scripts: imgtool: fix compression with encryption

adds TLV which stores compressed image size in case encryption is on.
This is to avoid wrong streaam size due to encryption padding.

Signed-off-by: Mateusz Michalek <mateusz.michalek@nordicsemi.no>

Author: michalek-no

scripts/imgtool/image.py

@@ -94,6 +94,7 @@
         'DECOMP_SIZE': 0x70,
         'DECOMP_SHA': 0x71,
         'DECOMP_SIGNATURE': 0x72,
+        'COMP_DEC_SIZE' : 0x73,
 }
 
 TLV_SIZE = 4
@@ -460,7 +461,7 @@ def create(self, key, public_key_format, enckey, dependencies=None,
                sw_type=None, custom_tlvs=None, compression_tlvs=None,
                compression_type=None, encrypt_keylen=128, clear=False,
                fixed_sig=None, pub_key=None, vector_to_sign=None,
-               user_sha='auto', is_pure=False):
+               user_sha='auto', is_pure=False, keep_comp_size=False, dont_encrypt=False):
         self.enckey = enckey
 
         # key decides on sha, then pub_key; of both are none default is used
@@ -522,6 +523,9 @@ def create(self, key, public_key_format, enckey, dependencies=None,
             dependencies_num = len(dependencies[DEP_IMAGES_KEY])
             protected_tlv_size += (dependencies_num * 16)
 
+        if keep_comp_size:
+            compression_tlvs["COMP_DEC_SIZE"] = struct.pack(
+                self.get_struct_endian() + 'L', self.image_size)
         if compression_tlvs is not None:
             for value in compression_tlvs.values():
                 protected_tlv_size += TLV_SIZE + len(value)
@@ -537,7 +541,7 @@ def create(self, key, public_key_format, enckey, dependencies=None,
         #
         # This adds the padding if image is not aligned to the 16 Bytes
         # in encrypted mode
-        if self.enckey is not None:
+        if self.enckey is not None and dont_encrypt is False:
             pad_len = len(self.payload) % 16
             if pad_len > 0:
                 pad = bytes(16 - pad_len)
@@ -594,6 +598,7 @@ def create(self, key, public_key_format, enckey, dependencies=None,
                     prot_tlv.add(tag, value)
 
             protected_tlv_off = len(self.payload)
+
             self.payload += prot_tlv.get()
 
         tlv = TLV(self.endian)
@@ -657,7 +662,7 @@ def create(self, key, public_key_format, enckey, dependencies=None,
         if protected_tlv_off is not None:
             self.payload = self.payload[:protected_tlv_off]
 
-        if enckey is not None:
+        if enckey is not None and dont_encrypt is False:
             if encrypt_keylen == 256:
                 plainkey = os.urandom(32)
             else:

scripts/imgtool/main.py

@@ -521,12 +521,11 @@ def sign(key, public_key_format, align, version, pad_sig, header_size,
             'Pure signatures, currently, enforces preferred hash algorithm, '
             'and forbids sha selection by user.')
 
-    img.create(key, public_key_format, enckey, dependencies, boot_record,
+    if compression in ["lzma2", "lzma2armthumb"]:
+        img.create(key, public_key_format, enckey, dependencies, boot_record,
                custom_tlvs, compression_tlvs, None, int(encrypt_keylen), clear,
                baked_signature, pub_key, vector_to_sign, user_sha=user_sha,
-               is_pure=is_pure)
-
-    if compression in ["lzma2", "lzma2armthumb"]:
+               is_pure=is_pure, keep_comp_size=False, dont_encrypt=True)
         compressed_img = image.Image(version=decode_version(version),
                   header_size=header_size, pad_header=pad_header,
                   pad=pad, confirm=confirm, align=int(align),
@@ -562,12 +561,20 @@ def sign(key, public_key_format, align, version, pad_sig, header_size,
                 lc = comp_default_lc, lp = comp_default_lp)
             compressed_img.load_compressed(compressed_data, compression_header)
             compressed_img.base_addr = img.base_addr
+            keep_comp_size = False;
+            if enckey:
+                keep_comp_size = True
             compressed_img.create(key, public_key_format, enckey,
                dependencies, boot_record, custom_tlvs, compression_tlvs,
                compression, int(encrypt_keylen), clear, baked_signature,
                pub_key, vector_to_sign, user_sha=user_sha,
-               is_pure=is_pure)
+               is_pure=is_pure, keep_comp_size=keep_comp_size)
             img = compressed_img
+    else:
+        img.create(key, public_key_format, enckey, dependencies, boot_record,
+               custom_tlvs, compression_tlvs, None, int(encrypt_keylen), clear,
+               baked_signature, pub_key, vector_to_sign, user_sha=user_sha,
+               is_pure=is_pure)
     img.save(outfile, hex_addr)
     if sig_out is not None:
         new_signature = img.get_signature()