Lecture 5: Security, PhP
• Security and
Authorization
– Discretionary Access
Control
• Grant, Revoke,
Authorization Graph,
Views
– Mandatory Access
Control
– Internet-oriented
Security
– Statistical Database
Security
CS3/586 Some slides copied from Kim Howard,
with permission.
• Getting started in UNIX
• Overview of PHP and
HTML
• PHP Basics
• PHP and Databases
– Postgres and MySQL
– Database Abstractions
– Connecting via Java or Perl
• Security
• References
Slide 1
3/23/2016
Lecture 5
Learning Objectives
• LO5.1 Identify the active privileges after a sequence
of GRANT and REVOKE commands on tables and/or
views
• LO5.2 Derive information in a database despite
statistical security measures.
• Be able to write a web application using a back end
database
Slide 2
Security and Authorization, Chapter 21
• Objectives:
– Secrecy: Users should not be able to see things they are not
supposed to see.
•
E.g., A student can’t see other students’ grades.
– Integrity: Users should not be able to modify things they are
not supposed to modify.
•
E.g., Only instructors can assign grades.
– Availability: Users should be able to see and modify things
they are allowed to see and modify.
• OS, Network security issues also relevant
– Only database issues discussed here
Slide 3
Access Controls
• A security policy specifies who is authorized to do
what.
• A security mechanism allows us to enforce a chosen
security policy.
• Two main mechanisms at the DBMS level:
–
–
Discretionary access control
Mandatory access control
Slide 4
Discretionary Access Control
• Based on the concept of access rights or privileges
for objects (tables and views), and mechanisms for
giving users privileges (and revoking privileges).
• Creator of a table automatically gets all privileges on
it.
–
DMBS keeps track of who subsequently gains and loses
privileges, and ensures that only requests from users who
have the necessary privileges (at the time the request is
issued) are allowed.
Slide 5
GRANT Command*
GRANT privileges ON object TO auth [WITH GRANT OPTION]
• The following privileges can be specified:




SELECT: Can read all columns (including those added later via
ALTER TABLE command).
 SELECT(col-name(s)) means can read these columns.
INSERT : Can insert tuples.
 INSERT(col-name(s)) means can insert non-null values into
these columns.
DELETE: Can delete tuples.
REFERENCES (col-name): Can define foreign keys (in other
tables) that refer to this column.
Auth is a group of users.
• If a user has a privilege with the GRANT OPTION, can pass
privilege on to other users (with or without passing on the
GRANT OPTION).
• Only owner can execute CREATE, ALTER, and DROP.

Slide 6
REVOKE Command
REVOKE privileges ON object FROM auth [RESTRICT|CASCADE]
• Must be issued by a user who granted “privileges” on
“object” to “auth”.
• CASCADE:
– abandon anyone granted this privilege by auth, and so on
recursively.
– “abandon”: If an auth’s privilege is abandoned and this is
the last possible abandonment, then revoke auth’s privilege
– “and so on recursively”: Abandon anyone granted the
privilege by the auth just abandoned.
• RESTRICT: If CASCADE would cause anyone to be
abandoned, then cancel the command.
Slide 7
Examples of Grant, Revoke
• Suppose Len has created the author table, then these commands
are executed in this order
– Len: GRANT UPDATE, SELECT ON author TO Yingjin
– Len: GRANT UPDATE ON author TO Parisa WITH GRANT
OPTION
– Parisa: GRANT UPDATE ON author TO Yingjin
– Len: REVOKE UPDATE ON author FROM Parisa CASCADE
– Len: REVOKE SELECT ON author FROM Yingjin CASCADE
•
•
•
•
What privileges does Parisa have on author?
What privileges does Yingjin have on author?
Can Yingjin issue UPDATE author A SET A.age=25?
Can Yingjin issue UPDATE author A SET
A.age=A.age+1?
