Storing a username and password, then allowing user update. Python

Question

I am trying to create a program that asks the user for, in this example, lets say a username and password, then store this (I assume in a text file). The area I am struggling with is how to allow the user to update this their password stored in the text file? I am writing this in Python.

Answer 1

Because you've asked to focus on how to handle the updates in a text file, I've focused on that part of your question. So, in effect I've focused on answering how would you go about having something that changes in a text file when those changes impact the length and structure of the text file. That question is independent of the thing in the text file being a password. There are significant concerns related to whether you should store a password, or whether you should store some quantity that can be used to verify a password. All that depends on what you're trying to do, what your security model is, and on what else your program needs to interact with. You've ruled all that out of scope for your question by asking us to focus on the text file update part of the problem.

You might adopt the following pattern to accomplish this task:

• At the beginning see if the text file is present. Read it and if so assume you are doing an update rather than a new user

• Ask for the username and password. If it is an update prompt with the old values and allow them to be changed

• Write out the text file.

Most strategies for updating things stored in text files involve rewriting the text file entirely on every update.

Answer 2

import getpass
import os
import bcrypt

new=None

def two_hash():

 master_key = getpass.getpass('enter pass word ')

 salt = bcrypt.gensalt()

 combo =  salt + master_key

 hashed = bcrypt.hashpw(combo , salt)

 allow = raw_input('do you want to update pass ')


 if allow == 'y':

  new =  getpass.getpass('enter old pass word ')

  combo = salt + new

  bcrypt.hashpw(combo , salt)

  if ( bcrypt.hashpw(combo , salt) == hashed ):

   new = getpass.getpass('enter new pass ')

   print  new


 else :
  pass


if __name__ == '__main__':
 two_hash()

Note 1 : i wanted to split my code to some function but i can't so help for split it to some function

Answer 3

Is this a single user application that you have? If you can provide more information one where you're struggling

You can read the password file (which has usernames and passwords) - When user authenticate, match the username and password to the combination in text file - When user wants to change password, then user provides old and new password. The username and old password combination is compared to the one in text file and if matches, stores the new

Answer 4

Try using JSON. An example of a json file would be this:

{
    "Usernames": {
        "Username": [
            {
                "Password": "Password123"
            }
        ]
    }
}

Then to edit the json:

jsonloads = json.loads(open('json.json').read()) #Load the json

username = input("Enter your username: ") #Get username as a string
for i in jsonloads["Usernames"]: #Iterate through usernames
    if i == username: #If the username is what they entered
        passw = input("New password: ") #Ask for new password
        jsonloads["Usernames"][i][0]["Password"] = passw #Set the password
        jsonFile = open("json.json", "w+") #Open the json
        jsonFile.write(json.dumps(jsonloads, indent=4)) #Write
        jsonFile.close() #Close it 
        break #Break out of the for loop
else: #If it remains unbroken
    print("You aren't in the database. ")
    user = input("Username: ") #Ask for username
    passw = input("Password: ") #Ask for password for username
    item = {"Password":pass} #Make a dict
    jsonloads["Usernames"].update({user: item}) #Add that dict to "Usernames"
    with open('json.json','w') as f: #Open the json
        f.write(json.dumps(jsonloads, indent=4)) #Write

Something like that should work, haven't tested it though.

Also, remember to always encrypt passwords!