/*
 * Copyright (c) 1990, 2010, Oracle and/or its affiliates. All rights reserved.
 */

/*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*        All Rights Reserved   */

/*
 * Copyright (c) 1985 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 */

#include "lint.h"
#include <sys/types.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <ctype.h>
#include <stdio.h>
#include <limits.h>
#include <stdlib.h>
#include <sys/file.h>
#include "libc.h"
#include <unistd.h>

#define SHELLS "/etc/shells"

/*
 * Do not add local shells here.  They should be added in /etc/shells
 *
 * Do not add restricted shells:
 * Shells returned by getusershell traditionally allow:
 * - users to change away from (i.e., if you have an rksh in
 *   getusershell(), then users can change their shell to ksh)
 * - by default, ftp in is allowed only for shells returned by
 *   getusershell(); since FTP has no restrictions on directory
 *   movement, adding rksh to getusershell() would defeat that
 *   protection.
 */
const char *okshells[] = {
        "/usr/bin/sh",
        "/usr/bin/csh",
        "/usr/bin/ksh",
        "/usr/bin/ksh93",
        "/usr/bin/jsh",
        "/bin/sh",
        "/bin/csh",
        "/bin/ksh",
        "/bin/ksh93",
        "/bin/jsh",
        "/sbin/sh",
        "/sbin/jsh",
        "/usr/bin/pfsh",
        "/usr/bin/pfcsh",
        "/usr/bin/pfksh",
        "/usr/bin/pfksh93",
        "/usr/bin/bash",
        "/usr/bin/tcsh",
        "/usr/bin/zsh",
        "/usr/bin/pfbash",
        "/usr/bin/pftcsh",
        "/usr/bin/pfzsh",
        "/bin/pfsh",
        "/bin/pfcsh",
        "/bin/pfksh",
        "/bin/pfksh93",
        "/bin/bash",
        "/bin/tcsh",
        "/bin/zsh",
        "/bin/pfbash",
        "/bin/pftcsh",
        "/bin/pfzsh",
        "/usr/xpg4/bin/sh",
        "/usr/xpg4/bin/pfsh",
        "/sbin/pfsh",
        "/usr/sfw/bin/zsh",
        NULL
};

static char **shells, *strings;
static char **curshell;
static char **initshells(void);

/*
 * Get a list of shells from SHELLS, if it exists.
 */
char *
getusershell(void)
{
        char *ret;

        if (curshell == NULL)
                curshell = initshells();
        ret = *curshell;
        if (ret != NULL)
                curshell++;
        return (ret);
}

void
endusershell(void)
{

        if (shells != NULL)
                (void) free((char *)shells);
        shells = NULL;
        if (strings != NULL)
                (void) free(strings);
        strings = NULL;
        curshell = NULL;
}

void
setusershell(void)
{

        curshell = initshells();
}

static char **
initshells(void)
{
        char **sp, *cp;
        FILE *fp;
        struct stat statb;

        if (shells != NULL)
                (void) free((char *)shells);
        shells = NULL;
        if (strings != NULL)
                (void) free(strings);
        strings = NULL;
        if ((fp = fopen(SHELLS, "rF")) == (FILE *)0)
                return ((char **)okshells);
        /*
         * The +1 in the malloc() below is needed to handle the final
         * fgets() NULL terminator.  From fgets(3C):
         *
         * char *fgets(char *s, int n, FILE *stream);
         *
         * The  fgets()  function reads characters from the stream into
         * the array pointed to by s, until n-1 characters are read, or
         * a newline character is read and transferred to s, or an end-
         * of-file condition is encountered.  The string is then termi-
         * nated with a null character.
         */
        if ((fstat(fileno(fp), &statb) == -1) || (statb.st_size > LONG_MAX) ||
            ((strings = malloc((size_t)statb.st_size + 1)) == NULL)) {
                (void) fclose(fp);
                return ((char **)okshells);
        }
        shells = calloc((size_t)statb.st_size / 3, sizeof (char *));
        if (shells == NULL) {
                (void) fclose(fp);
                (void) free(strings);
                strings = NULL;
                return ((char **)okshells);
        }
        sp = shells;
        cp = strings;
        while (fgets(cp, MAXPATHLEN + 1, fp) != NULL) {
                while (*cp != '#' && *cp != '/' && *cp != '\0')
                        cp++;
                if (*cp == '#' || *cp == '\0')
                        continue;
                *sp++ = cp;
                while (!isspace(*cp) && *cp != '#' && *cp != '\0')
                        cp++;
                *cp++ = '\0';
        }
        *sp = (char *)0;
        (void) fclose(fp);
        return (shells);
}