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648 lines
16 KiB
C++
648 lines
16 KiB
C++
// This file implements methods from the QPDF class that involve
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// encryption.
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#include <qpdf/QPDF.hh>
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#include <qpdf/QPDFExc.hh>
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#include <qpdf/QUtil.hh>
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#include <qpdf/Pl_RC4.hh>
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#include <qpdf/RC4.hh>
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#include <qpdf/MD5.hh>
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#include <string.h>
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static char const padding_string[] = {
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0x28, 0xbf, 0x4e, 0x5e, 0x4e, 0x75, 0x8a, 0x41,
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0x64, 0x00, 0x4e, 0x56, 0xff, 0xfa, 0x01, 0x08,
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0x2e, 0x2e, 0x00, 0xb6, 0xd0, 0x68, 0x3e, 0x80,
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0x2f, 0x0c, 0xa9, 0xfe, 0x64, 0x53, 0x69, 0x7a
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};
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static unsigned int const O_key_bytes = sizeof(MD5::Digest);
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static unsigned int const id_bytes = 16;
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static unsigned int const key_bytes = 32;
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void
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pad_or_truncate_password(std::string const& password, char k1[key_bytes])
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{
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int password_bytes = std::min((size_t) key_bytes, password.length());
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int pad_bytes = key_bytes - password_bytes;
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memcpy(k1, password.c_str(), password_bytes);
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memcpy(k1 + password_bytes, padding_string, pad_bytes);
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}
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DLL_EXPORT
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void
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QPDF::trim_user_password(std::string& user_password)
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{
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// Although unnecessary, this routine trims the padding string
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// from the end of a user password. Its only purpose is for
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// recovery of user passwords which is done in the test suite.
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char const* cstr = user_password.c_str();
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size_t len = user_password.length();
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if (len < key_bytes)
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{
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return;
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}
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char const* p = 0;
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while ((p = strchr(cstr, '\x28')) != 0)
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{
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if (memcmp(p, padding_string, len - (p - cstr)) == 0)
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{
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user_password = user_password.substr(0, p - cstr);
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return;
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}
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}
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}
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static std::string
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pad_or_truncate_password(std::string const& password)
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{
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char k1[key_bytes];
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pad_or_truncate_password(password, k1);
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return std::string(k1, key_bytes);
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}
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static void
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iterate_md5_digest(MD5& md5, MD5::Digest& digest, int iterations)
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{
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md5.digest(digest);
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for (int i = 0; i < iterations; ++i)
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{
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MD5 m;
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m.encodeDataIncrementally((char*)digest, sizeof(digest));
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m.digest(digest);
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}
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}
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static void
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iterate_rc4(unsigned char* data, int data_len,
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unsigned char* okey, int key_len,
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int iterations, bool reverse)
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{
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unsigned char* key = new unsigned char[key_len];
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for (int i = 0; i < iterations; ++i)
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{
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int const xor_value = (reverse ? iterations - 1 - i : i);
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for (int j = 0; j < key_len; ++j)
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{
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key[j] = okey[j] ^ xor_value;
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}
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RC4 rc4(key, key_len);
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rc4.process(data, data_len);
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}
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delete [] key;
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}
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DLL_EXPORT
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std::string
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QPDF::compute_data_key(std::string const& encryption_key,
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int objid, int generation)
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{
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// Algorithm 3.1 from the PDF 1.4 Reference Manual
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std::string result = encryption_key;
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// Append low three bytes of object ID and low two bytes of generation
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result += (char) (objid & 0xff);
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result += (char) ((objid >> 8) & 0xff);
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result += (char) ((objid >> 16) & 0xff);
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result += (char) (generation & 0xff);
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result += (char) ((generation >> 8) & 0xff);
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MD5 md5;
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md5.encodeDataIncrementally(result.c_str(), result.length());
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MD5::Digest digest;
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md5.digest(digest);
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return std::string((char*) digest,
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std::min(result.length(), (size_t) 16));
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}
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DLL_EXPORT
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std::string
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QPDF::compute_encryption_key(
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std::string const& password, EncryptionData const& data)
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{
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// Algorithm 3.2 from the PDF 1.4 Reference Manual
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MD5 md5;
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md5.encodeDataIncrementally(
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pad_or_truncate_password(password).c_str(), key_bytes);
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md5.encodeDataIncrementally(data.O.c_str(), key_bytes);
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char pbytes[4];
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pbytes[0] = (char) (data.P & 0xff);
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pbytes[1] = (char) ((data.P >> 8) & 0xff);
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pbytes[2] = (char) ((data.P >> 16) & 0xff);
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pbytes[3] = (char) ((data.P >> 24) & 0xff);
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md5.encodeDataIncrementally(pbytes, 4);
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md5.encodeDataIncrementally(data.id1.c_str(), id_bytes);
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MD5::Digest digest;
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iterate_md5_digest(md5, digest, ((data.R == 3) ? 50 : 0));
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return std::string((char*)digest, data.Length_bytes);
