mirror of
https://github.com/Leseratte10/acsm-calibre-plugin
synced 2024-12-27 09:58:19 +01:00
c508280319
Some PDFs apparently use nonstandard spacing in the /Encrypt blob which my parser didn't like. Hopefully this fixes it? Related to #44
288 lines
No EOL
7.6 KiB
Python
288 lines
No EOL
7.6 KiB
Python
import sys, os, zlib, base64, time
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class BackwardReader:
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def __init__(self, file):
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self.file = file
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def readlines(self):
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BLKSIZE = 4096
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# Move reader to the end of file
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self.file.seek(0, os.SEEK_END)
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if sys.version_info[0] >= 3:
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buffer = bytearray()
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else:
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buffer = ""
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while True:
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if sys.version_info[0] >= 3:
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pos_newline = buffer.rfind(bytes([0x0a]))
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else:
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pos_newline = buffer.rfind("\n")
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# Get the current position of the reader
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current_pos = self.file.tell()
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if pos_newline != -1:
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# Newline is found
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line = buffer[pos_newline+1:]
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buffer = buffer[:pos_newline]
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if sys.version_info[0] >= 3:
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yield line.decode("latin-1")
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else:
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yield line
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elif current_pos:
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# Need to fill the buffer
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to_read = min(BLKSIZE, current_pos)
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self.file.seek(current_pos-to_read, 0)
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buffer = self.file.read(to_read) + buffer
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self.file.seek(current_pos-to_read, 0)
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if current_pos is to_read:
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if sys.version_info[0] >= 3:
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buffer = bytes([0x0a]) + buffer
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else:
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buffer = "\n" + buffer
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else:
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# Start of file
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return
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def trim_encrypt_string(encrypt):
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string_list = list(encrypt)
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strlen = len(encrypt)
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i = 0
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bracket_count = 0
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while (i < strlen):
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if string_list[i] == "<" and string_list[i+1] == "<":
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bracket_count += 1
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if string_list[i] == ">" and string_list[i+1] == ">":
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bracket_count -= 1
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if bracket_count == 0:
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break
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i = i + 1
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len_to_use = i+2
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return encrypt[0:len_to_use]
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def cleanup_encrypt_element(element):
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if element.startswith("ID[<"):
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element = element.replace("><", "> <")
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element = ' '.join(element.split())
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element = element.replace("[ ", "[").replace("] ", "]")
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return element
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def deflate_and_base64_encode( string_val ):
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zlibbed_str = zlib.compress( string_val )
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compressed_string = zlibbed_str[2:-4]
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return base64.b64encode( compressed_string )
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def update_ebx_with_keys(ebx_data, adept_license, ebx_bookid):
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b64data = deflate_and_base64_encode(adept_license.encode("utf-8")).decode("utf-8")
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ebx_new = ebx_data[:-2]
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ebx_new += "/EBX_BOOKID(%s)/ADEPT_LICENSE(%s)>>" % (ebx_bookid, b64data)
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return ebx_new
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def find_ebx(filename_in):
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find_ebx_start = int(time.time() * 1000)
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i = 0
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fl = open(filename_in, "rb")
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br = BackwardReader(fl)
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for line in br.readlines():
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i = i + 1
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if "/EBX_HANDLER/" in line:
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find_ebx_end = int(time.time() * 1000)
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print("Found EBX after %d attempts - took %d ms" % (i, find_ebx_end - find_ebx_start))
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return line
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find_ebx_end = int(time.time() * 1000)
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print("Error: Did not find EBX_HANDLER - took %d ms" % (find_ebx_end - find_ebx_start))
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return None
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def find_enc(filename_in):
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find_enc_start = int(time.time() * 1000)
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i = 0
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fl = open(filename_in, "rb")
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br = BackwardReader(fl)
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for line in br.readlines():
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i = i + 1
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is_encrypt_normal = "R/Encrypt" in line and "R/ID" in line
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is_encrypt_odd = "R" in line and "/Encrypt" in line and "/ID" in line
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if is_encrypt_normal or is_encrypt_odd:
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find_enc_end = int(time.time() * 1000)
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print("Found ENC after %d attempts - took %d ms" % (i, find_enc_end - find_enc_start))
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if is_encrypt_odd:
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print("Odd formatting of encryption blob?")
