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/* $OpenBSD: realpath.c,v 1.22 2017/12/24 01:50:50 millert Exp $ */
/*
* Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The names of the authors may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
/* A slightly modified copy of this file exists in libexec/ld.so */
/*
* char *realpath(const char *path, char resolved[PATH_MAX]);
*
* Find the real name of path, by removing all ".", ".." and symlink
* components. Returns (resolved) on success, or (NULL) on failure,
* in which case the path which caused trouble is left in (resolved).
*/
char *
realpath(const char *path, char *resolved)
{
const char *p;
char *q;
size_t left_len, resolved_len, next_token_len;
unsigned symlinks;
int serrno, mem_allocated;
ssize_t slen;
char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
if (path == NULL) {
errno = EINVAL;
return (NULL);
}
if (path[0] == '\0') {
errno = ENOENT;
return (NULL);
}
serrno = errno;
if (resolved == NULL) {
resolved = malloc(PATH_MAX);
if (resolved == NULL)
return (NULL);
mem_allocated = 1;
} else
mem_allocated = 0;
symlinks = 0;
if (path[0] == '/') {
resolved[0] = '/';
resolved[1] = '\0';
if (path[1] == '\0')
return (resolved);
resolved_len = 1;
left_len = strlcpy(left, path + 1, sizeof(left));
} else {
if (getcwd(resolved, PATH_MAX) == NULL) {
if (mem_allocated)
free(resolved);
else
strlcpy(resolved, ".", PATH_MAX);
return (NULL);
}
resolved_len = strlen(resolved);
left_len = strlcpy(left, path, sizeof(left));
}
if (left_len >= sizeof(left)) {
errno = ENAMETOOLONG;
goto err;
}
/*
* Iterate over path components in `left'.
*/
while (left_len != 0) {
/*
* Extract the next path component and adjust `left'
* and its length.
*/
p = strchr(left, '/');
next_token_len = p ? (size_t) (p - left) : left_len;
memcpy(next_token, left, next_token_len);
next_token[next_token_len] = '\0';
if (p != NULL) {
left_len -= next_token_len + 1;
memmove(left, p + 1, left_len + 1);
} else {
left[0] = '\0';
left_len = 0;
}
if (resolved[resolved_len - 1] != '/') {
if (resolved_len + 1 >= PATH_MAX) {
errno = ENAMETOOLONG;
goto err;
}
resolved[resolved_len++] = '/';
resolved[resolved_len] = '\0';
}
if (next_token[0] == '\0')
continue;
else if (strcmp(next_token, ".") == 0)
continue;
else if (strcmp(next_token, "..") == 0) {
/*
* Strip the last path component except when we have
* single "/"
*/
if (resolved_len > 1) {
resolved[resolved_len - 1] = '\0';
q = strrchr(resolved, '/') + 1;
*q = '\0';
resolved_len = q - resolved;
}
continue;
}
/*
* Append the next path component and readlink() it. If
* readlink() fails we still can return successfully if
* it exists but isn't a symlink, or if there are no more
* path components left.
*/
resolved_len = strlcat(resolved, next_token, PATH_MAX);
if (resolved_len >= PATH_MAX) {
errno = ENAMETOOLONG;
goto err;
}
slen = readlink(resolved, symlink, sizeof(symlink));
if (slen < 0) {
switch (errno) {
case EINVAL:
/* not a symlink, continue to next component */
continue;
case ENOENT:
if (p == NULL) {
errno = serrno;
return (resolved);
}
/* FALLTHROUGH */
default:
goto err;
}
} else if (slen == 0) {
errno = EINVAL;
goto err;
} else if (slen == sizeof(symlink)) {
errno = ENAMETOOLONG;
goto err;
} else {
if (symlinks++ > SYMLOOP_MAX) {
errno = ELOOP;
goto err;
}
symlink[slen] = '\0';
if (symlink[0] == '/') {
resolved[1] = 0;
resolved_len = 1;
} else {
/* Strip the last path component. */
q = strrchr(resolved, '/') + 1;
*q = '\0';
resolved_len = q - resolved;
}
/*
* If there are any path components left, then
* append them to symlink. The result is placed
* in `left'.
*/
if (p != NULL) {
if (symlink[slen - 1] != '/') {
if (slen + 1 >= sizeof(symlink)) {
errno = ENAMETOOLONG;
goto err;
}
symlink[slen] = '/';
symlink[slen + 1] = 0;
}
left_len = strlcat(symlink, left, sizeof(symlink));
if (left_len >= sizeof(symlink)) {
errno = ENAMETOOLONG;
goto err;
}
}
left_len = strlcpy(left, symlink, sizeof(left));
}
}
/*
* Remove trailing slash except when the resolved pathname
* is a single "/".
*/
if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
resolved[resolved_len - 1] = '\0';
return (resolved);
err:
if (mem_allocated)
free(resolved);
return (NULL);
}
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