Slide 8
REVOKE more precisely
•
•
In some cases we need a more precise definition of
REVOKE.
Steps to be taken after “REVOKE P ON O FROM A”
– First consider the case CASCADE
1. Draw an authorization graph of current state (cf. next page)
2. Delete the arc corresponding to “GRANT P ON O TO A”
3. Also delete any arc not accessible from SYSTEM via grants of
the privilege P on O
4. If an auth has no incoming arcs granting P on O, then auth
loses the privilege P on O.
– RESTRICT is the same as before: If CASCADE would
cause any arc other than “GRANT ON P TO A” to be
deleted, then abort the command.
Slide 9
Authorization Graph
System
( * on Sailors,Yes)
1
Joe
(Select on Sailors,Yes)
(Revoke, Cascade)
6
Art
3
(Select on Sailors,Yes)
4
2
(Select on Sailors,Yes)
(Select on Sailors,Yes)
5
Cal
(Select on Sailors,Yes)
Bob
Slide 10
GRANT/REVOKE on Views
• The creator of a view only has a privilege on the view
if s/he has it on every component of the view.
– In particular, must have SELECT on all components to
create the view
– If the creator of a view loses the SELECT privilege on an
underlying table, the view is dropped!
• If the creator of a view loses a privilege held with the
grant option on an underlying table, (s)he loses the
privilege on the view as well; so do users who were
granted that privilege on the view!
Slide 11
View Example
• Len is the creator of author. Suppose these statements are
executed.
– Len: GRANT SELECT ON author TO Vijay WITH GRANT OPTION
– Len: GRANT SELECT ON author TO Pratibha WITH GRANT
OPTION
– Pratibha: GRANT SELECT ON author TO Vijay WITH GRANT
OPTION
– Vijay: CREATE VIEW ta AS SELECT * FROM AUTHOR A WHERE
A.age < 30
– Len: REVOKE SELECT ON author FROM Vijay CASCADE
– Len: REVOKE SELECT ON author FROM Pratibha RESTRICT
• What privileges does Vijay have on author, ta?
• What privileges does Pratibha have on author, ta?
Slide 12
Role-Based Authorization
• In SQL-92, privileges are actually assigned to
authorization ids, which can denote a single user or a
group of users.
• In SQL:1999 privileges are assigned to roles.
–
–
–
Roles can then be granted to users and to other roles.
Reflects how real organizations work.
Illustrates how standards often catch up with “de facto”
standards embodied in popular systems.
Slide 13
Security to the Level of a Field!
• Can create a view that only returns one field of one
tuple. (How?)
• Then grant access to that view accordingly.
• Allows for arbitrary granularity of control, but:
–
–
Clumsy to specify, though this can be hidden under a good
UI
Performance is unacceptable if we need to define fieldgranularity access frequently. (Too many view creations and
look-ups.)
Slide 14
Mandatory Access Control
• Based on system-wide policies that cannot be changed by
individual users.
–
–
–
Each DB object is assigned a security class.
Each subject (user or user program) is assigned a clearance for a
security class.
Rules based on security classes and clearances govern who can
read/write which objects.
• Most commercial systems do not support mandatory access
control. Versions of some DBMSs do support it; used for
specialized (e.g., military) applications.
Slide 15
Why Mandatory Control?
• Discretionary control has some flaws, e.g., the Trojan horse
problem:
–
–
–
Justin has access to secret information that Dick wants to know.
Dick creates a table called Secret and gives INSERT privileges to
Justin (who doesn’t know about this).
Dick modifes the code of a database application program used by
Justin to additionally write some secret data to table Secret.
•
–
This requires hacking the OS security system a bit.
Now, Dick can see the secret data.
• The modification of the code is beyond the DBMSs control, but it
can try and prevent the use of the database as a channel for
secret information.
Slide 16
Bell-LaPadula Model
• Objects (e.g., tables, views, tuples)
• Subjects (e.g., users, user programs)
• Security classes:
–
Top secret (TS), secret (S), confidential (C), unclassified (U):
TS > S> C > U
• Each object and subject is assigned a class.