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print("If this doesn't work correctly please open a bug report.")
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return line
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find_enc_end = int(time.time() * 1000)
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print("Error: Did not find ENC - took %d ms" % (find_enc_end - find_enc_start))
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return None
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def patch_drm_into_pdf(filename_in, adept_license_string, filename_out, ebx_bookid):
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drm_start_time = int(time.time() * 1000)
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trailer = ""
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trailer_idx = 0
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startxref_offset = 0
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prevline = ""
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fl = open(filename_in, "rb")
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br = BackwardReader(fl)
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print("Searching for startxref ...")
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for line in br.readlines():
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trailer_idx += 1
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trailer = line + "\n" + trailer
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#print ("LINE: " + line)
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if (trailer_idx > 10):
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print("Took more than 10 attempts to find startxref ...")
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return False
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if (line == "startxref"):
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startxref_offset = int(prevline)
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print("Got startxref: %d" % (startxref_offset))
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break
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prevline = line
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r_encrypt_offs1 = 0
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r_encrypt_offs2 = 0
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encrypt = None
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encrypt = find_enc(filename_in)
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if encrypt is None:
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print("Error, enc not found")
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return False
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line_split = encrypt.split(' ')
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next = 0
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for element in line_split:
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if element == "R/Encrypt" or element == "/Encrypt":
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next = 2
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continue
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if next == 2:
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r_encrypt_offs1 = element
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next = 1
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continue
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if next == 1:
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r_encrypt_offs2 = element
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next = 0
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continue
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# read EBX element:
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ebx_elem = find_ebx(filename_in)
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if (ebx_elem is None):
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print("Err: EBX is None")
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return False
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print("")
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print("")
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print("Encryption handler:")
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print(encrypt)
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print("EBX handler:")
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print(ebx_elem)
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encrypt = trim_encrypt_string(encrypt)
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print("Trimmed encryption handler:")
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print(encrypt)
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ebx_elem = update_ebx_with_keys(ebx_elem, adept_license_string, ebx_bookid)
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print("Updated EBX handler not logged due to sensitive data")
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#print(ebx_elem)
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filesize_str = str(os.path.getsize(filename_in))
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filesize_pad = filesize_str.zfill(10)
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additional_data = "\r"
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additional_data += r_encrypt_offs1 + " " + r_encrypt_offs2 + " " + "obj" + "\r"
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additional_data += ebx_elem
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additional_data += "\r"
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additional_data += "endobj"
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ptr = int(filesize_str) + len(additional_data)
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additional_data += "\rxref\r" + r_encrypt_offs1 + " " + str((int(r_encrypt_offs2) + 1)) + "\r"
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additional_data += filesize_pad + " 00000 n" + "\r\n"
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additional_data += "trailer"
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additional_data += "\r"
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arr_root_str = encrypt.split('/')
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did_prev = False
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for elem in arr_root_str:
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if elem.startswith("Prev"):
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did_prev = True
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additional_data += "Prev " + str(startxref_offset)
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#print("Replacing prev from '%s' to '%s'" % (elem, "Prev " + startxref))
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else:
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additional_data += cleanup_encrypt_element(elem)
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additional_data += "/"
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if not did_prev:
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# remove two >> at end
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additional_data = additional_data[:-3]
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additional_data += "/Prev " + str(startxref_offset) + ">>" + "/"
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#print("Faking Prev %s" % startxref)
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additional_data = additional_data[:-1]
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additional_data += "\r" + "startxref\r" + str(ptr) + "\r" + "%%EOF"
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#print("Appending DRM data: %s" % (additional_data))
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inp = open(filename_in, "rb")
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out = open(filename_out, "wb")
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out.write(inp.read())
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out.write(additional_data.encode("latin-1"))
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inp.close()
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out.close()
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drm_end_time = int(time.time() * 1000)
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print("Whole DRM patching took %d milliseconds." % (drm_end_time - drm_start_time))
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return True |