initial tweaks and questions for the proposed udp spec

svn:r6081
This commit is contained in:
Roger Dingledine 2006-02-26 06:57:06 +00:00
parent a3d1671f95
commit 8614b958c6

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@ -73,7 +73,7 @@ Contents
implementations MUST support the DTLS ciphersuite "[TODO]".
DTLS connections are formed using the same protocol as TLS connections.
This occurs upon request, following at CREATE_UDP or CREATE_FAST_UDP cell,
This occurs upon request, following a CREATE_UDP or CREATE_FAST_UDP cell,
as detailed in section 4.6.
Once a paired TLS/DTLS connection is established, the two sides send cells
@ -119,10 +119,13 @@ Contents
section 4.5.
[Should the sequence number only appear in RELAY packets? The overhead is
small, and I'm hesitant to force more code paths on the implementor.]
small, and I'm hesitant to force more code paths on the implementor. -ML]
[There's already a separate relay header that has other material in it,
so it wouldn't be the end of the world to move it there if it's
appropriate. -RD]
[Having separate commands for UDP circuits seems necessary, unless we can
assume a flag day event for a large number of tor nodes.]
assume a flag day event for a large number of tor nodes. -ML]
4. Circuit management
@ -131,6 +134,10 @@ Contents
Keys are set up for UDP circuits in the same fashion as for TCP circuits.
Each UDP circuit shares keys with its corresponding TCP circuit.
[If the keys are used for both TCP and UDP connections, how does it
work to mix sequence-number-less cells with sequenced-numbered cells --
how do you know you have the encryption order right? -RD]
4.3. Creating circuits
UDP circuits are created as TCP circuits, using the *_UDP cells as
@ -157,12 +164,16 @@ Contents
Use Kb as key; encrypt, using sequence number to synchronize
ciphertext and keystream.
Note that in counter mode, decrypt and encrypt are the same operation.
[Since the sequence number is only 2 bytes, what do you do when it
rolls over? -RD]
Each stream encrypted by a Kf or Kb has a corresponding unique state,
captured by a sequence number; the originator of each such stream chooses
the initial sequence number randomly, and increments it only with RELAY
cells. [This counts cells; unlike, say, TCP, tor uses fixed-size cells, so
there's no need for counting bytes directly. Right? - ML]
[I believe this is true. You'll find out for sure when you try to
build it. ;) -RD]
The OR then decides whether it recognizes the relay cell, by
inspecting the payload as described in section 5.1 below. If the OR
@ -199,7 +210,7 @@ Contents
UDP port [2 bytes]
Onion skin [186 bytes]
Identity fingerprint [20 bytes]
The address field and ports denote the IPV4 address and ports of the next OR
in the circuit.
@ -273,6 +284,9 @@ Contents
set to the SHA-1 digest of the current RELAY cells' entire payload, with the
digest field set to zero. Coupled with a randomly-chosen streamID, this
provides per-cell integrity checking on UDP cells.
[If you drop malformed UDP relay cells but don't close the circuit,
then this 8 bytes of digest is not as strong as what we get in the
TCP-circuit side. Is this a problem? -RD]
When the 'recognized' field of a RELAY cell is zero, and the digest
is correct, the cell is considered "recognized" for the purposes of
@ -364,3 +378,10 @@ The items' formats are as follows:
directory-related HTTP connections; and UDPPort is a port at which
this OR accepts DTLS connections for UDP data. If any port is not
supported, the value 0 is given instead of a port number.
Other sections:
What changes need to happen to each node's exit policy to support this? -RD