linux-kernel - Re: [PATCH v2] crypto: AF_ALG - add support for keys/asymmetric-type

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Date:	Wed, 13 Jan 2016 12:27:42 +0000
From:	David Woodhouse <dwmw2@...radead.org>
To:	Tadeusz Struk <tstruk@...il.com>, herbert@...dor.apana.org.au
Cc:	tadeusz.struk@...el.com, smueller@...onox.de,
	linux-api@...r.kernel.org, marcel@...tmann.org,
	linux-kernel@...r.kernel.org, dhowells@...hat.com,
	keyrings@...r.kernel.org, linux-crypto@...r.kernel.org,
	zohar@...ux.vnet.ibm.com
Subject: Re: [PATCH v2] crypto: AF_ALG - add support for keys/asymmetric-type

On Sat, 2015-12-26 at 07:50 -0800, Tadeusz Struk wrote:
> +static int alg_setkey_id(void *private, const u8 *key, unsigned int keylen,
> +                        int (*setkey)(void *private, const u8 *key,
> +                                      unsigned int keylen))
> +{
> +       struct key *keyring;
> +       struct public_key *pkey;
> +       char key_name[12];
> +       u32 keyid = *((u32 *)key);
> +       int err;
> +
> +       sprintf(key_name, "id:%08x", keyid);
> +       keyring = request_key(&key_type_asymmetric, key_name, NULL);
> +
> +       err = -ENOKEY;
> +       if (IS_ERR(keyring))
> +               goto out;
> +
> +       pkey = keyring->payload.data[asym_crypto];
> +       if (!pkey) {
> +               key_put(keyring);
> +               goto out;
> +       }
> +
> +       err = setkey(private, pkey->key, pkey->keylen);
> +       key_put(keyring);
> +
> +out:
> +       return err;
> +}

This seems entirely wrong to me. You cannot just assume that the
private key data are available in software form to the kernel and can
be extracted.

Please ensure you test this with a key in a TPM, or in a SGX software
enclave or something like that.

David, is there a way to do that test purely in software without
needing hardware support? We know that the data might not actually be
present in all cases... is there an easy test for that case?

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation


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