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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 python_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
self.python_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
if self.python_session is not None:
self.python_session.end()
self.python_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_python(self):
with self._access_lock:
if self.python_session is None:
self.python_session = python_session.PythonSession() # lazy init
return self.python_session
def get_problem_data(self, language, problem_group, problem):
mod = problems.load_problem(language, problem_group, problem, 'en')
mod_language = problems.load_language(language, 'en')
# Get generic and problem-specific hints.
hint = dict(mod_language.hint)
hint.update(mod.hint)
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': 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, 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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