sign: normalize short read failures

Return a consistent failure code on encrypt-key short reads and initialize final-swap ret to 0.

F/CI

Author: danielinux

src/update_flash.c

@@ -434,7 +434,7 @@ static int RAMFUNCTION wolfBoot_swap_and_final_erase(int resume)
     uintptr_t tmpBootPos = WOLFBOOT_PARTITION_SIZE - eraseLen -
         WOLFBOOT_SECTOR_SIZE;
     uint32_t tmpBuffer[TRAILER_OFFSET_WORDS + 1];
-    int ret;
+    int ret = 0;
 
     /* open partitions (ignore failure) */
     wolfBoot_open_image(boot, PART_BOOT);

tools/keytools/sign.c

@@ -2034,11 +2034,13 @@ static int make_header_ex(int is_diff, uint8_t *pubkey, uint32_t pubkey_sz,
         ret = (int)fread(key, 1, keySz, fek);
         if (ret != keySz) {
             fprintf(stderr, "Error reading key from %s\n", CMD.encrypt_key_file);
+            ret = -1;
             goto failure;
         }
         ret = (int)fread(iv, 1, ivSz, fek);
         if (ret != ivSz) {
             fprintf(stderr, "Error reading IV from %s\n", CMD.encrypt_key_file);
+            ret = -1;
             goto failure;
         }
         fclose(fek);