Documentation/usb/usbdevfs-drop-permissions.c

0001 #include <sys/ioctl.h>
0002 #include <sys/types.h>
0003 #include <sys/stat.h>
0004 #include <fcntl.h>
0005 #include <stdio.h>
0006 #include <errno.h>
0007 #include <string.h>
0008 #include <inttypes.h>
0009 #include <unistd.h>
0010
0011 #include <linux/usbdevice_fs.h>
0012
0013 /* For building without an updated set of headers */
0014 #ifndef USBDEVFS_DROP_PRIVILEGES
0015 #define USBDEVFS_DROP_PRIVILEGES        _IOW('U', 30, __u32)
0016 #define USBDEVFS_CAP_DROP_PRIVILEGES        0x40
0017 #endif
0018
0019 void drop_privileges(int fd, uint32_t mask)
0020 {
0021     int res;
0022
0023     res = ioctl(fd, USBDEVFS_DROP_PRIVILEGES, &mask);
0024     if (res)
0025         printf("ERROR: USBDEVFS_DROP_PRIVILEGES returned %d\n", res);
0026     else
0027         printf("OK: privileges dropped!\n");
0028 }
0029
0030 void reset_device(int fd)
0031 {
0032     int res;
0033
0034     res = ioctl(fd, USBDEVFS_RESET);
0035     if (!res)
0036         printf("OK: USBDEVFS_RESET succeeded\n");
0037     else
0038         printf("ERROR: reset failed! (%d - %s)\n",
0039                -res, strerror(-res));
0040 }
0041
0042 void claim_some_intf(int fd)
0043 {
0044     int i, res;
0045
0046     for (i = 0; i < 4; i++) {
0047         res = ioctl(fd, USBDEVFS_CLAIMINTERFACE, &i);
0048         if (!res)
0049             printf("OK: claimed if %d\n", i);
0050         else
0051             printf("ERROR claiming if %d (%d - %s)\n",
0052                    i, -res, strerror(-res));
0053     }
0054 }
0055
0056 int main(int argc, char *argv[])
0057 {
0058     uint32_t mask, caps;
0059     int c, fd;
0060
0061     fd = open(argv[1], O_RDWR);
0062     if (fd < 0) {
0063         printf("Failed to open file\n");
0064         goto err_fd;
0065     }
0066
0067     /*
0068      * check if dropping privileges is supported,
0069      * bail on systems where the capability is not present
0070      */
0071     ioctl(fd, USBDEVFS_GET_CAPABILITIES, &caps);
0072     if (!(caps & USBDEVFS_CAP_DROP_PRIVILEGES)) {
0073         printf("DROP_PRIVILEGES not supported\n");
0074         goto err;
0075     }
0076
0077     /*
0078      * Drop privileges but keep the ability to claim all
0079      * free interfaces (i.e., those not used by kernel drivers)
0080      */
0081     drop_privileges(fd, -1U);
0082
0083     printf("Available options:\n"
0084         "[0] Exit now\n"
0085         "[1] Reset device. Should fail if device is in use\n"
0086         "[2] Claim 4 interfaces. Should succeed where not in use\n"
0087         "[3] Narrow interface permission mask\n"
0088         "Which option shall I run?: ");
0089
0090     while (scanf("%d", &c) == 1) {
0091         switch (c) {
0092         case 0:
0093             goto exit;
0094         case 1:
0095             reset_device(fd);
0096             break;
0097         case 2:
0098             claim_some_intf(fd);
0099             break;
0100         case 3:
0101             printf("Insert new mask: ");
0102             scanf("%x", &mask);
0103             drop_privileges(fd, mask);
0104             break;
0105         default:
0106             printf("I don't recognize that\n");
0107         }
0108
0109         printf("Which test shall I run next?: ");
0110     }
0111
0112 exit:
0113     close(fd);
0114     return 0;
0115
0116 err:
0117     close(fd);
0118 err_fd:
0119     return 1;
0120 }