openssh bugs - Oct 2017 - [Bug 2791] New: Match host exec doesn't resolve SHELL in the PATH

https://bugzilla.mindrot.org/show_bug.cgi?id=2791

            Bug ID: 2791
           Summary: Match host exec doesn't resolve SHELL in the PATH
           Product: Portable OpenSSH
           Version: 7.2p2
          Hardware: amd64
                OS: Mac OS X
            Status: NEW
          Severity: enhancement
          Priority: P5
         Component: ssh
          Assignee: unassigned-bugs at mindrot.org
          Reporter: berdario at google.com

If you have something like

  Match host *.example.com exec /usr/bin/true
    ProxyCommand /usr/local/bin/ssh-helper %h %p

in your ssh config, and your SHELL contains the name of the shell
executable (and not its path), connection will fail with:

Unable to execute '/usr/bin/true': No such file or directory
command '/usr/bin/true' exited abnormally
/etc/ssh_config line 46: match exec '/usr/bin/true' error

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Damien Miller <djm at mindrot.org> changed:

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

--- Comment #1 from Damien Miller <djm at mindrot.org> ---
I don't think searching $PATH for SHELL is correct. The system shoudl
never set $SHELL to a relative path and
http://pubs.opengroup.org/onlinepubs/009695399/functions/system.html
specifies system(3) to use execl(2), and it doesn't search $PATH.

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--- Comment #2 from berdario at google.com ---
Uhm, system(3) should use sh(1)

manpages for sh(1) on my system are explicitly about bash, but
otherwise I think it should be about this:

http://pubs.opengroup.org/onlinepubs/009695399/utilities/sh.html

which says that the path for `sh` should be resolved from PATH

(I was under the impression that the POSIX standard specified that
/bin/sh would always have to exist, but I guess I was wrong?)

I haven't looked into openssh source code, but given the above, I'd be
surprised if it used system(3)

I understand that the behavior might not be changed, but the error
message

Unable to execute '/usr/bin/true': No such file or directory

Seems to be a bit misleading to me, given that the actual command
executed would've been something like

sh -c /usr/bin/true

Thanks anyhow for looking into this

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--- Comment #3 from berdario at google.com ---
Forgot to add:


  Unable to execute 'sh': No such file or directory


Would've been much clearer as an error message, imho

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Roland Friedwagner <r.friedwagner at gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |r.friedwagner at gmail.com

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dtucker at dtucker.net
   Attachment #3302|                            |ok?(dtucker at dtucker.net)
              Flags|                            |

--- Comment #4 from Damien Miller <djm at mindrot.org> ---
Created attachment 3302
  --> https://bugzilla.mindrot.org/attachment.cgi?id=3302&action=edit
check shell is executable to provide better error message

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
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             Blocks|                            |2988


Referenced Bugs:

https://bugzilla.mindrot.org/show_bug.cgi?id=2988
[Bug 2988] Tracking bug for 8.1 release
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Darren Tucker <dtucker at dtucker.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Attachment #3302|ok?(dtucker at dtucker.net)    |ok+
              Flags|                            |

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #5 from Damien Miller <djm at mindrot.org> ---
patch applied and will be in openssh-8.1, due soon. Thanks!

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |CLOSED

--- Comment #6 from Damien Miller <djm at mindrot.org> ---
closing resolved bugs as of 8.6p1 release

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