(PHP 5 >= 5.3.0, PHP 7)
openssl_encrypt — 加密数据
$data
, string $method
, string $key
[, int $options = 0
[, string $iv = ""
[, string &$tag = NULL
[, string $aad = ""
[, int $tag_length = 16
]]]]] )以指定的方式和 key 加密数据，返回原始或 base64 编码后的字符串。
data待加密的明文信息数据。
method密码学方式。openssl_get_cipher_methods() 可获取有效密码方式列表。
keykey。
options
options 是以下标记的按位或：
OPENSSL_RAW_DATA 、
OPENSSL_ZERO_PADDING。
iv非 NULL 的初始化向量。
tag使用 AEAD 密码模式（GCM 或 CCM）时传引用的验证标签。
aad附加的验证数据。
tag_length
验证 tag 的长度。GCM 模式时，它的范围是 4 到 16。
成功时返回加密后的字符串， 或者在失败时返回 FALSE。
method 传入未知算法时，产生 E_WARNING 级别的错误。
iv 传入空字符串时产生 E_WARNING 级别的错误。
| 版本 | 说明 |
|---|---|
| 5.3.3 |
增加 iv 参数。
|
| 5.4.0 |
raw_output 改到 options。
|
| 7.1.0 | 增加了 tag、aad、tag_length 参数 |
Example #1 PHP 7.1+ 下 GCM 模式的 AES 认证加密例子
<?php
//$key should have been previously generated in a cryptographically safe way, like openssl_random_pseudo_bytes
$plaintext = "message to be encrypted";
$cipher = "aes-128-gcm";
if (in_array($cipher, openssl_get_cipher_methods()))
{
$ivlen = openssl_cipher_iv_length($cipher);
$iv = openssl_random_pseudo_bytes($ivlen);
$ciphertext = openssl_encrypt($plaintext, $cipher, $key, $options=0, $iv, $tag);
//store $cipher, $iv, and $tag for decryption later
$original_plaintext = openssl_decrypt($ciphertext, $cipher, $key, $options=0, $iv, $tag);
echo $original_plaintext."\n";
}
?>
Example #2 PHP 5.6+ 的 AES 认证加密例子
<?php
//$key previously generated safely, ie: openssl_random_pseudo_bytes
$plaintext = "message to be encrypted";
$ivlen = openssl_cipher_iv_length($cipher="AES-128-CBC");
$iv = openssl_random_pseudo_bytes($ivlen);
$ciphertext_raw = openssl_encrypt($plaintext, $cipher, $key, $options=OPENSSL_RAW_DATA, $iv);
$hmac = hash_hmac('sha256', $ciphertext_raw, $key, $as_binary=true);
$ciphertext = base64_encode( $iv.$hmac.$ciphertext_raw );
//decrypt later....
$c = base64_decode($ciphertext);
$ivlen = openssl_cipher_iv_length($cipher="AES-128-CBC");
$iv = substr($c, 0, $ivlen);
$hmac = substr($c, $ivlen, $sha2len=32);
$ciphertext_raw = substr($c, $ivlen+$sha2len);
$original_plaintext = openssl_decrypt($ciphertext_raw, $cipher, $key, $options=OPENSSL_RAW_DATA, $iv);
$calcmac = hash_hmac('sha256', $ciphertext_raw, $key, $as_binary=true);
if (hash_equals($hmac, $calcmac))//PHP 5.6+ timing attack safe comparison
{
echo $original_plaintext."\n";
}
?>
<?php
string openssl_encrypt (
string $data ,
string $method ,
string $key,
int $options = 0, // optional
string $iv = "", // optional
string &$tag = NULL, // optional
string $aad = "", // optional
int $tag_length = 16 // optional
)
// (a kinder, gentler function header)
?>
Important: The key should have exactly the same length as the cipher you are using. For example, if you use AES-256 then you should provide a $key that is 32 bytes long (256 bits == 32 bytes). Any additional bytes in $key will be truncated and not used at all.
How to migrate from mcrypt to openssl with backward compatibility.
In my case I used Blowfish in ECB mode. The task was to decrypt data with openssl_decrypt, encrypted by mcrypt_encrypt and vice versa. It was obvious for a first sight. But in fact openssl_encrypt and mcrypt_encript give different results in most cases.
