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For open/openat, if the flags parameter does not contain O_CREAT, the
3rd (variadic) mode_t parameter is irrelevant.  Many developers in the past
have passed mode_t (0, 044, 0644, or such), which might lead future people
to copy this broken idiom, and perhaps even believe this parameter has some
meaning or implication or application. Delete them all.
This comes out of a conversation where tb@ noticed that a strange (but
intentional) pledge behaviour is to always knock-out high-bits from
mode_t on a number of system calls as a safety factor, and his bewilderment
that this appeared to be happening against valid modes (at least visually),
but no sorry, they are all irrelevant junk.  They could all be 0xdeafbeef.
ok millert

/*	$OpenBSD: dd.c,v 1.28 2021/10/24 21:24:21 deraadt Exp $	*/
/*	$NetBSD: dd.c,v 1.6 1996/02/20 19:29:06 jtc Exp $	*/

/*-
 * Copyright (c) 1991, 1993, 1994
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Keith Muller of the University of California, San Diego and Lance
 * Visser of Convex Computer Corporation.
 *
 * 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.
 */

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

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

#include "dd.h"
#include "extern.h"

static void dd_close(void);
static void dd_in(void);
static void getfdtype(IO *);
static void setup(void);

#define MAXIMUM(a, b)	(((a) > (b)) ? (a) : (b))

IO	in, out;		/* input/output state */
STAT	st;			/* statistics */
void	(*cfunc)(void);		/* conversion function */
size_t	cpy_cnt;		/* # of blocks to copy */
u_int	ddflags;		/* conversion options */
size_t	cbsz;			/* conversion block size */
size_t	files_cnt = 1;		/* # of files to copy */
const	u_char	*ctab;		/* conversion table */

int
main(int argc, char *argv[])
{
	jcl(argv);
	setup();

	(void)signal(SIGINFO, summaryx);
	(void)signal(SIGINT, terminate);

	atexit(summary);

	if (cpy_cnt != (size_t)-1) {
		while (files_cnt--)
			dd_in();
	}

	dd_close();
	exit(0);
}

static void
setup(void)
{
	if (in.name == NULL) {
		in.name = "stdin";
		in.fd = STDIN_FILENO;
	} else {
		in.fd = open(in.name, O_RDONLY);
		if (in.fd == -1)
			err(1, "%s", in.name);
	}

	getfdtype(&in);

	if (files_cnt > 1 && !(in.flags & ISTAPE))
		errx(1, "files is not supported for non-tape devices");

	if (out.name == NULL) {
		/* No way to check for read access here. */
		out.fd = STDOUT_FILENO;
		out.name = "stdout";
	} else {
#define	OFLAGS \
    (O_CREAT | (ddflags & (C_SEEK | C_NOTRUNC) ? 0 : O_TRUNC))
		out.fd = open(out.name, O_RDWR | OFLAGS, DEFFILEMODE);
		/*
		 * May not have read access, so try again with write only.
		 * Without read we may have a problem if output also does
		 * not support seeks.
		 */
		if (out.fd == -1) {
			out.fd = open(out.name, O_WRONLY | OFLAGS, DEFFILEMODE);
			out.flags |= NOREAD;
		}
		if (out.fd == -1)
			err(1, "%s", out.name);
	}

	getfdtype(&out);

	/*
	 * Allocate space for the input and output buffers.  If not doing
	 * record oriented I/O, only need a single buffer.
	 */
	if (!(ddflags & (C_BLOCK|C_UNBLOCK))) {
		if ((in.db = malloc(out.dbsz + in.dbsz - 1)) == NULL)
			err(1, "input buffer");
		out.db = in.db;
	} else {
		in.db = malloc(MAXIMUM(in.dbsz, cbsz) + cbsz);
		if (in.db == NULL)
			err(1, "input buffer");
		out.db = malloc(out.dbsz + cbsz);
		if (out.db == NULL)
			err(1, "output buffer");
	}
	in.dbp = in.db;
	out.dbp = out.db;

