/* SPDX-License-Identifier: MIT */
/* Copyright (c) 2022-2026 Leah Rowe <leah@libreboot.org> */
/* Copyright (c) 2023 Riku Viitanen <riku.viitanen@protonmail.com> */

#include <sys/stat.h>

#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

static void reset_global_state(void);
static void set_cmd(int, char **);
static void check_cmd_args(int, char **);
static void set_io_flags(int, char **);
static void open_files(void);
static void xopen(int *, const char *, int, struct stat *);
static void read_gbe(void);
static void read_gbe_part(int, int);
static void cmd_setmac(void);
static void parse_mac_string(void);
static void set_mac_byte(int);
static void check_mac_separator(int);
static void set_mac_nib(int, int);
static uint8_t hextonum(char);
static uint8_t rhex(void);
static void read_file_PERFECTLY_or_die(int, void *, size_t,
    off_t, const char *, const char *);
static int check_read_or_die(const char *,
    ssize_t, size_t, int, const char *);
static int write_mac_part(int);
static void cmd_dump(void);
static void print_mac_address(int);
static void hexdump(int);
static void cmd_setchecksum(void);
static void cmd_brick(void);
static void cmd_copy(void);
static void cmd_swap(void);
static int good_checksum(int);
static uint16_t word(size_t, int);
static void set_word(size_t, int, uint16_t);
static void check_bound(size_t, int);
static void write_gbe(void);
static void write_gbe_part(int);
static off_t gbe_bound(int, const char *);
static void usage(void);
static void err(int, const char *, ...);
static const char *getnvmprogname(void);
static void set_err(int);

#if defined(__OpenBSD__) || defined(__FreeBSD__) || \
    defined(__NetBSD__) || defined(__APPLE__) || \
    defined(__DragonFly__)
#ifndef HAVE_ARC4RANDOM
#define HAVE_ARC4RANDOM
#endif
#endif

#define NVM_CHECKSUM 0xBABA
#define NVM_CHECKSUM_WORD 0x3F
#define NVM_SIZE 128

#define SIZE_1KB 1024
#define SIZE_4KB (4 * SIZE_1KB)
#define SIZE_8KB (8 * SIZE_1KB)
#define SIZE_16KB (16 * SIZE_1KB)
#define SIZE_128KB (128 * SIZE_1KB)

#define MAX_RETRY_READ 30

#define items(x) (sizeof((x)) / sizeof((x)[0]))

static const char newrandom[] = "/dev/urandom";
static const char oldrandom[] = "/dev/random"; /* fallback on OLD unix */
#ifndef HAVE_ARC4RANDOM
static const char *rname = NULL;
#endif

static uint8_t buf[SIZE_8KB];
static uint16_t macbuf[3];
static off_t partsize;

static int flags;
#ifndef HAVE_ARC4RANDOM
static int rfd = -1;
#endif
static int fd = -1;
static struct stat st;
static int part;
static int invert;
static int part_modified[2];

static const char *mac = NULL;
static const char rmac[] = "xx:xx:xx:xx:xx:xx";
static const char *fname = "";
static const char *argv0;

struct op {
	const char *str;
	void (*cmd)(void);
	int args;
};
static const struct op ops[] = {
	{ "dump", cmd_dump, 3 },
	{ "setmac", cmd_setmac, 3 },
	{ "swap", cmd_swap, 3 },
	{ "copy", cmd_copy, 4 },
	{ "brick", cmd_brick, 4 },
	{ "setchecksum", cmd_setchecksum, 4 },
};

static void (*cmd)(void) = NULL;

int
main(int argc, char *argv[])
{
	argv0 = argv[0];
	if (argc < 2)
		usage();

	reset_global_state();
	fname = argv[1];

#ifdef __OpenBSD__
	if (pledge("stdio rpath wpath unveil", NULL) == -1)
		err(ECANCELED, "pledge");

	/*
	 * For restricted filesystem access on early error.
	 *
	 * Unveiling the random device early, regardless of
	 * whether we will use it, prevents operations on any
	 * GbE files until we permit it, while performing the
	 * prerequisite error checks.
	 *
	 * We don't actually use the random device on platforms
	 * that have arc4random, which includes OpenBSD.
	 */
	if (unveil("/dev/urandom", "r") == -1)
		err(ECANCELED, "unveil '/dev/urandom'");
	if (unveil("/dev/random", "r") == -1)
		err(ECANCELED, "unveil '/dev/random'");
#endif

	set_cmd(argc, argv);
	check_cmd_args(argc, argv);
	set_io_flags(argc, argv);

