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checkpoint -- partially implemented /V=4 encryption

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git-svn-id: svn+q:///qpdf/trunk@811 71b93d88-0707-0410-a8cf-f5a4172ac649
This commit is contained in:
Jay Berkenbilt 2009-10-17 18:54:51 +00:00
parent 27e8d4bbff
commit c13bc66de8
7 changed files with 210 additions and 72 deletions
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65
TODO
View File

@ -43,6 +43,49 @@
(http://delphi.about.com). .. use at your own risk and for whatever
the purpose you want .. no support provided. Sample code provided."
* Implement as much of R = 4 encryption as possible. Already able to
decode AES-128-CBC and check passwords.
aes test suite: use fips-197 test vector with cbc disabled; encrypt
and decrypt some other files including multiples of 16 and not to
test cbc mode.
/Encrypt keys (if V == 4)
/StmF - name of crypt filter for streams; default /Identity
/StrF - name of crypt filter for strings; default /Identity
/EFF - crypt filter for embedded files without their own crypt
filters; default is to use /StmF
/CF - keys are crypt filter names, values are are crypt
dictionaries
Individual streams may also have crypt filters. Filter type
/Crypt; /DecodeParms must contain a Crypt filter decode
parameters dictionary whose /Name entry specifies the particular
filter to be used. If /Name is missing, use /Identity.
/DecodeParms << /Crypt << /Name /XYZ >> >> where /XYZ is
/Identity or a key in /CF.
/Identity means not to encrypt.
Crypt Dictionaries
/Type (optional) /CryptFilter
/CFM:
/V2 - use rc4
/AESV2 - use aes
/Length - supposed to be key length, but the one file I have
has a bogus value for it, so I'm ignoring it.
We will ignore remaining fields and values.
Remember to honor /EncryptMetadata; applies to streams of /Type
/Metadata
When we write encrypted files, we must remember to omit any
encryption filter settings from original streams.
2.2
===
@ -52,22 +95,6 @@
Stefan Heinsen <stefan.heinsen@gmx.de> in August, 2009. He seems
to like to send encrypted mail. (key 01FCC336)
* See whether we can do anything with /V > 3 in the encryption
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.
@ -109,9 +136,9 @@ General
of doing this seems very low since no viewer seems to care, so it's
probably not worth it.
* Embedded files streams: figure out why running qpdf over the pdf
1.7 spec results in a file that crashes acrobat reader when you try
to save nested documents.
* Embedded file streams: figure out why running qpdf over the pdf 1.7
spec results in a file that crashes acrobat reader when you try to
save nested documents.
* QPDFObjectHandle::getPageImages() doesn't notice images in
inherited resource dictionaries. See comments in that function.

14
include/qpdf/QPDF.hh
View File

@ -141,7 +141,7 @@ class DLL_EXPORT QPDF
static void compute_encryption_O_U(
char const* user_password, char const* owner_password,
int V, int R, int key_len, int P,
int V, int R, int key_len, int P, bool encrypt_metadata,
std::string const& id1,
std::string& O, std::string& U);
// Return the full user password as stored in the PDF file. If
@ -398,10 +398,12 @@ class DLL_EXPORT QPDF
// methods to support encryption -- implemented in QPDF_encryption.cc
void initializeEncryption();
std::string getKeyForObject(int objid, int generation);
std::string getKeyForObject(int objid, int generation, bool use_aes);
void decryptString(std::string&, int objid, int generation);
void decryptStream(Pipeline*& pipeline, int objid, int generation,
std::vector<PointerHolder<Pipeline> >& heap);
void decryptStream(
Pipeline*& pipeline, int objid, int generation,
QPDFObjectHandle& stream_dict,
std::vector<PointerHolder<Pipeline> >& heap);
// Linearization Hint table structures.
// Naming conventions:
@ -735,7 +737,9 @@ class DLL_EXPORT QPDF
bool ignore_xref_streams;
bool suppress_warnings;
bool attempt_recovery;
bool encryption_use_aes;
int encryption_V;
bool encrypt_metadata;
QPDFObjectHandle encryption_dictionary;
std::string provided_password;
std::string user_password;
std::string encryption_key;

