Add example of dictionary search.

misc/dict_search/Makefile

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+TARGET=luks_dict
+CFLAGS=-O2 -g -Wall -D_GNU_SOURCE
+LDLIBS=-lcryptsetup
+CC=gcc
+
+SOURCES=$(wildcard *.c)
+OBJECTS=$(SOURCES:.c=.o)
+
+all: $(TARGET)
+
+$(TARGET): $(OBJECTS)
+	$(CC) -o $@ $^ $(LDLIBS)
+
+clean:
+	rm -f *.o *~ core $(TARGET)
+
+.PHONY: clean

misc/dict_search/README

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+Simple example how to use libcryptsetup
+for password search.
+
+Run: luks_dict <device|image> <dictionary> [cpus]
+
+<device|image> is LUKS device or image
+<dictionary> is list of passphrases to try
+(note trailing EOL is stripped)
+
+cpus - number of processes to start in parallel
+
+Format of dictionary file is simple one password per line,
+if first char on line s # it is skiped as comment.
+
+You have it run as root (device-mapper cannot
+create dmcrypt devices as nrmal user. Code need
+to map keyslots as temporary dmcrypt device.)

misc/dict_search/luks_dict.c

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+/*
+ * Example of LUKS password dictionary search
+ *
+ * Run this as root, e.g. ./luks_check test.img /usr/share/john/password.lst 4
+ *
+ * Copyright (C) 2012 Milan Broz <asi@ucw.cz>
+ *
+ * This copyrighted material is made available to anyone wishing to use,
+ * modify, copy, or redistribute it subject to the terms and conditions
+ * of the GNU General Public License v.2.
+ *
+ * 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 <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <sys/prctl.h>
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <libcryptsetup.h>
+
+#define MAX_LEN 512
+
+static void check(struct crypt_device *cd, const char *pwd_file, unsigned my_id, unsigned max_id)
+{
+	FILE *f;
+	int len, r;
+	unsigned long line = 0;
+	char pwd[MAX_LEN];
+
+	if (fork())
+		return;
+
+	/* open password file, now in separate process */
+	f = fopen(pwd_file, "r");
+	if (!f) {
+		printf("Cannot open %s.\n", pwd_file);
+		exit(EXIT_FAILURE);
+	}
+
+	while (fgets(pwd, MAX_LEN, f)) {
+
+		/* every process tries N-th line, skip others */
+		if (line++ % max_id != my_id)
+			continue;
+
+		len = strlen(pwd);
+
+		/* lines starting "#" are comments */
+		if (pwd[0] == '#')
+			continue;
+
+		/* strip EOL - this is like a input from tty */
+		if (len && pwd[len - 1] == '\n') {
+			pwd[len - 1] = '\0';
+			len--;
+		}
+
+		//printf("%d: checking %s\n", my_id, pwd);
+		r = crypt_activate_by_passphrase(cd, NULL, CRYPT_ANY_SLOT, pwd, len, 0);
+		if (r >= 0) {
+			printf("Found passphrase for slot %d: %s\n", r, pwd);
+			break;
+		}
+	}
+
+	fclose(f);
+	crypt_free(cd);
+	exit(0);
+}
+
+int main(int argc, char *argv[])
+{
+	int i, status, procs = 4;
+	struct crypt_device *cd;
+
+	if (argc < 3 || argc > 4) {
+		printf("Use: %s <LUKS_device|file> <password file> [#processes] %d\n", argv[0], argc);
+		exit(EXIT_FAILURE);
+	}
+
+	if (argc == 4 && sscanf(argv[3], "%i", &procs) != 1) {
+		printf("Wrong number of processes.\n");
+		exit(EXIT_FAILURE);
+	}
+
+	/* signal all children if anything happens */
+	prctl(PR_SET_PDEATHSIG, SIGHUP);
+	setpriority(PRIO_PROCESS, 0, -5);
+
+	/* we are not going to modify anything, so common init is ok */
+	if (crypt_init(&cd, argv[1]) || crypt_load(cd, CRYPT_LUKS1, NULL)) {
+		printf("Cannot open %s.\n", argv[1]);
+		exit(EXIT_FAILURE);
+	}
+
+	/* run scan in separate processes */
+	for (i = 0; i < procs; i++)
+		check(cd, argv[2], i, procs);
+
+	/* wait until at least one finishes */
+	wait(&status);
+	kill(0, SIGHUP);
+	return 0;
+}