Friday, September 23, 2011

Internet Explorer and its disrespect to W3C standards

    W3C has set since much time ago, several set of standards to rule rendering of webpages and to unify criteria among navigators.

    This time, I am not refering to how IE treats margins in a completelly different way than all the others, but I am refering at how internet explorer does not seem to look at the provided charset of an X/HTML page.

    But this is not the first time that Microsoft goes on his own way contrary to the world, let me mention a bit of history about encodings.

Some time ago, where there wasn't any formal definition for anything that went outside ASCII encoding, several models were proposed from International Organization for Standardization (ISO): For example, the ISO-8859-XX for european languages, and not forget the most used UTF-8 encoding.

Well, while all, and when I say all is all, the Operating Systems in the world adopted any (if not all) of those standard models, Microsoft came along with a new, different and incompatible charset: windows-xxxx character sets (for example windows-1252.

Not happy with being the only one who broke the international standarization rules, some time after came Internet Explorer, parsing and rendering X/HTML elements as it wants, sometimes it is correct, and sometimes it is not.

    But let's get back to main topic: What is wrong (this time) with Internet Explorer? One of the things I will comment here is a problematic one: it ignores provided character set and uses windows' default one! Despite this error seems not reproducible always.

    This (and all IE problems) are not easy to deal with, because one can think: then let people know and use safer and better navigator, but this won't be an accepted solution, so what are the problems IE cause?

  • It forces developers (despite following strict standards) to put an extra effort in developing, which translates in more money to spend on project.
  • Since it is the default on Windows, an unexperienced user (a potencial client) may use it and unknow other navigators
  • Much more problems that I will not write about now.
    Conclusion: Imagine a battery vendor (that also is bound to standards like size, voltage, etc...) and you need some batteries for your remote control of your TV.
Now you have to buy some new batteries because the old ones ran out, and discover that there is only one vendor who is not following those standards and the batteries you bought are a bit bigger and with more voltage than what you need. This is the question I want to ask to everybody:
Will you change your remote control to a new one (provided also by that vendor), or will you discard those batteries, keep your remote control and ask that vendor to follow standard to produce items as it should?

    Now, think about Internet Explorer and keep in mind previous example: Why in this case, we need to change our developed code (remote control) in order to work with Internet Explorer(batteries) instead of doing what makes sense: Just discard Internet Explorer and force Microsoft to program a quality navigator?

Think about it...


Wednesday, August 17, 2011

Farewell KMail2

    I've been testing the new akonadi based KMail2 and I got dissapointed. My last version tested was from KDE 4.7.0 and now, I decided to change to another software for productivity reasons.

    The main reason for this change is that KMail fails to mark messages as read and it fails to differentiate read messages from unread (for example, like previous KMail did, having different colours for read and unread ones).

    I've already posted a bug against it (KDE bug #276893), but I didn't receive any feedback from developers as of today.

    So I finally decided posting an image wich will show this problem: KMail does not mark ANY message as read, so it is hard to keep your messages up to date, since I have to remember which messages I have read and which I have not.

    My last hope is that they take seriously this severe blockstopper bug as soon as possible... In the mean while, I will be using another software for managing my emails, so.... After several years... farewell KMail2

Monday, August 08, 2011

About SQL injection

    Despite this kind of attack is very old, it is still the primary source of database and website attacks so it really deserves a little speak here and everywhere. In an ideal world, maybe this will not worth a cent, but unfortunatelly we are not in an ideal world.

    Many people say that this is due to malicious people and/or hackers fault, but the guilt comes from both sides: bad programmers and bad people.

    I'll explain this kind of attack with an example (in PHP, but it affects SQL independently of language used).

    Suppose we have a login validation this way:
$sentence="SELECT COUNT(*) FROM Users WHERE username='".$_GET['user']."' AND pass='".$_GET['password']."'";
    (And later in your code check if result>0 in order to check if login was successfull)

    The problem here comes from not checking user inputs, in a good case, sentence will not be a special one, for example: (user input in bold) 

SELECT COUNT(*) FROM Users WHERE username='bob' AND pass='foo';

    But there is a problem, if input is not sanitized, this SQL sentence could be transformed and executed into many SQL sentences allowing a user, for example this can happen because of not sanitizing _GET array:
(1) SELECT COUNT(*) FROM Users WHERE username='bob' OR 1=1;--' AND pass='foo';
(2) SELECT COUNT(*) FROM Users WHERE username='bob'; DROP TABLE Users;--' AND PASS='foo';
(3) SELECT COUNT(*) FROM Users WHERE username='bob'; SELECT creditcardnumber FROM Users;--' AND pass='foo';

    Those two sentences with user input marked as bold are self explanatory, but you can see how 1 sentence can be modified to allow you to login with an account which is not yours(1), to destroy data(2) or to gather other kind of sensitive information(3).

    Maybe you are thinking that if this problem is old, it does not worth to speak of it: ERROR!
From time to time, a huge company(Sony) or government agency (CIA) are attacked using this method. This leads me to think: How poor their hired programmers work, and how little do companies value our personal and sensitive data!