Investigating the web I found out that the reason is in different padding methods. And for some reasons openssl_encrypt behave the same strange way with OPENSSL_ZERO_PADDING and OPENSSL_NO_PADDING options: it returns FALSE if encrypted string doesn't divide to the block size. To solve the problem you have to pad your string with NULs by yourself.
The second question was the key length. Both functions give the same result if the key length is between 16 and 56 bytes. And I managed to find that if your key is shorter than 16 bytes, you just have to repeat it appropriate number of times.
And finally the code follows which works the same way on openssl and mcrypt libraries.
<?php
function encrypt($data, $key)
{
$l = strlen($key);
if ($l < 16)
$key = str_repeat($key, ceil(16/$l));
if ($m = strlen($data)%8)
$data .= str_repeat("\x00", 8 - $m);
if (function_exists('mcrypt_encrypt'))
$val = mcrypt_encrypt(MCRYPT_BLOWFISH, $key, $data, MCRYPT_MODE_ECB);
else
$val = openssl_encrypt($data, 'BF-ECB', $key, OPENSSL_RAW_DATA | OPENSSL_NO_PADDING);
return $val;
}
function decrypt($data, $key)
{
$l = strlen($key);
if ($l < 16)
$key = str_repeat($key, ceil(16/$l));
if (function_exists('mcrypt_encrypt'))
$val = mcrypt_decrypt(MCRYPT_BLOWFISH, $key, $data, MCRYPT_MODE_ECB);
else
$val = openssl_decrypt($data, 'BF-ECB', $key, OPENSSL_RAW_DATA | OPENSSL_NO_PADDING);
return $val;
}
$data = 'my secret message';
$key = 'dontsay';
$c = encrypt($data, $key);
$d = decrypt($c, $key);
var_dump($c);
var_dump($d);
?>
Gives:
string(32) "SWBMedXJIxuA9FcMOqCqomk0E5nFq6wv"
string(24) "my secret message\000\000\000\000\000\000\000"
To check if cipher uses IV use openssl_cipher_iv_length it returns length if exist, 0 if not, false if cipher is unknown.
PHP lacks a build-in function to encrypt and decrypt large files. `openssl_encrypt()` can be used to encrypt strings, but loading a huge file into memory is a bad idea.
So we have to write a userland function doing that. This example uses the symmetric AES-128-CBC algorithm to encrypt smaller chunks of a large file and writes them into another file.
# Encrypt Files
<?php
/**
* Define the number of blocks that should be read from the source file for each chunk.
* For 'AES-128-CBC' each block consist of 16 bytes.
* So if we read 10,000 blocks we load 160kb into memory. You may adjust this value
* to read/write shorter or longer chunks.
*/
define('FILE_ENCRYPTION_BLOCKS', 10000);
/**
* Encrypt the passed file and saves the result in a new file with ".enc" as suffix.
*
* @param string $source Path to file that should be encrypted
* @param string $key The key used for the encryption
* @param string $dest File name where the encryped file should be written to.
* @return string|false Returns the file name that has been created or FALSE if an error occured
*/
function encryptFile($source, $key, $dest)
{
$key = substr(sha1($key, true), 0, 16);
$iv = openssl_random_pseudo_bytes(16);
$error = false;
if ($fpOut = fopen($dest, 'w')) {
// Put the initialzation vector to the beginning of the file
fwrite($fpOut, $iv);
if ($fpIn = fopen($source, 'rb')) {
while (!feof($fpIn)) {
$plaintext = fread($fpIn, 16 * FILE_ENCRYPTION_BLOCKS);
$ciphertext = openssl_encrypt($plaintext, 'AES-128-CBC', $key, OPENSSL_RAW_DATA, $iv);
// Use the first 16 bytes of the ciphertext as the next initialization vector
$iv = substr($ciphertext, 0, 16);
fwrite($fpOut, $ciphertext);
}
fclose($fpIn);
} else {
$error = true;
}
fclose($fpOut);
} else {
$error = true;
}
return $error ? false : $dest;
}
?>
# Decrypt Files
To decrypt files that have been encrypted with the above function you can use this function.
<?php
/**
* Dencrypt the passed file and saves the result in a new file, removing the
* last 4 characters from file name.
