7 May
2012
7 May
'12
10:08 p.m.
Hi,
First:
In file openbsc/openbsc/src/libmsc/db.c on line 372 there is
"ainfo->a3a8_ki_len = sizeof(ainfo->a3a8_ki_len);"
which takes the sizeof of the length value. This always results in a wrong keylength and
hence no authentification will ever be executed. This should rather be changed to:
ainfo->a3a8_ki_len = sizeof(ainfo->a3a8_ki);
There is indeed a bug. But it's only in the "exception" processing, so
in a normal case that shouldn't have prevented auth. (and since we use
auth at the camp and 27c3, I can guarantee it works in the normal case
:)
Secondly:
I haven't found the piece of code which is responsible for this bug particulary but:
Whenever the key for the a3a8_comp128 is being read from the database a shift of one bit
occurs.
i.e. when you set the a3a8_key in the hlr.sqlite3 to 01010101010101010101010101010101 the
value being processed as key in the a3a8_comp128 algorithm is
02020202020202020202020202020202.
That's not a bug per-se. I think you're assuming the binary value
stored in the field is used as key. This is _not_ the case. libdbi has
some special binary escaping that results in the binary value stored
not being the "raw" key.
You have to either:
- Use the vty to set the key
- Set the key using libdbi
- Escape the binary value yourself the same way as libdbi does.
Cheers,
Sylvain