77
libqpdf/Pl_AES_PDF.cc
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@ -1,16 +1,19 @@
#include <qpdf/Pl_AES_PDF.hh>
#include <qpdf/QUtil.hh>
#include <qpdf/MD5.hh>
#include <cstring>
#include <assert.h>
#include <stdexcept>
#include <qpdf/rijndael.h>
// XXX Still need CBC
#include <string>
#include <stdlib.h>
Pl_AES_PDF::Pl_AES_PDF(char const* identifier, Pipeline* next,
bool encrypt, unsigned char key[key_size]) :
Pipeline(identifier, next),
encrypt(encrypt),
cbc_mode(true),
first(true),
offset(0),
nrounds(0)
{
@ -21,6 +24,7 @@ Pl_AES_PDF::Pl_AES_PDF(char const* identifier, Pipeline* next,
std::memset(this->rk, 0, sizeof(this->rk));
std::memset(this->inbuf, 0, this->buf_size);
std::memset(this->outbuf, 0, this->buf_size);
std::memset(this->cbc_block, 0, this->buf_size);
if (encrypt)
{
this->nrounds = rijndaelSetupEncrypt(this->rk, this->key, keybits);
@ -37,6 +41,12 @@ Pl_AES_PDF::~Pl_AES_PDF()
// nothing needed
}
void
Pl_AES_PDF::disableCBC()
{
this->cbc_mode = false;
}
void
Pl_AES_PDF::write(unsigned char* data, int len)
{
@ -90,17 +100,80 @@ Pl_AES_PDF::finish()
getNext()->finish();
}
void
Pl_AES_PDF::initializeVector()
{
std::string seed_str;
seed_str += QUtil::int_to_string((int)QUtil::get_current_time());
seed_str += " QPDF aes random";
MD5 m;
m.encodeString(seed_str.c_str());
MD5::Digest digest;
m.digest(digest);
assert(sizeof(digest) >= sizeof(unsigned int));
unsigned int seed;
memcpy((void*)(&seed), digest, sizeof(unsigned int));
srandom(seed);
for (unsigned int i = 0; i < this->buf_size; ++i)
{
this->cbc_block[i] = (unsigned char)(random() & 0xff);
}
}
void
Pl_AES_PDF::flush(bool strip_padding)
{
assert(this->offset == this->buf_size);
if (first)
{
first = false;
if (this->cbc_mode)
{
if (encrypt)
{
// Set cbc_block to a random initialization vector and
// write it to the output stream
initializeVector();
getNext()->write(this->cbc_block, this->buf_size);
}
else
{
// Take the first block of input as the initialization
// vector. There's nothing to write at this time.
memcpy(this->cbc_block, this->inbuf, this->buf_size);
this->offset = 0;
return;
}
}
}
if (this->encrypt)
{
if (this->cbc_mode)
{
for (unsigned int i = 0; i < this->buf_size; ++i)
{
this->inbuf[i] ^= this->cbc_block[i];
}
}
rijndaelEncrypt(this->rk, this->nrounds, this->inbuf, this->outbuf);
if (this->cbc_mode)
{
memcpy(this->cbc_block, this->outbuf, this->buf_size);
}
}
else
{
rijndaelDecrypt(this->rk, this->nrounds, this->inbuf, this->outbuf);
if (this->cbc_mode)
{
for (unsigned int i = 0; i < this->buf_size; ++i)
{
this->outbuf[i] ^= this->cbc_block[i];
}
memcpy(this->cbc_block, this->inbuf, this->buf_size);
}
}
unsigned int bytes = this->buf_size;
if (strip_padding)

