Re: [PATCH 06/10] lockd: Add helper to sanity check incoming NOTIFY requests

["J. Bruce Fields" <bfields@fieldses.org>]

On Wed, Oct 01, 2008 at 12:01:30PM -0400, Chuck Lever wrote:
> On Sep 26, 2008, at Sep 26, 2008, 6:43 PM, J. Bruce Fields wrote:
>> On Wed, Sep 17, 2008 at 11:17:57AM -0500, Chuck Lever wrote:
>>> The NLM performs a silly test to see that incoming NOTIFY requests  
>>> are
>>> relatively secure.  Make sure the test works for both AF_INET and  
>>> AF_INET6
>>> addresses.
>>
>> Makes sense.  (Why's the test silly?  If it prevents local users from
>> telling lockd to drop a client's locks, that seems good.)
>
> I was referring to the port range part of the test.  Anyone who wants  
> real security will not rely on the port value, but will use SSL or  
> third-party authentication like Kerberos.

Over the loopback interface?

This is a local call--if the kernel needs kerberos to decide whether a
local process is privileged, something's wrong.

--b.

>
>>
>>
>> --b.
>>
>>>
>>> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
>>> ---
>>>
>>> fs/lockd/svc4proc.c         |    6 ++----
>>> fs/lockd/svcproc.c          |    6 ++----
>>> include/linux/lockd/lockd.h |   41 +++++++++++++++++++++++++++++++++ 
>>> ++++++++
>>> 3 files changed, 45 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/fs/lockd/svc4proc.c b/fs/lockd/svc4proc.c
>>> index 9e1c751..6a5ef9f 100644
>>> --- a/fs/lockd/svc4proc.c
>>> +++ b/fs/lockd/svc4proc.c
>>> @@ -432,11 +432,9 @@ nlm4svc_proc_sm_notify(struct svc_rqst *rqstp,  
>>> struct nlm_reboot *argp,
>>> {
>>> 	struct sockaddr_in	saddr;
>>>
>>> -	memcpy(&saddr, svc_addr_in(rqstp), sizeof(saddr));
>>> -
>>> 	dprintk("lockd: SM_NOTIFY     called\n");
>>> -	if (saddr.sin_addr.s_addr != htonl(INADDR_LOOPBACK)
>>> -	 || ntohs(saddr.sin_port) >= 1024) {
>>> +
>>> +	if (!nlm_privileged_requester(rqstp)) {
>>> 		char buf[RPC_MAX_ADDRBUFLEN];
>>> 		printk(KERN_WARNING "lockd: rejected NSM callback from %s\n",
>>> 				svc_print_addr(rqstp, buf, sizeof(buf)));
>>> diff --git a/fs/lockd/svcproc.c b/fs/lockd/svcproc.c
>>> index fcb7998..62fcfdb 100644
>>> --- a/fs/lockd/svcproc.c
>>> +++ b/fs/lockd/svcproc.c
>>> @@ -464,11 +464,9 @@ nlmsvc_proc_sm_notify(struct svc_rqst *rqstp,  
>>> struct nlm_reboot *argp,
>>> {
>>> 	struct sockaddr_in	saddr;
>>>
>>> -	memcpy(&saddr, svc_addr_in(rqstp), sizeof(saddr));
>>> -
>>> 	dprintk("lockd: SM_NOTIFY     called\n");
>>> -	if (saddr.sin_addr.s_addr != htonl(INADDR_LOOPBACK)
>>> -	 || ntohs(saddr.sin_port) >= 1024) {
>>> +
>>> +	if (!nlm_privileged_requester(rqstp)) {
>>> 		char buf[RPC_MAX_ADDRBUFLEN];
>>> 		printk(KERN_WARNING "lockd: rejected NSM callback from %s\n",
>>> 				svc_print_addr(rqstp, buf, sizeof(buf)));
>>> diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/ 
>>> lockd.h
>>> index 075095f..409eab4 100644
>>> --- a/include/linux/lockd/lockd.h
>>> +++ b/include/linux/lockd/lockd.h
>>> @@ -280,6 +280,47 @@ static inline struct inode  
>>> *nlmsvc_file_inode(struct nlm_file *file)
>>> 	return file->f_file->f_path.dentry->d_inode;
>>> }
>>>
>>> +static inline int __nlm_privileged_request4(const struct sockaddr  
>>> *sap)
>>> +{
>>> +	const struct sockaddr_in *sin = (struct sockaddr_in *)sap;
>>> +	return (sin->sin_addr.s_addr == htonl(INADDR_LOOPBACK)) &&
>>> +			(ntohs(sin->sin_port) < 1024);
>>> +}
>>> +
>>> +#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
>>> +static inline int __nlm_privileged_request6(const struct sockaddr  
>>> *sap)
>>> +{
>>> +	const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sap;
>>> +	return (ipv6_addr_type(&sin6->sin6_addr) & IPV6_ADDR_LOOPBACK) &&
>>> +			(ntohs(sin6->sin6_port) < 1024);
>>> +}
>>> +#else	/* defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) */
>>> +static inline int __nlm_privileged_request6(const struct sockaddr  
>>> *sap)
>>> +{
>>> +	return 0;
>>> +}
>>> +#endif	/* defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) */
>>> +
>>> +/*
>>> + * Ensure incoming requests are suitably "secure"
>>> + *
>>> + * Return TRUE if sender is local and is connecting via a  
>>> privileged port;
>>> + * otherwise return FALSE.
>>> + */
>>> +static inline int nlm_privileged_requester(const struct svc_rqst  
>>> *rqstp)
>>> +{
>>> +	const struct sockaddr *sap = svc_addr(rqstp);
>>> +
>>> +	switch (sap->sa_family) {
>>> +	case AF_INET:
>>> +		return __nlm_privileged_request4(sap);
>>> +	case AF_INET6:
>>> +		return __nlm_privileged_request6(sap);
>>> +	default:
>>> +		return 0;
>>> +	}
>>> +}
>>> +
>>> static inline int __nlm_cmp_addr4(const struct sockaddr *sap1,
>>> 				  const struct sockaddr *sap2)
>>> {
>>>
>> --
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>
> -- 
> Chuck Lever
> chuck[dot]lever[at]oracle[dot]com
>
>
>
>