[Libguestfs] [PATCH] daemon: Rewrite prog_exists so it uses the actual PATH, not hard-coded list.

[Pino Toscano]

In data martedì 23 giugno 2015 14:34:18, Richard W.M. Jones ha scritto:
> ---
>  daemon/guestfsd.c | 37 +++++++++++++++++++++++--------------
>  1 file changed, 23 insertions(+), 14 deletions(-)
> 
> diff --git a/daemon/guestfsd.c b/daemon/guestfsd.c
> index 21b3600..c9cc8c5 100644
> --- a/daemon/guestfsd.c
> +++ b/daemon/guestfsd.c
> @@ -243,9 +243,6 @@ main (int argc, char *argv[])
>    /* Set up a basic environment.  After we are called by /init the
>     * environment is essentially empty.
>     * https://bugzilla.redhat.com/show_bug.cgi?id=502074#c5
> -   *
> -   * NOTE: if you change $PATH, you must also change 'prog_exists'
> -   * function below.
>     */
>    setenv ("PATH", "/sbin:/usr/sbin:/bin:/usr/bin", 1);
>    setenv ("SHELL", "/bin/sh", 1);
> @@ -1440,22 +1437,34 @@ mountable_to_string (const mountable_t *mountable)
>    }
>  }
>  
> -/* Check program exists and is executable on $PATH.  Actually, we
> - * just assume PATH contains the default entries (see main() above).
> - */
> +/* Check program exists and is executable on $PATH. */
>  int
>  prog_exists (const char *prog)
>  {
> -  static const char * const dirs[] =
> -    { "/sbin", "/usr/sbin", "/bin", "/usr/bin" };
> -  size_t i;
> -  char buf[1024];
> -
> -  for (i = 0; i < sizeof dirs / sizeof dirs[0]; ++i) {
> -    snprintf (buf, sizeof buf, "%s/%s", dirs[i], prog);
> -    if (access (buf, X_OK) == 0)
> +  const char *pathc = getenv ("PATH");
> +
> +  if (!pathc)
> +    return 0;
> +
> +  const char *elem;
> +  char *saveptr;
> +  size_t len = strlen (pathc) + 1;
> +  char path[len];
> +  strcpy (path, pathc);
> +
> +  elem = strtok_r (path, ":", &saveptr);
> +  while (elem) {
> +    size_t n = strlen (elem) + strlen (prog) + 2;
> +    char testprog[n];
> +
> +    snprintf (testprog, n, "%s/%s", elem, prog);
> +    if (access (testprog, X_OK) == 0)
>        return 1;
> +
> +    elem = strtok_r (NULL, ":", &saveptr);
>    }
> +
> +  /* Not found. */
>    return 0;
>  }

LGTM.

The only minor note, "strlen (prog)" could be cached outside the while
loop.

-- 
Pino Toscano