[PATCH v2 1/5] telemetry: escape special char when tel string

[Stephen Hemminger]

On Fri, 17 Jun 2022 12:25:04 +0100
Bruce Richardson <bruce.richardson at intel.com> wrote:

> On Fri, Jun 17, 2022 at 01:16:08PM +0200, Morten Brørup wrote:
> > > From: Chengwen Feng [mailto:fengchengwen at huawei.com]
> > > Sent: Friday, 17 June 2022 11.46
> > > 
> > > This patch supports escape special characters (including: \",\\,/,\b,
> > > /f,/n,/r,/t) when telemetry string.
> > > This patch is used to support telemetry xxx-dump commands which the
> > > string may include special characters.
> > > 
> > > Signed-off-by: Chengwen Feng <fengchengwen at huawei.com>
> > > ---
> > >  lib/telemetry/telemetry.c | 96 +++++++++++++++++++++++++++++++++++++--
> > >  1 file changed, 93 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/lib/telemetry/telemetry.c b/lib/telemetry/telemetry.c
> > > index c6fd03a5ab..0f762f633e 100644
> > > --- a/lib/telemetry/telemetry.c
> > > +++ b/lib/telemetry/telemetry.c
> > > @@ -215,6 +215,94 @@ container_to_json(const struct rte_tel_data *d,
> > > char *out_buf, size_t buf_len)
> > >  	return used;
> > >  }
> > > 
> > > +static bool
> > > +json_is_special_char(char ch)
> > > +{
> > > +	static unsigned char is_spec[256] = { 0 };
> > > +	static bool init_once;
> > > +
> > > +	if (!init_once) {
> > > +		is_spec['\"'] = 1;
> > > +		is_spec['\\'] = 1;
> > > +		is_spec['/'] = 1;
> > > +		is_spec['\b'] = 1;
> > > +		is_spec['\f'] = 1;
> > > +		is_spec['\n'] = 1;
> > > +		is_spec['\r'] = 1;
> > > +		is_spec['\t'] = 1;
> > > +		init_once = true;
> > > +	}
> > > +
> > > +	return (bool)is_spec[(unsigned char)ch];
> > > +}  
> 
> According to the json spec at [1], the characters that need to be escaped
> are:
> a) any characters <0x20
> b) inverted commas/quote character \"
> c) the "reverse solidus character", better known to you and I as the
> back-slash.
> 
> Therefore, I think this table generation could be simplified, but also
> expanded using this. For completeness we should also see about handling all
> control characters if they are encountered.
> 
> [1] https://www.rfc-editor.org/rfc/rfc8259.txt
> 
> /Bruce

Since it is trivial could be initializer?

static const uint8_t is_spec[256] = {
   [0 ... 0x20] = 1,
   ['\"' ] = 1,
   ['\\' ] = 1,
   ['/'] = 1,

etc

Or we could change the telemetry API to disallow control characters?