#ifdef __OpenBSD__
	if (flags == O_RDONLY) {
		if (unveil(fname, "r") == -1)
			err(ECANCELED, "unveil ro '%s'", fname);
		if (unveil(NULL, NULL) == -1)
			err(ECANCELED, "unveil block (ro)");
		if (pledge("stdio rpath", NULL) == -1)
			err(ECANCELED, "pledge ro (kill unveil)");
	} else {
		if (unveil(fname, "rw") == -1)
			err(ECANCELED, "unveil rw '%s'", fname);
		if (unveil(NULL, NULL) == -1)
			err(ECANCELED, "unveil block (rw)");
		if (pledge("stdio rpath wpath", NULL) == -1)
			err(ECANCELED, "pledge rw (kill unveil)");
	}
#endif

	open_files();

#ifdef __OpenBSD__
	if (pledge("stdio", NULL) == -1)
		err(ECANCELED, "pledge stdio (main)");
#endif

	read_gbe();
	(*cmd)();
	write_gbe();

	if (close(fd) == -1)
		err(ECANCELED, "close '%s'", fname);
#ifndef HAVE_ARC4RANDOM
	if (close(rfd) == -1)
		err(ECANCELED, "close '%s'", rname);
#endif

	if (cmd != cmd_dump) {
		if (errno)
			err(ECANCELED, "Unhandled error on exit");
	}

	if (errno)
		return EXIT_FAILURE;
	else
		return EXIT_SUCCESS;
}

/*
 * Currently redundant, because the program only runs
 * once, but I plan to expand this tool so that it can
 * work on multiple files, using getop switches as args.
 */
static void
reset_global_state(void)
{
	errno = 0;

	mac = NULL;
	invert = 0;
	part_modified[0] = 0;
	part_modified[1] = 0;
	fname = "";
	cmd = NULL;
	fd = -1;
#ifndef HAVE_ARC4RANDOM
	rfd = -1;
#endif
	part = 0;

	memset(macbuf, 0, sizeof(macbuf));
	memset(buf, 0, sizeof(buf));
}

static void
set_cmd(int argc, char *argv[])
{
	size_t i;

	if (argc == 2) {
		cmd = cmd_setmac;
		return;
	}

	for (i = 0; i < items(ops) && cmd == NULL; i++) {
		if (strcmp(argv[2], ops[i].str) != 0)
			continue;
		if (argc >= ops[i].args) {
			cmd = ops[i].cmd;
			break;
		}
		err(EINVAL, "Too few args: command '%s'", ops[i].str);
	}
}

static void
check_cmd_args(int argc, char *argv[])
{
	if (cmd == NULL && argc > 2) { /* nvm gbe [MAC] */
		mac = argv[2];
		cmd = cmd_setmac;
	} else if (cmd == cmd_setmac) { /* nvm gbe setmac [MAC] */
		mac = rmac; /* random MAC */
		if (argc > 3)
			mac = argv[3];
	} else if (cmd != NULL && argc > 3) { /* user-supplied partnum */
		part = argv[3][0] - '0';
		if (!((part == 0 || part == 1) && argv[3][1] == '\0'))
			err(EINVAL, "Bad partnum: %s", argv[3]);
	}

	if (cmd == NULL)
		err(EINVAL, "Bad command");
}

static void
set_io_flags(int argc, char *argv[])
{
	flags = O_RDWR;
	if (argc < 3)
		return;
	if (strcmp(argv[2], "dump") == 0)
		flags = O_RDONLY;
}

static void
open_files(void)
{
#ifndef HAVE_ARC4RANDOM
	struct stat st_rfd;
	rname = newrandom;
	if ((rfd = open(rname, O_RDONLY)) == -1) {
		/*
		 * Fall back to /dev/random on old platforms
		 * where /dev/urandom does not exist.
		 */
		rname = oldrandom;
		xopen(&rfd, rname, O_RDONLY, &st_rfd);
	}
#endif
	xopen(&fd, fname, flags, &st);

	switch(st.st_size) {
	case SIZE_8KB:
	case SIZE_16KB:
	case SIZE_128KB:
		partsize = st.st_size >> 1;
		break;
	default:
		err(ECANCELED, "File size must be 8KB, 16KB or 128KB");
		break;
	}
}

static void
xopen(int *f, const char *l, int p, struct stat *st)
{
	if ((*f = open(l, p)) == -1)
		err(ECANCELED, "%s", l);
	if (fstat(*f, st) == -1)
		err(ECANCELED, "%s", l);
}

static void
read_gbe(void)
{
	int p;
	int do_read[2] = {1, 1};

	if (cmd == cmd_copy || cmd == cmd_brick || cmd == cmd_setchecksum)
		do_read[part ^ 1] = 0;

