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Fix WVCryptoPlugin use after free vulnerability.

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The shared memory buffer used by srcPtr can be freed by another
thread because it is not protected by a mutex. Subsequently,
a use after free AIGABRT can occur in a race condition.

SafetyNet logging is not added to avoid log spamming. The
mutex lock is called to setup for decryption, which is
called frequently.

The crash was reproduced on the device before the fix.
Verified the test passes after the fix.

Test: sts
  sts-tradefed run sts-engbuild-no-spl-lock -m StsHostTestCases --test android.security.sts.Bug_176495665#testPocBug_176495665

Test: push to device with target_hwasan-userdebug build
  adb shell /data/local/tmp/Bug-176495665_sts64

Bug: 176495665
Bug: 176444161
Change-Id: If62b73a9c636048f942a2fc63a13b5bfd1e57b86
This commit is contained in:
Edwin Wong
2021-03-08 21:37:42 -08:00
parent bb2e41adfd
commit 596d8bf4cc
3 changed files with 15 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
libwvdrmengine/mediacrypto/Android.bp
View File

@@ -90,6 +90,8 @@ cc_library_static {
"liblog", "liblog",
], ],
cflags: ["-Wthread-safety"],
proprietary: true, proprietary: true,
} }

9
libwvdrmengine/mediacrypto/include_hidl/WVCryptoPlugin.h
View File

@@ -7,8 +7,11 @@
#ifndef WV_CRYPTO_PLUGIN_H_ #ifndef WV_CRYPTO_PLUGIN_H_
#define WV_CRYPTO_PLUGIN_H_ #define WV_CRYPTO_PLUGIN_H_
#include <android-base/thread_annotations.h>
#include <android/hidl/memory/1.0/IMemory.h> #include <android/hidl/memory/1.0/IMemory.h>
#include <mutex>
#include "HidlTypes.h" #include "HidlTypes.h"
#include "log.h" #include "log.h"
#include "wv_content_decryption_module.h" #include "wv_content_decryption_module.h"
@@ -60,7 +63,7 @@ struct WVCryptoPlugin : public ::drm::V1_4::ICryptoPlugin {
const SharedBuffer& source, const SharedBuffer& source,
uint64_t offset, uint64_t offset,
const DestinationBuffer& destination, const DestinationBuffer& destination,
decrypt_1_2_cb _hidl_cb) override; decrypt_1_2_cb _hidl_cb) override NO_THREAD_SAFETY_ANALYSIS; // use unique_lock
Return<void> getLogMessages( Return<void> getLogMessages(
getLogMessages_cb _hidl_cb) override; getLogMessages_cb _hidl_cb) override;
@@ -73,7 +76,7 @@ struct WVCryptoPlugin : public ::drm::V1_4::ICryptoPlugin {
wvcdm::LoggingUidSetter mLoggingUidSetter; wvcdm::LoggingUidSetter mLoggingUidSetter;
wvcdm::CdmSessionId mSessionId; wvcdm::CdmSessionId mSessionId;
std::map<uint32_t, sp<IMemory> > mSharedBufferMap; std::map<uint32_t, sp<IMemory> > mSharedBufferMap GUARDED_BY(mSharedBufferLock);
sp<wvcdm::WvContentDecryptionModule> const mCDM; sp<wvcdm::WvContentDecryptionModule> const mCDM;
uint32_t mUserId; uint32_t mUserId;
@@ -81,6 +84,8 @@ struct WVCryptoPlugin : public ::drm::V1_4::ICryptoPlugin {
Status_V1_2 attemptDecrypt( Status_V1_2 attemptDecrypt(
const wvcdm::CdmDecryptionParametersV16& params, const wvcdm::CdmDecryptionParametersV16& params,
bool haveEncryptedSubsamples, std::string* errorDetailMsg); bool haveEncryptedSubsamples, std::string* errorDetailMsg);
std::mutex mSharedBufferLock;
}; };
} // namespace widevine } // namespace widevine

7
libwvdrmengine/mediacrypto/src_hidl/WVCryptoPlugin.cpp
View File

@@ -121,6 +121,8 @@ Return<void> WVCryptoPlugin::setSharedBufferBase(
const hidl_memory& base, uint32_t bufferId) { const hidl_memory& base, uint32_t bufferId) {
sp<IMemory> hidlMemory = mapMemory(base); sp<IMemory> hidlMemory = mapMemory(base);
std::lock_guard<std::mutex> shared_buffer_lock(mSharedBufferLock);
// allow mapMemory to return nullptr // allow mapMemory to return nullptr
mSharedBufferMap[bufferId] = hidlMemory; mSharedBufferMap[bufferId] = hidlMemory;
return Void(); return Void();
@@ -169,7 +171,7 @@ Return<void> WVCryptoPlugin::decrypt_1_2(
uint64_t offset, uint64_t offset,
const DestinationBuffer& destination, const DestinationBuffer& destination,
decrypt_1_2_cb _hidl_cb) { decrypt_1_2_cb _hidl_cb) {
std::unique_lock<std::mutex> lock(mSharedBufferLock);
if (mSharedBufferMap.find(source.bufferId) == mSharedBufferMap.end()) { if (mSharedBufferMap.find(source.bufferId) == mSharedBufferMap.end()) {
_hidl_cb(Status_V1_2::ERROR_DRM_CANNOT_HANDLE, 0, _hidl_cb(Status_V1_2::ERROR_DRM_CANNOT_HANDLE, 0,
"source decrypt buffer base not set"); "source decrypt buffer base not set");
@@ -242,6 +244,9 @@ Return<void> WVCryptoPlugin::decrypt_1_2(
destPtr = static_cast<void *>(handle); destPtr = static_cast<void *>(handle);
} }
// release mSharedBufferLock
lock.unlock();
// Set up the decrypt params // Set up the decrypt params
CdmDecryptionParametersV16 params; CdmDecryptionParametersV16 params;
params.key_id = cryptoKey; params.key_id = cryptoKey;