summaryrefslogtreecommitdiffstats
path: root/misc/keyslot_checker/chk_luks_keyslots.c
diff options
context:
space:
mode:
Diffstat (limited to 'misc/keyslot_checker/chk_luks_keyslots.c')
-rw-r--r--misc/keyslot_checker/chk_luks_keyslots.c371
1 files changed, 371 insertions, 0 deletions
diff --git a/misc/keyslot_checker/chk_luks_keyslots.c b/misc/keyslot_checker/chk_luks_keyslots.c
new file mode 100644
index 0000000..308b002
--- /dev/null
+++ b/misc/keyslot_checker/chk_luks_keyslots.c
@@ -0,0 +1,371 @@
+/*
+ * LUKS keyslot entropy tester. Works only for header version 1.
+ *
+ * Functionality: Determines sample entropy (symbols: bytes) for
+ * each (by default) 512B sector in each used keyslot. If it
+ * is lower than a threshold, the sector address is printed
+ * as it is suspected of having non-"random" data in it, indicating
+ * damage by overwriting. This can obviously not find overwriting
+ * with random or random-like data (encrypted, compressed).
+ *
+ * Version history:
+ * v0.1: 09.09.2012 Initial release
+ * v0.2: 08.10.2012 Converted to use libcryptsetup
+ *
+ * Copyright (C) 2012, Arno Wagner <arno@wagner.name>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <ctype.h>
+#include <math.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <libcryptsetup.h>
+
+const char *help =
+"Version 0.2 [8.10.2012]\n"
+"\n"
+" chk_luks_keyslots [options] luks-device \n"
+"\n"
+"This tool checks all keyslots of a LUKS device for \n"
+"low entropy sections. If any are found, they are reported. \n"
+"This allows one to find areas damaged by things like filesystem \n"
+"creation or RAID superblocks. \n"
+"\n"
+"Options: \n"
+" -t <num> Entropy threshold. Possible values 0.0 ... 1.0 \n"
+" Default: 0.90, which works well for 512B sectors.\n"
+" For 512B sectors, you will get frequent misdetections\n"
+" at thresholds around 0.94\n"
+" Higher value: more sensitive but more false detections.\n"
+" -s <num> Sector size. Must divide keyslot-size.\n"
+" Default: 512 Bytes.\n"
+" Values smaller than 128 are generally not very useful.\n"
+" For values smaller than the default, you need to adjust\n"
+" the threshold down to reduce misdetection. For values\n"
+" larger than the default you need to adjust the threshold\n"
+" up to retain sensitivity.\n"
+" -v Print found suspicious sectors verbosely. \n"
+" -d Print decimal addresses instead of hex ones.\n"
+"\n";
+
+
+/* Config defaults */
+
+static int sector_size = 512;
+static double threshold = 0.90;
+static int print_decimal = 0;
+static int verbose = 0;
+
+/* tools */
+
+/* Calculates and returns sample entropy on byte level for
+ * The argument.
