Initial version

Signed-off-by: Joakim Bech <joakim.bech@linaro.org>

2 files changed, 89 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..b948985
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+*.swp
+*.pyc
diff --git a/patch_mynewt_img.py b/patch_mynewt_img.py
new file mode 100755
index 0000000..26d2b4d
--- /dev/null
+++ b/patch_mynewt_img.py
@@ -0,0 +1,87 @@
+#!/usr/bin/python2
+import hashlib
+import mmap
+import os
+import struct
+import sys
+from ctypes import *
+
+def patch_header(img):
+    image_size = os.path.getsize(img + ".elf.bin")
+    print("Image size (bin): %d" % image_size)
+
+    try:
+        with open(img + ".img", "r+b") as f:
+            print("[*] Loading : {0}".format(img))
+
+            # Patch the header size (Hardcoded to 0x80)
+            f.seek(8)
+            f.write('\x80\x00')
+
+            # Patch the image size, start by convert int to hex string.
+            image_size = struct.pack('i', image_size)
+            f.seek(12)
+            f.write(image_size)
+
+            # 
+            f.close()
+    except IOError:
+        print("[*] Cannot open {0} (!) ".format(img))
+
+
+def extend_image(img):
+    try:
+        with open(img + ".img", "r+b") as f:
+            print("[*] Loading : {0}".format(img))
+            mm=mmap.mmap(f.fileno(),0)
+            f.write(mm[0:32] + ('\xFF' * 0x60) + mm[33:])
+            f.close()
+    except IOError:
+        print("[*] Cannot open {0} (!) ".format(img))
+
+
+def calculate_hash(img):
+    sha256 = hashlib.sha256()
+    with open(img + ".img", "rb") as f:
+        for chunk in iter(lambda: f.read(4096), b""):
+            sha256.update(chunk)
+    return sha256.hexdigest()
+
+
+def append_hash(img, digest):
+    with open(img + ".img", "ab") as f:
+
+        # Start by settings the TLV type
+        # https://github.com/apache/incubator-mynewt-newt/blob/master/newt/image/image.go#L109-L116
+        tlv_type = struct.pack('b', 1) # 1: SHA256, 2: RSA2048, 3: ECDSA224
+
+        # Next 1 byte padding
+        tlv_pad = '\x00'
+
+        # Finally the size of the TLV, for SHA256 that is 32 bytes
+        tlv_len = struct.pack('h', 0x20)
+        
+        f.write(tlv_type)
+        f.write(tlv_pad)
+        f.write(tlv_len)
+        f.write(digest.decode('hex'))
+        f.close()
+
+def main(img):
+    patch_header(img)
+    extend_image(img)
+
+    digest = calculate_hash(img)
+    print("Hash of intermediate image: %s" % digest)
+
+    append_hash(img, digest)
+
+if __name__ == "__main__":
+    if sys.argv[1]:
+        try:
+            main(sys.argv[1])
+        except KeyboardInterrupt:
+            sys.exit(0)
+    else:
+        print("[*] Not enough arguments (!) ")
+        print("[*] Usage : parser.py bin")