Re: [OE-core] [PATCH v3] wic: ensure generated disk system identifier is non-zero

[Ed Bartosh]

On Mon, Jul 31, 2017 at 06:04:47PM +1000, Jonathan Liu wrote:
> >
> > How about random.SystemRandom().randrange(1, 0x) ?
> >
> 
> random.SystemRandom().randint(1, 0x) actually
> 

This looks ok to me. Thanks.

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Re: [OE-core] [PATCH v3] wic: ensure generated disk system identifier is non-zero

[Jonathan Liu]

On 31 July 2017 at 17:58, Jonathan Liu  wrote:
> Hi Ed,
>
> On 31 July 2017 at 17:28, Ed Bartosh  wrote:
>> On Sun, Jul 30, 2017 at 08:37:26PM +1000, Jonathan Liu wrote:
>>> Hi Ed,
>>>
>>> On 30 July 2017 at 20:02, Ed Bartosh  wrote:
>>> > On Sat, Jul 29, 2017 at 12:45:27AM +1000, Jonathan Liu wrote:
>>> >> Zero may be interpreted as no MBR signature present and another
>>> >> partitioning program might install a new MBR signature.
>>> >>
>>> >> Signed-off-by: Jonathan Liu 
>>> >> ---
>>> >>  scripts/lib/wic/plugins/imager/direct.py | 2 +-
>>> >>  1 file changed, 1 insertion(+), 1 deletion(-)
>>> >>
>>> >> diff --git a/scripts/lib/wic/plugins/imager/direct.py 
>>> >> b/scripts/lib/wic/plugins/imager/direct.py
>>> >> index f20d8433f1..fe9b688ab0 100644
>>> >> --- a/scripts/lib/wic/plugins/imager/direct.py
>>> >> +++ b/scripts/lib/wic/plugins/imager/direct.py
>>> >> @@ -297,7 +297,7 @@ class PartitionedImage():
>>> >># all partitions (in bytes)
>>> >>  self.ptable_format = ptable_format  # Partition table format
>>> >>  # Disk system identifier
>>> >> -self.identifier = int.from_bytes(os.urandom(4), 'little')
>>> >> +self.identifier = int.from_bytes(os.urandom(4), 'little') or 
>>> >> 0x
>>> >>
>>> >
>>> > Can we generate random identifier by calling os.urandom again if
>>> > self.identifier is zero? Something like this, may be?
>>> >
>>> > while True:
>>> > self.identifier = int.from_bytes(os.urandom(4), 'little')
>>> > if self.identifier:
>>> > break
>>> >
>>> > Assigning constant 0x can potentially create nonunique 
>>> > identifiers.
>>> >
>>>
>>> There is no guarantee that urandom will create unique identifiers.
>> We can't have a guarantee with urandom, true. My point was that if you
>> need random value it's better to call urandom again than using a constant 
>> value.
>>
>>> Infinite loop needs a timeout and error in the case it is unable to
>>> generate a suitable identifier.
>> I'm not sure it's needed, but it's not a big deal to add this. I really
>> doubt os.urandom can generate long enough sequence of zeros.
>>
>>> It is only 0x if it is 0. That
>>> means 0x is twice as likely to occur (2 in 4294967296 instead
>>> of 1 in 4294967296) so there is tiny bias. Note that this is how it is
>>> implemented for the DISK_SIGNATURE variable in OE and in GNU Parted as
>>> well.
>> Does this mean we shouldn't do better?
>>
>
> How about random.SystemRandom().randrange(1, 0x) ?
>

random.SystemRandom().randint(1, 0x) actually

>>> >>  self.partitions = partitions
>>> >>  self.partimages = []
>>> >> --
>>> >> 2.13.2
>>> >>
>>> >> --
>>> >> ___
>>> >> Openembedded-core mailing list
>>> >> Openembedded-core@lists.openembedded.org
>>> >> http://lists.openembedded.org/mailman/listinfo/openembedded-core
>>>
>>> Regards,
>>> Jonathan
>>
>> --
>> Regards,
>> Ed
>
> Regards,
> Jonathan
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Re: [OE-core] [PATCH v3] wic: ensure generated disk system identifier is non-zero

[Jonathan Liu]

