/*      $OpenBSD: rmt.c,v 1.23 2019/06/28 13:32:50 deraadt Exp $        */

/*
 * Copyright (c) 1983 Regents of the University of California.
 * 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.
 * 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. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
 */

/*
 * rmt
 */
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/mtio.h>

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <limits.h>

int     tape = -1;

char    *record;
int     maxrecsize = -1;

#define STRSIZE 64
char    device[PATH_MAX];
char    lastdevice[PATH_MAX] = "";
char    count[STRSIZE], mode[STRSIZE], pos[STRSIZE], op[STRSIZE];

char    resp[BUFSIZ];

FILE    *debug;
#define DEBUG(f)        if (debug) fprintf(debug, f)
#define DEBUG1(f,a)     if (debug) fprintf(debug, f, a)
#define DEBUG2(f,a1,a2) if (debug) fprintf(debug, f, a1, a2)

char            *checkbuf(char *, int);
void            getstring(char *, int);
void            error(int);
__dead void     usage(void);

int
main(int argc, char *argv[])
{
        off_t orval;
        int rval;
        char c;
        int n, i, cc;
        int ch, rflag = 0, wflag = 0;
        int f, acc;
        mode_t m;
        char *dir = NULL;
        char *devp;
        size_t dirlen;

        if (pledge("stdio rpath wpath cpath inet", NULL) == -1)
                err(1, "pledge");

        while ((ch = getopt(argc, argv, "d:rw")) != -1) {
                switch (ch) {
                case 'd':
                        dir = optarg;
                        if (*dir != '/')
                                errx(1, "directory must be absolute");
                        break;
                case 'r':
                        rflag = 1;
                        break;
                case 'w':
                        wflag = 1;
                        break;
                default:
                        usage();
                        /* NOTREACHED */
                }
        }
        argc -= optind;
        argv += optind;

        if (rflag && wflag)
                usage();

        if (argc > 0) {
                debug = fopen(*argv, "w");
                if (debug == 0)
                        err(1, "cannot open debug file");
                setvbuf(debug, NULL, _IONBF, 0);
        }

        if (dir) {
                if (chdir(dir) != 0)
                        err(1, "chdir");
                dirlen = strlen(dir);
        }

top:
        errno = 0;
        rval = 0;
        if (read(STDIN_FILENO, &c, 1) != 1)
                exit(0);
        switch (c) {

        case 'O':
                if (tape >= 0)
                        (void) close(tape);
                getstring(device, sizeof(device));
                getstring(mode, sizeof(mode));
                DEBUG2("rmtd: O %s %s\n", device, mode);

                devp = device;
                f = atoi(mode);
                m = S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH;
                acc = f & O_ACCMODE;
                if (dir) {
                        /* Strip away valid directory prefix. */
                        if (strncmp(dir, devp, dirlen) == 0 &&
                            (devp[dirlen - 1] == '/' ||
                             devp[dirlen] == '/')) {
                             devp += dirlen;
                             while (*devp == '/')
                                devp++;
                        }
                        /* Don't allow directory traversal. */
                        if (strchr(devp, '/')) {
                                errno = EACCES;
                                goto ioerror;
                        }
                        f |= O_NOFOLLOW;
                }
                if (rflag) {
                        /*
                         * Only allow readonly open and ignore file
                         * creation requests.
                         */
                        if (acc != O_RDONLY) {
                                errno = EPERM;
                                goto ioerror;
                        }
                        f &= ~O_CREAT;
                } else if (wflag) {
                        /*
                         * Require, and force creation of, a nonexistent file,
                         * unless we are reopening the last opened file again,
                         * in which case it is opened read-only.
                         */
                        if (strcmp(devp, lastdevice) != 0) {
                                /*
                                 * Disallow read-only open since that would
                                 * only result in an empty file.
                                 */
                                if (acc == O_RDONLY) {
                                        errno = EPERM;
                                        goto ioerror;
                                }
                                f |= O_CREAT | O_EXCL;
                        } else {
                                acc = O_RDONLY;
                        }
                        /* Create readonly file */
                        m = S_IRUSR|S_IRGRP|S_IROTH;
                }
                /* Apply new access mode. */
                f = (f & ~O_ACCMODE) | acc;

