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#include <assert.h>
#include <bitcoin/privkey.h>
#include <ccan/build_assert/build_assert.h>
#include <ccan/crypto/hkdf_sha256/hkdf_sha256.h>
#include <ccan/endian/endian.h>
#include <ccan/fdpass/fdpass.h>
#include <ccan/mem/mem.h>
#include <ccan/read_write_all/read_write_all.h>
#include <ccan/short_types/short_types.h>
#include <common/crypto_sync.h>
#include <common/debug.h>
#include <common/status.h>
#include <common/type_to_string.h>
#include <common/version.h>
#include <errno.h>
#include <handshaked/gen_handshake_wire.h>
#include <hsmd/client.h>
#include <secp256k1.h>
#include <secp256k1_ecdh.h>
#include <sodium/crypto_aead_chacha20poly1305.h>
#include <sodium/randombytes.h>
#include <stdio.h>
#include <unistd.h>
#include <wire/peer_wire.h>
#include <wire/wire.h>
#include <wire/wire_sync.h>
#define REQ_FD STDIN_FILENO
/* BOLT #8:
*
* * `generateKey()`
* * where generateKey generates and returns a fresh `secp256k1` keypair
* * the object returned by `generateKey` has two attributes:
* * `.pub`: which returns an abstract object representing the
* public key
* * `.priv`: which represents the private key used to generate the
* public key
*/
struct keypair {
struct pubkey pub;
struct privkey priv;
};
static struct keypair generate_key(void)
{
struct keypair k;
do {
randombytes_buf(k.priv.secret.data, sizeof(k.priv.secret.data));
} while (!secp256k1_ec_pubkey_create(secp256k1_ctx,
&k.pub.pubkey, k.priv.secret.data));
return k;
}
/* BOLT #8:
*
* Throughout the handshake process, each side maintains these variables:
*
* * `ck`: The **chaining key**. This value is the accumulated hash of all
* previous ECDH outputs. At the end of the handshake, `ck` is used to
* derive the encryption keys for lightning messages.
*
* * `h`: The **handshake hash**. This value is the accumulated hash of _all_
* handshake data that has been sent and received so far during the
* handshake process.
*
* * `temp_k1`, `temp_k2`, `temp_k3`: **intermediate keys** used to
* encrypt/decrypt the zero-length AEAD payloads at the end of each
* handshake message.
*
* * `e`: A party's **ephemeral keypair**. For each session a node MUST
* generate a new ephemeral key with strong cryptographic randomness.
*
* * `s`: A party's **static public key** (`ls` for local, `rs` for remote)
*/
struct handshake {
struct secret ck;
struct secret temp_k;
struct sha256 h;
struct keypair e;
struct secret ss;
};
/* h = SHA-256(h || data) */
static void sha_mix_in(struct sha256 *h, const void *data, size_t len)
{
struct sha256_ctx shactx;
sha256_init(&shactx);
sha256_update(&shactx, h, sizeof(*h));
sha256_update(&shactx, data, len);
sha256_done(&shactx, h);
}
/* h = SHA-256(h || pub.serializeCompressed()) */
static void sha_mix_in_key(struct sha256 *h, const struct pubkey *key)
{
u8 der[PUBKEY_DER_LEN];
size_t len = sizeof(der);
secp256k1_ec_pubkey_serialize(secp256k1_ctx, der, &len, &key->pubkey,
SECP256K1_EC_COMPRESSED);
assert(len == sizeof(der));
sha_mix_in(h, der, sizeof(der));
}
/* out1, out2 = HKDF(in1, in2)` */
static void hkdf_two_keys(struct secret *out1, struct secret *out2,
const struct secret *in1,
const void *in2, size_t in2_size)
{
/* BOLT #8:
*
* * `HKDF(salt,ikm)`: a function is defined in [3](#reference-3),
* evaluated with a zero-length `info` field.
* * All invocations of the `HKDF` implicitly return `64-bytes`
* of cryptographic randomness using the extract-and-expand
* component of the `HKDF`.
*/
struct secret okm[2];
status_trace("# HKDF(0x%s,%s%s)",
tal_hexstr(trc, in1, sizeof(*in1)),
in2_size ? "0x" : "zero",
tal_hexstr(trc, in2, in2_size));
BUILD_ASSERT(sizeof(okm) == 64);
hkdf_sha256(okm, sizeof(okm), in1, sizeof(*in1), in2, in2_size,
NULL, 0);
*out1 = okm[0];
*out2 = okm[1];
}
static void le64_nonce(unsigned char *npub, u64 nonce)
{
/* BOLT #8:
*
* ...with nonce `n` encoded as 32 zero bits followed by a
* *little-endian* 64-bit value (this follows the Noise Protocol
* convention, rather than our normal endian).
