netdev - Re: [net v2] net/tls: fix corrupted data in recvmsg

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Message-ID: <cd2f4bfe-8fff-ddab-d271-08f0917a5b48@novek.ru>
Date:   Tue, 17 Nov 2020 00:45:11 +0000
From:   Vadim Fedorenko <vfedorenko@...ek.ru>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Boris Pismenny <borisp@...dia.com>,
        Aviad Yehezkel <aviadye@...dia.com>, netdev@...r.kernel.org
Subject: Re: [net v2] net/tls: fix corrupted data in recvmsg



On 17.11.2020 00:26, Jakub Kicinski wrote:
> On Sun, 15 Nov 2020 07:16:00 +0300 Vadim Fedorenko wrote:
>> If tcp socket has more data than Encrypted Handshake Message then
>> tls_sw_recvmsg will try to decrypt next record instead of returning
>> full control message to userspace as mentioned in comment. The next
>> message - usually Application Data - gets corrupted because it uses
>> zero copy for decryption that's why the data is not stored in skb
>> for next iteration. Revert check to not decrypt next record if
>> current is not Application Data.
>>
>> Fixes: 692d7b5d1f91 ("tls: Fix recvmsg() to be able to peek across multiple records")
>> Signed-off-by: Vadim Fedorenko <vfedorenko@...ek.ru>
>> ---
>>   net/tls/tls_sw.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
>> index 95ab5545..2fe9e2c 100644
>> --- a/net/tls/tls_sw.c
>> +++ b/net/tls/tls_sw.c
>> @@ -1913,7 +1913,7 @@ int tls_sw_recvmsg(struct sock *sk,
>>   			 * another message type
>>   			 */
>>   			msg->msg_flags |= MSG_EOR;
>> -			if (ctx->control != TLS_RECORD_TYPE_DATA)
>> +			if (control != TLS_RECORD_TYPE_DATA)
> Sorry I wasn't clear enough, should this be:
>
> 	if (ctx->control != control)
>
> ? Otherwise if we get a control record first and then data record
> the code will collapse them, which isn't correct, right?
>
>>   				goto recv_end;
>>   		} else {
>>   			break;
I think you mean when ctx->control is control record and control is
data record. In this case control message will be decrypted without
zero copy and will be stored in skb for the next recvmsg, but will
not be returned together with data message. This behavior is the same
as for TLSv1.3 when record type is known only after decrypting.
But if we want completely different flow for TLSv1.2 and TLSv1.3
then changing to check difference in message types makes sense.