Fix for security vulnerability in media server DO NOT MERGE

bug: 23540426
Change-Id: I5d602f99fd82e50d0136d47ce20cfa1ac9fd7ae2
(cherry picked from commit 9adc728)

Author: jefftinker

media/libmedia/ICrypto.cpp

@@ -255,7 +255,28 @@ status_t BnCrypto::onTransact(
             }
 
             AString errorDetailMsg;
-            ssize_t result = decrypt(
+            ssize_t result;
+
+            size_t sumSubsampleSizes = 0;
+            bool overflow = false;
+            for (int32_t i = 0; i < numSubSamples; ++i) {
+                CryptoPlugin::SubSample &ss = subSamples[i];
+                if (sumSubsampleSizes <= SIZE_MAX - ss.mNumBytesOfEncryptedData) {
+                    sumSubsampleSizes += ss.mNumBytesOfEncryptedData;
+                } else {
+                    overflow = true;
+                }
+                if (sumSubsampleSizes <= SIZE_MAX - ss.mNumBytesOfClearData) {
+                    sumSubsampleSizes += ss.mNumBytesOfClearData;
+                } else {
+                    overflow = true;
+                }
+            }
+
+            if (overflow || sumSubsampleSizes != totalSize) {
+                result = -EINVAL;
+            } else {
+                result = decrypt(
                     secure,
                     key,
                     iv,
@@ -264,6 +285,7 @@ status_t BnCrypto::onTransact(
                     subSamples, numSubSamples,
                     secure ? secureBufferId : dstPtr,
                     &errorDetailMsg);
+            }
 
             reply->writeInt32(result);