[Libguestfs] [PATCH 2/2] launch: Validate $TERM before passing it through to the kernel command line.

[Pino Toscano]

On Sunday, 18 December 2016 20:09:29 CET Richard W.M. Jones wrote:
> Make sure it is reasonable before we pass it through to the kernel
> command line.  I don't believe this is exploitable, but it might cause
> obscure bugs.
> ---
>  src/launch.c | 26 +++++++++++++++++++++++++-
>  1 file changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/src/launch.c b/src/launch.c
> index 84d5e82..ee2a23d 100644
> --- a/src/launch.c
> +++ b/src/launch.c
> @@ -39,6 +39,8 @@
>  #include <assert.h>
>  #include <libintl.h>
>  
> +#include "c-ctype.h"
> +
>  #include "guestfs.h"
>  #include "guestfs-internal.h"
>  #include "guestfs-internal-actions.h"
> @@ -284,6 +286,28 @@ guestfs_impl_config (guestfs_h *g,
>    return 0;
>  }
>  
> +/**
> + * Check that the $TERM environment variable is reasonable before
> + * we pass it through to the appliance.
> + */
> +static int
> +valid_term (const char *term)

I guess the return value can be bool.

> +{
> +  size_t len = strlen (term);
> +
> +  if (len == 0 || len > 16)
> +    return 0;
> +
> +  while (len > 0) {
> +    char c = *term++;
> +    len--;
> +    if (!c_isalnum (c) && c != '-' && c != '_')
> +      return 0;
> +  }

The loop is fine already, maybe the need to use len can be dropped:

  for (; *term; ++term) {
    char c = *term;
    if (!c_isalnum (c) && c != '-' && c != '_')
      return 0;
  }

Thanks,
-- 
Pino Toscano
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