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}
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static void
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compute_O_rc4_key(std::string const& user_password,
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std::string const& owner_password,
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QPDF::EncryptionData const& data,
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unsigned char key[O_key_bytes])
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{
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std::string password = owner_password;
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if (password.empty())
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{
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password = user_password;
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}
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MD5 md5;
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md5.encodeDataIncrementally(
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pad_or_truncate_password(password).c_str(), key_bytes);
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MD5::Digest digest;
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iterate_md5_digest(md5, digest, ((data.R == 3) ? 50 : 0));
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memcpy(key, digest, O_key_bytes);
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}
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static std::string
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compute_O_value(std::string const& user_password,
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std::string const& owner_password,
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QPDF::EncryptionData const& data)
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{
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// Algorithm 3.3 from the PDF 1.4 Reference Manual
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unsigned char O_key[O_key_bytes];
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compute_O_rc4_key(user_password, owner_password, data, O_key);
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char upass[key_bytes];
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pad_or_truncate_password(user_password, upass);
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iterate_rc4((unsigned char*) upass, key_bytes,
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O_key, data.Length_bytes, (data.R == 3) ? 20 : 1, false);
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return std::string(upass, key_bytes);
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}
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static
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std::string
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compute_U_value_R2(std::string const& user_password,
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QPDF::EncryptionData const& data)
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{
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// Algorithm 3.4 from the PDF 1.4 Reference Manual
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std::string k1 = QPDF::compute_encryption_key(user_password, data);
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char udata[key_bytes];
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pad_or_truncate_password("", udata);
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iterate_rc4((unsigned char*) udata, key_bytes,
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(unsigned char*)k1.c_str(), data.Length_bytes, 1, false);
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return std::string(udata, key_bytes);
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}
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static
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std::string
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compute_U_value_R3(std::string const& user_password,
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QPDF::EncryptionData const& data)
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{
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// Algorithm 3.5 from the PDF 1.4 Reference Manual
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std::string k1 = QPDF::compute_encryption_key(user_password, data);
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MD5 md5;
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md5.encodeDataIncrementally(
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pad_or_truncate_password("").c_str(), key_bytes);
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md5.encodeDataIncrementally(data.id1.c_str(), data.id1.length());
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MD5::Digest digest;
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md5.digest(digest);
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iterate_rc4(digest, sizeof(MD5::Digest),
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(unsigned char*) k1.c_str(), data.Length_bytes, 20, false);
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char result[key_bytes];
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memcpy(result, digest, sizeof(MD5::Digest));
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// pad with arbitrary data -- make it consistent for the sake of
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// testing
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for (unsigned int i = sizeof(MD5::Digest); i < key_bytes; ++i)
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{
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result[i] = (char)((i * i) % 0xff);
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}
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return std::string(result, key_bytes);
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}
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static std::string
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compute_U_value(std::string const& user_password,
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QPDF::EncryptionData const& data)
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{
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if (data.R == 3)
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{
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return compute_U_value_R3(user_password, data);
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}
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return compute_U_value_R2(user_password, data);
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}
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static bool
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check_user_password(std::string const& user_password,
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QPDF::EncryptionData const& data)
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{
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// Algorithm 3.6 from the PDF 1.4 Reference Manual
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std::string u_value = compute_U_value(user_password, data);
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int to_compare = ((data.R == 3) ? sizeof(MD5::Digest) : key_bytes);
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return (memcmp(data.U.c_str(), u_value.c_str(), to_compare) == 0);
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}
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static bool
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check_owner_password(std::string& user_password,
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std::string const& owner_password,
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QPDF::EncryptionData const& data)
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{
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// Algorithm 3.7 from the PDF 1.4 Reference Manual
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unsigned char key[O_key_bytes];
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compute_O_rc4_key(user_password, owner_password, data, key);
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unsigned char O_data[key_bytes];
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memcpy(O_data, (unsigned char*) data.O.c_str(), key_bytes);
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iterate_rc4(O_data, key_bytes, key, data.Length_bytes,
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(data.R == 3) ? 20 : 1, true);
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std::string new_user_password =
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std::string((char*)O_data, key_bytes);
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bool result = false;
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if (check_user_password(new_user_password, data))
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{
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result = true;
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user_password = new_user_password;
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}
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return result;
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}
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void
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QPDF::initializeEncryption()
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{
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if (this->encryption_initialized)
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{
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return;
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}
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this->encryption_initialized = true;
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// After we initialize encryption parameters, we must used stored
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// key information and never look at /Encrypt again. Otherwise,
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// things could go wrong if someone mutates the encryption
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// dictionary.
