checkpoint -- started doing some R4 encryption support

git-svn-id: svn+q:///qpdf/trunk@807 71b93d88-0707-0410-a8cf-f5a4172ac649

checkpoint -- started doing some R4 encryption support
git-svn-id: svn+q:///qpdf/trunk@807 71b93d88-0707-0410-a8cf-f5a4172ac649
Jay Berkenbilt
1 parent ad19b03f
Showing 11 changed files with 352 additions and 31 deletions
README
TODO
include/qpdf/QPDF.hh
libqpdf/Pl_AES_PDF.cc
libqpdf/QPDF.cc
libqpdf/QPDFWriter.cc
libqpdf/QPDF_encryption.cc
libqpdf/build.mk
libqpdf/qpdf/Pl_AES_PDF.hh
libtests/aes.cc
libtests/build.mk
@@ -8,6 +8,32 @@ Artistic License which may be found in the source distribution as
 "Artistic-2.0".  It is provided "as is" without express or implied
 warranty.
  
+
+Licensing terms of embedded software
+====================================
+
+Some additional software with additional licensing terms is embedded
+within the qpdf source distribution in "external-libs".  This software
+is not actually used by the qpdf build unless the
+--enable-build-external-libs option is passed to ./configure.  These
+packages have their own licensing terms, both of which are compatible
+with qpdf's license.
+
+Zlib's license can be read in external-libs/zlib/zlib.h
+
+PCRE's licensing terms can be found in external-libs/pcre/LICENSE.
+PCRE's licensing terms require that we include the following
+information:
+
+   Regular expression support is provided by the PCRE library package,
+   which is open source software, written by Philip Hazel, and
+   copyright by the University of Cambridge, England.
+
+The sources to PCRE can be independently obtained from
+
+   ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/
+
+
 Building on UNIX/Linux
 ======================
  
@@ -24,11 +50,11 @@ Building on Windows
 ===================
  
 QPDF is known to build and pass its test suite with mingw (gcc 4.4.0)
-and Microsoft Visual C++ .NET 2008 Express.  In both cases, cygwin is
-required to run the test suite.  Either cygwin or MSYS is required to
-build as well in order to get make and other related tools.  The MSVC
-build has only been tested under cygwin.  The mingw build requires
-MSYS and will probably not work with cygwin.
+and Microsoft Visual C++ .NET 2008 Express.  Either cygwin or MSYS
+plus ActivateState Perl is required to build as well in order to get
+make and other related tools.  The MSVC works with either cygwin or
+MSYS.  The mingw build requires MSYS and will probably not work with
+cygwin.
  
 For details on how to build under Windows, see README.windows.
  
@@ -56,6 +56,18 @@
    dictionary.  (V = 4 is Crypt Filters.)  See
    ~/Q/pdf-collection/R4-encrypt-PDF_Inside_and_Out.pdf
  
+   Search for XXX in the code.  Implementation has been started.
+
+   Algorithms from PDF Spec in QPDF_encrypt.cc have been updated.  We
+   can at least properly verify the user password with an R4 file.  In
+   order to finish the job, we need an aes-128-cbc implementation.
+   Then we can fill in the gaps for the aes pipeline and actually run
+   the test suite.  The pipeline may be able to hard-code the
+   initialization vector stuff by taking the first block of input and
+   by writing a random block for output.  The padding is already in
+   the code, but the initialization vector is not since I accidentally
+   started using an aes256 implementation instead of aes128-cbc.
+
  * Look at page splitting.
  
  
@@ -92,14 +92,15 @@ class DLL_EXPORT QPDF
 	// This class holds data read from the encryption dictionary.
 	EncryptionData(int V, int R, int Length_bytes, int P,
 		       std::string const& O, std::string const& U,
-		       std::string const& id1) :
+		       std::string const& id1, bool encrypt_metadata) :
 	    V(V),
 	    R(R),
 	    Length_bytes(Length_bytes),
 	    P(P),
 	    O(O),
 	    U(U),
-	    id1(id1)
+	    id1(id1),
+	    encrypt_metadata(encrypt_metadata)
 	{
 	}
  
@@ -110,6 +111,7 @@ class DLL_EXPORT QPDF
 	std::string O;
 	std::string U;
 	std::string id1;
+	bool encrypt_metadata;
     };
  
     bool isEncrypted() const;
@@ -132,7 +134,8 @@ class DLL_EXPORT QPDF
     // getTrimmedUserPassword's result.
     static void trim_user_password(std::string& user_password);
     static std::string compute_data_key(
-	std::string const& encryption_key, int objid, int generation);
+	std::string const& encryption_key, int objid, int generation,
+	bool use_aes);
     static std::string compute_encryption_key(
 	std::string const& password, EncryptionData const& data);
  
