Re: Locking a mutex by name?

[Ron <ron () skullsecurity net>]

Patrick Donnelly wrote:
> Yes, in the case of a library that is best.
>
> As for storing the mutexes for a library, placing them in the registry
> feels very wrong to me.
>
> I've looked at the smb library in nselib/smb.lua. Right now it appears
> the library has a global lock, so only on smb connection can be active
> at a time? So instead you want the mutexes on a per-host basis? If
> this is the case, I recommend using a local mutexes table , with smb
> connection keys and mutex values, that holds the mutexes for you for
> each smb connection. The table will have weak keys so an smb
> connection can be collected (and thus the mutex as well). Each mutex
> will still be passed the "SMB-hostname" string so you can ensure only
> one smb connection per host. I've attached a patch that does this.

All right, I implemented it like that and it appears to be working. You
can take a look at it, if you'd like, in:
svn://svn.insecure.org/nmap-exp/ron/nmap-smb

But suffice to say, I'm doing this:

--
local mutexes = setmetatable({}, {__mode = "k"});
[...]
local function get_mutex(smbstate)
    local mutex_name = "SMB-"
    local mutex

    -- Decide whether to use the name or the ip address as the unique
identifier
    if(smbstate['name'] ~= nil) then
        mutex_name = mutex_name .. smbstate['name']
    else
        mutex_name = mutex_name .. smbstate['ip']
    end

    if(mutexes[smbstate] == nil) then
        mutex = nmap.mutex(mutex_name)
        mutexes[smbstate] = mutex
    else
        mutex = mutexes[smbstate]
    end

    stdnse.print_debug(3, "SMB: Using mutex named '%s'", mutex_name)

    return mutex
end
--


Thanks for the help!

Ron

-- 
Ron Bowes
http://www.skullsecurity.org/

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