linux-kernel - Re: [PATCH v3] crypto: gcm - restrict assoclen for rfc4543

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Date:   Tue, 30 Jul 2019 11:50:08 +0000
From:   Horia Geanta <horia.geanta@....com>
To:     Iuliana Prodan <iuliana.prodan@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>
CC:     "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH v3] crypto: gcm - restrict assoclen for rfc4543

On 7/30/2019 2:03 PM, Iuliana Prodan wrote:
> Based on seqiv, IPsec ESP and rfc4543/rfc4106 the assoclen can be 16 or
> 20 bytes.
> 
> From esp4/esp6, assoclen is sizeof IP Header. This includes spi, seq_no
> and extended seq_no, that is 8 or 12 bytes.
> In seqiv, to asscolen is added the IV size (8 bytes).
> Therefore, the assoclen, for rfc4543, should be restricted to 16 or 20
> bytes, as for rfc4106.
> 
> Signed-off-by: Iuliana Prodan <iuliana.prodan@....com>
Reviewed-by: Horia Geantă <horia.geanta@....com>

[...]
> diff --git a/crypto/gcm.c b/crypto/gcm.c
> index 2f3b50f..7eb5ced 100644
> --- a/crypto/gcm.c
> +++ b/crypto/gcm.c
> @@ -1034,11 +1034,23 @@ static int crypto_rfc4543_copy_src_to_dst(struct aead_request *req, bool enc)
>  
>  static int crypto_rfc4543_encrypt(struct aead_request *req)
>  {
> +	int err;
> +
> +	err = crypto_ipsec_check_assoclen(req->assoclen);
> +	if (err)
> +		return err;
> +
>  	return crypto_rfc4543_crypt(req, true);
>  }
Could as well be:
	return crypto_ipsec_check_assoclen(req->assoclen) ?:
	       crypto_rfc4543_crypt(req, true);

The same for decryption.

Horia