@@ -732,6 +735,7 @@ class DLL_EXPORT QPDF
     bool ignore_xref_streams;
     bool suppress_warnings;
     bool attempt_recovery;
+    bool encryption_use_aes;
     std::string provided_password;
     std::string user_password;
     std::string encryption_key;
+#include <qpdf/Pl_AES_PDF.hh>
+#include <qpdf/QUtil.hh>
+#include <cstring>
+#include <assert.h>
+#include <stdexcept>
+
+Pl_AES_PDF::Pl_AES_PDF(char const* identifier, Pipeline* next,
+		       bool encrypt, unsigned char* key_data) :
+    Pipeline(identifier, next),
+    encrypt(encrypt),
+    offset(0)
+{
+    std::memset(this->buf, 0, this->buf_size);
+    // XXX init
+}
+
+Pl_AES_PDF::~Pl_AES_PDF()
+{
+    // XXX finalize
+}
+
+void
+Pl_AES_PDF::write(unsigned char* data, int len)
+{
+    unsigned int bytes_left = len;
+    unsigned char* p = data;
+
+    while (bytes_left > 0)
+    {
+	if (this->offset == this->buf_size)
+	{
+	    flush(false);
+	}
+
+	unsigned int available = this->buf_size - this->offset;
+	int bytes = (bytes_left < available ? bytes_left : available);
+	bytes_left -= bytes;
+	std::memcpy(this->buf + this->offset, p, bytes);
+	this->offset += bytes;
+	p += bytes;
+    }
+}
+
+void
+Pl_AES_PDF::finish()
+{
+    if (this->encrypt)
+    {
+	if (this->offset == this->buf_size)
+	{
+	    flush(false);
+	}
+	// Pad as described in section 3.5.1 of version 1.7 of the PDF
+	// specification, including providing an entire block of padding
+	// if the input was a multiple of 16 bytes.
+	unsigned char pad = this->buf_size - this->offset;
+	memset(this->buf + this->offset, pad, pad);
+	this->offset = this->buf_size;
+	flush(false);
+    }
+    else
+    {
+	if (this->offset != this->buf_size)
+	{
+	    throw std::runtime_error(
+		"aes encrypted stream length was not a multiple of " +
+		QUtil::int_to_string(this->buf_size) + " bytes (offset = " +
+		QUtil::int_to_string(this->offset) + ")");
+	}
+	flush(true);
+    }
+    getNext()->finish();
+}
+
+void
+Pl_AES_PDF::flush(bool strip_padding)
+{
+    assert(this->offset == this->buf_size);
+    if (this->encrypt)
+    {
+	// XXX encrypt this->buf
+    }
+    else
+    {
+	// XXX decrypt this->buf
+    }
+    unsigned int bytes = this->buf_size;
+    if (strip_padding)
+    {
+	unsigned char last = this->buf[this->buf_size - 1];
+	if (last <= this->buf_size)
+	{
+	    bool strip = true;
+	    for (unsigned int i = 1; i <= last; ++i)
+	    {
+		if (this->buf[this->buf_size - i] != last)
+		{
+		    strip = false;
+		    break;
+		}
+	    }
+	    if (strip)
+	    {
+		bytes -= last;
+	    }
+	}
+    }
+    getNext()->write(this->buf, bytes);
+    this->offset = 0;
+}
@@ -253,6 +253,7 @@ QPDF::QPDF() :
     ignore_xref_streams(false),
     suppress_warnings(false),
     attempt_recovery(true),
+    encryption_use_aes(false),
     cached_key_objid(0),
     cached_key_generation(0),
     first_xref_item_offset(0),
@@ -326,7 +326,8 @@ QPDFWriter::setEncryptionParametersInternal(
     encryption_dictionary["/O"] = QPDF_String(O).unparse(true);
     encryption_dictionary["/U"] = QPDF_String(U).unparse(true);
     this->encrypted = true;
-    QPDF::EncryptionData encryption_data(V, R, key_len, P, O, U, this->id1);
+    QPDF::EncryptionData encryption_data(V, R, key_len, P, O, U, this->id1,
+					 /*XXX encrypt_metadata*/true);
     this->encryption_key = QPDF::compute_encryption_key(
 	user_password, encryption_data);
 }
@@ -335,7 +336,7 @@ void
 QPDFWriter::setDataKey(int objid)
 {
     this->cur_data_key = QPDF::compute_data_key(
-	this->encryption_key, objid, 0);
+	this->encryption_key, objid, 0, /*XXX use_aes */false);
 }
  
 int
@@ -99,9 +99,10 @@ iterate_rc4(unsigned char* data, int data_len,
  
 std::string
 QPDF::compute_data_key(std::string const& encryption_key,
-		       int objid, int generation)
+		       int objid, int generation,
+		       bool use_aes)
 {
-    // Algorithm 3.1 from the PDF 1.4 Reference Manual
+    // Algorithm 3.1 from the PDF 1.7 Reference Manual
  
     std::string result = encryption_key;
  