–
–
Subject S can read object O only if class(S) >= class(O)
(Simple Security Property)
Subject S can write object O only if class(S) <= class(O) (*Property)
Slide 17
Intuition
• Idea is to ensure that information can never flow from
a higher to a lower security level.
• E.g., If Dick is cleared for security class C, Justin for
class S, and the secret information has class S:
–
–
–
Dick’s table, Secret, has Dick’s clearance, C.
Justin’s application has his clearance, S.
So, the database application cannot write into table Secret.
• The mandatory access control rules are applied in
addition to any discretionary controls that are in
effect.
Slide 18
Multilevel Relations
bid
101
102
bname
Salsa
Pinto
color
Red
Brown
class
S
C
• Users with S and TS clearance will see both rows; a user
with C will only see the 2nd row; a user with U will see no
rows.
• If user with C tries to insert <101,Pasta,Blue,C>:
–
–
–
Allowing insertion violates key constraint
Disallowing insertion tells user that there is another object with
key 101 that has a class > C!
Problem resolved by treating class field as part of key.
Slide 19
Polyinstantiation
• Consider previous table with <101,Pasta,Blue,C>
inserted.
• What is the color of boat with bid=101?
– Only the highest visible security level exists.
– Both exist
– The proper policy is chosen according to the semantics of
the application
• Notice that the answer to the question depends on
your clearances. This is called polyinstantiation.
Slide 20
Internet-Oriented Security
• Key Issues: User authentication and trust.
– When DB must be accessed from a secure location, passwordbased schemes are usually adequate.
• For access over an external network, trust is hard to
achieve.
– If someone with Sam’s credit card wants to buy from you, how
can you be sure it is not someone who stole his card?
– How can Sam be sure that the screen for entering his credit
card information is indeed yours, and not some rogue site
spoofing you (to steal such information)? How can he be sure
that sensitive information is not “sniffed” while it is being sent
over the network to you?
• Encryption is a technique used to address these issues.
Slide 21
Encryption
• “Masks” data for secure transmission or storage
– Encrypt(data, encryption key) = encrypted data
– Decrypt(encrypted data, decryption key) = original data
– Without decryption key, the encrypted data is meaningless
gibberish
• Symmetric Encryption:
– Encryption key = decryption key; all authorized users know
decryption key (a weakness).
– DES, used since 1977, has 56-bit key; AES has 128-bit
(optionally, 192-bit or 256-bit) key
• Public-Key Encryption: Each user has two keys:
– User’s public encryption key: Known to all
– Decryption key: Known only to this user
– Used in RSA scheme (Turing Award!)
Slide 22
Certifying Servers
• If Amazon distributes their public key, Sam’s browser will encrypt his
credit card information using it.
– So, only Amazon can decipher the credit card information, since no one else has
Amazon’s private key.
• But how can Sam (or his browser) know that the public key for Amazon
is genuine?
– Amazon contracts with, say, Verisign, to issue a certificate <Verisign, Amazon,
amazon.com, public-key>
– This certificate is stored in encrypted form, encrypted with Verisign’s private key,
known only to Verisign.
– Verisign’s public key is known to all browsers, which can therefore decrypt the
certificate and obtain Amazon’s public key, and be confident that it is genuine.
– Your browser then generates a temporary session key, encodes it using Amazon’s
public key, and sends it to Amazon.
– All subsequent msgs between the browser and Amazon are encoded using
symmetric encryption (e.g., DES), which is more efficient than public-key encryption.
•
This solves the problem of you trusting Amazon, but not the problem of Amazon
trusting you.
Slide 23
Statistical DB Security
• Statistical DB: Contains information about individuals,
but allows only aggregate queries (e.g., average age,
rather than Joe’s age).
• New problem: It may be possible to infer some secret
information!