*/
le64 le_nonce = cpu_to_le64(nonce);
const size_t zerolen = crypto_aead_chacha20poly1305_ietf_NPUBBYTES - sizeof(le_nonce);
BUILD_ASSERT(crypto_aead_chacha20poly1305_ietf_NPUBBYTES >= sizeof(le_nonce));
/* First part is 0, followed by nonce. */
memset(npub, 0, zerolen);
memcpy(npub + zerolen, &le_nonce, sizeof(le_nonce));
}
/* BOLT #8:
* * `encryptWithAD(k, n, ad, plaintext)`: outputs `encrypt(k, n, ad,
* plaintext)`
* * where `encrypt` is an evaluation of `ChaCha20-Poly1305` (IETF
* variant) with the passed arguments, with nonce `n`
*/
static void encrypt_ad(const struct secret *k, u64 nonce,
const void *additional_data, size_t additional_data_len,
const void *plaintext, size_t plaintext_len,
void *output, size_t outputlen)
{
unsigned char npub[crypto_aead_chacha20poly1305_ietf_NPUBBYTES];
unsigned long long clen;
int ret;
assert(outputlen == plaintext_len + crypto_aead_chacha20poly1305_ietf_ABYTES);
le64_nonce(npub, nonce);
BUILD_ASSERT(sizeof(*k) == crypto_aead_chacha20poly1305_ietf_KEYBYTES);
status_trace("# encryptWithAD(0x%s, 0x%s, 0x%s, %s%s)",
tal_hexstr(trc, k, sizeof(*k)),
tal_hexstr(trc, npub, sizeof(npub)),
tal_hexstr(trc, additional_data, additional_data_len),
plaintext_len ? "0x" : "<empty>",
tal_hexstr(trc, plaintext, plaintext_len));
ret = crypto_aead_chacha20poly1305_ietf_encrypt(output, &clen,
memcheck(plaintext, plaintext_len),
plaintext_len,
additional_data, additional_data_len,
NULL, npub, k->data);
assert(ret == 0);
assert(clen == plaintext_len + crypto_aead_chacha20poly1305_ietf_ABYTES);
}
/* BOLT #8:
* * `decryptWithAD(k, n, ad, ciphertext)`: outputs `decrypt(k, n, ad,
* ciphertext)`
* * where `decrypt` is an evaluation of `ChaCha20-Poly1305` (IETF
* variant) with the passed arguments, with nonce `n`
*/
static bool decrypt(const struct secret *k, u64 nonce,
const void *additional_data, size_t additional_data_len,
const void *ciphertext, size_t ciphertext_len,
void *output, size_t outputlen)
{
unsigned char npub[crypto_aead_chacha20poly1305_ietf_NPUBBYTES];
unsigned long long mlen;
assert(outputlen == ciphertext_len - crypto_aead_chacha20poly1305_ietf_ABYTES);
le64_nonce(npub, nonce);
BUILD_ASSERT(sizeof(*k) == crypto_aead_chacha20poly1305_ietf_KEYBYTES);
status_trace("# decryptWithAD(0x%s, 0x%s, 0x%s, 0x%s)",
tal_hexstr(trc, k, sizeof(*k)),
tal_hexstr(trc, npub, sizeof(npub)),
tal_hexstr(trc, additional_data, additional_data_len),
tal_hexstr(trc, ciphertext, ciphertext_len));
if (crypto_aead_chacha20poly1305_ietf_decrypt(output, &mlen, NULL,
memcheck(ciphertext, ciphertext_len),
ciphertext_len,
additional_data, additional_data_len,
npub, k->data) != 0)
return false;
assert(mlen == ciphertext_len - crypto_aead_chacha20poly1305_ietf_ABYTES);
return true;
}
static struct handshake *new_handshake(const tal_t *ctx,
const struct pubkey *id)
{
struct handshake *handshake = tal(ctx, struct handshake);
/* BOLT #8:
*
* Before the start of the first act, both sides initialize their
* per-sessions state as follows:
*
* 1. `h = SHA-256(protocolName)`
* * where `protocolName = "Noise_XK_secp256k1_ChaChaPoly_SHA256"`
* encoded as an ASCII string.
*/
sha256(&handshake->h, "Noise_XK_secp256k1_ChaChaPoly_SHA256",
strlen("Noise_XK_secp256k1_ChaChaPoly_SHA256"));
/* BOLT #8:
*
* 2. `ck = h`
*/
BUILD_ASSERT(sizeof(handshake->h) == sizeof(handshake->ck));
memcpy(&handshake->ck, &handshake->h, sizeof(handshake->ck));
status_trace("# ck=%s",
tal_hexstr(trc, &handshake->ck, sizeof(handshake->ck)));
/* BOLT #8:
*
* 3. `h = SHA-256(h || prologue)`
* * where `prologue` is the ASCII string: `lightning`.
*/
sha_mix_in(&handshake->h, "lightning", strlen("lightning"));
/* BOLT #8:
*
* As a concluding step, both sides mix the responder's public key
* into the handshake digest:
*
* * The initiating node mixes in the responding node's static public
* key serialized in Bitcoin's DER compressed format:
* * `h = SHA-256(h || rs.pub.serializeCompressed())`
*
* * The responding node mixes in their local static public key
* serialized in Bitcoin's DER compressed format:
* * `h = SHA-256(h || ls.pub.serializeCompressed())`
*/
sha_mix_in_key(&handshake->h, id);
status_trace("# h=%s",
tal_hexstr(trc, &handshake->h, sizeof(handshake->h)));
return handshake;
}
/* BOLT #8:
*
* Act One is sent from initiator to responder. During `Act One`, the
* initiator attempts to satisfy an implicit challenge by the responder. To
* complete this challenge, the initiator _must_ know the static public key of
* the responder.
