feat: OTA-Trailer bauen und prüfen

src/util/nl_fwup_trailer.c

@@ -0,0 +1,74 @@
+#include "util/nl_fwup_trailer.h"
+
+#include <string.h>
+
+/* NB: This layout is mirrored in Python at tools/mkimage/nl_mkimage.py (Task 3),
+   since there are two languages involved. Keep both in sync. */
+
+#define OFF_MAGIC   0u
+#define OFF_VERSION 4u
+#define OFF_DEVICE  5u
+#define OFF_FW      21u
+#define OFF_SHA     37u
+
+static bool copy_field(uint8_t *dst, const char *src, uint32_t len)
+{
+    uint32_t n = (uint32_t)strlen(src);
+    if (n >= len)
+        return false;
+    memset(dst, 0, len);
+    memcpy(dst, src, n);
+    return true;
+}
+
+bool nl_trailer_build(uint8_t out[NL_TRAILER_SIZE], const char *device, const char *version, const uint8_t sha256[32])
+{
+    memset(out, 0xFF, NL_TRAILER_SIZE);
+    memcpy(&out[OFF_MAGIC], "NINL", 4);
+    out[OFF_VERSION] = NL_TRAILER_VERSION;
+    if (!copy_field(&out[OFF_DEVICE], device, NL_TRAILER_DEVICE_LEN) ||
+        !copy_field(&out[OFF_FW], version, NL_TRAILER_VERSION_LEN))
+        return false;
+    memcpy(&out[OFF_SHA], sha256, 32);
+    return true;
+}
+
+static bool terminated(const uint8_t *field, uint32_t len)
+{
+    for (uint32_t i = 0; i < len; i++)
+        if (field[i] == 0)
+            return true;
+    return false;
+}
+
+nl_trailer_err_t nl_trailer_verify(const uint8_t *tail, uint32_t tail_len, const char *device, const uint8_t sha256[32])
+{
+    if (tail == NULL || tail_len < NL_TRAILER_SIZE)
+        return NL_TRAILER_ERR_SIZE;
+    if (memcmp(&tail[OFF_MAGIC], "NINL", 4) != 0)
+        return NL_TRAILER_ERR_MAGIC;
+    if (tail[OFF_VERSION] != NL_TRAILER_VERSION)
+        return NL_TRAILER_ERR_VERSION;
+    if (!terminated(&tail[OFF_DEVICE], NL_TRAILER_DEVICE_LEN) ||
+        strcmp((const char *)&tail[OFF_DEVICE], device) != 0)
+        return NL_TRAILER_ERR_DEVICE;
+    if (memcmp(&tail[OFF_SHA], sha256, 32) != 0)
+        return NL_TRAILER_ERR_HASH;
+    return NL_TRAILER_OK;
+}
+
+void nl_trailer_version(const uint8_t *tail, char *dst)
+{
+    memcpy(dst, &tail[OFF_FW], NL_TRAILER_VERSION_LEN);
+    dst[NL_TRAILER_VERSION_LEN - 1] = '\0';
+}
+
+const char *nl_trailer_err_name(nl_trailer_err_t e)
+{
+    switch (e) {
+    case NL_TRAILER_ERR_DEVICE: return "device_mismatch";
+    case NL_TRAILER_ERR_HASH: return "hash";
+    case NL_TRAILER_OK: return NULL;
+    default: return "trailer";
+    }
+}

src/util/nl_fwup_trailer.h

@@ -0,0 +1,28 @@
+#ifndef NL_FWUP_TRAILER_H
+#define NL_FWUP_TRAILER_H
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#define NL_TRAILER_SIZE        512u
+#define NL_TRAILER_VERSION     1u
+#define NL_TRAILER_DEVICE_LEN  16u
+#define NL_TRAILER_VERSION_LEN 16u
+
+typedef enum {
+    NL_TRAILER_OK = 0,
+    NL_TRAILER_ERR_SIZE,
+    NL_TRAILER_ERR_MAGIC,
+    NL_TRAILER_ERR_VERSION,
+    NL_TRAILER_ERR_DEVICE,
+    NL_TRAILER_ERR_HASH
+} nl_trailer_err_t;
+
+/* "NINL" | version | device[16] | fw_version[16] | sha256[32] | 0xFF padding */
+bool nl_trailer_build(uint8_t out[NL_TRAILER_SIZE], const char *device, const char *version, const uint8_t sha256[32]);
+nl_trailer_err_t nl_trailer_verify(const uint8_t *tail, uint32_t tail_len, const char *device, const uint8_t sha256[32]);
+void nl_trailer_version(const uint8_t *tail, char *dst); /* dst: NL_TRAILER_VERSION_LEN bytes */
+/* Maps to the last_ota_error vocabulary; NULL for NL_TRAILER_OK. */
+const char *nl_trailer_err_name(nl_trailer_err_t e);
+
+#endif