feat(firmware): add Wi-Fi + TLS spike (Spike 6)

Standalone `wifi_tls` binary: station assoc, SNTP, then a validated
HTTPS GET to api.github.com against the esp-idf cert bundle. Gates
Spike 7 (gitoxide push). Creds come from firmware/.env via build.rs.

firmware/.env.example

@@ -0,0 +1,17 @@
+# Build-time config for the network spikes (6/7). Copy to `.env` and fill in.
+# `.env` is gitignored; `just` loads it automatically (dotenv-load) so the
+# values reach build.rs, which emits them as compile-time env for the binary.
+#
+#   cp .env.example .env   # then edit
+#   just flash-wifi        # Spike 6 — Wi-Fi + TLS
+#
+# Only the editor build (`just flash`) needs none of these.
+
+# Home Wi-Fi (2.4 GHz — the ESP32-S3 has no 5 GHz radio).
+TW_WIFI_SSID=your-ssid
+TW_WIFI_PASS=your-password
+# Note: the spike assumes WPA2-Personal. Open network → leave TW_WIFI_PASS empty.
+# A WPA3-only AP needs AuthMethod::WPA3Personal in src/bin/wifi_tls.rs.
+
+# Spike 7 (gitoxide push) will add: TW_REMOTE_URL, TW_GH_USER, TW_PAT,
+# TW_AUTHOR_NAME, TW_AUTHOR_EMAIL.

firmware/Cargo.toml

@@ -5,11 +5,23 @@ authors = ["Julien Calixte <juliencalixte@gmail.com>"]
 edition = "2024"
 resolver = "2"
 rust-version = "1.85"
+# Declare every binary explicitly so a spike program under src/bin/ doesn't get
+# an auto-discovered target with the default test harness (which trips up
+# rust-analyzer — see README "harness = false" note).
+autobins = false
 
 [[bin]]
 name = "firmware"
+path = "src/main.rs"
 harness = false # do not use the built-in cargo test harness -> resolve rust-analyzer errors
 
+# Spike 6 — Wi-Fi + TLS. Standalone bench program, kept separate from the
+# editor firmware. Flash with `just flash-wifi`.
+[[bin]]
+name = "wifi_tls"
+path = "src/bin/wifi_tls.rs"
+harness = false
+
 [profile.release]
 opt-level = "s"
 
@@ -28,6 +40,9 @@ esp-idf-svc = { version = "0.52.1", features = ["critical-section", "embassy-tim
 # Remove `generic-queue-8` if you plan to use `embassy-time` WITH `embassy-executor`
 embassy-time = { version = "0.5", features = ["generic-queue-8"] }
 embedded-graphics = "0.8"
+# Traits shared with esp-idf-svc (Spike 6 uses `embedded_svc::http::Method`).
+# Already in the tree via esp-idf-svc; pinned here so the spike names it directly.
+embedded-svc = "0.29"
 
 [build-dependencies]
 embuild = "0.33"

firmware/build.rs

@@ -21,6 +21,18 @@ fn main() {
         .unwrap_or_else(|| "unknown".into());
     println!("cargo:rustc-env=BUILD_GIT={git}");
     println!("cargo:rustc-env=BUILD_TIME={time}Z");
+
+    // Wi-Fi credentials for the network spikes (6/7) and, later, the runtime.
+    // Read at build time and emitted as compile-time env so a binary can pull
+    // them in with env!(). Empty when unset: the network spike checks at
+    // runtime and prints a clear message, so the *editor* build never has to
+    // carry Wi-Fi creds. Source them from firmware/.env (loaded by `just`).
+    for var in ["TW_WIFI_SSID", "TW_WIFI_PASS"] {
+        let val = std::env::var(var).unwrap_or_default();
+        println!("cargo:rustc-env={var}={val}");
+        println!("cargo:rerun-if-env-changed={var}");
+    }
+
     // Pointing rerun-if-changed at a file that never exists forces this
     // script to rerun on every build, keeping BUILD_TIME fresh.
     println!("cargo:rerun-if-changed=.force-build-stamp");

firmware/justfile

@@ -2,8 +2,13 @@
 # Recipes source ~/export-esp.sh themselves (LIBCLANG_PATH + Xtensa GCC),
 # so no per-shell setup is needed before calling just.
 