*/
struct act_one {
u8 v;
u8 pubkey[PUBKEY_DER_LEN];
u8 tag[crypto_aead_chacha20poly1305_ietf_ABYTES];
};
/* BOLT #8: The handshake message is _exactly_ `50 bytes` */
#define ACT_ONE_SIZE 50 /* ARM's stupid ABI adds padding. */
static inline void check_act_one(const struct act_one *act1)
{
/* BOLT #8:
*
* : `1 byte` for the handshake version, `33 bytes` for the compressed
* ephemeral public key of the initiator, and `16 bytes` for the
* `poly1305` tag.
*/
BUILD_ASSERT(sizeof(act1->v) == 1);
BUILD_ASSERT(sizeof(act1->pubkey) == 33);
BUILD_ASSERT(sizeof(act1->tag) == 16);
}
static void act_one_initiator(struct handshake *h, int fd,
const struct pubkey *their_id)
{
struct act_one act1;
size_t len;
status_send_sync(towire_initr_act_one(h));
/* BOLT #8:
*
* **Sender Actions:**
*
* * `e = generateKey()`
*/
h->e = generate_key();
status_trace("e.priv: 0x%s",
tal_hexstr(trc, &h->e.priv, sizeof(h->e.priv)));
status_trace("e.pub: 0x%s",
type_to_string(trc, struct pubkey, &h->e.pub));
/* BOLT #8:
*
* * `h = SHA-256(h || e.pub.serializeCompressed())`
* * The newly generated ephemeral key is accumulated into our
* running handshake digest.
*/
sha_mix_in_key(&h->h, &h->e.pub);
status_trace("# h=0x%s", tal_hexstr(trc, &h->h, sizeof(h->h)));
/* BOLT #8:
*
* * `ss = ECDH(rs, e.priv)`
* * The initiator performs a `ECDH` between its newly generated
* ephemeral key with the remote node's static public key.
*/
if (!secp256k1_ecdh(secp256k1_ctx, h->ss.data,
&their_id->pubkey, h->e.priv.secret.data))
status_failed(STATUS_FAIL_PEER_BAD,
"WIRE_INITR_ACT1_BAD_ECDH_FOR_SS: %s", "");
status_trace("# ss=0x%s", tal_hexstr(trc, h->ss.data, sizeof(h->ss.data)));
/* BOLT #8:
*
* * `ck, temp_k1 = HKDF(ck, ss)`
* * This phase generates a new temporary encryption key
* which is used to generate the authenticating MAC.
*/
hkdf_two_keys(&h->ck, &h->temp_k, &h->ck, &h->ss, sizeof(h->ss));
status_trace("# ck,temp_k1=0x%s,0x%s",
tal_hexstr(trc, &h->ck, sizeof(h->ck)),
tal_hexstr(trc, &h->temp_k, sizeof(h->temp_k)));
/* BOLT #8:
*
* * `c = encryptWithAD(temp_k1, 0, h, zero)`
* * where `zero` is a zero-length plaintext
*/
encrypt_ad(&h->temp_k, 0, &h->h, sizeof(h->h), NULL, 0,
act1.tag, sizeof(act1.tag));
status_trace("# c=%s", tal_hexstr(trc, act1.tag, sizeof(act1.tag)));
/* BOLT #8:
*
* * `h = SHA-256(h || c)`
* * Finally, the generated ciphertext is accumulated into the
* authenticating handshake digest.
*/
sha_mix_in(&h->h, act1.tag, sizeof(act1.tag));
status_trace("# h=0x%s", tal_hexstr(trc, &h->h, sizeof(h->h)));
/* BOLT #8:
*
* * Send `m = 0 || e.pub.serializeCompressed() || c` to the responder over the network buffer.
*/
act1.v = 0;
len = sizeof(act1.pubkey);
secp256k1_ec_pubkey_serialize(secp256k1_ctx, act1.pubkey, &len,
&h->e.pub.pubkey,
SECP256K1_EC_COMPRESSED);
status_trace("output: 0x%s", tal_hexstr(trc, &act1, ACT_ONE_SIZE));
if (!write_all(fd, &act1, ACT_ONE_SIZE))
status_failed(STATUS_FAIL_PEER_IO,
"WIRE_INITR_ACT1_WRITE_FAILED: %s",
strerror(errno));
}
static void act_one_responder(struct handshake *h, int fd, struct pubkey *re)
{
struct act_one act1;
status_send_sync(towire_respr_act_one(h));
/* BOLT #8:
*
* * Read _exactly_ `50-bytes` from the network buffer.
*
* * Parse out the read message (`m`) into `v = m[0]`, `re =
* m[1:33]` and `c = m[34:]`
* * where `m[0]` is the _first_ byte of `m`, `m[1:33]` are the
* next `33` bytes of `m` and `m[34:]` is the last 16 bytes of
* `m`
*/
if (!read_all(fd, &act1, ACT_ONE_SIZE))
status_failed(STATUS_FAIL_PEER_IO,
"WIRE_RESPR_ACT1_READ_FAILED: %s",
strerror(errno));
status_trace("input: 0x%s", tal_hexstr(trc, &act1, ACT_ONE_SIZE));
/* BOLT #8:
*
* * If `v` is an unrecognized handshake version, then the responder
* MUST abort the connection attempt.
