Re: [PATCH] Fix segfault in pptpctrl argument parser

Thanks, pushed as d7b9552.

"git format-patch" style of mail is also welcome, and will save me a
few minutes.  ;-)

On Fri, Jul 08, 2016 at 12:58:07AM +0200, Christoph Biedl wrote:
> Hello,
> 
> it's easily possible to trigger a segfault in pptpctrl:
> 
> # /usr/sbin/pptpctrl 0 0 1 /etc/ppp/pptpd-options 0 1
> 
> This happened when triggering a bug in pptpmanager I am currently
> working on. The check for (argc < 7) isn't sufficient, my suggested
> fix adds a check to any GETARG_* invocation.
> 
>     Christoph
> 
> --- a/pptpctrl.c
> +++ b/pptpctrl.c
> @@ -92,19 +92,29 @@ static void launch_pppd(char **pppaddrs, struct in_addr *inetaddrs);
>  #define OUR_NB_MODE O_NDELAY
>  #endif
>  
> +void usage()
> +{
> +        fprintf(stderr, "pptpctrl: insufficient arguments, see man pptpctrl\n");
> +        exit(2);
> +}
> +
>  /* read a command line argument, a flag alone */
>  #define GETARG_INT(X) \
> +        if (arg >= argc) usage() ; \
>          X = atoi(argv[arg++])
>  
>  /* read a command line argument, a string alone */
>  #define GETARG_STRING(X) \
> +        if (arg >= argc) usage() ; \
>          X = strdup(argv[arg++])
>  
>  /* read a command line argument, a presence flag followed by string */
>  #define GETARG_VALUE(X) \
> -        if(atoi(argv[arg++]) != 0) \
> +        if (arg >= argc) usage() ; \
> +        if(atoi(argv[arg++]) != 0) { \
> +                if (arg >= argc) usage() ; \
>                  strlcpy(X, argv[arg++], sizeof(X)); \
> -        else \
> +        } else \
>                  *X = '\0'
>  
>  int main(int argc, char **argv)
> @@ -122,10 +132,8 @@ int main(int argc, char **argv)
>          gargv = argv;
>  
>          /* fail if argument count invalid */
> -        if (argc < 7) {
> -                fprintf(stderr, "pptpctrl: insufficient arguments, see man pptpctrl\n");
> -                exit(2);
> -        }
> +        if (argc < 7)
> +                usage();
>  
>          /* open a connection to the syslog daemon */
>          openlog("pptpd", LOG_PID, PPTP_FACILITY);
> 
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-- 
James Cameron
http://quozl.netrek.org/

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