Question

My script uses openssl_private_decrypt() to decrypt a string encrypted with RSA in another program. Currently it writes to a file. But when I try to open it up in a text editor, it says it can’t detect the encoding. If I try to echo it, nothing appears. If I output it’s length, I get 256, instead of the correct 3.

I know the decryption is done right because using the cat terminal command on the output file gives the correct data.

$ cat decrypted.txt

It looks like this is a character encoding problem, a problem I hear can give a lot of pain in PHP. I even tried utf8_encode(). What might the problem be?

Here’s the code:

$results = '';
openssl_private_decrypt(
    base64_decode(
        <<<EOS
QWlG+AZIt9GE0hw0wwcPRtUWueMLBxj3YWpa5zQBoz1ttnt7TvlxDtYWZcvaUL/qr2CJCADE2iTR
G72FhAwew2fhqlqmsxL7Nns3yegflTTMXyilVM3mPU4Cx94ylLfa+ZrqrNEepaRorNJ/js5iTq9i
avegO/kYOv4zhEsZirlk/Mj0vVv6irWo8WyZoCDC2SwfGWeSUI8F4pq4FUkRh9V/0zAUZ+3P0A7Z
SrA80dSa6U/J+poRcmE1vRLQXvM8dBtFRKmb0zfltLUBMcMhcglzAhcpemJ99OCZmUuynFRcRNkj
CkOLsO+lSHntcbmXqsKE+of78gnU3tp5hHSHIg==
EOS
    ),
    $results,
    openssl_pkey_get_private(
        // load private key
    ),
    OPENSSL_NO_PADDING
);
echo $results;

Answer 1

The fact that you’re getting decrypted data exactly the length of a single block instead of the length of your expected data is really, really pointing towards a padding problem.

Make sure you’re using the same padding flag on both sides.