+# Load firmware/.env (Wi-Fi creds for the network spikes) into recipe env.
+# Absent .env is fine — the editor build ignores TW_* entirely.
+set dotenv-load := true
+
 esp_env := ". ~/export-esp.sh &&"
 elf := "target/xtensa-esp32s3-espidf/release/firmware"
+elf_wifi := "target/xtensa-esp32s3-espidf/release/wifi_tls"
 
 # list recipes
 default:
@@ -11,16 +16,28 @@ default:
 
 # compile (release)
 build:
-    {{esp_env}} cargo build --release
+    {{esp_env}} cargo build --release --bin firmware
 
 # build + flash + open serial monitor
 flash:
-    {{esp_env}} cargo run --release
+    {{esp_env}} cargo run --release --bin firmware
 
 # serial monitor only, with decoded backtraces
 monitor:
     espflash monitor --elf {{elf}}
 
+# Spike 6 — build the Wi-Fi + TLS spike (needs TW_WIFI_SSID / TW_WIFI_PASS in .env)
+build-wifi:
+    {{esp_env}} cargo build --release --bin wifi_tls
+
+# Spike 6 — flash + monitor the Wi-Fi + TLS spike
+flash-wifi:
+    {{esp_env}} cargo run --release --bin wifi_tls
+
+# serial monitor for the Wi-Fi spike, with decoded backtraces
+monitor-wifi:
+    espflash monitor --elf {{elf_wifi}}
+
 # detect board, print chip/MAC/flash size
 info:
     espflash board-info

firmware/sdkconfig.defaults

@@ -1,12 +1,21 @@
 # Rust often needs a bit of an extra main task stack size compared to C (the default is 3K)
-# You might have to increase this further if you allocate large stack variables in the main task
-CONFIG_ESP_MAIN_TASK_STACK_SIZE=8192
+# You might have to increase this further if you allocate large stack variables in the main task.
+# Bumped for the TLS handshake (Spike 6): mbedtls runs on the calling task and
+# wants several KB of stack on top of the app's own usage.
+CONFIG_ESP_MAIN_TASK_STACK_SIZE=12288
 
 # Increase a bit these stack sizes as they are also a bit too small by default
 CONFIG_ESP_SYSTEM_EVENT_TASK_STACK_SIZE=4096
 CONFIG_FREERTOS_IDLE_TASK_STACKSIZE=4096
 
-# You might have to increase this further if you spawn your own Rust threads 
-# that allocate large stack variables; or better yet - use 
+# You might have to increase this further if you spawn your own Rust threads
+# that allocate large stack variables; or better yet - use
 # `std::thread::Builder::new().stack_size(XXX)` for spawning
 CONFIG_PTHREAD_TASK_STACK_SIZE_DEFAULT=4096
+
+# TLS trust store (Spike 6 — Wi-Fi + TLS, the gate for Spike 7 gitoxide push).
+# The certificate bundle backs esp_crt_bundle_attach so an HTTPS GET to
+# api.github.com validates against real roots. FULL rather than the common
+# subset so a less common CA in the chain can't surprise us on the bench.
+CONFIG_MBEDTLS_CERTIFICATE_BUNDLE=y
+CONFIG_MBEDTLS_CERTIFICATE_BUNDLE_DEFAULT_FULL=y