	/*
	 * speedhack: if copy/swap, flip where data gets written to memory,
	 * so that cmd_copy and cmd_swap don't have to work on every word
	 */
	if (cmd == cmd_copy || cmd == cmd_swap)
		invert = 1;

	for (p = 0; p < 2; p++) {
		if (do_read[p])
			read_gbe_part(p, invert);
	}
}

static void
read_gbe_part(int p, int invert)
{
	read_file_PERFECTLY_or_die(fd, buf + (SIZE_4KB * (p ^ invert)),
	    SIZE_4KB, gbe_bound(p, "pread"), fname, "pread");
}

static void
cmd_setmac(void)
{
	int partnum;
	int mac_updated = 0;

	parse_mac_string();
	printf("MAC address to be written: %s\n", mac);

	for (partnum = 0; partnum < 2; partnum++)
		mac_updated |= write_mac_part(partnum);
	if (mac_updated)
		errno = 0;
}

static void
parse_mac_string(void)
{
	int mac_pos;

	if (strlen(mac) != 17)
		err(EINVAL, "MAC address is the wrong length");

	for (mac_pos = 0; mac_pos < 16; mac_pos += 3)
		set_mac_byte(mac_pos);

	if ((macbuf[0] | macbuf[1] | macbuf[2]) == 0)
		err(EINVAL, "Must not specify all-zeroes MAC address");
	if (macbuf[0] & 1)
		err(EINVAL, "Must not specify multicast MAC address");
}

static void
set_mac_byte(int mac_pos)
{
	int nib;
	check_mac_separator(mac_pos);

	for (nib = 0; nib < 2; nib++)
		set_mac_nib(mac_pos, nib);
}

static void
check_mac_separator(int mac_pos)
{
	char separator;

	if (mac_pos == 15)
		return;
	if ((separator = mac[mac_pos + 2]) == ':')
		return;

	err(EINVAL, "Invalid MAC address separator '%c'", separator);
}

static void
set_mac_nib(int mac_pos, int nib)
{
	uint8_t h;
	int byte = mac_pos / 3;

	if ((h = hextonum(mac[mac_pos + nib])) > 15)
		err(EINVAL, "Invalid character '%c'",
		    mac[mac_pos + nib]);

	/* If random, ensure that local/unicast bits are set */
	if (byte == 0 && nib == 1) {
		if ((mac[mac_pos + nib] == '?') ||
		    (mac[mac_pos + nib] == 'x') ||
		    (mac[mac_pos + nib] == 'X')) /* random */
			h = (h & 0xE) | 2; /* local, unicast */
	}

	macbuf[byte >> 1] |= (uint16_t)h <<
	    (((byte & 1) << 3) + (4 * (nib ^ 1)));
}

static uint8_t
hextonum(char ch)
{
	if (ch >= '0' && ch <= '9')
		return ch - '0';
	else if (ch >= 'A' && ch <= 'F')
		return ch - 'A' + 10;
	else if (ch >= 'a' && ch <= 'f')
		return ch - 'a' + 10;
	else if (ch == '?' || ch == 'x' || ch == 'X')
		return rhex(); /* random hex value */
	else
		return 16; /* error: invalid character */
}

static uint8_t
rhex(void)
{
	static uint8_t rnum[12];
	static size_t n = 0;

	if (!n) {
		n = sizeof(rnum);
#ifdef HAVE_ARC4RANDOM
		arc4random_buf(rnum, n);
#else
		read_file_PERFECTLY_or_die(rfd, rnum, n, 0, rname, NULL);
#endif
	}

	return rnum[--n] & 0xf;
}

static void
read_file_PERFECTLY_or_die(int fd, void *buf, size_t len,
    off_t off, const char *path, const char *op)
{
	int retry;
	ssize_t rval;

	for (retry = 0; retry < MAX_RETRY_READ; retry++) {
		if (op == NULL)
			rval = read(fd, buf, len);
		else
			rval = pread(fd, buf, len, off);

