Pl_AES_PDF.cc
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#include <qpdf/Pl_AES_PDF.hh>
#include <qpdf/QIntC.hh>
#include <qpdf/QPDFCryptoProvider.hh>
#include <qpdf/QUtil.hh>
#include <cstring>
#include <stdexcept>
#include <string>
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,
size_t key_bytes) :
Pipeline(identifier, next),
crypto(QPDFCryptoProvider::getImpl()),
encrypt(encrypt),
key_bytes(key_bytes)
{
if (!next) {
throw std::logic_error("Attempt to create Pl_AES_PDF with nullptr as next");
}
if (!(key_bytes == 32 || key_bytes == 16)) {
throw std::runtime_error("unsupported key length");
}
this->key = std::make_unique<unsigned char[]>(key_bytes);
std::memcpy(this->key.get(), key, key_bytes);
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);
}
void
Pl_AES_PDF::useZeroIV()
{
use_zero_iv = true;
}
void
Pl_AES_PDF::disablePadding()
{
disable_padding = true;
}
void
Pl_AES_PDF::setIV(unsigned char const* iv, size_t bytes)
{
if (bytes != buf_size) {
throw std::logic_error(
"Pl_AES_PDF: specified initialization vector"
" size in bytes must be " +
std::to_string(bytes));
}
use_specified_iv = true;
memcpy(specified_iv, iv, bytes);
}
void
Pl_AES_PDF::disableCBC()
{
cbc_mode = false;
}
void
Pl_AES_PDF::useStaticIV()
{
use_static_iv = true;
}
void
Pl_AES_PDF::write(unsigned char const* data, size_t len)
{
size_t bytes_left = len;
unsigned char const* p = data;
while (bytes_left > 0) {
if (offset == buf_size) {
flush(false);
}
size_t available = buf_size - offset;
size_t bytes = (bytes_left < available ? bytes_left : available);
bytes_left -= bytes;
std::memcpy(inbuf + offset, p, bytes);
offset += bytes;
p += bytes;
}
}
void
Pl_AES_PDF::finish()
{
if (encrypt) {
if (offset == buf_size) {
flush(false);
}
if (!disable_padding) {
// 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 = QIntC::to_uchar(buf_size - offset);
memset(inbuf + offset, pad, pad);
offset = buf_size;
flush(false);
}
} else {
if (offset != 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.
if (offset >= buf_size) {
throw std::logic_error("buffer overflow in AES encryption pipeline");
}
std::memset(inbuf + offset, 0, buf_size - offset);
offset = buf_size;
}
flush(!disable_padding);
}
crypto->rijndael_finalize();
next()->finish();
}
void
Pl_AES_PDF::initializeVector()
{
if (use_zero_iv) {
for (unsigned int i = 0; i < buf_size; ++i) {
cbc_block[i] = 0;
}
} else if (use_specified_iv) {
std::memcpy(cbc_block, specified_iv, buf_size);
} else if (use_static_iv) {
for (unsigned int i = 0; i < buf_size; ++i) {
cbc_block[i] = static_cast<unsigned char>(14U * (1U + i));
}
} else {
QUtil::initializeWithRandomBytes(cbc_block, buf_size);
}
}
void
Pl_AES_PDF::flush(bool strip_padding)
{
if (offset != buf_size) {
throw std::logic_error("AES pipeline: flush called when buffer was not full");
}
if (first) {
first = false;
bool return_after_init = false;
if (cbc_mode) {
if (encrypt) {
// Set cbc_block to the initialization vector, and if not zero, write it to the
// output stream.
initializeVector();
if (!(use_zero_iv || use_specified_iv)) {
next()->write(cbc_block, buf_size);
}
} else if (use_zero_iv || use_specified_iv) {
// Initialize vector with zeroes; zero vector was not written to the beginning of
// the input file.
initializeVector();
} else {
// Take the first block of input as the initialization vector. There's nothing to
// write at this time.
memcpy(cbc_block, inbuf, buf_size);
offset = 0;
return_after_init = true;
}
}
crypto->rijndael_init(encrypt, key.get(), key_bytes, cbc_mode, cbc_block);
if (return_after_init) {
return;
}
}
crypto->rijndael_process(inbuf, outbuf);
unsigned int bytes = buf_size;
if (strip_padding) {
unsigned char last = outbuf[buf_size - 1];
if (last <= buf_size) {
bool strip = true;
for (unsigned int i = 1; i <= last; ++i) {
if (outbuf[buf_size - i] != last) {
strip = false;
break;
}
}
if (strip) {
bytes -= last;
}
}
}
offset = 0;
next()->write(outbuf, bytes);
}