+ */
+static double ent_samp(unsigned char * buf, int len)
+{
+ int freq[256]; /* stores symbol frequencies */
+ int i;
+ double e, f;
+
+ /* 0. Plausibility checks */
+ if (len <= 0)
+ return 0.0;
+
+ /* 1. count all frequencies */
+ for (i = 0; i < 256; i++) {
+ freq[i] = 0.0;
+ }
+
+ for (i = 0; i < len; i ++)
+ freq[buf[i]]++;
+
+ /* 2. calculate sample entropy */
+ e = 0.0;
+ for (i = 0; i < 256; i++) {
+ f = freq[i];
+ if (f > 0) {
+ f = f / (double)len;
+ e += f * log2(f);
+ }
+ }
+
+ if (e != 0.0)
+ e = -1.0 * e;
+
+ e = e / 8.0;
+ return e;
+}
+
+static void print_address(FILE *out, uint64_t value)
+{
+ if (print_decimal) {
+ fprintf(out,"%08" PRIu64 " ", value);
+ } else {
+ fprintf(out,"%#08" PRIx64 " ", value);
+ }
+}
+
+/* uses default "hd" style, i.e. 16 bytes followed by ASCII */
+static void hexdump_line(FILE *out, uint64_t address, unsigned char *buf) {
+ int i;
+ static char tbl[16] = "0123456789ABCDEF";
+
+ fprintf(out," ");
+ print_address(out, address);
+ fprintf(out," ");
+
+ /* hex */
+ for (i = 0; i < 16; i++) {
+ fprintf(out, "%c%c",
+ tbl[(unsigned char)buf[i]>> 4],
+ tbl[(unsigned char)buf[i] & 0x0f]);
+ fprintf(out," ");
+ if (i == 7)
+ fprintf(out," ");
+ }
+
+ fprintf(out," ");
+
+ /* ascii */
+ for (i = 0; i < 16; i++) {
+ if (isprint(buf[i])) {
+ fprintf(out, "%c", buf[i]);
+ } else {
+ fprintf(out, ".");
+ }
+ }
+ fprintf(out, "\n");
+}
+
+static void hexdump_sector(FILE *out, unsigned char *buf, uint64_t address, int len)
+{
+ int done;
+
+ done = 0;
+ while (len - done >= 16) {
+ hexdump_line(out, address + done, buf + done);
+ done += 16;
+ }
+}
+
+static int check_keyslots(FILE *out, struct crypt_device *cd, int f_luks)
+{
+ int i;
+ double ent;
+ off_t ofs;
+ uint64_t start, length, end;
+ crypt_keyslot_info ki;
+ unsigned char buffer[sector_size];
+
+ for (i = 0; i < crypt_keyslot_max(CRYPT_LUKS1) ; i++) {
+ fprintf(out, "- processing keyslot %d:", i);
+ ki = crypt_keyslot_status(cd, i);
+ if (ki == CRYPT_SLOT_INACTIVE) {
+ fprintf(out, " keyslot not in use\n");
+ continue;
+ }
+
+ if (ki == CRYPT_SLOT_INVALID) {
+ fprintf(out, "\nError: keyslot invalid.\n");
+ return EXIT_FAILURE;
+ }
+
+ if (crypt_keyslot_area(cd, i, &start, &length) < 0) {
+ fprintf(stderr,"\nError: querying keyslot area failed for slot %d\n", i);
+ perror(NULL);
+ return EXIT_FAILURE;
+ }
+ end = start + length;
+
+ fprintf(out, " start: ");
+ print_address(out, start);
+ fprintf(out, " end: ");
+ print_address(out, end);
+ fprintf(out, "\n");
+
+ /* check whether sector-size divides size */
+ if (length % sector_size != 0) {
+ fprintf(stderr,"\nError: Argument to -s does not divide keyslot size\n");
+ return EXIT_FAILURE;
+ }
+
+ for (ofs = start; (uint64_t)ofs < end; ofs += sector_size) {
+ if (lseek(f_luks, ofs, SEEK_SET) != ofs) {
+ fprintf(stderr,"\nCannot seek to keyslot area.\n");
+ return EXIT_FAILURE;
+ }
+ if (read(f_luks, buffer, sector_size) != sector_size) {
+ fprintf(stderr,"\nCannot read keyslot area.\n");
+ return EXIT_FAILURE;
+ }
+ ent = ent_samp(buffer, sector_size);
+ if (ent < threshold) {
+ fprintf(out, " low entropy at: ");
+ print_address(out, ofs);
+ fprintf(out, " entropy: %f\n", ent);
+ if (verbose) {
+ fprintf(out, " Binary dump:\n");
+ hexdump_sector(out, buffer, (uint64_t)ofs, sector_size);
+ fprintf(out,"\n");
+ }
+ }
+ }
+ }
+
+ return EXIT_SUCCESS;
+}
+
+/* Main */
+int main(int argc, char **argv)
+{
+ /* for option processing */
