[asterisk-bugs] [Zaptel 0011471]: [patch] unsafe use of strncpy

[noreply at bugs.digium.com]

A NOTE has been added to this issue. 
====================================================================== 
http://bugs.digium.com/view.php?id=11471 
====================================================================== 
Reported By:                flefoll
Assigned To:                
====================================================================== 
Project:                    Zaptel
Issue ID:                   11471
Category:                   General
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     new
Zaptel Version:              SVN 
SVN Branch (only for SVN checkouts, not tarball releases):  1.4  
SVN Revision (number only!): 3317 
Disclaimer on File?:        N/A 
Request Review:              
====================================================================== 
Date Submitted:             12-05-2007 03:15 CST
Last Modified:              12-07-2007 02:07 CST
====================================================================== 
Summary:                    [patch] unsafe use of strncpy
Description: 
strncpy(dst, src, len) makes a copy of src towards dst, limited to len
characters, but does NOT guarantee a final null character. So if you want
to obtain a "traditional" null-terminated string, extra work is required.

Zaptel uses strncpy in many places, but most often does not do this extra
work, while destination initial contents is undetermined (stack, ...).

I suggest to use snprintf() instead of strncpy(), since snprintf does
guarantee a final null character. Constraint : snprintf requires including
stdio.h, while strncpy requires including strings.h.

See additional information for the list of files that use strncpy.

I will upload patches for a number of them (not all at the moment).

The same work should be done on SVN Trunk, but it did not compile
yesterday for me (Fedora 7)
====================================================================== 

---------------------------------------------------------------------- 
 flefoll - 12-07-07 02:07  
---------------------------------------------------------------------- 
My first idea was to define a static inline function indeed : I considered
adding a static inline zap_strncpy() in zaptel.h, but 3 things made me
prefer using snprintf (or combining strncpy() and dst[n-1]=0 in header
files) :
- includes problems
  . size_t is unknown when compiling zonedata.c
    (can be fixed by either changing includes or using "unsigned int"
instead)
  . not all C files include zaptel.h
    (can also be fixes by changing includes, of course)
- snprintf() replaces strncpy() PLUS strncat() in zaptel-base.c, and
strncat() use was buggy as well :-)
- snprintf() is already used in zaptel

However, I understand that zap_strncpy() or zap_copy_string() or whatever
may be prefered. Whatever solution will guarantee null-terminated strings
and avoid buffer overflows will be good. 

Issue History 
Date Modified   Username       Field                    Change               
====================================================================== 
12-07-07 02:07  flefoll        Note Added: 0075009                          
======================================================================