Re: [9fans] lpdaemon

[erik quanstrom <quanstro@quanstro.net>]

On Wed Jun  5 09:15:11 EDT 2013, don.bailey@gmail.com wrote:
> The first opportunity to write a nil byte should always be taken.
> Using sizeof only means that in corner cases memory disclosure may
> occur between where the nil should be and the end of the array.  While
> this isn't a security critical app, it is still good coding practice.
> 
> x = strlen(info.host) < sizeof info.host ? strlen() : sizeof ;
> info.host[x] = 0;

let's start at the beginning.  strncpy is not good coding practice.
and lpdaemon is not well written by today's standards.  ☺

however, unless i'm missing something, the code has exactly that.

/sys/src/cmd/lp/lpdaemon.c:297,310
		case 'H':
			if (ap[1] == '\0')
				strncpy(info.host, "unknown", NAMELEN);
			else
				strncpy(info.host, (const char *)&ap[1], NAMELEN);
			info.host[NAMELEN] = '\0';
			break;
		case 'P':
			if (ap[1] == '\0')
				strncpy(info.user, "unknown", NAMELEN);
			else
				strncpy(info.user, (const char *)&ap[1], NAMELEN);
			info.user[NAMELEN] = '\0';
			break;

- erik