openssh bugs - Sep 2015 - [Bug 2465] New: openssh portable does not check if arc4random_buf is declared in the system headers?

https://bugzilla.mindrot.org/show_bug.cgi?id=2465

            Bug ID: 2465
           Summary: openssh portable does not check if arc4random_buf is
                    declared in the system headers?
           Product: Portable OpenSSH
           Version: 7.1p1
          Hardware: amd64
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P5
         Component: Build system
          Assignee: unassigned-bugs at mindrot.org
          Reporter: busterb at gmail.com

Hi,

 I got this report about the build process of openssh portable only
checking if arc4random_buf links, not if it is declared in a header. 
It should probably ensure that the function exists in a header and set
the local compatibility header define appropriately.

https://github.com/libressl-portable/portable/issues/109

Thanks!

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |djm at mindrot.org

--- Comment #1 from Damien Miller <djm at mindrot.org> ---
So libressl implements this but doesn't provide a prototype for it? IMO
that's broken - it should use symbol visibility to hide functions that
it uses internally but doesn't intend to provide to library users.

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--- Comment #2 from Brent Cook <busterb at gmail.com> ---
We could perhaps conditionally provide a prototype, but it would be in
a nonstandard location. It would be better if programs did not have to
guess whether arc4random_buf is in stdlib.h or some random libressl
header, no? In other words, even if we did expose the prototype, I
believe openssh would still have to do a header check to see if it is
stdlib.h or elsewhere.

The symbol export is intentional, as the arc4random_buf in libcrypto
then shared between libssl, openssl(1) and libtls.

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--- Comment #3 from Damien Miller <djm at mindrot.org> ---
I was wondering why this was causing problems at all - normally we
wouldn't pick up these symbols from libcrypto because most library
tests are done only against libc. So I checked this history to see why
these were done late:
> commit 00f9cd230709c04399ef5ff80492d70a55230694
> Author: Damien Miller <djm at mindrot.org>
> Date:   Tue Jul 15 10:41:38 2014 +1000
> 
> - (djm) [configure.ac] Delay checks for arc4random* until after libcrypto
>   has been located; fixes builds agains libressl-portable
So this used to work. What changed?

IMO if you're going to provide replacements for functions usually in
libc, then you should provide prototypes for them too. You can't expect
programs to pick up your symbols but provide their own prototypes -
what if your prototype doesn't match ours?

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--- Comment #4 from Damien Miller <djm at mindrot.org> ---
Created attachment 2721
  --> https://bugzilla.mindrot.org/attachment.cgi?id=2721&action=edit
unconditionally define prototypes for libressl

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Attachment #2721|0                           |1
        is obsolete|                            |

--- Comment #5 from Damien Miller <djm at mindrot.org> ---
Created attachment 2722
  --> https://bugzilla.mindrot.org/attachment.cgi?id=2722&action=edit
fixed diff

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--- Comment #6 from Damien Miller <djm at mindrot.org> ---
could you please try the patch on this bug and see if it fixes things
for you?

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