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qpdf/libqpdf/QPDF_encryption.cc
Jay Berkenbilt 5d9d80beba Fix fallback logic for encryption (fixes #229)
2018-08-12 22:32:40 -04:00

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// This file implements methods from the QPDF class that involve
// encryption.
#include <qpdf/QPDF.hh>
#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/Pl_Buffer.hh>
#include <qpdf/Pl_SHA2.hh>
#include <qpdf/RC4.hh>
#include <qpdf/MD5.hh>
#include <algorithm>
#include <assert.h>
#include <string.h>
static unsigned char const padding_string[] = {
0x28, 0xbf, 0x4e, 0x5e, 0x4e, 0x75, 0x8a, 0x41,
0x64, 0x00, 0x4e, 0x56, 0xff, 0xfa, 0x01, 0x08,
0x2e, 0x2e, 0x00, 0xb6, 0xd0, 0x68, 0x3e, 0x80,
0x2f, 0x0c, 0xa9, 0xfe, 0x64, 0x53, 0x69, 0x7a
};
static unsigned int const key_bytes = 32;
// V4 key lengths apply to V <= 4
static unsigned int const OU_key_bytes_V4 = sizeof(MD5::Digest);
static unsigned int const OU_key_bytes_V5 = 48;
static unsigned int const OUE_key_bytes_V5 = 32;
static unsigned int const Perms_key_bytes_V5 = 16;
int
QPDF::EncryptionData::getV() const
{
return this->V;
}
int
QPDF::EncryptionData::getR() const
{
return this->R;
}
int
QPDF::EncryptionData::getLengthBytes() const
{
return this->Length_bytes;
}
int
QPDF::EncryptionData::getP() const
{
return this->P;
}
std::string const&
QPDF::EncryptionData::getO() const
{
return this->O;
}
std::string const&
QPDF::EncryptionData::getU() const
{
return this->U;
}
std::string const&
QPDF::EncryptionData::getOE() const
{
return this->OE;
}
std::string const&
QPDF::EncryptionData::getUE() const
{
return this->UE;
}
std::string const&
QPDF::EncryptionData::getPerms() const
{
return this->Perms;
}
std::string const&
QPDF::EncryptionData::getId1() const
{
return this->id1;
}
bool
QPDF::EncryptionData::getEncryptMetadata() const
{
return this->encrypt_metadata;
}
void
QPDF::EncryptionData::setO(std::string const& O)
{
this->O = O;
}
void
QPDF::EncryptionData::setU(std::string const& U)
{
this->U = U;
}
void
QPDF::EncryptionData::setV5EncryptionParameters(
std::string const& O,
std::string const& OE,
std::string const& U,
std::string const& UE,
std::string const& Perms)
{
this->O = O;
this->OE = OE;
this->U = U;
this->UE = UE;
this->Perms = Perms;
}
static void
pad_or_truncate_password_V4(std::string const& password, char k1[key_bytes])
{
int password_bytes = std::min(static_cast<size_t>(key_bytes),
password.length());
int pad_bytes = key_bytes - password_bytes;
memcpy(k1, password.c_str(), password_bytes);
memcpy(k1 + password_bytes, padding_string, pad_bytes);
}
void
QPDF::trim_user_password(std::string& user_password)
{
// Although unnecessary, this routine trims the padding string
// from the end of a user password. Its only purpose is for
// recovery of user passwords which is done in the test suite.
char const* cstr = user_password.c_str();
size_t len = user_password.length();
if (len < key_bytes)
{
return;
}
char const* p1 = cstr;
char const* p2 = 0;
while ((p2 = strchr(p1, '\x28')) != 0)
{
if (memcmp(p2, padding_string, len - (p2 - cstr)) == 0)
{
user_password = user_password.substr(0, p2 - cstr);
return;
}
else
{
QTC::TC("qpdf", "QPDF_encryption skip 0x28");
p1 = p2 + 1;
}
}
}
static std::string
pad_or_truncate_password_V4(std::string const& password)
{
char k1[key_bytes];
pad_or_truncate_password_V4(password, k1);
return std::string(k1, key_bytes);
}
static std::string
truncate_password_V5(std::string const& password)
{
return password.substr(
0, std::min(static_cast<size_t>(127), password.length()));
}
static void
iterate_md5_digest(MD5& md5, MD5::Digest& digest, int iterations, int key_len)
{
md5.digest(digest);
for (int i = 0; i < iterations; ++i)
{
MD5 m;
m.encodeDataIncrementally(reinterpret_cast<char*>(digest),
key_len);
m.digest(digest);
}
}
static void
iterate_rc4(unsigned char* data, int data_len,
unsigned char* okey, int key_len,
int iterations, bool reverse)
{
unsigned char* key = new unsigned char[key_len];
for (int i = 0; i < iterations; ++i)
{
int const xor_value = (reverse ? iterations - 1 - i : i);
for (int j = 0; j < key_len; ++j)
{
key[j] = okey[j] ^ xor_value;
}
RC4 rc4(key, key_len);
rc4.process(data, data_len);
}
delete [] key;
}
static std::string
process_with_aes(std::string const& key,
bool encrypt,
std::string const& data,
size_t outlength = 0,
unsigned int repetitions = 1,
unsigned char const* iv = 0,
size_t iv_length = 0)
{
Pl_Buffer buffer("buffer");
Pl_AES_PDF aes("aes", &buffer, encrypt,
QUtil::unsigned_char_pointer(key),
key.length());
if (iv)
{
aes.setIV(iv, iv_length);
}
else
{
aes.useZeroIV();
}
aes.disablePadding();
for (unsigned int i = 0; i < repetitions; ++i)
{
aes.write(QUtil::unsigned_char_pointer(data), data.length());
}
aes.finish();
PointerHolder<Buffer> bufp = buffer.getBuffer();
