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am 03752be0: am 0c297f5e: Merge "Revert "Fold uevent message origin checking from init into libcutils.""

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* commit '03752be0a437d12e19ac73ebe23385fe6f756e2c':
  Revert "Fold uevent message origin checking from init into libcutils."
This commit is contained in:
Nick Kralevich 2011-04-27 10:35:06 -07:00 committed by Android Git Automerger
commit de35f2741c
4 changed files with 29 additions and 108 deletions
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32
include/cutils/uevent.h
View file

@ -1,32 +0,0 @@
/*
* 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.
*/
#ifndef __CUTILS_UEVENT_H
#define __CUTILS_UEVENT_H
#include <sys/socket.h>
#ifdef __cplusplus
extern "C" {
#endif
ssize_t uevent_checked_recv(int socket, void *buffer, size_t length);
#ifdef __cplusplus
}
#endif
#endif /* __CUTILS_UEVENT_H */

34
init/devices.c
View file

@ -34,8 +34,6 @@
#include <asm/page.h>
#include <sys/wait.h>
#include <cutils/uevent.h>
#include "devices.h"
#include "util.h"
#include "log.h"
@ -646,9 +644,35 @@ static void handle_firmware_event(struct uevent *uevent)
#define UEVENT_MSG_LEN 1024
void handle_device_fd()
{
char msg[UEVENT_MSG_LEN+2];
int n;
while ((n = uevent_checked_recv(device_fd, msg, UEVENT_MSG_LEN)) > 0) {
for(;;) {
char msg[UEVENT_MSG_LEN+2];
char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
struct iovec iov = {msg, sizeof(msg)};
struct sockaddr_nl snl;
struct msghdr hdr = {&snl, sizeof(snl), &iov, 1, cred_msg, sizeof(cred_msg), 0};
ssize_t n = recvmsg(device_fd, &hdr, 0);
if (n <= 0) {
break;
}
if ((snl.nl_groups != 1) || (snl.nl_pid != 0)) {
/* ignoring non-kernel netlink multicast message */
continue;
}
struct cmsghdr * cmsg = CMSG_FIRSTHDR(&hdr);
if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
/* no sender credentials received, ignore message */
continue;
}
struct ucred * cred = (struct ucred *)CMSG_DATA(cmsg);
if (cred->uid != 0) {
/* message from non-root user, ignore */
continue;
}
if(n >= UEVENT_MSG_LEN) /* overflow -- discard */
continue;

1
libcutils/Android.mk
View file

@ -74,7 +74,6 @@ else
mspace.c \
selector.c \
tztime.c \
uevent.c \
zygote.c
commonHostSources += \

70
libcutils/uevent.c
View file

@ -1,70 +0,0 @@
/*
* 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 <strings.h>
#include <linux/netlink.h>
/**
* Like recv(), but checks that messages actually originate from the kernel.
*/
ssize_t uevent_checked_recv(int socket, void *buffer, size_t length) {
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,
};
ssize_t n = recvmsg(socket, &hdr, 0);
if (n <= 0) {
return n;
}
if (addr.nl_groups == 0 || addr.nl_pid != 0) {
/* ignoring non-kernel or unicast netlink message */
goto out;
}
struct cmsghdr *cmsg = CMSG_FIRSTHDR(&hdr);
if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
/* ignoring netlink message with no sender credentials */
goto out;
}
struct ucred *cred = (struct ucred *)CMSG_DATA(cmsg);
if (cred->uid != 0) {
/* ignoring netlink message from non-root user */
goto out;
}
return n;
out:
/* clear residual potentially malicious data */
bzero(buffer, length);
errno = EIO;
return -1;
}