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# coding=utf-8
import uuid
import threading # multiprocessing.managers.BaseManager uses threading to serve incoming requests
import hashlib
import base64
import random
from . import prolog_session
from . import problems
import db
from errors.session import NoSuchSession, AuthenticationFailed
import psycopg2.extras
__all__ = ['get_session_by_id', 'get_or_create_session', 'UserSession']
sessions = {} # maps session IDs to session objects
module_access_lock = threading.Lock() # use this lock to access the sessions dictionary
class UserSession(object):
"""Abstracts a user session.
Only public methods are available to the outside world due to the use of multiprocessing managers.
Therefore prefix any private methods with an underscore (_).
No properties are accessible; use getters and setters instead.
Values are passed by value instead of by reference (deep copy!).
"""
def __init__(self, uid, username):
self._access_lock = threading.Lock()
self.sid = uuid.uuid4().hex
self.uid = uid
self.username = username
self.prolog_session = None
def destroy(self):
"""Destroys the session."""
with self._access_lock:
with module_access_lock:
del sessions[self.sid]
if self.prolog_session is not None:
self.prolog_session.end()
self.prolog_session = None
# TODO: add any cleanups as features are added!
def get_sid(self):
return self.sid
def get_uid(self):
return self.uid
def get_prolog(self):
with self._access_lock:
if self.prolog_session is None:
self.prolog_session = prolog_session.PrologSession() # lazy init
return self.prolog_session
def get_problem_data(self, language, problem_group, problem):
mod = problems.load_problem(language, problem_group, problem, 'en')
conn = db.get_connection()
try:
cur = conn.cursor()
try:
cur.execute("select l.id, l.name, g.id, g.name, p.id, p.name from problem p inner join language l on l.id = p.language_id inner join problem_group g on g.id = p.problem_group_id where l.identifier = %s and g.identifier = %s and p.identifier = %s", (language, problem_group, problem))
row = cur.fetchone()
problem_id = row[4]
result = {
'language': {'id': row[0], 'identifier': language, 'name': row[1]},
'problem_group': {'id': row[2], 'identifier': problem_group, 'name': row[3]},
'problem': {'id': problem_id, 'identifier': problem, 'name': row[5], 'slug': mod.slug, 'description': mod.description, 'hint': mod.hint}
}
cur.execute("select content from solution where problem_id = %s and codeq_user_id = %s", (problem_id, self.uid))
row = cur.fetchone()
if row:
result['solution'] = row[0]
else:
result['solution'] = ''
return result
finally:
cur.close()
finally:
conn.commit()
db.return_connection(conn)
def update_solution(self, problem_id, trace, solution):
if (trace is None) and (solution is None):
return
conn = db.get_connection()
try:
cur = conn.cursor()
try:
# TODO: convert to upsert with postgresql 9.5 to eliminate the small window where it's possible for more than one concurrent insert to execute
cur.execute('select id, trace, solution, content from solution where codeq_user_id = %s and problem_id = %s for update', (self.uid, problem_id))
row = cur.fetchone()
if row:
if row[1]:
new_trace = row[1]
if trace:
new_trace.extend(trace)
else:
new_trace = trace
new_solution = row[2] if solution is None else solution
cur.execute('update solution set content = %s, trace = %s where id = %s', (new_solution, psycopg2.extras.Json(new_trace), row[0]))
else:
# this is the first entry
cur.execute('insert into solution (done, content, problem_id, codeq_user_id, trace) values (%s, %s, %s, %s, %s)', (False, solution, problem_id, self.uid, psycopg2.extras.Json(trace)))
finally:
cur.close()
conn.commit()
except:
conn.rollback()
raise
finally:
db.return_connection(conn)
def __del__(self):
# no locking needed if GC is removing us, as there cannot be any concurrent access by definition
if hasattr(self, 'prolog_session') and (self.prolog_session is not None):
self.prolog_session.end()
self.prolog_session = None
# TODO: add any cleanups as features are added!
def get_session_by_id(sid):
with module_access_lock:
s = sessions.get(sid, None)
if s is None:
raise NoSuchSession('There is no session with SID {}'.format(sid))
return s
def get_or_create_session(uid, username, sid=None):
with module_access_lock:
if sid is not None:
s = sessions.get(sid)
if s is not None:
return s
s = UserSession(uid, username)
sessions[s.sid] = s
return s
def authenticate_and_create_session(username, password):
conn = db.get_connection()
try:
cur = conn.cursor()
try:
cur.execute('select id, password from codeq_user where username = %s', (username,))
row = cur.fetchone()
if row is None:
raise AuthenticationFailed('No such user: {}'.format(username))
if verify_password(password, row[1]):
return get_or_create_session(row[0], username)
raise AuthenticationFailed('Password mismatch')
finally:
cur.close()
finally:
conn.commit()
db.return_connection(conn)
def verify_password(plain_password, encrypted_password):
elts = encrypted_password.split('$')
if len(elts) != 4:
return False
if elts[0] != 'pbkdf2_sha256':
return False
try:
rounds = int(elts[1])
except:
return False
enc = hashlib.pbkdf2_hmac('sha256', plain_password.encode('utf-8'), elts[2].encode('utf-8'), rounds)
return base64.b64encode(enc).decode('utf-8') == elts[3]
_salt_chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
_salt_chars_len = len(_salt_chars)
def encrypt_password(plain_password):
rounds = 20000
chosen_chars = []
for i in range(0, 12):
chosen_chars.append(_salt_chars[random.randrange(0, _salt_chars_len)])
salt = ''.join(chosen_chars)
enc = hashlib.pbkdf2_hmac('sha256', plain_password.encode('utf-8'), salt.encode('utf-8'), rounds)
return '{0}${1}${2}${3}'.format('pbkdf2_sha256', rounds, salt, base64.b64encode(enc).decode('utf-8'))
random.seed()
# TODO: add a session timeout timer
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