*/
if (act1.v != 0)
status_failed(STATUS_FAIL_PEER_BAD,
"WIRE_RESPR_ACT1_BAD_VERSION: %u", act1.v);
/* BOLT #8:
* * The raw bytes of the remote party's ephemeral public key
* (`e`) are to be deserialized into a point on the curve using
* affine coordinates as encoded by the key's serialized
* composed format.
*/
if (secp256k1_ec_pubkey_parse(secp256k1_ctx, &re->pubkey,
act1.pubkey, sizeof(act1.pubkey)) != 1)
status_failed(STATUS_FAIL_PEER_BAD,
"WIRE_RESPR_ACT1_BAD_PUBKEY: %s",
tal_hexstr(trc, &act1.pubkey,
sizeof(act1.pubkey)));
status_trace("# re=0x%s", type_to_string(trc, struct pubkey, re));
/* BOLT #8:
*
* * `h = SHA-256(h || re.serializeCompressed())`
* * Accumulate the initiator's ephemeral key into the
* authenticating handshake digest.
*/
sha_mix_in_key(&h->h, re);
status_trace("# h=0x%s", tal_hexstr(trc, &h->h, sizeof(h->h)));
/* BOLT #8:
* * `ss = ECDH(re, s.priv)`
* * The responder performs an `ECDH` between its static public
* key and the initiator's ephemeral public key.
*/
if (!hsm_do_ecdh(&h->ss, re))
status_failed(STATUS_FAIL_PEER_BAD,
"WIRE_RESPR_ACT1_BAD_HSM_ECDH: re=%s",
type_to_string(trc, struct pubkey, re));
status_trace("# ss=0x%s", tal_hexstr(trc, &h->ss, sizeof(h->ss)));
/* BOLT #8:
*
* * `ck, temp_k1 = HKDF(ck, ss)`
* * This phase generates a new temporary encryption key
* which will be used to shortly check the
* authenticating MAC.
*/
hkdf_two_keys(&h->ck, &h->temp_k, &h->ck, &h->ss, sizeof(h->ss));
status_trace("# ck,temp_k1=0x%s,0x%s",
tal_hexstr(trc, &h->ck, sizeof(h->ck)),
tal_hexstr(trc, &h->temp_k, sizeof(h->temp_k)));
/* BOLT #8:
*
* * `p = decryptWithAD(temp_k1, 0, h, c)`
* * If the MAC check in this operation fails, then the initiator
* does _not_ know our static public key. If so, then the
* responder MUST terminate the connection without any further
* messages.
*/
if (!decrypt(&h->temp_k, 0, &h->h, sizeof(h->h),
act1.tag, sizeof(act1.tag), NULL, 0))
status_failed(STATUS_FAIL_PEER_BAD,
"WIRE_RESPR_ACT1_BAD_TAG: re=%s ss=%s tag=%s",
type_to_string(trc, struct pubkey, re),
tal_hexstr(trc, &h->ss, sizeof(h->ss)),
tal_hexstr(trc, act1.tag, sizeof(act1.tag)));
/* BOLT #8:
*
* * `h = SHA-256(h || c)`
* * Mix the received ciphertext into the handshake digest. This
* step serves to ensure the payload wasn't modified by a MiTM.
*/
sha_mix_in(&h->h, act1.tag, sizeof(act1.tag));
status_trace("# h=0x%s", tal_hexstr(trc, &h->h, sizeof(h->h)));
}
/* BOLT #8:
*
* `Act Two` is sent from the responder to the initiator. `Act Two` will
* _only_ take place if `Act One` was successful. `Act One` was successful if
* the responder was able to properly decrypt and check the `MAC` of the tag
* sent at the end of `Act One`.
*/
struct act_two {
u8 v;
u8 pubkey[PUBKEY_DER_LEN];
u8 tag[crypto_aead_chacha20poly1305_ietf_ABYTES];
};
/* BOLT #8: The handshake is _exactly_ `50 bytes:` */
#define ACT_TWO_SIZE 50 /* ARM's stupid ABI adds padding. */
static inline void check_act_two(const struct act_two *act2)
{
/* BOLT #8:
* `1 byte` for the handshake version,
* `33 bytes` for the compressed ephemeral public key of the initiator, and
* `16 bytes` for the `poly1305` tag.
*/
BUILD_ASSERT(sizeof(act2->v) == 1);
BUILD_ASSERT(sizeof(act2->pubkey) == 33);
BUILD_ASSERT(sizeof(act2->tag) == 16);
}
static void act_two_responder(struct handshake *h, int fd,
const struct pubkey *re)
{
struct act_two act2;
size_t len;
status_send_sync(towire_respr_act_two(h));
/* BOLT #8:
*
* **Sender Actions:**
*
* * `e = generateKey()`
*/
h->e = generate_key();
status_trace("# e.pub=0x%s e.priv=0x%s",
type_to_string(trc, struct pubkey, &h->e.pub),
tal_hexstr(trc, &h->e.priv, sizeof(h->e.priv)));
/* BOLT #8:
*
* * `h = SHA-256(h || e.pub.serializeCompressed())`
* * The newly generated ephemeral key is accumulated into our
* running handshake digest.
*/
sha_mix_in_key(&h->h, &h->e.pub);
status_trace("# h=0x%s", tal_hexstr(trc, &h->h, sizeof(h->h)));
/* BOLT #8:
*
* * `ss = ECDH(re, e.priv)`
* * where `re` is the ephemeral key of the initiator which was
* received during `ActOne`.
