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sphinx: Expose the shared secret creation function

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This commit is contained in:
Christian Decker
2020-03-02 19:39:16 +01:00
committed by Rusty Russell
parent 49a3321d7e
commit fd37c5b672
3 changed files with 37 additions and 11 deletions
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18
common/sphinx.c
View File

@@ -364,12 +364,12 @@ static bool blind_group_element(struct pubkey *blindedelement,
return true;
}
static bool create_shared_secret(struct secret *secret,
bool sphinx_create_shared_secret(struct secret *privkey,
const struct pubkey *pubkey,
const struct secret *session_key)
const struct secret *secret)
{
if (secp256k1_ecdh(secp256k1_ctx, secret->data, &pubkey->pubkey,
session_key->data, NULL, NULL) != 1)
if (secp256k1_ecdh(secp256k1_ctx, privkey->data, &pubkey->pubkey,
secret->data, NULL, NULL) != 1)
return false;
return true;
}
@@ -379,8 +379,8 @@ bool onion_shared_secret(
const struct onionpacket *packet,
const struct privkey *privkey)
{
return create_shared_secret(secret, &packet->ephemeralkey,
&privkey->secret);
return sphinx_create_shared_secret(secret, &packet->ephemeralkey,
&privkey->secret);
}
static void generate_key_set(const struct secret *secret,
@@ -408,8 +408,8 @@ static struct hop_params *generate_hop_params(
path->session_key->data) != 1)
return NULL;
if (!create_shared_secret(&params[0].secret, &path->hops[0].pubkey,
path->session_key))
if (!sphinx_create_shared_secret(
&params[0].secret, &path->hops[0].pubkey, path->session_key))
return NULL;
compute_blinding_factor(
@@ -491,7 +491,7 @@ static void sphinx_prefill(u8 *routinginfo, const struct sphinx_path *sp,
/* Now fill in the obfuscation stream, which can be regenerated by the
* node processing this onion. */
create_shared_secret(&shared_secret, sp->rendezvous_id, sp->session_key);
sphinx_create_shared_secret(&shared_secret, sp->rendezvous_id, sp->session_key);
sphinx_prefill_stream_xor(routinginfo + prefill_offset, prefill_size, &shared_secret);
}

11
common/sphinx.h
View File

@@ -253,6 +253,17 @@ bool sphinx_path_set_rendezvous(struct sphinx_path *sp,
u8 *sphinx_decompress(const tal_t *ctx, const u8 *compressed,
struct secret *shared_secret);
/**
* Use ECDH to generate a shared secret from a privkey and a pubkey.
*
* Sphinx uses shared secrets derived from a private key and a public key
* using ECDH in a number of places. This is a simple wrapper around the
* secp256k1 functions, with our internal types.
*/
bool sphinx_create_shared_secret(struct secret *privkey,
const struct pubkey *pubkey,
const struct secret *secret);
#if DEVELOPER
/* Override to force us to reject valid onion packets */
extern bool dev_fail_process_onionpacket;

19
devtools/onion.c
View File

@@ -310,8 +310,23 @@ static void decompress(char *hexprivkey, char *hexonion)
pubkey_from_der(compressed + 1, PUBKEY_SIZE, &ephkey);
decompressed = sphinx_decompress(NULL, compressed, &shared_secret);
printf("Decompressed Onion: %s\n", tal_hex(NULL, decompressed));
tinyonion = sphinx_compressed_onion_deserialize(NULL, compressed);
if (tinyonion == NULL)
errx(1, "Could not deserialize compressed onion");
if (!sphinx_create_shared_secret(&shared_secret,
&tinyonion->ephemeralkey,
&rendezvous_key.secret))
errx(1,
"Could not generate shared secret from ephemeral key %s "
"and private key %s",
pubkey_to_hexstr(NULL, &ephkey), hexprivkey);
onion = sphinx_decompress(NULL, tinyonion, &shared_secret);
if (onion == NULL)
errx(1, "Could not decompress compressed onion");
printf("Decompressed Onion: %s\n", tal_hex(NULL, serialize_onionpacket(NULL, onion)));
}
/* Tal wrappers for opt. */