[PATCH 1/2] udhcpd: sanitize invalid hostnames to match rfcs

[walter harms]

Am 18.10.2015 07:54, schrieb Isaac Dunham:
> RFC952/RFC1123 limit the characters in a hostname for a node to
> [-a-zA-Z0-9], with '-' being legal only in the middle; we were
> accepting everything from ' ' to '~'.
> (As a byproduct of this, the hostname in dumpleases can now be safely
> used from scripts without sanitization.)
> 
> function                                             old     new   delta
> add_lease                                            326     363     +37
> ------------------------------------------------------------------------------
> (add/remove: 0/0 grow/shrink: 1/0 up/down: 37/0)               Total: 37 bytes
>    text	   data	    bss	    dec	    hex	filename
>  892983	   6844	   7288	 907115	  dd76b	busybox_old
>  893020	   6844	   7288	 907152	  dd790	busybox_unstripped
> ---
>  networking/udhcp/leases.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/networking/udhcp/leases.c b/networking/udhcp/leases.c
> index 745340a..1f7af87 100644
> --- a/networking/udhcp/leases.c
> +++ b/networking/udhcp/leases.c
> @@ -65,12 +65,19 @@ struct dyn_lease* FAST_FUNC add_lease(
>  			if (hostname_len > sizeof(oldest->hostname))
>  				hostname_len = sizeof(oldest->hostname);
>  			p = safe_strncpy(oldest->hostname, hostname, hostname_len);
> -			/* sanitization (s/non-ASCII/^/g) */
> +			/* sanitization - per rfcs 952 & 1123 only [-a-zA-Z0-9] are legal
> +			 * with '-' being allowed only in the middle
> +			 */
>  			while (*p) {
> -				if (*p < ' ' || *p > 126)
> -					*p = '^';
> +				if (! (isupper((char)*p) || islower((char)*p) ||
> +						isdigit((char)*p) || (char)*p == '-') )
> +					*p = '-';
>  				p++;
>  			}
> +			if (p--, *p == '-')
> +				*p = 'X';
> +			if (p = oldest->hostname, *p == '-')
> +				*p = 'X';
>  		}
>  		if (chaddr)
>  			memcpy(oldest->lease_mac, chaddr, 6);

since several tools check for hostnames,
maybe it is useful to make this a function ?

re,
 wh