if (outlength == 0)
{
outlength = bufp->getSize();
}
else
{
outlength = std::min(outlength, bufp->getSize());
}
return std::string(reinterpret_cast<char*>(bufp->getBuffer()), outlength);
}
static std::string
hash_V5(std::string const& password,
std::string const& salt,
std::string const& udata,
QPDF::EncryptionData const& data)
{
Pl_SHA2 hash(256);
hash.write(QUtil::unsigned_char_pointer(password), password.length());
hash.write(QUtil::unsigned_char_pointer(salt), salt.length());
hash.write(QUtil::unsigned_char_pointer(udata), udata.length());
hash.finish();
std::string K = hash.getRawDigest();
std::string result;
if (data.getR() < 6)
{
result = K;
}
else
{
// Algorithm 2.B from ISO 32000-1 chapter 7: Computing a hash
int round_number = 0;
bool done = false;
while (! done)
{
// The hash algorithm has us setting K initially to the R5
// value and then repeating a series of steps 64 times
// before starting with the termination case testing. The
// wording of the specification is very unclear as to the
// exact number of times it should be run since the
// wording about whether the initial setup counts as round
// 0 or not is ambiguous. This code counts the initial
// setup (R5) value as round 0, which appears to be
// correct. This was determined to be correct by
// increasing or decreasing the number of rounds by 1 or 2
// from this value and generating 20 test files. In this
// interpretation, all the test files worked with Adobe
// Reader X. In the other configurations, many of the
// files did not work, and we were accurately able to
// predict which files didn't work by looking at the
// conditions under which we terminated repetition.
++round_number;
std::string K1 = password + K + udata;
assert(K.length() >= 32);
std::string E = process_with_aes(
K.substr(0, 16), true, K1, 0, 64,
QUtil::unsigned_char_pointer(K.substr(16, 16)), 16);
// E_mod_3 is supposed to be mod 3 of the first 16 bytes
// of E taken as as a (128-bit) big-endian number. Since
// (xy mod n) is equal to ((x mod n) + (y mod n)) mod n
// and since 256 mod n is 1, we can just take the sums of
// the the mod 3s of each byte to get the same result.
int E_mod_3 = 0;
for (unsigned int i = 0; i < 16; ++i)
{
E_mod_3 += static_cast<unsigned char>(E.at(i));
}
E_mod_3 %= 3;
int next_hash = ((E_mod_3 == 0) ? 256 :
(E_mod_3 == 1) ? 384 :
512);
Pl_SHA2 hash(next_hash);
hash.write(QUtil::unsigned_char_pointer(E), E.length());
hash.finish();
K = hash.getRawDigest();
if (round_number >= 64)
{
unsigned int ch = static_cast<unsigned char>(*(E.rbegin()));
if (ch <= static_cast<unsigned int>(round_number - 32))
{
done = true;
}
}
}
result = K.substr(0, 32);
}
return result;
}
static
void pad_short_parameter(std::string& param, unsigned int max_len)
{
if (param.length() < max_len)
{
QTC::TC("qpdf", "QPDF_encryption pad short parameter");
param.append(max_len - param.length(), '\0');
}
}
std::string
QPDF::compute_data_key(std::string const& encryption_key,
int objid, int generation, bool use_aes,
int encryption_V, int encryption_R)
{
// Algorithm 3.1 from the PDF 1.7 Reference Manual
std::string result = encryption_key;
if (encryption_V >= 5)
{
// Algorithm 3.1a (PDF 1.7 extension level 3): just use
// encryption key straight.
return result;
}
// Append low three bytes of object ID and low two bytes of generation
result += static_cast<char>(objid & 0xff);
result += static_cast<char>((objid >> 8) & 0xff);
result += static_cast<char>((objid >> 16) & 0xff);
result += static_cast<char>(generation & 0xff);
result += static_cast<char>((generation >> 8) & 0xff);
if (use_aes)
{
result += "sAlT";
}
MD5 md5;
md5.encodeDataIncrementally(result.c_str(), result.length());
MD5::Digest digest;
md5.digest(digest);
return std::string(reinterpret_cast<char*>(digest),
std::min(result.length(), static_cast<size_t>(16)));
}
std::string
QPDF::compute_encryption_key(
std::string const& password, EncryptionData const& data)
{
if (data.getV() >= 5)
{
// For V >= 5, the encryption key is generated and stored in
// the file, encrypted separately with both user and owner
// passwords.
return recover_encryption_key_with_password(password, data);
}
else
{
// For V < 5, the encryption key is derived from the user
// password.
return compute_encryption_key_from_password(password, data);
}
}
std::string
QPDF::compute_encryption_key_from_password(
std::string const& password, EncryptionData const& data)
{
// Algorithm 3.2 from the PDF 1.7 Reference Manual
// This code does not properly handle Unicode passwords.
// Passwords are supposed to be converted from OS codepage
// characters to PDFDocEncoding. Unicode passwords are supposed
// to be converted to OS codepage before converting to
// PDFDocEncoding. We instead require the password to be
// presented in its final form.
