Add link, hashing, and renaming to Python upload script

The script below works great but it needs a few additions.

1. If the file is the same name as a file that's already exists, rename the existing file and then continue to upload the new file. Currently the old file is overwritten by the new file.
2. When the script displays the file has uploaded successfully it needs to display the file size and a calculated hash value in MD5 or SHA.
3. The display page also needs a link to go to another page as it currently requires interacting with the browser navigation to continue.

Thanks for any help in advance.

#!/usr/bin/env python
import cgi, os
import cgitb; cgitb.enable()
 
try: # Windows needs stdio set for binary mode.
    import msvcrt
    msvcrt.setmode (0, os.O_BINARY) # stdin  = 0
    msvcrt.setmode (1, os.O_BINARY) # stdout = 1
except ImportError:
    pass
 
form = cgi.FieldStorage()
 
# Generator to buffer file chunks
def fbuffer(f, chunk_size=10000):
   while True:
      chunk = f.read(chunk_size)
      if not chunk: break
      yield chunk
 
# A nested FieldStorage instance holds the file
fileitem = form['file']
 
# Test if the file was uploaded
if fileitem.filename:
 
   # strip leading path from file name to avoid directory traversal attacks
   fn = os.path.basename(fileitem.filename)
   f = open('/var/www/dropbox/' + fn, 'wb', 10000)
 
   # Read the file in chunks
   for chunk in fbuffer(fileitem.file):
      f.write(chunk)
   f.close()
   message = 'The file "' + fn + '" was uploaded successfully'
 
else:
   message = 'No file was uploaded'
 
print """\
Content-Type: text/html\n
<html><body>
<p>%s</p>
</body></html>
""" % (message,)

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Okay, first the hashing. From what I've read I have to open it in binary mode. If I try just using the fileitem from the instance the script complains that the data must be in a string or read-only binary. I've tried to again open the file for obtaining the hash value but it doesn't work and even if it did it seems that it would be rather inefficient to hash after testing to see if the file was uploaded. Can the hashing not occur as the file is being read into buffer or written to the file-system?

#!/usr/bin/env python
import cgi, os
import cgitb; cgitb.enable()
#import os.path
import hashlib
 
 
try: # Windows needs stdio set for binary mode.
    import msvcrt
    msvcrt.setmode (0, os.O_BINARY) # stdin  = 0
    msvcrt.setmode (1, os.O_BINARY) # stdout = 1
except ImportError:
    pass
 
form = cgi.FieldStorage()
 
# Generator to buffer file chunks
def fbuffer(f, chunk_size=10000):
   while True:
      chunk = f.read(chunk_size)
      if not chunk: break
      yield chunk
 
# A nested FieldStorage instance holds the file
fileitem = form['file']
 
# Create a MD5 hash of the new file
#hexdigest = hashlib.md5(fileitem).hexdigest()
#datalength = len(fileitem)
 
# Test if the file was uploaded
if fileitem.filename:
 
   # strip leading path from file name to avoid directory traversal attacks
   fn = os.path.basename(fileitem.filename)
   f = open('/var/www/apache2-default/' + fn, 'wb', 10000)
 
   # Read the file in chunks
   for chunk in fbuffer(fileitem.file):
      f.write(chunk)
   f.close()
 
# Create a MD5 hash of the new file
f = open('/var/www/apache2-default/' + fn, 'rb', 10000).read()
hexdigest = hashlib.md5(fileitem.file).hexdigest()
datalength = len(fileitem.file)
f.close()
 
   message = 'The file "' + fn + '" was uploaded successfully with a hash value of ' + hexdigest + ', click <a href="#">here</a> to go back.'
 
else:
   message = 'No file was uploaded'
 
print """\
Content-Type: text/html\n
<html><body>
<p>%s</p>
</body></html>
""" % (message,)

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h = hashlib.md5() datalength = 0 for chunk in fbuffer(fileitem.file): f.write(chunk) h.update(chunk) datalength += len(chunk) hexdigest = h.hexdigest()

h = hashlib.md5() datalength = 0 # Read the file in chunks for chunk in fbuffer(fileitem.file): f.write(chunk) h.update(chunk) datalength += len(chunk) hexdigest = h.hexdigest() f.close()

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Add link, hashing, and renaming to Python upload script

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