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sphinx: Add sphinx_path struct to encapsulate routing related info

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`struct sphinx_path` serves as a container for all the routing related
information, with a couple of constructors that can be used for normal
operation or testing (with pre-determined `session_key`).

Signed-off-by: Christian Decker <decker.christian@gmail.com>
This commit is contained in:
Christian Decker
2019-02-14 14:54:17 +01:00
committed by Rusty Russell
parent ea4831363e
commit 71cf4e1b39
2 changed files with 82 additions and 0 deletions
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51
common/sphinx.c
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@@ -34,6 +34,57 @@ struct keyset {
u8 gamma[KEY_LEN];
};
/*
* All the necessary information to generate a valid onion for this hop on a
* sphinx path. The payload is preserialized in order since the onion
* generation is payload agnostic. */
struct sphinx_hop {
struct pubkey pubkey;
u8 realm;
const u8 *payload;
u8 hmac[HMAC_SIZE];
};
/* Encapsulates the information about a given payment path for the the onion
* routing algorithm.
*/
struct sphinx_path {
/* The session_key used to generate the shared secrets along the
* path. This MUST be generated in a cryptographically secure manner,
* and is exposed solely for testing, i.e., it can be set to known
* values in unit tests. If unset it'll be generated during the packet
* generation. */
struct secret *session_key;
/* The associated data is appended to the packet when generating the
* HMAC, but is not passed along as part of the packet. It is used to
* ensure some external data (HTLC payment_hash) is not modified along
* the way. */
u8 *associated_data;
/* The individual hops on this route. */
struct sphinx_hop *hops;
};
struct sphinx_path *sphinx_path_new(const tal_t *ctx, const u8 *associated_data)
{
struct sphinx_path *sp = tal(ctx, struct sphinx_path);
sp->associated_data = tal_dup_arr(sp, u8, associated_data,
tal_bytelen(associated_data), 0);
sp->session_key = NULL;
sp->hops = tal_arr(sp, struct sphinx_hop, 0);
return sp;
}
struct sphinx_path *sphinx_path_new_with_key(const tal_t *ctx,
const u8 *associated_data,
const struct secret *session_key)
{
struct sphinx_path *sp = sphinx_path_new(ctx, associated_data);
sp->session_key = tal_dup(sp, struct secret, session_key);
return sp;
}
/* Small helper to append data to a buffer and update the position
* into the buffer
*/