MD5 md5;
md5.encodeDataIncrementally(
pad_or_truncate_password_V4(password).c_str(), key_bytes);
md5.encodeDataIncrementally(data.getO().c_str(), key_bytes);
char pbytes[4];
int P = data.getP();
pbytes[0] = static_cast<char>(P & 0xff);
pbytes[1] = static_cast<char>((P >> 8) & 0xff);
pbytes[2] = static_cast<char>((P >> 16) & 0xff);
pbytes[3] = static_cast<char>((P >> 24) & 0xff);
md5.encodeDataIncrementally(pbytes, 4);
md5.encodeDataIncrementally(data.getId1().c_str(),
data.getId1().length());
if ((data.getR() >= 4) && (! data.getEncryptMetadata()))
{
char bytes[4];
memset(bytes, 0xff, 4);
md5.encodeDataIncrementally(bytes, 4);
}
MD5::Digest digest;
int key_len = std::min(static_cast<int>(sizeof(digest)),
data.getLengthBytes());
iterate_md5_digest(md5, digest, ((data.getR() >= 3) ? 50 : 0), key_len);
return std::string(reinterpret_cast<char*>(digest), key_len);
}
static void
compute_O_rc4_key(std::string const& user_password,
std::string const& owner_password,
QPDF::EncryptionData const& data,
unsigned char key[OU_key_bytes_V4])
{
if (data.getV() >= 5)
{
throw std::logic_error(
"compute_O_rc4_key called for file with V >= 5");
}
std::string password = owner_password;
if (password.empty())
{
password = user_password;
}
MD5 md5;
md5.encodeDataIncrementally(
pad_or_truncate_password_V4(password).c_str(), key_bytes);
MD5::Digest digest;
int key_len = std::min(static_cast<int>(sizeof(digest)),
data.getLengthBytes());
iterate_md5_digest(md5, digest, ((data.getR() >= 3) ? 50 : 0), key_len);
memcpy(key, digest, OU_key_bytes_V4);
}
static std::string
compute_O_value(std::string const& user_password,
std::string const& owner_password,
QPDF::EncryptionData const& data)
{
// Algorithm 3.3 from the PDF 1.7 Reference Manual
unsigned char O_key[OU_key_bytes_V4];
compute_O_rc4_key(user_password, owner_password, data, O_key);
char upass[key_bytes];
pad_or_truncate_password_V4(user_password, upass);
std::string k1(reinterpret_cast<char*>(O_key), OU_key_bytes_V4);
pad_short_parameter(k1, data.getLengthBytes());
iterate_rc4(QUtil::unsigned_char_pointer(upass), key_bytes,
O_key, data.getLengthBytes(),
(data.getR() >= 3) ? 20 : 1, false);
return std::string(upass, key_bytes);
}
static
std::string
compute_U_value_R2(std::string const& user_password,
QPDF::EncryptionData const& data)
{
// Algorithm 3.4 from the PDF 1.7 Reference Manual
std::string k1 = QPDF::compute_encryption_key(user_password, data);
char udata[key_bytes];
pad_or_truncate_password_V4("", udata);
pad_short_parameter(k1, data.getLengthBytes());
iterate_rc4(QUtil::unsigned_char_pointer(udata), key_bytes,
QUtil::unsigned_char_pointer(k1),
data.getLengthBytes(), 1, false);
return std::string(udata, key_bytes);
}
static
std::string
compute_U_value_R3(std::string const& user_password,
QPDF::EncryptionData const& data)
{
// Algorithm 3.5 from the PDF 1.7 Reference Manual
std::string k1 = QPDF::compute_encryption_key(user_password, data);
MD5 md5;
md5.encodeDataIncrementally(
pad_or_truncate_password_V4("").c_str(), key_bytes);
md5.encodeDataIncrementally(data.getId1().c_str(),
data.getId1().length());
MD5::Digest digest;
md5.digest(digest);
pad_short_parameter(k1, data.getLengthBytes());
iterate_rc4(digest, sizeof(MD5::Digest),
QUtil::unsigned_char_pointer(k1),
data.getLengthBytes(), 20, false);
char result[key_bytes];
memcpy(result, digest, sizeof(MD5::Digest));
// pad with arbitrary data -- make it consistent for the sake of
// testing
for (unsigned int i = sizeof(MD5::Digest); i < key_bytes; ++i)
{
result[i] = static_cast<char>((i * i) % 0xff);
}
return std::string(result, key_bytes);
}
static std::string
compute_U_value(std::string const& user_password,
QPDF::EncryptionData const& data)
{
if (data.getR() >= 3)
{
return compute_U_value_R3(user_password, data);
}
return compute_U_value_R2(user_password, data);
}
static bool
check_user_password_V4(std::string const& user_password,
QPDF::EncryptionData const& data)
{
// Algorithm 3.6 from the PDF 1.7 Reference Manual
std::string u_value = compute_U_value(user_password, data);
int to_compare = ((data.getR() >= 3) ? sizeof(MD5::Digest)
: key_bytes);
return (memcmp(data.getU().c_str(), u_value.c_str(), to_compare) == 0);
}
static bool
check_user_password_V5(std::string const& user_password,
QPDF::EncryptionData const& data)
{
// Algorithm 3.11 from the PDF 1.7 extension level 3
std::string user_data = data.getU().substr(0, 32);
std::string validation_salt = data.getU().substr(32, 8);
std::string password = truncate_password_V5(user_password);
