Patchwork Fix out-of-bounds reading in sctp_asoc_get_hmac()

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Submitter Dan Rosenberg
Date Oct. 1, 2010, 9:51 p.m.
Message ID <1285969907.2814.49.camel@Dan>
Download mbox | patch
Permalink /patch/66524/
State Accepted
Delegated to: David Miller
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Comments

Dan Rosenberg - Oct. 1, 2010, 9:51 p.m.
The sctp_asoc_get_hmac() function iterates through a peer's hmac_ids
array and attempts to ensure that only a supported hmac entry is
returned.  The current code fails to do this properly - if the last id
in the array is out of range (greater than SCTP_AUTH_HMAC_ID_MAX), the
id integer remains set after exiting the loop, and the address of an
out-of-bounds entry will be returned and subsequently used in the parent
function, causing potentially ugly memory corruption.  This patch resets
the id integer to 0 on encountering an invalid id so that NULL will be
returned after finishing the loop if no valid ids are found.

Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>



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Vlad Yasevich - Oct. 1, 2010, 10:13 p.m.
On 10/01/2010 05:51 PM, Dan Rosenberg wrote:
> The sctp_asoc_get_hmac() function iterates through a peer's hmac_ids
> array and attempts to ensure that only a supported hmac entry is
> returned.  The current code fails to do this properly - if the last id
> in the array is out of range (greater than SCTP_AUTH_HMAC_ID_MAX), the
> id integer remains set after exiting the loop, and the address of an
> out-of-bounds entry will be returned and subsequently used in the parent
> function, causing potentially ugly memory corruption.  This patch resets
> the id integer to 0 on encountering an invalid id so that NULL will be
> returned after finishing the loop if no valid ids are found.
>
> Signed-off-by: Dan Rosenberg<drosenberg@vsecurity.com>

Good catch.

Acked-by: Vlad Yasevich <vladislav.yasevich@hp.com>

-vlad


>
> --- linux-2.6.35.5.orig/net/sctp/auth.c	2010-09-20 16:59:09.000000000 -0400
> +++ linux-2.6.35.5/net/sctp/auth.c	2010-10-01 16:48:58.000000000 -0400
> @@ -543,16 +543,20 @@ struct sctp_hmac *sctp_auth_asoc_get_hma
>   		id = ntohs(hmacs->hmac_ids[i]);
>
>   		/* Check the id is in the supported range */
> -		if (id>  SCTP_AUTH_HMAC_ID_MAX)
> +		if (id>  SCTP_AUTH_HMAC_ID_MAX) {
> +			id = 0;
>   			continue;
> +		}
>
>   		/* See is we support the id.  Supported IDs have name and
>   		 * length fields set, so that we can allocated and use
>   		 * them.  We can safely just check for name, for without the
>   		 * name, we can't allocate the TFM.
>   		 */
> -		if (!sctp_hmac_list[id].hmac_name)
> +		if (!sctp_hmac_list[id].hmac_name) {
> +			id = 0;
>   			continue;
> +		}
>
>   		break;
>   	}
>
>

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David Miller - Oct. 4, 2010, 5 a.m.
From: Vlad Yasevich <vladislav.yasevich@hp.com>
Date: Fri, 01 Oct 2010 18:13:34 -0400

> On 10/01/2010 05:51 PM, Dan Rosenberg wrote:
>> The sctp_asoc_get_hmac() function iterates through a peer's hmac_ids
>> array and attempts to ensure that only a supported hmac entry is
>> returned.  The current code fails to do this properly - if the last id
>> in the array is out of range (greater than SCTP_AUTH_HMAC_ID_MAX), the
>> id integer remains set after exiting the loop, and the address of an
>> out-of-bounds entry will be returned and subsequently used in the
>> parent
>> function, causing potentially ugly memory corruption.  This patch
>> resets
>> the id integer to 0 on encountering an invalid id so that NULL will be
>> returned after finishing the loop if no valid ids are found.
>>
>> Signed-off-by: Dan Rosenberg<drosenberg@vsecurity.com>
> 
> Good catch.
> 
> Acked-by: Vlad Yasevich <vladislav.yasevich@hp.com>

Applied.
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Patch

--- linux-2.6.35.5.orig/net/sctp/auth.c	2010-09-20 16:59:09.000000000 -0400
+++ linux-2.6.35.5/net/sctp/auth.c	2010-10-01 16:48:58.000000000 -0400
@@ -543,16 +543,20 @@  struct sctp_hmac *sctp_auth_asoc_get_hma
 		id = ntohs(hmacs->hmac_ids[i]);
 
 		/* Check the id is in the supported range */
-		if (id > SCTP_AUTH_HMAC_ID_MAX)
+		if (id > SCTP_AUTH_HMAC_ID_MAX) {
+			id = 0;
 			continue;
+		}
 
 		/* See is we support the id.  Supported IDs have name and
 		 * length fields set, so that we can allocated and use
 		 * them.  We can safely just check for name, for without the
 		 * name, we can't allocate the TFM.
 		 */
-		if (!sctp_hmac_list[id].hmac_name)
+		if (!sctp_hmac_list[id].hmac_name) {
+			id = 0;
 			continue;
+		}
 
 		break;
 	}