–
E.g., If I know Joe is the oldest sailor, I can ask “How many
sailors are older than X?” for different values of X until I get the
answer 1; this allows me to infer Joe’s age.
• Idea: Insist that each query must involve at least N
rows, for some N. Will this work?
Slide 24
Challenge Question
• You can ask queries which
aggregate data (no GROUP
BY) from at least 6 tuples.
Find the age of Len with as
few queries as possible.
Your answer should work for
any instance of the table with
more than 6 entries.
Name
Age
Len
61
Dave
45
Xavier
25
Kyu
20
Olgay
19
Vachara
22
Tabor
24
Slide 25
Creating your UNIX Workspace
• Login to your CS UNIX account
– mkdir ~/public_html
– chmod 755 public_html
• Place all web files in public_html
• All files must be world readable
– chmod 644 index.html
• If you enter this address to a browser
– http://www.cs.pdx.edu/~username
• The browswer will display a default index file if one
exists
– index.html, index.php, index.cgi
Slide 26
What is PHP?
• Recursive acronym for “PHP: Hypertext
Preprocessor”
• Widely used Open Source general-purpose scripting
language
– Scripting language: programing language that controls
software applications.
• Specially suited for Web development
• Can be embedded into HTML
• There may well be better scripting languages, but I
think PHP is the easiest to learn.
Slide 27
Some Advantages of PHP
• Runs on all major OS’s: MS Windows, Solaris, major
UNIX and Linux variants, Mac OS’s
• Runs on all major web servers: Apache, MS IIS,
iPlanet, …
• Has support for all major DBMSs: My SQL, Postgres,
Oracle, SQL Server, DB2, …
• Simple to learn basics, especially for those knowing
other languages like C/C++
• Lots of advanced features for professional
programmers
• Also available for command line scripting and gui
applications (PHP-GTK)
Slide 28
HTML
• HTML - Hyper Text Markup Language
• Way to explain document structure (not presentation!)
– Structure is title, paragraph, section
– Use CSS for presentation, e.g., font size, bold, bullets, margins
•
•
•
•
Tries to be device independent
Outside the scope of this lecture
HTML Tutorials: http://w3.org/MarkUp/#tutorials
A Caveman's Introduction to HTML and Related Tools:
http://www.cat.pdx.edu/~johnj/talks/show.php/introHTML
Slide 29
HTML Requests
• Client sends HTTP request from browser to web
server
• Server locates pages and transmit back to client
• Browser renders webpage from html
Slide 30
PHP Requests
• PHP executed by server and HTML sent back to server
Slide 31
PHP is a Server-Side Language
• PHP code is surrounded by start and end tags
• Preprocessing jumps in and out of PHP “mode”
– Replaces ALL PHP with HTML
• Finally, HTML is sent back to browser
Slide 32
Example of Server Side Processing
• If your HTML/PHP file contains:
<html>
<?php echo “Hello World”?>
</html>
• Then the PHP processor sends this HTML text back
to your browser (see it with “view source”):
<html>
Hello World
</html>
• Try it, and remember
– The HTML/PHP file must end in .php, e.g., test.php
• It is just a text file, edit it with pico, vi, emacs, etc.
