How can I decode a .bin into a .pdf

Question

I extracted an embedded object from an excel spreadsheet that was a pdf but the excel zip file saves embedded objects as binary files.

I am trying to read the binary file and return it to it's original format as a pdf. I took some code from another question with a similar issue but when i try opening the pdf adobe gives error "can't open because file is damaged...not decoded correctly.."

Does anyone know of a way to do this?

with open('oleObject1.bin','rb') as f: 
    binaryData = f.read() 
print(binaryData)

with open(os.path.expanduser('test1.pdf'), 'wb') as fout:
    fout.write(base64.decodebytes(binaryData))

Link to the object file on github

Can you post the "binary file" here to your question, so others can see what you got from excel? — Ryan, Jun 14 '19 at 22:02

score 4 · Answer 1 · answered Jun 24 '19 at 19:32

Thanks Ryan, I was able to see what you are talking about. Here is solution for future reference.

str1 = b'%PDF-'  # Begin PDF
str2 = b'%%EOF'  # End PDF

with open('oleObject1.bin', 'rb') as f:
    binary_data = f.read()
print(binary_data)

# Convert BYTE to BYTEARRAY
binary_byte_array = bytearray(binary_data)

# Find where PDF begins
result1 = binary_byte_array.find(str1)
print(result1)

# Remove all characters before PDF begins
del binary_byte_array[:result1]
print(binary_byte_array)

# Find where PDF ends
result2 = binary_byte_array.find(str2)
print(result2)

# Subtract the length of the array from the position of where PDF ends (add 5 for %%OEF characters)
# and delete that many characters from end of array
print(len(binary_byte_array))
to_remove = len(binary_byte_array) - (result2 + 5)
print(to_remove)

del binary_byte_array[-to_remove:]
print(binary_byte_array)

with open(os.path.expanduser('test1.pdf'), 'wb') as fout:
    fout.write(binary_byte_array)

score 3 · Answer 2 · answered Jun 17 '19 at 17:43

3

The bin file contains a valid PDF. There is no decoding required. The bin file though does have bytes before and after the PDF that need to be trimmed.

To get the first byte look for the first occurrence of string %PDF-

To get the final byte look for the last %%EOF.

Note, I do not know what "format" the leading/trailing bytes are, that are added by Excel. The solution above obliviously would not work if either of the ascii strings above could also be in the leading/trailing data.

answered Jun 17 '19 at 17:43

Ryan

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Hi Ryan, I solved this issue but I have another question. What if the file is a VSD or DOCX or another type. Is there some first and last occurrence of other types of files like there is with PDF? – Matthew Martinez Jul 10 '19 at 19:18

score 0 · Answer 3 · answered Jun 13 '19 at 20:58

0

You should try using a python library that allows you to write pdf files like reportlab or pyPDF

answered Jun 13 '19 at 20:58

xeno097

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How can I decode a .bin into a .pdf

3 Answers3

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