/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1998 Dag-Erling Smørgrav
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer
 *    in this position and unchanged.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#include <err.h>
#include <errno.h>
#include <ctype.h>
#include <inttypes.h>
#include <limits.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sysexits.h>

static void __dead2
usage(void)
{

        fprintf(stderr, "usage: chkgrp [-q] [groupfile]\n");
        exit(EX_USAGE);
}

int
main(int argc, char *argv[])
{
        FILE *gf;
        unsigned long gid;
        unsigned int i;
        size_t len;
        int opt, quiet;
        int n = 0, k, e = 0;
        const char *cp, *f[4], *gfn, *p;
        char *line;

        quiet = 0;
        while ((opt = getopt(argc, argv, "q")) != -1) {
                switch (opt) {
                case 'q':
                        quiet = 1;
                        break;
                default:
                        usage();
                }
        }

        argc -= optind;
        argv += optind;

        if (argc == 0)
                gfn = "/etc/group";
        else if (argc == 1)
                gfn = argv[0];
        else
                usage();

        /* open group file */
        if ((gf = fopen(gfn, "r")) == NULL)
                err(EX_NOINPUT, "%s", gfn);

        /* check line by line */
        while (++n) {
                if ((line = fgetln(gf, &len)) == NULL)
                        break;
                if (len > 0 && line[len - 1] != '\n') {
                        warnx("%s: line %d: no newline character", gfn, n);
                        e = 1;
                }
                while (len && isspace(line[len-1]))
                        len--;

                /* ignore blank lines and comments */
                for (p = line; p < line + len; p++)
                        if (!isspace(*p)) break;
                if (!len || *p == '#')
                        continue;

                /*
                 * Hack: special case for + line
                 */
                if (strncmp(line, "+:::", len) == 0 ||
                    strncmp(line, "+:*::", len) == 0)
                        continue;

                /*
                 * A correct group entry has four colon-separated fields,
                 * the third of which must be entirely numeric and the
                 * fourth of which may be empty.
                 */
                for (i = k = 0; k < 4; k++) {
                        for (f[k] = line + i; i < len && line[i] != ':'; i++)
                                /* nothing */ ;
                        if (k < 3 && line[i] != ':')
                                break;
                        line[i++] = 0;
                }

                if (k < 4) {
                        warnx("%s: line %d: missing field(s)", gfn, n);
                        while (k < 4)
                                f[k++] = "";
                        e = 1;
                }

                for (cp = f[0] ; *cp ; cp++) {
                        if (!isalnum(*cp) && *cp != '.' && *cp != '_' &&
                            *cp != '-' && (cp > f[0] || *cp != '+')) {
                                warnx("%s: line %d: '%c' invalid character",
                                    gfn, n, *cp);
                                e = 1;
                        }
                }

                for (cp = f[3] ; *cp ; cp++) {
                        if (!isalnum(*cp) && *cp != '.' && *cp != '_' &&
                            *cp != '-' && *cp != ',') {
                                warnx("%s: line %d: '%c' invalid character",
                                    gfn, n, *cp);
                                e = 1;
                        }
                }

                /* check if fourth field ended with a colon */
                if (i < len) {
                        warnx("%s: line %d: too many fields", gfn, n);
                        e = 1;
                }
        
                /* check that none of the fields contain whitespace */
                for (k = 0; k < 4; k++) {
                        if (strcspn(f[k], " \t") != strlen(f[k])) {
                                warnx("%s: line %d: field %d contains whitespace",
                                    gfn, n, k+1);
                                e = 1;
                        }
                }

                /* check that the GID is numeric */
                if (strspn(f[2], "0123456789") != strlen(f[2])) {
                        warnx("%s: line %d: group id is not numeric", gfn, n);
                        e = 1;
                }

                /* check the range of the group id */
                errno = 0;
                gid = strtoul(f[2], NULL, 10);
                if (errno != 0) {
                        warnx("%s: line %d: strtoul failed", gfn, n);
                } else if (gid > GID_MAX) {
                        warnx("%s: line %d: group id is too large (%ju > %ju)",
                            gfn, n, (uintmax_t)gid, (uintmax_t)GID_MAX);
                        e = 1;
                }
        }

        /* check what broke the loop */
        if (ferror(gf))
                err(EX_IOERR, "%s: line %d", gfn, n);

        /* done */
        fclose(gf);
        if (e == 0 && quiet == 0)
                printf("%s is fine\n", gfn);
        exit(e ? EX_DATAERR : EX_OK);
}