return (hash_V5(password, validation_salt, "", data) == user_data);
}
static bool
check_user_password(std::string const& user_password,
QPDF::EncryptionData const& data)
{
if (data.getV() < 5)
{
return check_user_password_V4(user_password, data);
}
else
{
return check_user_password_V5(user_password, data);
}
}
static bool
check_owner_password_V4(std::string& user_password,
std::string const& owner_password,
QPDF::EncryptionData const& data)
{
// Algorithm 3.7 from the PDF 1.7 Reference Manual
unsigned char key[OU_key_bytes_V4];
compute_O_rc4_key(user_password, owner_password, data, key);
unsigned char O_data[key_bytes];
memcpy(O_data, QUtil::unsigned_char_pointer(data.getO()), key_bytes);
std::string k1(reinterpret_cast<char*>(key), OU_key_bytes_V4);
pad_short_parameter(k1, data.getLengthBytes());
iterate_rc4(O_data, key_bytes, QUtil::unsigned_char_pointer(k1),
data.getLengthBytes(),
(data.getR() >= 3) ? 20 : 1, true);
std::string new_user_password =
std::string(reinterpret_cast<char*>(O_data), key_bytes);
bool result = false;
if (check_user_password(new_user_password, data))
{
result = true;
user_password = new_user_password;
}
return result;
}
static bool
check_owner_password_V5(std::string const& owner_password,
QPDF::EncryptionData const& data)
{
// Algorithm 3.12 from the PDF 1.7 extension level 3
std::string user_data = data.getU().substr(0, 48);
std::string owner_data = data.getO().substr(0, 32);
std::string validation_salt = data.getO().substr(32, 8);
std::string password = truncate_password_V5(owner_password);
return (hash_V5(password, validation_salt, user_data,
data) == owner_data);
}
static bool
check_owner_password(std::string& user_password,
std::string const& owner_password,
QPDF::EncryptionData const& data)
{
if (data.getV() < 5)
{
return check_owner_password_V4(user_password, owner_password, data);
}
else
{
return check_owner_password_V5(owner_password, data);
}
}
std::string
QPDF::recover_encryption_key_with_password(
std::string const& password, EncryptionData const& data)
{
// Disregard whether Perms is valid.
bool disregard;
return recover_encryption_key_with_password(password, data, disregard);
}
static void
compute_U_UE_value_V5(std::string const& user_password,
std::string const& encryption_key,
QPDF::EncryptionData const& data,
std::string& U, std::string& UE)
{
// Algorithm 3.8 from the PDF 1.7 extension level 3
char k[16];
QUtil::initializeWithRandomBytes(
QUtil::unsigned_char_pointer(k), sizeof(k));
std::string validation_salt(k, 8);
std::string key_salt(k + 8, 8);
U = hash_V5(user_password, validation_salt, "", data) +
validation_salt + key_salt;
std::string intermediate_key = hash_V5(user_password, key_salt, "", data);
UE = process_with_aes(intermediate_key, true, encryption_key);
}
static void
compute_O_OE_value_V5(std::string const& owner_password,
std::string const& encryption_key,
QPDF::EncryptionData const& data,
std::string const& U,
std::string& O, std::string& OE)
{
// Algorithm 3.9 from the PDF 1.7 extension level 3
char k[16];
QUtil::initializeWithRandomBytes(
QUtil::unsigned_char_pointer(k), sizeof(k));
std::string validation_salt(k, 8);
std::string key_salt(k + 8, 8);
O = hash_V5(owner_password, validation_salt, U, data) +
validation_salt + key_salt;
std::string intermediate_key = hash_V5(owner_password, key_salt, U, data);
OE = process_with_aes(intermediate_key, true, encryption_key);
}
void
compute_Perms_value_V5_clear(std::string const& encryption_key,
QPDF::EncryptionData const& data,
unsigned char k[16])
{
// From algorithm 3.10 from the PDF 1.7 extension level 3
unsigned long long extended_perms = 0xffffffff00000000LL | data.getP();
for (int i = 0; i < 8; ++i)
{
k[i] = static_cast<unsigned char>(extended_perms & 0xff);
extended_perms >>= 8;
}
k[8] = data.getEncryptMetadata() ? 'T' : 'F';
k[9] = 'a';
k[10] = 'd';
k[11] = 'b';
QUtil::initializeWithRandomBytes(k + 12, 4);
}
static std::string
compute_Perms_value_V5(std::string const& encryption_key,
QPDF::EncryptionData const& data)
{
// Algorithm 3.10 from the PDF 1.7 extension level 3
unsigned char k[16];
compute_Perms_value_V5_clear(encryption_key, data, k);
return process_with_aes(
encryption_key, true,
std::string(reinterpret_cast<char*>(k), sizeof(k)));
}
std::string
QPDF::recover_encryption_key_with_password(
std::string const& password, EncryptionData const& data,
bool& perms_valid)
{
// Algorithm 3.2a from the PDF 1.7 extension level 3
// This code does not handle Unicode passwords correctly.