*
* @param string $source Path to file that should be decrypted
* @param string $key The key used for the decryption (must be the same as for encryption)
* @param string $dest File name where the decryped file should be written to.
* @return string|false Returns the file name that has been created or FALSE if an error occured
*/
function decryptFile($source, $key, $dest)
{
$key = substr(sha1($key, true), 0, 16);
$error = false;
if ($fpOut = fopen($dest, 'w')) {
if ($fpIn = fopen($source, 'rb')) {
// Get the initialzation vector from the beginning of the file
$iv = fread($fpIn, 16);
while (!feof($fpIn)) {
// we have to read one block more for decrypting than for encrypting
$ciphertext = fread($fpIn, 16 * (FILE_ENCRYPTION_BLOCKS + 1));
$plaintext = openssl_decrypt($ciphertext, 'AES-128-CBC', $key, OPENSSL_RAW_DATA, $iv);
// Use the first 16 bytes of the ciphertext as the next initialization vector
$iv = substr($ciphertext, 0, 16);
fwrite($fpOut, $plaintext);
}
fclose($fpIn);
} else {
$error = true;
}
fclose($fpOut);
} else {
$error = true;
}
return $error ? false : $dest;
}
?>
Source: http://stackoverflow.com/documentation/php/5794/cryptography/25499/
There still seems to be some confusion about the "password" argument to this function. It accepts a binary string for the key (ie. NOT encoded), at least for the cipher methods I tried (AES-128-CTR and AES-256-CTR). One of the posts says you should hex encode the key (which is wrong), and some say you should hash the key but don't make it clear how to properly pass the hashed key.
Instead of the post made by anonymous, this should be more accurate info about the parameters:
data - BINARY string
method - regular string, from openssl_get_cipher_methods()
password - BINARY string (ie. the encryption key in binary)
options - integer (use the constants provided)
iv - BINARY string
This is not only from my testing, but backed up by the usage of this function by https://github.com/defuse/php-encryption
There's a lot of confusion plus some false guidance here on the openssl library.
The basic tips are:
aes-256-ctr is arguably the best choice for cipher algorithm as of 2016. This avoids potential security issues (so-called padding oracle attacks) and bloat from algorithms that pad data to a certain block size. aes-256-gcm is preferable, but not usable until the openssl library is enhanced, which is due in PHP 7.1
Use different random data for the initialisation vector each time encryption is made with the same key. mcrypt_create_iv() is one choice for random data. AES uses 16 byte blocks, so you need 16 bytes for the iv.
Join the iv data to the encrypted result and extract the iv data again when decrypting.
Pass OPENSSL_RAW_DATA for the flags and encode the result if necessary after adding in the iv data.
Hash the chosen encryption key (the password parameter) using openssl_digest() with a hash function such as sha256, and use the hashed value for the password parameter.
There's a simple Cryptor class on GitHub called php-openssl-cryptor that demonstrates encryption/decryption and hashing with openssl, along with how to produce and consume the data in base64 and hex as well as binary. It should lay the foundations for better understanding and making effective use of openssl with PHP.
Hopefully it will help anyone looking to get started with this powerful library.
Contrary to some of the other comments here, I'm not certain that Password is indeed being improperly treated as the direct key. I say this because I've been passing random text values into this parameter which would be invalid as hex input. It seems to be hashing the password I provide, using what algorithm I do not know, because otherwise I'd expect it to throw an exception instead of working as expected.
That said, I'm using openssl_decrypt() to decrypt data that was only encrypted with openssl_encrypt(). I've not had to try to decrypt data where I do know for certain what the direct key is to know if I have an issue with bad pad blocks or any other exceptions which would indicate a key mismatch.
Note, that if you don't specify the ...RAW_DATA option, then you get a base64 encoded result. I lost a few hours because my PHP didn't have the OPENSSL_RAW_DATA constant, and after I'd carefully base64 encoded the result, it just wasn't decoding...
Beware of the padding this method adds !
<?php
$encryption_key = openssl_random_pseudo_bytes(32);
$iv = openssl_random_pseudo_bytes(16);
$data = openssl_random_pseudo_bytes(32);
for ($i = 0; $i < 5; $i++) {
$data = openssl_encrypt($data, 'aes-256-cbc', $encryption_key, OPENSSL_RAW_DATA, $iv);
echo strlen($data) . "\n";
}
?>
With this sample the output will be:
48
64
80
96
112
This is because our $data is already taking all the block size, so the method is adding a new block which will contain only padded bytes.
