match_digest.c   [plain text]

/*
 * SPDX-License-Identifier: ISC
 *
 * Copyright (c) 1996, 1998-2005, 2007-2019
 *	Todd C. Miller <Todd.Miller@sudo.ws>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * Sponsored in part by the Defense Advanced Research Projects
 * Agency (DARPA) and Air Force Research Laboratory, Air Force
 * Materiel Command, USAF, under agreement number F39502-99-1-0512.
 */

/*
 * This is an open source non-commercial project. Dear PVS-Studio, please check it.
 * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
 */

#include <config.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <stdlib.h>
#ifdef HAVE_STRING_H
# include <string.h>
#endif /* HAVE_STRING_H */
#ifdef HAVE_STRINGS_H
# include <strings.h>
#endif /* HAVE_STRINGS_H */
#include <unistd.h>

#include "sudoers.h"
#include <gram.h>

bool
digest_matches(int fd, const char *file, const struct command_digest *digest)
{
    unsigned char *file_digest = NULL;
    unsigned char *sudoers_digest = NULL;
    bool matched = false;
    size_t digest_len;
    debug_decl(digest_matches, SUDOERS_DEBUG_MATCH)

    if (fd == -1)
	goto done;

    file_digest = sudo_filedigest(fd, file, digest->digest_type, &digest_len);
    if (lseek(fd, (off_t)0, SEEK_SET) == -1) {
	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO|SUDO_DEBUG_LINENO,
	    "unable to rewind digest fd");
    }
    if (file_digest == NULL) {
	/* Warning (if any) printed by sudo_filedigest() */
	goto done;
    }

    /* Convert the command digest from ascii to binary. */
    if ((sudoers_digest = malloc(digest_len)) == NULL) {
	sudo_warnx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
	goto done;
    }
    if (strlen(digest->digest_str) == digest_len * 2) {
	/* Convert ascii hex to binary. */
	unsigned int i;
	for (i = 0; i < digest_len; i++) {
	    const int h = hexchar(&digest->digest_str[i + i]);
	    if (h == -1)
		goto bad_format;
	    sudoers_digest[i] = (unsigned char)h;
	}
    } else {
	/* Convert base64 to binary. */
	size_t len = base64_decode(digest->digest_str, sudoers_digest, digest_len);
	if (len != digest_len) {
	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
		"incorrect length for digest, expected %zu, got %zu",
		digest_len, len);
	    goto bad_format;
	}
    }

    if (memcmp(file_digest, sudoers_digest, digest_len) == 0) {
	matched = true;
    } else {
	sudo_debug_printf(SUDO_DEBUG_DIAG|SUDO_DEBUG_LINENO,
	    "%s digest mismatch for %s, expecting %s",
	    digest_type_to_name(digest->digest_type), file, digest->digest_str);
    }
    goto done;

bad_format:
    sudo_warnx(U_("digest for %s (%s) is not in %s form"), file,
	digest->digest_str, digest_type_to_name(digest->digest_type));
done:
    free(sudoers_digest);
    free(file_digest);
    debug_return_bool(matched);
}