php implementation of openssl enc

Question

Working with guacamole-auth-json, coding php client implementation.

I need to be able to encrypt hmac sha256 hashed json with aes-128-cbc cipher. I have same input data with hash, but failing to implement encryption.

Working guacamole-auth-json example in bash

#!/bin/bash -e

##
## Encryption/signing key.
##
SECRET_KEY="$1"

##
## The filename of the JSON data being signed and encrypted.
##
JSON_FILENAME="$2"
##

## A null (all zeroes) IV.
##
NULL_IV="00000000000000000000000000000000"

##
## Signs the contents of the given file using the given key. The signature is
## created using HMAC/SHA-256, and is output in binary form to STDOUT, followed
## by the raw contents of the file.
##
## @param KEY
##     The key to use to sign the contents of the given file with HMAC/SHA-256.
##
## @param FILENAME
##     The filename of the file to sign.
##
sign() {

    KEY="$1"
    FILENAME="$2"

    #
    # Write out signature
    #

    openssl dgst                                \
        -sha256 -mac HMAC -macopt hexkey:"$KEY" \
        -binary "$FILENAME"

    #
    # Write out file contents
    #

    cat "$FILENAME"

}

##
## Encrypts all data received through STDIN using the provided key. Data is
## encrypted using 128-bit AES in CBC mode (with a null IV). The encrypted
## result is printed to STDOUT encoded with base64.
##
## @param KEY
##     The key to encrypt STDIN with, as a 16-byte (32-digit) hexadecimal
##     value.
##
encrypt() {

    KEY="$1"

    #
    # Encrypt STDIN
    #

    openssl enc -aes-128-cbc -K "$KEY" -iv "$NULL_IV" -nosalt -a

}

#
# Sign and encrypt file using secret key
#
sign "$SECRET_KEY" "$JSON_FILENAME" | encrypt "$SECRET_KEY"

My other data producing php implementation

$auth_json = "{\n";
$auth_json = $auth_json . "    \"username\" : \"\",\n";
$auth_json = $auth_json . "    \"expires\" : \"1607500000000\",\n";
$auth_json = $auth_json . "    \"connections\" : {\n";
$auth_json = $auth_json . "        \"Trading server 001\" : {\n";
$auth_json = $auth_json . "            \"protocol\" : \"" . get_post_meta( $post->ID,'trading_server_protocol', true ) . "\",\n";
$auth_json = $auth_json . "            \"parameters\" : {\n";
$auth_json = $auth_json . "                \"hostname\" : \"" . get_post_meta( $post->ID,'trading_server_hostname', true ) . "\",\n";
$auth_json = $auth_json . "                \"port\" : \"" . get_post_meta( $post->ID,'trading_server_port', true ) . "\",\n";
$auth_json = $auth_json . "                \"password\" : \"" . get_post_meta( $post->ID,'trading_server_password', true ) . "\",\n";
$auth_json = $auth_json . "                \"read-only\" : \"" . get_post_meta( $post->ID,'trading_server_readonly', true ) . "\"\n";
$auth_json = $auth_json . "            }\n";
$auth_json = $auth_json . "        }\n";
$auth_json = $auth_json . "    }\n";
$auth_json = $auth_json . "}";
            
$encrypt_key = "12345678901234567890123456789012";
$NULL_IV="00000000000000000000000000000000";
// HMAC Hex to byte
$secret     = hex2bin($encrypt_key);
$auth_json_hash = hash_hmac("sha256", $auth_json, $secret);
$auth_json_hash_bin = hash_hmac("sha256", $auth_json, $secret, true);
            
$cipher = "AES-128-CBC";
$data = $auth_json_hash_bin . $auth_json;
$auth_json_encrypted_raw = openssl_encrypt( $data, $cipher, $encrypt_key, $options = OPENSSL_RAW_DATA, $NULL_IV );
$auth_json_encrypted_base64 = base64_encode( $auth_json_encrypted_raw );

I have same hash, but not able to call openssl_encrypt function with same result as produced using bash example.

There is probably some problem with difference between

openssl enc -aes-128-cbc -K "$KEY" -iv "$NULL_IV" -nosalt -a

and

openssl_encrypt( $data, $cipher, $encrypt_key, $options = OPENSSL_RAW_DATA, $NULL_IV )

I understand, that I need to base64 encode result in php (-a switch) and need some solution for (-nosalt switch).

Hint: Dont build JSON manually. Create an object/array or mixture of both and then use JSON_ENCODE() to make the JSON String — RiggsFolly
Key and IV encoding is likely different (hex in bash and raw bytes in php) — Artjom B.
Thanks, that is correct, found it myself just in the same time. :-) — Jan Blaha

Jan Blaha Jan Blaha · Accepted Answer · 2020-12-01T19:03:51

Problem was with hex parameters (encrypt_key, NULL_IV) in php.

Correct code should be

$encrypt_key = "12345678901234567890123456789012";
$NULL_IV="00000000000000000000000000000000";
..
$auth_json_encrypted_raw = openssl_encrypt( $data, $cipher, hex2bin($encrypt_key), $options = OPENSSL_RAW_DATA, hex2bin($NULL_IV) );

php implementation of openssl enc

1 Answers