CODEWITHSUNDEEP
phpencryptionphp-openssl
saeid ezzati
saeid ezzati

Reputation: 891

decrypt encrypted private key by password and openssl_decrypt

I have a private key encrypted script with a password and here is its output:

{
    "iv":"Ra6kDXvh2DBiZ0r37pNuzg==",
    "v":1,
    "iter":10000,
    "ks":256,
    "ts":64,
    "mode":"ccm",
    "adata":"",
    "cipher":"aes",
    "salt":"pNN1xP7SZks=",
    "ct":"Sd8p3C3vPuW+LD
    nO9GwltDnqGOHg7+qguaEjQxzidEh5RNDh7bodJfmzmoB4DjFYQ4Qi8ferWoVV6bwJ2Q9/BnqI+
    X4A1MQY/HgVbtc9AnXj1EczsKxsUxG/ET7W+OBGQGLddzKVC38ACRg9q0NjOieOH0yTx64="
}

I dont know exactly whats name of this type of encryption and I want to know how to decrypt it using a password and PHP.

According to my research, it can be decrypted by the openssl_decrypt function. But I couldn't find how to use my parameters in this function.

For example, I have a key called salt in the json that I have and I don't know what to do with it.

Also, in the openssl_decrypt function, there is an input argument called tag. I don't know the json key that it belongs to.

This is a sample of the code I'm using:

$ct = 'Sd8p3C3vPuW+LD
nO9GwltDnqGOHg7+qguaEjQxzidEh5RNDh7bodJfmzmoB4DjFYQ4Qi8ferWoVV6bwJ2Q9/BnqI+
X4A1MQY/HgVbtc9AnXj1EczsKxsUxG/ET7W+OBGQGLddzKVC38ACRg9q0NjOieOH0yTx64=';
$method = 'aes-256-ccm';
$password = 'Qw370207610';
$options = 0;
$iv = base64_decode('Ra6kDXvh2DBiZ0r37pNuzg==');

$output = openssl_decrypt($ct, $method, $password, $options, $iv);

And I received this error:

openssl_decrypt(): Setting of IV length for AEAD mode failed

UPDATE:

So I have gethered that for producing the third parameter (key) that is used in openssl_decrypt, I should act like this:

$ks = 256;
$key_length = $ks/8;
$password = 'Qw370207610';
$salt_base64 = 'pNN1xP7SZks=';
$salt = base64_decode($salt_base64);
$iterations = 10000;
$digest_algorithm = 'sha256';

$key = openssl_pbkdf2 ( $password , $salt , $key_length , $iterations , $digest_algorithm );

And then it can be decrypted in this way:

$ct_base64 = 'Sd8p3C3vPuW+LD
nO9GwltDnqGOHg7+qguaEjQxzidEh5RNDh7bodJfmzmoB4DjFYQ4Qi8ferWoVV6bwJ2Q9/BnqI+
X4A1MQY/HgVbtc9AnXj1EczsKxsUxG/ET7W+OBGQGLddzKVC38ACRg9q0NjOieOH0yTx64=';
$ct = base64_decode($ct_base64);

$ts = 64;
$tag_length = $ts/8;
$tag = substr($ct,-$tag_length);
$ccm = substr($ct,0,-$tag_length);

$method = 'aes-256-ccm';

$options = OPENSSL_RAW_DATA;
$iv_base64 = 'Ra6kDXvh2DBiZ0r37pNuzg==';
$iv = base64_decode($iv_base64); // 16 bytes length

$output = openssl_decrypt($ccm, $method, $key, $options, $iv, $tag);

However in PHP, for decrypting aes-ccm, there is just openssl, and they haven't offered another library.

On the other hand, these functions don't accept an IV (initialization vector) larger than 12 bytes. Because IV of my encrypted message is 16 bytes and it can not be decrypted in PHP at all !!

Have PHP developers not thought about this?

I have never had such problems in nodejs, but I always face some kind of restriction in PHP.

Upvotes: 0

Views: 1734

Answers (2)

shorol
shorol

Reputation: 1000

please try this : From mcrypt_decrypt to openssl_decrypt

and for this you don't need the value of $iv if you give your data raw-value it will convert into base64 and other operation will be done by your method and algorithm. I think this might help you.

Upvotes: 0

Maarten Bodewes
Maarten Bodewes

Reputation: 94058

No, you have a password encrypted script, where a secret key is generated from that password. And it was generated using SJCL or a compatible library, demonstration here.

The salt and iteration count iter are input to the PBKDF2 function, which generates the AES key.

I hope you can progress using this information, because SO is not a code delivery service. Fortunately I know that OpenSSL contains PBKDF2, but I'm not sure if it is exposed to you.

Upvotes: 0

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