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// Copyright © Tavian Barnes <tavianator@tavianator.com>
// SPDX-License-Identifier: 0BSD
#include "fsade.h"
#include "config.h"
#include "bfstd.h"
#include "bftw.h"
#include "dir.h"
#include "dstring.h"
#include <errno.h>
#include <fcntl.h>
#include <stddef.h>
#include <unistd.h>
#if BFS_CAN_CHECK_ACL
# include <sys/acl.h>
#endif
#if BFS_CAN_CHECK_CAPABILITIES
# include <sys/capability.h>
#endif
#if BFS_USE_SYS_EXTATTR_H
# include <sys/extattr.h>
#elif BFS_USE_SYS_XATTR_H
# include <sys/xattr.h>
#endif
#if BFS_CAN_CHECK_ACL || BFS_CAN_CHECK_CAPABILITIES || BFS_CAN_CHECK_XATTRS
/**
* Many of the APIs used here don't have *at() variants, but we can try to
* emulate something similar if /proc/self/fd is available.
*/
static const char *fake_at(const struct BFTW *ftwbuf) {
static bool proc_works = true;
static bool proc_checked = false;
char *path = NULL;
if (!proc_works || ftwbuf->at_fd == AT_FDCWD) {
goto fail;
}
path = dstrprintf("/proc/self/fd/%d/", ftwbuf->at_fd);
if (!path) {
goto fail;
}
if (!proc_checked) {
proc_checked = true;
if (xfaccessat(AT_FDCWD, path, F_OK) != 0) {
proc_works = false;
goto fail;
}
}
if (dstrcat(&path, ftwbuf->at_path) != 0) {
goto fail;
}
return path;
fail:
dstrfree(path);
return ftwbuf->path;
}
static void free_fake_at(const struct BFTW *ftwbuf, const char *path) {
if (path != ftwbuf->path) {
dstrfree((char *)path);
}
}
/**
* Check if an error was caused by the absence of support or data for a feature.
*/
static bool is_absence_error(int error) {
// If the OS doesn't support the feature, it's obviously not enabled for
// any files
if (error == ENOTSUP) {
return true;
}
// On Linux, ACLs and capabilities are implemented in terms of extended
// attributes, which report ENODATA/ENOATTR when missing
#ifdef ENODATA
if (error == ENODATA) {
return true;
}
#endif
#if defined(ENOATTR) && ENOATTR != ENODATA
if (error == ENOATTR) {
return true;
}
#endif
// On at least FreeBSD and macOS, EINVAL is returned when the requested
// ACL type is not supported for that file
if (error == EINVAL) {
return true;
}
#if __APPLE__
// On macOS, ENOENT can also signal that a file has no ACLs
if (error == ENOENT) {
return true;
}
#endif
return false;
}
#endif // BFS_CAN_CHECK_ACL || BFS_CAN_CHECK_CAPABILITIES || BFS_CAN_CHECK_XATTRS
#if BFS_CAN_CHECK_ACL
/** Check if a POSIX.1e ACL is non-trivial. */
static int bfs_check_posix1e_acl(acl_t acl, bool ignore_required) {
int ret = 0;
acl_entry_t entry;
for (int status = acl_get_entry(acl, ACL_FIRST_ENTRY, &entry);
#if __APPLE__
// POSIX.1e specifies a return value of 1 for success, but macOS
// returns 0 instead
status == 0;
#else
status > 0;
#endif
status = acl_get_entry(acl, ACL_NEXT_ENTRY, &entry)) {
#if defined(ACL_USER_OBJ) && defined(ACL_GROUP_OBJ) && defined(ACL_OTHER)
if (ignore_required) {
acl_tag_t tag;
if (acl_get_tag_type(entry, &tag) != 0) {
ret = -1;
continue;
}
if (tag == ACL_USER_OBJ || tag == ACL_GROUP_OBJ || tag == ACL_OTHER) {
continue;
}
}
#endif
ret = 1;
break;
}
return ret;
}
/** Check if an ACL of the given type is non-trivial. */
static int bfs_check_acl_type(acl_t acl, acl_type_t type) {
