[PATCH xserver] os: Treat ssh as a non-local client (v2)

[Mark Kettenis]

> From: =?UTF-8?q?Michel=20D=C3=A4nzer?= <michel at daenzer.net>
> Date: Fri, 11 Dec 2015 11:28:51 +0900
> 
> By the time we get to ComputeLocalClient, we've already done
> NextAvailableClient → ReserveClientIds →
> DetermineClientCmd (assuming we're built with #define CLIENTIDS), so
> we can look up the name of the client process and refuse to treat
> ssh's X forwarding as if it were local.
> 
> v2: (Michel Dänzer)
>     * Only match "ssh" itself, not other executable names starting with
>       that prefix.
>     * Ignore executable path for the match.
> 
> Signed-off-by: Adam Jackson <ajax at redhat.com>
> Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>
> ---
>  os/access.c | 27 ++++++++++++++++++++++++---
>  1 file changed, 24 insertions(+), 3 deletions(-)
> 
> diff --git a/os/access.c b/os/access.c
> index 10a48c3..6ff6977 100644
> --- a/os/access.c
> +++ b/os/access.c
> @@ -101,6 +101,7 @@ SOFTWARE.
>  #include <sys/socket.h>
>  #include <sys/ioctl.h>
>  #include <ctype.h>
> +#include <libgen.h>
>  
>  #ifndef NO_LOCAL_CLIENT_CRED
>  #include <pwd.h>
> @@ -1081,9 +1082,8 @@ ResetHosts(const char *display)
>      }
>  }
>  
> -/* Is client on the local host */
> -Bool
> -ComputeLocalClient(ClientPtr client)
> +static Bool
> +xtransLocalClient(ClientPtr client)
>  {
>      int alen, family, notused;
>      Xtransaddr *from = NULL;
> @@ -1116,6 +1116,27 @@ ComputeLocalClient(ClientPtr client)
>      return FALSE;
>  }
>  
> +/* Is client on the local host */
> +Bool
> +ComputeLocalClient(ClientPtr client)
> +{
> +    if (!xtransLocalClient(client))
> +        return FALSE;
> +
> +#ifndef WIN32
> +    /* If the executable name is "ssh", consider this client not local */
> +    if (client->clientIds->cmdname) {

Isn't it better to use GetClientCmdName() here to keep avoid a
potential null-pointer dereference?  Actually include/client.h tells
you you shuld ;).