Make local kms server proxy file creation atomic with renameHEADmaster

1 files changed, 9 insertions, 4 deletions

diff --git a/main.c b/main.c
index bc1f589..8084021 100644
--- a/main.c
+++ b/main.c
@@ -80,10 +80,12 @@ static int create_local_kms_server_proxy_directory(const char *home) {
     return 1;
 }
 
-static int create_local_kms_server_proxy_file(const char *source_path, const char *dest_path) {
+static int create_local_kms_server_proxy_file_atomic(const char *source_path, const char *dest_path) {
     int in_fd = -1;
     int out_fd = -1;
     int res = 0;
+    char tmp_filepath[PATH_MAX];
+    snprintf(tmp_filepath, sizeof(tmp_filepath), "%s.tmp", dest_path);
 
     in_fd = open(source_path, O_RDONLY);
     if(in_fd == -1)
@@ -93,7 +95,7 @@ static int create_local_kms_server_proxy_file(const char *source_path, const cha
     if(fstat(in_fd, &st) == -1)
         goto done;
 
-    out_fd = open(dest_path, O_RDWR | O_CREAT | O_TRUNC, 0755);
+    out_fd = open(tmp_filepath, O_RDWR | O_CREAT | O_TRUNC, 0755);
     if(out_fd == -1)
         goto done;
 
@@ -109,7 +111,10 @@ static int create_local_kms_server_proxy_file(const char *source_path, const cha
         close(out_fd);
 
     if(res)
-        res = file_set_sys_admin_capability(dest_path, 1);
+        res = file_set_sys_admin_capability(tmp_filepath, 1);
+
+    if(res)
+        rename(tmp_filepath, dest_path);
 
     return res;
 }
@@ -165,7 +170,7 @@ int main(int argc, char **argv) {
         return execvp(args[0], (char *const*)args);
     } else if(geteuid() == 0) { /* is current user root */
         file_set_sys_admin_capability(gsr_kms_server_filepath, 0);
-        create_local_kms_server_proxy_file(self_path, kms_server_proxy_local_filepath);
+        create_local_kms_server_proxy_file_atomic(self_path, kms_server_proxy_local_filepath);
 
         const char *args[] = { gsr_kms_server_filepath, initial_socket_path, card_path, NULL };
         return execv(args[0], (char *const*)args);