/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*      Copyright (c) 1988 AT&T */
/*        All Rights Reserved   */

#include <sys/types.h>
#include <locale.h>
#include <string.h>

#define FBSZ 64

/*
 * function that uses heuristics to determine if
 * a file is encrypted
 */

int
isencrypt(const char *fbuf, size_t ninbuf)
{
        const char      *fp;
        char            *locale;
        int             crflag = 0;
        int             i;

        if (ninbuf == 0)
                return (0);
        fp = fbuf;
        while (fp < &fbuf[ninbuf])
        /* Check if file has non-ASCII characters */
                if (*fp++ & 0200) {
                        crflag = 1;
                        break;
                }
        if (crflag == 0)
                /* If all characters are ASCII, assume file is cleartext */
                return (0);
        locale = setlocale(LC_CTYPE, 0);
        if (strcmp(locale, "C") == 0 || strcmp(locale, "ascii") == 0)
        /*
         * If character type is ascii or "C",
         * assume file is encrypted
         */
                return (1);
        if (ninbuf >= 64) {
                /*
                 * We are in non-ASCII environment; use
                 * chi-square test to determine if file
                 * is encrypted if there are more
                 * than 64 characters in buffer.
                 */

                int bucket[8];
                float cs;

                for (i = 0; i < 8; i++) bucket[i] = 0;

                for (i = 0; i < 64; i++) bucket[(fbuf[i]>>5)&07] += 1;

                cs = 0;
                for (i = 0; i < 8; i++) cs += (bucket[i]-8)*(bucket[i]-8);
                cs /= 8.;

                if (cs <= 24.322)
                        return (1);
                return (0);
        }

        /*
         * If file has nulls, assume it is encrypted
         */

        for (i = 0; i < ninbuf; i++)
                if (fbuf[i] == '\0')
                        return (1);

        /*
         * If last character in buffer is not a new-line,
         * assume file is encrypted
         */

        if (fbuf[ninbuf - 1] != '\n')
                return (1);
        return (0);
}