@@ -111,6 +112,10 @@ QPDF::compute_data_key(std::string const&amp; encryption_key,
     result += (char) ((objid >> 16) & 0xff);
     result += (char) (generation & 0xff);
     result += (char) ((generation >> 8) & 0xff);
+    if (use_aes)
+    {
+	result += "sAlT";
+    }
  
     MD5 md5;
     md5.encodeDataIncrementally(result.c_str(), result.length());
@@ -118,13 +123,16 @@ QPDF::compute_data_key(std::string const&amp; encryption_key,
     md5.digest(digest);
     return std::string((char*) digest,
 		       std::min(result.length(), (size_t) 16));
+
+    // XXX Item 4 in Algorithm 3.1 mentions CBC and a random number.
+    // We still have to incorporate that.
 }
  
 std::string
 QPDF::compute_encryption_key(
     std::string const& password, EncryptionData const& data)
 {
-    // Algorithm 3.2 from the PDF 1.4 Reference Manual
+    // Algorithm 3.2 from the PDF 1.7 Reference Manual
  
     MD5 md5;
     md5.encodeDataIncrementally(
@@ -137,8 +145,14 @@ QPDF::compute_encryption_key(
     pbytes[3] = (char) ((data.P >> 24) & 0xff);
     md5.encodeDataIncrementally(pbytes, 4);
     md5.encodeDataIncrementally(data.id1.c_str(), id_bytes);
+    if ((data.R >= 4) && (! data.encrypt_metadata))
+    {
+	char bytes[4];
+	memset(bytes, 0xff, 4);
+	md5.encodeDataIncrementally(bytes, 4);
+    }
     MD5::Digest digest;
-    iterate_md5_digest(md5, digest, ((data.R == 3) ? 50 : 0));
+    iterate_md5_digest(md5, digest, ((data.R >= 3) ? 50 : 0));
     return std::string((char*)digest, data.Length_bytes);
 }
  
@@ -157,7 +171,7 @@ compute_O_rc4_key(std::string const&amp; user_password,
     md5.encodeDataIncrementally(
 	pad_or_truncate_password(password).c_str(), key_bytes);
     MD5::Digest digest;
-    iterate_md5_digest(md5, digest, ((data.R == 3) ? 50 : 0));
+    iterate_md5_digest(md5, digest, ((data.R >= 3) ? 50 : 0));
     memcpy(key, digest, O_key_bytes);
 }
  
@@ -166,7 +180,7 @@ compute_O_value(std::string const&amp; user_password,
 		std::string const& owner_password,
 		QPDF::EncryptionData const& data)
 {
-    // Algorithm 3.3 from the PDF 1.4 Reference Manual
+    // Algorithm 3.3 from the PDF 1.7 Reference Manual
  
     unsigned char O_key[O_key_bytes];
     compute_O_rc4_key(user_password, owner_password, data, O_key);
@@ -174,7 +188,7 @@ compute_O_value(std::string const&amp; user_password,
     char upass[key_bytes];
     pad_or_truncate_password(user_password, upass);
     iterate_rc4((unsigned char*) upass, key_bytes,
-		O_key, data.Length_bytes, (data.R == 3) ? 20 : 1, false);
+		O_key, data.Length_bytes, (data.R >= 3) ? 20 : 1, false);
     return std::string(upass, key_bytes);
 }
  
@@ -183,7 +197,7 @@ std::string
 compute_U_value_R2(std::string const& user_password,
 		   QPDF::EncryptionData const& data)
 {
-    // Algorithm 3.4 from the PDF 1.4 Reference Manual
+    // Algorithm 3.4 from the PDF 1.7 Reference Manual
  
     std::string k1 = QPDF::compute_encryption_key(user_password, data);
     char udata[key_bytes];
@@ -198,7 +212,7 @@ std::string
 compute_U_value_R3(std::string const& user_password,
 		   QPDF::EncryptionData const& data)
 {
-    // Algorithm 3.5 from the PDF 1.4 Reference Manual
+    // Algorithm 3.5 from the PDF 1.7 Reference Manual
  
