用户登陆系统，采用Flask，SQLite，hmac编写

# -*- coding: utf-8 -*-
"""
Created on Sat Jun 30 10:56:19 2018

@author: lewisliu
"""

from flask import Flask
from flask import request
import sqlite3
import hmac


#def hmac_sha1(key, s):
#    return hmac.new(key.encode('utf-8'), s.encode('utf-8'), 'MD5').hexdigest()


app = Flask(__name__)



@app.route('/', methods=['GET', 'POST'])
def home():
    return '<h1>Home</h1>'


@app.route('/signin', methods=['GET'])
def signin_form():
    return'''<form action="/signin" method="post">
             <p>model<input name="model">(enroll/login/exit)</p>
             <p>username<input name="username"></p>
             <p>password<input name="password" type="password"></p>
             <p><button type="submit">Submit</button></p>
             </form>'''


@app.route('/signin', methods=['POST'])
def signin():
    # 需要从request对象读取表单内容：
    conn = sqlite3.connect('user_flask.db')
    cursor = conn.cursor()
    try:
        cursor.execute('create table userpass (name varchar(20) primary key, password varchar(20))')
    except Exception as e:
        pass
    if request.form['model']=='exit':
        conn.close()
        return'<h3>Good bay!</h3>'
    elif request.form['model']=='enroll':
        flag = cursor.execute("select name from userpass where name='%s'" % request.form['username']).fetchone()
        if flag:
            return'''<form action="/signin" method="post">
             <p>name exit!</p>
             <p>model<input name="model">(enroll/login/exit)</p>
             <p>username<input name="username"></p>
             <p>password<input name="password" type="password"></p>
             <p><button type="submit">Submit</button></p>
             </form>'''
        else:
            key = 'liu'  # ''.join([chr(random.randint(48, 122)) for i in range(20)])
            password = hmac.new(key.encode('utf-8'), request.form['password'].encode('utf-8'), 'MD5').hexdigest()
            cursor.execute("insert into userpass (name, password) values ('%s','%s')" % (request.form['username'], password))
            conn.commit()
            return'''<form action="/signin" method="post">
             <p>you enroll successful!</p>
             <p>model<input name="model">(enroll/login/exit)</p>
             <p>username<input name="username"></p>
             <p>password<input name="password" type="password"></p>
             <p><button type="submit">Submit</button></p>
             </form>'''
    elif request.form['model']=='login':
        key = 'liu'
        password = hmac.new(key.encode('utf-8'), request.form['password'].encode('utf-8'), 'MD5').hexdigest()
        flag = cursor.execute("select name and password from userpass where name = '%s' and password='%s'" % (request.form['username'], password)).fetchone()
        if flag:
            return'''<form action="/signin" method="post">
            <p>wellcome!</p>
            <p>model<input name="model">(enroll/login/exit)</p>
            <p>username<input name="username"></p>
            <p>password<input name="password" type="password"></p>
            <p><button type="submit">Submit</button></p>
            </form>'''
        else:
            return'''<form action="/signin" method="post">
                <p>Bad username or password!</p>
                <p>model<input name="model">(enroll/login/exit)</p>
                <p>username<input name="username"></p>
                <p>password<input name="password" type="password"></p>
                <p><button type="submit">Submit</button></p>
                </form>'''
    else:
        return'''<form action="/signin" method="post">
                <p>model wrong!</p>
                <p>model<input name="model">(enroll/login/exit)</p>
                <p>username<input name="username"></p>
                <p>password<input name="password" type="password"></p>
                <p><button type="submit">Submit</button></p>
                </form>'''


if __name__ == '__main__':
    app.run()