d883f52e1f
The new USBDEVFS_DROP_PRIVILEGES ioctl allows a process to voluntarily
relinquish the ability to issue other ioctls that may interfere with
other processes and drivers that have claimed an interface on the
device.
This commit also includes a simple utility to be able to test the
ioctl, located at Documentation/usb/usbdevfs-drop-permissions.c
Example (with qemu-kvm's input device):
$ lsusb
...
Bus 001 Device 002: ID 0627:0001 Adomax Technology Co., Ltd
$ usb-devices
...
C: #Ifs= 1 Cfg#= 1 Atr=a0 MxPwr=100mA
I: If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=00 Prot=02 Driver=usbhid
$ sudo ./usbdevfs-drop-permissions /dev/bus/usb/001/002
OK: privileges dropped!
Available options:
[0] Exit now
[1] Reset device. Should fail if device is in use
[2] Claim 4 interfaces. Should succeed where not in use
[3] Narrow interface permission mask
Which option shall I run?: 1
ERROR: USBDEVFS_RESET failed! (1 - Operation not permitted)
Which test shall I run next?: 2
ERROR claiming if 0 (1 - Operation not permitted)
ERROR claiming if 1 (1 - Operation not permitted)
ERROR claiming if 2 (1 - Operation not permitted)
ERROR claiming if 3 (1 - Operation not permitted)
Which test shall I run next?: 0
After unbinding usbhid:
$ usb-devices
...
I: If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=00 Prot=02 Driver=(none)
$ sudo ./usbdevfs-drop-permissions /dev/bus/usb/001/002
...
Which option shall I run?: 2
OK: claimed if 0
ERROR claiming if 1 (1 - Operation not permitted)
ERROR claiming if 2 (1 - Operation not permitted)
ERROR claiming if 3 (1 - Operation not permitted)
Which test shall I run next?: 1
OK: USBDEVFS_RESET succeeded
Which test shall I run next?: 0
After unbinding usbhid and restricting the mask:
$ sudo ./usbdevfs-drop-permissions /dev/bus/usb/001/002
...
Which option shall I run?: 3
Insert new mask: 0
OK: privileges dropped!
Which test shall I run next?: 2
ERROR claiming if 0 (1 - Operation not permitted)
ERROR claiming if 1 (1 - Operation not permitted)
ERROR claiming if 2 (1 - Operation not permitted)
ERROR claiming if 3 (1 - Operation not permitted)
Signed-off-by: Reilly Grant <reillyg@chromium.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Emilio López <emilio.lopez@collabora.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
121 lines
2.3 KiB
C
121 lines
2.3 KiB
C
#include <sys/ioctl.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <errno.h>
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#include <string.h>
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#include <inttypes.h>
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#include <unistd.h>
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#include <linux/usbdevice_fs.h>
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/* For building without an updated set of headers */
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#ifndef USBDEVFS_DROP_PRIVILEGES
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#define USBDEVFS_DROP_PRIVILEGES _IOW('U', 30, __u32)
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#define USBDEVFS_CAP_DROP_PRIVILEGES 0x40
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#endif
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void drop_privileges(int fd, uint32_t mask)
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{
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int res;
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res = ioctl(fd, USBDEVFS_DROP_PRIVILEGES, &mask);
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if (res)
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printf("ERROR: USBDEVFS_DROP_PRIVILEGES returned %d\n", res);
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else
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printf("OK: privileges dropped!\n");
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}
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void reset_device(int fd)
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{
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int res;
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res = ioctl(fd, USBDEVFS_RESET);
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if (!res)
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printf("OK: USBDEVFS_RESET succeeded\n");
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else
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printf("ERROR: reset failed! (%d - %s)\n",
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-res, strerror(-res));
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}
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void claim_some_intf(int fd)
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{
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int i, res;
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for (i = 0; i < 4; i++) {
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res = ioctl(fd, USBDEVFS_CLAIMINTERFACE, &i);
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if (!res)
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printf("OK: claimed if %d\n", i);
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else
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printf("ERROR claiming if %d (%d - %s)\n",
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i, -res, strerror(-res));
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}
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}
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int main(int argc, char *argv[])
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{
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uint32_t mask, caps;
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int c, fd;
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fd = open(argv[1], O_RDWR);
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if (fd < 0) {
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printf("Failed to open file\n");
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goto err_fd;
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}
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/*
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* check if dropping privileges is supported,
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* bail on systems where the capability is not present
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*/
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ioctl(fd, USBDEVFS_GET_CAPABILITIES, &caps);
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if (!(caps & USBDEVFS_CAP_DROP_PRIVILEGES)) {
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printf("DROP_PRIVILEGES not supported\n");
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goto err;
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}
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/*
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* Drop privileges but keep the ability to claim all
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* free interfaces (i.e., those not used by kernel drivers)
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*/
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drop_privileges(fd, -1U);
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printf("Available options:\n"
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"[0] Exit now\n"
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"[1] Reset device. Should fail if device is in use\n"
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"[2] Claim 4 interfaces. Should succeed where not in use\n"
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"[3] Narrow interface permission mask\n"
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"Which option shall I run?: ");
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while (scanf("%d", &c) == 1) {
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switch (c) {
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case 0:
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goto exit;
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case 1:
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reset_device(fd);
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break;
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case 2:
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claim_some_intf(fd);
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break;
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case 3:
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printf("Insert new mask: ");
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scanf("%x", &mask);
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drop_privileges(fd, mask);
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break;
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default:
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printf("I don't recognize that\n");
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}
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printf("Which test shall I run next?: ");
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}
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exit:
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close(fd);
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return 0;
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err:
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close(fd);
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err_fd:
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return 1;
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}
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