Merge "Verify UID of incoming Zygote connections." into main (5c96d2c1) · Commits · e / os / android_frameworks_base

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

+3 −0

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

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

core/jni/com_android_internal_os_ZygoteCommandBuffer.cpp

+53 −29

Original line number	Original line	Diff line number	Diff line
	@@ -354,6 +354,18 @@ jstring com_android_internal_os_ZygoteCommandBuffer_nativeNextArg(JNIEnv* env, j
	return result;		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		// 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		// 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.		// count. And we don't need access to the fd to do so.
	@@ -413,19 +425,12 @@ jboolean com_android_internal_os_ZygoteCommandBuffer_nativeForkRepeatedly(
	fail_fn_z("Failed to retrieve session socket timeout");		fail_fn_z("Failed to retrieve session socket timeout");
	}		}

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

	bool first_time = true;		bool first_time = true;
	do {		do {
	if (credentials.uid != static_cast<uid_t>(expected_uid)) {
	return JNI_FALSE;
	}
	n_buffer->readAllLines(first_time ? fail_fn_1 : fail_fn_n);		n_buffer->readAllLines(first_time ? fail_fn_1 : fail_fn_n);
	n_buffer->reset();		n_buffer->reset();
	int pid = zygote::forkApp(env, /* no pipe FDs */ -1, -1, session_socket_fds,		int pid = zygote::forkApp(env, /* no pipe FDs */ -1, -1, session_socket_fds,
	@@ -453,6 +458,7 @@ jboolean com_android_internal_os_ZygoteCommandBuffer_nativeForkRepeatedly(
	}		}
	}		}
	for (;;) {		for (;;) {
			bool valid_session_socket = true;
	// Clear buffer and get count from next command.		// Clear buffer and get count from next command.
	n_buffer->clear();		n_buffer->clear();
	// Poll isn't strictly necessary for now. But without it, disconnect is hard to detect.		// Poll isn't strictly necessary for now. But without it, disconnect is hard to detect.
	@@ -463,17 +469,42 @@ jboolean com_android_internal_os_ZygoteCommandBuffer_nativeForkRepeatedly(
	if ((fd_structs[SESSION_IDX].revents & POLLIN) != 0) {		if ((fd_structs[SESSION_IDX].revents & POLLIN) != 0) {
	if (n_buffer->getCount(fail_fn_z) != 0) {		if (n_buffer->getCount(fail_fn_z) != 0) {
	break;		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) {		} else if (poll_res == 0 \|\| (fd_structs[ZYGOTE_IDX].revents & POLLIN) == 0) {
	fail_fn_z(		fail_fn_z(
	CREATE_ERROR("Poll returned with no descriptors ready! Poll returned %d", poll_res));		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.		// We've now seen either a disconnect or connect request.
	close(session_socket);		new_fd = TEMP_FAILURE_RETRY(accept(zygote_socket_fd, nullptr, nullptr));
	int new_fd = TEMP_FAILURE_RETRY(accept(zygote_socket_fd, nullptr, nullptr));
	if (new_fd == -1) {		if (new_fd == -1) {
	fail_fn_z(CREATE_ERROR("Accept(%d) failed: %s", zygote_socket_fd, strerror(errno)));		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) {		if (new_fd != session_socket) {
	// Move new_fd back to the old value, so that we don't have to change Java-level data		// 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.		// structures to reflect a change. This implicitly closes the old one.
	@@ -493,13 +524,6 @@ jboolean com_android_internal_os_ZygoteCommandBuffer_nativeForkRepeatedly(
	fail_fn_z(CREATE_ERROR("Failed to set send timeout for socket %d: %s",		fail_fn_z(CREATE_ERROR("Failed to set send timeout for socket %d: %s",
	session_socket, strerror(errno)));		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;		first_time = false;
	} while (n_buffer->isSimpleForkCommand(minUid, fail_fn_n));		} while (n_buffer->isSimpleForkCommand(minUid, fail_fn_n));