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[noise] Trim the resume header comments

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This commit is contained in:
J. Nick Koston
2026-08-24 19:41:53 -05:00
parent a9b1fc361b
commit cff5cf7ad5
1 changed files with 8 additions and 14 deletions
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esphome/components/noise/noise_resume.h
+8 -14
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@@ -25,10 +25,8 @@ namespace esphome::noise {
* confirm_mac = HKDF(secret, "confirm" || client_nonce || server_nonce).out1[:16]
* k_c2d, k_d2c = HKDF(secret, "keys" || client_nonce || server_nonce || SHA256(prologue))
*
* A client that offers a ticket must hold handshake message 1 back until
* the ServerHello declines: an accept switches the responder straight to
* transport mode. A resumed session has no ephemeral DH; its keys come
* from the single-use ticket secret, which both sides wipe on redemption.
* An offering client sends handshake message 1 only after a decline.
* Resumed sessions have no ephemeral DH; the ticket is wiped on use.
*/
static constexpr uint8_t RESUME_OFFER_VERSION = 0x01;
@@ -72,11 +70,9 @@ class ResumeTicketCache {
/// Forget every ticket (PSK change).
void clear();
// Realistically one or two controllers hold a ticket at a time. Issue is
// round robin, so three steady clients keep evicting each other and all
// fall back to full handshakes.
// Round robin; more clients than slots thrash and fall back to full handshakes
static constexpr uint8_t SLOTS = 2;
static_assert(SLOTS <= 8, "used_mask_ is a uint8_t bitmask");
static_assert(SLOTS <= 8, "used_mask_ is uint8_t");
protected:
ResumeTicket slots_[SLOTS];
@@ -94,9 +90,7 @@ static constexpr size_t RESUME_KDF_MAX_DATA =
sizeof(RESUME_LABEL_KEYS) - 1 + RESUME_NONCE_SIZE + RESUME_NONCE_SIZE + 32;
/// Noise-construction HKDF-SHA256 keyed with the ticket secret over
/// label || a || b [|| SHA256(hash_in)]. out2 == nullptr means MAC only.
/// label_len + a_len + b_len (+ 32 with hash_in) must not exceed
/// RESUME_KDF_MAX_DATA; the wrappers below static_assert their inputs.
/// label || a || b [|| SHA256(hash_in)], at most RESUME_KDF_MAX_DATA. out2 == nullptr means MAC only.
bool resume_kdf(const uint8_t *secret, const char *label, size_t label_len, const uint8_t *a, size_t a_len,
const uint8_t *b, size_t b_len, const uint8_t *hash_in, size_t hash_in_len, uint8_t *out1,
size_t out1_len, uint8_t *out2);
@@ -106,7 +100,7 @@ bool resume_kdf(const uint8_t *secret, const char *label, size_t label_len, cons
inline bool resume_compute_offer_mac(const uint8_t *secret, const uint8_t *session_id, const uint8_t *client_nonce,
uint8_t *out_mac) {
static_assert(sizeof(RESUME_LABEL_OFFER) - 1 + RESUME_SESSION_ID_SIZE + RESUME_NONCE_SIZE <= RESUME_KDF_MAX_DATA,
"offer MAC input must fit the KDF buffer");
"KDF buffer");
return resume_kdf(secret, RESUME_LABEL_OFFER, sizeof(RESUME_LABEL_OFFER) - 1, session_id, RESUME_SESSION_ID_SIZE,
client_nonce, RESUME_NONCE_SIZE, nullptr, 0, out_mac, RESUME_MAC_SIZE, nullptr);
}
@@ -115,7 +109,7 @@ inline bool resume_compute_offer_mac(const uint8_t *secret, const uint8_t *sessi
inline bool resume_compute_confirm_mac(const uint8_t *secret, const uint8_t *client_nonce, const uint8_t *server_nonce,
uint8_t *out_mac) {
static_assert(sizeof(RESUME_LABEL_CONFIRM) - 1 + RESUME_NONCE_SIZE + RESUME_NONCE_SIZE <= RESUME_KDF_MAX_DATA,
"confirm MAC input must fit the KDF buffer");
"KDF buffer");
return resume_kdf(secret, RESUME_LABEL_CONFIRM, sizeof(RESUME_LABEL_CONFIRM) - 1, client_nonce, RESUME_NONCE_SIZE,
server_nonce, RESUME_NONCE_SIZE, nullptr, 0, out_mac, RESUME_MAC_SIZE, nullptr);
}
@@ -125,7 +119,7 @@ inline bool resume_compute_confirm_mac(const uint8_t *secret, const uint8_t *cli
inline bool resume_derive_keys(const uint8_t *secret, const uint8_t *client_nonce, const uint8_t *server_nonce,
const uint8_t *prologue, size_t prologue_len, uint8_t *k_c2d, uint8_t *k_d2c) {
static_assert(sizeof(RESUME_LABEL_KEYS) - 1 + RESUME_NONCE_SIZE + RESUME_NONCE_SIZE + 32 <= RESUME_KDF_MAX_DATA,
"key derivation input must fit the KDF buffer");
"KDF buffer");
return resume_kdf(secret, RESUME_LABEL_KEYS, sizeof(RESUME_LABEL_KEYS) - 1, client_nonce, RESUME_NONCE_SIZE,
server_nonce, RESUME_NONCE_SIZE, prologue, prologue_len, k_c2d, 32, k_d2c);
}