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

[Walter Harms]

> 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()

> +    (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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