*/
if (!secp256k1_ecdh(secp256k1_ctx, h->ss.data, &re->pubkey,
h->e.priv.secret.data))
status_failed(STATUS_FAIL_PEER_BAD,
"WIRE_RESPR_ACT2_BAD_ECDH_FOR_SS: re=%s e.priv=%s",
type_to_string(trc, struct pubkey, re),
tal_hexstr(trc, &h->e.priv, sizeof(h->e.priv)));
status_trace("# ss=0x%s", tal_hexstr(trc, &h->ss, sizeof(h->ss)));
/* BOLT #8:
*
* * `ck, temp_k2 = HKDF(ck, ss)`
* * This phase generates a new temporary encryption key
* which is used to generate the authenticating MAC.
*/
hkdf_two_keys(&h->ck, &h->temp_k, &h->ck, &h->ss, sizeof(h->ss));
status_trace("# ck,temp_k2=0x%s,0x%s",
tal_hexstr(trc, &h->ck, sizeof(h->ck)),
tal_hexstr(trc, &h->temp_k, sizeof(h->temp_k)));
/* BOLT #8:
*
* * `c = encryptWithAD(temp_k2, 0, h, zero)`
* * where `zero` is a zero-length plaintext
*/
encrypt_ad(&h->temp_k, 0, &h->h, sizeof(h->h), NULL, 0,
act2.tag, sizeof(act2.tag));
status_trace("# c=0x%s", tal_hexstr(trc, act2.tag, sizeof(act2.tag)));
/* BOLT #8:
*
* * `h = SHA-256(h || c)`
* * Finally, the generated ciphertext is accumulated into the
* authenticating handshake digest.
*/
sha_mix_in(&h->h, act2.tag, sizeof(act2.tag));
status_trace("# h=0x%s", tal_hexstr(trc, &h->h, sizeof(h->h)));
/* BOLT #8:
*
* * Send `m = 0 || e.pub.serializeCompressed() || c` to the initiator over the network buffer.
*/
act2.v = 0;
len = sizeof(act2.pubkey);
secp256k1_ec_pubkey_serialize(secp256k1_ctx, act2.pubkey, &len,
&h->e.pub.pubkey,
SECP256K1_EC_COMPRESSED);
status_trace("output: 0x%s", tal_hexstr(trc, &act2, ACT_TWO_SIZE));
if (!write_all(fd, &act2, ACT_TWO_SIZE))
status_failed(STATUS_FAIL_PEER_IO,
"WIRE_RESPR_ACT2_WRITE_FAILED: %s",
strerror(errno));
}
static void act_two_initiator(struct handshake *h, int fd, struct pubkey *re)
{
struct act_two act2;
status_send_sync(towire_initr_act_two(h));
/* BOLT #8:
*
* * Read _exactly_ `50-bytes` from the network buffer.
*
* * Parse out the read message (`m`) into `v = m[0]`, `re = m[1:33]`
* and `c = m[34:]`
* * where `m[0]` is the _first_ byte of `m`, `m[1:33]` are the
* next `33` bytes of `m` and `m[34:]` is the last 16 bytes of
* `m`
*/
if (!read_all(fd, &act2, ACT_TWO_SIZE))
status_failed(STATUS_FAIL_PEER_IO,
"WIRE_INITR_ACT2_READ_FAILED: %s",
strerror(errno));
status_trace("input: 0x%s", tal_hexstr(trc, &act2, ACT_TWO_SIZE));
/* BOLT #8:
*
* * If `v` is an unrecognized handshake version, then the responder
* MUST abort the connection attempt.
*/
if (act2.v != 0)
status_failed(STATUS_FAIL_PEER_BAD,
"WIRE_INITR_ACT2_BAD_VERSION: %u", act2.v);
/* BOLT #8:
*
* * The raw bytes of the remote party's ephemeral public key
* (`re`) are to be deserialized into a point on the curve using
* affine coordinates as encoded by the key's serialized
* composed format.
*/
if (secp256k1_ec_pubkey_parse(secp256k1_ctx, &re->pubkey,
act2.pubkey, sizeof(act2.pubkey)) != 1)
status_failed(STATUS_FAIL_PEER_BAD,
"WIRE_INITR_ACT2_BAD_PUBKEY: %s",
tal_hexstr(trc, &act2.pubkey,
sizeof(act2.pubkey)));
status_trace("# re=0x%s", type_to_string(trc, struct pubkey, re));
/* BOLT #8:
*
* * `h = SHA-256(h || re.serializeCompressed())`
*/
sha_mix_in_key(&h->h, re);
status_trace("# h=0x%s", tal_hexstr(trc, &h->h, sizeof(h->h)));
/* BOLT #8:
*
* * `ss = ECDH(re, e.priv)`
*/
if (!secp256k1_ecdh(secp256k1_ctx, h->ss.data, &re->pubkey,
h->e.priv.secret.data))
status_failed(STATUS_FAIL_PEER_BAD,
"WIRE_INITR_ACT2_BAD_ECDH_FOR_SS: re=%s e.priv=%s",
type_to_string(trc, struct pubkey, re),
tal_hexstr(trc, &h->e.priv, sizeof(h->e.priv)));
status_trace("# ss=0x%s", tal_hexstr(trc, &h->ss, sizeof(h->ss)));
/* BOLT #8:
*
* * `ck, temp_k2 = HKDF(ck, ss)`
* * This phase generates a new temporary encryption key
* which is used to generate the authenticating MAC.
