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basic/fs-util: add a version of chmod_and_chown that doesn not use /proc

This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2020-03-03 11:51:50 +01:00
parent 08c7c3216b
commit 6cb356ca9f
3 changed files with 92 additions and 0 deletions
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46
src/basic/fs-util.c
View File

@ -272,6 +272,52 @@ int fchmod_and_chown(int fd, mode_t mode, uid_t uid, gid_t gid) {
return do_chown || do_chmod;
}
int chmod_and_chown_unsafe(const char *path, mode_t mode, uid_t uid, gid_t gid) {
bool do_chown, do_chmod;
struct stat st;
assert(path);
/* Change ownership and access mode of the specified path, see description of fchmod_and_chown().
* Should only be used on trusted paths. */
if (lstat(path, &st) < 0)
return -errno;
do_chown =
(uid != UID_INVALID && st.st_uid != uid) ||
(gid != GID_INVALID && st.st_gid != gid);
do_chmod =
!S_ISLNK(st.st_mode) && /* chmod is not defined on symlinks */
((mode != MODE_INVALID && ((st.st_mode ^ mode) & 07777) != 0) ||
do_chown); /* If we change ownership, make sure we reset the mode afterwards, since chown()
* modifies the access mode too */
if (mode == MODE_INVALID)
mode = st.st_mode; /* If we only shall do a chown(), save original mode, since chown() might break it. */
else if ((mode & S_IFMT) != 0 && ((mode ^ st.st_mode) & S_IFMT) != 0)
return -EINVAL; /* insist on the right file type if it was specified */
if (do_chown && do_chmod) {
mode_t minimal = st.st_mode & mode; /* the subset of the old and the new mask */
if (((minimal ^ st.st_mode) & 07777) != 0)
if (chmod(path, minimal & 07777) < 0)
return -errno;
}
if (do_chown)
if (lchown(path, uid, gid) < 0)
return -errno;
if (do_chmod)
if (chmod(path, mode & 07777) < 0)
return -errno;
return do_chown || do_chmod;
}
int fchmod_umask(int fd, mode_t m) {
mode_t u;
int r;

1
src/basic/fs-util.h
View File

@ -34,6 +34,7 @@ int readlink_and_make_absolute(const char *p, char **r);
int chmod_and_chown(const char *path, mode_t mode, uid_t uid, gid_t gid);
int fchmod_and_chown(int fd, mode_t mode, uid_t uid, gid_t gid);
int chmod_and_chown_unsafe(const char *path, mode_t mode, uid_t uid, gid_t gid);
int fchmod_umask(int fd, mode_t mode);
int fchmod_opath(int fd, mode_t m);

45
src/test/test-fs-util.c
View File

@ -802,6 +802,50 @@ static void test_chmod_and_chown(void) {
assert_se(S_ISLNK(st.st_mode));
}
static void test_chmod_and_chown_unsafe(void) {
_cleanup_(rm_rf_physical_and_freep) char *d = NULL;
_unused_ _cleanup_umask_ mode_t u = umask(0000);
struct stat st;
const char *p;
if (geteuid() != 0)
return;
log_info("/* %s */", __func__);
assert_se(mkdtemp_malloc(NULL, &d) >= 0);
p = strjoina(d, "/reg");
assert_se(mknod(p, S_IFREG | 0123, 0) >= 0);
assert_se(chmod_and_chown_unsafe(p, S_IFREG | 0321, 1, 2) >= 0);
assert_se(chmod_and_chown_unsafe(p, S_IFDIR | 0555, 3, 4) == -EINVAL);
assert_se(lstat(p, &st) >= 0);
assert_se(S_ISREG(st.st_mode));
assert_se((st.st_mode & 07777) == 0321);
p = strjoina(d, "/dir");
assert_se(mkdir(p, 0123) >= 0);
assert_se(chmod_and_chown_unsafe(p, S_IFDIR | 0321, 1, 2) >= 0);
assert_se(chmod_and_chown_unsafe(p, S_IFREG | 0555, 3, 4) == -EINVAL);
assert_se(lstat(p, &st) >= 0);
assert_se(S_ISDIR(st.st_mode));
assert_se((st.st_mode & 07777) == 0321);
p = strjoina(d, "/lnk");
assert_se(symlink("idontexist", p) >= 0);
assert_se(chmod_and_chown_unsafe(p, S_IFLNK | 0321, 1, 2) >= 0);
assert_se(chmod_and_chown_unsafe(p, S_IFREG | 0555, 3, 4) == -EINVAL);
assert_se(chmod_and_chown_unsafe(p, S_IFDIR | 0555, 3, 4) == -EINVAL);
assert_se(lstat(p, &st) >= 0);
assert_se(S_ISLNK(st.st_mode));
}
int main(int argc, char *argv[]) {
test_setup_logging(LOG_INFO);
@ -819,6 +863,7 @@ int main(int argc, char *argv[]) {
test_fsync_directory_of_file();
test_rename_noreplace();
test_chmod_and_chown();
test_chmod_and_chown_unsafe();
return 0;
}