firmware/src/bin/wifi_tls.rs

@@ -0,0 +1,202 @@
+//! Spike 6 — Wi-Fi + TLS.
+//!
+//! A small standalone bench program (separate binary from the editor firmware)
+//! that proves the networking + TLS stack end to end:
+//!
+//!   1. Bring up the station and associate with the home AP.
+//!   2. Sync the clock over SNTP — mbedtls checks the server cert's
+//!      not-before/not-after against wall time, so without this the 1970 RTC
+//!      makes every handshake fail with "certificate is not valid yet".
+//!   3. HTTPS GET https://api.github.com/ with cert-chain validation against
+//!      the esp-idf certificate bundle (esp_crt_bundle_attach), and read the
+//!      response body.
+//!
+//! A validated GET is the whole point: it's the gate for Spike 7 (gitoxide
+//! push over HTTPS + PAT). Free heap is logged around the handshake because
+//! TLS heap pressure on this chip is a top-3 watched risk (see qfd.md §6).
+//!
+//! Credentials come from build-time env (build.rs → env!): set TW_WIFI_SSID /
+//! TW_WIFI_PASS in firmware/.env and run `just flash-wifi`.
+
+use std::time::{Instant, SystemTime, UNIX_EPOCH};
+
+use anyhow::{bail, Context, Result};
+use embedded_svc::http::Method;
+use esp_idf_svc::eventloop::EspSystemEventLoop;
+use esp_idf_svc::hal::delay::FreeRtos;
+use esp_idf_svc::hal::peripherals::Peripherals;
+use esp_idf_svc::http::client::{Configuration as HttpConfig, EspHttpConnection};
+use esp_idf_svc::nvs::EspDefaultNvsPartition;
+use esp_idf_svc::sntp::{EspSntp, SyncStatus};
+use esp_idf_svc::wifi::{AuthMethod, BlockingWifi, ClientConfiguration, Configuration, EspWifi};
+
+/// Injected by build.rs so serial output identifies the exact build.
+const BUILD_TAG: &str = concat!("build ", env!("BUILD_TIME"), " @", env!("BUILD_GIT"));
+
+/// Wi-Fi credentials, baked in at build time from firmware/.env. Empty when
+/// unset — checked at runtime so the editor build never depends on them.
+const WIFI_SSID: &str = env!("TW_WIFI_SSID");
+const WIFI_PASS: &str = env!("TW_WIFI_PASS");
+
+/// The validated endpoint. Root of the GitHub REST API: returns JSON, needs a
+/// User-Agent, and is served over a normal public CA chain — a faithful
+/// stand-in for the api.github.com host Spike 7 will push through.
+const TEST_URL: &str = "https://api.github.com/";
+
+/// SNTP first-sync budget. Home networks resolve pool.ntp.org and answer well
+/// within this; failing past it is a real problem worth surfacing.
+const SNTP_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(20);
+
+fn main() -> Result<()> {
+    // Required once before any esp-idf-svc call; some runtime patches only link
+    // if this symbol is referenced. See esp-idf-template#71.
+    esp_idf_svc::sys::link_patches();
+    esp_idf_svc::log::EspLogger::initialize_default();
+
+    log::info!("Typoena — Spike 6 (Wi-Fi + TLS), {BUILD_TAG}");
+
+    match run() {
+        Ok(()) => log::info!("✅ Spike 6 complete — Wi-Fi assoc + SNTP + validated HTTPS GET"),
+        Err(e) => log::error!("❌ Spike 6 failed: {e:?}"),
+    }
+
+    // Idle instead of returning, so the result stays on screen and Wi-Fi/other
+    // tasks keep running for inspection rather than the app winding down.
+    loop {
+        FreeRtos::delay_ms(1000);
+    }
+}
+
+fn run() -> Result<()> {
+    if WIFI_SSID.is_empty() {
+        bail!("TW_WIFI_SSID is empty — set it in firmware/.env (see .env.example) and rebuild");
+    }
+
+    let peripherals = Peripherals::take()?;
+    let sys_loop = EspSystemEventLoop::take()?;
+    let nvs = EspDefaultNvsPartition::take()?;
+
+    let mut wifi = BlockingWifi::wrap(
+        EspWifi::new(peripherals.modem, sys_loop.clone(), Some(nvs))?,
+        sys_loop,
+    )?;
+
+    connect_wifi(&mut wifi)?;
+    let ip = wifi.wifi().sta_netif().get_ip_info()?;
+    log::info!("Wi-Fi up — IP {}, GW {}", ip.ip, ip.subnet.gateway);
+
+    sync_clock()?;
+
+    https_get(TEST_URL)?;
+    Ok(())
+}
+
