::string>::iterator iter = keys.begin();
+         iter != keys.end(); ++iter)
+    {
+        std::string const& key = *iter;
+        if ((filter == "/FlateDecode") && (key == "/Predictor"))
+        {
+            QPDFObjectHandle predictor_obj = decode_obj.getKey(key);
+            if (predictor_obj.isInteger())
+            {
+                predictor = predictor_obj.getIntValue();
+                if (! ((predictor == 1) || (predictor == 12)))
+                {
+                    filterable = false;
+                }
+            }
+            else
+            {
+                filterable = false;
+            }
+        }
+        else if ((filter == "/LZWDecode") && (key == "/EarlyChange"))
+        {
+            QPDFObjectHandle earlychange_obj = decode_obj.getKey(key);
+            if (earlychange_obj.isInteger())
+            {
+                int earlychange = earlychange_obj.getIntValue();
+                early_code_change = (earlychange == 1);
+                if (! ((earlychange == 0) || (earlychange == 1)))
+                {
+                    filterable = false;
+                }
+            }
+            else
+            {
+                filterable = false;
+            }
+        }
+        else if (key == "/Columns")
+        {
+            QPDFObjectHandle columns_obj = decode_obj.getKey(key);
+            if (columns_obj.isInteger())
+            {
+                columns = columns_obj.getIntValue();
+            }
+            else
+            {
+                filterable = false;
+            }
+        }
+        else if ((filter == "/Crypt") &&
+                 (((key == "/Type") || (key == "/Name")) &&
+                  (decode_obj.getKey("/Type").isNull() ||
+                   (decode_obj.getKey("/Type").isName() &&
+                    (decode_obj.getKey("/Type").getName() ==
+                     "/CryptFilterDecodeParms")))))
+        {
+            // we handle this in decryptStream
+        }
+        else
+        {
+            filterable = false;
+        }
+    }
+
+    return filterable;
+}
+
+bool
 QPDF_Stream::filterable(std::vector<std::string>& filters,
 			int& predictor, int& columns,
 			bool& early_code_change)
@@ -110,106 +184,6 @@ QPDF_Stream::filterable(std::vector&lt;std::string&gt;&amp; filters,
 	filter_abbreviations["/DCT"] = "/DCTDecode";
     }
-    // Initialize values to their defaults as per the PDF spec
-    predictor = 1;
-    columns = 0;
-    early_code_change = true;
-
-    bool filterable = true;
-
-    // See if we can support any decode parameters that are specified.
-
-    QPDFObjectHandle decode_obj =
-	this->stream_dict.getKey("/DecodeParms");
-    if (decode_obj.isNull())
-    {
-	// no problem
-    }
-    else if (decode_obj.isDictionary())
-    {
-	std::set<std::string> keys = decode_obj.getKeys();
-	for (std::set<std::string>::iterator iter = keys.begin();
-	     iter != keys.end(); ++iter)
-	{
-	    std::string const& key = *iter;
-	    if (key == "/Predictor")
-	    {
-		QPDFObjectHandle predictor_obj = decode_obj.getKey(key);
-		if (predictor_obj.isInteger())
-		{
-		    predictor = predictor_obj.getIntValue();
-		    if (! ((predictor == 1) || (predictor == 12)))
-		    {
-			filterable = false;
-		    }
-		}
-		else
-		{
-		    filterable = false;
-		}
-	    }
-	    else if (key == "/EarlyChange")
-	    {
-		QPDFObjectHandle earlychange_obj = decode_obj.getKey(key);
-		if (earlychange_obj.isInteger())
-		{
-		    int earlychange = earlychange_obj.getIntValue();
-		    early_code_change = (earlychange == 1);
-		    if (! ((earlychange == 0) || (earlychange == 1)))
-		    {
-			filterable = false;
-		    }
-		}
-		else
-		{
-		    filterable = false;
-		}
-	    }
-	    else if (key == "/Columns")
-	    {
-		QPDFObjectHandle columns_obj = decode_obj.getKey(key);
-		if (columns_obj.isInteger())
-		{
-		    columns = columns_obj.getIntValue();
-		}
-		else
-		{
-		    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;
-	    }
-	}
-    }
-    else
-    {
-	// Ignore for now -- some filter types, like CCITTFaxDecode,
-	// use types other than dictionary for this.
