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Bug 768112 - ValueError: String can't be PCKS7-padded in the mock service
ValueError: String can't be PCKS7-padded in the mock service
Status: RESOLVED FIXED
Product: libsecret
Classification: Other
Component: General
0.18.x
Other Linux
: Normal normal
: ---
Assigned To: libsecret maintainer(s)
libsecret maintainer(s)
Depends on:
Blocks:
 
 
Reported: 2016-06-27 19:54 UTC by Dmitry Shachnev
Modified: 2017-11-07 14:46 UTC
See Also:
GNOME target: ---
GNOME version: ---

Attachments
mock: Pad the common secret with zero bytes to make it exactly 128 bytes long (974 bytes, patch)
2017-10-08 18:37 UTC, Dmitry Shachnev 		accepted-commit_now Details | Review

Description Dmitry Shachnev 2016-06-27 19:54:46 UTC 
Hi,

I'm (mis)using libsecret's mock service for testing my own code on Travis. It usually works OK, but in some rare case I get this error:

python3 ./libsecret/libsecret/mock-service-normal.py
Traceback (most recent call last):

+ Trace 236396

  • File "/usr/lib/python3/dist-packages/dbus/service.py", line 707 in _message_cb 
    retval = candidate_method(self, *args, **keywords)
  • File "./libsecret/libsecret/mock/service.py", line 390 in CreateItem 
    (secret, content_type) = session.decode_secret(value)
  • File "./libsecret/libsecret/mock/service.py", line 172 in decode_secret 
    plain = self.algorithm.decrypt(self.key, value[1], value[2])
  • File "./libsecret/libsecret/mock/service.py", line 108 in decrypt 
    return aes.strip_PKCS7_padding(decr)
  • File "./libsecret/libsecret/mock/aes.py", line 27 in strip_PKCS7_padding 
    raise ValueError("String ending with %r can't be PCKS7-padded" % s[-1])
ValueError: String ending with 22 can't be PCKS7-padded 

I think I just got this error for a second or third time. This time it happened when calling CreateItem method on a collection interface.

I don't know much about mock code but I suspect it may be wrong handling of cases where first/last byte of a key is zero (in this case the error will happen approx. one time of 256).
Comment 1 Dmitry Shachnev 2017-10-08 18:37:28 UTC 
Created attachment 361147 [details] [review]
mock: Pad the common secret with zero bytes to make it exactly 128 bytes long

I finally found some time to debug this. It happens because the mock implementation does not pad the common DH secret with zero bytes, but my module and libsecret’s own C code do it:

https://git.gnome.org/browse/libsecret/tree/egg/egg-dh.c#n340

Attaching a patch to fix this.
Comment 2 Dmitry Shachnev 2017-11-07 10:21:15 UTC 
Stef: any chance you can commit this patch?
Comment 3 Stef Walter 2017-11-07 14:19:51 UTC 
Review of attachment 361147 [details] [review]:

Looks good to me!
Comment 4 Dmitry Shachnev 2017-11-07 14:22:04 UTC 
Please push, I do not have rights :(
Comment 5 Stef Walter 2017-11-07 14:46:05 UTC 
Merged to git master.