Merge "Verify UID of incoming Zygote connections." into sc-dev (eca6d61e) · Commits · e / os / android_frameworks_base

core/java/com/android/internal/os/ZygoteConnection.java

+3 −0

Original line number	Diff line number	Diff line
		@@ -93,6 +93,9 @@ class ZygoteConnection {
		throw ex;
		}

		if (peer.getUid() != Process.SYSTEM_UID) {
		throw new ZygoteSecurityException("Only system UID is allowed to connect to Zygote.");
		}
		isEof = false;
		}

core/jni/com_android_internal_os_ZygoteCommandBuffer.cpp

+53 −28

Original line number	Diff line number	Diff line
		@@ -341,6 +341,18 @@ jstring com_android_internal_os_ZygoteCommandBuffer_nativeNextArg(JNIEnv* env, j
		return result;
		}

		static uid_t getSocketPeerUid(int socket, const std::function<void(const std::string&)>& fail_fn) {
		struct ucred credentials;
		socklen_t cred_size = sizeof credentials;
		if (getsockopt(socket, SOL_SOCKET, SO_PEERCRED, &credentials, &cred_size) == -1
		\|\| cred_size != sizeof credentials) {
		fail_fn(CREATE_ERROR("Failed to get socket credentials, %s",
		strerror(errno)));
		}

		return credentials.uid;
		}

		// Read all lines from the current command into the buffer, and then reset the buffer, so
		// we will start reading again at the beginning of the command, starting with the argument
		// count. And we don't need access to the fd to do so.
		@@ -398,18 +410,12 @@ jboolean com_android_internal_os_ZygoteCommandBuffer_nativeForkRepeatedly(
		fail_fn_z("Failed to retrieve session socket timeout");
		}

		struct ucred credentials;
		socklen_t cred_size = sizeof credentials;
		if (getsockopt(n_buffer->getFd(), SOL_SOCKET, SO_PEERCRED, &credentials, &cred_size) == -1
		\|\| cred_size != sizeof credentials) {
		fail_fn_1(CREATE_ERROR("ForkMany failed to get initial credentials, %s", strerror(errno)));
		uid_t peerUid = getSocketPeerUid(session_socket, fail_fn_1);
		if (peerUid != static_cast<uid_t>(expected_uid)) {
		return JNI_FALSE;
		}

		bool first_time = true;
		do {
		if (credentials.uid != expected_uid) {
		return JNI_FALSE;
		}
		n_buffer->readAllLines(first_time ? fail_fn_1 : fail_fn_n);
		n_buffer->reset();
		int pid = zygote::forkApp(env, /* no pipe FDs */ -1, -1, session_socket_fds,
		@@ -439,22 +445,48 @@ jboolean com_android_internal_os_ZygoteCommandBuffer_nativeForkRepeatedly(
		// Clear buffer and get count from next command.
		n_buffer->clear();
		for (;;) {
		bool valid_session_socket = true;
		// Poll isn't strictly necessary for now. But without it, disconnect is hard to detect.
		int poll_res = TEMP_FAILURE_RETRY(poll(fd_structs, 2, -1 /* infinite timeout */));
		if ((fd_structs[SESSION_IDX].revents & POLLIN) != 0) {
		if (n_buffer->getCount(fail_fn_z) != 0) {
		break;
		} // else disconnected;
		} else {
		// Session socket was disconnected
		valid_session_socket = false;
		close(session_socket);
		}
		} else if (poll_res == 0 \|\| (fd_structs[ZYGOTE_IDX].revents & POLLIN) == 0) {
		fail_fn_z(
		CREATE_ERROR("Poll returned with no descriptors ready! Poll returned %d", poll_res));
		}
		int new_fd = -1;
		do {
		// We've now seen either a disconnect or connect request.
		close(session_socket);
		int new_fd = TEMP_FAILURE_RETRY(accept(zygote_socket_fd, nullptr, nullptr));
		new_fd = TEMP_FAILURE_RETRY(accept(zygote_socket_fd, nullptr, nullptr));
		if (new_fd == -1) {
		fail_fn_z(CREATE_ERROR("Accept(%d) failed: %s", zygote_socket_fd, strerror(errno)));
		}
		uid_t newPeerUid = getSocketPeerUid(new_fd, fail_fn_1);
		if (newPeerUid != static_cast<uid_t>(expected_uid)) {
		ALOGW("Dropping new connection with a mismatched uid %d\n", newPeerUid);
		close(new_fd);
		new_fd = -1;
		} else {
		// If we still have a valid session socket, close it now
		if (valid_session_socket) {
		close(session_socket);
		}
		valid_session_socket = true;
		}
		} while (!valid_session_socket);

		// At this point we either have a valid new connection (new_fd > 0), or
		// an existing session socket we can poll on
		if (new_fd == -1) {
		// The new connection wasn't valid, and we still have an old one; retry polling
		continue;
		}
		if (new_fd != session_socket) {
		// Move new_fd back to the old value, so that we don't have to change Java-level data
		// structures to reflect a change. This implicitly closes the old one.
		@@ -474,13 +506,6 @@ jboolean com_android_internal_os_ZygoteCommandBuffer_nativeForkRepeatedly(
		fail_fn_z(CREATE_ERROR("Failed to set send timeout for socket %d: %s",
		session_socket, strerror(errno)));
		}
		if (getsockopt(session_socket, SOL_SOCKET, SO_PEERCRED, &credentials, &cred_size) == -1) {
		fail_fn_z(CREATE_ERROR("ForkMany failed to get credentials: %s", strerror(errno)));
		}
		if (cred_size != sizeof credentials) {
		fail_fn_z(CREATE_ERROR("ForkMany credential size = %d, should be %d",
		cred_size, static_cast<int>(sizeof credentials)));
		}
		}
		first_time = false;
		} while (n_buffer->isSimpleForkCommand(minUid, fail_fn_n));