// Empirical evidence suggests that most viewers don't. We are
// supposed to process the input string with the SASLprep (RFC
// 4013) profile of stringprep (RFC 3454) and then convert the
// result to UTF-8.
perms_valid = false;
std::string key_password = truncate_password_V5(password);
std::string key_salt;
std::string user_data;
std::string encrypted_file_key;
if (check_owner_password_V5(key_password, data))
{
key_salt = data.getO().substr(40, 8);
user_data = data.getU().substr(0, 48);
encrypted_file_key = data.getOE().substr(0, 32);
}
else if (check_user_password_V5(key_password, data))
{
key_salt = data.getU().substr(40, 8);
encrypted_file_key = data.getUE().substr(0, 32);
}
std::string intermediate_key =
hash_V5(key_password, key_salt, user_data, data);
std::string file_key =
process_with_aes(intermediate_key, false, encrypted_file_key);
// Decrypt Perms and check against expected value
std::string perms_check =
process_with_aes(file_key, false, data.getPerms(), 12);
unsigned char k[16];
compute_Perms_value_V5_clear(file_key, data, k);
perms_valid = (memcmp(perms_check.c_str(), k, 12) == 0);
return file_key;
}
QPDF::encryption_method_e
QPDF::interpretCF(QPDFObjectHandle cf)
{
if (cf.isName())
{
std::string filter = cf.getName();
if (this->m->crypt_filters.count(filter) != 0)
{
return this->m->crypt_filters[filter];
}
else if (filter == "/Identity")
{
return e_none;
}
else
{
return e_unknown;
}
}
else
{
// Default: /Identity
return e_none;
}
}
void
QPDF::initializeEncryption()
{
if (this->m->encryption_initialized)
{
return;
}
this->m->encryption_initialized = true;
// After we initialize encryption parameters, we must used stored
// key information and never look at /Encrypt again. Otherwise,
// things could go wrong if someone mutates the encryption
// dictionary.
if (! this->m->trailer.hasKey("/Encrypt"))
{
return;
}
// Go ahead and set this->m->encrypted here. That way, isEncrypted
// will return true even if there were errors reading the
// encryption dictionary.
this->m->encrypted = true;
std::string id1;
QPDFObjectHandle id_obj = this->m->trailer.getKey("/ID");
if ((id_obj.isArray() &&
(id_obj.getArrayNItems() == 2) &&
id_obj.getArrayItem(0).isString()))
{
id1 = id_obj.getArrayItem(0).getStringValue();
}
else
{
// Treating a missing ID as the empty string enables qpdf to
// decrypt some invalid encrypted files with no /ID that
// poppler can read but Adobe Reader can't.
warn(QPDFExc(qpdf_e_damaged_pdf, this->m->file->getName(),
"trailer", this->m->file->getLastOffset(),
"invalid /ID in trailer dictionary"));
}
QPDFObjectHandle encryption_dict = this->m->trailer.getKey("/Encrypt");
if (! encryption_dict.isDictionary())
{
throw QPDFExc(qpdf_e_damaged_pdf, this->m->file->getName(),
this->m->last_object_description,
this->m->file->getLastOffset(),
"/Encrypt in trailer dictionary is not a dictionary");
}
if (! (encryption_dict.getKey("/Filter").isName() &&
(encryption_dict.getKey("/Filter").getName() == "/Standard")))
{
throw QPDFExc(qpdf_e_damaged_pdf, this->m->file->getName(),
"encryption dictionary", this->m->file->getLastOffset(),
"unsupported encryption filter");
}
if (! encryption_dict.getKey("/SubFilter").isNull())
{
warn(QPDFExc(qpdf_e_unsupported, this->m->file->getName(),
"encryption dictionary", this->m->file->getLastOffset(),
"file uses encryption SubFilters,"
" which qpdf does not support"));
}
if (! (encryption_dict.getKey("/V").isInteger() &&
encryption_dict.getKey("/R").isInteger() &&
encryption_dict.getKey("/O").isString() &&
encryption_dict.getKey("/U").isString() &&
encryption_dict.getKey("/P").isInteger()))
{
throw QPDFExc(qpdf_e_damaged_pdf, this->m->file->getName(),
"encryption dictionary", this->m->file->getLastOffset(),
"some encryption dictionary parameters are missing "
"or the wrong type");
}
int V = encryption_dict.getKey("/V").getIntValue();
int R = encryption_dict.getKey("/R").getIntValue();
std::string O = encryption_dict.getKey("/O").getStringValue();
std::string U = encryption_dict.getKey("/U").getStringValue();
unsigned int P = encryption_dict.getKey("/P").getIntValue();
// If supporting new encryption R/V values, remember to update
// error message inside this if statement.
if (! (((R >= 2) && (R <= 6)) &&
((V == 1) || (V == 2) || (V == 4) || (V == 5))))
{
throw QPDFExc(qpdf_e_unsupported, this->m->file->getName(),
"encryption dictionary", this->m->file->getLastOffset(),
"Unsupported /R or /V in encryption dictionary; R = " +
QUtil::int_to_string(R) + " (max 6), V = " +
QUtil::int_to_string(V) + " (max 5)");
}
this->m->encryption_V = V;
this->m->encryption_R = R;
// OE, UE, and Perms are only present if V >= 5.
std::string OE;
std::string UE;
std::string Perms;
if (V < 5)
{
// These must be exactly the right number of bytes.
pad_short_parameter(O, key_bytes);
pad_short_parameter(U, key_bytes);
if (! ((O.length() == key_bytes) && (U.length() == key_bytes)))
{
throw QPDFExc(qpdf_e_damaged_pdf, this->m->file->getName(),
"encryption dictionary",
this->m->file->getLastOffset(),
"incorrect length for /O and/or /U in "
"encryption dictionary");
}
}
else
{
if (! (encryption_dict.getKey("/OE").isString() &&
encryption_dict.getKey("/UE").isString() &&
encryption_dict.getKey("/Perms").isString()))
{
throw QPDFExc(qpdf_e_damaged_pdf, this->m->file->getName(),
"encryption dictionary",
this->m->file->getLastOffset(),
"some V=5 encryption dictionary parameters are "
"missing or the wrong type");
}
OE = encryption_dict.getKey("/OE").getStringValue();
UE = encryption_dict.getKey("/UE").getStringValue();
Perms = encryption_dict.getKey("/Perms").getStringValue();
// These may be longer than the minimum number of bytes.
pad_short_parameter(O, OU_key_bytes_V5);
pad_short_parameter(U, OU_key_bytes_V5);
pad_short_parameter(OE, OUE_key_bytes_V5);
pad_short_parameter(UE, OUE_key_bytes_V5);
pad_short_parameter(Perms, Perms_key_bytes_V5);
}
int Length = 40;
if (encryption_dict.getKey("/Length").isInteger())
{
Length = encryption_dict.getKey("/Length").getIntValue();
if (R < 3)
{
// Force Length to 40 regardless of what the file says.
