Atomic copy_from in files promise

Changes to `files` promise in `copy_from` attribute:

- The new file (i.e., `<FILENAME>.cfnew`) is now created with correct
  permission during remote copy. Previously it would be created with
  default permissions.
- The destination file (`<FILENAME>`) is no longer deleted on backup
  during file copy.  Previously it would be renamed to
  `<FILENAME>.cfsaved`, causing the original file to dissappear. Now an
  actual copy of the original file with the same permissions is created
  instead.

As a result, there will no longer be a brief moment where the original
file is inaccessible.

Ticket: ENT-11988
Changelog: Commit
Signed-off-by: Lars Erik Wik <lars.erik.wik@northern.tech>

cf-agent/verify_files_utils.c

@@ -1552,7 +1552,7 @@ bool CopyRegularFile(EvalContext *ctx, const char *source, const char *dest, con
         }
 
         if (!CopyRegularFileNet(source, ToChangesPath(new),
-                                sstat->st_size, attr->copy.encrypt, conn))
+                                sstat->st_size, attr->copy.encrypt, conn, sstat->st_mode))
         {
             RecordFailure(ctx, pp, attr, "Failed to copy file '%s' from '%s'",
                           source, conn->remoteip);
@@ -1712,7 +1712,7 @@ bool CopyRegularFile(EvalContext *ctx, const char *source, const char *dest, con
                 }
             }
 
-            if (rename(dest, changes_backup) == 0)
+            if (FileCopyKeepPerms(dest, changes_backup))
             {
                 RecordChange(ctx, pp, attr, "Backed up '%s' as '%s'", dest, backup);
                 *result = PromiseResultUpdate(*result, PROMISE_RESULT_CHANGE);

libcfnet/client_code.c

@@ -750,7 +750,7 @@ static void FlushFileStream(int sd, int toget)
 /* TODO finalise socket or TLS session in all cases that this function fails
  * and the transaction protocol is out of sync. */
 bool CopyRegularFileNet(const char *source, const char *dest, off_t size,
-                        bool encrypt, AgentConnection *conn)
+                        bool encrypt, AgentConnection *conn, mode_t mode)
 {
     char *buf, workbuf[CF_BUFSIZE], cfchangedstr[265];
     const int buf_size = 2048;
@@ -774,7 +774,7 @@ bool CopyRegularFileNet(const char *source, const char *dest, off_t size,
 
     unlink(dest);                /* To avoid link attacks */
 
-    int dd = safe_open_create_perms(dest, O_WRONLY | O_CREAT | O_TRUNC | O_EXCL | O_BINARY, CF_PERMS_DEFAULT);
+    int dd = safe_open_create_perms(dest, O_WRONLY | O_CREAT | O_TRUNC | O_EXCL | O_BINARY, mode);
     if (dd == -1)
     {
         Log(LOG_LEVEL_ERR,

libcfnet/client_code.h

@@ -48,7 +48,7 @@ void DisconnectServer(AgentConnection *conn);
 
 bool CompareHashNet(const char *file1, const char *file2, bool encrypt, AgentConnection *conn);
 bool CopyRegularFileNet(const char *source, const char *dest, off_t size,
-                        bool encrypt, AgentConnection *conn);
+                        bool encrypt, AgentConnection *conn, mode_t mode);
 Item *RemoteDirList(const char *dirname, bool encrypt, AgentConnection *conn);
 
 int TLSConnectCallCollect(ConnectionInfo *conn_info, const char *username);