Hi Ed,

On 31 July 2017 at 17:28, Ed Bartosh  wrote:
> On Sun, Jul 30, 2017 at 08:37:26PM +1000, Jonathan Liu wrote:
>> Hi Ed,
>>
>> On 30 July 2017 at 20:02, Ed Bartosh  wrote:
>> > On Sat, Jul 29, 2017 at 12:45:27AM +1000, Jonathan Liu wrote:
>> >> Zero may be interpreted as no MBR signature present and another
>> >> partitioning program might install a new MBR signature.
>> >>
>> >> Signed-off-by: Jonathan Liu 
>> >> ---
>> >>  scripts/lib/wic/plugins/imager/direct.py | 2 +-
>> >>  1 file changed, 1 insertion(+), 1 deletion(-)
>> >>
>> >> diff --git a/scripts/lib/wic/plugins/imager/direct.py 
>> >> b/scripts/lib/wic/plugins/imager/direct.py
>> >> index f20d8433f1..fe9b688ab0 100644
>> >> --- a/scripts/lib/wic/plugins/imager/direct.py
>> >> +++ b/scripts/lib/wic/plugins/imager/direct.py
>> >> @@ -297,7 +297,7 @@ class PartitionedImage():
>> >># all partitions (in bytes)
>> >>  self.ptable_format = ptable_format  # Partition table format
>> >>  # Disk system identifier
>> >> -self.identifier = int.from_bytes(os.urandom(4), 'little')
>> >> +self.identifier = int.from_bytes(os.urandom(4), 'little') or 
>> >> 0x
>> >>
>> >
>> > Can we generate random identifier by calling os.urandom again if
>> > self.identifier is zero? Something like this, may be?
>> >
>> > while True:
>> > self.identifier = int.from_bytes(os.urandom(4), 'little')
>> > if self.identifier:
>> > break
>> >
>> > Assigning constant 0x can potentially create nonunique identifiers.
>> >
>>
>> There is no guarantee that urandom will create unique identifiers.
> We can't have a guarantee with urandom, true. My point was that if you
> need random value it's better to call urandom again than using a constant 
> value.
>
>> Infinite loop needs a timeout and error in the case it is unable to
>> generate a suitable identifier.
> I'm not sure it's needed, but it's not a big deal to add this. I really
> doubt os.urandom can generate long enough sequence of zeros.
>
>> It is only 0x if it is 0. That
>> means 0x is twice as likely to occur (2 in 4294967296 instead
>> of 1 in 4294967296) so there is tiny bias. Note that this is how it is
>> implemented for the DISK_SIGNATURE variable in OE and in GNU Parted as
>> well.
> Does this mean we shouldn't do better?
>

How about random.SystemRandom().randrange(1, 0x) ?

>> >>  self.partitions = partitions
>> >>  self.partimages = []
>> >> --
>> >> 2.13.2
>> >>
>> >> --
>> >> ___
>> >> Openembedded-core mailing list
>> >> Openembedded-core@lists.openembedded.org
>> >> http://lists.openembedded.org/mailman/listinfo/openembedded-core
>>
>> Regards,
>> Jonathan
>
> --
> Regards,
> Ed

Regards,
Jonathan
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Re: [OE-core] [PATCH v3] wic: ensure generated disk system identifier is non-zero

[Ed Bartosh]

On Sun, Jul 30, 2017 at 08:37:26PM +1000, Jonathan Liu wrote:
> Hi Ed,
> 
> On 30 July 2017 at 20:02, Ed Bartosh  wrote:
> > On Sat, Jul 29, 2017 at 12:45:27AM +1000, Jonathan Liu wrote:
> >> Zero may be interpreted as no MBR signature present and another
> >> partitioning program might install a new MBR signature.
> >>
> >> Signed-off-by: Jonathan Liu 
> >> ---
> >>  scripts/lib/wic/plugins/imager/direct.py | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/scripts/lib/wic/plugins/imager/direct.py 
> >> b/scripts/lib/wic/plugins/imager/direct.py
> >> index f20d8433f1..fe9b688ab0 100644
> >> --- a/scripts/lib/wic/plugins/imager/direct.py
> >> +++ b/scripts/lib/wic/plugins/imager/direct.py
> >> @@ -297,7 +297,7 @@ class PartitionedImage():
> >># all partitions (in bytes)
> >>  self.ptable_format = ptable_format  # Partition table format
> >>  # Disk system identifier
> >> -self.identifier = int.from_bytes(os.urandom(4), 'little')
> >> +self.identifier = int.from_bytes(os.urandom(4), 'little') or 
> >> 0x
> >>
> >
> > Can we generate random identifier by calling os.urandom again if
> > self.identifier is zero? Something like this, may be?
> >
> > while True:
> > self.identifier = int.from_bytes(os.urandom(4), 'little')
> > if self.identifier:
> > break
> >
> > Assigning constant 0x can potentially create nonunique identifiers.
> >
>
> There is no guarantee that urandom will create unique identifiers.
We can't have a guarantee with urandom, true. My point was that if you
need random value it's better to call urandom again than using a constant value.