Length = 40;
}
if ((Length % 8) || (Length < 40) || (Length > 256))
{
throw QPDFExc(qpdf_e_damaged_pdf, this->m->file->getName(),
"encryption dictionary",
this->m->file->getLastOffset(),
"invalid /Length value in encryption dictionary");
}
}
this->m->encrypt_metadata = true;
if ((V >= 4) && (encryption_dict.getKey("/EncryptMetadata").isBool()))
{
this->m->encrypt_metadata =
encryption_dict.getKey("/EncryptMetadata").getBoolValue();
}
if ((V == 4) || (V == 5))
{
QPDFObjectHandle CF = encryption_dict.getKey("/CF");
std::set<std::string> keys = CF.getKeys();
for (std::set<std::string>::iterator iter = keys.begin();
iter != keys.end(); ++iter)
{
std::string const& filter = *iter;
QPDFObjectHandle cdict = CF.getKey(filter);
if (cdict.isDictionary())
{
encryption_method_e method = e_none;
if (cdict.getKey("/CFM").isName())
{
std::string method_name = cdict.getKey("/CFM").getName();
if (method_name == "/V2")
{
QTC::TC("qpdf", "QPDF_encryption CFM V2");
method = e_rc4;
}
else if (method_name == "/AESV2")
{
QTC::TC("qpdf", "QPDF_encryption CFM AESV2");
method = e_aes;
}
else if (method_name == "/AESV3")
{
QTC::TC("qpdf", "QPDF_encryption CFM AESV3");
method = e_aesv3;
}
else
{
// Don't complain now -- maybe we won't need
// to reference this type.
method = e_unknown;
}
}
this->m->crypt_filters[filter] = method;
}
}
QPDFObjectHandle StmF = encryption_dict.getKey("/StmF");
QPDFObjectHandle StrF = encryption_dict.getKey("/StrF");
QPDFObjectHandle EFF = encryption_dict.getKey("/EFF");
this->m->cf_stream = interpretCF(StmF);
this->m->cf_string = interpretCF(StrF);
if (EFF.isName())
{
this->m->cf_file = interpretCF(EFF);
}
else
{
this->m->cf_file = this->m->cf_stream;
}
}
EncryptionData data(V, R, Length / 8, P, O, U, OE, UE, Perms,
id1, this->m->encrypt_metadata);
if (this->m->provided_password_is_hex_key)
{
// ignore passwords in file
}
else if (check_owner_password(
this->m->user_password, this->m->provided_password, data))
{
// password supplied was owner password; user_password has
// been initialized for V < 5
}
else if (check_user_password(this->m->provided_password, data))
{
this->m->user_password = this->m->provided_password;
}
else
{
throw QPDFExc(qpdf_e_password, this->m->file->getName(),
"", 0, "invalid password");
}
if (this->m->provided_password_is_hex_key)
{
this->m->encryption_key = QUtil::hex_decode(this->m->provided_password);
}
else if (V < 5)
{
// For V < 5, the user password is encrypted with the owner
// password, and the user password is always used for
// computing the encryption key.
this->m->encryption_key = compute_encryption_key(
this->m->user_password, data);
}
else
{
// For V >= 5, either password can be used independently to
// compute the encryption key, and neither password can be
// used to recover the other.
bool perms_valid;
this->m->encryption_key = recover_encryption_key_with_password(
this->m->provided_password, data, perms_valid);
if (! perms_valid)
{
warn(QPDFExc(qpdf_e_damaged_pdf, this->m->file->getName(),
"encryption dictionary",
this->m->file->getLastOffset(),
"/Perms field in encryption dictionary"
" doesn't match expected value"));
}
}
}
std::string
QPDF::getKeyForObject(int objid, int generation, bool use_aes)
{
if (! this->m->encrypted)
{
throw std::logic_error(
"request for encryption key in non-encrypted PDF");
}
if (! ((objid == this->m->cached_key_objid) &&
(generation == this->m->cached_key_generation)))
{
this->m->cached_object_encryption_key =
compute_data_key(this->m->encryption_key, objid, generation,
use_aes, this->m->encryption_V,
this->m->encryption_R);
this->m->cached_key_objid = objid;
this->m->cached_key_generation = generation;
}
return this->m->cached_object_encryption_key;
}
void
QPDF::decryptString(std::string& str, int objid, int generation)
{
if (objid == 0)
{
return;
}
bool use_aes = false;
if (this->m->encryption_V >= 4)
{
switch (this->m->cf_string)
{
case e_none:
return;
case e_aes:
use_aes = true;
break;
case e_aesv3:
use_aes = true;
break;
case e_rc4:
break;
default:
warn(QPDFExc(qpdf_e_damaged_pdf, this->m->file->getName(),
this->m->last_object_description,
this->m->file->getLastOffset(),
"unknown encryption filter for strings"
" (check /StrF in /Encrypt dictionary);"
" strings may be decrypted improperly"));
// To avoid repeated warnings, reset cf_string. Assume
// we'd want to use AES if V == 4.
