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onion_message: don't use general secret, use per-message secret.

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We had a scheme where lightningd itself would put a per-node secret in
the blinded path, then we'd tell the caller when it was used.  Then it
simply checks the alias to determine if the correct path was used.

But this doesn't work when we start to offer multiple blinded paths.
So go for a far simpler scheme, where the secret is generated (and
stored) by the caller, and hand it back to them.

We keep the split "with secret" or "without secret" API, since I'm
sure callers who don't care about the secret won't check that it
doesn't exist!  And without that, someone can use a blinded path for a
different message and get a response which may reveal the node.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
2022-11-09 12:00:10 +10:30
committed by Christian Decker
parent 4cfd972407
commit 5becfa6ee1
11 changed files with 51 additions and 74 deletions
Download Patch File Download Diff File Expand all files Collapse all files

32
plugins/fetchinvoice.c
View File

@@ -29,8 +29,8 @@ static LIST_HEAD(sent_list);
struct sent {
/* We're in sent_invreqs, awaiting reply. */
struct list_node list;
/* The alias used by reply */
struct pubkey *reply_alias;
/* The secret used by reply */
struct secret *reply_secret;
/* The command which sent us. */
struct command *cmd;
/* The offer we are trying to get an invoice/payment for. */
@@ -48,12 +48,12 @@ struct sent {
u32 wait_timeout;
};
static struct sent *find_sent_by_alias(const struct pubkey *alias)
static struct sent *find_sent_by_secret(const struct secret *pathsecret)
{
struct sent *i;
list_for_each(&sent_list, i, list) {
if (i->reply_alias && pubkey_eq(i->reply_alias, alias))
if (i->reply_secret && secret_eq_consttime(i->reply_secret, pathsecret))
return i;
}
return NULL;
@@ -409,18 +409,16 @@ static struct command_result *recv_modern_onion_message(struct command *cmd,
const char *buf,
const jsmntok_t *params)
{
const jsmntok_t *om, *aliastok;
const jsmntok_t *om, *secrettok;
struct sent *sent;
struct pubkey alias;
struct secret pathsecret;
struct command_result *err;
om = json_get_member(buf, params, "onion_message");
aliastok = json_get_member(buf, om, "our_alias");
if (!aliastok || !json_to_pubkey(buf, aliastok, &alias))
return command_hook_success(cmd);
sent = find_sent_by_alias(&alias);
secrettok = json_get_member(buf, om, "pathsecret");
json_to_secret(buf, secrettok, &pathsecret);
sent = find_sent_by_secret(&pathsecret);
if (!sent) {
plugin_log(cmd->plugin, LOG_DBG,
"No match for modern onion %.*s",
@@ -703,11 +701,6 @@ static struct command_result *use_reply_path(struct command *cmd,
json_tok_full_len(result),
json_tok_full(buf, result));
/* Remember our alias we used so we can recognize reply */
sending->sent->reply_alias
= tal_dup(sending->sent, struct pubkey,
&rpath->path[tal_count(rpath->path)-1]->blinded_node_id);
return send_modern_message(cmd, rpath, sending);
}
@@ -722,6 +715,10 @@ static struct command_result *make_reply_path(struct command *cmd,
return command_fail(cmd, PAY_ROUTE_NOT_FOUND,
"Refusing to talk to ourselves");
/* Create transient secret so we can validate reply! */
sending->sent->reply_secret = tal(sending->sent, struct secret);
randombytes_buf(sending->sent->reply_secret, sizeof(struct secret));
req = jsonrpc_request_start(cmd->plugin, cmd, "blindedpath",
use_reply_path,
forward_error,
@@ -733,6 +730,7 @@ static struct command_result *make_reply_path(struct command *cmd,
for (int i = nhops - 2; i >= 0; i--)
json_add_pubkey(req->js, NULL, &sending->sent->path[i]);
json_array_end(req->js);
json_add_secret(req->js, "pathsecret", sending->sent->reply_secret);
return send_outreq(cmd->plugin, req);
}
@@ -1723,7 +1721,7 @@ static const char *init(struct plugin *p, const char *buf UNUSED,
static const struct plugin_hook hooks[] = {
{
"onion_message_ourpath",
"onion_message_recv_secret",
recv_modern_onion_message
},
{

2
plugins/offers.c
View File

@@ -127,7 +127,7 @@ static struct command_result *onion_message_modern_call(struct command *cmd,
static const struct plugin_hook hooks[] = {
{
"onion_message_blinded",
"onion_message_recv",
onion_message_modern_call
},
};