mirror of
https://github.com/ElementsProject/lightning.git
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259 lines
7.7 KiB
C
259 lines
7.7 KiB
C
#include "config.h"
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#include <bitcoin/tx.h>
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#include <ccan/cast/cast.h>
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#include <common/blindedpath.h>
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#include <common/blinding.h>
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#include <common/bolt11.h>
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#include <common/hmac.h>
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#include <secp256k1_ecdh.h>
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#include <sodium.h>
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#include <wire/onion_wire.h>
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#ifndef SUPERVERBOSE
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#define SUPERVERBOSE(...)
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#endif
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/* Blinds node_id and calculates next blinding factor. */
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static bool blind_node(const struct privkey *path_privkey,
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const struct secret *ss,
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const struct pubkey *node,
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struct pubkey *node_alias,
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struct privkey *next_path_privkey)
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{
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struct pubkey path_pubkey;
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struct sha256 h;
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if (!blindedpath_get_alias(ss, node, node_alias))
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return false;
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SUPERVERBOSE("\t\"blinded_node_id\": \"%s\",\n",
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fmt_pubkey(tmpctx, node_alias));
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/* BOLT #4:
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* - $`E_{i+1} = SHA256(E_i || ss_i) * E_i`$
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* (`path_key`. NB: $`N_i`$ MUST NOT learn $`e_i`$)
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*/
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if (!pubkey_from_privkey(path_privkey, &path_pubkey))
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return false;
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SUPERVERBOSE("\t\"E\": \"%s\",\n",
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fmt_pubkey(tmpctx, &path_pubkey));
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/* BOLT #4:
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* - $`e_{i+1} = SHA256(E_i || ss_i) * e_i`$
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* (ephemeral private path key, only known by $`N_r`$)
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*/
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blinding_hash_e_and_ss(&path_pubkey, ss, &h);
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SUPERVERBOSE("\t\"H(E || ss)\": \"%s\",\n",
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fmt_sha256(tmpctx, &h));
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blinding_next_path_privkey(path_privkey, &h, next_path_privkey);
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SUPERVERBOSE("\t\"next_e\": \"%s\",\n",
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fmt_privkey(tmpctx, next_path_privkey));
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return true;
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}
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static u8 *enctlv_from_encmsg_raw(const tal_t *ctx,
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const struct privkey *path_privkey,
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const struct pubkey *node,
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const u8 *raw_encmsg TAKES,
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struct privkey *next_path_privkey,
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struct pubkey *node_alias)
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{
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struct secret ss, rho;
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u8 *ret;
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int ok;
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/* All-zero npub */
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static const unsigned char npub[crypto_aead_chacha20poly1305_ietf_NPUBBYTES];
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/* BOLT #4:
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* - $`ss_i = SHA256(e_i * N_i) = SHA256(k_i * E_i)`$
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* (ECDH shared secret known only by $`N_r`$ and $`N_i`$)
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*/
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if (secp256k1_ecdh(secp256k1_ctx, ss.data,
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&node->pubkey, path_privkey->secret.data,
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NULL, NULL) != 1)
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return NULL;
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SUPERVERBOSE("\t\"ss\": \"%s\",\n",
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fmt_secret(tmpctx, &ss));
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/* This calculates the node's alias, and next path_key */
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if (!blind_node(path_privkey, &ss, node, node_alias, next_path_privkey))
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return NULL;
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ret = tal_dup_talarr(ctx, u8, raw_encmsg);
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/* BOLT #4:
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* - $`rho_i = HMAC256(\text{"rho"}, ss_i)`$
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* (key used to encrypt `encrypted_recipient_data` for $`N_i`$ by $`N_r`$)
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*/
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subkey_from_hmac("rho", &ss, &rho);
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SUPERVERBOSE("\t\"rho\": \"%s\",\n",
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fmt_secret(tmpctx, &rho));
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/* BOLT #4:
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* - MUST encrypt each `encrypted_data_tlv[i]` with ChaCha20-Poly1305 using
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* the corresponding $`rho_i`$ key and an all-zero nonce to produce
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* `encrypted_recipient_data[i]`
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*/
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/* Encrypt in place */
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towire_pad(&ret, crypto_aead_chacha20poly1305_ietf_ABYTES);
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ok = crypto_aead_chacha20poly1305_ietf_encrypt(ret, NULL,
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ret,
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tal_bytelen(ret)
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- crypto_aead_chacha20poly1305_ietf_ABYTES,
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NULL, 0,
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NULL, npub,
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rho.data);
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assert(ok == 0);
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return ret;
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}
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u8 *encrypt_tlv_encrypted_data(const tal_t *ctx,
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const struct privkey *path_privkey,
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const struct pubkey *node,
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const struct tlv_encrypted_data_tlv *tlv,
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struct privkey *next_path_privkey,
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struct pubkey *node_alias)
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{
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struct privkey unused;
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u8 *tlv_wire = tal_arr(NULL, u8, 0);
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towire_tlv_encrypted_data_tlv(&tlv_wire, tlv);
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/* last hop doesn't care about next path_key */
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if (!next_path_privkey)
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next_path_privkey = &unused;
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return enctlv_from_encmsg_raw(ctx, path_privkey, node, take(tlv_wire),
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next_path_privkey, node_alias);
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}
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bool unblind_onion(const struct pubkey *path_key,
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void (*ecdh)(const struct pubkey *point, struct secret *ss),
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struct pubkey *onion_key,
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struct secret *ss)
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{
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struct secret hmac;
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/* BOLT #4:
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* A reader:
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*...