The only solution that come to my mind to avoid this situation is to add the option OPENSSL_ZERO_PADDING along with the first one:
<?php
$data = openssl_encrypt($data, 'aes-256-cbc', $encryption_key, OPENSSL_RAW_DATA|OPENSSL_ZERO_PADDING, $iv);
?>
/!\ Be careful when using this option, be sure that you provide data that have already been padded or that takes already all the block size.
Since the $options are not documented, I'm going to clarify what they mean here in the comments. Behind the scenes, in the source code for /ext/openssl/openssl.c:
EVP_EncryptInit_ex(&cipher_ctx, NULL, NULL, key, (unsigned char *)iv);
if (options & OPENSSL_ZERO_PADDING) {
EVP_CIPHER_CTX_set_padding(&cipher_ctx, 0);
}
And later:
if (options & OPENSSL_RAW_DATA) {
outbuf[outlen] = '\0';
RETVAL_STRINGL((char *)outbuf, outlen, 0);
} else {
int base64_str_len;
char *base64_str;
base64_str = (char*)php_base64_encode(outbuf, outlen, &base64_str_len);
efree(outbuf);
RETVAL_STRINGL(base64_str, base64_str_len, 0);
}
So as we can see here, OPENSSL_ZERO_PADDING has a direct impact on the OpenSSL context. EVP_CIPHER_CTX_set_padding() enables or disables padding (enabled by default). So, OPENSSL_ZERO_PADDING disables padding for the context, which means that you will have to manually apply your own padding out to the block size. Without using OPENSSL_ZERO_PADDING, you will automatically get PKCS#7 padding.
OPENSSL_RAW_DATA does not affect the OpenSSL context but has an impact on the format of the data returned to the caller. When OPENSSL_RAW_DATA is specified, the returned data is returned as-is. When it is not specified, Base64 encoded data is returned to the caller.
Hope this saves someone a trip to the PHP source code to figure out what the $options do. Pro developer tip: Download and have a copy of the PHP source code locally so that, when the PHP documentation fails to live up to quality expectations, you can see what is actually happening behind the scenes.
Just a couple of notes about the parameters:
data - It is interpreted as a binary string
method - Regular string, make sure you check openssl_get_cipher_methods() for a list of the ciphers available in your server*
password - As biohazard mentioned before, this is actually THE KEY! It should be in hex format.
options - As explained in the Parameters section
iv - Initialization Vector. Different than biohazard mentioned before, this should be a BINARY string. You should check for your particular implementation.
To verify the length/format of your IV, you can provide strings of different lengths and check the error log. For example, in PHP 5.5.9 (Ubuntu 14.04 LTS), providing a 32 byte hex string (which would represent a 16 byte binary IV) throws an error.
"IV passed is 32 bytes long which is longer than the 16 expected by the selected cipher" (cipher chosen was 'aes-256-cbc' which uses an IV of 128 bits, its block size).
Alternatively, you can use openssl_cipher_iv_length().
From the security standpoint, make sure you understand whether your IV needs to be random, secret or encrypted. Many times the IV can be non-secret but it has to be a cryptographically secure random number. Make sure you generate it with an appropriate function like openssl_random_pseudo_bytes(), not mt_rand().
*Note that the available cipher methods can differ between your dev server and your production server! They will depend on the installation and compilation options used for OpenSSL in your machine(s).
Might be useful to people trying to use 'aes-256-cbc' cipher (and probably other cbc ciphers) in collaboration with other implementations of AES (C libs for example) that the openssl extension has a strict implementation regarding padding bytes. I found the solution only by manually going through the openssl source.
In C, you would want to pad plaintexts the following way (assuming all mem allocations are proper):
nPadding = ( 16 - ( bufferSize % 16 ) ) ? ( 16 - ( bufferSize % 16 ) ) : 16;
for( index = bufferSize; index < bufferSize + nPadding; index++ )
{
plaintext[ index ] = (char)nPadding;
}
while decryptions are validated like:
isSuccess = TRUE;
for( index = bufferSize - 1; index > ( bufferSize - nPadding ); index-- )
{
if( plaintext[ index ] != nPadding )
{
isSuccess = FALSE;
break;
}
}
decryptedSize = bufferSize - nPadding;
In plain english, the buffer must be padded up to blockSize. If the buffer is already a multiple of blockSize, you add an entire new blockSize bytes as padding.
