On mercoledì 20 aprile 2022 14:23:28 CEST Rebecca Mckeever wrote:
> Currently, these three get_key functions return -1 when the provided len
> value is less a specific key length value, which can result in buffer
> overflow depending on how the returned value is used. These functions are
> used in three places in ieee80211/ieee80211_wx.c:
>
> ieee80211_wx_get_encode() :
> The behavior of this function will be unchanged.
>
> ieee80211_wx_get_encode_ext() :
> The result of the get_key function is written to ext->key_len,
> resulting in a buffer overflow if the result is negative.
>
> ieee80211_wx_set_encode() :
> The behavior of this function will change. When len is less than the
> key length value, it will set a default key of all 0.
>
> Suggested-by: Dan Carpenter <[email protected]>
> Signed-off-by: Rebecca Mckeever <[email protected]>
> ---
> drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_ccmp.c | 2 +-
> drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c | 2 +-
> drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_wep.c | 2 +-
> 3 files changed, 3 insertions(+), 3 deletions(-)
I was not able to find the message where Dan suggested this solution.
However it looks that we actually have problems in those callers when they
get '-1' as the return code.
I didn't look at the code with much attention but I think that returning
'0' to signal errors is not so good.
If I'm not missing something from the context, I'd rather return '-EINVAL'
and change the callers to check for this specific error that would signal
we have "len less than a specific len value". If so, act in accordance to
the returned -EINVAL.
For example, in a caller you may test:
if (ext->key_len == -EINVAL || <some other test, if required>)
<error path>
<success path>
Just my thoughts, but, as I said, I haven't checked carefully neither the
callers nor the called functions. Maybe that returning '0' is the better
solution, but it usually means that we have no errors.
However, I'm 100% sure that, if Dan suggested this specific solution, there
must be good reasons behind. If so, your changes are good :)
Thanks,
Fabio M. De Francesco
>
> diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_ccmp.c b/
drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_ccmp.c
> index 101c28265e91..f17d07dad56d 100644
> --- a/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_ccmp.c
> +++ b/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_ccmp.c
> @@ -362,7 +362,7 @@ static int ieee80211_ccmp_get_key(void *key, int len,
u8 *seq, void *priv)
> struct ieee80211_ccmp_data *data = priv;
>
> if (len < CCMP_TK_LEN)
> - return -1;
> + return 0;
>
> if (!data->key_set)
> return 0;
> diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c b/
drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c
> index 689d8843f538..7b120b8cb982 100644
> --- a/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c
> +++ b/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c
> @@ -637,7 +637,7 @@ static int ieee80211_tkip_get_key(void *key, int len,
u8 *seq, void *priv)
> struct ieee80211_tkip_data *tkey = priv;
>
> if (len < TKIP_KEY_LEN)
> - return -1;
> + return 0;
>
> if (!tkey->key_set)
> return 0;
> diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_wep.c b/
drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_wep.c
> index 8a51ea1dd6e5..a2cdf3bfd1a4 100644
> --- a/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_wep.c
> +++ b/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_wep.c
> @@ -201,7 +201,7 @@ static int prism2_wep_get_key(void *key, int len, u8
*seq, void *priv)
> struct prism2_wep_data *wep = priv;
>
> if (len < wep->key_len)
> - return -1;
> + return 0;
>
> memcpy(key, wep->key, wep->key_len);
>
> --
> 2.32.0
>
>
>
On Wed, Apr 20, 2022 at 04:52:36PM +0200, Fabio M. De Francesco wrote:
> On mercoled? 20 aprile 2022 14:23:28 CEST Rebecca Mckeever wrote:
> > Currently, these three get_key functions return -1 when the provided len
> > value is less a specific key length value, which can result in buffer
> > overflow depending on how the returned value is used. These functions are
> > used in three places in ieee80211/ieee80211_wx.c:
> >
> > ieee80211_wx_get_encode() :
> > The behavior of this function will be unchanged.
> >
> > ieee80211_wx_get_encode_ext() :
> > The result of the get_key function is written to ext->key_len,
> > resulting in a buffer overflow if the result is negative.
> >
> > ieee80211_wx_set_encode() :
> > The behavior of this function will change. When len is less than the
> > key length value, it will set a default key of all 0.
> >
> > Suggested-by: Dan Carpenter <[email protected]>
> > Signed-off-by: Rebecca Mckeever <[email protected]>
> > ---
> > drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_ccmp.c | 2 +-
> > drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_tkip.c | 2 +-
> > drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_wep.c | 2 +-
> > 3 files changed, 3 insertions(+), 3 deletions(-)
>
> I was not able to find the message where Dan suggested this solution.
> However it looks that we actually have problems in those callers when they
> get '-1' as the return code.
>
> I didn't look at the code with much attention but I think that returning
> '0' to signal errors is not so good.
>
> If I'm not missing something from the context, I'd rather return '-EINVAL'
> and change the callers to check for this specific error that would signal
> we have "len less than a specific len value". If so, act in accordance to
> the returned -EINVAL.
>
> For example, in a caller you may test:
>
> if (ext->key_len == -EINVAL || <some other test, if required>)
> <error path>
> <success path>
These are valid questions.
Ideally the errors wouldn't happen. Maybe they don't happen?
The error handling is copied from ieee80211_wx_get_encode_ext(). An all
zero password (rot13 security) is better than plaintext. So this is a
conservative fix which potentially fixes some memory corruption and
doesn't break anything.
A more extensive fix would require someone who understands the code
better or can test it.
regards,
dan carpenter