[CRIU] [PATCH 2/2] crit: Anonymize file paths in files.img

[Pavel Emelianov]

On 8/11/19 12:30 PM, Harshavardhan Unnibhavi wrote:
> Hi Pavel,
> 
> Sorry for the late reply. When we restore the anonymized images(with
> file names anonymized) it fails to restore the task as the files
> themselves don't exist. I have gone through the  criu/pie/restorer.c's
> restore_task() function and have found that lines between 1553 and
> 1599 access the file descriptor from the VMA entry struct.

Of course. The "anonymized" file paths cannot be opened, so you should patch
the criu restore code to make it pretend that the file in question is opened,
but restore some fake file descriptor instead. And abort the restore at the
very end.
 
> I have also traced out the file access steps followed by restore from
> criu/cr-restore.c to criu/files-reg.c. I think the solution would be
> to create a new file with the anonymized name? Where should I insert
> this piece of code,to create a new file if it doesn't exist?

Not create the file with anonymous name, but rather report back a fake file
descriptor. I'd introduce a "--anon" CLI option to the restore action for this.

-- Pavel

> Best,
> Harsha
> 
> On Tue, Jul 9, 2019 at 6:27 PM Pavel Emelianov <xemul at virtuozzo.com> wrote:
>>
>> On 6/30/19 10:53 AM, Harshavardhan Unnibhavi wrote:
>>> File path names are replaced by their corresponding sha1 hash values.
>>> The top level names such as bin, var, usr, lib etc, are kept unchanged.
>>>
>>> Resolve Issue #360.
>>
>> This looks really good :)
>>
>> Let's go ahead and try to teach criu-restore do the restore of the anonymized
>> images until the criu/pie/restorer.c's restore_task() line
>>
>>         restore_finish_stage(task_entries_local, CR_STATE_RESTORE_CREDS);
>>
>> after which the whole restore just aborts and exits.
>>
>>> Signed-off-by: Harshavardhan Unnibhavi <hvubfoss at gmail.com>
>>> ---
>>>  lib/py/anonymize.py | 72 +++++++++++++++++++++++++++++++++++++++++++++
>>>  lib/py/cli.py       |  4 +++
>>>  2 files changed, 76 insertions(+)
>>>  create mode 100644 lib/py/anonymize.py
>>>
>>> diff --git a/lib/py/anonymize.py b/lib/py/anonymize.py
>>> new file mode 100644
>>> index 00000000..42861696
>>> --- /dev/null
>>> +++ b/lib/py/anonymize.py
>>> @@ -0,0 +1,72 @@
>>> +# This file contains methods to anonymize criu images.
>>> +
>>> +# In order to anonymize images three steps are followed:
>>> +#     - decode the binary image to json
>>> +#     - strip the necessary information from the json dict
>>> +#     - encode the json dict back to a binary image, which is now anonymized
>>> +
>>> +# The following contents are being anonymized:
>>> +#     - Paths to files
>>> +
>>> +import hashlib
>>> +
>>> +def files_anon(image):
>>> +    levels = {}
>>> +
>>> +    fname_key = 'reg'
>>> +    checksum  = hashlib.sha1()
>>> +
>>> +    for e in image['entries']:
>>> +        if fname_key in e:
>>> +            f_path = e[fname_key]['name']
>>> +
>>> +        f_path  = f_path.split('/')
>>> +        lev_num = 0
>>> +
>>> +        for i, p in enumerate(f_path):
>>> +            if p == '':
>>> +                continue
>>> +            if lev_num not in levels:
>>> +                levels[lev_num] = {}
>>> +            if p not in levels[lev_num]:
>>> +                if i == 1:
>>> +                    levels[lev_num][p] = p
>>> +                else:
>>> +                    checksum.update(p)
>>> +                    levels[lev_num][p] = checksum.hexdigest()
>>> +            lev_num += 1
>>> +
>>> +    for i, e in enumerate(image['entries']):
>>> +        if fname_key in e:
>>> +            f_path = e[fname_key]['name']
>>> +
>>> +        if f_path == '/':
>>> +            continue
>>> +
>>> +        f_path = f_path.split('/')
>>> +        lev_num = 0
>>> +
>>> +        for j, p in enumerate(f_path):
>>> +            if p == '':
>>> +                continue
>>> +            f_path[j] = levels[lev_num][p]
>>> +            lev_num += 1
>>> +        f_path = '/'.join(f_path)
>>> +        image['entries'][i][fname_key]['name'] = f_path
>>> +
>>> +    return image
>>> +
>>> +anonymizers = {
>>> +    'FILES': files_anon
>>> +}
>>> +
>>> +def anon_handler(image):
>>> +    magic = image['magic']
>>> +
>>> +    if magic != 'FILES':
>>> +        return -1
>>> +
>>> +    handler  = anonymizers[magic]
>>> +    anon_img = handler(image)
>>> +
>>> +    return anon_img
>>> diff --git a/lib/py/cli.py b/lib/py/cli.py
>>> index fdb24dbe..400c084e 100755
>>> --- a/lib/py/cli.py
>>> +++ b/lib/py/cli.py
>>> @@ -6,6 +6,7 @@ import os
>>>  import glob
>>>
>>>  import pycriu
>>> +from anonymize import anon_handler
>>>
>>>  def inf(opts):
>>>       if opts['in']:
>>> @@ -286,6 +287,9 @@ def anonymize(opts):
>>>
>>>               try:
>>>                       img = pycriu.images.load(inf(inf_opts))
>>> +                     anon_dict = anon_handler(img)
>>> +                     if anon_dict != -1:
>>> +                             pycriu.images.dump(anon_dict, outf(inf_opts))
>>>               except pycriu.images.MagicException as exc:
>>>                       print("Unknown magic %#x.\n"\
>>>                                       "Found a raw image" %exc.magic, file=sys.stderr)
>>>
>>
> .
>