84c99136fd
This is a partial revert of https://android-review.googlesource.com/c/platform/system/core/+/528619. The uid-check was done before https://patchwork.kernel.org/patch/1525551/ was available, and thus is now unnecessary to perform such check, since we can just rely on the kernel patch now. Bug: 71632076 Test: aosp_sailfish-userdebug still works Change-Id: I1d1319b774483d1714ecb4dd838a20e055acc2a3
124 lines
3.4 KiB
C++
124 lines
3.4 KiB
C++
/*
|
|
* Copyright (C) 2011 The Android Open Source Project
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*/
|
|
|
|
#include <cutils/uevent.h>
|
|
|
|
#include <errno.h>
|
|
#include <stdint.h>
|
|
#include <stdio.h>
|
|
#include <string.h>
|
|
#include <strings.h>
|
|
#include <sys/socket.h>
|
|
#include <sys/un.h>
|
|
#include <unistd.h>
|
|
|
|
#include <linux/netlink.h>
|
|
|
|
extern "C" {
|
|
|
|
/**
|
|
* Like recv(), but checks that messages actually originate from the kernel.
|
|
*/
|
|
ssize_t uevent_kernel_multicast_recv(int socket, void* buffer, size_t length) {
|
|
uid_t uid = -1;
|
|
return uevent_kernel_multicast_uid_recv(socket, buffer, length, &uid);
|
|
}
|
|
|
|
/**
|
|
* Like the above, but passes a uid_t in by pointer. In the event that this
|
|
* fails due to a bad uid check, the uid_t will be set to the uid of the
|
|
* socket's peer.
|
|
*
|
|
* If this method rejects a netlink message from outside the kernel, it
|
|
* returns -1, sets errno to EIO, and sets "user" to the UID associated with the
|
|
* message. If the peer UID cannot be determined, "user" is set to -1."
|
|
*/
|
|
ssize_t uevent_kernel_multicast_uid_recv(int socket, void* buffer, size_t length, uid_t* uid) {
|
|
return uevent_kernel_recv(socket, buffer, length, true, uid);
|
|
}
|
|
|
|
ssize_t uevent_kernel_recv(int socket, void* buffer, size_t length, bool require_group, uid_t* uid) {
|
|
struct iovec iov = {buffer, length};
|
|
struct sockaddr_nl addr;
|
|
char control[CMSG_SPACE(sizeof(struct ucred))];
|
|
struct msghdr hdr = {
|
|
&addr, sizeof(addr), &iov, 1, control, sizeof(control), 0,
|
|
};
|
|
struct ucred* cred;
|
|
|
|
*uid = -1;
|
|
ssize_t n = recvmsg(socket, &hdr, 0);
|
|
if (n <= 0) {
|
|
return n;
|
|
}
|
|
|
|
struct cmsghdr* cmsg = CMSG_FIRSTHDR(&hdr);
|
|
if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
|
|
/* ignoring netlink message with no sender credentials */
|
|
goto out;
|
|
}
|
|
|
|
cred = (struct ucred*)CMSG_DATA(cmsg);
|
|
*uid = cred->uid;
|
|
|
|
if (addr.nl_pid != 0) {
|
|
/* ignore non-kernel */
|
|
goto out;
|
|
}
|
|
if (require_group && addr.nl_groups == 0) {
|
|
/* ignore unicast messages when requested */
|
|
goto out;
|
|
}
|
|
|
|
return n;
|
|
|
|
out:
|
|
/* clear residual potentially malicious data */
|
|
bzero(buffer, length);
|
|
errno = EIO;
|
|
return -1;
|
|
}
|
|
|
|
int uevent_open_socket(int buf_sz, bool passcred) {
|
|
struct sockaddr_nl addr;
|
|
int on = passcred;
|
|
int s;
|
|
|
|
memset(&addr, 0, sizeof(addr));
|
|
addr.nl_family = AF_NETLINK;
|
|
addr.nl_pid = getpid();
|
|
addr.nl_groups = 0xffffffff;
|
|
|
|
s = socket(PF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_KOBJECT_UEVENT);
|
|
if (s < 0) return -1;
|
|
|
|
/* buf_sz should be less than net.core.rmem_max for this to succeed */
|
|
if (setsockopt(s, SOL_SOCKET, SO_RCVBUF, &buf_sz, sizeof(buf_sz)) < 0) {
|
|
close(s);
|
|
return -1;
|
|
}
|
|
|
|
setsockopt(s, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on));
|
|
|
|
if (bind(s, (struct sockaddr*)&addr, sizeof(addr)) < 0) {
|
|
close(s);
|
|
return -1;
|
|
}
|
|
|
|
return s;
|
|
}
|
|
|
|
} // extern "C"
|