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# IVLE - Informatics Virtual Learning Environment
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# Copyright (C) 2007-2008 The University of Melbourne
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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# Code to talk to the PostgreSQL database.
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# (This is the Data Access Layer).
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# All DB code should be in this module to ensure portability if we want to
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# change the DB implementation.
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# This means no SQL strings should be outside of this module. Add functions
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# here to perform the activities needed, and place the SQL code for those
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# CAUTION to editors of this module.
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# All string inputs must be sanitized by calling _escape before being
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# formatted into an SQL query string.
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from common import (caps, user)
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"""Wrapper around pg.escape_string. Prepares the Python value for use in
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SQL. Returns a string, which may be safely placed verbatim into an SQL
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Handles the following types:
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* str: Escapes the string, and also quotes it.
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* int/long/float: Just converts to an unquoted string.
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* bool: Returns as "TRUE" or "FALSE", unquoted.
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* NoneType: Returns "NULL", unquoted.
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* common.caps.Role: Returns the role as a quoted, lowercase string.
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Raises a DBException if val has an unsupported type.
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# "E'" is postgres's way of making "escape" strings.
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# Such strings allow backslashes to escape things. Since escape_string
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# converts a single backslash into two backslashes, it needs to be fed
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# Ref: http://www.postgresql.org/docs/8.2/static/sql-syntax-lexical.html
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# WARNING: PostgreSQL-specific code
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elif isinstance(val, str):
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return "E'" + pg.escape_string(val) + "'"
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elif isinstance(val, bool):
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return "TRUE" if val else "FALSE"
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elif isinstance(val, int) or isinstance(val, long) \
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or isinstance(val, float):
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elif isinstance(val, caps.Role):
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return _escape(str(val))
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raise DBException("Attempt to insert an unsupported type "
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def _passhash(password):
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return md5.md5(password).hexdigest()
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class DBException(Exception):
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"""A DBException is for bad conditions in the database or bad input to
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these methods. If Postgres throws an exception it does not get rebadged.
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This is only for additional exceptions."""
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"""An IVLE database object. This object provides an interface to
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interacting with the IVLE database without using any external SQL.
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Most methods of this class have an optional dry argument. If true, they
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will return the SQL query string and NOT actually execute it. (For
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Methods may throw db.DBException, or any of the pg exceptions as well.
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(In general, be prepared to catch exceptions!)
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"""Connects to the database and creates a DB object.
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Takes no parameters - gets all the DB info from the configuration."""
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self.db = pg.connect(dbname=conf.db_dbname, host=conf.db_host,
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port=conf.db_port, user=conf.db_user, passwd=conf.db_password)
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# GENERIC DB FUNCTIONS #
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def check_dict(dict, tablefields, disallowed=frozenset([]), must=False):
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"""Checks that a dict does not contain keys that are not fields
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of the specified table.
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dict: A mapping from string keys to values; the keys are checked to
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see that they correspond to login table fields.
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tablefields: Collection of strings for field names in the table.
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Only these fields will be allowed.
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disallowed: Optional collection of strings for field names that are
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must: If True, the dict MUST contain all fields in tablefields.
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If False, it may contain any subset of the fields.
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Returns True if the dict is valid, False otherwise.
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allowed = frozenset(tablefields) - frozenset(disallowed)
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dictkeys = frozenset(dict.keys())
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return allowed == dictkeys
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return allowed.issuperset(dictkeys)
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def insert(self, dict, tablename, tablefields, disallowed=frozenset([]),
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"""Inserts a new row in a table, using data from a supplied
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dictionary (which will be checked by check_dict).
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dict: Dictionary mapping column names to values. The values may be
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any of the following types:
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str, int, long, float, NoneType.
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tablename: String, name of the table to insert into. Will NOT be
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escaped - must be a valid identifier.
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tablefields, disallowed: see check_dict.
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dry: Returns the SQL query as a string, and does not execute it.
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Raises a DBException if the dictionary contains invalid fields.
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if not DB.check_dict(dict, tablefields, disallowed):
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raise DBException("Supplied dictionary contains invalid fields.")
