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To: Sammy Kaye Powers <me@sammyk.me>, PHP Internals <internals@lists.php.net>
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Message-ID: <a7c0c8d0-ff50-d6c7-f8ba-a0e724ce57d6@heigl.org>
Date: Mon, 12 Dec 2016 17:02:05 +0100
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Subject: Re: [PHP-DEV] More secure defaults for openssl_public_encrypt() &
 openssl_private_decrypt()
From: andreas@heigl.org (Andreas Heigl)

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Am 12.12.16 um 16:26 schrieb Sammy Kaye Powers:
> Hey internals!
>=20
> As pointed out in Paragon's excellent blog post,
> openssl_public_encrypt() & openssl_private_decrypt() defaults to the
> insecure OPENSSL_PKCS1_PADDING constant.
>=20
> https://paragonie.com/blog/2016/12/everything-you-know-about-public-key=
-encryption-in-php-is-wrong#php-openssl-rsa-bad-default
>=20
> What are your thoughts about deprecating OPENSSL_PKCS1_PADDING and
> using OPENSSL_PKCS1_OAEP_PADDING as the new default?

Is that backwards compatible? I'm thinking of decrypting data that was
encrypted with the "old" settings...

I just tested this:

    <?php
    openssl_public_encrypt('Testdata', $crypted, $pubKey,
OPENSSL_PKCS1_OAEP_PADDING);
    openssl_private_decrypt($crypted, $decrypt, $privateKey));
    var_Dump($decrypt);
    // NULL

while this works as expected:

    <?php
    openssl_public_encrypt('Testdata', $crypted, $pubKey,
OPENSSL_PKCS1_OAEP_PADDING);
    openssl_private_decrypt($crypted, $decrypt, $privateKey,
OPENSSL_PKCS1_OAEP_PADDING));
    var_Dump($decrypt);
    // string(8) "Testdata"

So it looks like you're out of luck with your already encrypted data
when the default-padding is changed. And I suppose that those that used
the default aren't aware of that information being a vital part.

And on a first glance I couldn't find a way of retrieving the used
padding from the data. So there might be no way of retrieving that
information other than by guessing/decrypting using all possible
paddings until a valid value is returned...

Just my 0.02 =E2=82=AC

Cheers

Andreas


--=20
                                                              ,,,
                                                             (o o)
+---------------------------------------------------------ooO-(_)-Ooo-+
| Andreas Heigl                                                       |
| mailto:andreas@heigl.org                  N 50=C2=B022'59.5" E 08=C2=B0=
23'58" |
| http://andreas.heigl.org                       http://hei.gl/wiFKy7 |
+---------------------------------------------------------------------+
| http://hei.gl/root-ca                                               |
+---------------------------------------------------------------------+


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