– The file must reside in public_html,e.g., public_html/test.php
– The file must have world-readable permission
– Address it from any browser with
http://www.cs.pdx.edu/~username/test.php
Slide 33
My First PHP Page
<html>
<?php phpinfo(); ?>
</html>
PHP Version 4.4.0
System
SunOS scalpel.cat.pdx.edu 5.9 Generic_117171-07 sun4u
Build Date
Aug 22 2005 08:43:09
Configure Command
'…omitted…
Server API
Apache
Virtual Directory Support
disabled
Configuration File (php.ini) Path
/pkgs/webservers/apache-1.3.33/etc
…truncated…
Slide 34
PHP Language Basics
• Tutorial: http://us2.php.net/tut.php
• Language Reference:
http://us2.php.net/manual/en/langref.php
Slide 35
Language Basics
• Type decided at runtime by PHP depending on the
context in which that variable is used
• null, boolean, integer, float, string, array, object
<?php
$foo = 1; // integer
$bar = "Testing"; // string
$xyz = 3.14; // float
$foo = $foo + 1; // still an integer
?>
Slide 36
Basic Data Types
• Numbers (integers and real), Strings
<?php
$a = 1234;
$b = 0777;
$c = 0xff;
$d = 1.25;
echo "$a $b $c $d<br />\n";
?>
• Output: 1234 511 255 1.25
<?php
$name = 'Rasmus $last'; // Single-quoted
$str = "Hi $name\n";
// Double-quoted
echo $str;
?>
• Output: Hi Rasmus $last
Slide 37
More Basic Data Types, Dynamic Typing
• Booleans
<?php
$greeting = true;
while ($greeting) {
echo "Hi Carl";
$greeting = false;
}
?>
• Output: Hi Carl
• Dynamic Typing
– Don't have to declare types
– Automatic conversion done
<?php
echo 5 + "1.5" + "10e2";
?>
• Output: 1006.5
Slide 38
Arrays
• Useful for many things besides an array: list (vector),
hashtable, dictionary, collection, stack, queue, and more
<?php
$arr[1] = 1;
$arr["stuff"] = "more stuff"; // always use quotes
//around string literal array indexes
$arr2[1][2] = 3;
?>
• Useful array functions built-in
• array_push, array_pop, array_rand,
array_shift, array_search, sort, ...
Slide 39
Predefined Variables*
• $_SERVER : array containing information such as headers,
paths, and script locations
• $_GET : associative array of variables passed to the current
script via the HTTP GET method
• $_POST : associative array of variables passed to the current
script via the HTTP POST method
<?php
echo "script: $_SERVER[SCRIPT_NAME]
<br/>\n";
echo "user-agent: $_SERVER[HTTP_USER_AGENT]
<br/>\n";
?>
• Output
script: /~len/test.php
user-agent: Mozilla/4.0 (compatible; MSIE 6.0;
Windows NT 5.1; SV1; InfoPath.1; .NET CLR
2.0.50727; .NET CLR 1.1.4322)
Slide 40
C-like syntax
<?php
$loop = 0;
$i = 0;
for ($loop = -3; $loop < 3; $loop++) {
if ($i < 0) {
echo "-";
} elseif ($i > 0) {
echo "+";
}
echo "$loop<br/>\n";
}
while(--$loop) {
switch($loop % 2) {
case 0:
echo "Even<br/>\n";
break;
case 1:
echo "Odd<br/>\n";
break;
}
}
do {
echo "$loop<br/>";
} while (++$loop < 5);
?>
•Output:
-3
-2
-1
0
1
2
Even
Odd
0
1
2
3
4
Slide 41
Syntax and Switching Modes
<? if(strstr($_SERVER['HTTP_USER_AGENT'],"MSIE"))
{ ?>
<b>You are using Internet Explorer</b>
<? } else
{ ?>
<b>You are not using Internet Explorer</b>
<? } ?>
Slide 42
A useful print function: print_r
<?php
$arr = array ('a' => 'apple',
'b' => 'banana',
'c' =>
array ('x', 'y', 'z'));
echo "<pre>" . print_r($arr) . "</pre>";
?>
• Output
Array
(
[a] => apple
[b] => banana
[c] => Array
(
[0] => x
[1] => y
[2] => z
)
)
Slide 43
Object Oriented Programming
• Classes
<?php
class Box {
var $contents;
function Box($contents) {
$this->contents = $contents;
}
}
function get_inside() {
return $this->contents;
}
$mybox = new Box("Stuff");
echo $mybox->get_inside();
?>
• Output: Stuff
Slide 44
More OO Programming
<?php
class Present extends Box {
var $wrap_color;
function Present($contents, $wrap_color) {
$this->contents = $contents;
$this->wrap_color = $wrap_color;
}
}
function get_color() {
return $this->wrap_color;
}
$mybox = new Present("iPod Shuffle", "lime
green");
echo $mybox->get_inside() .
