Fwd: [PATCH] Audit: fix handling of 'strings' with NULL characters

[Miloslav Trmac]

Hello,
this appears to have been lost somewhere...
    Mirek
> --- Begin Message ---
> currently audit_log_n_untrustedstring() uses
> audit_string_contains_control() to check if the 'string' has any control
> characters.  If the 'string' has an embedded NULL
> audit_string_contains_control() will return that the data has no control
> characters and will then pass the string to audit_log_n_string with the
> total length, not the length up to the first NULL.  audit_log_n_string
> does a memcpy of the entire length and so the actual audit record
> emitted may then contain a NULL and then whatever random memory is after
> the NULL.
>
> Since we want to log the entire octet stream (if we can't trust the data
> to be a string we can't trust that a NULL isn't actually a part of it)
> we should just consider NULL as a control character.  If the caller is
> certain they want to stop at the first NULL they should be using
> audit_log_untrustedstring.
>
> Signed-off-by: Eric Paris <eparis@xxxxxxxxxx>
>
> ---
>
> Miloslav, this is also going to take care of nulls in the TTY_AUDIT_USER
> message from userspace.  Is it going to be common to have control
> characters on that code path as well?  Do you want to change
> audit_receive_msg() to also use the hex encoding directly instead of the
> _n_untrustedstring interface?
>
>  kernel/audit.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/audit.c b/kernel/audit.c
> index 4414e93..ccb8d68 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -1370,7 +1370,7 @@ void audit_log_n_string(struct audit_buffer *ab, const char *string,
>  int audit_string_contains_control(const char *string, size_t len)
>  {
>  	const unsigned char *p;
> -	for (p = string; p < (const unsigned char *)string + len && *p; p++) {
> +	for (p = string; p < (const unsigned char *)string + len; p++) {
>  		if (*p == '"' || *p < 0x21 || *p > 0x7e)
>  			return 1;
>  	}
>
>
>
> --- End Message ---