Re: Compare Hex to Decimal

[jpotter-varnish]

Hi Michael,

I did something similar to this several years back using inline C:
https://varnish-cache.org/docs/5.1/users-guide/vcl-inline-c.html 


I’m super-rusty on my C, so ask better minds, but I’d start by doing the if 
check in C and leaving the rest of the logic in VCL. I.e.
strtol() with a base of 16 (see 
http://pubs.opengroup.org/onlinepubs/7908799/xsh/strtol.html 
) and then a 
direct check of that against gmtime() - delta (hopefully your unix hex 
timestamps in UTC?). Double-check the input to strtol is safe — this approach 
has untrusted inputs getting run through into C.

-Jeff

> On Apr 13, 2018, at 11:42 AM, Michael Kennedy  wrote:
> 
> Hi,
> 
> I have a URL that contains a Unix hex timestamp (something like 5ace8c5d). 
> The timestamp should be within X minutes of now, and is used as part of an 
> access control mechanism. I want to do something like this:
> 
> if (std.time(req.http.x-hextime, now) < now - 1w) {
> ...
> }
> 
> Is there an efficient way in VCL to either convert Hex to Dec so that this 
> comparison can be done, or some other solution that does not involve changing 
> the data in the URL.
> 
> Thanks,
> 
> Michael
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Compare Hex to Decimal

[Michael Kennedy]

Hi,


I have a URL that contains a Unix hex timestamp (something like 5ace8c5d). The 
timestamp should be within X minutes of now, and is used as part of an access 
control mechanism. I want to do something like this:


if (std.time(req.http.x-hextime, now) < now - 1w) {
...
}

Is there an efficient way in VCL to either convert Hex to Dec so that this 
comparison can be done, or some other solution that does not involve changing 
the data in the URL.

Thanks,

Michael
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