openssh bugs - Dec 2004 - [Bug 959] enhancement: supporting a remote scp path option in scp

http://bugzilla.mindrot.org/show_bug.cgi?id=959

           Summary: enhancement: supporting a remote scp path option in scp
           Product: Portable OpenSSH
           Version: -current
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: scp
        AssignedTo: openssh-bugs at mindrot.org
        ReportedBy: dlssh at leach.net.au


I've written some enhancements to scp.c and pathnames.h to enable the scp
to arbitrarily set the remote scp path.
(eg $ scp -e /usr/bin/scp foo user at bar:foo)

I did read the "scp: command not found" FAQ entry but I'm not
quite sure
why we can't do this, unless it's because enhancements to scp are no
longer a priority.  Any other reason why it "is the way it is" other
than
that?

The patch is below, all I've really done is replaced char cmd[CMDNEEDS]
with char *rspcmd throughout.  Forgive any dodgy coding, I'm not a
developer during the day :).  I haven't been able to test the patch below
because I don't have a handy openbsd box, I have tested a patch under the
portable version that seems to work fine.  Let me know if I'm better off
providing that.

My reason for wanting is that it means server side scripts that wrap
around forced commands can tie scp down to the absolute path. 
Incidentally, if there is a reason why anyone thinks this is a bad idea,
please let me know.



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------- Additional Comments From dlssh at leach.net.au  2004-12-04 02:39 -------
Created an attachment (id=745)
 --> (http://bugzilla.mindrot.org/attachment.cgi?id=745&action=view)
patches scp.c and pathname.h

i don't think these two files have changed much since I created this patch
(31/8/2004), so it should be fine to patch directly against the current openbsd
openssh tree.



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dlssh at leach.net.au changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
           Keywords|                            |openbsd
           Priority|P2                          |P3





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------- Additional Comments From djm at mindrot.org  2004-12-06 16:44 -------
I'm not sure that we should add more scp options, when a user can just fix
the
server's $PATH. scp has required a working $PATH for many years and has
survived
without this.



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------- Additional Comments From dlssh at leach.net.au  2004-12-06 17:36 -------
My reason for wanting is that it means server side scripts that wrapper
forced commands can tie scp down to the absolute path.  

When scp is executed is PATH being determined by the user shell (by virtue of
the fact that sshd is doing a sh -c force_cmd)?  In a restricted environment
this would allow me to pattern match against the SSH_ORIGINAL_COMMAND, and I
would rather be matching against an absolute (^/usr/bin/scp...$) command than a
relative one (^scp...$).  Perhaps my fears wrt relative path are unfounded..

Maybe this is unnecessary?
a) because it isn't possible for a user to abuse the PATH variable; or 
b) because the PATH variable can be forced in .ssh/environment

I fine with this patch being rejected if there's a better way to achieve
what I
want to do.



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djm at mindrot.org changed:

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



------- Additional Comments From djm at mindrot.org  2004-12-07 11:59 -------
Reading of ~/.ssh/environment is controlled by the PermitUserEnvironment option
in sshd_config. It defaults to "no". 

The other ssh-related vector by which the environment may be modified by the
user is through environment passing (AcceptEnv in sshd_config, SendEnv in
ssh_config), it too is off by default (on both the client and the server).

So, assuming that the user can't modify shell initialisation files (e.g.
.bashrc), the user's $PATH is under your control and you should be able to
match
on the bare command safely.



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