samba-mirror/lib/fuzzing/fuzz_sddl_parse.c

/*
  Fuzz sddl decoding and encoding
  Copyright (C) Catalyst IT 2023

  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 3 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, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"
#include "libcli/security/security.h"
#include "librpc/gen_ndr/conditional_ace.h"
#include "fuzzing/fuzzing.h"
#include "util/charset/charset.h"

#define MAX_LENGTH (100 * 1024 - 1)
static char sddl_string[MAX_LENGTH + 1] = {0};
static struct dom_sid dom_sid = {0};

int LLVMFuzzerInitialize(int *argc, char ***argv)
{
	string_to_sid(&dom_sid,
		      "S-1-5-21-2470180966-3899876309-2637894779");
	return 0;
}


int LLVMFuzzerTestOneInput(const uint8_t *input, size_t len)
{
	TALLOC_CTX *mem_ctx = NULL;
	struct security_descriptor *sd1 = NULL;
	struct security_descriptor *sd2 = NULL;
	char *result = NULL;
	bool ok;

	if (len > MAX_LENGTH) {
		return 0;
	}

	memcpy(sddl_string, input, len);
	sddl_string[len] = '\0';

	mem_ctx = talloc_new(NULL);

	sd1 = sddl_decode(mem_ctx, sddl_string, &dom_sid);
	if (sd1 == NULL) {
		goto end;
	}
	result = sddl_encode(mem_ctx, sd1, &dom_sid);
	if (result == NULL) {
		/*
		 * Because Samba currently doesn't enforce strict
		 * utf-8 parsing, illegal utf-8 sequences in
		 * sddl_string could have ferried bad characters
		 * through into the security descriptor conditions
		 * that we then find we can't encode.
		 *
		 * The proper solution is strict UTF-8 enforcement in
		 * sddl_decode, but for now we forgive unencodable
		 * security descriptors made from bad utf-8.
		 */
		size_t byte_len, char_len, utf16_len;
		ok = utf8_check(sddl_string, len,
				&byte_len, &char_len, &utf16_len);
		if (!ok) {
			goto end;
		}
		/* utf-8 was fine, but we couldn't encode! */
		abort();
	}

	sd2 = sddl_decode(mem_ctx, result, &dom_sid);
	if (sd2 == NULL) {
		if (strlen(result) > CONDITIONAL_ACE_MAX_LENGTH) {
			/*
			 * This could fail if a unicode string or
			 * attribute name that contains escapable
			 * bytes (e.g '\x0b') in an unescaped form in
			 * the original string ends up with them in
			 * the escaped form ("%000b") in the result
			 * string, making the entire attribute name
			 * too long for the arbitrary limit we set for
			 * SDDL attribute names.
			 *
			 * We could increase that arbitrary limit (to,
			 * say, CONDITIONAL_ACE_MAX_LENGTH * 5), but
			 * that is getting very far from real world
			 * needs.
			 */
			goto end;
		}
		abort();
	}
	ok = security_descriptor_equal(sd1, sd2);
	if (!ok) {
		abort();
	}
end:
	talloc_free(mem_ctx);
	return 0;
}