svn commit: r349890 - head/contrib/telnet/telnet

[Shawn Webb]

On Wed, Jul 10, 2019 at 05:42:04PM +0000, Philip Paeps wrote:
> Author: philip
> Date: Wed Jul 10 17:42:04 2019
> New Revision: 349890
> URL: https://svnweb.freebsd.org/changeset/base/349890
> 
> Log:
>   telnet: fix a couple of snprintf() buffer overflows
>   
>   Obtained from:	Juniper Networks
>   MFC after:	1 week
> 
> Modified:
>   head/contrib/telnet/telnet/commands.c
>   head/contrib/telnet/telnet/telnet.c
>   head/contrib/telnet/telnet/utilities.c
> 
> Modified: head/contrib/telnet/telnet/commands.c
> ==============================================================================
> --- head/contrib/telnet/telnet/commands.c	Wed Jul 10 17:21:59 2019	(r349889)
> +++ head/contrib/telnet/telnet/commands.c	Wed Jul 10 17:42:04 2019	(r349890)
> @@ -1655,10 +1655,11 @@ env_init(void)
>  		char hbuf[256+1];
>  		char *cp2 = strchr((char *)ep->value, ':');
>  
> -		gethostname(hbuf, 256);
> -		hbuf[256] = '\0';
> -		cp = (char *)malloc(strlen(hbuf) + strlen(cp2) + 1);
> -		sprintf((char *)cp, "%s%s", hbuf, cp2);
> +		gethostname(hbuf, sizeof(hbuf));
> +		hbuf[sizeof(hbuf)-1] = '\0';
> +                unsigned int buflen = strlen(hbuf) + strlen(cp2) + 1;

buflen should be defined with the rest of the variables in the code
block above this one.

> +		cp = (char *)malloc(sizeof(char)*buflen);

Lack of NULL check here leads to

> +		snprintf((char *)cp, buflen, "%s%s", hbuf, cp2);

potential NULL pointer deref here.

Thanks,

-- 
Shawn Webb
Cofounder / Security Engineer
HardenedBSD

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