Differences

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--- devicesal [2009/05/07 09:38] – document "ocmmod" marcus
+++ devicesal [2009/05/27 12:31] – example for ssatrans marcus
@@ Line 1: / Line 1: @@
+Missing Info:
+<code>
+Dict 0xfc - contains an unknown 8 byte key, used in dev_0xd8, dev_0xd9.
+</code>
 Native modules:
 <code>
@@ Line 94: / Line 102: @@
 // Some decrypt function.
+// KEYBLOB seems to be 16 byte in practice.
 any_t
-dev_0xd8 (blob_t data1, blob_t data2)
+dev_0xd8 (blob_t ciphertext, blob_t keyblob)
 {
-  blob_t data3 = data2 XOR concat (dict[0xfc], dict[0xfc]);
+  blob_t key = keyblob XOR concat (dict[0xfc], dict[0xfc]);
-  dict[0xdb] = data3;
+  // Side-effect.
+  dict[0xdb] = key;
-  blob_t shasum = SHA1 (data3[0..1f]);
+  blob_t hashed_key = SHA1 (key[0..14]);
-  blob_t iv = shasum[0..7];
+  blob_t des_iv = hashed_key[0..7];
-  blob_t key = shasum[8..15]
+  blob_t des_key = hashed_key[8..15]
-  blob_t dec_data1 = DES_CBC_Decrypt (data1, iv, key, 0xd8_DESDecrypt);
+  blob_t data = DES_CBC_Decrypt (ciphertext, des_iv, des_key, 0xd8_DESDecrypt);
   // Decrypt with ocmmod cipher.
-  int len = blob_length (dec_data);
+  int len = blob_length (data);
   // Round up to multiple of 8.
   len = (len + 7) / 8 * 8;
-  blob_t out = repeat_nul (len);
+  blob_t plaintext = repeat_nul (len);
-  out = native::ocmmod (dec_data1, out, shasum, len, 1);
+  plaintext = native::ocmmod (data, plaintext, hashed_key, len, 1);
-  return decode_asn1 (out);
+  // Return deserialized object.
+  return decode_asn1 (plaintext);
+}
+// Some encrypt function.
+// KEYBLOB seems to be 16 byte in practice.
+blob_t
+dev_0xd9 (any_t plainobj, blob_t keyblob)
+{
+  blob_t key = keyblob XOR concat (dict[0xfc], dict[0xfc]);
+  // Side-effect.
+  dict[0xdb] = key;
+  // Serialization.
+  plaintext = encode_asn1 (plaintext);
+  // Encrypt with ocmmod cipher.
+  int len = blob_length (data);
+  // Round up to multiple of 8.
+  len = (len + 7) / 8 * 8;
+  blob_t data = repeat_nul (len);
+  blob_t hashed_key = SHA1 (key[0..14]);
+  data = native::ocmmod (plaintext, data, hashed_key, len, 0);
+  // Encrypt DES.
+  blob_t des_iv = hashed_key[0..7];
+  blob_t des_key = hashed_key[8..15]
+  blob_t ciphertext = DES_CBC_Decrypt (data, des_iv, des_key, 0xd7_DESEncrypt);
+  return ciphertext;
 }
 </code>
+NOT part of device.sal, but for lack of a better place, here an example of SsaTrans on updater.ocm:
+<code>
+$ SsaTrans updater.ocm
+BCSeedRand63 (1, "j5\162\GS\140<,\f");
+BCSetCryptTable ("L\225\164\152\DC1\RSD?\216f\198!\196\154\154\201\195b \192l^V\176r\245\151*\245[[\DC1\NULV#"...);
+v_39 = BCNewBlob (8);
+v_41 = BCDES_SetKey ("\188k\180(\150\EOT,\138");
+arg_0 = Unknown
+v_43 = BCDES_CBC BCDDecrypt (arg_0, v_39, v_41, "\216");
+v_44 = BCBlobLength (v_43);
+v_46 = BCBlobLength ("<!--omg certificated-->");
+v_49 = BCSubBlob (v_43, v_44 - v_46, -1);
+v_51 = BCCompareBlob (v_49, "<!--omg certificated-->");
+if (v_51 == 0) [1 -> 1]
+  {
+    return [v_43, 1];
+  }
+else [1 -> 1]
+  {
+    return [0];
+  }
+v_56 = BCIfElse (v_43);
+v_57 = BCSerialize (v_56);
+return v_57;
+</code>