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[noise] Inline the spare slot check, keep the slot empty if the base multiply fails

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has_spare_ephemeral() is polled every api loop tick, so the flag is now
an extern and the accessor lives in the header.
This commit is contained in:
J. Nick Koston
2026-09-07 12:21:04 +02:00
parent 0f6c266cd7
commit 5747c736c2
2 changed files with 8 additions and 5 deletions
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esphome/components/noise/noise.cpp
+5 -4
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@@ -28,9 +28,7 @@ void NoiseContext::load_psk(psk_t &out) const {
#ifdef USE_API_NOISE
static uint8_t spare_ephemeral[EPHEMERAL_KEYPAIR_SIZE]; // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
static bool spare_ephemeral_ready = false; // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
bool has_spare_ephemeral() { return spare_ephemeral_ready; }
bool spare_ephemeral_ready = false; // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
void prepare_spare_ephemeral() {
// A partial fill must never look ready
@@ -44,7 +42,10 @@ void prepare_spare_ephemeral() {
}
private_key[0] &= 0xF8;
private_key[EPHEMERAL_PRIVATE_KEY_SIZE - 1] = (private_key[EPHEMERAL_PRIVATE_KEY_SIZE - 1] & 0x7F) | 0x40;
crypto_scalarmult_curve25519_base(public_key, private_key);
if (crypto_scalarmult_curve25519_base(public_key, private_key) != 0) {
sodium_memzero(spare_ephemeral, EPHEMERAL_KEYPAIR_SIZE);
return;
}
spare_ephemeral_ready = true;
}
esphome/components/noise/noise.h
+3 -1
View File
@@ -48,7 +48,9 @@ using ephemeral_keypair_t = std::array<uint8_t, EPHEMERAL_KEYPAIR_SIZE>;
// One responder ephemeral key pair generated ahead of time (about 60 ms on
// ESP8266), refilled by the api server while idle, shared by every noise
// transport; an empty slot means the handshake generates its own key.
bool has_spare_ephemeral();
extern bool spare_ephemeral_ready; // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
// Polled every api loop tick, so it must inline
inline bool has_spare_ephemeral() { return spare_ephemeral_ready; }
/// Fill the slot; blocks for the base point multiply
void prepare_spare_ephemeral();
/// Move the slot into out and empty it; false (out untouched) when empty