1/*
2 * Copyright (c) 2012 Damien Miller <djm@mindrot.org>
3 *
4 * Permission to use, copy, modify, and distribute this software for any
5 * purpose with or without fee is hereby granted, provided that the above
6 * copyright notice and this permission notice appear in all copies.
7 *
8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15 */
16
17/* $OpenBSD: modpipe.c,v 1.6 2013/11/21 03:16:47 djm Exp $ */
18
19#include "includes.h"
20
21#include <sys/types.h>
22#include <unistd.h>
23#include <stdio.h>
24#include <string.h>
25#include <stdarg.h>
26#include <stdlib.h>
27#include <errno.h>
28#ifdef HAVE_ERR_H
29# include <err.h>
30#endif
31#include "openbsd-compat/getopt_long.c"
32
33static void
34usage(void)
35{
36	fprintf(stderr, "Usage: modpipe -w [-m modspec ...] < in > out\n");
37	fprintf(stderr, "modspec is one of:\n");
38	fprintf(stderr, "    xor:offset:value       - XOR \"value\" at \"offset\"\n");
39	fprintf(stderr, "    andor:offset:val1:val2 - AND \"val1\" then OR \"val2\" at \"offset\"\n");
40	exit(1);
41}
42
43#define MAX_MODIFICATIONS 256
44struct modification {
45	enum { MOD_XOR, MOD_AND_OR } what;
46	unsigned long long offset;
47	u_int8_t m1, m2;
48};
49
50static void
51parse_modification(const char *s, struct modification *m)
52{
53	char what[16+1];
54	int n, m1, m2;
55
56	bzero(m, sizeof(*m));
57	if ((n = sscanf(s, "%16[^:]%*[:]%llu%*[:]%i%*[:]%i",
58	    what, &m->offset, &m1, &m2)) < 3)
59		errx(1, "Invalid modification spec \"%s\"", s);
60	if (strcasecmp(what, "xor") == 0) {
61		if (n > 3)
62			errx(1, "Invalid modification spec \"%s\"", s);
63		if (m1 < 0 || m1 > 0xff)
64			errx(1, "Invalid XOR modification value");
65		m->what = MOD_XOR;
66		m->m1 = m1;
67	} else if (strcasecmp(what, "andor") == 0) {
68		if (n != 4)
69			errx(1, "Invalid modification spec \"%s\"", s);
70		if (m1 < 0 || m1 > 0xff)
71			errx(1, "Invalid AND modification value");
72		if (m2 < 0 || m2 > 0xff)
73			errx(1, "Invalid OR modification value");
74		m->what = MOD_AND_OR;
75		m->m1 = m1;
76		m->m2 = m2;
77	} else
78		errx(1, "Invalid modification type \"%s\"", what);
79}
80
81int
82main(int argc, char **argv)
83{
84	int ch;
85	u_char buf[8192];
86	size_t total;
87	ssize_t r, s, o;
88	struct modification mods[MAX_MODIFICATIONS];
89	u_int i, wflag = 0, num_mods = 0;
90
91	while ((ch = getopt(argc, argv, "wm:")) != -1) {
92		switch (ch) {
93		case 'm':
94			if (num_mods >= MAX_MODIFICATIONS)
95				errx(1, "Too many modifications");
96			parse_modification(optarg, &(mods[num_mods++]));
97			break;
98		case 'w':
99			wflag = 1;
100			break;
101		default:
102			usage();
103			/* NOTREACHED */
104		}
105	}
106	for (total = 0;;) {
107		r = s = read(STDIN_FILENO, buf, sizeof(buf));
108		if (r == 0)
109			break;
110		if (r < 0) {
111			if (errno == EAGAIN || errno == EINTR)
112				continue;
113			err(1, "read");
114		}
115		for (i = 0; i < num_mods; i++) {
116			if (mods[i].offset < total ||
117			    mods[i].offset >= total + s)
118				continue;
119			switch (mods[i].what) {
120			case MOD_XOR:
121				buf[mods[i].offset - total] ^= mods[i].m1;
122				break;
123			case MOD_AND_OR:
124				buf[mods[i].offset - total] &= mods[i].m1;
125				buf[mods[i].offset - total] |= mods[i].m2;
126				break;
127			}
128		}
129		for (o = 0; o < s; o += r) {
130			r = write(STDOUT_FILENO, buf, s - o);
131			if (r == 0)
132				break;
133			if (r < 0) {
134				if (errno == EAGAIN || errno == EINTR)
135					continue;
136				err(1, "write");
137			}
138		}
139		total += s;
140	}
141	/* Warn if modifications not reached in input stream */
142	r = 0;
143	for (i = 0; wflag && i < num_mods; i++) {
144		if (mods[i].offset < total)
145			continue;
146		r = 1;
147		fprintf(stderr, "modpipe: warning - mod %u not reached\n", i);
148	}
149	return r;
150}
151