uevent.c revision 2d55e02d0f3c27f0c99ab889ab7b73126280a21c
13f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang/* 23f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang * Copyright (C) 2011 The Android Open Source Project 33f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang * 43f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang * Licensed under the Apache License, Version 2.0 (the "License"); 53f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang * you may not use this file except in compliance with the License. 63f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang * You may obtain a copy of the License at 73f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang * 83f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang * http://www.apache.org/licenses/LICENSE-2.0 93f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang * 103f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang * Unless required by applicable law or agreed to in writing, software 113f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang * distributed under the License is distributed on an "AS IS" BASIS, 123f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 133f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang * See the License for the specific language governing permissions and 143f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang * limitations under the License. 153f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang */ 163f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang 173f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang#include <cutils/uevent.h> 183f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang 193f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang#include <errno.h> 202d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin#include <stdbool.h> 212d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin#include <string.h> 223f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang#include <strings.h> 232d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin#include <sys/socket.h> 242d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin#include <sys/un.h> 252d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin#include <unistd.h> 263f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang 273f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang#include <linux/netlink.h> 283f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang 293f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang/** 303f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang * Like recv(), but checks that messages actually originate from the kernel. 313f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang */ 3257de8b8f27f887ca8084671df777a4ac199ba647Nick Kralevichssize_t uevent_kernel_multicast_recv(int socket, void *buffer, size_t length) { 333f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang struct iovec iov = { buffer, length }; 343f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang struct sockaddr_nl addr; 353f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang char control[CMSG_SPACE(sizeof(struct ucred))]; 363f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang struct msghdr hdr = { 373f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang &addr, 383f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang sizeof(addr), 393f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang &iov, 403f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang 1, 413f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang control, 423f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang sizeof(control), 433f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang 0, 443f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang }; 453f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang 463f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang ssize_t n = recvmsg(socket, &hdr, 0); 473f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang if (n <= 0) { 483f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang return n; 493f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang } 503f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang 513f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang if (addr.nl_groups == 0 || addr.nl_pid != 0) { 523f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang /* ignoring non-kernel or unicast netlink message */ 533f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang goto out; 543f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang } 553f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang 563f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang struct cmsghdr *cmsg = CMSG_FIRSTHDR(&hdr); 573f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) { 583f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang /* ignoring netlink message with no sender credentials */ 593f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang goto out; 603f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang } 613f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang 623f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang struct ucred *cred = (struct ucred *)CMSG_DATA(cmsg); 633f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang if (cred->uid != 0) { 643f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang /* ignoring netlink message from non-root user */ 653f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang goto out; 663f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang } 673f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang 683f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang return n; 693f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang 703f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tangout: 713f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang /* clear residual potentially malicious data */ 723f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang bzero(buffer, length); 733f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang errno = EIO; 743f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang return -1; 753f582e92f07d358f3d0941b86407b39e2e7e67ccVernon Tang} 762d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin 772d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavinint uevent_open_socket(int buf_sz, bool passcred) 782d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin{ 792d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin struct sockaddr_nl addr; 802d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin int on = passcred; 812d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin int s; 822d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin 832d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin memset(&addr, 0, sizeof(addr)); 842d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin addr.nl_family = AF_NETLINK; 852d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin addr.nl_pid = getpid(); 862d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin addr.nl_groups = 0xffffffff; 872d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin 882d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin s = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT); 892d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin if(s < 0) 902d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin return -1; 912d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin 922d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin setsockopt(s, SOL_SOCKET, SO_RCVBUFFORCE, &buf_sz, sizeof(buf_sz)); 932d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin setsockopt(s, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on)); 942d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin 952d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin if(bind(s, (struct sockaddr *) &addr, sizeof(addr)) < 0) { 962d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin close(s); 972d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin return -1; 982d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin } 992d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin 1002d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin return s; 1012d55e02d0f3c27f0c99ab889ab7b73126280a21cDima Zavin} 102