+ int c, r;
+ char *device;
+
+ /* for use of libcryptsetup */
+ struct crypt_device *cd;
+
+ /* Other vars */
+ int f_luks; /* device file for the luks device */
+ FILE *out;
+
+ /* temporary helper vars */
+ int res;
+
+ /* getopt values */
+ char *s, *end;
+ double tvalue;
+ int svalue;
+
+ /* global initializations */
+ out = stdout;
+
+ /* get commandline parameters */
+ while ((c = getopt (argc, argv, "t:s:vd")) != -1) {
+ switch (c) {
+ case 't':
+ s = optarg;
+ tvalue = strtod(s, &end);
+ if (s == end) {
+ fprintf(stderr, "\nError: Parsing of argument to -t failed.\n");
+ exit(EXIT_FAILURE);
+ }
+
+ if (tvalue < 0.0 || tvalue > 1.0) {
+ fprintf(stderr,"\nError: Argument to -t must be in 0.0 ... 1.0\n");
+ exit(EXIT_FAILURE);
+ }
+ threshold = tvalue;
+ break;
+ case 's':
+ s = optarg;
+ svalue = strtol(s, &end, 10);
+ if (s == end) {
+ fprintf(stderr, "\nError: Parsing of argument to -s failed.\n");
+ exit(EXIT_FAILURE);
+ }
+
+ if (svalue < 1) {
+ fprintf(stderr,"\nError: Argument to -s must be >= 1 \n");
+ exit(EXIT_FAILURE);
+ }
+ sector_size = svalue;
+ break;
+ case 'v':
+ verbose = 1;
+ break;
+ case 'd':
+ print_decimal = 1;
+ break;
+ case '?':
+ if (optopt == 't' || optopt == 's')
+ fprintf (stderr,"\nError: Option -%c requires an argument.\n",
+ optopt);
+ else if (isprint (optopt)) {
+ fprintf(stderr,"\nError: Unknown option `-%c'.\n", optopt);
+ fprintf(stderr,"\n\n%s", help);
+ } else {
+ fprintf (stderr, "\nError: Unknown option character `\\x%x'.\n",
+ optopt);
+ fprintf(stderr,"\n\n%s", help);
+ }
+ exit(EXIT_SUCCESS);
+ default:
+ exit(EXIT_FAILURE);
+ }
+ }
+
+ /* parse non-option stuff. Should be exactly one, the device. */
+ if (optind+1 != argc) {
+ fprintf(stderr,"\nError: exactly one non-option argument expected!\n");
+ fprintf(stderr,"\n\n%s", help);
+ exit(EXIT_FAILURE);
+ }
+ device = argv[optind];
+
+ /* test whether we can open and read device */
+ /* This is needed as we are reading the actual data
+ * in the keyslots directly from the LUKS container.
+ */
+ f_luks = open(device, O_RDONLY);
+ if (f_luks == -1) {
+ fprintf(stderr,"\nError: Opening of device %s failed:\n", device);
+ perror(NULL);
+ exit(EXIT_FAILURE);
+ }
+
+ /* now get the parameters we need via libcryptsetup */
+ /* Basically we need all active keyslots and their placement on disk */
+
+ /* first init. This does the following:
+ * - gets us a crypt_device struct with some values filled in
+ * Note: This does some init stuff we do not need, but that
+ * should not cause trouble.
+ */
+
+ res = crypt_init(&cd, device);
+ if (res < 0) {
+ fprintf(stderr, "crypt_init() failed. Maybe not running as root?\n");
+ close(f_luks);
+ exit(EXIT_FAILURE);
+ }
+
+ /* now load LUKS header into the crypt_device
+ * This should also make sure a valid LUKS1 header is on disk
+ * and hence we should be able to skip magic and version checks.
+ */
+ res = crypt_load(cd, CRYPT_LUKS1, NULL);
+ if (res < 0) {
+ fprintf(stderr, "crypt_load() failed. LUKS header too broken/absent?\n");
+ crypt_free(cd);
+ close(f_luks);
+ exit(EXIT_FAILURE);
+ }
+
+ fprintf(out, "\nparameters (commandline and LUKS header):\n");
+ fprintf(out, " sector size: %d\n", sector_size);
+ fprintf(out, " threshold: %0f\n\n", threshold);
+
+ r = check_keyslots(out, cd, f_luks);
+
+ crypt_free(cd);
+ close(f_luks);
+ return r;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-07 02:58:08 +0000