The value of the padding bytes MUST be the number of padding bytes as a byte...
So 5 bytes of padding will result in the following bytes added at the end of the ciphertext:
[ 0x05 ][ 0x05 ][ 0x05 ][ 0x05 ][ 0x05 ]
Hope this saves someone else a few hours of their life.
Be advised there was a memory leak in this function: https://bugs.php.net/bug.php?id=54060. I believe this got fixed in 5.3.6, but on production webservers running 5.3.5 with modest traffic, this became a memory hemorrhage that brought my site down. Look at mcrypt_encrypt instead.
PHP OpenSSL functions openssl_encrypt() and openssl_decrypt() seem to use PKCS5/7 style padding for all symmetric ciphers. Upon this, you can't use them to encrypt using null byte padding or to decrypt null byte padded data.
The developers of the wrapper forgot the padding scheme flags... :(
Many users give up with handilng problem when openssl command line tool cant decrypt php openssl encrypted file which is encrypted with openssl_encrypt function.
For example how beginner is encrypting data:
<?php
$string = 'It works ? Or not it works ?';
$pass = '1234';
$method = 'aes128';
file_put_contents ('./file.encrypted', openssl_encrypt ($string, $method, $pass));
?>
And then how beginner is trying to decrypt data from command line:
# openssl enc -aes-128-cbc -d -in file.encrypted -pass pass:123
Or even if he/she determinates that openssl_encrypt output was base64 and tries:
# openssl enc -aes-128-cbc -d -in file.encrypted -base64 -pass pass:123
Or even if he determinates that base64 encoded file is represented in one line and tries:
# openssl enc -aes-128-cbc -d -in file.encrypted -base64 -A -pass pass:123
Or even if he determinates that IV is needed and adds some string iv as encryption function`s fourth parameter and than adds hex representation of iv as parameter in openssl command line :
# openssl enc -aes-128-cbc -d -in file.encrypted -base64 -pass pass:123 -iv -iv 31323334353637383132333435363738
Or even if he determinates that aes-128 password must be 128 bits there fore 16 bytes and sets $pass = '1234567812345678' and tries:
# openssl enc -aes-128-cbc -d -in file.encrypted -base64 -pass pass:1234567812345678 -iv -iv 31323334353637383132333435363738
All these troubles will have no result in any case.
BECAUSE THE PASSWORD PARAMETER DOCUMENTED HERE IS NOT THE PASSWORD.
It means that the password parameter of the function is not the same string used as [-pass pass:] parameter with openssl cmd tool for file encryption decryption.
IT IS THE KEY !
And now how to correctly encrypt data with php openssl_encrypt and how to correctly decrypt it from openssl command line tool.
<?php
function strtohex($x)
{
$s='';
foreach (str_split($x) as $c) $s.=sprintf("%02X",ord($c));
return($s);
}
$source = 'It works !';
$iv = "1234567812345678";
$pass = '1234567812345678';
$method = 'aes-128-cbc';
echo "\niv in hex to use: ".strtohex ($iv);
echo "\nkey in hex to use: ".strtohex ($pass);
echo "\n";
file_put_contents ('./file.encrypted',openssl_encrypt ($source, $method, $pass, true, $iv));
$exec = "openssl enc -".$method." -d -in file.encrypted -nosalt -nopad -K ".strtohex($pass)." -iv ".strtohex($iv);
echo 'executing: '.$exec."\n\n";
echo exec ($exec);
echo "\n";
?>
IV and Key parameteres passed to openssl command line must be in hex representation of string.
The correct command for decrypting is:
# openssl enc -aes-128-cbc -d -in file.encrypted -nosalt -nopad -K 31323334353637383132333435363738 -iv 31323334353637383132333435363738
As it has no salt has no padding and by setting functions third parameter we have no more base64 encoded file to decode. The command will echo that it works...
: /
The list of methods for this function can be obtained with openssl_get_cipher_methods();
The password can be encrypted with the openssl_private/public_encrypt()