    So as this problem has been proved to be relevant and important, let's investigate some solutions.
  • Prepared Statements and parametrized queries:
    This seems the best solution: A SQL sentence is no longer crafted by join two or more strings, and SQL keywords are splitted from data. (and also, real sentence is not sent over the network every time it is executed). An example of prepared statement could be: (in postgres)
SELECT COUNT(*) FROM Users WHERE username=$1 AND pass=$2

    This time, postgres already know what type are $1 and $2 and they are parsed accordingly, but the more important fact, $1 and $2 parameters will be treated as a complete string, eliminating the posibility of crafting another sentence from this one. So in this case a malicious input will be treated like:
SELECT COUNT(*) FROM Users WHERE username='bob''; DROP TABLE Users;--' AND pass='foo';

    In this case, as all username will be treated as a whole parameter, this sentence will likelly return 0 rows as a result instead of harming data.
Try to AVOID SQL crafted strings in your source code and use prepared statements!

  • Sanitize inputs: While this approach is good enough, I recomment to apply in conjunction with previous one. It consists on checking and escaping any non standard character and convert them to avoid SQL sentence breakage. (In case you can't avoid crafting sentence)
$input=pg_escape_string($_GET['username']); and apply it to SQL crafted string, this way, any ' or " character that could break your SQL sentence will be quoted disallowing it to harm your sentence.

    To sum up: Even governments and big companies do not care enough their databases to spend a little time to check source code to avoid this kind of problems.

Tuesday, July 26, 2011

Dropping ReiserFS (v3)

    As the time goes by, Reiser FS v3 is becoming outdated, but this is not the reason I will drop it in the near future in favour of ext4.

    Last night, I was renaming a couple of files (14GiB ones), and my laptop's battery went out.
When I rebooted and after checking disk consistency with reiserfsck, one of those files became empty! (I must explain that that file was not in cache nor it had been written recently, it has been there since I booted)

    This is just unaceptable for a journaled and "modern" file system, and since Hans Reiser is in prison and namesys seems to have discontinued Reiser FS v4 support, I will DROP ReiserFS forever.

Rest in peace ReiserFS

Wednesday, May 04, 2011

PostgreSQL Inhertance and Constraints problem solved!

Warning: Using stored procedures and triggers in PostgreSQL is addictive!

    I've been playing around with stored procedures using PLpgSQL language, just to try performance improvements and they are just addictive!

    For example, PostgreSQL has the ability to inherit all data from one or more tables to other table, but unfortunately, any constraint will be inherited as of 9.0.4, and thus, you can not make a FOREIGN KEY constraint agains parent table.

    Fortunately, you can workaround this issue with a little performance impact by using stored procedures, triggers and a separate table for that constraint.

    For example, imagine this scenario:
CREATE TABLE account (
    id SERIAL,
    username VARCHAR(50) UNIQUE NOT NULL,
    PRIMARY KEY (id)

CREATE TABLE employee (
    salary MONEY(6,2) NOT NULL
) INHERITS (account);

CREATE TABLE problematic (
    id SERIAL,
    account_id INTEGER NOT NULL,
    PRIMARY KEY (id),
    FOREIGN KEY (account_id) REFERENCES account(id)

    Suppose we have some data:

INSERT INTO employee(username,salary) VALUES ('foo','1280.90'),('bar','3460.75');

    We will have account filled with those usernames as well as employee filed with the rest of values but the problem will come with a:

INSERT INTO problematic(account_id) VALUES(1);

    Since inheritance does not cover constraints, this last INSERT will fail because it will not find corresponding id on account table, despite it is really there.

    But there is NOT all lost! Fortunately we can place triggers on employee to fill and maintain other intermediary table values for simulating that constraint.

    Solution will be to create that table:

CREATE TABLE account_constraint (
    PRIMARY KEY (id)

    And to change employee's FOREIGN KEY constraint this way:

FOREIGN KEY (account_id) REFERENCES account_constraint(id);

    And now... how to keep account_constraint table up to date always and in a safe way? The solution rather than code it by yourself in all clients is to use a procedure and place triggers which will fire BEFORE INSERT, UPDATE and DELETE.

    This could be an example of this procedure:

CREATE OR REPLACE FUNCTION account_id_constraint_handler() RETURNS trigger
AS $$
       IF (TG_OP = 'INSERT') THEN
          INSERT INTO account_constraint(id) VALUES (;
          IF (TG_OP = 'UPDATE') THEN
             UPDATE account_constraint SET WHERE;
             DELETE FROM account_constraint WHERE;
             RETURN OLD;
          END IF;
       END IF;
Language 'plpgsql';

    And the last thing to do is to set triggers this way:

CREATE TRIGGER insert_accountID
EXECUTE PROCEDURE account_id_constraint_handler();
CREATE TRIGGER update_accountID
EXECUTE PROCEDURE account_id_constraint_handler();
CREATE TRIGGER delete_accountID
EXECUTE PROCEDURE account_id_constraint_handler();

    You can now alter any data safely maintaining FOREIGN KEY CONSTRAINT!
And the best: database will do all work needed with only a little impact, since PostgreSQL stores procedures in a precompiled state to improve performance a bit.

