Re: PATCH] sms_decode_text(): Sanitize 8-bit data so that it is UTF8-clean.

["Andrew Bird (Sphere Systems)" <ajb spheresystems co uk>]

On Tuesday 27 September 2011, Dan Williams wrote:
> On Mon, 2011-09-26 at 18:29 -0400, Nathan Williams wrote:
> > This keeps ModemManager from crashing deep in the DBus libraries when
> > a SMS Get() or List() DBus operation finds a message that isn't valid
> > UTF-8 and/or has embedded NUL characters.
> > 
> > I'll be putting up a separate patch as a proposal for how to avoid
> > this problem in the new API.
> 
> Sounds fine; though in general we know the encoding that the message
> comes in with, and we know we need to convert to UTF-8 for D-Bus (and
> really, everything should be UTF-8 at the boundaries, it would be just
> horrid to expose any charset encoding details to clients and I don't
> think we have to).  So we should be able to convert to UTF-8 without any
> real loss of fidelity when reading the  message from the modem, and we
> should be able to convert from UTF-8 to a suitable charset (whatever
> we've selected from CSCS) when sending messages too.
> 
> In what cases would we want to send or receive essentially binary data
> via SMS?  AFAIK most of these cases show up as base64 or hex-string SMS
> if they aren't intended for human consumption.
> 
> In any case, applied, thanks!
> 
> Dan
> 
> >     - Nathan
> > 
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Hi Dan,
	Here's a case you might want to consider. Sometimes mobile networks send 
WAP pushes to signify that an MMS is ready for retrieval, or send the user 
revised phone settings etc. Now we can't currently do much with those but they 
are binary and can contain embedded \x00 which Dbus really won't transfer in a 
string. But it's no good just ignoring them and not showing the client the 
message because they take up valuable SIM based SMS slots, if we did then the 
user would not know of their existence and eventually the SIM would silently 
fill. I had one WAP push last week that spanned 4 SMS slots. On Wader we worked 
around this problem by Zipping and Base64 encoding the message before sending 
over Dbus [0] [1], but I couldn't think of a elegant solution without changing 
the spec. If you come up with a better solution please let me know and we can 
revise what we have.

[0]:https://forge.betavine.net/plugins/scmsvn/viewcvs.php/trunk/src/core/wader/common/mal.py?root=bcm&rev=1210&r1=1193&r2=1210
[1]:https://forge.betavine.net/plugins/scmsvn/viewcvs.php/trunk/src/core/wader/common/encoding.py?root=bcm&rev=1210&r1=1194&r2=1210

Andrew