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s2n_stuffer_skip_write usage pattern #2078

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baldwinmatt opened this issue Jun 26, 2020 · 2 comments
Open

s2n_stuffer_skip_write usage pattern #2078

baldwinmatt opened this issue Jun 26, 2020 · 2 comments
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CBMC difficulty/beginner good first issue

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@baldwinmatt
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@baldwinmatt baldwinmatt commented Jun 26, 2020

Problem:

A common pattern is:

GUARD(s2n_stuffer_skip_write(stuffer, bytes_to_write));
uint8_t* ptr = suffer->blob.data + stuffer->write_cursor - bytes_to_write;

which could be simplified.

Solution:

*ptr could be an *out parameter to s2n_stuffer_skip_write

  • Does this change what S2N sends over the wire? No.
  • Does this change any public APIs? No.
  • Which versions of TLS will this impact? N/A.

Requirements / Acceptance Criteria:

What must a solution address in order to solve the problem? How do we know the solution is complete?

  • Testing: Existing tests should pass as is, however CBMC proofs will need to be updated to match thew new stuffer API
    • Will this change trigger SAW changes? No.
    • Should this change be fuzz tested? N/A

Out of scope:

Is there anything the solution will intentionally NOT address?

No
@baldwinmatt baldwinmatt added good first issue difficulty/beginner CBMC labels Jun 26, 2020
@baldwinmatt baldwinmatt mentioned this issue Jun 26, 2020
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@danielsn
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@danielsn danielsn commented Jun 26, 2020

Actually, would it make sense for the skip_write to return a s2n_blob_slice, so we carry around both the size, and the pointer together? https://github.com/awslabs/s2n/blob/0e74e54a14c4f48f95ebcb24cffd6690d0c11e4d/utils/s2n_blob.c#L55
@baldwinmatt
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@baldwinmatt baldwinmatt commented Jun 30, 2020

Actually, would it make sense for the skip_write to return a s2n_blob_slice, so we carry around both the size, and the pointer together?

https://github.com/awslabs/s2n/blob/0e74e54a14c4f48f95ebcb24cffd6690d0c11e4d/utils/s2n_blob.c#L55

love it!
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Labels
CBMC difficulty/beginner good first issue
2 participants
@danielsn @baldwinmatt