     std::string k1 = QPDF::compute_encryption_key(user_password, data);
     MD5 md5;
@@ -224,7 +238,7 @@ static std::string
 compute_U_value(std::string const& user_password,
 		QPDF::EncryptionData const& data)
 {
-    if (data.R == 3)
+    if (data.R >= 3)
     {
 	return compute_U_value_R3(user_password, data);
     }
@@ -236,10 +250,10 @@ static bool
 check_user_password(std::string const& user_password,
 		    QPDF::EncryptionData const& data)
 {
-    // Algorithm 3.6 from the PDF 1.4 Reference Manual
+    // Algorithm 3.6 from the PDF 1.7 Reference Manual
  
     std::string u_value = compute_U_value(user_password, data);
-    int to_compare = ((data.R == 3) ? sizeof(MD5::Digest) : key_bytes);
+    int to_compare = ((data.R >= 3) ? sizeof(MD5::Digest) : key_bytes);
     return (memcmp(data.U.c_str(), u_value.c_str(), to_compare) == 0);
 }
  
@@ -248,14 +262,14 @@ check_owner_password(std::string&amp; user_password,
 		     std::string const& owner_password,
 		     QPDF::EncryptionData const& data)
 {
-    // Algorithm 3.7 from the PDF 1.4 Reference Manual
+    // Algorithm 3.7 from the PDF 1.7 Reference Manual
  
     unsigned char key[O_key_bytes];
     compute_O_rc4_key(user_password, owner_password, data, key);
     unsigned char O_data[key_bytes];
     memcpy(O_data, (unsigned char*) data.O.c_str(), key_bytes);
     iterate_rc4(O_data, key_bytes, key, data.Length_bytes,
-		(data.R == 3) ? 20 : 1, true);
+		(data.R >= 3) ? 20 : 1, true);
     std::string new_user_password =
 	std::string((char*)O_data, key_bytes);
     bool result = false;
@@ -339,13 +353,20 @@ QPDF::initializeEncryption()
     std::string U = encryption_dict.getKey("/U").getStringValue();
     unsigned int P = (unsigned int) encryption_dict.getKey("/P").getIntValue();
  
-    if (! (((R == 2) || (R == 3)) &&
-	   ((V == 1) || (V == 2))))
+    if (! (((R == 2) || (R == 3) || (R == 4)) &&
+	   ((V == 1) || (V == 2) || (V == 4))))
     {
 	throw QPDFExc(this->file.getName(), this->file.getLastOffset(),
 		      "Unsupported /R or /V in encryption dictionary");
     }
  
+    // XXX remove this check to continue implementing R4.
+    if ((R == 4) || (V == 4))
+    {
+	throw QPDFExc(this->file.getName(), this->file.getLastOffset(),
+		      "PDF >= 1.5 encryption support is not fully implemented");
+    }
+
     if (! ((O.length() == key_bytes) && (U.length() == key_bytes)))
     {
 	throw QPDFExc(this->file.getName(), this->file.getLastOffset(),
@@ -364,7 +385,18 @@ QPDF::initializeEncryption()
 	}
     }
  
-    EncryptionData data(V, R, Length / 8, P, O, U, id1);
+    bool encrypt_metadata = true;
+    if ((V >= 4) && (encryption_dict.getKey("/EncryptMetadata").isBool()))
+    {
+	encrypt_metadata =
+	    encryption_dict.getKey("/EncryptMetadata").getBoolValue();
+    }
+    // XXX not really...
+    if (R >= 4)
+    {
+	this->encryption_use_aes = true;
+    }
+    EncryptionData data(V, R, Length / 8, P, O, U, id1, encrypt_metadata);
     if (check_owner_password(this->user_password, this->provided_password, data))
     {
 	// password supplied was owner password; user_password has
@@ -395,7 +427,8 @@ QPDF::getKeyForObject(int objid, int generation)
 	   (generation == this->cached_key_generation)))
     {
 	this->cached_object_encryption_key =
-	    compute_data_key(this->encryption_key, objid, generation);
+	    compute_data_key(this->encryption_key, objid, generation,
+			     this->encryption_use_aes);
 	this->cached_key_objid = objid;
 	this->cached_key_generation = generation;
     }
@@ -424,8 +457,15 @@ QPDF::decryptStream(Pipeline*&amp; pipeline, int objid, int generation,
 		    std::vector<PointerHolder<Pipeline> >& heap)
 {
     std::string key = getKeyForObject(objid, generation);
-    pipeline = new Pl_RC4("stream decryption", pipeline,
-			  (unsigned char*) key.c_str(), key.length());
+    if (this->encryption_use_aes)
+    {
+	throw std::logic_error("aes not yet implemented"); // XXX
+    }
+    else
+    {
+	pipeline = new Pl_RC4("RC4 stream decryption", pipeline,
+			      (unsigned char*) key.c_str(), key.length());
+    }
     heap.push_back(pipeline);
 }
  
