summary: Groupware message receive integer overflow
discoveredBy: Sean (infamous42md)
Integer overflow in memory allocation results in heap overflow. By passing the
size variable as `~0`, integer overflows to 0 when 1 is added in `g_alloc()`.
A `malloc(0)` call results in 16 bytes of memory being allocated on IA- 32.
Then we can overflow the heap when `nm_read_all()` is called next step.
Usually cases like this suck for exploitation, because the len (`~0`) is so
large that a following call to `memcpy()` or `strcpy()` will just run into
kernel mem or unmapped address and fault. However in this case we read the
data from the network via a `read()` call, so we can just stop sending data and
close the connection to short out before `~0` bytes are read. However, this is
triggered by input from the server, not directly from a client. Someone
running a malicious groupware server could leverage this to run arbitrary code
Bounds checking was added.