		if (check_read_or_die(path, rval, len, retry,
		    op ? op : "read"))
			return;
	}

	err(EINTR, "%s: max retries exceeded on file: %s",
	    op ? op : "read", path);
}

static int
check_read_or_die(const char *rpath, ssize_t rval, size_t rsize,
    int retry, const char *readtype)
{
	if (rval == (ssize_t)rsize) {
		errno = 0;
		return 1; /* Successful read */
	}

	if (rval != -1)
		err(ECANCELED, "Short %s, %zd bytes, on file: %s",
		    readtype, rval, rpath);
	if (errno != EINTR)
		err(ECANCELED, "Could not %s file: '%s'", readtype, rpath);
	if (retry == MAX_RETRY_READ - 1)
		err(EINTR, "%s: max retries exceeded on file: %s",
		    readtype, rpath);

	/*
	 * Bad read, with errno EINTR (syscall interrupted).
	 */
	return 0;
}

static int
write_mac_part(int partnum)
{
	size_t w;

	part = partnum;
	if (!good_checksum(partnum))
		return 0;

	for (w = 0; w < 3; w++)
		set_word(w, partnum, macbuf[w]);

	printf("Wrote MAC address to part %d: ", partnum);
	print_mac_address(partnum);

	cmd_setchecksum();
	return 1;
}

static void
cmd_dump(void)
{
	int partnum;
	int num_invalid = 0;

	for (partnum = 0; partnum < 2; partnum++) {
		if (!good_checksum(partnum))
			++num_invalid;

		printf("MAC (part %d): ", partnum);
		print_mac_address(partnum);
		hexdump(partnum);
	}

	if (num_invalid < 2)
		errno = 0;
}

static void
print_mac_address(int partnum)
{
	size_t c;
	for (c = 0; c < 3; c++) {
		uint16_t val16 = word(c, partnum);
		printf("%02x:%02x", val16 & 0xff, val16 >> 8);
		if (c == 2)
			printf("\n");
		else
			printf(":");
	}
}

static void
hexdump(int partnum)
{
	size_t c;
	size_t row;
	uint16_t val16;

	for (row = 0; row < 8; row++) {
		printf("%08lx ", row << 4);
		for (c = 0; c < 8; c++) {
			val16 = word((row << 3) + c, partnum);
			if (c == 4)
				printf(" ");
			printf(" %02x %02x", val16 & 0xff, val16 >> 8);
		}
		printf("\n");
	}
}

static void
cmd_setchecksum(void)
{
	size_t c;
	uint16_t val16 = 0;

	for (c = 0; c < NVM_CHECKSUM_WORD; c++)
		val16 += word(c, part);

	set_word(NVM_CHECKSUM_WORD, part, NVM_CHECKSUM - val16);
}

static void
cmd_brick(void)
{
	uint16_t checksum_word;

	if (!good_checksum(part)) {
		err(ECANCELED,
		    "Part %d checksum already invalid in file '%s'",
		    part, fname);
	}

	/*
	 * We know checksum_word is valid, so we need only
	 * flip one bit to invalidate it.
	 */
	checksum_word = word(NVM_CHECKSUM_WORD, part);
	set_word(NVM_CHECKSUM_WORD, part, checksum_word ^ 1);
}

static void
cmd_copy(void)
{
	if (!good_checksum(part ^ 1))
		err(ECANCELED, "copy p%d, file '%s'", part ^ 1, fname);

	/*
	 * SPEED HACK:
	 *
	 * read_gbe() already performed the copy,
	 * by virtue of inverted read. We need
	 * only set the other part as changed.
	 */
	part_modified[part ^ 1] = 1;
}

static void
cmd_swap(void)
{
	if (!(good_checksum(0) || good_checksum(1)))
		err(ECANCELED, "swap parts, file '%s'", fname);

	/*
	 * good_checksum() can set errno, if one
	 * of the parts is bad. We will reset it.
	 */
	errno = 0;

