[PATCH v2] Ntpd config file support

[Isaac Dunham]

On Sat, Mar 22, 2014 at 08:40:48PM +0100, Harald Becker wrote:
> Hi Isaac !
> 
> Your program will fail on lines starting with the word server
> (eg. serverxyz), that is it does not check for clear word
> boundary and gives wrong results in that case.

...which are not legitimate entries in ntp.conf.

My aim is to parse a correct ntp.conf, and not cause security problems
on incorrect ones.

> >while (cbuf[i] > 35) i++;
> 
> Unwise to do this in a not poor ASCII environment, as most
> systems are nowadays. This way you allow unprintable and any
> kind of illegal characters in time server addresses. 
Fixing. 
The fix expects chars exclusively in the set [-.:0-9a-zA-Z], which all 
valid hostnames and IP addresses (ipv4/ipv6) have.

>... and what
> about buffer overflow? Won't this loop then run to unknown
> locations?

Not possible. i is size_t, and getline() is _always_ \0 terminated.
However, the previous loop did have a potential buffer overrun if the
line ended prematurely:
server \n\0 would result in it walking over the end and writing 0 to the
first character less than 36 after a sequence of chars greater than
35 ('#')...

> Beside this: Make it a default NO configuration, not being
> included in binaries build from standard options.

OK. 
(Denys gets the final say on that, though.)

Here's a version that has the issues mentioned fixed, and removes the 10
byte overhead.
It accepts "peer" as well as "server", and runs 320 bytes.


Thanks,
Isaac Dunham
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