[PATCH app/sessreg] Replace strncpy calls with a sane version that always terminates

[Peter Hutterer]

On Wed, Sep 12, 2018 at 09:09:22AM +0200, Walter Harms wrote:
> 
> 
> > Peter Hutterer <peter.hutterer at who-t.net> hat am 12. September 2018 um 06:50
> > geschrieben:
> > 
> > 
> > Fixes coverity complaints about potentially unterminated strings
> > 
> > Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> > ---
> >  sessreg.c | 26 +++++++++++++++++---------
> >  1 file changed, 17 insertions(+), 9 deletions(-)
> > 
> > diff --git a/sessreg.c b/sessreg.c
> > index 0a8fdb2..53b30b0 100644
> > --- a/sessreg.c
> > +++ b/sessreg.c
> > @@ -192,6 +192,14 @@ sysnerr (int x, const char *s)
> >  	return x;
> >  }
> >  
> > +static void
> > +safe_strncpy(char *dest, const char *src, size_t n)
> > +{
> 
> if you add
>      if (!src)
>           return;
> 
> you can also remove the if (x) before strncpy()

tbh, I'd rather touch this code as little as possible. there's more cleanup
possible but...

Cheers,
   Peter

> 
> > +    (void)strncpy(dest, src, n);
> > +    if (n > 0)
> > +        dest[n - 1] = '\0';
> > +}
> > +
> 
> 
> just my 2 cents
> 
> re,
>  wh
> 
> >  int
> >  main (int argc, char **argv)
> >  {
> > @@ -406,9 +414,9 @@ main (int argc, char **argv)
> >  			memset(&ll, 0, sizeof(ll));
> >  			ll.ll_time = current_time;
> >  			if (line)
> > -			 (void) strncpy (ll.ll_line, line, sizeof (ll.ll_line));
> > +			 safe_strncpy (ll.ll_line, line, sizeof (ll.ll_line));
> >  			if (host_name)
> > -			 (void) strncpy (ll.ll_host, host_name, sizeof (ll.ll_host));
> > +			 safe_strncpy (ll.ll_host, host_name, sizeof (ll.ll_host));
> >  
> >  			sysnerr (write (llog, (char *) &ll, sizeof (ll))
> >  					== sizeof (ll), "write lastlog entry");
> > @@ -429,11 +437,11 @@ set_utmp (struct utmp *u, char *line, char *user, char
> > *host, time_t date, int a
> >  {
> >  	memset (u, 0, sizeof (*u));
> >  	if (line)
> > -		(void) strncpy (u->ut_line, line, sizeof (u->ut_line));
> > +		safe_strncpy (u->ut_line, line, sizeof (u->ut_line));
> >  	else
> >  		memset (u->ut_line, 0, sizeof (u->ut_line));
> >  	if (addp && user)
> > -		(void) strncpy (u->ut_name, user, sizeof (u->ut_name));
> > +		safe_strncpy (u->ut_name, user, sizeof (u->ut_name));
> >  	else
> >  		memset (u->ut_name, 0, sizeof (u->ut_name));
> >  #ifdef HAVE_STRUCT_UTMP_UT_ID
> > @@ -451,7 +459,7 @@ set_utmp (struct utmp *u, char *line, char *user, char
> > *host, time_t date, int a
> >  			i -= sizeof (u->ut_id);
> >  		else
> >  			i = 0;
> > -		(void) strncpy (u->ut_id, line + i, sizeof (u->ut_id));
> > +		safe_strncpy (u->ut_id, line + i, sizeof (u->ut_id));
> >  	} else
> >  		memset (u->ut_id, 0, sizeof (u->ut_id));
> >  #endif
> > @@ -469,7 +477,7 @@ set_utmp (struct utmp *u, char *line, char *user, char
> > *host, time_t date, int a
> >  #endif
> >  #ifdef HAVE_STRUCT_UTMP_UT_HOST
> >  	if (addp && host)
> > -		(void) strncpy (u->ut_host, host, sizeof (u->ut_host));
> > +		safe_strncpy (u->ut_host, host, sizeof (u->ut_host));
> >  	else
> >  		memset (u->ut_host, 0, sizeof (u->ut_host));
> >  #endif
> > @@ -513,7 +521,7 @@ set_utmpx (struct utmpx *u, const char *line, const char
> > *user,
> >  		if(strcmp(line, ":0") == 0)
> >  			(void) strcpy(u->ut_line, "console");
> >  		else
> > -			(void) strncpy (u->ut_line, line, sizeof (u->ut_line));
> > +			safe_strncpy (u->ut_line, line, sizeof (u->ut_line));
> >  
> >  		strncpy(u->ut_host, line, sizeof(u->ut_host));
> >  #ifdef HAVE_STRUCT_UTMPX_UT_SYSLEN
> > @@ -523,7 +531,7 @@ set_utmpx (struct utmpx *u, const char *line, const char
> > *user,
> >  	else
> >  		memset (u->ut_line, 0, sizeof (u->ut_line));
> >  	if (addp && user)
> > -		(void) strncpy (u->ut_user, user, sizeof (u->ut_user));
> > +		safe_strncpy (u->ut_user, user, sizeof (u->ut_user));
> >  	else
> >  		memset (u->ut_user, 0, sizeof (u->ut_user));
> >  
> > @@ -541,7 +549,7 @@ set_utmpx (struct utmpx *u, const char *line, const char
> > *user,
> >  			i -= sizeof (u->ut_id);
> >  		else
> >  			i = 0;
> > -		(void) strncpy (u->ut_id, line + i, sizeof (u->ut_id));
> > +		safe_strncpy (u->ut_id, line + i, sizeof (u->ut_id));
> >  
> >  		/* make sure there is no entry using identical ut_id */
> >  		if (!UtmpxIdOpen(u->ut_id) && addp) {
> > -- 
> > 2.17.1
> > 
> > _______________________________________________
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