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# Build two lists concurrently: field names and values, as SQL strings
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for k,v in dict.items():
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values.append(_escape(v))
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if len(fieldnames) == 0: return
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fieldnames = ', '.join(fieldnames)
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values = ', '.join(values)
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query = ("INSERT INTO %s (%s) VALUES (%s);"
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% (tablename, fieldnames, values))
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def update(self, primarydict, updatedict, tablename, tablefields,
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primary_keys, disallowed_update=frozenset([]), dry=False):
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"""Updates a row in a table, matching against primarydict to find the
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row, and using the data in updatedict (which will be checked by
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primarydict: Dict mapping column names to values. The keys should be
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the table's primary key. Only rows which match this dict's values
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updatedict: Dict mapping column names to values. The columns will be
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updated with the given values for the matched rows.
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tablename, tablefields, disallowed_update: See insert.
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primary_keys: Collection of strings which together form the primary
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key for this table. primarydict must contain all of these as keys,
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if (not (DB.check_dict(primarydict, primary_keys, must=True)
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and DB.check_dict(updatedict, tablefields, disallowed_update))):
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raise DBException("Supplied dictionary contains invalid or "
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# Make a list of SQL fragments of the form "field = 'new value'"
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# These fragments are ALREADY-ESCAPED
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for k,v in updatedict.items():
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setlist.append("%s = %s" % (k, _escape(v)))
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for k,v in primarydict.items():
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wherelist.append("%s = %s" % (k, _escape(v)))
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if len(setlist) == 0 or len(wherelist) == 0:
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# Join the fragments into a comma-separated string
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setstring = ', '.join(setlist)
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wherestring = ' AND '.join(wherelist)
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# Build the whole query as an UPDATE statement
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query = ("UPDATE %s SET %s WHERE %s;"
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% (tablename, setstring, wherestring))
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def delete(self, primarydict, tablename, primary_keys, dry=False):
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"""Deletes a row in the table, matching against primarydict to find
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primarydict, tablename, primary_keys: See update.
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if not DB.check_dict(primarydict, primary_keys, must=True):
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raise DBException("Supplied dictionary contains invalid or "
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for k,v in primarydict.items():
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wherelist.append("%s = %s" % (k, _escape(v)))
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if len(wherelist) == 0:
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wherestring = ' AND '.join(wherelist)
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query = ("DELETE FROM %s WHERE %s;" % (tablename, wherestring))
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def get_single(self, primarydict, tablename, getfields, primary_keys,
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error_notfound="No rows found", dry=False):
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"""Retrieves a single row from a table, returning it as a dictionary
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mapping field names to values. Matches against primarydict to find the
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primarydict, tablename, primary_keys: See update/delete.
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getfields: Collection of strings; the field names which will be
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returned as keys in the dictionary.
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error_notfound: Error message if 0 rows match.
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Raises a DBException if 0 rows match, with error_notfound as the msg.
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Raises an AssertError if >1 rows match (this should not happen if
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primary_keys is indeed the primary key).
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if not DB.check_dict(primarydict, primary_keys, must=True):
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raise DBException("Supplied dictionary contains invalid or "
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for k,v in primarydict.items():
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wherelist.append("%s = %s" % (k, _escape(v)))
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if len(getfields) == 0 or len(wherelist) == 0:
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# Join the fragments into a comma-separated string
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getstring = ', '.join(getfields)
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wherestring = ' AND '.join(wherelist)
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# Build the whole query as an SELECT statement
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query = ("SELECT %s FROM %s WHERE %s;"
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% (getstring, tablename, wherestring))
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result = self.db.query(query)
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# Expecting exactly one
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if result.ntuples() != 1:
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# It should not be possible for ntuples to be greater than 1
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assert (result.ntuples() < 1)
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raise DBException(error_notfound)
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# Return as a dictionary
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return result.dictresult()[0]
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def get_all(self, tablename, getfields, dry=False):
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"""Retrieves all rows from a table, returning it as a list of
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dictionaries mapping field names to values.
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tablename, getfields: See get_single.
