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

[noreply at bugs.digium.com]

A NOTE has been added to this issue. 
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http://bugs.digium.com/view.php?id=11471 
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Reported By:                flefoll
Assigned To:                
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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:              
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Date Submitted:             12-05-2007 03:15 CST
Last Modified:              12-07-2007 08:20 CST
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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)
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---------------------------------------------------------------------- 
 Corydon76 - 12-07-07 08:20  
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The main problem I have with snprintf is that it is significantly slower
than ast_copy_string.  That matters a great deal, especially in places like
kernel modules.

In fact, it is even possible to see a slight speedup with ast_copy_string
over strncpy, because ast_copy_string only copies as many bytes as
necessary, whereas strncpy fills the remaining buffer with 0's. 

Issue History 
Date Modified   Username       Field                    Change               
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12-07-07 08:20  Corydon76      Note Added: 0075018                          
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