[Dnsmasq-discuss] spaces in hostnames

[Jim Alles]

Simon, Sir:

in 2007 @
https://www.mail-archive.com/dnsmasq-discuss%40lists.thekelleys.org.uk/msg01532.html

you said:

"Hmm, an interesting can of worms. My first reaction to this was "it's

not a problem, spaces are not legal in hostnames and should never get
there", but when I looked at the code, two things are apparent.

1) Hostnames in --dhcp-host lines are not ever checked for legality:
that's a bug. They are checked elsewhere (/etc/ethers, /etc/hosts, DHCP
client supplied names....)

2) The "is this hostname legal" checker actually allows spaces. This was
a change made to allow SRV records for DNS-SD, which have to have
spaces. The implications for the DHCP lease system were missed.

My inclination is to re-impose the ban on spaces on DHCP hostnames.
Richard, would that cause you problems? Presumably you have at least one
name with a space in it, is that "real" or from an all-possibilites test?

If spaces in hostnames are to be allowed, they should be escaped somehow.
​"


May I ask ​what the resolution of this issue was? I see no reference
in recent changelogs.


And methinks the GUI of a router that I use should have an input
validation to prevent spaces from being entered.


Is there a list or reference to legal hostname characters in an
"addn-hosts=" file for dnsmasq.conf?


My gratitude to you for being here!


Jim Alles

[Simon Kelley]

Post by Jim Alles
https://www.mail-archive.com/dnsmasq-discuss%40lists.thekelleys.org.uk/msg01532.html
"Hmm, an interesting can of worms. My first reaction to this was "it's
not a problem, spaces are not legal in hostnames and should never get
there", but when I looked at the code, two things are apparent.
that's a bug. They are checked elsewhere (/etc/ethers, /etc/hosts, DHCP
client supplied names....)
2) The "is this hostname legal" checker actually allows spaces. This was
a change made to allow SRV records for DNS-SD, which have to have
spaces. The implications for the DHCP lease system were missed.
My inclination is to re-impose the ban on spaces on DHCP hostnames.
Richard, would that cause you problems? Presumably you have at least one
name with a space in it, is that "real" or from an all-possibilites test?
If spaces in hostnames are to be allowed, they should be escaped somehow.
​"
May I ask ​what the resolution of this issue was? I see no reference
in recent changelogs.
And methinks the GUI of a router that I use should have an input
validation to prevent spaces from being entered.
My gratitude to you for being here!
Jim Alles

/* Hostnames have a more limited valid charset than domain names
so check for legal char a-z A-Z 0-9 - _


It's all a very long time ago, but we ended up making the correct
distinction between _hostnames_ and _domain_names_

For dhcp-host, the check is for a legal hostname, which is

a-z A-Z 0-9 - _

for names in /etc/hosts and friends, they're domain names, and anything
other then control characters are allowed. If dnsmasq is compiled with
the internationalised domain name support, then the check is done by the
IDN library, so it's whatever GNU libidn allows.



Cheers,

Simon.