                tape = open(devp, f, m);
                if (tape == -1)
                        goto ioerror;
                (void)strlcpy(lastdevice, devp, sizeof(lastdevice));
                goto respond;

        case 'C':
                DEBUG("rmtd: C\n");
                getstring(device, sizeof(device));      /* discard */
                if (close(tape) == -1)
                        goto ioerror;
                tape = -1;
                goto respond;

        case 'L':
                getstring(count, sizeof(count));
                getstring(pos, sizeof(pos));
                DEBUG2("rmtd: L %s %s\n", count, pos);
                orval = lseek(tape, strtoll(count, NULL, 0), atoi(pos));
                if (orval == -1)
                        goto ioerror;
                goto respond;

        case 'W':
                getstring(count, sizeof(count));
                n = atoi(count);
                DEBUG1("rmtd: W %s\n", count);
                record = checkbuf(record, n);
                for (i = 0; i < n; i += cc) {
                        cc = read(STDIN_FILENO, &record[i], n - i);
                        if (cc <= 0) {
                                DEBUG("rmtd: premature eof\n");
                                exit(2);
                        }
                }
                rval = write(tape, record, n);
                if (rval == -1)
                        goto ioerror;
                goto respond;

        case 'R':
                getstring(count, sizeof(count));
                DEBUG1("rmtd: R %s\n", count);
                n = atoi(count);
                record = checkbuf(record, n);
                rval = read(tape, record, n);
                if (rval == -1)
                        goto ioerror;
                (void) snprintf(resp, sizeof resp, "A%d\n", rval);
                (void) write(STDOUT_FILENO, resp, strlen(resp));
                (void) write(STDOUT_FILENO, record, rval);
                goto top;

        case 'I':
                getstring(op, sizeof(op));
                getstring(count, sizeof(count));
                DEBUG2("rmtd: I %s %s\n", op, count);
                { struct mtop mtop;
                  mtop.mt_op = atoi(op);
                  mtop.mt_count = atoi(count);
                  if (ioctl(tape, MTIOCTOP, (char *)&mtop) == -1)
                        goto ioerror;
                  rval = mtop.mt_count;
                }
                goto respond;

        case 'S':               /* status */
                DEBUG("rmtd: S\n");
                { struct mtget mtget;
                  if (ioctl(tape, MTIOCGET, (char *)&mtget) == -1)
                        goto ioerror;
                  rval = sizeof (mtget);
                  (void) snprintf(resp, sizeof resp, "A%d\n", rval);
                  (void) write(STDOUT_FILENO, resp, strlen(resp));
                  (void) write(STDOUT_FILENO, (char *)&mtget, sizeof (mtget));
                  goto top;
                }

        default:
                DEBUG1("rmtd: garbage command %c\n", c);
                exit(3);
        }
respond:
        DEBUG1("rmtd: A %d\n", rval);
        (void) snprintf(resp, sizeof resp, "A%d\n", rval);
        (void) write(STDOUT_FILENO, resp, strlen(resp));
        goto top;
ioerror:
        error(errno);
        goto top;
}

void
getstring(char *bp, int size)
{
        char *cp = bp;
        char *ep = bp + size - 1;

        do {
                if (read(STDIN_FILENO, cp, 1) != 1)
                        exit(0);
        } while (*cp != '\n' && ++cp < ep);
        *cp = '\0';
}

char *
checkbuf(char *record, int size)
{
        if (size <= maxrecsize)
                return (record);
        if (record != 0)
                free(record);
        record = malloc(size);
        if (record == 0) {
                DEBUG("rmtd: cannot allocate buffer space\n");
                exit(4);
        }
        maxrecsize = size;
        while (size > 1024 &&
            setsockopt(0, SOL_SOCKET, SO_RCVBUF, &size, sizeof (size)) == -1)
                size -= 1024;
        return (record);
}

void
error(int num)
{

        DEBUG2("rmtd: E %d (%s)\n", num, strerror(num));
        (void) snprintf(resp, sizeof (resp), "E%d\n%s\n", num, strerror(num));
        (void) write(STDOUT_FILENO, resp, strlen(resp));
}

__dead void
usage(void)
{
        extern char *__progname;

        (void)fprintf(stderr, "usage: %s [-r | -w] [-d directory]\n",
            __progname);
        exit(1);
}