" : " . $mybox->get_color();
?>
• Output: iPod Shuffle : lime green
Slide 45
HTML Forms
<form
action="<?php echo $PHP_SELF ?>"
method="POST">
Your name: <input type="text"
name="name"><br>
Your age: <input type="text" name="age"><br>
<input type="submit">
</form>
• Output (what appears on the browser):
Your name:
Your age:
Submit
Slide 46
How to Manage Forms
Hi <?echo $_POST['name'] ?>.
You are <?echo $_POST['age'] ?> years
old.
Slide 47
PHP and Databases: Overview
• Open a connection to the database - PHP returns a
"connection resource"
• Run a query - PHP returns a query "result resource"
• Do something with the result - display output to user
or do some other actions
• Close the connection resource - tell database and
PHP we don't need it any more
Slide 48
Connecting to a Database
• PHP Postgresql Functions:
http://www.php.net/manual/en/ref.pgsql.php
• pg_connect() returns a connection resource that is needed by
other PostgreSQL functions.
<?php
$username = “cs386";
$password = "introdb";
$databasename = “cs386";
$hostname = "db.cecs.pdx.edu";
$connection = pg_connect("host=$hostname
dbname=$databasename user=$username
password=$password")
or die ("Could not connect");
// do stuff
pg_close($connection);
?>
Slide 49
Connection Errors
<?php
$username = “cs386";
$password = "foobar"; // wrong password
$databasename = “cs386";
$hostname = "db.cecs.pdx.edu";
$connection = pg_connect("host=$hostname
dbname=$databasename user=$username
password=$password")
or die ("Could not connect");
// do stuff
pg_close($connection);?>
• Error Message
Warning: pg_connect(): Unable to connect to PostgreSQL
server:
FATAL: Password authentication failed for user “cs386"
in ./display.php(433) : eval()'d code on line 7
Could not connect
Slide 50
Executing a Query on a Connection: pg_query
<?php
// assuming we already connected with
code from previous slide...
$query = "
SELECT DISTINCT N.candname, N.party
FROM candcl N;
";
$result = pg_query($connection, $query)
or
die("Query error: " .
pg_last_error());
?>
Slide 51
Query Result Errors
• If we had said
SELECT DISTINCT foobar
• We would have seen the error message
Warning: pg_query(): Query failed:
ERROR: column "foobar" does not exist
in ./display.php(433) :
eval()'d code on line 20
Query error: ERROR: column "foobar"
does not exist
• Note: Postgresql automatically folds all identifiers
(e.g. table/column names) to lower case values. To
get it to recognize upper case values, you must wrap
the identifier in quotes
Slide 52
Retrieving tuples: pg_fetch_row
• pg_fetch_row returns each row as an enumerated
array
<?php
echo pg_num_rows($result) . " rows returned\n";
$row = 0;
while ($row = pg_fetch_row($result)) {
echo "Name: $row[0]<br>\n";
echo “Party: $row[1]<br>\n";
}
?>
• Output
4 rows returned
Name: MCCAIN, JOHN S.
Party: REP
…
Slide 53
Fetching rows as objects
<?php
$num = pg_numrows($result);
echo '<table border="1">';
for($count=0; $count < $num &&
$data=pg_fetch_object($result,$count); $count++){
printf("<tr>\n");
printf("
<td>%s</td>\n",$data->candname);
printf("
<td>%s</td>\n",$data->party);
printf("</tr>\n");
}
echo "</table>\n";
?>
Output:
MCAIN JOHN S.