*/
hkdf_two_keys(&h->ck, &h->temp_k, &h->ck, &h->ss, sizeof(h->ss));
status_trace("# ck,temp_k2=0x%s,0x%s",
tal_hexstr(trc, &h->ck, sizeof(h->ck)),
tal_hexstr(trc, &h->temp_k, sizeof(h->temp_k)));
/* BOLT #8:
*
* * `p = decryptWithAD(temp_k2, 0, h, c)`
* * If the MAC check in this operation fails, then the initiator
* MUST terminate the connection without any further messages.
*/
if (!decrypt(&h->temp_k, 0, &h->h, sizeof(h->h),
act2.tag, sizeof(act2.tag), NULL, 0))
status_failed(STATUS_FAIL_PEER_BAD,
"WIRE_INITR_ACT2_BAD_TAG: c=%s",
tal_hexstr(trc, act2.tag, sizeof(act2.tag)));
/* BOLT #8:
*
* * `h = SHA-256(h || c)`
* * Mix the received ciphertext into the handshake digest. This
* step serves to ensure the payload wasn't modified by a MiTM.
*/
sha_mix_in(&h->h, act2.tag, sizeof(act2.tag));
status_trace("# h=0x%s", tal_hexstr(trc, &h->h, sizeof(h->h)));
}
/* BOLT #8:
*
* `Act Three` is the final phase in the authenticated key agreement described
* in this section. This act is sent from the initiator to the responder as a
* final concluding step. `Act Three` is only executed `iff` `Act Two` was
* successful. During `Act Three`, the initiator transports its static public
* key to the responder encrypted with _strong_ forward secrecy using the
* accumulated `HKDF` derived secret key at this point of the handshake.
*/
struct act_three {
u8 v;
u8 ciphertext[PUBKEY_DER_LEN + crypto_aead_chacha20poly1305_ietf_ABYTES];
u8 tag[crypto_aead_chacha20poly1305_ietf_ABYTES];
};
/* BOLT #8: The handshake is _exactly_ `66 bytes` */
#define ACT_THREE_SIZE 66 /* ARM's stupid ABI adds padding. */
static inline void check_act_three(const struct act_three *act3)
{
/* BOLT #8:
*
* `1 byte` for the handshake version, `33 bytes` for the ephemeral
* public key encrypted with the `ChaCha20` stream cipher, `16 bytes`
* for the encrypted public key's tag generated via the `AEAD`
* construction, and `16 bytes` for a final authenticating tag.
*/
BUILD_ASSERT(sizeof(act3->v) == 1);
BUILD_ASSERT(sizeof(act3->ciphertext) == 33 + 16);
BUILD_ASSERT(sizeof(act3->tag) == 16);
}
static void act_three_initiator(struct handshake *h, int fd,
const struct pubkey *re,
const struct pubkey *my_id)
{
struct act_three act3;
u8 spub[PUBKEY_DER_LEN];
size_t len = sizeof(spub);
status_send_sync(towire_initr_act_three(h));
/* BOLT #8:
* * `c = encryptWithAD(temp_k2, 1, h, s.pub.serializeCompressed())`
* * where `s` is the static public key of the initiator.
*/
secp256k1_ec_pubkey_serialize(secp256k1_ctx, spub, &len,
&my_id->pubkey,
SECP256K1_EC_COMPRESSED);
encrypt_ad(&h->temp_k, 1, &h->h, sizeof(h->h), spub, sizeof(spub),
act3.ciphertext, sizeof(act3.ciphertext));
status_trace("# c=0x%s",
tal_hexstr(trc,act3.ciphertext,sizeof(act3.ciphertext)));
/* BOLT #8:
* * `h = SHA-256(h || c)`
*/
sha_mix_in(&h->h, act3.ciphertext, sizeof(act3.ciphertext));
status_trace("# h=0x%s", tal_hexstr(trc, &h->h, sizeof(h->h)));
/* BOLT #8:
*
* * `ss = ECDH(re, s.priv)`
* * where `re` is the ephemeral public key of the responder.
*
*/
if (!hsm_do_ecdh(&h->ss, re))
status_failed(STATUS_FAIL_PEER_BAD,
"WIRE_INITR_ACT3_BAD_HSM_ECDH: re=%s",
type_to_string(trc, struct pubkey, re));
status_trace("# ss=0x%s", tal_hexstr(trc, &h->ss, sizeof(h->ss)));
/* BOLT #8:
*
* * `ck, temp_k3 = HKDF(ck, ss)`
* * Mix the final intermediate shared secret into the running chaining key.
*/
hkdf_two_keys(&h->ck, &h->temp_k, &h->ck, &h->ss, sizeof(h->ss));
status_trace("# ck,temp_k3=0x%s,0x%s",
tal_hexstr(trc, &h->ck, sizeof(h->ck)),
tal_hexstr(trc, &h->temp_k, sizeof(h->temp_k)));
/* BOLT #8:
*
* * `t = encryptWithAD(temp_k3, 0, h, zero)`
* * where `zero` is a zero-length plaintext
*
*/
encrypt_ad(&h->temp_k, 0, &h->h, sizeof(h->h), NULL, 0,
act3.tag, sizeof(act3.tag));
status_trace("# t=0x%s",
tal_hexstr(trc, act3.tag, sizeof(act3.tag)));
/* BOLT #8:
*
* * Send `m = 0 || c || t` over the network buffer.