> Infinite loop needs a timeout and error in the case it is unable to
> generate a suitable identifier.
I'm not sure it's needed, but it's not a big deal to add this. I really
doubt os.urandom can generate long enough sequence of zeros.

> It is only 0x if it is 0. That
> means 0x is twice as likely to occur (2 in 4294967296 instead
> of 1 in 4294967296) so there is tiny bias. Note that this is how it is
> implemented for the DISK_SIGNATURE variable in OE and in GNU Parted as
> well.
Does this mean we shouldn't do better?

> >>  self.partitions = partitions
> >>  self.partimages = []
> >> --
> >> 2.13.2
> >>
> >> --
> >> ___
> >> Openembedded-core mailing list
> >> Openembedded-core@lists.openembedded.org
> >> http://lists.openembedded.org/mailman/listinfo/openembedded-core
>
> Regards,
> Jonathan

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Re: [OE-core] [PATCH v3] wic: ensure generated disk system identifier is non-zero

[Jonathan Liu]

Hi Ed,

On 30 July 2017 at 20:02, Ed Bartosh  wrote:
> On Sat, Jul 29, 2017 at 12:45:27AM +1000, Jonathan Liu wrote:
>> Zero may be interpreted as no MBR signature present and another
>> partitioning program might install a new MBR signature.
>>
>> Signed-off-by: Jonathan Liu 
>> ---
>>  scripts/lib/wic/plugins/imager/direct.py | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/scripts/lib/wic/plugins/imager/direct.py 
>> b/scripts/lib/wic/plugins/imager/direct.py
>> index f20d8433f1..fe9b688ab0 100644
>> --- a/scripts/lib/wic/plugins/imager/direct.py
>> +++ b/scripts/lib/wic/plugins/imager/direct.py
>> @@ -297,7 +297,7 @@ class PartitionedImage():
>># all partitions (in bytes)
>>  self.ptable_format = ptable_format  # Partition table format
>>  # Disk system identifier
>> -self.identifier = int.from_bytes(os.urandom(4), 'little')
>> +self.identifier = int.from_bytes(os.urandom(4), 'little') or 
>> 0x
>>
>
> Can we generate random identifier by calling os.urandom again if
> self.identifier is zero? Something like this, may be?
>
> while True:
> self.identifier = int.from_bytes(os.urandom(4), 'little')
> if self.identifier:
> break
>
> Assigning constant 0x can potentially create nonunique identifiers.
>

There is no guarantee that urandom will create unique identifiers.
Infinite loop needs a timeout and error in the case it is unable to
generate a suitable identifier. It is only 0x if it is 0. That
means 0x is twice as likely to occur (2 in 4294967296 instead
of 1 in 4294967296) so there is tiny bias. Note that this is how it is
implemented for the DISK_SIGNATURE variable in OE and in GNU Parted as
well.

>>  self.partitions = partitions
>>  self.partimages = []
>> --
>> 2.13.2
>>
>> --
>> ___
>> Openembedded-core mailing list
>> Openembedded-core@lists.openembedded.org
>> http://lists.openembedded.org/mailman/listinfo/openembedded-core
>
> --
> --
> Regards,
> Ed

Regards,
Jonathan
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Re: [OE-core] [PATCH v3] wic: ensure generated disk system identifier is non-zero

[Ed Bartosh]

On Sat, Jul 29, 2017 at 12:45:27AM +1000, Jonathan Liu wrote:
> Zero may be interpreted as no MBR signature present and another
> partitioning program might install a new MBR signature.
> 
> Signed-off-by: Jonathan Liu 
> ---
>  scripts/lib/wic/plugins/imager/direct.py | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/scripts/lib/wic/plugins/imager/direct.py 
> b/scripts/lib/wic/plugins/imager/direct.py
> index f20d8433f1..fe9b688ab0 100644
> --- a/scripts/lib/wic/plugins/imager/direct.py
> +++ b/scripts/lib/wic/plugins/imager/direct.py
> @@ -297,7 +297,7 @@ class PartitionedImage():
># all partitions (in bytes)
>  self.ptable_format = ptable_format  # Partition table format
>  # Disk system identifier
> -self.identifier = int.from_bytes(os.urandom(4), 'little')
> +self.identifier = int.from_bytes(os.urandom(4), 'little') or 
> 0x
>  

Can we generate random identifier by calling os.urandom again if
self.identifier is zero? Something like this, may be?

while True:
self.identifier = int.from_bytes(os.urandom(4), 'little')
if self.identifier:
break

Assigning constant 0x can potentially create nonunique identifiers.

>  self.partitions = partitions
>  self.partimages = []
> -- 
> 2.13.2
> 
> -- 
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> Openembedded-core@lists.openembedded.org
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Regards,
Ed
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