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 <sys/types.h>
20 #include <unistd.h>
21 #include <stdio.h>
22 #include <string.h>
23 #include <stdlib.h>
24 #include <err.h>
25 #include <errno.h>
26
27 static void
usage(void)28 usage(void)
29 {
30 fprintf(stderr, "Usage: modpipe -w [-m modspec ...] < in > out\n");
31 fprintf(stderr, "modspec is one of:\n");
32 fprintf(stderr, " xor:offset:value - XOR \"value\" at \"offset\"\n");
33 fprintf(stderr, " andor:offset:val1:val2 - AND \"val1\" then OR \"val2\" at \"offset\"\n");
34 exit(1);
35 }
36
37 #define MAX_MODIFICATIONS 256
38 struct modification {
39 enum { MOD_XOR, MOD_AND_OR } what;
40 unsigned long long offset;
41 u_int8_t m1, m2;
42 };
43
44 static void
parse_modification(const char * s,struct modification * m)45 parse_modification(const char *s, struct modification *m)
46 {
47 char what[16+1];
48 int n, m1, m2;
49
50 bzero(m, sizeof(*m));
51 if ((n = sscanf(s, "%16[^:]%*[:]%llu%*[:]%i%*[:]%i",
52 what, &m->offset, &m1, &m2)) < 3)
53 errx(1, "Invalid modification spec \"%s\"", s);
54 if (strcasecmp(what, "xor") == 0) {
55 if (n > 3)
56 errx(1, "Invalid modification spec \"%s\"", s);
57 if (m1 < 0 || m1 > 0xff)
58 errx(1, "Invalid XOR modification value");
59 m->what = MOD_XOR;
60 m->m1 = m1;
61 } else if (strcasecmp(what, "andor") == 0) {
62 if (n != 4)
63 errx(1, "Invalid modification spec \"%s\"", s);
64 if (m1 < 0 || m1 > 0xff)
65 errx(1, "Invalid AND modification value");
66 if (m2 < 0 || m2 > 0xff)
67 errx(1, "Invalid OR modification value");
68 m->what = MOD_AND_OR;
69 m->m1 = m1;
70 m->m2 = m2;
71 } else
72 errx(1, "Invalid modification type \"%s\"", what);
73 }
74
75 int
main(int argc,char ** argv)76 main(int argc, char **argv)
77 {
78 int ch;
79 u_char buf[8192];
80 size_t total;
81 ssize_t r, s, o;
82 struct modification mods[MAX_MODIFICATIONS];
83 u_int i, wflag = 0, num_mods = 0;
84
85 while ((ch = getopt(argc, argv, "wm:")) != -1) {
86 switch (ch) {
87 case 'm':
88 if (num_mods >= MAX_MODIFICATIONS)
89 errx(1, "Too many modifications");
90 parse_modification(optarg, &(mods[num_mods++]));
91 break;
92 case 'w':
93 wflag = 1;
94 break;
95 default:
96 usage();
97 /* NOTREACHED */
98 }
99 }
100 for (total = 0;;) {
101 r = s = read(STDIN_FILENO, buf, sizeof(buf));
102 if (r == 0)
103 break;
104 if (r < 0) {
105 if (errno == EAGAIN || errno == EINTR)
106 continue;
107 err(1, "read");
108 }
109 for (i = 0; i < num_mods; i++) {
110 if (mods[i].offset < total ||
111 mods[i].offset >= total + s)
112 continue;
113 switch (mods[i].what) {
114 case MOD_XOR:
115 buf[mods[i].offset - total] ^= mods[i].m1;
116 break;
117 case MOD_AND_OR:
118 buf[mods[i].offset - total] &= mods[i].m1;
119 buf[mods[i].offset - total] |= mods[i].m2;
120 break;
121 }
122 }
123 for (o = 0; o < s; o += r) {
124 r = write(STDOUT_FILENO, buf, s - o);
125 if (r == 0)
126 break;
127 if (r < 0) {
128 if (errno == EAGAIN || errno == EINTR)
129 continue;
130 err(1, "write");
131 }
132 }
133 total += s;
134 }
135 /* Warn if modifications not reached in input stream */
136 r = 0;
137 for (i = 0; wflag && i < num_mods; i++) {
138 if (mods[i].offset < total)
139 continue;
140 r = 1;
141 fprintf(stderr, "modpipe: warning - mod %u not reached\n", i);
142 }
143 return r;
144 }
145