modpipe.c revision 262566 
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#include "openbsd-compat/getopt_long.c"
29
30static void err(int, const char *, ...) __attribute__((format(printf, 2, 3)));
31static void errx(int, const char *, ...) __attribute__((format(printf, 2, 3)));
32
33static void
34err(int r, const char *fmt, ...)
35{
36	va_list args;
37
38	va_start(args, fmt);
39	fprintf(stderr, "%s: ", strerror(errno));
40	vfprintf(stderr, fmt, args);
41	fputc('\n', stderr);
42	va_end(args);
43	exit(r);
44}
45
46static void
47errx(int r, const char *fmt, ...)
48{
49	va_list args;
50
51	va_start(args, fmt);
52	vfprintf(stderr, fmt, args);
53	fputc('\n', stderr);
54	va_end(args);
55	exit(r);
56}
57
58static void
59usage(void)
60{
61	fprintf(stderr, "Usage: modpipe -w [-m modspec ...] < in > out\n");
62	fprintf(stderr, "modspec is one of:\n");
63	fprintf(stderr, "    xor:offset:value       - XOR \"value\" at \"offset\"\n");
64	fprintf(stderr, "    andor:offset:val1:val2 - AND \"val1\" then OR \"val2\" at \"offset\"\n");
65	exit(1);
66}
67
68#define MAX_MODIFICATIONS 256
69struct modification {
70	enum { MOD_XOR, MOD_AND_OR } what;
71	unsigned long long offset;
72	u_int8_t m1, m2;
73};
74
75static void
76parse_modification(const char *s, struct modification *m)
77{
78	char what[16+1];
79	int n, m1, m2;
80
81	bzero(m, sizeof(*m));
82	if ((n = sscanf(s, "%16[^:]%*[:]%llu%*[:]%i%*[:]%i",
83	    what, &m->offset, &m1, &m2)) < 3)
84		errx(1, "Invalid modification spec \"%s\"", s);
85	if (strcasecmp(what, "xor") == 0) {
86		if (n > 3)
87			errx(1, "Invalid modification spec \"%s\"", s);
88		if (m1 < 0 || m1 > 0xff)
89			errx(1, "Invalid XOR modification value");
90		m->what = MOD_XOR;
91		m->m1 = m1;
92	} else if (strcasecmp(what, "andor") == 0) {
93		if (n != 4)
94			errx(1, "Invalid modification spec \"%s\"", s);
95		if (m1 < 0 || m1 > 0xff)
96			errx(1, "Invalid AND modification value");
97		if (m2 < 0 || m2 > 0xff)
98			errx(1, "Invalid OR modification value");
99		m->what = MOD_AND_OR;
100		m->m1 = m1;
101		m->m2 = m2;
102	} else
103		errx(1, "Invalid modification type \"%s\"", what);
104}
105
106int
107main(int argc, char **argv)
108{
109	int ch;
110	u_char buf[8192];
111	size_t total;
112	ssize_t r, s, o;
113	struct modification mods[MAX_MODIFICATIONS];
114	u_int i, wflag = 0, num_mods = 0;
115
116	while ((ch = getopt(argc, argv, "wm:")) != -1) {
117		switch (ch) {
118		case 'm':
119			if (num_mods >= MAX_MODIFICATIONS)
120				errx(1, "Too many modifications");
121			parse_modification(optarg, &(mods[num_mods++]));
122			break;
123		case 'w':
124			wflag = 1;
125			break;
126		default:
127			usage();
128			/* NOTREACHED */
129		}
130	}
131	for (total = 0;;) {
132		r = s = read(STDIN_FILENO, buf, sizeof(buf));
133		if (r == 0)
134			break;
135		if (r < 0) {
136			if (errno == EAGAIN || errno == EINTR)
137				continue;
138			err(1, "read");
139		}
140		for (i = 0; i < num_mods; i++) {
141			if (mods[i].offset < total ||
142			    mods[i].offset >= total + s)
143				continue;
144			switch (mods[i].what) {
145			case MOD_XOR:
146				buf[mods[i].offset - total] ^= mods[i].m1;
147				break;
148			case MOD_AND_OR:
149				buf[mods[i].offset - total] &= mods[i].m1;
150				buf[mods[i].offset - total] |= mods[i].m2;
151				break;
152			}
153		}
154		for (o = 0; o < s; o += r) {
155			r = write(STDOUT_FILENO, buf, s - o);
156			if (r == 0)
157				break;
158			if (r < 0) {
159				if (errno == EAGAIN || errno == EINTR)
160					continue;
161				err(1, "write");
162			}
163		}
164		total += s;
165	}
166	/* Warn if modifications not reached in input stream */
167	r = 0;
168	for (i = 0; wflag && i < num_mods; i++) {
169		if (mods[i].offset < total)
170			continue;
171		r = 1;
172		fprintf(stderr, "modpipe: warning - mod %u not reached\n", i);
173	}
174	return r;
175}
176