*
*/
act3.v = 0;
status_trace("output: 0x%s", tal_hexstr(trc, &act3, ACT_THREE_SIZE));
if (!write_all(fd, &act3, ACT_THREE_SIZE))
status_failed(STATUS_FAIL_PEER_IO,
"WIRE_INITR_ACT3_WRITE_FAILED: %s",
strerror(errno));
}
static void act_three_responder(struct handshake *h, int fd,
struct pubkey *their_id)
{
struct act_three act3;
u8 der[PUBKEY_DER_LEN];
status_send_sync(towire_respr_act_three(h));
/* BOLT #8:
*
* **Receiver Actions:**
*
* * Read _exactly_ `66-bytes` from the network buffer.
*/
if (!read_all(fd, &act3, ACT_THREE_SIZE))
status_failed(STATUS_FAIL_PEER_IO,
"WIRE_RESPR_ACT3_READ_FAILED: %s",
strerror(errno));
status_trace("input: 0x%s", tal_hexstr(trc, &act3, ACT_THREE_SIZE));
/* BOLT #8:
*
* * Parse out the read message (`m`) into `v = m[0]`, `c = m[1:49]` and `t = m[50:]`
*/
/* BOLT #8:
*
* * If `v` is an unrecognized handshake version, then the responder MUST
* abort the connection attempt.
*/
if (act3.v != 0)
status_failed(STATUS_FAIL_PEER_BAD,
"WIRE_RESPR_ACT3_BAD_VERSION: %u", act3.v);
/* BOLT #8:
*
* * `rs = decryptWithAD(temp_k2, 1, h, c)`
* * At this point, the responder has recovered the static public key of the
* initiator.
*/
if (!decrypt(&h->temp_k, 1, &h->h, sizeof(h->h),
act3.ciphertext, sizeof(act3.ciphertext),
der, sizeof(der)))
status_failed(STATUS_FAIL_PEER_BAD,
"WIRE_RESPR_ACT3_BAD_CIPHERTEXT: ciphertext=%s",
tal_hexstr(trc, act3.ciphertext,
sizeof(act3.ciphertext)));
status_trace("# rs=0x%s", tal_hexstr(trc, der, sizeof(der)));
if (secp256k1_ec_pubkey_parse(secp256k1_ctx, &their_id->pubkey,
der, sizeof(der)) != 1)
status_failed(STATUS_FAIL_PEER_BAD,
"WIRE_RESPR_ACT3_BAD_PUBKEY: %s",
tal_hexstr(trc, &der, sizeof(der)));
/* BOLT #8:
*
* * `h = SHA-256(h || c)`
*
*/
sha_mix_in(&h->h, act3.ciphertext, sizeof(act3.ciphertext));
status_trace("# h=0x%s", tal_hexstr(trc, &h->h, sizeof(h->h)));
/* BOLT #8:
*
* * `ss = ECDH(rs, e.priv)`
* * where `e` is the responder's original ephemeral key
*/
if (!secp256k1_ecdh(secp256k1_ctx, h->ss.data, &their_id->pubkey,
h->e.priv.secret.data))
status_failed(STATUS_FAIL_PEER_BAD,
"WIRE_RESPR_ACT3_BAD_ECDH_FOR_SS: rs=%s e.priv=%s",
type_to_string(trc, struct pubkey, their_id),
tal_hexstr(trc, &h->e.priv, sizeof(h->e.priv)));
status_trace("# ss=0x%s", tal_hexstr(trc, &h->ss, sizeof(h->ss)));
/* BOLT #8:
* * `ck, temp_k3 = HKDF(ck, ss)`
*/
hkdf_two_keys(&h->ck, &h->temp_k, &h->ck, &h->ss, sizeof(h->ss));
status_trace("# ck,temp_k3=0x%s,0x%s",
tal_hexstr(trc, &h->ck, sizeof(h->ck)),
tal_hexstr(trc, &h->temp_k, sizeof(h->temp_k)));
/* BOLT #8:
* * `p = decryptWithAD(temp_k3, 0, h, t)`
* * If the MAC check in this operation fails, then the responder MUST
* terminate the connection without any further messages.
*
*/
if (!decrypt(&h->temp_k, 0, &h->h, sizeof(h->h),
act3.tag, sizeof(act3.tag), NULL, 0))
status_failed(STATUS_FAIL_PEER_BAD,
"WIRE_RESPR_ACT3_BAD_TAG: temp_k3=%s h=%s t=%s",
tal_hexstr(trc, &h->temp_k, sizeof(h->temp_k)),
tal_hexstr(trc, &h->h, sizeof(h->h)),
tal_hexstr(trc, act3.tag, sizeof(act3.tag)));
}
static void initiator(int fd, const struct pubkey *my_id,
const struct pubkey *their_id,
struct secret *ck, struct secret *sk, struct secret *rk)
{
const tal_t *tmpctx = tal_tmpctx(NULL);
struct handshake *h = new_handshake(tmpctx, their_id);
struct pubkey re;
act_one_initiator(h, fd, their_id);
act_two_initiator(h, fd, &re);
act_three_initiator(h, fd, &re, my_id);
/* We need this for re-keying */
*ck = h->ck;
/* BOLT #8:
*
* * `sk, rk = HKDF(ck, zero)`
*
* * where `zero` is a zero-length plaintext, `sk` is the key to
* be used by the initiator to encrypt messages to the
* responder, and `rk` is the key to be used by the initiator
* to decrypt messages sent by the responder.
