/* $OpenBSD: modpipe.c,v 1.9 2026/03/06 07:06:45 dtucker Exp $ */

/*
 * Copyright (c) 2012 Damien Miller <djm@mindrot.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <err.h>
#include <errno.h>

static void
usage(void)
{
        fprintf(stderr, "Usage: modpipe -w [-m modspec ...] < in > out\n");
        fprintf(stderr, "modspec is one of:\n");
        fprintf(stderr, "    xor:offset:value       - XOR \"value\" at \"offset\"\n");
        fprintf(stderr, "    andor:offset:val1:val2 - AND \"val1\" then OR \"val2\" at \"offset\"\n");
        exit(1);
}

#define MAX_MODIFICATIONS 256
struct modification {
        enum { MOD_XOR, MOD_AND_OR } what;
        unsigned long long offset;
        uint8_t m1, m2;
};

static void
parse_modification(const char *s, struct modification *m)
{
        char what[16+1];
        int n, m1, m2;

        bzero(m, sizeof(*m));
        if ((n = sscanf(s, "%16[^:]%*[:]%llu%*[:]%i%*[:]%i",
            what, &m->offset, &m1, &m2)) < 3)
                errx(1, "Invalid modification spec \"%s\"", s);
        if (strcasecmp(what, "xor") == 0) {
                if (n > 3)
                        errx(1, "Invalid modification spec \"%s\"", s);
                if (m1 < 0 || m1 > 0xff)
                        errx(1, "Invalid XOR modification value");
                m->what = MOD_XOR;
                m->m1 = m1;
        } else if (strcasecmp(what, "andor") == 0) {
                if (n != 4)
                        errx(1, "Invalid modification spec \"%s\"", s);
                if (m1 < 0 || m1 > 0xff)
                        errx(1, "Invalid AND modification value");
                if (m2 < 0 || m2 > 0xff)
                        errx(1, "Invalid OR modification value");
                m->what = MOD_AND_OR;
                m->m1 = m1;
                m->m2 = m2;
        } else
                errx(1, "Invalid modification type \"%s\"", what);
}

int
main(int argc, char **argv)
{
        int ch;
        u_char buf[8192];
        size_t total;
        ssize_t r, s, o;
        struct modification mods[MAX_MODIFICATIONS];
        u_int i, wflag = 0, num_mods = 0;

        while ((ch = getopt(argc, argv, "wm:")) != -1) {
                switch (ch) {
                case 'm':
                        if (num_mods >= MAX_MODIFICATIONS)
                                errx(1, "Too many modifications");
                        parse_modification(optarg, &(mods[num_mods++]));
                        break;
                case 'w':
                        wflag = 1;
                        break;
                default:
                        usage();
                        /* NOTREACHED */
                }
        }
        for (total = 0;;) {
                r = s = read(STDIN_FILENO, buf, sizeof(buf));
                if (r == 0)
                        break;
                if (r < 0) {
                        if (errno == EAGAIN || errno == EINTR)
                                continue;
                        err(1, "read");
                }
                for (i = 0; i < num_mods; i++) {
                        if (mods[i].offset < total ||
                            mods[i].offset >= total + s)
                                continue;
                        switch (mods[i].what) {
                        case MOD_XOR:
                                buf[mods[i].offset - total] ^= mods[i].m1;
                                break;
                        case MOD_AND_OR:
                                buf[mods[i].offset - total] &= mods[i].m1;
                                buf[mods[i].offset - total] |= mods[i].m2;
                                break;
                        }
                }
                for (o = 0; o < s; o += r) {
                        r = write(STDOUT_FILENO, buf + o, s - o);
                        if (r == 0)
                                break;
                        if (r < 0) {
                                if (errno == EAGAIN || errno == EINTR)
                                        continue;
                                err(1, "write");
                        }
                }
                total += s;
        }
        /* Warn if modifications not reached in input stream */
        r = 0;
        for (i = 0; wflag && i < num_mods; i++) {
                if (mods[i].offset < total)
                        continue;
                r = 1;
                fprintf(stderr, "modpipe: warning - mod %u not reached\n", i);
        }
        return r;
}