OBAMA, BARACK
SMITH, GORDON
MERKLEY, JEFFREY
REP
DEM
REP
DEM
Slide 54
Fetching rows as arrays
• Calling pg_fetch_array() will return an enumerated
and an associative array
<?php
$array = pg_fetch_array($result);
echo "Name: $array[“candname"]<br/>\n";
echo “Party: $array[“party"]<br/>\n";
echo "Name: $array[0]<br/>\n";
echo “Party: $array[1]<br/>\n";
?>
• Output:
Name: MCCAIN, JOHN S.
Party: REP
Name: OBAMA, BARACK
Party: DEM
Slide 55
Example for MySQL
<?php
$username = "akimbo_ro";
$password = "readme";
$databasename = "akimbo";
$hostname = "db.cecs.pdx.edu";
$connection = mysql_connect($hostname, $username,
$password)
or die ("Could not connect");
mysql_select_db($databasename) or die("Database
select error: " . mysql_error());
$query = "
SELECT DISTINCT N.candname, N.party
FROM candcl
);
";
$result = mysql_query($query, $connection) or
die("Query error: " . mysql_error());
echo mysql_num_rows($result) . " rows returned\n";
while ($row = mysql_fetch_row($result)) {
echo "Name: $row[0]<br/>\n";
echo “Party: $row[1]<br/>\n";
}
mysql_close($connection);
?>
Slide 56
DB Application Development
• Planning!
–
–
–
–
–
Target audience and platform: Web? Native App?
Server OS, Webserver, Language
Database differences
Specifications
Schema!
• Split up the work
– Presentation versus application code
– Designers versus programmers
• Smarty: http://smarty.php.net
– Template/Presentation Framework
Slide 57
Database Abstractions
• Database-independent software interfaces
• Allows developers to deal with different DBMSs
without altering code
• Why is it needed? Implementations of SQL differ in
many ways, e.g.
– Data formats, such as dates
– Null values can be represented differently
– New features, such as TOP N vs. LIMIT
• Many of these abstractions are based on ODBC.
• Comparison of PHP abstractions:
http://phplens.com/lens/adodb/
Slide 58
Connecting to PostgreSQL with Java
•
•
PostgreSQL JDBC Driver: http://jdbc.postgresql.org/
On Unix add /pkgs/pgsql/pgsql-7.4.6/share/java/postgresql.jar to your
$CLASSPATH or use jar file from the site
/* sample that connects to cs386 and gets two columns from
the candcl table
*/
import java.sql.*;
public class connectPostgreSQL {
public static void main(java.lang.String[] args) {
try {
// Here we load the JDBC driver.
Class.forName("org.postgresql.Driver");
} catch (Exception e) {
System.out.println(“Driver error:“ + e.getMessage());
return;
}
try {
Connection pSQL =
DriverManager.getConnection(
"jdbc:postgresql://db.cecs.pdx.edu/cs386",
“cs386","introdb");
Slide 59
/* This is where we create a Statement object
* and execute a SQL query using it.
*/
Statement query = pSQL.createStatement();
ResultSet cands =
query.executeQuery(
"SELECT * FROM candcl;");
/* Here we'll loop through the ResultSet,
* printing out results by column names,
* candname and party
*/
Connecting to
PostgreSQL with
Java, ctd.
System.out.println(“NAME%tPARTY");
while (cands.next()) {
System.out.println(
cands.getString(“candname")
+ “\t%"
+ cands.getString(“party"));
}
}
}
// Close all of our JDBC resources.
cands.close();
query.close();
pSQL.close();
} catch (SQLException se) {
// Give feedback for any SQL errors.