	/*
	 * SPEED HACK:
	 *
	 * read_gbe() already performed the swap,
	 * by virtue of inverted read. We need
	 * only set both parts as changed.
	 */
	part_modified[1] = part_modified[0] = 1;
}

static int
good_checksum(int partnum)
{
	size_t w;
	uint16_t total = 0;
	for (w = 0; w <= NVM_CHECKSUM_WORD; w++)
		total += word(w, partnum);

	if (total == NVM_CHECKSUM)
		return 1;

	fprintf(stderr, "WARNING: BAD checksum in part %d\n",
	    partnum ^ invert);

	set_err(ECANCELED);
	return 0;
}

/*
 * GbE NVM files store 16-bit (2-byte) little-endian words.
 * We must therefore swap the order when reading or writing.
 */

static uint16_t
word(size_t pos16, int p)
{
	size_t pos;

	check_bound(pos16, p);
	pos = (pos16 << 1) + ((size_t)p * SIZE_4KB);

	return (uint16_t)buf[pos] | ((uint16_t)buf[pos + 1] << 8);
}

static void
set_word(size_t pos16, int p, uint16_t val16)
{
	size_t pos;

	check_bound(pos16, p);
	pos = (pos16 << 1) + ((size_t)p * SIZE_4KB);

	buf[pos] = (uint8_t)(val16 & 0xff);
	buf[pos + 1] = (uint8_t)(val16 >> 8);

	part_modified[p] = 1;
}

static void
check_bound(size_t c, int p)
{
	/*
	 * NVM_SIZE assumed as the limit, because the
	 * current design assumes that we will only
	 * ever modified the NVM area.
	 *
	 * The only exception is copy/swap, but these
	 * do not use word/set_word and therefore do
	 * not cause check_bound() to be called.
	 *
	 * TODO:
	 * This should be adjusted in the future, if
	 * we ever wish to work on the extented area.
	 */

	if (p != 0 && p != 1)
		err(EINVAL, "check_bound: invalid partnum %d", p);
	if (c >= (NVM_SIZE >> 1))
		err(EINVAL, "check_bound: out of bounds %zu", c);
}

static void
write_gbe(void)
{
	int p;

	if (flags == O_RDONLY)
		return;

	for (p = 0; p < 2; p++) {
		if (part_modified[p])
			write_gbe_part(p);
	}
}

static void
write_gbe_part(int p)
{
	if (pwrite(fd, buf + (SIZE_4KB * p),
	    SIZE_4KB, gbe_bound(p, "pwrite")) != (ssize_t)SIZE_4KB) {
		err(ECANCELED,
		    "Can't write %d b to '%s' p%d", SIZE_4KB, fname, p);
	}
}

/*
 * Reads to GbE from write_gbe_part and read_gbe_part
 * are filtered through here. These operations must
 * only write from the 0th position or the half position
 * within the GbE file, and write 4KB of data.
 *
 * This check is called, to ensure just that.
 */
static off_t
gbe_bound(int p, const char *f_op)
{
	off_t off = (off_t)p * partsize;

	if (off + SIZE_4KB > st.st_size)
		err(ECANCELED, "GbE file %s out of bounds: %s", f_op, fname);

	if (off != 0 && off != st.st_size >> 1)
		err(ECANCELED, "GbE file %s at bad offset: %s", f_op, fname);

	return off;
}

static void
usage(void)
{
	const char *util = getnvmprogname();

#ifdef __OpenBSD__
	if (pledge("stdio", NULL) == -1)
		err(ECANCELED, "pledge");
#endif
	fprintf(stderr,
	    "Modify Intel GbE NVM images e.g. set MAC\n"
	    "USAGE:\n"
	    "\t%s FILE dump\n"
	    "\t%s FILE   # same as setmac without [MAC]\n"
	    "\t%s FILE setmac [MAC]\n"
	    "\t%s FILE swap\n"
	    "\t%s FILE copy 0|1\n"
	    "\t%s FILE brick 0|1\n"
	    "\t%s FILE setchecksum 0|1\n",
	    util, util, util, util, util, util, util);

	err(ECANCELED, "Too few arguments");
}

static void
err(int nvm_errval, const char *msg, ...)
{
	va_list args;

	fprintf(stderr, "%s: ", getnvmprogname());

	va_start(args, msg);
	vfprintf(stderr, msg, args);
	va_end(args);

	set_err(nvm_errval);
	fprintf(stderr, ": %s", strerror(errno));

	fprintf(stderr, "\n");
	exit(EXIT_FAILURE);
}

static const char *
getnvmprogname(void)
{
	const char *p;

	if (argv0 == NULL || *argv0 == '\0')
		return "";

	p = strrchr(argv0, '/');

	if (p)
		return p + 1;
	else
		return argv0;
}

static void
set_err(int x)
{
	if (errno)
		return;
	if (x)
		errno = x;
	else
		errno = ECANCELED;
}