boot: Add tlv query for protected region

Add a query to the TLV iterator that will indicate if the currently iterated TLV
entry was found in the protected region or not.

Signed-off-by: David Brown <david.brown@linaro.org>

Author: d3zd3z

boot/bootutil/include/bootutil/image.h

@@ -186,6 +186,7 @@ int bootutil_tlv_iter_begin(struct image_tlv_iter *it,
                             bool prot);
 int bootutil_tlv_iter_next(struct image_tlv_iter *it, uint32_t *off,
                            uint16_t *len, uint16_t *type);
+int bootutil_tlv_iter_is_prot(struct image_tlv_iter *it, uint32_t off);
 
 int32_t bootutil_get_img_security_cnt(struct image_header *hdr,
                                       const struct flash_area *fap,

boot/bootutil/src/tlv.c

@@ -132,3 +132,23 @@ bootutil_tlv_iter_next(struct image_tlv_iter *it, uint32_t *off, uint16_t *len,
 
     return 1;
 }
+
+/*
+ * Return if a TLV entry is in the protected area.
+ *
+ * @param it The image TLV iterator struct
+ * @param off The offset of the entry to check.
+ *
+ * @return 0 if this TLV iterator entry is not protected.
+ *         1 if this TLV iterator entry is in the protected region
+ *         -1 if the iterator is invalid.
+ */
+int
+bootutil_tlv_iter_is_prot(struct image_tlv_iter *it, uint32_t off)
+{
+    if (it == NULL || it->hdr == NULL || it->fap == NULL) {
+        return -1;
+    }
+
+    return off < it->prot_end;
+}