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#include <qpdf/Pl_AES_PDF.hh>
#include <qpdf/QUtil.hh>
#include <cstring>
#include <assert.h>
#include <stdexcept>
#include <qpdf/rijndael.h>
#include <string>
#include <stdlib.h>
#include <qpdf/qpdf-config.h>
#ifndef HAVE_RANDOM
# define random rand
# define srandom srand
#endif
bool Pl_AES_PDF::use_static_iv = false;
Pl_AES_PDF::Pl_AES_PDF(char const* identifier, Pipeline* next,
bool encrypt, unsigned char const key[key_size]) :
Pipeline(identifier, next),
encrypt(encrypt),
cbc_mode(true),
first(true),
offset(0),
nrounds(0)
{
static int const keybits = 128;
assert(key_size == KEYLENGTH(keybits));
assert(sizeof(this->rk) / sizeof(uint32_t) == RKLENGTH(keybits));
std::memcpy(this->key, key, key_size);
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);
}
else
{
this->nrounds = rijndaelSetupDecrypt(this->rk, this->key, keybits);
}
assert(this->nrounds == NROUNDS(keybits));
}
Pl_AES_PDF::~Pl_AES_PDF()
{
// nothing needed
}
void
Pl_AES_PDF::disableCBC()
{
this->cbc_mode = false;
}
void
Pl_AES_PDF::useStaticIV()
{
use_static_iv = true;
}
void
Pl_AES_PDF::write(unsigned char* data, size_t len)
{
size_t bytes_left = len;
unsigned char* p = data;
while (bytes_left > 0)
{
if (this->offset == this->buf_size)
{
flush(false);
}
size_t available = this->buf_size - this->offset;
size_t bytes = (bytes_left < available ? bytes_left : available);
bytes_left -= bytes;
std::memcpy(this->inbuf + 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 = (unsigned char) (this->buf_size - this->offset);
memset(this->inbuf + this->offset, pad, pad);
this->offset = this->buf_size;
flush(false);
}
else
{
if (this->offset != this->buf_size)
{
// This is never supposed to happen as the output is
// always supposed to be padded. However, we have
// encountered files for which the output is not a
// multiple of the block size. In this case, pad with
// zeroes and hope for the best.
assert(this->buf_size > this->offset);
std::memset(this->inbuf + this->offset, 0,
this->buf_size - this->offset);
this->offset = this->buf_size;
}
flush(true);
}
getNext()->finish();
}
void
Pl_AES_PDF::initializeVector()
{
static bool seeded_random = false;
if (! seeded_random)
{
// Seed the random number generator with something simple, but
// just to be interesting, don't use the unmodified current
// time....
srandom((int)QUtil::get_current_time() ^ 0xcccc);
seeded_random = true;
}
if (use_static_iv)
{
for (unsigned int i = 0; i < this->buf_size; ++i)
{
this->cbc_block[i] = 14 * (1 + i);
}
}
else
{
for (unsigned int i = 0; i < this->buf_size; ++i)
{
this->cbc_block[i] = (unsigned char)((random() & 0xff0) >> 4);
}
}
}
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)
{
unsigned char last = this->outbuf[this->buf_size - 1];
if (last <= this->buf_size)
{
bool strip = true;
for (unsigned int i = 1; i <= last; ++i)
{
if (this->outbuf[this->buf_size - i] != last)
{
strip = false;
break;
}
}
if (strip)
{
bytes -= last;
}
}
}
getNext()->write(this->outbuf, bytes);
this->offset = 0;
}
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