Django (audio) File Validation

Question

I\'m experimenting with a site that will allow users to upload audio files. I\'ve read every doc that I can get my hands on but can\'t find much about validating files

Answer 1

You want to validate the file before it gets written to disk. When you upload a file, the form gets validated then the uploaded file gets passed to a handler/method that deals with the actual writing to the disk on your server. So in between these two operations, you want to perform some custom validation to make sure it's a valid audio file

You could:

• check if the the file is less then a certain size (good practice)
• then check if the submitted file has a certain content type (i.e. an audio file)
  • this is pretty useless as someone could easily spoof it
• then check that the file ends in a certain extension (or extensions)
  • this is also pretty useless
• try read the file and see if it's actually audio

(I haven't tested this code)

models.py

class UserSong(models.Model):
    title = models.CharField(max_length=100)
    audio_file = models.FileField()

forms.py

class UserSongForm(forms.ModelForm):
     # Add some custom validation to our file field
     def clean_audio_file(self):
         file = self.cleaned_data.get('audio_file',False):
         if file:
             if file._size > 4*1024*1024:
                   raise ValidationError("Audio file too large ( > 4mb )")
             if not file.content-type in ["audio/mpeg","audio/..."]:
                   raise ValidationError("Content-Type is not mpeg")
             if not os.path.splitext(file.name)[1] in [".mp3",".wav" ...]:
                   raise ValidationError("Doesn't have proper extension")
             # Here we need to now to read the file and see if it's actually 
             # a valid audio file. I don't know what the best library is to 
             # to do this
             if not some_lib.is_audio(file.content):
                   raise ValidationError("Not a valid audio file")
             return file
         else:
             raise ValidationError("Couldn't read uploaded file")

views.py from utils import handle_uploaded_file

def upload_file(request):
    if request.method == 'POST':
        form = UserSongForm(request.POST, request.FILES)
        if form.is_valid():
            # If we are here, the above file validation has completed
            # so we can now write the file to disk
            handle_uploaded_file(request.FILES['file'])
            return HttpResponseRedirect('/success/url/')
    else:
        form = UploadFileForm()
    return render_to_response('upload.html', {'form': form})

utils.py

# from django's docs
def handle_uploaded_file(f):
    ext = os.path.splitext(f.name)[1]
    destination = open('some/file/name%s'%(ext), 'wb+')
    for chunk in f.chunks():
        destination.write(chunk)
    destination.close()

https://docs.djangoproject.com/en/dev/topics/http/file-uploads/#file-uploads https://docs.djangoproject.com/en/dev/ref/forms/fields/#filefield https://docs.djangoproject.com/en/dev/ref/files/file/#django.core.files.File