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Need object when reading/writing encrypted PDFs (to decrypt/encrypt strings),

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RC4 writing is now working, AES-128 needs work, AES-256 hasn't been done yet.
This commit is contained in:
Michael R Sweet
2021-10-23 18:08:16 -04:00
parent 3af39d5d1f
commit dd56317635
8 changed files with 175 additions and 62 deletions
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82
pdfio-file.c
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@ -193,6 +193,7 @@ pdfioFileCreate(
pdfio_file_t *pdf; // PDF file
pdfio_dict_t *dict; // Dictionary for pages object
pdfio_dict_t *info_dict; // Dictionary for information object
unsigned char id_value[16]; // File ID value
// Range check input...
@ -303,6 +304,15 @@ pdfioFileCreate(
return (NULL);
}
// Create random file ID values...
_pdfioCryptoMakeRandom(id_value, sizeof(id_value));
if ((pdf->id_array = pdfioArrayCreate(pdf)) != NULL)
{
pdfioArrayAppendBinary(pdf->id_array, id_value, sizeof(id_value));
pdfioArrayAppendBinary(pdf->id_array, id_value, sizeof(id_value));
}
return (pdf);
}
@ -458,6 +468,7 @@ pdfioFileCreateOutput(
pdfio_file_t *pdf; // PDF file
pdfio_dict_t *dict; // Dictionary for pages object
pdfio_dict_t *info_dict; // Dictionary for information object
unsigned char id_value[16]; // File ID value
// Range check input...
@ -558,6 +569,15 @@ pdfioFileCreateOutput(
return (NULL);
}
// Create random file ID values...
_pdfioCryptoMakeRandom(id_value, sizeof(id_value));
if ((pdf->id_array = pdfioArrayCreate(pdf)) != NULL)
{
pdfioArrayAppendBinary(pdf->id_array, id_value, sizeof(id_value));
pdfioArrayAppendBinary(pdf->id_array, id_value, sizeof(id_value));
}
return (pdf);
}
@ -1099,51 +1119,51 @@ pdfioFileSetPermissions(
case PDFIO_ENCRYPTION_RC4_128 :
case PDFIO_ENCRYPTION_AES_128 :
// Create the 128-bit encryption keys...
if (user_password && *user_password)
if (user_password)
{
// Copy the user password and pad it with the special PDF pad bytes
// Use the specified user password
if ((len = strlen(user_password)) > sizeof(user_pad))
len = sizeof(user_pad);
if (len > 0)
memcpy(user_pad, user_password, len);
if (len < sizeof(user_pad))
memcpy(user_pad + len, pad, sizeof(user_pad) - len);
}
else
{
// Use default (pad) password
memcpy(user_pad, pad, sizeof(user_pad));
// No user password
len = 0;
}
if (owner_password && *owner_password)
if (len > 0)
memcpy(user_pad, user_password, len);
if (len < sizeof(user_pad))
memcpy(user_pad + len, pad, sizeof(user_pad) - len);
if (owner_password)
{
// Copy the owner password and pad it with the special PDF pad bytes
// Use the specified owner password...
if ((len = strlen(owner_password)) > sizeof(owner_pad))
len = sizeof(owner_pad);
if (len > 0)
memcpy(owner_pad, owner_password, len);
if (len < sizeof(owner_pad))
memcpy(owner_pad + len, pad, sizeof(owner_pad) - len);
}
else if (user_password && *user_password)
{
// Generate a random owner password...
_pdfioCryptoMakeRandom(owner_pad, sizeof(owner_pad));
len = sizeof(owner_pad);
}
else
{
// Use default (pad) password
memcpy(owner_pad, pad, sizeof(owner_pad));
// No owner password
len = 0;
}
if (len > 0)
memcpy(owner_pad, owner_password, len);
if (len < sizeof(owner_pad))
memcpy(owner_pad + len, pad, sizeof(owner_pad) - len);
// Compute the owner key...
_pdfioCryptoMD5Init(&md5);
_pdfioCryptoMD5Append(&md5, owner_pad, 32);
_pdfioCryptoMD5Finish(&md5, digest);
// MD5 the result 50 more times...
for (i = 0; i < 50; i ++)
{
_pdfioCryptoMD5Init(&md5);
@ -1151,13 +1171,12 @@ pdfioFileSetPermissions(
_pdfioCryptoMD5Finish(&md5, digest);
}
// Copy the padded user password...
