it turns out some of those bits weren't random

segafs/makesegafs.py

@@ -1,11 +1,14 @@
+# pyright: reportMissingTypeStubs=false, reportOperatorIssue=false, reportUnknownArgumentType=false, reportUnknownMemberType=false
 from math import ceil
 import os
 import secrets
 import struct
+import time
 import zlib
 
-from Crypto.Cipher import AES
+from Crypto.Cipher import AES, PKCS1_OAEP
 from Crypto.Hash import HMAC, SHA1
+from Crypto.PublicKey import RSA
 from construct import Bytes, Const, Int16ul, Int32ul, Int64ul, Int8ul, Struct
 
 # ---- Configuration
@@ -65,6 +68,17 @@ BTIV = bytes.fromhex("")
 
 # The HMAC key that ensures the app/opt/pack created is authentic.
 SIGKEY = bytes.fromhex("")
+
+HEADER_META_PUBKEY = RSA.import_key("""-----BEGIN PUBLIC KEY-----
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAsRMLnJuczNpfoqPpHQ3o
+5XNkjKXO6P3ToV/45Az5dNaHVL7uEu9vPI7a2KYFQnNYgD3UUHFahfTcljzLOkcH
+1aVrhm8gaB/5mygjUJWcN+kKyB7sASqhL22RC7NlxtDY15ozli/b0MagVoaBAV5D
+MytUCa73GPRGY0x9v/wTvtmFclYCWjJ9c2QzrCrQ9eNTVyETwh5q6qKEARHGZgCX
+rWmdCsa/+oS+3pLbUGFlHCSZtCvvWCJgmgurlTGAGzoxrieO6XDEg2AGiRprWWL2
+BGNh7gwgnSq6FWnKSf2Qe7xoFcTpV5QhNFBQjrq0KnBDRfz5EXJnMoKxNYL6reqR
+uwIDAQAB
+-----END PUBLIC KEY-----
+""")
 # ----
 
 # ---- Constants. Don't edit.
@@ -123,8 +137,10 @@ print(f"Generated IV: {iv.hex()}")
 filesize = os.stat(INPUT_FILE).st_size
 BOOTID["block_count"] = ceil(filesize / BOOTID["block_size"]) + 8
 
-bullshit = secrets.token_bytes(BOOTID["block_size"])
-bullshit_crc32 = zlib.crc32(bullshit)
+header_meta = struct.pack("<Q", time.time()) + os.path.abspath(INPUT_FILE).encode("utf-8")
+header_meta += secrets.token_bytes(BOOTID["block_size"] - len(header_meta))
+header_meta = PKCS1_OAEP.new(HEADER_META_PUBKEY).encrypt(header_meta)
+bullshit_crc32 = zlib.crc32(header_meta)
 block_crc32s = [0, bullshit_crc32, bullshit_crc32, bullshit_crc32, bullshit_crc32, bullshit_crc32, bullshit_crc32, bullshit_crc32]
 
 with open(INPUT_FILE, "rb") as fin, open(OUTPUT_FILE, "w+b") as fout:
@@ -140,9 +156,8 @@ with open(INPUT_FILE, "rb") as fin, open(OUTPUT_FILE, "w+b") as fout:
     # We'll generate random bytes for them though.
     _ = fout.write(secrets.token_bytes(BOOTID["block_size"] - 0x2800))
 
-    # Bullshit out 7 random blocks for the header.
     for i in range(BOOTID["header_block_count"] - 1):
-        _ = fout.write(bullshit)
+        _ = fout.write(header_meta)
 
     # Encrypt the contents of the file.
     total_written = 0