wpa_supplicant can't find hidden SSID

Dan Williams dcbw at redhat.com
Mon Mar 23 12:00:59 EDT 2009


On Mon, 2009-03-23 at 16:04 +0200, Chuck Tuffli wrote:
> I ran into a problem that sounds similar to this with our driver which
> was ultimately caused by the Linux Wireless Extensions.
> 
> Some AP implement hidden SSID by setting the SSID to 32 NULL characters.
> The wireless extensions code in the kernel (ioctl_standard_iw_point() in
> net/wireless/wext.c) determines if a WEXT client is using compatibility
> mode (i.e. adds an extra terminating NULL character on SSID - the
> behavior before version 21) by checking if the last character is NULL,
> and strips off this byte if present. The problem then becomes that when
> using WE versions 21 and later, the SSID supplied to the driver (31 NULL
> characters) doesn't match the SSID seen on air (32 NULL characters) and
> our driver wouldn't associate. Note that if you use a version of WE
> prior to 20, this isn't an issue because the supplicant (and all the
> wireless tools for that matter) will add a sacrificial 33'rd NULL
> character to the string prior to passing it to the kernel.



> I sent out a question about this behavior and patch fixing it to some of
> the maintainers, but never received a response. Can you try compiling
> the supplicant with an earlier version of WE to see if this fixes your
> problem?

What was the subject of that mail?  Can't find it on linux-wireless...
Looks like what should probably be done is if the SSID is all NULLs, and
the iw_point length is IW_ESSID_MAX_SIZE, just use IW_ESSID_MAX_SIZE
instead of doing the compat thing.

Dan

> ---chuck
> 
> > -----Original Message-----
> > From: hostap-bounces at lists.shmoo.com 
> > [mailto:hostap-bounces at lists.shmoo.com] On Behalf Of Jouni Malinen
> > Sent: Thursday, March 19, 2009 11:10 AM
> > To: hostap at lists.shmoo.com
> > Subject: Re: wpa_supplicant can't find hidden SSID
> > 
> > On Thu, Mar 19, 2009 at 05:05:01PM +0000, planetf1 wrote:
> > 
> > > So driver issue likely? (in the context of a nasty AP anyway)
> > 
> > Sounds like a driver issue to me. Which driver version are 
> > you using? If the driver does not send out a Probe Request 
> > with the specific SSID you are trying to use, it won't be 
> > able to use this network.
> > 
> > -- 
> > Jouni Malinen                                            PGP 
> > id EFC895FA
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