Adds VPN Handler

JIRA: N/A

adds a vpn handler in source/api/vpn.py
vpn.py contains a formal interface definition as well as a specific
implementation using LDAP. If your lab's vpn does not use LDAP, you may
create a new vpn handler that properly extends the abstract vpn class
and it should be fine.

Change-Id: I31e8d8477dfed913c4da864d3ff3b49e988d64b1
Signed-off-by: Parker Berberian <pberberian@iol.unh.edu>

1 files changed, 235 insertions, 0 deletions

diff --git a/source/api/vpn.py b/source/api/vpn.py
new file mode 100644
index 0000000..336a681
--- /dev/null
+++ b/source/api/vpn.py
@@ -0,0 +1,235 @@
+from abc import ABCMeta, abstractmethod
+import ldap
+import os
+import random
+from base64 import b64encode
+from database import BookingDataBase
+
+
+class VPN_BaseClass:
+    """
+    the vpn handler abstract class / interface
+
+    """
+    __metaclass__ = ABCMeta
+
+    @abstractmethod
+    def __init__(self, config):
+        """
+        config is the parsed vpn.yaml file
+        """
+        pass
+
+    @abstractmethod
+    def makeNewUser(self, user=None):
+        """
+        This method is called when a vpn user is needed.
+        This method should create a vpn user in whatever
+        runs the vpn in our infrastructure. returns the
+        credentials for the vpn user and some uid
+        that will be associated with the booking in the
+        database. This uid is used to track the vpn user and
+        to delete the user when there are no bookings associated
+        with that uid.
+        """
+        user = "username"
+        passwd = "password"
+        uid = "some way for you to identify this user in the database"
+        return user, passwd, uid
+
+    @abstractmethod
+    def removeOldUsers(self):
+        """
+        checks the list of all vpn users against a list of
+        vpn users associated with active bookings and removes
+        users who dont have an active booking
+
+        If you want your vpn accounts to be persistent,
+        you can just ignore this
+        """
+        pass
+
+
+names = [
+    'frodo baggins', 'samwise gamgee', 'peregrin took', 'meriadoc brandybuck',
+    'bilbo baggins', 'gandalf grey', 'aragorn dunadan', 'arwen evenstar',
+    'saruman white', 'pippin took', 'merry brandybuck', 'legolas greenleaf',
+    'gimli gloin', 'anakin skywalker', 'padme amidala', 'han solo',
+    'jabba hut', 'mace windu', 'sount dooku', 'qui-gon jinn',
+    'admiral ackbar', 'emperor palpatine'
+]
+
+
+class VPN:
+    """
+    This class communicates with the ldap server to manage vpn users.
+    This class extends the above ABC, and implements the makeNewUser,
+    removeOldUser, and __init__ abstract functions you must override to
+    extend the VPN_BaseClass
+    """
+
+    def __init__(self, config):
+        """
+        init takes the parsed vpn config file as an arguement.
+        automatically connects and authenticates on the ldap server
+        based on the configuration file
+        """
+        self.config = config
+        server = config['server']
+        self.uri = "ldap://"+server
+
+        self.conn = None
+        user = config['authentication']['user']
+        pswd = config['authentication']['pass']
+        if os.path.isfile(pswd):
+            pswd = open(pswd).read()
+        self.connect(user, pswd)
+
+    def connect(self, root_dn, root_pass):
+        """
+        Opens a connection to the server in the config file
+        and authenticates as the given user
+        """
+        self.conn = ldap.initialize(self.uri)
+        self.conn.simple_bind_s(root_dn, root_pass)
+
+    def addUser(self, full_name, passwd):
+        """
+        Adds a user to the ldap server. Creates the new user with the classes
+        and in the directory given in the config file.
+        full_name should be two tokens seperated by a space. The first token
+        will become the username
+        private helper function for the makeNewUser()
+        """
+        first = full_name.split(' ')[0]
+        last = full_name.split(' ')[1]
+        user_dir = self.config['directory']['user']
+        user_dir += ','+self.config['directory']['root']
+        dn = "uid=" + first + ',' + user_dir
+        record = [
+                ('objectclass', ['top', 'inetOrgPerson']),
