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Code Issues Releases Wiki Activity

Try passwords with different string encodings

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This commit is contained in:
Jay Berkenbilt 2019-01-17 19:44:18 -05:00
parent e4fa5a3c2a
commit 392f2ece51
2 changed files with 85 additions and 1 deletions
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7
ChangeLog
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@ -1,5 +1,12 @@
2019-01-17 Jay Berkenbilt <ejb@ql.org>
* When attempting to open an encrypted file with a password, if
the password doesn't work, try alternative passwords created by
re-interpreting the supplied password with different string
encodings. This makes qpdf able to recover passwords with
non-ASCII characters when either the decryption or encryption
operation was performed with an incorrectly encoded password.
* Fix data loss bug: qpdf was discarding referenced resources in
the case in which a page's resource dictionary contained an
indirect reference for either /Font or /XObject that contained

79
qpdf/qpdf.cc
View File

@ -3671,7 +3671,7 @@ ImageOptimizer::provideStreamData(int, int, Pipeline* pipeline)
}
template <typename T>
static PointerHolder<QPDF> do_process(
static PointerHolder<QPDF> do_process_once(
void (QPDF::*fn)(T, char const*),
T item, char const* password,
Options& o, bool empty)
@ -3689,6 +3689,83 @@ static PointerHolder<QPDF> do_process(
return pdf;
}
template <typename T>
static PointerHolder<QPDF> do_process(
void (QPDF::*fn)(T, char const*),
T item, char const* password,
Options& o, bool empty)
{
// If a password has been specified but doesn't work, try other
// passwords that are equivalent in different character encodings.
// This makes it possible to open PDF files that were encrypted
// using incorrect string encodings. For example, if someone used
// a password encoded in PDF Doc encoding or Windows code page
// 1252 for an AES-encrypted file or a UTF-8-encoded password on
// an RC4-encrypted file, or if the password was properly encoded
// by the password given here was incorrectly encoded, there's a
// good chance we'd succeed here.
if ((password == 0) || empty || o.password_is_hex_key)
{
// There is no password, so just do the normal processing.
return do_process_once(fn, item, password, o, empty);
}
// Get a list of otherwise encoded strings. Keep in scope for this
// method.
std::vector<std::string> passwords_str =
QUtil::possible_repaired_encodings(password);
// Represent to char const*, as required by the QPDF class.
std::vector<char const*> passwords;
for (std::vector<std::string>::iterator iter = passwords_str.begin();
iter != passwords_str.end(); ++iter)
{
passwords.push_back((*iter).c_str());
}
// We always try the supplied password first because it is the
// first string returned by possible_repaired_encodings. If there
// is more than one option, go ahead and put the supplied password
// at the end so that it's that decoding attempt whose exception
// is thrown.
if (passwords.size() > 1)
{
passwords.push_back(password);
}
// Try each password. If one works, return the resulting object.
// If they all fail, throw the exception thrown by the final
// attempt, which, like the first attempt, will be with the
// supplied password.
bool warned = false;
for (std::vector<char const*>::iterator iter = passwords.begin();
iter != passwords.end(); ++iter)
{
try
{
return do_process_once(fn, item, *iter, o, empty);
}
catch (QPDFExc& e)
{
std::vector<char const*>::iterator next = iter;
++next;
if (next == passwords.end())
{
throw e;
}
}
if ((! warned) && o.verbose)
{
warned = true;
std::cout << whoami << ": supplied password didn't work;"
<< " trying other passwords based on interpreting"
<< " password with different string encodings"
<< std::endl;
}
}
// Should not be reachable
throw std::logic_error("do_process returned");
}
static PointerHolder<QPDF> process_file(char const* filename,
char const* password,
Options& o)