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checkpoint -- started doing some R4 encryption support

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git-svn-id: svn+q:///qpdf/trunk@807 71b93d88-0707-0410-a8cf-f5a4172ac649
This commit is contained in:
Jay Berkenbilt 2009-10-17 03:14:47 +00:00
parent ad19b03fd3
commit 846c9f6bcc
11 changed files with 352 additions and 31 deletions
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36
README
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@ -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.

12
TODO
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@ -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.

10
include/qpdf/QPDF.hh
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@ -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;

110
libqpdf/Pl_AES_PDF.cc Normal file
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@ -0,0 +1,110 @@
#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;
}

1
libqpdf/QPDF.cc
View File

@ -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),

5
libqpdf/QPDFWriter.cc
View File

@ -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

83
libqpdf/QPDF_encryption.cc
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@ -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& 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& 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& 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& 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& 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& 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*& 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);

1
libqpdf/build.mk
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@ -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 \

27
libqpdf/qpdf/Pl_AES_PDF.hh Normal file
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@ -0,0 +1,27 @@
#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__

97
libtests/aes.cc Normal file
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@ -0,0 +1,97 @@
#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;
}

1
libtests/build.mk
View File

@ -1,4 +1,5 @@
BINS_libtests = \
aes \
ascii85 \
bits \
buffer \