Re: [PATCH nfs-utils] exportfs: make "insecure" the default for all exports

[Chuck Lever <chuck.lever@oracle.com>]

On 5/13/25 10:28 PM, NeilBrown wrote:
> On Wed, 14 May 2025, NeilBrown wrote:
>> On Tue, 13 May 2025, Jeff Layton wrote:
>>> Back in the 80's someone thought it was a good idea to carve out a set
>>> of ports that only privileged users could use. When NFS was originally
>>> conceived, Sun made its server require that clients use low ports.
>>> Since Linux was following suit with Sun in those days, exportfs has
>>> always defaulted to requiring connections from low ports.
>>>
>>> These days, anyone can be root on their laptop, so limiting connections
>>> to low source ports is of little value.
>>
>> But who is going to export any filesystem to their laptop?
>>
>>>
>>> Make the default be "insecure" when creating exports.
>>
>> So you want to break lots of configurations that are working perfectly
>> well?
> 
> Sorry - I was wrong.  You aren't breaking working configurations, but
> you are removing a protection that people might be expecting.  It might
> not be much protection, but it is not zero.

I beg to differ. It really is no protection at all in the modern era,
and it is actively inconvenient for deployments with desktop file
browsers or NAT routers.

As a community we should be encouraging secure deployments out of the
shrink wrap. Making cryptographic security easy should be (and is for
me) job number one. This export option is nothing more than theater.

I agree that a warning would be useful if neither "secure" nor
"insecure" is specified for an export.


>> I don't see any really motivation for this change.  Could you provide it
>> please?
> 
> Or to put it another way: who benefits?
> 
> Thanks,
> NeilBrown
> 
> 
>>
>> Thanks,
>> NeilBrown
>>
>>>
>>> Signed-off-by: Jeff Layton <jlayton@kernel.org>
>>> ---
>>> In discussion at the Bake-a-thon, we decided to just go for making
>>> "insecure" the default for all exports.
>>> ---
>>>  support/nfs/exports.c      | 7 +++++--
>>>  utils/exportfs/exports.man | 4 ++--
>>>  2 files changed, 7 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/support/nfs/exports.c b/support/nfs/exports.c
>>> index 21ec6486ba3d3945df0800972ba1dfd03bd65375..69f8ca8b5e2ed50b837ef287ca0685af3e70ed0b 100644
>>> --- a/support/nfs/exports.c
>>> +++ b/support/nfs/exports.c
>>> @@ -34,8 +34,11 @@
>>>  #include "reexport.h"
>>>  #include "nfsd_path.h"
>>>  
>>> -#define EXPORT_DEFAULT_FLAGS	\
>>> -  (NFSEXP_READONLY|NFSEXP_ROOTSQUASH|NFSEXP_GATHERED_WRITES|NFSEXP_NOSUBTREECHECK)
>>> +#define EXPORT_DEFAULT_FLAGS	(NFSEXP_READONLY |	\
>>> +				 NFSEXP_ROOTSQUASH |	\
>>> +				 NFSEXP_GATHERED_WRITES |\
>>> +				 NFSEXP_NOSUBTREECHECK | \
>>> +				 NFSEXP_INSECURE_PORT)
>>>  
>>>  struct flav_info flav_map[] = {
>>>  	{ "krb5",	RPC_AUTH_GSS_KRB5,	1},
>>> diff --git a/utils/exportfs/exports.man b/utils/exportfs/exports.man
>>> index 39dc30fb8290213990ca7a14b1b3971140b0d120..0b62bb3a82b0e74bc2a7eb84301c4ec97b14d003 100644
>>> --- a/utils/exportfs/exports.man
>>> +++ b/utils/exportfs/exports.man
>>> @@ -180,8 +180,8 @@ understands the following export options:
>>>  .TP
>>>  .IR secure
>>>  This option requires that requests not using gss originate on an
>>> -Internet port less than IPPORT_RESERVED (1024). This option is on by default.
>>> -To turn it off, specify
>>> +Internet port less than IPPORT_RESERVED (1024). This option is off by default
>>> +but can be explicitly disabled by specifying
>>>  .IR insecure .
>>>  (NOTE: older kernels (before upstream kernel version 4.17) enforced this
>>>  requirement on gss requests as well.)
>>>
>>> ---
>>> base-commit: 2cf015ea4312f37598efe9733fef3232ab67f784
>>> change-id: 20250513-master-89974087bb04
>>>
>>> Best regards,
>>> -- 
>>> Jeff Layton <jlayton@kernel.org>
>>>
>>>
>>>
>>
>>
>>
> 
> 


-- 
Chuck Lever