linux-kernel - Re: [PATCH] KEYS: encrypted: fix key instantiation with user-provided data

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Date:   Tue, 20 Sep 2022 08:06:15 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Nikolaus Voss <nv@...n.de>
Cc:     Mimi Zohar <zohar@...ux.ibm.com>,
        David Howells <dhowells@...hat.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        linux-integrity@...r.kernel.org, keyrings@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KEYS: encrypted: fix key instantiation with
 user-provided data

On Fri, Sep 16, 2022 at 07:45:29AM +0200, Nikolaus Voss wrote:
> Commit cd3bc044af48 ("KEYS: encrypted: Instantiate key with user-provided
> decrypted data") added key instantiation with user provided decrypted data.
> The user data is hex-ascii-encoded but was just memcpy'ed to the binary buffer.
> Fix this to use hex2bin instead.
> 
> Fixes: cd3bc044af48 ("KEYS: encrypted: Instantiate key with user-provided decrypted data")
> Cc: stable <stable@...nel.org>
> Signed-off-by: Nikolaus Voss <nikolaus.voss@...g-streit.com>
> ---
>  security/keys/encrypted-keys/encrypted.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
> index e05cfc2e49ae..1e313982af02 100644
> --- a/security/keys/encrypted-keys/encrypted.c
> +++ b/security/keys/encrypted-keys/encrypted.c
> @@ -627,7 +627,7 @@ static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
>  			pr_err("encrypted key: instantiation of keys using provided decrypted data is disabled since CONFIG_USER_DECRYPTED_DATA is set to false\n");
>  			return ERR_PTR(-EINVAL);
>  		}
> -		if (strlen(decrypted_data) != decrypted_datalen) {
> +		if (strlen(decrypted_data) != decrypted_datalen * 2) {

This looks wrong. What does cap decrypted_data, and why strnlen()
is not used?

>  			pr_err("encrypted key: decrypted data provided does not match decrypted data length provided\n");

Using pr_err() is probably wrong here and has different prefix
than elsewhere in the file (also most of other uses of pr_err()
are wrong apparently). Nothing bad is really happening.

And who does make any sense of that error message anyway?

For one, I don't understand it.

>  			return ERR_PTR(-EINVAL);
>  		}
> @@ -791,8 +791,8 @@ static int encrypted_init(struct encrypted_key_payload *epayload,
>  		ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv);
>  	} else if (decrypted_data) {
>  		get_random_bytes(epayload->iv, ivsize);
> -		memcpy(epayload->decrypted_data, decrypted_data,
> -				   epayload->decrypted_datalen);
> +		ret = hex2bin(epayload->decrypted_data, decrypted_data,
> +			      epayload->decrypted_datalen);
>  	} else {
>  		get_random_bytes(epayload->iv, ivsize);
>  		get_random_bytes(epayload->decrypted_data, epayload->decrypted_datalen);
> -- 
> 2.34.1
> 


BR, Jarkko