15
libqpdf/QPDF.cc
View File

@ -253,7 +253,8 @@ QPDF::QPDF() :
ignore_xref_streams(false),
suppress_warnings(false),
attempt_recovery(true),
encryption_use_aes(false),
encryption_V(0),
encrypt_metadata(true),
cached_key_objid(0),
cached_key_generation(0),
first_xref_item_offset(0),
@ -1813,17 +1814,7 @@ QPDF::pipeStreamData(int objid, int generation,
std::vector<PointerHolder<Pipeline> > to_delete;
if (this->encrypted)
{
bool xref_stream = false;
if (stream_dict.getKey("/Type").isName() &&
(stream_dict.getKey("/Type").getName() == "/XRef"))
{
QTC::TC("qpdf", "QPDF piping xref stream from encrypted file");
xref_stream = true;
}
if (! xref_stream)
{
decryptStream(pipeline, objid, generation, to_delete);
}
decryptStream(pipeline, objid, generation, stream_dict, to_delete);
}
try

3
libqpdf/QPDFWriter.cc
View File

@ -281,7 +281,8 @@ QPDFWriter::setEncryptionParameters(
std::string O;
std::string U;
QPDF::compute_encryption_O_U(
user_password, owner_password, V, R, key_len, P, this->id1, O, U);
user_password, owner_password, V, R, key_len, P,
/*XXX encrypt_metadata*/true, this->id1, O, U);
setEncryptionParametersInternal(
V, R, key_len, P, O, U, this->id1, user_password);
}