this->m->cf_string = e_aes;
use_aes = true;
break;
}
}
std::string key = getKeyForObject(objid, generation, use_aes);
try
{
if (use_aes)
{
QTC::TC("qpdf", "QPDF_encryption aes decode string");
Pl_Buffer bufpl("decrypted string");
Pl_AES_PDF pl("aes decrypt string", &bufpl, false,
QUtil::unsigned_char_pointer(key),
key.length());
pl.write(QUtil::unsigned_char_pointer(str), str.length());
pl.finish();
PointerHolder<Buffer> buf = bufpl.getBuffer();
str = std::string(reinterpret_cast<char*>(buf->getBuffer()),
buf->getSize());
}
else
{
QTC::TC("qpdf", "QPDF_encryption rc4 decode string");
unsigned int vlen = str.length();
// Using PointerHolder guarantees that tmp will
// be freed even if rc4.process throws an exception.
PointerHolder<char> tmp(true, QUtil::copy_string(str));
RC4 rc4(QUtil::unsigned_char_pointer(key), key.length());
rc4.process(QUtil::unsigned_char_pointer(tmp.getPointer()), vlen);
str = std::string(tmp.getPointer(), vlen);
}
}
catch (QPDFExc&)
{
throw;
}
catch (std::runtime_error& e)
{
throw QPDFExc(qpdf_e_damaged_pdf, this->m->file->getName(),
this->m->last_object_description,
this->m->file->getLastOffset(),
"error decrypting string for object " +
QUtil::int_to_string(objid) + " " +
QUtil::int_to_string(generation) + ": " + e.what());
}
}
void
QPDF::decryptStream(Pipeline*& pipeline, int objid, int generation,
QPDFObjectHandle& stream_dict,
std::vector<PointerHolder<Pipeline> >& heap)
{
std::string type;
if (stream_dict.getKey("/Type").isName())
{
type = stream_dict.getKey("/Type").getName();
}
if (type == "/XRef")
{
QTC::TC("qpdf", "QPDF_encryption xref stream from encrypted file");
return;
}
bool use_aes = false;
if (this->m->encryption_V >= 4)
{
encryption_method_e method = e_unknown;
std::string method_source = "/StmF from /Encrypt dictionary";
if (stream_dict.getKey("/Filter").isOrHasName("/Crypt"))
{
if (stream_dict.getKey("/DecodeParms").isDictionary())
{
QPDFObjectHandle decode_parms =
stream_dict.getKey("/DecodeParms");
if (decode_parms.getKey("/Type").isName() &&
(decode_parms.getKey("/Type").getName() ==
"/CryptFilterDecodeParms"))
{
QTC::TC("qpdf", "QPDF_encryption stream crypt filter");
method = interpretCF(decode_parms.getKey("/Name"));
method_source = "stream's Crypt decode parameters";
}
}
else if (stream_dict.getKey("/DecodeParms").isArray() &&
stream_dict.getKey("/Filter").isArray())
{
QPDFObjectHandle filter = stream_dict.getKey("/Filter");
QPDFObjectHandle decode = stream_dict.getKey("/DecodeParms");
if (filter.getArrayNItems() == decode.getArrayNItems())
{
for (int i = 0; i < filter.getArrayNItems(); ++i)
{
if (filter.getArrayItem(i).isName() &&
(filter.getArrayItem(i).getName() == "/Crypt"))
{
QPDFObjectHandle crypt_params =
decode.getArrayItem(i);
if (crypt_params.isDictionary() &&
crypt_params.getKey("/Name").isName())
{
QTC::TC("qpdf", "QPDF_encrypt crypt array");
method = interpretCF(
crypt_params.getKey("/Name"));
method_source = "stream's Crypt "
"decode parameters (array)";
}
}
}
}
}
}
if (method == e_unknown)
{
if ((! this->m->encrypt_metadata) && (type == "/Metadata"))
{
QTC::TC("qpdf", "QPDF_encryption cleartext metadata");
method = e_none;
}
else
{
if (this->m->attachment_streams.count(
QPDFObjGen(objid, generation)) > 0)
{
method = this->m->cf_file;
}
else
{
method = this->m->cf_stream;
}
}
}
use_aes = false;
switch (method)
{
case e_none:
return;
break;
case e_aes:
use_aes = true;
break;
case e_aesv3:
use_aes = true;
break;
case e_rc4:
break;
default:
// filter local to this stream.
warn(QPDFExc(qpdf_e_damaged_pdf, this->m->file->getName(),
this->m->last_object_description,
this->m->file->getLastOffset(),
"unknown encryption filter for streams"
" (check " + method_source + ");"
" streams may be decrypted improperly"));
// To avoid repeated warnings, reset cf_stream. Assume
// we'd want to use AES if V == 4.