// Copy and encrypt the padded user password...
memcpy(pdf->owner_key, user_pad, sizeof(pdf->owner_key));
// Encrypt the result 20 times...
for (i = 0; i < 20; i ++)
{
uint8_t encrypt_key[16];// RC4 encryption key
uint8_t encrypt_key[16]; // RC4 encryption key
// XOR each byte in the digest with the loop counter to make a key...
for (j = 0; j < sizeof(encrypt_key); j ++)
@ -1178,7 +1197,6 @@ pdfioFileSetPermissions(
_pdfioCryptoMD5Init(&md5);
_pdfioCryptoMD5Append(&md5, user_pad, 32);
_pdfioCryptoMD5Append(&md5, pdf->owner_key, 32);
_pdfioCryptoMD5Append(&md5, perm_bytes, 4);
_pdfioCryptoMD5Append(&md5, file_id, file_id_len);
_pdfioCryptoMD5Finish(&md5, digest);
@ -1437,7 +1455,7 @@ load_obj_stream(pdfio_obj_t *obj) // I - Object to load
// Read the objects themselves...
for (cur_obj = 0; cur_obj < num_objs; cur_obj ++)
{
if (!_pdfioValueRead(obj->pdf, &tb, &(objs[cur_obj]->value)))
if (!_pdfioValueRead(obj->pdf, obj, &tb, &(objs[cur_obj]->value)))
{
pdfioStreamClose(st);
return (false);
@ -1615,7 +1633,7 @@ load_xref(pdfio_file_t *pdf, // I - PDF file
_pdfioTokenInit(&tb, pdf, (_pdfio_tconsume_cb_t)_pdfioFileConsume, (_pdfio_tpeek_cb_t)_pdfioFilePeek, pdf);
if (!_pdfioValueRead(pdf, &tb, &trailer))
if (!_pdfioValueRead(pdf, obj, &tb, &trailer))
{
_pdfioFileError(pdf, "Unable to read cross-reference stream dictionary.");
return (false);
@ -1863,7 +1881,7 @@ load_xref(pdfio_file_t *pdf, // I - PDF file
_pdfioTokenInit(&tb, pdf, (_pdfio_tconsume_cb_t)_pdfioFileConsume, (_pdfio_tpeek_cb_t)_pdfioFilePeek, pdf);
if (!_pdfioValueRead(pdf, &tb, &trailer))
if (!_pdfioValueRead(pdf, NULL, &tb, &trailer))
{
_pdfioFileError(pdf, "Unable to read trailer dictionary.");
return (false);
@ -1982,7 +2000,6 @@ write_trailer(pdfio_file_t *pdf) // I - PDF file
bool ret = true; // Return value
off_t xref_offset; // Offset to xref table
size_t i; // Looping var
unsigned char id_values[2][16]; // ID array values
// Write the xref table...
@ -2016,15 +2033,6 @@ write_trailer(pdfio_file_t *pdf) // I - PDF file
goto done;
}
_pdfioCryptoMakeRandom(id_values[0], sizeof(id_values[0]));
_pdfioCryptoMakeRandom(id_values[1], sizeof(id_values[1]));
if ((pdf->id_array = pdfioArrayCreate(pdf)) != NULL)
{
pdfioArrayAppendBinary(pdf->id_array, id_values[0], sizeof(id_values[0]));
pdfioArrayAppendBinary(pdf->id_array, id_values[1], sizeof(id_values[1]));
}
if ((pdf->trailer_dict = pdfioDictCreate(pdf)) == NULL)
{
_pdfioFileError(pdf, "Unable to create trailer.");
@ -2040,7 +2048,7 @@ write_trailer(pdfio_file_t *pdf) // I - PDF file
pdfioDictSetObj(pdf->trailer_dict, "Root", pdf->root_obj);
pdfioDictSetNumber(pdf->trailer_dict, "Size", pdf->num_objs + 1);
if (!_pdfioDictWrite(pdf->trailer_dict, NULL))
if (!_pdfioDictWrite(pdf->trailer_dict, NULL, NULL))
{
_pdfioFileError(pdf, "Unable to write trailer.");
ret = false;