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* - if `path_key` is specified:
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* - Calculate the `blinding_ss` as ECDH(`path_key`, `node_privkey`).
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* - Either:
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* - Tweak `public_key` by multiplying by $`HMAC256(\text{"blinded\_node\_id"}, blinding\_ss)`$.
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* - or (equivalently):
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* - Tweak its own `node_privkey` below by multiplying by $`HMAC256(\text{"blinded\_node\_id"}, blinding\_ss)`$.
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*/
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ecdh(path_key, ss);
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subkey_from_hmac("blinded_node_id", ss, &hmac);
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/* We tweak the *ephemeral* key from the onion and use
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* our normal privkey: since hsmd knows only how to ECDH with
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* our real key. */
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return secp256k1_ec_pubkey_tweak_mul(secp256k1_ctx,
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&onion_key->pubkey,
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hmac.data) == 1;
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}
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u8 *decrypt_encmsg_raw(const tal_t *ctx,
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const struct secret *ss,
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const u8 *enctlv)
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{
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struct secret rho;
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u8 *dec;
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/* All-zero npub */
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static const unsigned char npub[crypto_aead_chacha20poly1305_ietf_NPUBBYTES];
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/* BOLT #4:
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* The reader of the `encrypted_recipient_data`:
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*...
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*- $`rho_i = HMAC256(\text{"rho"}, ss_i)`$
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*- MUST decrypt the `encrypted_recipient_data` field using $`rho_i`$
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* as a key using ChaCha20-Poly1305 and an all-zero nonce key.
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*/
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subkey_from_hmac("rho", ss, &rho);
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/* BOLT #4:
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* - If the `encrypted_recipient_data` field is missing, cannot be
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* decrypted into an `encrypted_data_tlv` or contains unknown even
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* fields:
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* - MUST return an error
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*/
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/* Too short? */
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if (tal_bytelen(enctlv) < crypto_aead_chacha20poly1305_ietf_ABYTES)
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return NULL;
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dec = tal_arr(ctx, u8, tal_bytelen(enctlv)
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- crypto_aead_chacha20poly1305_ietf_ABYTES);
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if (crypto_aead_chacha20poly1305_ietf_decrypt(dec, NULL,
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NULL,
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enctlv, tal_bytelen(enctlv),
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NULL, 0,
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npub,
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rho.data) != 0)
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return tal_free(dec);
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return dec;
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}
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struct tlv_encrypted_data_tlv *decrypt_encrypted_data(const tal_t *ctx,
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const struct secret *ss,
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const u8 *enctlv)
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{
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const u8 *cursor = decrypt_encmsg_raw(tmpctx, ss, enctlv);
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size_t maxlen = tal_bytelen(cursor);
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/* BOLT #4:
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* - If the `encrypted_recipient_data` field is missing, cannot be
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* decrypted into an `encrypted_data_tlv` or contains unknown even
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* fields:
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* - MUST return an error
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*/
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/* Note: our parser consider nothing is a valid TLV, but decrypt_encmsg_raw
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* returns NULL if it couldn't decrypt. */
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if (!cursor)
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return NULL;
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return fromwire_tlv_encrypted_data_tlv(ctx, &cursor, &maxlen);
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}
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bool blindedpath_get_alias(const struct secret *ss,
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const struct pubkey *my_id,
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struct pubkey *alias)
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{
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struct secret node_id_blinding;
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/* BOLT #4:
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* - $`B_i = HMAC256(\text{"blinded\_node\_id"}, ss_i) * N_i`$
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* (blinded `node_id` for $`N_i`$, private key known only by $`N_i`$)
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*/
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subkey_from_hmac("blinded_node_id", ss, &node_id_blinding);
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SUPERVERBOSE("\t\"HMAC256('blinded_node_id', ss)\": \"%s\",\n",
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fmt_secret(tmpctx, &node_id_blinding));
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*alias = *my_id;
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return secp256k1_ec_pubkey_tweak_mul(secp256k1_ctx,
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&alias->pubkey,
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node_id_blinding.data) == 1;
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}
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void blindedpath_next_path_key(const struct tlv_encrypted_data_tlv *enc,
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const struct pubkey *path_key,
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const struct secret *ss,
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struct pubkey *next_path_key)
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{
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/* BOLT #4:
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* - $`E_{i+1} = SHA256(E_i || ss_i) * E_i`$
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* ...
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* - If the `encrypted_data_tlv` contains a `next_path_key_override`:
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* - MUST use it as the next `path_key`.
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* - Otherwise:
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* - MUST use $`E_{i+1} = SHA256(E_i || ss_i) * E_i`$ as the next `path_key`
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*/
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if (enc->next_path_key_override)
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*next_path_key = *enc->next_path_key_override;
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else {
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struct sha256 h;
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blinding_hash_e_and_ss(path_key, ss, &h);
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blinding_next_path_key(path_key, &h, next_path_key);
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}
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}
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