PHPKonf Istanbul PHP Conference 2019 - Call for Papers

Modelo de Armazenamento Criptografado

SSL/SSH protege dados transitando de um cliente para o servidor, mas não protege os dados guardados em um banco de dados. SSL é um protocolo on-the-wire.

Uma vez que o atacante ganha acesso direto ao seu banco de dados(desviando do servidor web), os dados armazenados podem ser expostos ou sofre uso nocivo, a não ser que a informação seja protegida pelo banco em si. Criptografa os dados é uma boa maneira de diminuir essa ameaça, mas poucos bancos de dados oferecem esse tipo de criptografia de dados.

A maneira mais fácil de contornar esse problema é primeiro criar seu próprio pacote de criptografia, e então usá-lo no seus scripts PHP. O PHP pode ajudá-lo com várias extensões, tais como Mcrypt e Mhash, cobrindo uma grande variedade de algoritmos de criptografia. O script criptografa os dados antes de inserí-los no banco de dados e descriptografa quando os recupera. Veja as referência para outros exemplos de como criptografia funciona.

No caso de dados realmente escondidos, se sua representação crua não é necessária (ex.: não será mostrada), usar uma função de hash pode ser levada em consideração. Um exemplo bem conhecido disso é guardar o hash MD5 de uma senha no banco de dados ao invés da senha em si. Veja também crypt() e md5().

Exemplo #1 Usando campo de senha hasheado


// guardando hash da senha
$query  sprintf("INSERT INTO users(name,pwd) VALUES('%s','%s');",
pg_escape_string($username), md5($password));
$result pg_query($connection$query);

// consultando se o usuário enviou a senha correta
$query sprintf("SELECT 1 FROM users WHERE name='%s' AND pwd='%s';",
pg_escape_string($username), md5($password));
$result pg_query($connection$query);

if (
pg_num_rows($result) > 0) {
'Welcome, $username!';
} else {
'Authentication failed for $username.';

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User Contributed Notes 5 notes

seigoryu at hotmail dot de
6 years ago
I would strongly recommend using SHA-2 or better the new SHA-3 hash algorithm. MD5 is practically unusable, since there are very well working rainbow tables around the whole web. Almost the same for SHA-1. Of course you should never do a hash without salting!
7 years ago
Using functions to obfuscate the hash generation does not increase security. This is security by obscurity. The algorithm used to hash the data needs to be secure by itself.

I would not suggest to use other data as salt. For example if you use the username, you won't be able to change the values without rehashing the password.

I would use a dedicated salt value stored in the same database table.

Why? Because a lot of users use the same login credentials on different web services. And in case another service also uses the username as salt, the resulting hashed password might be the same!

Also an attacker may prepare a rainbow table with prehashed passwords using the username and other known data as salt. Using random data would easily prevent this with little programming effort.
11 years ago
A better way to hash would be to use a separate salt for each user. Changing the salt upon each password update will ensure the hashes do not become stale.
about2mount at gmail dot com
3 years ago
It's difficult to post scripts here for all to view on the subject of best security practices. But i would wish to point out that using a salt with a randomized and odd numbered long length salt value is do_able with two Php functions while retrieving and separating the salt when it comes out using simple math functions. But with everything we add we also have to think of the constant standardized login systems we stay behind with.

For one,,, adding and validating two to four passwords is not a bad idea.  Also having no username or email going in. They can be stored after the user logs in after the validation process.  It is possible to store the email on the first signup and only at that time. And if the user loses his passwords then validate by email only upon request within a contact form by a validated phone number stored in the database,, and then via their email account.
Fairydave at the location of
12 years ago
I think the best way to have a salt is not to randomly generate one or store a fixed one. Often more than just a password is saved, so use the extra data. Use things like the username, signup date, user ID, anything which is saved in the same table. That way you save on space used by not storing the salt for each user.

Although your method can always be broken if the hacker gets access to your database AND your file, you can make it more difficult. Use different user data depending on random things, the code doesn't need to make sense, just produce the same result each time. For example:

if ((asc(username character 5) > asc(username character 2))
   if (month the account created > 6)
      salt = ddmmyyyy of account created date
      salt = yyyyddmm of account created date
   if (day of account created > 15)
      salt = user id * asc(username character 3)
      salt = user id + asc(username character 1) + asc(username character 4)

This wont prevent them from reading passwords when they have both database and file access, but it will confuse them and slow them up without much more processing power required to create a random salt
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