dpca4790 2017-09-25 02:47
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使用PHP加密图像以便在MySQL BLOB中存储然后解密和打印

I'm trying to take an uploaded image, encrypt the image, store it in MySQL, then decrypt it for display when an authorized person requests to see it.

Here's how I'm currently encrypting:

$image = addslashes(file_get_contents($_FILES['users_image']['tmp_name']));
$enc_image = encrypt($image, "long secret random key");

Then I store the $enc_image in a MySQL BLOB field. When I try to decrypt it and print it goes like so:

$img = decrypt($rec['file'], "long secret random key");
echo '<img src="data:image/jpeg;base64,'.base64_encode($img).'"/>';

I'm using this code from this Stackoverflow answer, and I'm seeing the decrypted base-64 text, in my output, but it doesn't display via HTML. Here is a sample encrypted image's attempt at being recovered: https://pastebin.com/miDCP3Gz

NOTE: My "long secret random key" includes a hashed random unique salt, but I am sure I am encrypting and decrypting with the same string.

Any idea why this wouldn't be displaying correctly?

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  • douzi4766 2017-09-25 07:24
    关注

    1. Make sure your image is small enough or your storage location is large enough. If you have anything over 65kB you need a longblob not a blob. Anything over that size will be truncated and lost.

    2. Move the addslashes to right before insertion into the DB, NOT before the encryption. Single quotes (or double depending on which you are using) designate the beginning and end of a string to the MySQL engine. The addslashes function escapes these and other special characters to prevent them from confusing they MySQL engine. The fact that it adds the record to the DB with you performing it before the encryption is merely random chance.

    3. You should know that these images are being saved on the server as temporary files. Unless special precautions are taken, the data in them will remain in the slack space on the HDD. It can easily be retrieved by an adversary using forensics or restoration tools.

    Markup:

    <html>
<head><title>Picture</title></head>
<body>
    <form enctype="multipart/form-data" action="file.php" method="post">
        <input type="hidden" name="MAX_FILE_SIZE" value="600000" />
        <input type="file" name="users_image"/>
        <input type="submit" text="Upload">
    </form>
<?

    if($_SERVER['REQUEST_METHOD'] === 'POST')
    {

        $image = file_get_contents($_FILES['users_image']['tmp_name']);
        //encrypt
        $cipher = "aes-128-cbc";
        $ivlen = openssl_cipher_iv_length($cipher);
        $iv = openssl_random_pseudo_bytes($ivlen);
        $key = openssl_random_pseudo_bytes(128);
        $ciphertext = openssl_encrypt($image, $cipher, $key, $options=0, $iv);

        //add to DB
        $mysqli = mysqli_connect("localhost","testu","","test");
        $query = "INSERT INTO blobtbl(pics) VALUES (\"" . addslashes($ciphertext) ."\")";
        $mysqli->query($query);
        $id = mysqli_insert_id($mysqli);

        //retrieve from DB
        $sql = "SELECT * FROM blobtbl WHERE id = $id";
        $res = $mysqli->query($sql);
        $row=mysqli_fetch_assoc($res);
        $newciphertext = $row['pics'];

        //decrpyt and display
        $img = openssl_decrypt($newciphertext, $cipher, $key, $options=0, $iv);
        echo '<img src="data:image/jpeg;base64,'.base64_encode($img).'"/>';
        echo "<br>Did it work?";
    }
?>
</body>
</html>
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