101
libqpdf/QPDF_encryption.cc
View File

@ -5,11 +5,14 @@
#include <qpdf/QPDFExc.hh>
#include <qpdf/QTC.hh>
#include <qpdf/QUtil.hh>
#include <qpdf/Pl_RC4.hh>
#include <qpdf/Pl_AES_PDF.hh>
#include <qpdf/RC4.hh>
#include <qpdf/MD5.hh>
#include <assert.h>
#include <string.h>
static char const padding_string[] = {
@ -123,9 +126,6 @@ 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
@ -322,7 +322,8 @@ QPDF::initializeEncryption()
"incorrect length");
}
QPDFObjectHandle encryption_dict = this->trailer.getKey("/Encrypt");
this->encryption_dictionary = this->trailer.getKey("/Encrypt");
QPDFObjectHandle& encryption_dict = this->encryption_dictionary;
if (! encryption_dict.isDictionary())
{
throw QPDFExc(this->file.getName(), this->file.getLastOffset(),
@ -360,12 +361,7 @@ QPDF::initializeEncryption()
"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");
}
this->encryption_V = V;
if (! ((O.length() == key_bytes) && (U.length() == key_bytes)))
{
@ -385,19 +381,21 @@ QPDF::initializeEncryption()
}
}
bool encrypt_metadata = true;
this->encrypt_metadata = true;
if ((V >= 4) && (encryption_dict.getKey("/EncryptMetadata").isBool()))
{
encrypt_metadata =
this->encrypt_metadata =
encryption_dict.getKey("/EncryptMetadata").getBoolValue();
}
// XXX not really...
if (R >= 4)
// XXX warn if /SubFilter is present
if (V == 4)
{
this->encryption_use_aes = true;
// XXX get CF
}
EncryptionData data(V, R, Length / 8, P, O, U, id1, encrypt_metadata);
if (check_owner_password(this->user_password, this->provided_password, data))
EncryptionData data(V, R, Length / 8, P, O, U, id1, this->encrypt_metadata);
if (check_owner_password(
this->user_password, this->provided_password, data))
{
// password supplied was owner password; user_password has
// been initialized
@ -415,7 +413,7 @@ QPDF::initializeEncryption()
}
std::string
QPDF::getKeyForObject(int objid, int generation)
QPDF::getKeyForObject(int objid, int generation, bool use_aes)
{
if (! this->encrypted)
{
@ -427,8 +425,7 @@ QPDF::getKeyForObject(int objid, int generation)
(generation == this->cached_key_generation)))
{
this->cached_object_encryption_key =
compute_data_key(this->encryption_key, objid, generation,
this->encryption_use_aes);
compute_data_key(this->encryption_key, objid, generation, use_aes);
this->cached_key_objid = objid;
this->cached_key_generation = generation;
}
@ -443,23 +440,62 @@ QPDF::decryptString(std::string& str, int objid, int generation)
{
return;
}
std::string key = getKeyForObject(objid, generation);
char* tmp = QUtil::copy_string(str);
unsigned int vlen = str.length();
RC4 rc4((unsigned char const*)key.c_str(), key.length());
rc4.process((unsigned char*)tmp, vlen);
str = std::string(tmp, vlen);
delete [] tmp;
bool use_aes = false; // XXX
std::string key = getKeyForObject(objid, generation, use_aes);
if (use_aes)
{
// XXX
throw std::logic_error("XXX");
}
else
{
unsigned int vlen = str.length();
char* tmp = QUtil::copy_string(str);
RC4 rc4((unsigned char const*)key.c_str(), key.length());
rc4.process((unsigned char*)tmp, vlen);
str = std::string(tmp, vlen);
delete [] tmp;
}
}
void
QPDF::decryptStream(Pipeline*& pipeline, int objid, int generation,
QPDFObjectHandle& stream_dict,
std::vector<PointerHolder<Pipeline> >& heap)
{
std::string key = getKeyForObject(objid, generation);
if (this->encryption_use_aes)
bool decrypt = true;
std::string type;
if (stream_dict.getKey("/Type").isName())
{
throw std::logic_error("aes not yet implemented"); // XXX
type = stream_dict.getKey("/Type").getName();
}
if (type == "/XRef")
{
QTC::TC("qpdf", "QPDF piping xref stream from encrypted file");
decrypt = false;
}
bool use_aes = false;
if (this->encryption_V == 4)
{
if ((! this->encrypt_metadata) && (type == "/Metadata"))
{
// XXX no test case for this
decrypt = false;
}
// XXX check crypt filter; if not found, use StmF; see TODO
use_aes = true; // XXX
}
if (! decrypt)
{
return;
}
std::string key = getKeyForObject(objid, generation, use_aes);
if (use_aes)
{
assert(key.length() == Pl_AES_PDF::key_size);
pipeline = new Pl_AES_PDF("AES stream decryption", pipeline,
false, (unsigned char*) key.c_str());
}
else
{
@ -472,11 +508,10 @@ QPDF::decryptStream(Pipeline*& pipeline, int objid, int generation,
void
QPDF::compute_encryption_O_U(
char const* user_password, char const* owner_password,
int V, int R, int key_len, int P,
int V, int R, int key_len, int P, bool encrypt_metadata,
std::string const& id1, std::string& O, std::string& U)
{
EncryptionData data(V, R, key_len, P, "", "", id1,
/*XXX encrypt_metadata*/true);
EncryptionData data(V, R, key_len, P, "", "", id1, encrypt_metadata);
data.O = compute_O_value(user_password, owner_password, data);
O = data.O;
U = compute_U_value(user_password, data);

7
libqpdf/qpdf/Pl_AES_PDF.hh
View File

@ -18,17 +18,24 @@ class DLL_EXPORT Pl_AES_PDF: public Pipeline
virtual void write(unsigned char* data, int len);
virtual void finish();
// For testing only; PDF always uses CBC
void disableCBC();
private:
void flush(bool discard_padding);
void initializeVector();
static unsigned int const buf_size = 16;
bool encrypt;
bool cbc_mode;
bool first;
unsigned int offset;
unsigned char key[key_size];
uint32_t rk[key_size + 28];
unsigned char inbuf[buf_size];
unsigned char outbuf[buf_size];
unsigned char cbc_block[buf_size];
unsigned int nrounds;
};