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Date: Wed, 21 Mar 2018 07:20:55 +0200
From: Boris Pismenny <borisp@...lanox.com>
To: Dave Watson <davejwatson@...com>,
"David S. Miller" <davem@...emloft.net>,
Tom Herbert <tom@...ntonium.net>,
Alexei Starovoitov <alexei.starovoitov@...il.com>,
herbert@...dor.apana.org.au, linux-crypto@...r.kernel.org,
netdev@...r.kernel.org
Cc: Atul Gupta <atul.gupta@...lsio.com>,
Vakul Garg <vakul.garg@....com>,
Hannes Frederic Sowa <hannes@...essinduktion.org>,
Steffen Klassert <steffen.klassert@...unet.com>,
John Fastabend <john.fastabend@...il.com>,
Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH net-next 5/6] tls: RX path for ktls
On 3/20/2018 7:54 PM, Dave Watson wrote:
> Add rx path for tls software implementation.
>
> recvmsg, splice_read, and poll implemented.
>
> An additional sockopt TLS_RX is added, with the same interface as
> TLS_TX. Either TLX_RX or TLX_TX may be provided separately, or
> together (with two different setsockopt calls with appropriate keys).
>
> Control messages are passed via CMSG in a similar way to transmit.
> If no cmsg buffer is passed, then only application data records
> will be passed to userspace, and EIO is returned for other types of
> alerts.
>
> EBADMSG is passed for decryption errors, and EMSGSIZE is passed for
> framing errors (either framing too big *or* too small with crypto
> overhead). EINVAL is returned for TLS versions that do not match the
> original setsockopt call. All are unrecoverable.
>
> strparser is used to parse TLS framing. Decryption is done directly
> in to userspace buffers if they are large enough to support it, otherwise
> sk_cow_data is called (similar to ipsec), and buffers are decrypted in
> place and copied. splice_read always decrypts in place, since no
> buffers are provided to decrypt in to.
>
> sk_poll is overridden, and only returns POLLIN if a full TLS message is
> received. Otherwise we wait for strparser to finish reading a full frame.
> Actual decryption is only done during recvmsg or splice_read calls.
>
> Signed-off-by: Dave Watson <davejwatson@...com>
> ---
...
> +
> +static int tls_read_size(struct strparser *strp, struct sk_buff *skb)
> +{
> + struct tls_context *tls_ctx = tls_get_ctx(strp->sk);
> + struct tls_sw_context *ctx = tls_sw_ctx(tls_ctx);
> + char header[tls_ctx->rx.prepend_size];
> + struct strp_msg *rxm = strp_msg(skb);
> + size_t cipher_overhead;
> + size_t data_len = 0;
> + int ret;
> +
> + /* Verify that we have a full TLS header, or wait for more data */
> + if (rxm->offset + tls_ctx->rx.prepend_size > skb->len)
> + return 0;
> +
> + /* Linearize header to local buffer */
> + ret = skb_copy_bits(skb, rxm->offset, header, tls_ctx->rx.prepend_size);
> +
> + if (ret < 0)
> + goto read_failure;
> +
> + ctx->control = header[0];
> +
> + data_len = ((header[4] & 0xFF) | (header[3] << 8));
> +
> + cipher_overhead = tls_ctx->rx.tag_size + tls_ctx->rx.iv_size;
> +
> + if (data_len > TLS_MAX_PAYLOAD_SIZE + cipher_overhead) {
> + ret = -EMSGSIZE;
> + goto read_failure;
> + }
> + if (data_len < cipher_overhead) {
> + ret = -EMSGSIZE;
I think this should be considered EBADMSG, because this error is cipher
dependent. At least, that's what happens within OpenSSL. Also, EMSGSIZE
is usually used only for too long messages.
> + goto read_failure;
> + }
> +
> + if (header[1] != TLS_VERSION_MINOR(tls_ctx->crypto_recv.version) ||
> + header[2] != TLS_VERSION_MAJOR(tls_ctx->crypto_recv.version)) {
> + ret = -EINVAL;
> + goto read_failure;
> + }
> +
> + return data_len + TLS_HEADER_SIZE;
> +
> +read_failure:
> + tls_err_abort(strp->sk, ret);
> +
> + return ret;
> +}
> +
...
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