linux-kernel - Re: [PATCH 4.4 19/92] sctp: delay the authentication for the duplicated cookie-echo chunk

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Date:   Wed, 06 Jun 2018 23:31:47 +0100
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Xin Long <lucien.xin@...il.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Neil Horman <nhorman@...driver.com>
Cc:     stable@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4.4 19/92] sctp: delay the authentication for the
 duplicated cookie-echo chunk

On Thu, 2018-05-24 at 11:37 +0200, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Xin Long <lucien.xin@...il.com>
> 
> [ Upstream commit 59d8d4434f429b4fa8a346fd889058bda427a837 ]
> 
> Now sctp only delays the authentication for the normal cookie-echo
> chunk by setting chunk->auth_chunk in sctp_endpoint_bh_rcv(). But
> for the duplicated one with auth, in sctp_assoc_bh_rcv(), it does
> authentication first based on the old asoc, which will definitely
> fail due to the different auth info in the old asoc.
[...]
> --- a/net/sctp/associola.c
> +++ b/net/sctp/associola.c
> @@ -1000,9 +1000,10 @@ static void sctp_assoc_bh_rcv(struct wor
>  	struct sctp_endpoint *ep;
>  	struct sctp_chunk *chunk;
>  	struct sctp_inq *inqueue;
> -	int state;
>  	sctp_subtype_t subtype;
> +	int first_time = 1;	/* is this the first time through the loop */
>  	int error = 0;
> +	int state;
>  
>  	/* The association should be held so we should be safe. */
>  	ep = asoc->ep;
> @@ -1013,6 +1014,30 @@ static void sctp_assoc_bh_rcv(struct wor
>  		state = asoc->state;
>  		subtype = SCTP_ST_CHUNK(chunk->chunk_hdr->type);
>  
> +		/* If the first chunk in the packet is AUTH, do special
> +		 * processing specified in Section 6.3 of SCTP-AUTH spec
> +		 */
> +		if (first_time && subtype.chunk == SCTP_CID_AUTH) {
> +			struct sctp_chunkhdr *next_hdr;
> +
> +			next_hdr = sctp_inq_peek(inqueue);
> +			if (!next_hdr)
> +				goto normal;
> +
> +			/* If the next chunk is COOKIE-ECHO, skip the AUTH
> +			 * chunk while saving a pointer to it so we can do
> +			 * Authentication later (during cookie-echo
> +			 * processing).
> +			 */
> +			if (next_hdr->type == SCTP_CID_COOKIE_ECHO) {
> +				chunk->auth_chunk = skb_clone(chunk->skb,
> +							      GFP_ATOMIC);
> +				chunk->auth = 1;

Doesn't the first_time flag need to be cleared here (and before the
other continue statement in this loop)?

Ben.

> +				continue;
> +			}
> +		}
> +
> +normal:
[...]

-- 
Ben Hutchings, Software Developer                         Codethink Ltd
https://www.codethink.co.uk/                 Dale House, 35 Dale Street
                                     Manchester, M1 2HF, United Kingdom