-	QTC::TC("qpdf", "QPDF_Stream ignore non-dictionary DecodeParms");
-
-	filterable = false;
-    }
-
-    if ((predictor > 1) && (columns == 0))
-    {
-	// invalid
-	filterable = false;
-    }
-
-    if (! filterable)
-    {
-	return false;
-    }
-
     // Check filters
     QPDFObjectHandle filter_obj = this->stream_dict.getKey("/Filter");
@@ -254,8 +228,7 @@ QPDF_Stream::filterable(std::vector&lt;std::string&gt;&amp; filters,
 		      "stream filter type is not name or array");
     }
-    // `filters' now contains a list of filters to be applied in
-    // order.  See which ones we can support.
+    bool filterable = true;
     for (std::vector<std::string>::iterator iter = filters.begin();
 	 iter != filters.end(); ++iter)
@@ -278,6 +251,79 @@ QPDF_Stream::filterable(std::vector&lt;std::string&gt;&amp; filters,
 	}
     }
+    if (! filterable)
+    {
+        return false;
+    }
+
+    // `filters' now contains a list of filters to be applied in
+    // order.  See which ones we can support.
+
+    // Initialize values to their defaults as per the PDF spec
+    predictor = 1;
+    columns = 0;
+    early_code_change = true;
+
+    // See if we can support any decode parameters that are specified.
+
+    QPDFObjectHandle decode_obj = this->stream_dict.getKey("/DecodeParms");
+    std::vector<QPDFObjectHandle> decode_parms;
+    if (decode_obj.isArray())
+    {
+        for (int i = 0; i < decode_obj.getArrayNItems(); ++i)
+        {
+            decode_parms.push_back(decode_obj.getArrayItem(i));
+        }
+    }
+    else
+    {
+        for (unsigned int i = 0; i < filters.size(); ++i)
+        {
+            decode_parms.push_back(decode_obj);
+        }
+    }
+
+    if (decode_parms.size() != filters.size())
+    {
+	throw QPDFExc(qpdf_e_damaged_pdf, qpdf->getFilename(),
+		      "", this->offset,
+		      "stream /DecodeParms length is"
+                      " inconsistent with filters");
+    }
+
+    for (unsigned int i = 0; i < filters.size(); ++i)
+    {
+        QPDFObjectHandle decode_item = decode_parms[i];
+        if (decode_item.isNull())
+        {
+            // okay
+        }
+        else if (decode_item.isDictionary())
+        {
+            if (! understandDecodeParams(
+                    filters[i], decode_item,
+                    predictor, columns, early_code_change))
+            {
+                filterable = false;
+            }
+        }
+        else
+        {
+            filterable = false;
+        }
+    }
+
+    if ((predictor > 1) && (columns == 0))
+    {
+	// invalid
+	filterable = false;
+    }
+
+    if (! filterable)
+    {
+	return false;
+    }
+
     return filterable;
 }
@@ -573,28 +573,6 @@ QPDF::initializeEncryption()
 	{
 	    this->cf_file = this->cf_stream;
 	}
-	if (this->cf_file != this->cf_stream)
-	{
-	    // The issue for qpdf is that it can't tell the difference
-	    // between an embedded file stream and a regular stream.
-	    // Search for a comment containing cf_file.  To fix this,
-	    // we need files with encrypted embedded files and
-	    // non-encrypted native streams and vice versa.  Also if
-	    // it is possible for them to be encrypted in different
-	    // ways, we should have some of those too.  In cases where
-	    // we can detect whether a stream is encrypted or not, we
-	    // might want to try to detecet that automatically in
-	    // defense of possible logic errors surrounding detection
-	    // of embedded file streams, unless that's really clear
-	    // from the specification.
