Merge pull request #15002 from keszybz/sysusers-no-proc

Make systemd-sysusers work if /proc is unavailable

4 files changed, 111 insertions, 13 deletions

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/sysusers/sysusers.c b/src/sysusers/sysusers.c
index 2771fd959f..f7cc7e0900 100644
--- a/src/sysusers/sysusers.c
+++ b/src/sysusers/sysusers.c
@@ -94,6 +94,12 @@ STATIC_DESTRUCTOR_REGISTER(database_groups, set_free_freep);
 STATIC_DESTRUCTOR_REGISTER(uid_range, freep);
 STATIC_DESTRUCTOR_REGISTER(arg_root, freep);
 
+static int errno_is_not_exists(int code) {
+        /* See getpwnam(3) and getgrnam(3): those codes and others can be returned if the user or group are
+         * not found. */
+        return IN_SET(code, 0, ENOENT, ESRCH, EBADF, EPERM);
+}
+
 static int load_user_database(void) {
         _cleanup_fclose_ FILE *f = NULL;
         const char *passwd_path;
@@ -193,7 +199,7 @@ static int load_group_database(void) {
 static int make_backup(const char *target, const char *x) {
         _cleanup_close_ int src = -1;
         _cleanup_fclose_ FILE *dst = NULL;
-        _cleanup_free_ char *temp = NULL;
+        _cleanup_free_ char *dst_tmp = NULL;
         char *backup;
         struct timespec ts[2];
         struct stat st;
@@ -210,7 +216,7 @@ static int make_backup(const char *target, const char *x) {
         if (fstat(src, &st) < 0)
                 return -errno;
 
-        r = fopen_temporary_label(target, x, &dst, &temp);
+        r = fopen_temporary_label(target, x, &dst, &dst_tmp);
         if (r < 0)
                 return r;
 
@@ -224,7 +230,7 @@ static int make_backup(const char *target, const char *x) {
         backup = strjoina(x, "-");
 
         /* Copy over the access mask */
-        r = fchmod_and_chown(fileno(dst), st.st_mode & 07777, st.st_uid, st.st_gid);
+        r = chmod_and_chown_unsafe(dst_tmp, st.st_mode & 07777, st.st_uid, st.st_gid);
         if (r < 0)
                 log_warning_errno(r, "Failed to change access mode or ownership of %s: %m", backup);
 
@@ -237,7 +243,7 @@ static int make_backup(const char *target, const char *x) {
         if (r < 0)
                 goto fail;
 
-        if (rename(temp, backup) < 0) {
+        if (rename(dst_tmp, backup) < 0) {
                 r = -errno;
                 goto fail;
         }
@@ -245,7 +251,7 @@ static int make_backup(const char *target, const char *x) {
         return 0;
 
 fail:
-        (void) unlink(temp);
+        (void) unlink(dst_tmp);
         return r;
 }
 
@@ -339,13 +345,13 @@ static int putsgent_with_members(const struct sgrp *sg, FILE *gshadow) {
 }
 #endif
 
-static int sync_rights(FILE *from, FILE *to) {
+static int sync_rights(FILE *from, const char *to) {
         struct stat st;
 
         if (fstat(fileno(from), &st) < 0)
                 return -errno;
 
-        return fchmod_and_chown(fileno(to), st.st_mode & 07777, st.st_uid, st.st_gid);
+        return chmod_and_chown_unsafe(to, st.st_mode & 07777, st.st_uid, st.st_gid);
 }
 
 static int rename_and_apply_smack(const char *temp_path, const char *dest_path) {
@@ -383,7 +389,7 @@ static int write_temporary_passwd(const char *passwd_path, FILE **tmpfile, char
         original = fopen(passwd_path, "re");
         if (original) {
 
-                r = sync_rights(original, passwd);
+                r = sync_rights(original, passwd_tmp);
                 if (r < 0)
                         return r;
 
@@ -485,7 +491,7 @@ static int write_temporary_shadow(const char *shadow_path, FILE **tmpfile, char
         original = fopen(shadow_path, "re");
         if (original) {
 
-                r = sync_rights(original, shadow);
+                r = sync_rights(original, shadow_tmp);
                 if (r < 0)
                         return r;
 
@@ -582,7 +588,7 @@ static int write_temporary_group(const char *group_path, FILE **tmpfile, char **
         original = fopen(group_path, "re");
         if (original) {
 
-                r = sync_rights(original, group);
+                r = sync_rights(original, group_tmp);
                 if (r < 0)
                         return r;
 
@@ -681,7 +687,7 @@ static int write_temporary_gshadow(const char * gshadow_path, FILE **tmpfile, ch
         if (original) {
                 struct sgrp *sg;
 
-                r = sync_rights(original, gshadow);
+                r = sync_rights(original, gshadow_tmp);
                 if (r < 0)
                         return r;
 
@@ -971,7 +977,7 @@ static int add_user(Item *i) {
 
                         return 0;
                 }
-                if (!IN_SET(errno, 0, ENOENT))
+                if (!errno_is_not_exists(errno))
                         return log_error_errno(errno, "Failed to check if user %s already exists: %m", i->name);
         }
 
@@ -1108,7 +1114,7 @@ static int get_gid_by_name(const char *name, gid_t *gid) {
                         *gid = g->gr_gid;
                         return 0;
                 }
-                if (!IN_SET(errno, 0, ENOENT))
+                if (!errno_is_not_exists(errno))
                         return log_error_errno(errno, "Failed to check if group %s already exists: %m", name);
         }
 
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;
 }