Haven't seen a PR, so went ahead and implemented as discussed:
https://github.com/c-ares/c-ares/commit/d0f7d5ee
On 3/12/18 9:23 AM, Francisco Sedano Crippa (fsedanoc) wrote:
>
> Hi folks.
>
> Yes, ares_set_servers_csv() returned what it should. It’s just the behavior afterwards which is not correct. I’ll
> submit PR for adding this check, thanks.
>
> *. .:|:.:|:. _Francisco Sedano_ | CCIE 14859, Tech Lead Software Engineering | CSG Enterprise Access and Services
> Group (EASG)*
>
> *From: *c-ares <c-ares-bounces_at_cool.haxx.se> on behalf of David Drysdale <drysdale_at_google.com>
> *Reply-To: *c-ares hacking <c-ares_at_cool.haxx.se>
> *Date: *Sunday, 11 March 2018 at 08:29
> *To: *c-ares hacking <c-ares_at_cool.haxx.se>
> *Subject: *Re: Wrong handling on badly formatted strings passed to set_servers_csv
>
> On Sat, Mar 10, 2018 at 1:03 PM, Brad House <brad_at_mainstreetsoftworks.com<mailto:brad_at_mainstreetsoftworks.com>> wrote:
>
> Did ares_set_servers_csv() return ARES_EBADSTR as it should?
>
> There's a test that implies that it will: https://github.com/c-ares/c-ares/blob/master/test/ares-test-misc.cc#L86-L88
>
> It does appear when it does that, it leaves the channel in a "bad" state since existing servers are cleared before
> parse. I'm not sure of any other instances where a channel might have no servers, as even in the case where it
> can't determine one from configuration, it uses a localhost fallback. It may make more sense to kill the
> ares__destroy_servers_state() call at the beginning of set_servers_csv(), since ares_set_servers_ports() clears
> it which gets called after a successful parse.
>
> I'd agree that there should probably be a sanity check in ares_send() to not try an invalid ares_malloc(),
> ARES_ESERVFAIL would be as good an error condition as any in this case.
>
> +1
>
>
> -Brad
>
> On 3/9/18 7:07 PM, Francisco Sedano Crippa (fsedanoc) wrote:
>
> Hello,
>
> I noticed today if you pass a string with spaces to set_servers_csv, like:
>
> "127.0.0.1 , 200.0.0.1"
>
> It will take the first server as "127.0.0.1 " (note the space), it will notice it's not a valid IP and fail.
> So far so good.
>
> However, nservers for the channel will stay set to -1, so when ares_send is called, this will be executed:
>
> query->server_info = ares_malloc(channel->nservers *
> sizeof(query->server_info[0]));
>
> The negative value will be misinterpreted to a huge number since argument is size_t and we agree things smell
> really bad from here. In practice, such a mem allocation fails and we return ENOMEM (which is also
> misleading), but it's a very incorrect behaviour.
>
> I was thinking on just adding a check at the beginning of ares_send() to exit if nservers is <= 0.
>
> Do you guys agree with the approach? If that’s the case, which error do you suggest to return? No one really
> matches, I’d say ARES_ENOTFOUND, but that implies we tried to contact the server…
>
> Thanks!
>
> *. .:|:.:|:. _Francisco Sedano_ | CCIE 14859, Tech Lead Software Engineering | CSG Enterprise Access
> and Services Group (EASG)*
>
Received on 2018-03-15