+/// Associate with the configured AP and wait for the netif (DHCP) to come up.
+fn connect_wifi(wifi: &mut BlockingWifi<EspWifi<'static>>) -> Result<()> {
+    // Open network → no auth; otherwise WPA2-Personal (see .env.example for WPA3).
+    let auth_method = if WIFI_PASS.is_empty() {
+        AuthMethod::None
+    } else {
+        AuthMethod::WPA2Personal
+    };
+
+    wifi.set_configuration(&Configuration::Client(ClientConfiguration {
+        ssid: WIFI_SSID
+            .try_into()
+            .ok()
+            .context("SSID longer than 32 bytes")?,
+        password: WIFI_PASS
+            .try_into()
+            .ok()
+            .context("password longer than 64 bytes")?,
+        auth_method,
+        ..Default::default()
+    }))?;
+
+    wifi.start()?;
+    log::info!("associating with \"{WIFI_SSID}\"…");
+    wifi.connect().context("Wi-Fi association failed")?;
+    wifi.wait_netif_up().context("DHCP / netif never came up")?;
+    Ok(())
+}
+
+/// Kick off SNTP and block until the first sync (or time out). Required before
+/// TLS: cert validity is checked against wall time.
+fn sync_clock() -> Result<()> {
+    let sntp = EspSntp::new_default()?;
+    log::info!("SNTP started, waiting for first sync…");
+
+    let start = Instant::now();
+    while sntp.get_sync_status() != SyncStatus::Completed {
+        if start.elapsed() >= SNTP_TIMEOUT {
+            bail!("SNTP did not sync within {SNTP_TIMEOUT:?} — TLS cert validity would fail");
+        }
+        FreeRtos::delay_ms(100);
+    }
+
+    let unix = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .map(|d| d.as_secs())
+        .unwrap_or(0);
+    // A synced clock lands well past this (2023-11-14); anything below means the
+    // RTC never actually advanced and TLS would reject on validity.
+    if unix < 1_700_000_000 {
+        bail!("clock still at {unix} after SNTP sync — refusing TLS with a bad wall clock");
+    }
+    log::info!("clock synced — unix {unix}");
+    Ok(())
+}
+
+/// HTTPS GET with cert-chain validation against the esp-idf certificate bundle.
+/// Logs status, the first chunk of the body, and free heap around the request.
+fn https_get(url: &str) -> Result<()> {
+    let heap_before = unsafe { esp_idf_svc::sys::esp_get_free_heap_size() };
+
+    let mut conn = EspHttpConnection::new(&HttpConfig {
+        // Validate the server chain against the bundled roots. If this is None,
+        // the handshake skips verification — which would defeat the spike.
+        crt_bundle_attach: Some(esp_idf_svc::sys::esp_crt_bundle_attach),
+        ..Default::default()
+    })
+    .context("creating the HTTPS connection (TLS init)")?;
+
+    // GitHub rejects requests without a User-Agent.
+    let headers = [
+        ("User-Agent", "typoena-spike6"),
+        ("Accept", "application/vnd.github+json"),
+    ];
+    conn.initiate_request(Method::Get, url, &headers)
+        .context("TLS handshake / request send failed")?;
+    conn.initiate_response()?;
+
+    let status = conn.status();
+    log::info!("HTTPS GET {url} → {status}");
+
+    // Preview the first chunk, then drain the rest so we log the real byte count
+    // (proves the encrypted stream reads back cleanly, not just the handshake).
+    let mut buf = [0u8; 512];
+    let first = conn.read(&mut buf)?;
+    log::info!(
+        "body[..{first}]: {}",
+        String::from_utf8_lossy(&buf[..first]).replace('\n', " ")
+    );
+    let mut total = first;
+    loop {
+        let n = conn.read(&mut buf)?;
+        if n == 0 {
+            break;
+        }
+        total += n;
+    }
+
+    let heap_after = unsafe { esp_idf_svc::sys::esp_get_free_heap_size() };
+    log::info!(
+        "read {total} bytes; free heap {heap_before} → {heap_after} (Δ {} B during TLS)",
+        heap_before as i64 - heap_after as i64
+    );
+
+    if !(200..300).contains(&status) {
+        bail!("unexpected HTTP status {status} (TLS validated, but the request was not OK)");
+    }
+    Ok(())
+}