We need to control the *inputs* to the anchor tx, to make sure they
pay to witness scripts (thus the anchor is immalleable). The easiest
way to do this is to hand out P2SH addresses for the user, and have
them pay into those. Then they hand us that tx and we use it to
create the anchor.
This is not a long-term solution!
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
After useful feedback from Anthony Towns and Mats Jerratsch (of
thunder.network fame), this is the third version of inter-node crypto.
1) First, each side sends a 33-byte session pubkey. This is a
bitcoin-style compressed EC key, unique for each session.
2) ECDH is used to derive a shared secret. From this we generate
the following transmission encoding parameters for each side:
Session AES-128 key: SHA256(shared-secret || my-sessionpubkey || 0)
Session HMAC key: SHA256(shared-secret || my-sessionpubkey || 1)
IV for AES: SHA256(shared-secret || my-sessionpubkey || 2)
3) All packets from then on are encrypted of form:
/* HMAC, covering totlen and data */
struct sha256 hmac;
/* Total data transmitted (including this). */
le64 totlen;
/* Encrypted contents, rounded up to 16 byte boundary. */
u8 data[];
4) The first packet is an Authenticate protobuf, containing this node's
pubkey, and a bitcoin-style EC signature of the other side's session
pubkey.
5) Unknown protobuf fields are handled in the protocol as follows
(including in the initial Authenticate packet):
1) Odd numbered fields are optional, and backwards compatible.
2) Even numbered fields are required; abort if you get one.
Currently both sides just send an error packet "hello" after the
handshake, and make sure they receive the same.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Also based on pettycoin code.
(With embarrassing bug fixed where it didn't increment the address used,
thus using 100% CPU if that connect failed!)
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
For better or worse, the ccan/timer structure is completely minimal,
and designed to be wrapped inside a container structure.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
