Merge cdm changes to android repo

Bug: 251924225
Test: GtsMediaTestCases
Change-Id: I1b4e64c0abf701fe1f5017f14dc72b72c3ea6770

libwvdrmengine/oemcrypto/util/src/oemcrypto_rsa_key.cpp

@@ -326,6 +326,27 @@ bool RsaPublicKey::IsMatchingPrivateKey(
   return RsaKeysAreMatchingPair(GetRsaKey(), private_key.GetRsaKey());
 }
 
+std::vector<uint8_t> RsaPrivateKey::GetPrivateExponent() const {
+  const BIGNUM* d = RSA_get0_d(key_);
+  if (d == nullptr) {
+    LOGE("Private exponent must not be null");
+    return {};
+  }
+  // Get the required length for the data.
+  const size_t length = BN_num_bytes(d);
+  if (length <= 0) {
+    LOGE("Private exponent length must be positive");
+    return {};
+  }
+  std::vector<uint8_t> serialized_private_exponent(length, 0);
+  if (static_cast<size_t>(BN_bn2bin(d, serialized_private_exponent.data())) !=
+      length) {
+    LOGE("Failed to convert the private exponent");
+    return {};
+  }
+  return serialized_private_exponent;
+}
+
 OEMCryptoResult RsaPublicKey::Serialize(uint8_t* buffer,
                                         size_t* buffer_size) const {
   if (buffer_size == nullptr) {