	/* Position the input/output streams. */
	if (in.offset)
		pos_in();
	if (out.offset)
		pos_out();

	if (pledge("stdio", NULL) == -1)
		err(1, "pledge");

	/*
	 * Truncate the output file; ignore errors because it fails on some
	 * kinds of output files, tapes, for example.
	 */
	if ((ddflags & (C_OF | C_SEEK | C_NOTRUNC)) == (C_OF | C_SEEK))
		(void)ftruncate(out.fd, out.offset * out.dbsz);

	/*
	 * If converting case at the same time as another conversion, build a
	 * table that does both at once.  If just converting case, use the
	 * built-in tables.
	 */
	if (ddflags & (C_LCASE|C_UCASE)) {
#ifdef	NO_CONV
		/* Should not get here, but just in case... */
		errx(1, "case conv and -DNO_CONV");
#else	/* NO_CONV */
		u_int cnt;
		if (ddflags & C_ASCII || ddflags & C_EBCDIC) {
			if (ddflags & C_LCASE) {
				for (cnt = 0; cnt < 0377; ++cnt)
					casetab[cnt] = tolower(ctab[cnt]);
			} else {
				for (cnt = 0; cnt < 0377; ++cnt)
					casetab[cnt] = toupper(ctab[cnt]);
			}
		} else {
			if (ddflags & C_LCASE) {
				for (cnt = 0; cnt < 0377; ++cnt)
					casetab[cnt] = tolower(cnt);
			} else {
				for (cnt = 0; cnt < 0377; ++cnt)
					casetab[cnt] = toupper(cnt);
			}
		}

		ctab = casetab;
#endif	/* NO_CONV */
	}

	/* Statistics timestamp. */
	clock_gettime(CLOCK_MONOTONIC, &st.start);
}

static void
getfdtype(IO *io)
{
	struct mtget mt;
	struct stat sb;

	if (fstat(io->fd, &sb))
		err(1, "%s", io->name);
	if (S_ISCHR(sb.st_mode))
		io->flags |= ioctl(io->fd, MTIOCGET, &mt) ? ISCHR : ISTAPE;
	if (S_ISFIFO(sb.st_mode) || S_ISSOCK(sb.st_mode))
		io->flags |= ISPIPE;
}

static void
swapbytes(void *v, size_t len)
{
	unsigned char *p = v;
	unsigned char t;

	while (len > 1) {
		t = p[0];
		p[0] = p[1];
		p[1] = t;
		p += 2;
		len -= 2;
	}
}


static void
dd_in(void)
{
	ssize_t n;

	for (;;) {
		if (cpy_cnt && (st.in_full + st.in_part) >= cpy_cnt)
			return;

		/*
		 * Zero the buffer first if sync; if doing block operations
		 * use spaces.
		 */
		if (ddflags & C_SYNC) {
			if (ddflags & (C_BLOCK|C_UNBLOCK))
				(void)memset(in.dbp, ' ', in.dbsz);
			else
				(void)memset(in.dbp, 0, in.dbsz);
		}

		n = read(in.fd, in.dbp, in.dbsz);
		if (n == 0) {
			in.dbrcnt = 0;
			return;
		}

		/* Read error. */
		if (n == -1) {
			/*
			 * If noerror not specified, die.  POSIX requires that
			 * the warning message be followed by an I/O display.
			 */
			if (!(ddflags & C_NOERROR))
				err(1, "%s", in.name);
			warn("%s", in.name);
			summary();

			/*
			 * If it's not a tape drive or a pipe, seek past the
			 * error.  If your OS doesn't do the right thing for
			 * raw disks this section should be modified to re-read
			 * in sector size chunks.
			 */
			if (!(in.flags & (ISPIPE|ISTAPE)) &&
			    lseek(in.fd, (off_t)in.dbsz, SEEK_CUR))
				warn("%s", in.name);

			/* If sync not specified, omit block and continue. */
			if (!(ddflags & C_SYNC))
				continue;

