Re: [PATCH v2] net/sctp: Make sha1 as default algorithm if fips is enabled

[Ashwin Dayanand Kamat]

> On 27-May-2023, at 7:43 PM, Simon Horman <simon.horman@xxxxxxxxxxxx> wrote:
> 
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> 
> On Sat, May 27, 2023 at 07:49:26AM +0000, Ashwin Dayanand Kamat wrote:
>> 
>> 
>>> On 25-Mar-2023, at 12:03 PM, Ashwin Dayanand Kamat <kashwindayan@xxxxxxxxxx> wrote:
>>> 
>>> 
>>>> On 23-Mar-2023, at 2:16 AM, Simon Horman <simon.horman@xxxxxxxxxxxx> wrote:
>>>> 
>>>> !! External Email
>>>> 
>>>> On Wed, Mar 22, 2023 at 07:34:40PM +0530, Ashwin Dayanand Kamat wrote:
>>>>> MD5 is not FIPS compliant. But still md5 was used as the default
>>>>> algorithm for sctp if fips was enabled.
>>>>> Due to this, listen() system call in ltp tests was failing for sctp
>>>>> in fips environment, with below error message.
>>>>> 
>>>>> [ 6397.892677] sctp: failed to load transform for md5: -2
>>>>> 
>>>>> Fix is to not assign md5 as default algorithm for sctp
>>>>> if fips_enabled is true. Instead make sha1 as default algorithm.
>>>>> 
>>>>> Fixes: ltp testcase failure "cve-2018-5803 sctp_big_chunk"
>>>>> Signed-off-by: Ashwin Dayanand Kamat <kashwindayan@xxxxxxxxxx>
>>>>> ---
>>>>> v2:
>>>>> the listener can still fail if fips mode is enabled after
>>>>> that the netns is initialized. So taking action in sctp_listen_start()
>>>>> and buming a ratelimited notice the selected hmac is changed due to fips.
>>>>> ---
>>>>> net/sctp/socket.c | 10 ++++++++++
>>>>> 1 file changed, 10 insertions(+)
>>>>> 
>>>>> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
>>>>> index b91616f819de..a1107f42869e 100644
>>>>> --- a/net/sctp/socket.c
>>>>> +++ b/net/sctp/socket.c
>>>>> @@ -49,6 +49,7 @@
>>>>> #include <linux/poll.h>
>>>>> #include <linux/init.h>
>>>>> #include <linux/slab.h>
>>>>> +#include <linux/fips.h>
>>>>> #include <linux/file.h>
>>>>> #include <linux/compat.h>
>>>>> #include <linux/rhashtable.h>
>>>>> @@ -8496,6 +8497,15 @@ static int sctp_listen_start(struct sock *sk, int backlog)
>>>>> struct crypto_shash *tfm = NULL;
>>>>> char alg[32];
>>>>> 
>>>>> + if (fips_enabled && !strcmp(sp->sctp_hmac_alg, "md5")) {
>>>>> +#if (IS_ENABLED(CONFIG_SCTP_DEFAULT_COOKIE_HMAC_SHA1))
>>>> 
>>>> I'm probably misunderstanding things, but would
>>>> IS_ENABLED(CONFIG_SCTP_COOKIE_HMAC_SHA1)
>>>> be more appropriate here?
>>>> 
>>> 
>>> Hi Simon,
>>> I have moved the same check from sctp_init() to here based on the review for v1 patch.
>>> Please let me know if there is any alternative which can be used?
>>> 
>>> Thanks,
>>> Ashwin Kamat
>>> 
>> Hi Team,
>> Any update on this?
> 
> Hi Ashwin,
> 
> I don't recall exactly what I was thinking 2 months ago.
> But looking at this a second time it seems that I may have misread your
> patch: I now have no objections to it in its original form.
Thanks Simon.
I have Updated the v3 patch with some minor changes.  Please review the same.

> 
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