Merge "Use getrandom for device input event ID generation" (cb47d4f8) · Commits · e / os / platform_frameworks_native

libs/input/Input.cpp

+24 −2

Original line number	Diff line number	Diff line
		@@ -35,6 +35,9 @@
		#ifdef __linux__
		#include <binder/Parcel.h>
		#endif
		#if defined(__ANDROID__)
		#include <sys/random.h>
		#endif

		using android::base::StringPrintf;

		@@ -110,8 +113,11 @@ const char* motionToolTypeToString(int32_t toolType) {
		}

		// --- IdGenerator ---

		static status_t getRandomBytes(uint8_t* data, size_t size) {
		#if defined(__ANDROID__)
		[[maybe_unused]]
		#endif
		static status_t
		getRandomBytes(uint8_t* data, size_t size) {
		int ret = TEMP_FAILURE_RETRY(open("/dev/urandom", O_RDONLY \| O_CLOEXEC \| O_NOFOLLOW));
		if (ret == -1) {
		return -errno;
		@@ -130,7 +136,22 @@ int32_t IdGenerator::nextId() const {
		constexpr uint32_t SEQUENCE_NUMBER_MASK = ~SOURCE_MASK;
		int32_t id = 0;

		#if defined(__ANDROID__)
		// On device, prefer 'getrandom' to '/dev/urandom' because it's faster.
		constexpr size_t BUF_LEN = sizeof(id);
		size_t totalBytes = 0;
		while (totalBytes < BUF_LEN) {
		ssize_t bytes = TEMP_FAILURE_RETRY(getrandom(&id, BUF_LEN, GRND_NONBLOCK));
		if (CC_UNLIKELY(bytes < 0)) {
		ALOGW("Failed to fill in random number for sequence number: %s.", strerror(errno));
		id = 0;
		break;
		}
		totalBytes += bytes;
		}
		#else
		#if defined(__linux__)
		// On host, <sys/random.h> / GRND_NONBLOCK is not available
		while (true) {
		status_t result = getRandomBytes(reinterpret_cast<uint8_t*>(&id), sizeof(id));
		if (result == OK) {
		@@ -138,6 +159,7 @@ int32_t IdGenerator::nextId() const {
		}
		}
		#endif // __linux__
		#endif // __ANDROID__
		return (id & SEQUENCE_NUMBER_MASK) \| static_cast<int32_t>(mSource);
		}