8c39a1e837
1. Conform to IEEE Std 1003.1-2004, which state that "Constructed arguments cannot grow larger than 255 bytes", and 2. Avoid a buffer overflow. Unfortunately the standard doesn't indicate how xargs is supposed to handle arguments which (with the appropriate substitutions) would grow larger than 255 bytes; this solution handles those by making as many substitutions as possible without overflowing the buffer. OpenBSD's xargs resolves this in a different direction, by making all the substitutions and then silently truncating the resulting string. Since this change may break existing scripts which rely upon the buffer overflow (255 bytes isn't really all that long...) it will not be MFCed.
98 lines
2.2 KiB
C
98 lines
2.2 KiB
C
/* $xMach: strnsubst.c,v 1.3 2002/02/23 02:10:24 jmallett Exp $ */
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/*
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* Copyright (c) 2002 J. Mallett. All rights reserved.
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* You may do whatever you want with this file as long as
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* the above copyright and this notice remain intact, along
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* with the following statement:
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* For the man who taught me vi, and who got too old, too young.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <err.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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void strnsubst(char **, const char *, const char *, size_t);
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/*
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* Replaces str with a string consisting of str with match replaced with
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* replstr as many times as can be done before the constructed string is
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* maxsize bytes large. It does not free the string pointed to by str, it
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* is up to the calling program to be sure that the original contents of
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* str as well as the new contents are handled in an appropriate manner.
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* If replstr is NULL, then that internally is changed to a nil-string, so
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* that we can still pretend to do somewhat meaningful substitution.
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* No value is returned.
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*/
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void
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strnsubst(char **str, const char *match, const char *replstr, size_t maxsize)
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{
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char *s1, *s2, *this;
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s1 = *str;
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if (s1 == NULL)
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return;
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s2 = calloc(maxsize, 1);
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if (s2 == NULL)
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err(1, "calloc");
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if (replstr == NULL)
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replstr = "";
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if (match == NULL || replstr == NULL || maxsize == strlen(s1)) {
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strlcpy(s2, s1, maxsize);
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goto done;
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}
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for (;;) {
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this = strstr(s1, match);
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if (this == NULL)
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break;
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if ((strlen(s2) + strlen(s1) + strlen(replstr) -
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strlen(match) + 1) > maxsize) {
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strlcat(s2, s1, maxsize);
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goto done;
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}
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strncat(s2, s1, (uintptr_t)this - (uintptr_t)s1);
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strcat(s2, replstr);
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s1 = this + strlen(match);
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}
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strcat(s2, s1);
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done:
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*str = s2;
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return;
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}
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#ifdef TEST
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#include <stdio.h>
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int
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main(void)
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{
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char *x, *y, *z, *za;
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x = "{}%$";
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strnsubst(&x, "%$", "{} enpury!", 255);
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y = x;
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strnsubst(&y, "}{}", "ybir", 255);
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z = y;
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strnsubst(&z, "{", "v ", 255);
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za = z;
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strnsubst(&z, NULL, za, 255);
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if (strcmp(z, "v ybir enpury!") == 0)
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printf("strnsubst() seems to work!\n");
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else
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printf("strnsubst() is broken.\n");
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printf("%s\n", z);
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free(x);
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free(y);
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free(z);
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free(za);
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return 0;
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}
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#endif
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