Combined Decrypt Calls

(This is a merge of http://go/wvgerrit/93829,
http://go/wvgerrit/93830, http://go/wvgerrit/93832,
http://go/wvgerrit/93833, and http://go/wvgerrit/93834 from the
Widevine repo.)

This implements the CDM code changes necessary to take advantage of
Combined Decrypt Calls on OEMCrypto v16. The result of this is that
WVCryptoPlugin is much lighter now because it can pass the full sample
down to the core in one call, but CryptoSession is heavier, as it now
has to handle more complex fallback logic when devices can't handle
multiple subsamples at once.

This patch also removes support for the 'cens' and 'cbc1' schema, which
are being dropped in OEMCrypto v16. This fixes an overflow in the code
for handling those schemas by removing it entirely.

This patch also fixes the "in chunks" legacy decrypt path to use larger
chunk sizes on devices with higher resource rating tiers.

Bug: 135285640
Bug: 123435824
Bug: 138584971
Bug: 139257871
Bug: 78289910
Bug: 149361893
Test: no new CE CDM Unit Test failures
Test: Google Play plays
Test: Netflix plays
Test: no new GTS failures
Change-Id: Ic4952c9fa3bc7fd5ed08698e88254380a7a18514

libwvdrmengine/cdm/util/include/advance_iv_ctr.h

@@ -0,0 +1,46 @@
+// Copyright 2019 Google LLC. All Rights Reserved. This file and proprietary
+// source code may only be used and distributed under the Widevine Master
+// License Agreement.
+
+#ifndef WVCDM_UTIL_ADVANCE_IV_CTR_H_
+#define WVCDM_UTIL_ADVANCE_IV_CTR_H_
+
+#include <stdint.h>
+#include <string.h>
+
+#include "string_conversions.h"
+
+namespace wvcdm {
+
+// Advance an IV according to ISO-CENC's CTR modes. The lower half of the IV is
+// split off and treated as an unsigned 64-bit integer, then incremented by the
+// number of complete crypto blocks decrypted. The resulting value is then
+// copied back into the IV over the previous lower half.
+inline void AdvanceIvCtr(uint8_t (*subsample_iv)[16], size_t bytes) {
+  constexpr size_t kAesBlockSize = 16;
+  constexpr size_t kIvSize = kAesBlockSize;
+  constexpr size_t kCounterIndex = kIvSize / 2;
+  constexpr size_t kCounterSize = kIvSize / 2;
+
+  uint64_t counter;
+
+  static_assert(
+      sizeof(*subsample_iv) == kIvSize,
+      "The subsample_iv field is no longer the length of an AES-128 IV.");
+  static_assert(sizeof(counter) == kCounterSize,
+                "A uint64_t failed to be half the size of an AES-128 IV.");
+
+  // Defensive copy because the elements of the array may not be properly
+  // aligned
+  memcpy(&counter, &(*subsample_iv)[kCounterIndex], kCounterSize);
+
+  const size_t increment =
+      bytes / kAesBlockSize;  // The truncation here is intentional
+  counter = htonll64(ntohll64(counter) + increment);
+
+  memcpy(&(*subsample_iv)[kCounterIndex], &counter, kCounterSize);
+}
+
+}  // namespace wvcdm
+
+#endif  // WVCDM_UTIL_ADVANCE_IV_CTR_H_