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if len(getfields) == 0:
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getstring = ', '.join(getfields)
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query = ("SELECT %s FROM %s;" % (getstring, tablename))
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return self.db.query(query).dictresult()
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def start_transaction(self, dry=False):
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"""Starts a DB transaction.
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Will not commit any changes until self.commit() is called.
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query = "START TRANSACTION;"
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def commit(self, dry=False):
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"""Commits (ends) a DB transaction.
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Commits all changes since the call to start_transaction.
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def rollback(self, dry=False):
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"""Rolls back (ends) a DB transaction, undoing all changes since the
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call to start_transaction.
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# USER MANAGEMENT FUNCTIONS #
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login_primary = frozenset(["login"])
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login_fields_list = [
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"login", "passhash", "state", "unixid", "email", "nick", "fullname",
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"rolenm", "studentid", "acct_exp", "pass_exp", "last_login"
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login_fields = frozenset(login_fields_list)
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# Do not return passhash when reading from the DB
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login_getfields = login_fields - frozenset(["passhash"])
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def create_user(self, dry=False, **kwargs):
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"""Creates a user login entry in the database.
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All user fields are to be passed as args. The argument names
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are the field names of the "login" table of the DB schema.
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However, instead of supplying a "passhash", you must supply a
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"password" argument, which will be hashed internally.
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Also "state" must not given explicitly; it is implicitly set to
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Raises an exception if the user already exists, or the dict contains
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invalid keys or is missing required keys.
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if 'passhash' in kwargs:
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raise DBException("Supplied arguments include passhash (invalid).")
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# Make a copy of the dict. Change password to passhash (hashing it),
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# and set 'state' to "no_agreement".
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kwargs = copy.copy(kwargs)
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if 'password' in kwargs:
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kwargs['passhash'] = _passhash(kwargs['password'])
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del kwargs['password']
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kwargs['state'] = "no_agreement"
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return self.insert(kwargs, "login", self.login_fields, dry=dry)
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def update_user(self, login, dry=False, **kwargs):
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"""Updates fields of a particular user. login is the name of the user
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to update. The dict contains the fields which will be modified, and
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their new values. If any value is omitted from the dict, it does not
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get modified. login and studentid may not be modified.
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Passhash may be modified by supplying a "password" field, in
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cleartext, not a hashed password.
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Note that no checking is done. It is expected this function is called
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by a trusted source. In particular, it allows the password to be
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changed without knowing the old password. The caller should check
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that the user knows the existing password before calling this function
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if 'passhash' in kwargs:
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raise DBException("Supplied arguments include passhash (invalid).")
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if "password" in kwargs:
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kwargs = copy.copy(kwargs)
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kwargs['passhash'] = _passhash(kwargs['password'])
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del kwargs['password']
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return self.update({"login": login}, kwargs, "login",
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self.login_fields, self.login_primary, ["login", "studentid"],
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def get_user(self, login, dry=False):
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"""Given a login, returns a User object containing details looked up
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Raises a DBException if the login is not found in the DB.
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userdict = self.get_single({"login": login}, "login",
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self.login_getfields, self.login_primary,
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error_notfound="get_user: No user with that login name", dry=dry)
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return userdict # Query string
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# Package into a User object
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return user.User(**userdict)
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def get_users(self, dry=False):
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"""Returns a list of all users in the DB, as User objects.
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userdicts = self.get_all("login", self.login_getfields, dry=dry)
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return userdicts # Query string
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# Package into User objects
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return [user.User(**userdict) for userdict in userdicts]
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def user_authenticate(self, login, password, dry=False):
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"""Performs a password authentication on a user. Returns True if
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"passhash" is the correct passhash for the given login, False
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Also returns False if the login does not exist (so if you want to
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differentiate these cases, use get_user and catch an exception).
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query = ("SELECT login FROM login "
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"WHERE login = '%s' AND passhash = %s;"
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% (login, _escape(_passhash(password))))
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result = self.db.query(query)
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# If one row was returned, succeed.
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# Otherwise, fail to authenticate.
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return result.ntuples() == 1
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"""Close the DB connection. Do not call any other functions after
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this. (The behaviour of doing so is undefined).
added
removed
lib/common/db.py