+                ('uid', first),
+                ('cn', full_name),
+                ('sn', last),
+                ('userpassword', passwd),
+                ('ou', self.config['directory']['user'].split('=')[1])
+                ]
+        self.conn.add_s(dn, record)
+        return dn
+
+    def makeNewUser(self, name=None):
+        """
+        creates a new user in the ldap database, with the given name
+        if supplied. If no name is given, we will try to select from the
+        pre-written list above, and will resort to generating a random string
+        as a username if the preconfigured names are all taken.
+        Returns the username and password the user needs to authenticate, and
+        the dn that we can use to manage the user.
+        """
+        if name is None:
+            i = 0
+            while not self.checkName(name):
+                i += 1
+                if i == 20:
+                    name = self.randoString(8)
+                    name += ' '+self.randoString(8)
+                    break  # generates a random name to prevent infinite loop
+                name = self.genUserName()
+        passwd = self.randoString(15)
+        dn = self.addUser(name, passwd)
+        return name, passwd, dn
+
+    def checkName(self, name):
+        """
+        returns true if the name is available
+        """
+        if name is None:
+            return False
+        uid = name.split(' ')[0]
+        base = self.config['directory']['user'] + ','
+        base += self.config['directory']['root']
+        filtr = '(uid=' + uid + ')'
+        timeout = 5
+        ans = self.conn.search_st(
+                base,
+                ldap.SCOPE_SUBTREE,
+                filtr,
+                timeout=timeout
+                )
+        return len(ans) < 1
+
+    @staticmethod
+    def randoString(n):
+        """
+        uses /dev/urandom to generate a random string of length n
+        """
+        n = int(n)
+        # defines valid characters
+        alpha = 'abcdefghijklmnopqrstuvwxyz'
+        alpha_num = alpha
+        alpha_num += alpha.upper()
+        alpha_num += "0123456789"
+
+        # generates random string from /dev/urandom
+        rnd = b64encode(os.urandom(3*n)).decode('utf-8')
+        random_string = ''
+        for char in rnd:
+            if char in alpha_num:
+                random_string += char
+        return str(random_string[:n])
+
+    def genUserName(self):
+        """
+        grabs a random name from the list above
+        """
+        i = random.randint(0, len(names) - 1)
+        return names[i]
+
+    def deleteUser(self, dn):
+        self.conn.delete(dn)
+
+    def getAllUsers(self):
+        """
+        returns all the user dn's in the ldap database in a list
+        """
+        base = self.config['directory']['user'] + ','
+        base += self.config['directory']['root']
+        filtr = '(objectclass='+self.config['user']['objects'][-1]+')'
+        timeout = 10
+        ans = self.conn.search_st(
+                base,
+                ldap.SCOPE_SUBTREE,
+                filtr,
+                timeout=timeout
+                )
+        users = []
+        for user in ans:
+            users.append(user[0])  # adds the dn of each user
+        return users
+
+    def removeOldUsers(self):
+        """
+        removes users from the ldap server who dont have any active bookings.
+        will not delete a user if their uid's are named in the config
+        file as permanent users.
+        """
+        db = self.config['database']
+        # the dn of all users who have an active booking
+        active_users = BookingDataBase(db).getVPN()
+        all_users = self.getAllUsers()
+        for user in all_users:
+            # checks if they are a permanent user
+            if self.is_permanent_user(user):
+                continue
+            # deletes the user if they dont have an active booking
+            if user not in active_users:
+                self.deleteUser(user)
+
+    def is_permanent_user(self, dn):
+        for user in self.config['permanent_users']:
+            if (user in dn) or (dn in user):
+                return True
+        return False
+
+
+VPN_BaseClass.register(VPN)