| 1 | #include <sys/ioctl.h>
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| 2 | #include <sys/types.h>
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| 3 | #include <sys/stat.h>
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| 4 | #include <fcntl.h>
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| 5 | #include <stdio.h>
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| 6 | #include <errno.h>
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| 7 | #include <string.h>
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| 8 | #include <inttypes.h>
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| 9 | #include <unistd.h>
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| 10 |
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| 11 | #include <linux/usbdevice_fs.h>
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| 12 |
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| 13 |
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| 14 | #ifndef USBDEVFS_DROP_PRIVILEGES
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| 15 | #define USBDEVFS_DROP_PRIVILEGES _IOW('U', 30, __u32)
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| 16 | #define USBDEVFS_CAP_DROP_PRIVILEGES 0x40
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| 17 | #endif
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| 18 |
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| 19 | void drop_privileges(int fd, uint32_t mask)
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| 20 | {
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| 21 | int res;
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| 22 |
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| 23 | res = ioctl(fd, USBDEVFS_DROP_PRIVILEGES, &mask);
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| 24 | if (res)
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| 25 | printf("ERROR: USBDEVFS_DROP_PRIVILEGES returned %d\n", res);
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| 26 | else
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| 27 | printf("OK: privileges dropped!\n");
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| 28 | }
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| 29 |
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| 30 | void reset_device(int fd)
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| 31 | {
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| 32 | int res;
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| 33 |
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| 34 | res = ioctl(fd, USBDEVFS_RESET);
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| 35 | if (!res)
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| 36 | printf("OK: USBDEVFS_RESET succeeded\n");
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| 37 | else
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| 38 | printf("ERROR: reset failed! (%d - %s)\n",
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| 39 | -res, strerror(-res));
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| 40 | }
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| 41 |
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| 42 | void claim_some_intf(int fd)
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| 43 | {
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| 44 | int i, res;
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| 45 |
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| 46 | for (i = 0; i < 4; i++) {
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| 47 | res = ioctl(fd, USBDEVFS_CLAIMINTERFACE, &i);
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| 48 | if (!res)
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| 49 | printf("OK: claimed if %d\n", i);
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| 50 | else
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| 51 | printf("ERROR claiming if %d (%d - %s)\n",
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| 52 | i, -res, strerror(-res));
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| 53 | }
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| 54 | }
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| 55 |
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| 56 | int main(int argc, char *argv[])
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| 57 | {
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| 58 | uint32_t mask, caps;
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| 59 | int c, fd;
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| 60 |
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| 61 | fd = open(argv[1], O_RDWR);
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| 62 | if (fd < 0) {
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| 63 | printf("Failed to open file\n");
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| 64 | goto err_fd;
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| 65 | }
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| 66 |
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| 67 | |
| 68 | * check if dropping privileges is supported,
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| 69 | * bail on systems where the capability is not present
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| 70 |
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| 71 | ioctl(fd, USBDEVFS_GET_CAPABILITIES, &caps);
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| 72 | if (!(caps & USBDEVFS_CAP_DROP_PRIVILEGES)) {
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| 73 | printf("DROP_PRIVILEGES not supported\n");
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| 74 | goto err;
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| 75 | }
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| 76 |
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| 77 | |
| 78 | * Drop privileges but keep the ability to claim all
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| 79 | * free interfaces (i.e., those not used by kernel drivers)
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| 80 |
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| 81 | drop_privileges(fd, -1U);
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| 82 |
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| 83 | printf("Available options:\n"
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| 84 | "[0] Exit now\n"
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| 85 | "[1] Reset device. Should fail if device is in use\n"
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| 86 | "[2] Claim 4 interfaces. Should succeed where not in use\n"
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| 87 | "[3] Narrow interface permission mask\n"
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| 88 | "Which option shall I run?: ");
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| 89 |
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| 90 | while (scanf("%d", &c) == 1) {
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| 91 | switch (c) {
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| 92 | case 0:
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| 93 | goto exit;
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| 94 | case 1:
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| 95 | reset_device(fd);
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| 96 | break;
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| 97 | case 2:
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| 98 | claim_some_intf(fd);
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| 99 | break;
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| 100 | case 3:
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| 101 | printf("Insert new mask: ");
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| 102 | scanf("%x", &mask);
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| 103 | drop_privileges(fd, mask);
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| 104 | break;
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| 105 | default:
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| 106 | printf("I don't recognize that\n");
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| 107 | }
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| 108 |
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| 109 | printf("Which test shall I run next?: ");
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| 110 | }
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| 111 |
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| 112 | exit:
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| 113 | close(fd);
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| 114 | return 0;
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| 115 |
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| 116 | err:
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| 117 | close(fd);
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| 118 | err_fd:
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| 119 | return 1;
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| 120 | }
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