*
* * This step generates the final encryption keys to be used for
* sending and receiving messages for the duration of the
* session.
*/
hkdf_two_keys(sk, rk, ck, NULL, 0);
status_trace("output: sk,rk=0x%s,0x%s",
tal_hexstr(trc, sk, sizeof(*sk)),
tal_hexstr(trc, rk, sizeof(*rk)));
tal_free(tmpctx);
}
static void responder(int fd,
const struct pubkey *my_id,
struct pubkey *their_id,
struct secret *ck, struct secret *sk, struct secret *rk)
{
const tal_t *tmpctx = tal_tmpctx(NULL);
struct handshake *h = new_handshake(tmpctx, my_id);
struct pubkey re;
act_one_responder(h, fd, &re);
act_two_responder(h, fd, &re);
act_three_responder(h, fd, their_id);
/* We need this for re-keying */
*ck = h->ck;
/* BOLT #8:
*
* * `rk, sk = HKDF(ck, zero)`
* * where `zero` is a zero-length plaintext, `rk` is the key to
* be used by the responder to decrypt the messages sent by the
* initiator, and `sk` is the key to be used by the responder
* to encrypt messages to the initiator,
*
* * This step generates the final encryption keys to be used for
* sending and receiving messages for the duration of the
* session.
*/
hkdf_two_keys(rk, sk, ck, NULL, 0);
status_trace("output: rk,sk=0x%s,0x%s",
tal_hexstr(trc, rk, sizeof(*rk)),
tal_hexstr(trc, sk, sizeof(*sk)));
tal_free(tmpctx);
}
#ifndef TESTING
static void exchange_init(int fd, struct crypto_state *cs,
u8 **gfeatures, u8 **lfeatures)
{
/* BOLT #1:
*
* The sending node SHOULD use the minimum lengths required to
* represent the feature fields.
*
* The sender MUST set feature bits as defined in [BOLT
* #9](09-features.md), and MUST set to zero any feature bits that are
* not defined.
*/
u8 *localfeatures = tal_arrz(NULL, u8, 1);
localfeatures[0] = LOCALFEATURES_INITIAL_ROUTING_SYNC;
u8 *msg = towire_init(NULL, NULL, localfeatures);
localfeatures = tal_free(localfeatures);
if (!sync_crypto_write(cs, fd, msg))
status_failed(STATUS_FAIL_PEER_IO,
"PEER_WRITE_FAILED: %s", strerror(errno));
/* BOLT #1:
*
* Each node MUST wait to receive `init` before sending any other
* messages.
*/
msg = sync_crypto_read(NULL, cs, fd);
if (!msg)
status_failed(STATUS_FAIL_PEER_IO,
"INITMSG_READ_FAILED: %s", strerror(errno));
if (!fromwire_init(msg, msg, NULL, gfeatures, lfeatures))
status_failed(STATUS_FAIL_PEER_BAD, "bad init: %s",
tal_hex(msg, msg));
}
/* We expect hsmfd as fd 3, clientfd as 4 */
int main(int argc, char *argv[])
{
u8 *msg;
struct pubkey my_id, their_id;
int hsmfd = 3, clientfd = 4;
struct secret ck, rk, sk;
struct crypto_state cs;
u8 *gfeatures, *lfeatures;
if (argc == 2 && streq(argv[1], "--version")) {
printf("%s\n", version());
exit(0);
}
subdaemon_debug(argc, argv);
secp256k1_ctx = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY
| SECP256K1_CONTEXT_SIGN);
status_setup_sync(REQ_FD);
hsm_setup(hsmfd);
msg = wire_sync_read(NULL, REQ_FD);
if (fromwire_handshake_responder(msg, NULL, &my_id)) {
responder(clientfd, &my_id, &their_id, &ck, &sk, &rk);
cs.rn = cs.sn = 0;
cs.sk = sk;
cs.rk = rk;
cs.r_ck = cs.s_ck = ck;
exchange_init(clientfd, &cs, &gfeatures, &lfeatures);
wire_sync_write(REQ_FD,
towire_handshake_responder_reply(msg,
&their_id,
&cs,
gfeatures,
lfeatures));
} else if (fromwire_handshake_initiator(msg, NULL, &my_id,
&their_id)) {
initiator(clientfd, &my_id, &their_id, &ck, &sk, &rk);
cs.rn = cs.sn = 0;
cs.sk = sk;
cs.rk = rk;
cs.r_ck = cs.s_ck = ck;
exchange_init(clientfd, &cs, &gfeatures, &lfeatures);
wire_sync_write(REQ_FD,
towire_handshake_initiator_reply(msg, &cs,
gfeatures,
lfeatures));
} else
master_badmsg(WIRE_HANDSHAKE_INITIATOR, msg);
/* Hand back the fd. */
fdpass_send(REQ_FD, clientfd);
tal_free(msg);
return 0;
}
#endif /* TESTING */