alpine 3.6
access weakness #195


Weakness Breakdown


An access weakness occurs when software does not properly implement permissions that could have unintended consequences if exploited by malicious actors. An example of this weakness is when a default username and password are set by the developer but do not get changed by the system administrator.

Warning code(s):

Ensure that umask is given most restrictive possible setting.

File Name:



The highlighted line of code below is the trigger point of this particular Alpine 3.6 access weakness.


    rc = write_fh(fh, out);

    if (fh != NULL && tmpfilename != NULL) {
	/* tmpfilename != NULL indicates that we did NOT write to stdout,
	   so we have to close the stream and do the rename dance */

	if (rc == 0)  {
	    // renaming is only done if write_fh was successful
	    struct stat stat_buf;

	    /* in case we have an existing file, copy its mode... This
	       WILL NOT take care of any ACLs that may be set. Go
	       figure. */
	    if (stat(outfilename, &stat_buf) != 0) {
#ifdef WIN32
                stat_buf.st_mode = _S_IREAD | _S_IWRITE;  // have to test it is 
		/* an error occurred (file not found, maybe?). Anyway:
		   set the mode to 0666 using current umask */
		stat_buf.st_mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH;
		mode_t mask = umask(0);

		stat_buf.st_mode &= ~mask;
	    if (chmod(tmpfilename, stat_buf.st_mode) != 0) {
		rrd_set_error("Cannot chmod temporary file!");
		goto done;

	    // before we rename the file to the target file: forget all cached changes....
	    if (rrdc_is_any_connected()) {
		// is it a good idea to just ignore the error ????
#ifdef WIN32
/* in windows, renaming to an existing file is verboten */
	    if (rename(tmpfilename, outfilename) != 0) {
		rrd_set_error("Cannot rename temporary file to final file!");
		goto done;

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