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  • GNAT.SHA256 produces result different from sha257sum on Linux

    From wvxvw@21:1/5 to All on Sat Nov 4 15:39:37 2023
    Hello. (Sorry for duplication, the first attempt to send this sent it as
    a response to an unrelated thread).

    I'm learning Ada as well as how to use Usenet, so don't be too harsh.
    As a learning exercise, I want to write a program that, beside other
    things, needs to compute SHA256 hashes. I discovered GNAT.SHA256
    library and was able to use it (by calling Digest(<some string>)),
    however the result is different from what I'd get for the same string
    with running sha256sum.

    Eg, with GNAT.SHA256 for string "foo" I get:

    ❯ ./bin/test_sha --arg foo 2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae
    ❯ echo foo | sha256sum - b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c -

    My Ada code looks (with some unrelated stuff removed) like this:

    with GNAT.Command_Line; use GNAT.Command_Line;
    with GNAT.SHA256; use GNAT.SHA256;

    procedure Main is
    loop
    case Getopt ("-arg=") is
    when '-' =>
    if Full_Switch = "-arg" then
    Put_Line (Digest (Parameter));
    end if;
    end case;
    end loop;
    end Main;

    My understanding is that there are plenty of configuration settings to
    how the checksum is computed, but I know very little about it. My goal
    is to produce the same checksum as would be produced by sha256sum
    though, as the checksums are to be used outside of my program.

    Finally: is GNAT.SHA256 a good way to go if I need this functionality (I
    don't care about portability, if that's a concern)?

    Thanks!

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jeffrey R.Carter@21:1/5 to wvxvw on Sat Nov 4 16:09:58 2023
    On 2023-11-04 15:39, wvxvw wrote:

    ❯ ./bin/test_sha --arg foo 2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae
    ❯ echo foo | sha256sum - b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c -

    I think the problem may be that echo adds an LF:

    $ echo foo | hd
    00000000 66 6f 6f 0a |foo.|

    Since sha256sum expects to work on arbitrary files, it would include the LF in its input.

    --
    Jeff Carter
    "You can never forget too much about C++."
    115

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Niklas Holsti@21:1/5 to Jeffrey R.Carter on Sat Nov 4 18:49:58 2023
    On 2023-11-04 17:09, Jeffrey R.Carter wrote:
    On 2023-11-04 15:39, wvxvw wrote:

    ❯ ./bin/test_sha --arg foo
    2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae
    ❯ echo foo | sha256sum -
    b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c  -

    I think the problem may be that echo adds an LF:

    $ echo foo | hd
    00000000  66 6f 6f 0a                                       |foo.|

    Since sha256sum expects to work on arbitrary files, it would include the
    LF in its input.


    Some implementations of "echo" accept an option "-n" to suppress the
    trailing newline (LF). The OP could try that option as a quick check of
    this answer (which seems very plausible).

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From wvxvw@21:1/5 to Jeffrey R.Carter on Sat Nov 4 17:48:03 2023
    "Jeffrey R.Carter" <spam.jrcarter.not@spam.acm.org.not> writes:

    I think the problem may be that echo adds an LF:

    $ echo foo | hd
    00000000 66 6f 6f 0a |foo.|

    Since sha256sum expects to work on arbitrary files, it would include
    the LF in its input.

    Hi, thanks for the idea, but no, that's not it. With the line end added
    I get 04e1806fda6bdbc9e5e3534edd993c7c2bf03173f5489742db53d1e8b0ef8c61
    from Ada.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Ben Bacarisse@21:1/5 to wvxvw on Sat Nov 4 17:53:34 2023
    wvxvw <olegsivokon@gmail.com> writes:

    "Jeffrey R.Carter" <spam.jrcarter.not@spam.acm.org.not> writes:

    I think the problem may be that echo adds an LF:

    $ echo foo | hd
    00000000 66 6f 6f 0a |foo.|

    Since sha256sum expects to work on arbitrary files, it would include
    the LF in its input.

    Hi, thanks for the idea, but no, that's not it.

    You say that's not it, but with the newline removed, sha256sum gives the
    same hash as your original test code:

    $ printf foo | sha256sum - 2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae -

    From your earlier post:
    Eg, with GNAT.SHA256 for string "foo" I get:

    ❯ ./bin/test_sha --arg foo 2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae

    With the line end added
    I get 04e1806fda6bdbc9e5e3534edd993c7c2bf03173f5489742db53d1e8b0ef8c61
    from Ada.

    Ah! You didn't add a newline! I can get the same hash by guesswork:

    $ printf foo\\\\n >input
    $ sha256sum input 04e1806fda6bdbc9e5e3534edd993c7c2bf03173f5489742db53d1e8b0ef8c61 input
    $ hd input
    00000000 66 6f 6f 5c 6e |foo\n|
    00000005

    What you added to the test string was a backslash and a letter n.

    --
    Ben.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jeffrey R.Carter@21:1/5 to wvxvw on Sat Nov 4 18:39:51 2023
    On 2023-11-04 17:09, Jeffrey R.Carter wrote:
    On 2023-11-04 15:39, wvxvw wrote:

    ❯ ./bin/test_sha --arg foo
    2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae
    ❯ echo foo | sha256sum -
    b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c  -

    I think the problem may be that echo adds an LF:

    $ echo foo | hd
    00000000  66 6f 6f 0a                                       |foo.|

    Since sha256sum expects to work on arbitrary files, it would include the LF in
    its input.

    wvxvw wrote:

    Hi, thanks for the idea, but no, that's not it. With the line end added
    I get 04e1806fda6bdbc9e5e3534edd993c7c2bf03173f5489742db53d1e8b0ef8c61
    from Ada.

    On 2023-11-04 17:49, Niklas Holsti wrote:

    Some implementations of "echo" accept an option "-n" to suppress the trailing newline (LF). The OP could try that option as a quick check of this answer (which seems very plausible).

    $ echo -n foo | hd
    00000000 66 6f 6f |foo|
    $ echo -n foo | sha256sum - 2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae -

    Interesting results.

    --
    Jeff Carter
    "You can never forget too much about C++."
    115

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From wvxvw@21:1/5 to Ben Bacarisse on Sat Nov 4 20:26:34 2023
    Ben Bacarisse <ben.usenet@bsb.me.uk> writes:

    Ah! You didn't add a newline! I can get the same hash by guesswork:

    $ printf foo\\\\n >input
    $ sha256sum input 04e1806fda6bdbc9e5e3534edd993c7c2bf03173f5489742db53d1e8b0ef8c61 input
    $ hd input
    00000000 66 6f 6f 5c 6e |foo\n|
    00000005

    What you added to the test string was a backslash and a letter n.

    Yeah, thanks! I realized this too by trying to do this in Python:

    >>> import hashlib
    >>> hashlib.sha256('foo'.encode()).hexdigest()
    '2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae'
    >>> hashlib.sha256('foo\n'.encode()).hexdigest()
    'b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c'

    Thanks again.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)