Re: [PATCH 1/2] Avoid reverse resolution for server name

[Steve Dickson <SteveD@redhat.com>]

On 02/04/13 15:32, Simo Sorce wrote:
> A NFS client should be able to work properly even if the DNS Reverse record
> for the server is not set. There is no excuse to forcefully prevent that
> from working when it can.
> 
> This patch adds a new pair of options (-z/-Z) that allow to turn on/off
> DNS reverse resolution for determining the server name to use with GSSAPI.
Again, please tell me why we need the -Z flag when that is the default?

steved.
> 
> To avoid breaking current behavior the option defaults to off by default,
> ideally we will turn this on by default after a transition period.
> 
> Signed-off-by: Simo Sorce <simo@redhat.com>
> ---
>  utils/gssd/gss_util.h  |    2 ++
>  utils/gssd/gssd.c      |   10 ++++++++--
>  utils/gssd/gssd_proc.c |   25 +++++++++++++++++++++----
>  3 files changed, 31 insertions(+), 6 deletions(-)
> 
> diff --git a/utils/gssd/gss_util.h b/utils/gssd/gss_util.h
> index aa9f77806075f9ab67a7763a75a010369ba2d1b9..663fb0998bede6144118f890b9311ee8687176e3 100644
> --- a/utils/gssd/gss_util.h
> +++ b/utils/gssd/gss_util.h
> @@ -52,4 +52,6 @@ int gssd_check_mechs(void);
>  		gss_krb5_set_allowable_enctypes(min, cred, num, types)
>  #endif
>  
> +extern int avoid_ptr;
> +
>  #endif /* _GSS_UTIL_H_ */
> diff --git a/utils/gssd/gssd.c b/utils/gssd/gssd.c
> index 07b1e52e6b84e9bcba96e7a63b0505ca7823482a..1f0ac0c47667c42ed03e271cb18b6124165e5d5f 100644
> --- a/utils/gssd/gssd.c
> +++ b/utils/gssd/gssd.c
> @@ -85,7 +85,7 @@ sig_hup(int signal)
>  static void
>  usage(char *progname)
>  {
> -	fprintf(stderr, "usage: %s [-f] [-l] [-M] [-n] [-v] [-r] [-p pipefsdir] [-k keytab] [-d ccachedir] [-t timeout] [-R preferred realm]\n",
> +	fprintf(stderr, "usage: %s [-f] [-l] [-M] [-n] [-v] [-r] [-p pipefsdir] [-k keytab] [-d ccachedir] [-t timeout] [-R preferred realm] [-z] [-Z]\n",
>  		progname);
>  	exit(1);
>  }
> @@ -102,7 +102,7 @@ main(int argc, char *argv[])
>  	char *progname;
>  
>  	memset(ccachesearch, 0, sizeof(ccachesearch));
> -	while ((opt = getopt(argc, argv, "fvrlmnMp:k:d:t:R:")) != -1) {
> +	while ((opt = getopt(argc, argv, "fvrlmnMp:k:d:t:R:zZ")) != -1) {
>  		switch (opt) {
>  			case 'f':
>  				fg = 1;
> @@ -150,6 +150,12 @@ main(int argc, char *argv[])
>  				errx(1, "Encryption type limits not supported by Kerberos libraries.");
>  #endif
>  				break;
> +			case 'z':
> +				avoid_ptr = 1;
> +				break;
> +			case 'Z':
> +				avoid_ptr = 0;
> +				break;
>  			default:
>  				usage(argv[0]);
>  				break;
> diff --git a/utils/gssd/gssd_proc.c b/utils/gssd/gssd_proc.c
> index ea01e92e4565670b97dea1a936d2f0dbdc7c4610..21d4e1d78eb54d177626cb0a19b9de4e93e0a20d 100644
> --- a/utils/gssd/gssd_proc.c
> +++ b/utils/gssd/gssd_proc.c
> @@ -67,6 +67,7 @@
>  #include <errno.h>
>  #include <gssapi/gssapi.h>
>  #include <netdb.h>
> +#include <ctype.h>
>  
>  #include "gssd.h"
>  #include "err_util.h"
> @@ -107,6 +108,8 @@ struct pollfd * pollarray;
>  
>  unsigned long pollsize;  /* the size of pollaray (in pollfd's) */
>  
> +int avoid_ptr = 0;
> +
>  /*
>   * convert a presentation address string to a sockaddr_storage struct. Returns
>   * true on success or false on failure.
> @@ -165,12 +168,26 @@ addrstr_to_sockaddr(struct sockaddr *sa, const char *node, const char *port)
>   * convert a sockaddr to a hostname
>   */
>  static char *
> -sockaddr_to_hostname(const struct sockaddr *sa, const char *addr)
> +get_servername(const char *name, const struct sockaddr *sa, const char *addr)
>  {
>  	socklen_t		addrlen;
>  	int			err;
>  	char			*hostname;
>  	char			hbuf[NI_MAXHOST];
> +	unsigned char		buf[sizeof(struct in6_addr)];
> +	int			do_ptr_lookup = 0;
> +
> +	if (avoid_ptr) {
> +		/* try to determine if this is a name, or an IP address.
> +		 * If it is an IP fallback to a PTR lookup */
> +		if (strchr(name, '.') && inet_pton(AF_INET, name, buf) == 1)
> +			do_ptr_lookup = 1; /* IPv4 */
> +		else if (strchr(name, ':') && inet_pton(AF_INET6, name, buf) == 1)
> +			do_ptr_lookup = 1; /* or IPv6 */
> +		if (!do_ptr_lookup) {
> +			return strdup(name);
> +		}
> +	}
>  
>  	switch (sa->sa_family) {
>  	case AF_INET:
> @@ -208,7 +225,7 @@ read_service_info(char *info_file_name, char **servicename, char **servername,
>  		  struct sockaddr *addr) {
>  #define INFOBUFLEN 256
>  	char		buf[INFOBUFLEN + 1];
> -	static char	dummy[128];
> +	static char	server[128];
>  	int		nbytes;
>  	static char	service[128];
>  	static char	address[128];
> @@ -236,7 +253,7 @@ read_service_info(char *info_file_name, char **servicename, char **servername,
>  		   "service: %127s %15s version %15s\n"
>  		   "address: %127s\n"
>  		   "protocol: %15s\n",
> -		   dummy,
> +		   server,
>  		   service, program, version,
>  		   address,
>  		   protoname);
> @@ -258,7 +275,7 @@ read_service_info(char *info_file_name, char **servicename, char **servername,
>  	if (!addrstr_to_sockaddr(addr, address, port))
>  		goto fail;
>  
> -	*servername = sockaddr_to_hostname(addr, address);
> +	*servername = get_servername(server, addr, address);
>  	if (*servername == NULL)
>  		goto fail;
>  
>