@@ -435,7 +475,8 @@ QPDF::compute_encryption_O_U(
     int V, int R, int key_len, int P,
     std::string const& id1, std::string& O, std::string& U)
 {
-    EncryptionData data(V, R, key_len, P, "", "", id1);
+    EncryptionData data(V, R, key_len, P, "", "", id1,
+			/*XXX encrypt_metadata*/true);
     data.O = compute_O_value(user_password, owner_password, data);
     O = data.O;
     U = compute_U_value(user_password, data);
@@ -13,6 +13,7 @@ SRCS_libqpdf = \
 	libqpdf/MD5.cc \
 	libqpdf/PCRE.cc \
 	libqpdf/Pipeline.cc \
+	libqpdf/Pl_AES_PDF.cc \
 	libqpdf/Pl_ASCII85Decoder.cc \
 	libqpdf/Pl_ASCIIHexDecoder.cc \
 	libqpdf/Pl_Buffer.cc \
+#ifndef __PL_AES_PDF_HH__
+#define __PL_AES_PDF_HH__
+
+#include <qpdf/Pipeline.hh>
+
+class DLL_EXPORT Pl_AES_PDF: public Pipeline
+{
+  public:
+    // 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_data);
+    virtual ~Pl_AES_PDF();
+
+    virtual void write(unsigned char* data, int len);
+    virtual void finish();
+
+  private:
+    void flush(bool discard_padding);
+
+    bool encrypt;
+    unsigned int offset;
+    static unsigned int const buf_size = 16;
+    unsigned char buf[buf_size];
+};
+
+#endif // __PL_AES_PDF_HH__
+#include <qpdf/Pl_AES_PDF.hh>
+#include <qpdf/Pl_StdioFile.hh>
+
+#include <stdio.h>
+#include <string.h>
+#include <iostream>
+#include <stdlib.h>
+
+static void usage()
+{
+    std::cerr << "Usage: aes { -encrypt | -decrypt }"
+	      << " hex-key infile outfile" << std::endl;
+    exit(2);
+}
+
+int main(int argc, char* argv[])
+{
+    if (argc != 5)
+    {
+	usage();
+   }
+
+    char* action = argv[1];
+    char* hexkey = argv[2];
+    char* infilename = argv[3];
+    char* outfilename = argv[4];
+
+    bool encrypt = true;
+    if (strcmp(action, "-decrypt") == 0)
+    {
+	encrypt = false;
+    }
+    else if (strcmp(action, "-encrypt") != 0)
+    {
+	usage();
+    }
+
+    unsigned int hexkeylen = strlen(hexkey);
+    unsigned int keylen = hexkeylen / 2;
+    if (keylen != Pl_AES_PDF::key_size)
+    {
+	std::cerr << "key length must be " << Pl_AES_PDF::key_size
+		  << " bytes" << std::endl;
+	exit(2);
+    }
+
+    FILE* infile = fopen(infilename, "rb");
+    if (infile == 0)
+    {
+	std::cerr << "can't open " << infilename << std::endl;
+	exit(2);
+    }
+
+    FILE* outfile = fopen(outfilename, "wb");
+    if (outfile == 0)
+    {
+	std::cerr << "can't open " << outfilename << std::endl;
+	exit(2);
+    }
+
+    unsigned char key[Pl_AES_PDF::key_size];
+    for (unsigned int i = 0; i < strlen(hexkey); i += 2)
+    {
+	char t[3];
+	t[0] = hexkey[i];
+	t[1] = hexkey[i + 1];
+	t[2] = '\0';
+
+	long val = strtol(t, 0, 16);
+	key[i/2] = (unsigned char) val;
+    }
+
+    Pl_StdioFile* out = new Pl_StdioFile("stdout", outfile);
+    Pl_AES_PDF* aes = new Pl_AES_PDF("aes_128_cbc", out, encrypt, key);
+
+    // 16 < buffer size, buffer_size is not a multiple of 8 for testing
+    unsigned char buf[83];
+    bool done = false;
+    while (! done)
+    {
+	int len = fread(buf, 1, sizeof(buf), infile);
+	if (len <= 0)
+	{
+	    done = true;
+	}
+	else
+	{
+	    aes->write(buf, len);
+	}
+    }
+    aes->finish();
+    delete aes;
+    delete out;
+    fclose(infile);
+    fclose(outfile);
+    return 0;
+}
 BINS_libtests = \
+	aes \
 	ascii85 \
 	bits \
 	buffer \