this->m->cf_stream = e_aes;
break;
}
}
std::string key = getKeyForObject(objid, generation, use_aes);
if (use_aes)
{
QTC::TC("qpdf", "QPDF_encryption aes decode stream");
pipeline = new Pl_AES_PDF("AES stream decryption", pipeline,
false, QUtil::unsigned_char_pointer(key),
key.length());
}
else
{
QTC::TC("qpdf", "QPDF_encryption rc4 decode stream");
pipeline = new Pl_RC4("RC4 stream decryption", pipeline,
QUtil::unsigned_char_pointer(key),
key.length());
}
heap.push_back(pipeline);
}
void
QPDF::compute_encryption_O_U(
char const* user_password, char const* owner_password,
int V, int R, int key_len, int P, bool encrypt_metadata,
std::string const& id1, std::string& O, std::string& U)
{
if (V >= 5)
{
throw std::logic_error(
"compute_encryption_O_U called for file with V >= 5");
}
EncryptionData data(V, R, key_len, P, "", "", "", "", "",
id1, encrypt_metadata);
data.setO(compute_O_value(user_password, owner_password, data));
O = data.getO();
data.setU(compute_U_value(user_password, data));
U = data.getU();
}
void
QPDF::compute_encryption_parameters_V5(
char const* user_password, char const* owner_password,
int V, int R, int key_len, int P, bool encrypt_metadata,
std::string const& id1,
std::string& encryption_key,
std::string& O, std::string& U,
std::string& OE, std::string& UE, std::string& Perms)
{
EncryptionData data(V, R, key_len, P, "", "", "", "", "",
id1, encrypt_metadata);
unsigned char k[key_bytes];
QUtil::initializeWithRandomBytes(k, key_bytes);
encryption_key = std::string(reinterpret_cast<char*>(k), key_bytes);
compute_U_UE_value_V5(user_password, encryption_key, data, U, UE);
compute_O_OE_value_V5(owner_password, encryption_key, data, U, O, OE);
Perms = compute_Perms_value_V5(encryption_key, data);
data.setV5EncryptionParameters(O, OE, U, UE, Perms);
}
std::string const&
QPDF::getPaddedUserPassword() const
{
return this->m->user_password;
}
std::string
QPDF::getTrimmedUserPassword() const
{
std::string result = this->m->user_password;
trim_user_password(result);
return result;
}
std::string
QPDF::getEncryptionKey() const
{
return this->m->encryption_key;
}
bool
QPDF::isEncrypted() const
{
return this->m->encrypted;
}
bool
QPDF::isEncrypted(int& R, int& P)
{
int V;
encryption_method_e stream, string, file;
return isEncrypted(R, P, V, stream, string, file);
}
bool
QPDF::isEncrypted(int& R, int& P, int& V,
encryption_method_e& stream_method,
encryption_method_e& string_method,
encryption_method_e& file_method)
{
if (this->m->encrypted)
{
QPDFObjectHandle trailer = getTrailer();
QPDFObjectHandle encrypt = trailer.getKey("/Encrypt");
QPDFObjectHandle Pkey = encrypt.getKey("/P");
QPDFObjectHandle Rkey = encrypt.getKey("/R");
QPDFObjectHandle Vkey = encrypt.getKey("/V");
P = Pkey.getIntValue();
R = Rkey.getIntValue();
V = Vkey.getIntValue();
stream_method = this->m->cf_stream;
string_method = this->m->cf_string;
file_method = this->m->cf_file;
return true;
}
else
{
return false;
}
}
static bool
is_bit_set(int P, int bit)
{
// Bits in P are numbered from 1 in the spec
return (P & (1 << (bit - 1)));
}
bool
QPDF::allowAccessibility()
{
int R = 0;
int P = 0;
bool status = true;
if (isEncrypted(R, P))
{
if (R < 3)
{
status = is_bit_set(P, 5);
}
else
{
status = is_bit_set(P, 10);
}
}
return status;
}
bool
QPDF::allowExtractAll()
{
int R = 0;
int P = 0;
bool status = true;
if (isEncrypted(R, P))
{
status = is_bit_set(P, 5);
}
return status;
}
bool
QPDF::allowPrintLowRes()
{
int R = 0;
int P = 0;
bool status = true;
if (isEncrypted(R, P))
{
status = is_bit_set(P, 3);
}
return status;
}
bool
QPDF::allowPrintHighRes()
{
int R = 0;
int P = 0;
bool status = true;
if (isEncrypted(R, P))
{
status = is_bit_set(P, 3);
if ((R >= 3) && (! is_bit_set(P, 12)))
{
status = false;
}
}
return status;
}
bool
QPDF::allowModifyAssembly()
{
int R = 0;
int P = 0;
bool status = true;
if (isEncrypted(R, P))
{
if (R < 3)
{
status = is_bit_set(P, 4);
}
else
{
status = is_bit_set(P, 11);
}
}
return status;
}
bool
QPDF::allowModifyForm()
{
int R = 0;
int P = 0;
bool status = true;
if (isEncrypted(R, P))
{
if (R < 3)
{
status = is_bit_set(P, 6);
}
else
{
status = is_bit_set(P, 9);
}
}
return status;
}
bool
QPDF::allowModifyAnnotation()
{
int R = 0;
int P = 0;
bool status = true;
if (isEncrypted(R, P))
{
status = is_bit_set(P, 6);
}
return status;
}
bool
QPDF::allowModifyOther()
{
int R = 0;
int P = 0;
bool status = true;
if (isEncrypted(R, P))
{
status = is_bit_set(P, 4);
}
return status;
}
bool
QPDF::allowModifyAll()
{
int R = 0;
int P = 0;
bool status = true;
if (isEncrypted(R, P))
{
status = (is_bit_set(P, 4) && is_bit_set(P, 6));
if (R >= 3)
{
status = status && (is_bit_set(P, 9) && is_bit_set(P, 11));
}
}
return status;
}
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