STP mitm attack idea

[Przemyslaw Borkowski <xperience@xxxxxxxxxx>]

As I read in many white papers about attacks on Spanning Tree Protocol, I found 
mitm attack on two STP switches, one station and two ethernet NICs.
That attack is in most cases useless because:
- we need physical access to two (not one switch)
- two cards in station
As two cards are possible, that access to two switches in one ie. office is 
almost impossible.
My idea for modification of this attack needs:
- two stations to attack by mitm (A and B)
- two or more switches with STP protocol
- two attacking stations connected to two different switches in way beetween 
attacked stations (C and D) 

A ---- switch 1 ----- switch 2 ----- B
          |              |
          |              |
          C              D

Take first scenario:
1. A - sends frame to B
2. Switch 1 - accepts frame and forwards it to switch 2
3. Switch 2 - accepts frame via link from switch 1 and forwards it to B

Second scenario:
1. Station C and station D starts to send frames to break link beetween switch 
1 and switch 2, and announce non existing connection and switch from C port on 
switch 1 to D port on switch 2

A ---- switch 1 --X-- switch 2 ----- B
          |              |
          |              |
          C  --no conn-- D
2. Station A sends frame to B
3. Frame is forwarded to C station
4. Station C stores frame in memory
5. After equal timing station C and station D repair link beetween switch 1 and 
2
6. station C resends stored packet to station D (ie in tunnel or encapsulated 
in ip packet)
7. stations C and D break link beetween switches 1 and 2
8. station D sends transmitted packet to station B

Advantages
- no need for one station with two links to two switches
- needs two stations, either compromised or not (in large multiswitch 
enviroment with many stations sometimes we can find in example two compromised 
windows or linux hosts)
- when we have good timing and packet detection method, we can separate one 
protocol connection from whole traffic

Disadvantages of method.
- stops whole traffic beetween switches, and needs delicate timing
- when link beetween switch 1 and 2 is working we can't see frames that flying 
across wire

Additional information.
- timing question, ie - retransmition time beetween tcp frames, and time to 
break and repair link - is it possible to do it before frame is retransmited?

Uh that's all. Please think about it is possible, because my programming skills 
are to low to make it working.

With regards
Xperience