60 lines
2.5 KiB
C++
60 lines
2.5 KiB
C++
/*
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* Copyright (C) 2015 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <fcntl.h>
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#include <unistd.h>
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#include <errno.h>
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extern "C" int __faccessat(int, const char*, int);
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int faccessat(int dirfd, const char* pathname, int mode, int flags) {
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// "The mode specifies the accessibility check(s) to be performed,
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// and is either the value F_OK, or a mask consisting of the
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// bitwise OR of one or more of R_OK, W_OK, and X_OK."
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if ((mode != F_OK) && ((mode & ~(R_OK | W_OK | X_OK)) != 0) &&
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((mode & (R_OK | W_OK | X_OK)) == 0)) {
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errno = EINVAL;
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return -1;
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}
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if (flags != 0) {
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// We deliberately don't support AT_SYMLINK_NOFOLLOW, a glibc
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// only feature which is error prone and dangerous.
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// More details at http://permalink.gmane.org/gmane.linux.lib.musl.general/6952
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//
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// AT_EACCESS isn't supported either. Android doesn't have setuid
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// programs, and never runs code with euid!=uid.
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//
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// We could use faccessat2(2) from Linux 5.8, but since we don't want the
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// first feature and don't need the second, we just reject such requests.
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errno = EINVAL;
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return -1;
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}
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return __faccessat(dirfd, pathname, mode);
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}
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