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if (! this->trailer.hasKey("/Encrypt"))
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{
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return;
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}
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QPDFObjectHandle id_obj = this->trailer.getKey("/ID");
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if (! (id_obj.isArray() &&
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(id_obj.getArrayNItems() == 2) &&
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id_obj.getArrayItem(0).isString()))
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{
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throw QPDFExc(this->file.getName(), this->file.getLastOffset(),
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"invalid /ID in trailer dictionary");
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}
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std::string id1 = id_obj.getArrayItem(0).getStringValue();
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if (id1.length() != id_bytes)
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{
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throw QPDFExc(this->file.getName(), this->file.getLastOffset(),
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"first /ID string in trailer dictionary has "
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"incorrect length");
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}
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QPDFObjectHandle encryption_dict = this->trailer.getKey("/Encrypt");
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if (! encryption_dict.isDictionary())
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{
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throw QPDFExc(this->file.getName(), this->file.getLastOffset(),
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"/Encrypt in trailer dictionary is not a dictionary");
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}
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if (! (encryption_dict.getKey("/Filter").isName() &&
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(encryption_dict.getKey("/Filter").getName() == "/Standard")))
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{
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throw QPDFExc(this->file.getName(), this->file.getLastOffset(),
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"unsupported encryption filter");
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}
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if (! (encryption_dict.getKey("/V").isInteger() &&
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encryption_dict.getKey("/R").isInteger() &&
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encryption_dict.getKey("/O").isString() &&
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encryption_dict.getKey("/U").isString() &&
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encryption_dict.getKey("/P").isInteger()))
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{
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throw QPDFExc(this->file.getName(), this->file.getLastOffset(),
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"some encryption dictionary parameters are missing "
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"or the wrong type");
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}
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int V = encryption_dict.getKey("/V").getIntValue();
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int R = encryption_dict.getKey("/R").getIntValue();
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std::string O = encryption_dict.getKey("/O").getStringValue();
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std::string U = encryption_dict.getKey("/U").getStringValue();
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unsigned int P = (unsigned int) encryption_dict.getKey("/P").getIntValue();
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if (! (((R == 2) || (R == 3)) &&
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((V == 1) || (V == 2))))
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{
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throw QPDFExc(this->file.getName(), this->file.getLastOffset(),
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"Unsupported /R or /V in encryption dictionary");
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}
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if (! ((O.length() == key_bytes) && (U.length() == key_bytes)))
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{
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throw QPDFExc(this->file.getName(), this->file.getLastOffset(),
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"incorrect length for /O and/or /P in "
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"encryption dictionary");
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}
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int Length = 40;
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if (encryption_dict.getKey("/Length").isInteger())
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{
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Length = encryption_dict.getKey("/Length").getIntValue();
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if ((Length % 8) || (Length < 40) || (Length > 128))
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{
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throw QPDFExc(this->file.getName(), this->file.getLastOffset(),
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"invalid /Length value in encryption dictionary");
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}
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}
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EncryptionData data(V, R, Length / 8, P, O, U, id1);
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if (check_owner_password(this->user_password, this->provided_password, data))
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{
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// password supplied was owner password; user_password has
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// been initialized
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}
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else if (check_user_password(this->provided_password, data))
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{
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this->user_password = this->provided_password;
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}
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else
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{
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throw QPDFExc(this->file.getName() + ": invalid password");
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}
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this->encrypted = true;
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this->encryption_key = compute_encryption_key(this->user_password, data);
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}
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std::string
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QPDF::getKeyForObject(int objid, int generation)
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{
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if (! this->encrypted)
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{
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throw std::logic_error(
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"request for encryption key in non-encrypted PDF");
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}
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if (! ((objid == this->cached_key_objid) &&
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(generation == this->cached_key_generation)))
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{
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this->cached_object_encryption_key =
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compute_data_key(this->encryption_key, objid, generation);
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this->cached_key_objid = objid;
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this->cached_key_generation = generation;
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}
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return this->cached_object_encryption_key;
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}