-	    throw QPDFExc(qpdf_e_unsupported, this->file->getName(),
-			  "encryption dictionary", this->file->getLastOffset(),
-			  "This document has embedded files that are"
-			  " encrypted differently from the rest of the file."
-			  "  qpdf does not presently support this due to"
-			  " lack of test data; if possible, please submit"
-			  " a bug report that includes this file.");
-	}
     }
     EncryptionData data(V, R, Length / 8, P, O, U, "", "", "",
                         id1, this->encrypt_metadata);
@@ -737,18 +715,48 @@ QPDF::decryptStream(Pipeline*&amp; pipeline, int objid, int generation,
 	encryption_method_e method = e_unknown;
 	std::string method_source = "/StmF from /Encrypt dictionary";
-	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 (stream_dict.getKey("/Filter").isOrHasName("/Crypt"))
+        {
+            if (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";
+                }
+            }
+            else if (stream_dict.getKey("/DecodeParms").isArray() &&
+                     stream_dict.getKey("/Filter").isArray())
+            {
+                QPDFObjectHandle filter = stream_dict.getKey("/Filter");
+                QPDFObjectHandle decode = stream_dict.getKey("/DecodeParms");
+                if (filter.getArrayNItems() == decode.getArrayNItems())
+                {
+                    for (int i = 0; i < filter.getArrayNItems(); ++i)
+                    {
+                        if (filter.getArrayItem(i).isName() &&
+                            (filter.getArrayItem(i).getName() == "/Crypt"))
+                        {
+                            QPDFObjectHandle crypt_params =
+                                decode.getArrayItem(i);
+                            if (crypt_params.isDictionary() &&
+                                crypt_params.getKey("/Name").isName())
+                            {
+// XXX                          QTC::TC("qpdf", "QPDF_encrypt crypt array");
+                                method = interpretCF(
+                                    crypt_params.getKey("/Name"));
+                                method_source = "stream's Crypt "
+                                    "decode parameters (array)";
+                            }
+                        }
+                    }
+                }
+            }
 	}
 	if (method == e_unknown)
@@ -760,12 +768,15 @@ QPDF::decryptStream(Pipeline*&amp; pipeline, int objid, int generation,
 	    }
 	    else
 	    {
-		// NOTE: We should should use cf_file if this is an
-		// embedded file, but we can't yet detect embedded
-		// file streams as such.  When fixing, search for all
-		// occurrences of cf_file to find a reference to this
-		// comment.
-		method = this->cf_stream;
+                if (this->attachment_streams.count(
+                        ObjGen(objid, generation)) > 0)
+                {
+                    method = this->cf_file;
+                }
+                else
+                {
+                    method = this->cf_stream;
+                }
 	    }
 	}
 	use_aes = false;
@@ -45,6 +45,9 @@ class QPDF_Stream: public QPDFObject
     void replaceFilterData(QPDFObjectHandle const& filter,
 			   QPDFObjectHandle const& decode_parms,
 			   size_t length);
+    bool understandDecodeParams(
+        std::string const& filter, QPDFObjectHandle decode_params,
+        int& predictor, int& columns, bool& early_code_change);
     bool filterable(std::vector<std::string>& filters,
 		    int& predictor, int& columns, bool& early_code_change);
@@ -116,7 +116,6 @@ qpdf unable to filter 0
 QPDF_String non-trivial UTF-16 0
 QPDF xref overwrite object 0
 QPDF decoding error warning 0
-QPDF_Stream ignore non-dictionary DecodeParms 0
 qpdf-c called qpdf_init 0
 qpdf-c called qpdf_cleanup 0
 qpdf-c called qpdf_more_warnings 0
-checking obj0.pdf
 WARNING: obj0.pdf: file is damaged
 WARNING: obj0.pdf (object 1 0, file position 77): expected n n obj
 WARNING: obj0.pdf: Attempting to reconstruct cross-reference table
+checking obj0.pdf
 PDF Version: 1.3
 File is not encrypted
 File is not linearized