if (type == ACL_TYPE_DEFAULT) {
// For directory default ACLs, any entries make them non-trivial
return bfs_check_posix1e_acl(acl, false);
}
#if __FreeBSD__
int trivial;
#if __has_feature(memory_sanitizer)
// msan seems to be missing an interceptor for acl_is_trivial_np()
trivial = 0;
#endif
if (acl_is_trivial_np(acl, &trivial) < 0) {
return -1;
} else if (trivial) {
return 0;
} else {
return 1;
}
#else // !__FreeBSD__
return bfs_check_posix1e_acl(acl, true);
#endif
}
int bfs_check_acl(const struct BFTW *ftwbuf) {
static const acl_type_t acl_types[] = {
#if __APPLE__
// macOS gives EINVAL for either of the two standard ACL types,
// supporting only ACL_TYPE_EXTENDED
ACL_TYPE_EXTENDED,
#else
// The two standard POSIX.1e ACL types
ACL_TYPE_ACCESS,
ACL_TYPE_DEFAULT,
#endif
#ifdef ACL_TYPE_NFS4
ACL_TYPE_NFS4,
#endif
};
if (ftwbuf->type == BFS_LNK) {
return 0;
}
const char *path = fake_at(ftwbuf);
int ret = -1, error = 0;
for (size_t i = 0; i < BFS_COUNTOF(acl_types) && ret <= 0; ++i) {
acl_type_t type = acl_types[i];
if (type == ACL_TYPE_DEFAULT && ftwbuf->type != BFS_DIR) {
// ACL_TYPE_DEFAULT is supported only for directories,
// otherwise acl_get_file() gives EACCESS
continue;
}
acl_t acl = acl_get_file(path, type);
if (!acl) {
error = errno;
if (is_absence_error(error)) {
ret = 0;
}
continue;
}
ret = bfs_check_acl_type(acl, type);
error = errno;
acl_free(acl);
}
free_fake_at(ftwbuf, path);
errno = error;
return ret;
}
#else // !BFS_CAN_CHECK_ACL
int bfs_check_acl(const struct BFTW *ftwbuf) {
errno = ENOTSUP;
return -1;
}
#endif
#if BFS_CAN_CHECK_CAPABILITIES
int bfs_check_capabilities(const struct BFTW *ftwbuf) {
if (ftwbuf->type == BFS_LNK) {
return 0;
}
int ret = -1, error;
const char *path = fake_at(ftwbuf);
cap_t caps = cap_get_file(path);
if (!caps) {
error = errno;
if (is_absence_error(error)) {
ret = 0;
}
goto out_path;
}
// TODO: Any better way to check for a non-empty capability set?
char *text = cap_to_text(caps, NULL);
if (!text) {
error = errno;
goto out_caps;
}
ret = text[0] ? 1 : 0;
error = errno;
cap_free(text);
out_caps:
cap_free(caps);
out_path:
free_fake_at(ftwbuf, path);
errno = error;
return ret;
}
#else // !BFS_CAN_CHECK_CAPABILITIES
int bfs_check_capabilities(const struct BFTW *ftwbuf) {
errno = ENOTSUP;
return -1;
}
#endif
#if BFS_CAN_CHECK_XATTRS
int bfs_check_xattrs(const struct BFTW *ftwbuf) {
const char *path = fake_at(ftwbuf);
ssize_t len;
#if BFS_USE_SYS_EXTATTR_H
ssize_t (*extattr_list)(const char *, int, void*, size_t) =
ftwbuf->type == BFS_LNK ? extattr_list_link : extattr_list_file;
len = extattr_list(path, EXTATTR_NAMESPACE_SYSTEM, NULL, 0);
if (len <= 0) {
len = extattr_list(path, EXTATTR_NAMESPACE_USER, NULL, 0);
}
#elif __APPLE__
int options = ftwbuf->type == BFS_LNK ? XATTR_NOFOLLOW : 0;
len = listxattr(path, NULL, 0, options);
#else
if (ftwbuf->type == BFS_LNK) {
len = llistxattr(path, NULL, 0);
} else {
len = listxattr(path, NULL, 0);
}
#endif
int error = errno;
free_fake_at(ftwbuf, path);
if (len > 0) {
return 1;
} else if (len == 0 || is_absence_error(error)) {
return 0;
} else if (
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