systemd/0002-basic-fs-util-add-a-version-of-chmod_and_chown-that-.patch

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From 6cb356ca9fe063846cfb883ef484f7e7e411096c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
Date: Tue, 3 Mar 2020 11:51:50 +0100
Subject: [PATCH 2/3] basic/fs-util: add a version of chmod_and_chown that
doesn not use /proc
---
src/basic/fs-util.c | 46 +++++++++++++++++++++++++++++++++++++++++
src/basic/fs-util.h | 1 +
src/test/test-fs-util.c | 45 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 92 insertions(+)
diff --git a/src/basic/fs-util.c b/src/basic/fs-util.c
index f8095e85d8..558cafbcaf 100644
--- a/src/basic/fs-util.c
+++ b/src/basic/fs-util.c
@@ -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;
diff --git a/src/basic/fs-util.h b/src/basic/fs-util.h
index 78d68be9fd..6b9ade2ec1 100644
--- a/src/basic/fs-util.h
+++ b/src/basic/fs-util.h
@@ -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);
diff --git a/src/test/test-fs-util.c b/src/test/test-fs-util.c
index d0c6fb82bf..d97ccfda3b 100644
--- a/src/test/test-fs-util.c
+++ b/src/test/test-fs-util.c
@@ -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;
}