    Remember that, once you start using stores procedures (or functions) you will not stop as stated in the warning above!

Wednesday, April 20, 2011

Microsoft and its unfair selling techniques

    Microsoft, did it again: left its users alone with new versions of its programs.

    I am referring for example to Internet Explorer 9, new Version of Windows Live Messenger, etc....
Rather than make it compatible with its own older O.S., they just require you to upgrade (and BUY) another version of their O.S.

    This is TOTALLY UNFAIR! Specially taking into account the fact that ANY of its O.S. is FREE, then, the result is that you pay for an O.S. and be left alone in some time if you don't pay again (and thus, forced to pay another O.S.).

    What demonstrate this kind of behavior from Microsoft?
  • They does not value its own customers: you pay, and whenever they say they won't support you, they won't and you can't complain (it is in their TOS).
  • If for any cause, a security risk is discovered or an important upgrade in other program is made, if they don't release it for their O.S., you can't simply have it...
    What means this to me?
  • It makes me happy to be a Linux ONLY user since 7 years now, without using any software from Microsoft.
  • I don't get fooled by a company which requires me to pay for an limited product, full of security holes (in its long history), and full of bugs, and, of course, trapped to pay to them every X years forcedly!
Conclusion: Will you get fooled by Microsoft?

Dropping MySQL, and adopting PostgreSQL

    Finally I had the time to dig a bit this issue, and finally, decided to drop all MySQL support in favor of PostgreSQL.

    Despite PostgreSQL is not as known nor as used as MySQL, it has MANY advantages:
  • Referential Integrity: MySQL's default engine (MyIsam) does NOT support any kind of referential integrity, which could lead to corruption and inconsistencies in DB.
  • On the other hand, the other MySQL's engine which does support referential integrity (InnoDB) is very much slow. In my case, only to create a table with a referenced FOREIGN KEY to another table takes ~1 second! And cascade deleting/checking/updating also takes much more time then postgre takes.
  • Extended Data Types: With PostgreSQL you don't have only a few data types like you have in MySQL. With PostgreSQL you have, cidr (for IP addresses), money, and other data types, as well as user defined data types.
  • Prepared Statements: As stated in my previous post, MySQL had support for prepare statements, but you couldn't not give a name to them (unless you use my class, or code it by yourself), but with PostgreSQL, you can even give natively a string name! (even inside client).
  • Performance: In my case, with my databases, and googling a bit, you can see that PostgreSQL has much better overall performance than MySQL.
    To sum up, I though that since Oracle bought MySQL, it would be improved a lot, but it seems only a commercial action rather than a really interest in MySQL from Oracle.

Thursday, March 03, 2011

MySQL's Prepared Statements made really easy with PHP

    I've been programming a bit with php for first time, realizing that it is true what my friends told me: it is really close to C/C++.

    I managed to have an abstract class to handle and execute SQL's prepared statements, and a bit more that I want to share with world.

    But first, just an example of how I made prepared statements really easy to handle with only inheriting from my MySQLDatabase class! Specially if you program a singleton class for your database connection and let __construct and __destruct do its magic!

    You can really inherit from this class and see how easy is implementing prepared statements in your php project!

Example of usage

    And now... the code itself!

Code for MySQLDatabase class

    I hope someone find it usefull!

Friday, February 11, 2011

About Prepared Statements

    Well, I didn't know much about the benefit of having prepared statements as of today. But thanks to trinitycore I discovered a lot.

    As well as trinitycore (which is a framework for a World of Warcraft server and they do it for learning purposes), I learnt too.

    I saw they were moving to Prepared Statements almost all their queries, and wanted to do so on my own projects (specially php ones).

     If you code in OO paradigm, simply prepare all your statements in __construct, and close them in your __destruct ($stmt->close()) function.

    The benefits were huge:

  • Avoid ALL kind of SQL injection by treating parameters as strictly parameters. This way, even if a given parameter has some kind of SQL operator, it will be treated as a regular string, rather than execute what it contains.
  •  If a prepared statement contains any SQL syntax error (fields not existing, misspelling of a sentence, etc), the STMT object WILL NOT be created, and thus, in destructor, a warning will be raised when you call close function. This way, you can autocheck a sentence WITHOUT actually calling it, and thus, not modifying your database only to check if syntax is OK.
  • Also, you will keep SQL data as FAR as you can, and you can encapsulate even more, and more secure, since the only thing you do to query is TO BIND parameters, instead of writting the whole query. That could help you in a possible future redesign changing the less code as possible.
  • Speed: That query is stored in server only ONCE, and every time you run it, you only send its parameters to server. This way, you save time, bandwidth and you can focus your code in everything but database.

    There are even more benefits, but.. try them by yourself in your projects!