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该漏洞是一个CTFd的账户接管漏洞,在注册和修改密码处,存在逻辑漏洞,从而导致可以修改任意账号密码。
影响版本:v2.0.0-2.2.2
首先定位到用户注册处:/CTFd/auto.py
@auth.route("/register", methods=["POST", "GET"]) @check_registration_visibility @ratelimit(method="POST", limit=10, interval=5) def register(): errors = get_errors() if request.method == "POST": name = request.form["name"] email_address = request.form["email"] password = request.form["password"] name_len = len(name) == 0 names = Users.query.add_columns("name", "id").filter_by(name=name).first() emails = ( Users.query.add_columns("email", "id") .filter_by(email=email_address) .first() ) pass_short = len(password.strip()) == 0 pass_long = len(password) > 128 valid_email = validators.validate_email(request.form["email"]) team_name_email_check = validators.validate_email(name) if not valid_email: errors.append("Please enter a valid email address") if email.check_email_is_whitelisted(email_address) is False: errors.append( "Only email addresses under {domains} may register".format( domains=get_config("domain_whitelist") ) ) if names: errors.append("That user name is already taken") if team_name_email_check is True: errors.append("Your user name cannot be an email address") if emails: errors.append("That email has already been used") if pass_short: errors.append("Pick a longer password") if pass_long: errors.append("Pick a shorter password") if name_len: errors.append("Pick a longer user name") if len(errors) > 0: return render_template( "register.html", errors=errors, name=request.form["name"], email=request.form["email"], password=request.form["password"], ) else: with app.app_context(): user = Users( name=name.strip(), email=email_address.lower(), password=password.strip(), ) db.session.add(user) db.session.commit() db.session.flush() login_user(user) if config.can_send_mail() and get_config( "verify_emails" ): # Confirming users is enabled and we can send email. log( "registrations", format="[{date}] {ip} - {name} registered (UNCONFIRMED) with {email}", ) email.verify_email_address(user.email) db.session.close() return redirect(url_for("auth.confirm")) else: # Don't care about confirming users if ( config.can_send_mail() ): # We want to notify the user that they have registered. email.sendmail( request.form["email"], "You've successfully registered for {}".format( get_config("ctf_name") ), ) log("registrations", "[{date}] {ip} - {name} registered with {email}") db.session.close() if is_teams_mode(): return redirect(url_for("teams.private")) return redirect(url_for("challenges.listing")) else: return render_template("register.html", errors=errors)
上述代码,有一大半是进行输入检测的,提取出来关键部分:
def register(): errors = get_errors() if request.method == "POST": name = request.form["name"] email_address = request.form["email"] password = request.form["password"] name_len = len(name) == 0 names = Users.query.add_columns("name", "id").filter_by(name=name).first() emails = ( Users.query.add_columns("email", "id") .filter_by(email=email_address) .first() ) pass_short = len(password.strip()) == 0 pass_long = len(password) > 128 valid_email = validators.validate_email(request.form["email"]) team_name_email_check = validators.validate_email(name) if len(errors) > 0: #检测出错 '''注册账户密码插入数据库''' else: with app.app_context(): user = Users( name=name.strip(), email=email_address.lower(), password=password.strip(), ) db.session.add(user) db.session.commit() db.session.flush() login_user(user) if config.can_send_mail() and get_config( "verify_emails" ): # Confirming users is enabled and we can send email. log( "registrations", format="[{date}] {ip} - {name} registered (UNCONFIRMED) with {email}", ) email.verify_email_address(user.email) db.session.close() return redirect(url_for("auth.confirm"))
上方的上半部分,接受用户的输入信息:
def register(): errors = get_errors() if request.method == "POST": name = request.form["name"] email_address = request.form["email"] password = request.form["password"] name_len = len(name) == 0 names = Users.query.add_columns("name", "id").filter_by(name=name).first() emails = ( Users.query.add_columns("email", "id") .filter_by(email=email_address) .first() ) pass_short = len(password.strip()) == 0 pass_long = len(password) > 128 valid_email = validators.validate_email(request.form["email"]) team_name_email_check = validators.validate_email(name)
其关键在于这里:
names = Users.query.add_columns("name", "id").filter_by(name=name).first()
在判断用户是否已经注册时,是直接用的name,也就是用户输入的账户名,并且没有任何的过滤。
在下半部分,注册成功时,将账户、密码、邮箱插入到数据库中:
with app.app_context(): user = Users( name=name.strip(), email=email_address.lower(), password=password.strip(), ) db.session.add(user) db.session.commit() db.session.flush()
但是这里又对用户输入的账户进行了去除空格的操作。(也就是说,如果数据库中存在m1sn0w这个账户,但是,如果我在注册时输入的账户名为:空格m1sn0w,那么,注册时不会提示账户已存在,而是将m1sn0w这个用户名插入到数据库中,也就是数据库中有了同名用户)
接下来是第二个利用点(修改密码):提取出主要代码
@auth.route("/reset_password", methods=["POST", "GET"]) @auth.route("/reset_password/<data>", methods=["POST", "GET"]) @ratelimit(method="POST", limit=10, interval=60) def reset_password(data=None): if data is not None: try: name = unserialize(data, max_age=1800) except (BadTimeSignature, SignatureExpired): return render_template( "reset_password.html", errors=["Your link has expired"] ) except (BadSignature, TypeError, base64.binascii.Error): return render_template( "reset_password.html", errors=["Your reset token is invalid"] ) if request.method == "GET": return render_template("reset_password.html", mode="set") if request.method == "POST": user = Users.query.filter_by(name=name).first_or_404() user.password = request.form["password"].strip() db.session.commit() log( "logins", format="[{date}] {ip} - successful password reset for {name}", name=name, ) db.session.close() return redirect(url_for("auth.login"))
我们知道,在修改密码时,会向相应的邮箱发送一封邮件,点击之后,才能修改密码。(上面的data值,也就是发送给指定邮箱的URL后面的一串值)
接下来,看看data值是什么:/CTFd/utils/email/__init__.py
def forgot_password(email, team_name): token = serialize(team_name) text = """Did you initiate a password reset? Click the following link to reset your password: {0}/{1} """.format( url_for("auth.reset_password", _external=True), token ) return sendmail(email, text)
可以看到,它是将用户名序列化之后,拼接到相应URL后面,发送给邮箱。(通过前面的分析,我们知道数据库中的账号有两个是同名,那么进行修改密码操作时,就会修改第一个用户的密码)
(有些文章说需要修改当前用户为其他的用户名,但感觉好像不需要)
if request.method == "POST": user = Users.query.filter_by(name=name).first_or_404() user.password = request.form["password"].strip() db.session.commit()
它这里取出来的用户就是第一个用户(也就是先前注册的那个用户)
所以,大致的利用方法如下:
1、注册一个账号,和想要修改的那个用户名同名,但在注册时加上空格
2、点击修改密码,在邮箱确认,即可修改指定用户密码
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