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/****************************************************************************
* bfs *
* Copyright (C) 2019 Tavian Barnes <tavianator@tavianator.com> *
* *
* Permission to use, copy, modify, and/or distribute this software for any *
* purpose with or without fee is hereby granted. *
* *
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES *
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF *
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR *
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES *
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN *
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF *
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. *
****************************************************************************/
#include "posix1e.h"
#include "bftw.h"
#include "util.h"
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#if BFS_HAS_SYS_ACL
# include <sys/acl.h>
#endif
#if BFS_HAS_POSIX1E_CAPABILITIES
# include <sys/capability.h>
#endif
#if BFS_HAS_SYS_ACL || BFS_HAS_POSIX1E_CAPABILITIES
static const char *open_path(const struct BFTW *ftwbuf, int *fd) {
#ifdef O_PATH
// The POSIX.1e APIS predate the *at() family of functions. We'd still
// like to do something to avoid path re-traversals and limit races
// though. Ideally we could just do openat(..., O_PATH) (since we may
// not have read access) and pass that fd to something like cap_get_fd()
// but that will fail since fgetxattr() needs read access to the file.
// The workaround is to use O_PATH to open an fd and then pass
// /proc/self/fd/<fd> to cap_get_path(). Inspired by
// https://android.googlesource.com/platform/bionic/+/2825f10b7f61558c264231a536cf3affc0d84204
int flags = O_PATH;
if (ftwbuf->stat_flags & BFS_STAT_NOFOLLOW) {
flags |= O_NOFOLLOW;
}
*fd = openat(ftwbuf->at_fd, ftwbuf->at_path, flags);
if (*fd < 0) {
return NULL;
}
size_t size = strlen("/proc/self/fd/") + CHAR_BIT*sizeof(int) + 1;
char *path = malloc(size);
if (!path) {
close(*fd);
*fd = -1;
return NULL;
}
snprintf(path, size, "/proc/self/fd/%d", *fd);
return path;
#else
*fd = -1;
return ftwbuf->path;
#endif
}
static void close_path(const struct BFTW *ftwbuf, const char *path, int fd) {
if (path && path != ftwbuf->path) {
free((void *)path);
}
if (fd >= 0) {
close(fd);
}
}
#endif // BFS_HAS_SYS_ACL || BFS_HAS_POSIX1E_CAPABILITIES
#if BFS_HAS_SYS_ACL
/** Check if any ACLs of the given type are non-trivial. */
static bool bfs_check_acl_type(const char *path, acl_type_t type) {
acl_t acl = acl_get_file(path, type);
if (!acl) {
return false;
}
bool ret = false;
acl_entry_t entry;
for (int status = acl_get_entry(acl, ACL_FIRST_ENTRY, &entry);
status > 0;
status = acl_get_entry(acl, ACL_NEXT_ENTRY, &entry)) {
#if defined(ACL_USER_OBJ) && defined(ACL_GROUP_OBJ) && defined(ACL_OTHER)
acl_tag_t tag;
if (acl_get_tag_type(entry, &tag) != 0) {
continue;
}
if (tag != ACL_USER_OBJ && tag != ACL_GROUP_OBJ && tag != ACL_OTHER) {
ret = true;
break;
}
#else
ret = true;
break;
#endif
}
acl_free(acl);
return ret;
}
bool bfs_check_acl(const struct BFTW *ftwbuf) {
if (ftwbuf->typeflag == BFTW_LNK) {
return false;
}
int fd;
const char *path = open_path(ftwbuf, &fd);
if (!path) {
return false;
}
bool ret = false;
if (bfs_check_acl_type(path, ACL_TYPE_ACCESS)) {
ret = true;
} else if (bfs_check_acl_type(path, ACL_TYPE_DEFAULT)) {
ret = true;
#ifdef ACL_TYPE_EXTENDED
} else if (bfs_check_acl_type(path, ACL_TYPE_EXTENDED)) {
ret = true;
#endif
}
close_path(ftwbuf, path, fd);
return ret;
}
#else // !BFS_HAS_SYS_ACL
bool bfs_check_acl(const struct BFTW *ftwbuf) {
return false;
}
#endif
#if BFS_HAS_POSIX1E_CAPABILITIES
bool bfs_check_capabilities(const struct BFTW *ftwbuf) {
bool ret = false;
if (ftwbuf->typeflag == BFTW_LNK) {
goto out;
}
int fd;
const char *path = open_path(ftwbuf, &fd);
if (!path) {
goto out;
}
cap_t caps = cap_get_file(path);
if (!caps) {
goto out_close;
}
// TODO: Any better way to check for a non-empty capability set?
char *text = cap_to_text(caps, NULL);
if (!text) {
goto out_free_caps;
}
ret = text[0];
cap_free(text);
out_free_caps:
cap_free(caps);
out_close:
close_path(ftwbuf, path, fd);
out:
return ret;
}
#else // !BFS_HAS_POSIX1E_CAPABILITIES
bool bfs_check_capabilities(const struct BFTW *ftwbuf) {
return false;
}
#endif
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