boardloader, bootloader: check image contents against hashes in the header

embed/boardloader/main.c

@@ -182,6 +182,10 @@ int main(void)
         load_image_header((const uint8_t *)BOOTLOADER_START, BOOTLOADER_IMAGE_MAGIC, BOOTLOADER_IMAGE_MAXSIZE, BOARDLOADER_KEY_M, BOARDLOADER_KEY_N, BOARDLOADER_KEYS, &hdr),
         "invalid bootloader header");
 
+    ensure(
+        check_image_contents(&hdr, (const uint8_t *)BOOTLOADER_START, 1),
+        "invalid bootloader hash");
+
     jump_to(BOOTLOADER_START + IMAGE_HEADER_SIZE);
 
     return 0;

embed/bootloader/main.c

@@ -327,6 +327,10 @@ int main(void)
         load_image_header((const uint8_t *)(FIRMWARE_START + vhdr.hdrlen), FIRMWARE_IMAGE_MAGIC, FIRMWARE_IMAGE_MAXSIZE, vhdr.vsig_m, vhdr.vsig_n, vhdr.vpub, &hdr),
         "invalid firmware header");
 
+    ensure(
+        check_image_contents(&hdr, (const uint8_t *)(FIRMWARE_START + vhdr.hdrlen), 6),
+        "invalid firmware hash");
+
     display_vendor(vhdr.vimg, (const char *)vhdr.vstr, vhdr.vstr_len, hdr.version);
     display_fade(0, BACKLIGHT_NORMAL, 1000);
     if (vhdr.vtrust < 50) {

embed/trezorhal/image.c

@@ -128,3 +128,33 @@ bool load_vendor_header(const uint8_t * const data, uint8_t key_m, uint8_t key_n
 
     return 0 == ed25519_sign_open(hash, BLAKE2S_DIGEST_LENGTH, pub, *(const ed25519_signature *)vhdr->sig);
 }
+
+static bool check_hash(const uint8_t * const hash, const uint8_t * const data, int len)
+{
+    uint8_t h[BLAKE2S_DIGEST_LENGTH];
+    blake2s(data, len, h, BLAKE2S_DIGEST_LENGTH);
+    return 0 == memcmp(h, hash, BLAKE2S_DIGEST_LENGTH);
+}
+
+#define MIN(a,b) ((a) < (b) ? (a) : (b))
+
+bool check_image_contents(const image_header * const hdr, const uint8_t * const data, int maxblocks)
+{
+    int remaining = hdr->codelen;
+    if (!check_hash(hdr->hashes, data + IMAGE_HEADER_SIZE, MIN(remaining, IMAGE_CHUNK_SIZE - IMAGE_HEADER_SIZE))) {
+        return false;
+    }
+    int block = 1;
+    remaining -= IMAGE_CHUNK_SIZE - IMAGE_HEADER_SIZE;
+    while (remaining > 0) {
+        if (block >= maxblocks) {
+            return false;
+        }
+        if (!check_hash(hdr->hashes + block * 32, data + block * IMAGE_CHUNK_SIZE, MIN(remaining, IMAGE_CHUNK_SIZE))) {
+            return false;
+        }
+        block++;
+        remaining -= IMAGE_CHUNK_SIZE;
+    }
+    return true;
+}

embed/trezorhal/image.h

@@ -48,4 +48,6 @@ bool load_image_header(const uint8_t * const data, const uint32_t magic, const u
 
 bool load_vendor_header(const uint8_t * const data, uint8_t key_m, uint8_t key_n, const uint8_t * const *keys, vendor_header * const vhdr);
 
+bool check_image_contents(const image_header * const hdr, const uint8_t * const data, int maxblocks);
+
 #endif