[PATCH xauth] Look for FamilyLocal if inet or inet6 address is loopback

[Egbert Eich]

On Tue, Jul 30, 2013 at 11:01:02AM +0200, Egbert Eich wrote:
> libxcb uses FamilyLocal authorization if the host name or IP in the
> display string is from the loopback device. This patch adds the same
> behavior to xauth.
> This fixes a long standing problem that for ssh tunneled connections
> a display variable of the form: localhost:<N>.<M> leads to correct
> authorization when an X client is started but "xauth list $DISPLAY"
> returns nothing.

Likewise, does anyone care to comment on this patch?
It will change the behavior of xauth slightly - it will more
closely match what libxcb does and therefore its results will
resemble how Xclients behave more closely.

Cheers,
	Egbert.

> 
> Signed-off-by: Egbert Eich <eich at freedesktop.org>
> ---
>  gethost.c | 40 +++++++++++++++++++++++++++++++++++-----
>  1 file changed, 35 insertions(+), 5 deletions(-)
> 
> diff --git a/gethost.c b/gethost.c
> index 10f6078..7c4b600 100644
> --- a/gethost.c
> +++ b/gethost.c
> @@ -224,16 +224,36 @@ struct addrlist *get_address_info (
>  	for (ai = firstai; ai != NULL; ai = ai->ai_next) {
>  	    struct addrlist *duplicate;
>  
> +	    len = 0;
>  	    if (ai->ai_family == AF_INET) {
>  		struct sockaddr_in *sin = (struct sockaddr_in *)ai->ai_addr;
>  		src = &(sin->sin_addr);
> -		len = sizeof(sin->sin_addr);
> -		family = FamilyInternet;
> +		if (*(in_addr_t *) src == htonl(INADDR_LOOPBACK)) {
> +		    family = FamilyLocal;
> +		    if (get_local_hostname (buf, sizeof buf)) {
> +			src = buf;
> +			len = strlen (buf);
> +		    } else
> +			src = NULL;
> +		} else {
> +		    len = sizeof(sin->sin_addr);
> +		    family = FamilyInternet;
> +		}
>  	    } else if (ai->ai_family == AF_INET6) {
>  		struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)ai->ai_addr;
>  		src = &(sin6->sin6_addr);
> -		len = sizeof(sin6->sin6_addr);
> -		family = FamilyInternet6;
> +		if (IN6_IS_ADDR_V4MAPPED((struct sockaddr_in6 *)src)
> +		    || IN6_IS_ADDR_LOOPBACK((struct sockaddr_in6 *)src)) {
> +		    family = FamilyLocal;
> +		    if (get_local_hostname (buf, sizeof buf)) {
> +			src = buf;
> +			len = strlen (buf);
> +		    } else
> +			src = NULL;
> +		} else {
> +		    len = sizeof(sin6->sin6_addr);
> +		    family = FamilyInternet6;
> +		}
>  	    }
>  
>  	    for(duplicate = retval; duplicate != NULL; duplicate = duplicate->next) {
> @@ -272,7 +292,17 @@ struct addrlist *get_address_info (
>  #else
>  	if (!get_inet_address (host, &hostinetaddr)) return NULL;
>  	src = (char *) &hostinetaddr;
> -	len = 4; /* sizeof inaddr.sin_addr, would fail on Cray */
> +	if (*(in_addr_t *) src == htonl(INADDR_LOOPBACK)) {
> +	    family = FamilyLocal;
> +	    if (get_local_hostname (buf, sizeof buf)) {
> +		src = buf;
> +		len = strlen (buf);
> +	    } else {
> +		len = 0;
> +		src = NULL;
> +	    }
> +	} else
> +	    len = 4; /* sizeof inaddr.sin_addr, would fail on Cray */
>  	break;
>  #endif /* IPv6 */
>  #else
> -- 
> 1.8.1.4