System.out.println("SQL Exception: "
+ se.getMessage());
se.printStackTrace(System.out);
}
Slide 60
#!/usr/bin/perl
use DBI;
$username = “cs386";
$password = "introdb";
$databasename = “cs386";
$hostname = "db.cecs.pdx.edu";
$conn_type = "postgres";
Connecting to PostreSQL
with Perl
$dbh = DBI->connect(dbi:Pg:dbname=$databasename;host=$hostname",
"$username","$password");
if ($dbh) {
print "Content-type:text/html\n\n";
$query = "SELECT * from subject";
$sth = $dbh->prepare($query);
if (!defined($sth)) {
print "Cannot prepare $DBI::errstr\n";
}
if (!$sth->execute) {
print "Cannot execute $DBI::errstr\n";
}
print "<table>\n";
while (@vetor = $sth->fetchrow) {
print "<TR>\n";
foreach $field (@vetor) {
print "<TD VALIGN=TOP>$field</TD>\n";
}
print "</TR>\n";
}
print "</table>\n";
$sth->finish;
$dbh->disconnect();
} else {
print "Cannot connect to Postgres server: $DBI::errstr\n";
}
Slide 61
Web Security: SQL Injection
• Validate all incoming data, don't trust the web
• Be careful when executing system commands, database
queries from user supplied data
• SQL injection
<?php
$query = "SELECT * FROM sometable
WHERE field = '" . $_GET['email'] . "';";
?>
–
–
–
–
What happens if $_GET['email'] is "%" ?
SELECT * FROM sometable WHERE field = '%';
What happens if $_GET['email'] is "foo@bar'; DROP 'sometable" ?
SELECT * FROM sometable WHERE field = 'foo@bar'; DROP
'sometable';
Slide 62
Avoiding SQL Injection
• Connect to database as user with limited powers,
such as read only access
• Check that input has the correct datataype: use input
validating functions or regular expressions
• Escape string input: mysql_real_escape_string() or
addslashes()
• Don't print out information about the schema
• PHP on SQL Injection (can be applied to other
languages):
http://www.php.net/manual/en/security.database.sql-injection.php
Slide 63
Reading a File
<PRE><?php readfile("/etc/motd")?></PRE>
• Output:
Sun Microsystems Inc. SunOS 5.9 Generic May 2002
=======
Unauthorized access to this system is prohibited. Systems to
identify unauthorized users may also monitor authorized users.
=======
*** Read "msgs" for system bulletins.
Slide 64
C-Like File Functions
• Reading from a file
<?php
$file = fopen("sample.txt", "r");
while (!feof($file)) {
echo fgets($file), "<BR>";
}
?>
• Reading from a URL
<?php $file = fopen("http://www.php.net/file.txt", "r"); ?>
• Writing to a file
<?php
$file = fopen("agent.log", "a");
fputs($file, $HTTP_USER_AGENT."\n");
?>
Slide 65
Web References
•
•
•
•
•
•
•
•
PHP Website, Manual: http://www.php.net
PHP Beginning Tutorial: http://www.php.net/tut.php
Zend Website: http://www.zend.com/developers.php
Zend Beginning PHP Articles:
http://www.zend.com/php/beginners/index.php
PHP Presentations: http://talks.php.net/
More PHP Related Links http://www.php.net/links.php
Practical PostgreSQL Book:
http://www.commandprompt.com/ppbook/book1
PostgreSQL JDBC Driver: http://jdbc.postgresql.org/
Slide 66
Book References
•
•
•
•
•
•
PHP and PostgreSQL 8
Programming PHP
Advanced PHP Programming
Web Database Applications with PHP & MySQL
Learning PHP 5
Practical Postgresql (also available online, see
previous page)
Slide 67
Misc. References and Tools
• Connecting to Databases with Perl: http://dbi.perl.org/
• PHP Auto Documenter: http://www.phpdoc.org/
• Zend IDE (Windows, Linux, Unix, Mac OSX) and
Debugger: http://www.zend.com/store/products/zendstudio.php
• DBDesigner4 (Windows and Linux):
http://www.fabforce.net/dbdesigner4/
• HTML and MarkUp Validator http://validator.w3.org/
• MySQL: http://dev.mysql.com/
• PostgreSQL http://www.postgresql.org/
Slide 68