			/* Read errors count as full blocks. */
			in.dbcnt += in.dbrcnt = in.dbsz;
			++st.in_full;

		/* Handle full input blocks. */
		} else if (n == in.dbsz) {
			in.dbcnt += in.dbrcnt = n;
			++st.in_full;

		/* Handle partial input blocks. */
		} else {
			/* If sync, use the entire block. */
			if (ddflags & C_SYNC)
				in.dbcnt += in.dbrcnt = in.dbsz;
			else
				in.dbcnt += in.dbrcnt = n;
			++st.in_part;
		}

		/*
		 * POSIX states that if bs is set and no other conversions
		 * than noerror, notrunc or sync are specified, the block
		 * is output without buffering as it is read.
		 */
		if (ddflags & C_BS) {
			out.dbcnt = in.dbcnt;
			dd_out(1);
			in.dbcnt = 0;
			continue;
		}

		if (ddflags & C_SWAB) {
			if ((n = in.dbrcnt) & 1) {
				++st.swab;
				--n;
			}
			swapbytes(in.dbp, n);
		}

		in.dbp += in.dbrcnt;
		(*cfunc)();
	}
}

/*
 * Cleanup any remaining I/O and flush output.  If necessary, output file
 * is truncated.
 */
static void
dd_close(void)
{
	if (cfunc == def)
		def_close();
	else if (cfunc == block)
		block_close();
	else if (cfunc == unblock)
		unblock_close();
	if (ddflags & C_OSYNC && out.dbcnt && out.dbcnt < out.dbsz) {
		if (ddflags & (C_BLOCK|C_UNBLOCK))
			memset(out.dbp, ' ', out.dbsz - out.dbcnt);
		else
			memset(out.dbp, 0, out.dbsz - out.dbcnt);
		out.dbcnt = out.dbsz;
	}
	if (out.dbcnt)
		dd_out(1);
	if (ddflags & C_FSYNC) {
		if (fsync(out.fd) == -1)
			err(1, "fsync %s", out.name);
	}
}

void
dd_out(int force)
{
	static int warned;
	size_t cnt, n;
	ssize_t nw;
	u_char *outp;

	/*
	 * Write one or more blocks out.  The common case is writing a full
	 * output block in a single write; increment the full block stats.
	 * Otherwise, we're into partial block writes.  If a partial write,
	 * and it's a character device, just warn.  If a tape device, quit.
	 *
	 * The partial writes represent two cases.  1: Where the input block
	 * was less than expected so the output block was less than expected.
	 * 2: Where the input block was the right size but we were forced to
	 * write the block in multiple chunks.  The original versions of dd(1)
	 * never wrote a block in more than a single write, so the latter case
	 * never happened.
	 *
	 * One special case is if we're forced to do the write -- in that case
	 * we play games with the buffer size, and it's usually a partial write.
	 */
	outp = out.db;
	for (n = force ? out.dbcnt : out.dbsz;; n = out.dbsz) {
		for (cnt = n;; cnt -= nw) {
			nw = write(out.fd, outp, cnt);
			if (nw == 0)
				errx(1, "%s: end of device", out.name);
			if (nw == -1) {
				if (errno != EINTR)
					err(1, "%s", out.name);
				nw = 0;
			}
			outp += nw;
			st.bytes += nw;
			if (nw == n) {
				if (n != out.dbsz)
					++st.out_part;
				else
					++st.out_full;
				break;
			}
			++st.out_part;
			if (nw == cnt)
				break;
			if (out.flags & ISCHR && !warned) {
				warned = 1;
				warnx("%s: short write on character device",
				    out.name);
			}
			if (out.flags & ISTAPE)
				errx(1, "%s: short write on tape device", out.name);
		}
		if ((out.dbcnt -= n) < out.dbsz)
			break;
	}

	/* Reassemble the output block. */
	if (out.dbcnt)
		(void)memmove(out.db, out.dbp - out.dbcnt, out.dbcnt);
	out.dbp = out.db + out.dbcnt;
}