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[204.195.112.199]) by smtp.gmail.com with ESMTPSA id h27-20020aa79f5b000000b0051c79bd5047sm1848328pfr.139.2022.06.24.08.06.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Jun 2022 08:06:09 -0700 (PDT) Date: Fri, 24 Jun 2022 08:06:06 -0700 From: Stephen Hemminger <stephen@networkplumber.org> To: Morten =?UTF-8?B?QnLDuHJ1cA==?= <mb@smartsharesystems.com> Cc: "Bruce Richardson" <bruce.richardson@intel.com>, <dev@dpdk.org>, <ciara.power@intel.com>, <fengchengwen@huawei.com> Subject: Re: [RFC PATCH 2/6] telemetry: fix escaping of invalid json characters Message-ID: <20220624080606.66ca25dd@hermes.local> In-Reply-To: <98CBD80474FA8B44BF855DF32C47DC35D87174@smartserver.smartshare.dk> References: <20220623164245.561371-1-bruce.richardson@intel.com> <20220623164245.561371-3-bruce.richardson@intel.com> <98CBD80474FA8B44BF855DF32C47DC35D8716B@smartserver.smartshare.dk> <20220623113934.372b059e@hermes.local> <98CBD80474FA8B44BF855DF32C47DC35D8716C@smartserver.smartshare.dk> <YrVvJpDMGpCxu8J6@bricha3-MOBL.ger.corp.intel.com> <YrWdGYgO1GJU+0yl@bricha3-MOBL.ger.corp.intel.com> <98CBD80474FA8B44BF855DF32C47DC35D87174@smartserver.smartshare.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions <dev.dpdk.org> List-Unsubscribe: <https://mails.dpdk.org/options/dev>, <mailto:dev-request@dpdk.org?subject=unsubscribe> List-Archive: <http://mails.dpdk.org/archives/dev/> List-Post: <mailto:dev@dpdk.org> List-Help: <mailto:dev-request@dpdk.org?subject=help> List-Subscribe: <https://mails.dpdk.org/listinfo/dev>, <mailto:dev-request@dpdk.org?subject=subscribe> Errors-To: dev-bounces@dpdk.org On Fri, 24 Jun 2022 13:29:46 +0200 Morten Br=C3=B8rup <mb@smartsharesystems.com> wrote: > > From: Bruce Richardson [mailto:bruce.richardson@intel.com] > > Sent: Friday, 24 June 2022 13.17 > >=20 > > On Fri, Jun 24, 2022 at 09:00:38AM +0100, Bruce Richardson wrote: =20 > > > On Thu, Jun 23, 2022 at 08:48:21PM +0200, Morten Br=C3=B8rup wrote: = =20 > > > > > From: Stephen Hemminger [mailto:stephen@networkplumber.org] > > > > > Sent: Thursday, 23 June 2022 20.40 > > > > > > > > > > On Thu, 23 Jun 2022 20:34:07 +0200 > > > > > Morten Br=C3=B8rup <mb@smartsharesystems.com> wrote: > > > > > =20 > > > > > > > From: Bruce Richardson [mailto:bruce.richardson@intel.com] > > > > > > > Sent: Thursday, 23 June 2022 18.43 > > > > > > > > > > > > > > For string values returned from telemetry, escape any values = =20 > > that =20 > > > > > > > cannot > > > > > > > normally appear in a json string. According to the json =20 > > spec[1], =20 > > > > > the =20 > > > > > > > characters than need to be handled are control chars (char =20 > > value < =20 > > > > > > > 0x20) > > > > > > > and '"' and '\' characters. =20 > > > > > > > > > > > > Correct. Other chars are optional to escape. =20 > > > > > > > > > > For json_writer (which I wrote for iproute2 and could have been = =20 > > used =20 > > > > > here). > > > > > The switch handles: \t \n \r \f \b \\ " ' as special cases. =20 > > > > > > > > RFC 8259 chapter 7 says: > > > > > > > > All Unicode characters may be placed within the > > > > quotation marks, except for the characters that MUST be escaped: > > > > quotation mark, reverse solidus, and the control characters =20 > > (U+0000 =20 > > > > through U+001F). > > > > > > > > I have no preference for either, as long as '/' and other non- =20 > > control characters are not (unnecessarily) escaped. =20 > > > > > > > > Using tested and maintained code like json_writer could be =20 > > beneficial. If you hold the copyright, there should be no license > > issues. =20 > > > > =20 > > > > > > I will take a look at json_writer. =20 > >=20 > > Took a quick look at json_writer, and it's certainly an option. The > > main > > gap compared to what we have in our current implementation is that > > json_writer is designed around a stream for output rather than an > > output > > buffer. Now while we can use fmemopen to make our buffer act as a > > stream > > for writing, and the write apis should prevent it overflowing, we still > > hit > > the issue of the result of truncation not being valid json. The current > > implementation tries to handle truncation more gracefully in that any > > fields which don't fit just don't get added. > >=20 > > I'll think about it a bit more, and see if there is a way that it can > > be > > made to work more cleanly. =20 >=20 > It sounds like json_writer provides a more advanced API, adding a lot of = overhead for wrapping it into the Telemetry library. Since we only need a v= ery simple encoder, perhaps copy-paste-modify is more viable. Or just proce= ed with your RFC code. >=20 > Regardless, the API and underlying code probably needs extra scrutiny, so= it doesn't become an attack vector into the control plane of a DPDK applic= ation. I wrote it based on the model used by some Java library. Other JSON libraries were more concerned with parsing JSON.