port write_env_file() to label_os_pre() + teach firstboot a bit of relabelling (#37869)

This is a clean-up, and also addresses some of the points of #37857.

src/basic/env-file.c

@@ -5,10 +5,12 @@
 #include "alloc-util.h"
 #include "env-file.h"
 #include "env-util.h"
+#include "errno-util.h"
 #include "escape.h"
 #include "fd-util.h"
 #include "fileio.h"
 #include "fs-util.h"
+#include "label.h"
 #include "log.h"
 #include "string-util.h"
 #include "strv.h"
@@ -629,7 +631,7 @@ static void write_env_var(FILE *f, const char *v) {
         fputc_unlocked('\n', f);
 }
 
-int write_env_file(int dir_fd, const char *fname, char **headers, char **l) {
+int write_env_file(int dir_fd, const char *fname, char **headers, char **l, WriteEnvFileFlags flags) {
         _cleanup_fclose_ FILE *f = NULL;
         _cleanup_free_ char *p = NULL;
         int r;
@@ -637,7 +639,18 @@ int write_env_file(int dir_fd, const char *fname, char **headers, char **l) {
         assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
         assert(fname);
 
+        bool call_label_ops_post = false;
+        if (FLAGS_SET(flags, WRITE_ENV_FILE_LABEL)) {
+                r = label_ops_pre(dir_fd, fname, S_IFREG);
+                if (r < 0)
+                        return r;
+
+                call_label_ops_post = true;
+        }
+
         r = fopen_tmpfile_linkable_at(dir_fd, fname, O_WRONLY|O_CLOEXEC, &p, &f);
+        if (call_label_ops_post)
+                RET_GATHER(r, label_ops_post(f ? fileno(f) : dir_fd, f ? NULL : fname, /* created= */ !!f));
         if (r < 0)
                 return r;
 
@@ -672,5 +685,5 @@ int write_vconsole_conf(int dir_fd, const char *fname, char **l) {
                 "# Written by systemd-localed(8) or systemd-firstboot(1), read by systemd-localed",
                 "# and systemd-vconsole-setup(8). Use localectl(1) to update this file.");
 
-        return write_env_file(dir_fd, fname, headers, l);
+        return write_env_file(dir_fd, fname, headers, l, WRITE_ENV_FILE_LABEL);
 }

src/basic/env-file.h

@@ -15,7 +15,11 @@ int load_env_file_pairs_fd(int fd, const char *fname, char ***ret);
 
 int merge_env_file(char ***env, FILE *f, const char *fname);
 
-int write_env_file(int dir_fd, const char *fname, char **headers, char **l);
+typedef enum WriteEnvFileFlags {
+        WRITE_ENV_FILE_LABEL = 1 << 0,
+} WriteEnvFileFlags;
+
+int write_env_file(int dir_fd, const char *fname, char **headers, char **l, WriteEnvFileFlags flags);
 
 int write_vconsole_conf(int dir_fd, const char *fname, char **l);
 

src/basic/fs-util.c

@@ -459,14 +459,14 @@ int symlinkat_idempotent(const char *from, int atfd, const char *to, bool make_r
         return 0;
 }
 
-int symlinkat_atomic_full(const char *from, int atfd, const char *to, bool make_relative) {
-        _cleanup_free_ char *relpath = NULL, *t = NULL;
+int symlinkat_atomic_full(const char *from, int atfd, const char *to, SymlinkFlags flags) {
         int r;
 
         assert(from);
         assert(to);
 
-        if (make_relative) {
+        _cleanup_free_ char *relpath = NULL;
+        if (FLAGS_SET(flags, SYMLINK_MAKE_RELATIVE)) {
                 r = path_make_relative_parent(to, from, &relpath);
                 if (r < 0)
                         return r;
@@ -474,12 +474,25 @@ int symlinkat_atomic_full(const char *from, int atfd, const char *to, bool make_
                 from = relpath;
         }
 
+        _cleanup_free_ char *t = NULL;
         r = tempfn_random(to, NULL, &t);
         if (r < 0)
                 return r;
 
-        if (symlinkat(from, atfd, t) < 0)
-                return -errno;
+        bool call_label_ops_post = false;
+        if (FLAGS_SET(flags, SYMLINK_LABEL)) {
+                r = label_ops_pre(atfd, to, S_IFLNK);
+                if (r < 0)
+                        return r;
+
+                call_label_ops_post = true;
+        }
+
+        r = RET_NERRNO(symlinkat(from, atfd, t));
+        if (call_label_ops_post)
+                RET_GATHER(r, label_ops_post(atfd, t, /* created= */ r >= 0));
+        if (r < 0)
+                return r;
 
         r = RET_NERRNO(renameat(atfd, t, atfd, to));
         if (r < 0) {

src/basic/fs-util.h

@@ -48,9 +48,14 @@ static inline int symlink_idempotent(const char *from, const char *to, bool make
         return symlinkat_idempotent(from, AT_FDCWD, to, make_relative);
 }
 
-int symlinkat_atomic_full(const char *from, int atfd, const char *to, bool make_relative);
+typedef enum SymlinkFlags {
+        SYMLINK_MAKE_RELATIVE = 1 << 0,
+        SYMLINK_LABEL         = 1 << 1,
+} SymlinkFlags;
+
+int symlinkat_atomic_full(const char *from, int atfd, const char *to, SymlinkFlags flags);
 static inline int symlink_atomic(const char *from, const char *to) {
-        return symlinkat_atomic_full(from, AT_FDCWD, to, false);
+        return symlinkat_atomic_full(from, AT_FDCWD, to, 0);
 }
 
 int mknodat_atomic(int atfd, const char *path, mode_t mode, dev_t dev);