1/*	$NetBSD: expandm.c,v 1.12 2019/01/24 22:07:14 mrg Exp $	*/
2
3/*-
4 * Copyright (c) 2019 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Christos Zoulas.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31#include <sys/cdefs.h>
32__RCSID("$NetBSD: expandm.c,v 1.12 2019/01/24 22:07:14 mrg Exp $");
33
34#include <limits.h>
35#include <stdio.h>
36#include <string.h>
37#include <stdlib.h>
38#include <errno.h>
39
40#include "expandm.h"
41
42#ifdef TEST
43#undef INT_MAX
44#define INT_MAX 31
45#endif
46
47
48const char * __attribute__((__format_arg__(1)))
49expandm(const char *fmt, const char *sf, char **rbuf)
50{
51	const int err = errno;
52	const char *e = NULL;
53	char *buf, *m, *nbuf;
54	const char *ptr;
55
56	buf = NULL;
57	for (ptr = fmt; (m = strstr(ptr, "%m")) != NULL; ptr = m + 2) {
58		size_t cnt = 0;
59		size_t nlen;
60
61		for (char *p = m; p >= ptr && *p == '%'; p--)
62			cnt++;
63
64		nlen = (size_t)(m - ptr);
65		/*
66		 * we can't exceed INT_MAX because int is used as
67		 * a format width
68		 */
69		if (__predict_false(nlen >= INT_MAX)) {
70			size_t blen = buf ? strlen(buf) : 0;
71			size_t tlen;
72
73			/*
74			 * if we would overflow a ptrdiff_t when computing
75			 * tlen, then don't bother.  The format string is
76			 * simply too large to be converted.
77			 */
78			if (blen >= PTRDIFF_MAX ||
79			    nlen >= PTRDIFF_MAX - blen ||
80			    nlen >= SIZE_T_MAX - blen)
81				goto out;
82
83			tlen = nlen + blen;
84
85			nbuf = realloc(buf, tlen + 1);
86			if (nbuf == NULL)
87				goto out;
88
89			memcpy(nbuf + blen, ptr, nlen);
90			nbuf[tlen] = '\0';
91			ptr += nlen;
92			buf = nbuf;
93		}
94
95		if (__predict_true(e == NULL && (cnt & 1) != 0))
96			e = strerror(err);
97		if (asprintf(&nbuf, "%s%.*s%s", buf ? buf : "",
98		    (int)(m - ptr), ptr, (cnt & 1) ? e : "%m") == -1)
99			goto out;
100		free(buf);
101		buf = nbuf;
102	}
103
104	if (asprintf(&nbuf, "%s%s%s", buf ? buf : "", ptr, sf ? sf : "") == -1)
105		goto out;
106
107	free(buf);
108	if (rbuf)
109		*rbuf = nbuf;
110	errno = err;
111	return nbuf;
112out:
113	free(buf);
114	if (rbuf)
115		*rbuf = NULL;
116	errno = err;
117	return fmt;
118}
119
120#ifdef TEST
121int
122main(int argc, char *argv[])
123{
124	errno = ERANGE;
125	printf("%s\n", expandm(argc > 1 ? argv[1] : "Message %%m=%m: %%%m%%",
126	    "...", NULL));
127	return 0;
128}
129#endif
130