检查是否安全链接

try:
from urlparse import urlparse, urljoin
except ImportError:
from urllib.parse import urlparse, urljoin

from flask import request, redirect, url_for, current_app

def is_safe_url(target):
ref_url = urlparse(request.host_url)
test_url = urlparse(urljoin(request.host_url, target))
return test_url.scheme in ('http', 'https') and ref_url.netloc == test_url.netloc

如果没有跳转链接，则返回首页

def redirect_back(default='blog.index', **kwargs):
for target in request.args.get('next'), request.referrer:
if not target:
continue
if is_safe_url(target):
return redirect(target)
return redirect(url_for(default, **kwargs))

允许上传的文件类型

def allowed_file(filename):
return '.' in filename and
filename.rsplit('.', 1)[1].lower() in current_app.config['FLASKBLOG_ALLOWED_IMAGE_EXTENSIONS']