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void
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QPDF::decryptString(std::string& str, int objid, int generation)
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{
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if (objid == 0)
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{
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return;
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}
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std::string key = getKeyForObject(objid, generation);
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char* tmp = QUtil::copy_string(str);
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unsigned int vlen = str.length();
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RC4 rc4((unsigned char const*)key.c_str(), key.length());
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rc4.process((unsigned char*)tmp, vlen);
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str = std::string(tmp, vlen);
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delete [] tmp;
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}
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void
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QPDF::decryptStream(Pipeline*& pipeline, int objid, int generation,
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std::vector<PointerHolder<Pipeline> >& heap)
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{
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std::string key = getKeyForObject(objid, generation);
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pipeline = new Pl_RC4("stream decryption", pipeline,
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(unsigned char*) key.c_str(), key.length());
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heap.push_back(pipeline);
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}
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DLL_EXPORT
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void
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QPDF::compute_encryption_O_U(
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char const* user_password, char const* owner_password,
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int V, int R, int key_len, int P,
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std::string const& id1, std::string& O, std::string& U)
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{
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EncryptionData data(V, R, key_len, P, "", "", id1);
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data.O = compute_O_value(user_password, owner_password, data);
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O = data.O;
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U = compute_U_value(user_password, data);
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}
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DLL_EXPORT
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std::string const&
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QPDF::getPaddedUserPassword() const
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{
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return this->user_password;
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}
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DLL_EXPORT
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std::string
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QPDF::getTrimmedUserPassword() const
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{
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std::string result = this->user_password;
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trim_user_password(result);
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return result;
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}
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DLL_EXPORT
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bool
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QPDF::isEncrypted() const
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{
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return this->encrypted;
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}
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DLL_EXPORT
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bool
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QPDF::isEncrypted(int& R, int& P)
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{
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if (this->encrypted)
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{
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QPDFObjectHandle trailer = getTrailer();
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QPDFObjectHandle encrypt = trailer.getKey("/Encrypt");
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QPDFObjectHandle Pkey = encrypt.getKey("/P");
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QPDFObjectHandle Rkey = encrypt.getKey("/R");
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P = Pkey.getIntValue();
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R = Rkey.getIntValue();
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return true;
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}
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else
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{
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return false;
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}
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}
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static bool
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is_bit_set(int P, int bit)
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{
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// Bits in P are numbered from 1 in the spec
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return (P & (1 << (bit - 1)));
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}
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DLL_EXPORT
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bool
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QPDF::allowAccessibility()
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{
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int R = 0;
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int P = 0;
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bool status = true;
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if (isEncrypted(R, P))
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{
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if (R < 3)
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{
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status = is_bit_set(P, 5);
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}
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else
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{
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status = is_bit_set(P, 10);
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}
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}
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return status;
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}
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DLL_EXPORT
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bool
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QPDF::allowExtractAll()
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{
|
|
int R = 0;
|
|
int P = 0;
|
|
bool status = true;
|
|
if (isEncrypted(R, P))
|
|
{
|
|
status = is_bit_set(P, 5);
|
|
}
|
|
return status;
|
|
}
|
|
|
|
DLL_EXPORT
|
|
bool
|
|
QPDF::allowPrintLowRes()
|
|
{
|
|
int R = 0;
|
|
int P = 0;
|
|
bool status = true;
|
|
if (isEncrypted(R, P))
|
|
{
|
|
status = is_bit_set(P, 3);
|
|
}
|
|
return status;
|
|
}
|
|
|
|
DLL_EXPORT
|
|
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;
|
|
}
|
|
|
|
DLL_EXPORT
|
|
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;
|
|
}
|
|
|
|
DLL_EXPORT
|
|
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;
|
|
}
|
|
|
|
DLL_EXPORT
|
|
bool
|
|
QPDF::allowModifyAnnotation()
|
|
{
|
|
int R = 0;
|
|
int P = 0;
|
|
bool status = true;
|
|
if (isEncrypted(R, P))
|
|
{
|
|
status = is_bit_set(P, 6);
|
|
}
|
|
return status;
|
|
}
|
|
|
|
DLL_EXPORT
|
|
bool
|
|
QPDF::allowModifyOther()
|
|
{
|
|
int R = 0;
|
|
int P = 0;
|
|
bool status = true;
|
|
if (isEncrypted(R, P))
|
|
{
|
|
status = is_bit_set(P, 4);
|
|
}
|
|
return status;
|
|
}
|
|
|
|
DLL_EXPORT
|
|
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;
|
|
}
|