sftp-server

[John Syer]

Hi All,

Thanks Matt for the reply.  As is often the case, after I'd e-mailed you 
I decided to give it a go and see how I would fare having a wild stab in 
the dark (well, more sort of a half-hearted slash at late dusk) and I 
got it working.  I had downloaded the sources for OpenSSH-4.2p1, 
OpenSSL-0.9.8a, and zlib-1.2.3 when I was thinking of using OpenSSH ages 
ago so used those.
I found that I needed zlib (--with-zlib option), OpenSSL (--with-ssl-dir 
option) and the OpenSSL headers (CPPFLAGS=-I/path/to/ssl/header/files) 
to (cross)compile sftp-server.  Then I dumped sftp-server onto my box 
and away she went.  I've pasted the entire .configure command line 
below, in case anyone else is interested

./configure 
CC=~/opt/crosstool/arm-xscale-linux-gnu/gcc-3.4.2-glibc-2.3.3/bin/arm-xscale-linux-gnu-gcc 
CPPFLAGS=-I~/include --build=xscale --host=arm-xscale-linux-gnu 
--with-zlib=~/src/zlib-1.2.3/ --with-ssl-dir=~/lib/ 
--disable-etc-default-login

John

Matt Johnston wrote:

>(CCing the Dropbear list since it might be of interest)
>
>On Thu, Jan 18, 2007 at 12:55:53PM +1100, John wrote:
>  
>
>>I'm using an editor called ultraedit, 
>>which has the capability of editing remote files through the use of 
>>ftp/sftp, and I am not sure where to start in getting sftp to work with 
>>dropbear.  I have seen mention of using the OpenSSH implimentation of 
>>sftp-server on the internet, but originally rejected OpenSSH in favour 
>>of dropbear because of size constraints.  Is there any info kicking 
>>around about how to use sftp with dropbear (or how much of the OpenSSH 
>>package is required to use it's version of sftp-server)?  Alternately, 
>>is there any future plans to encorporate sftp into dropbear?
>>    
>>
>
>It's fairly easy to compile OpenSSH's sftp-server without
>linking to OpenSSL, and it should end up reasonably small. A
>fair amount of of code depends on OpenSSL headers, so
>you'll probably have to put them somewhere visible even if
>you don't bother compiling OpenSSL libraries for your target
>platform. 
>
>1) Grab a recent OpenSSH release. (I had 4.2p1 handy)
>
>2) Edit configure.ac, remove the OpenSSL tests. (Or maybe
>   leave the header tests in?)
>
>3) autoconf; autoheader     (to regenerate 'configure')
>
>4) Edit Makefile.in, remove the $(LIBS) part of the
>   sftp-server build line (line 160, after the one that
>   begins with "sftp-server$(EXEEXT):")
>
>5) ./configure    (with target platform CC, CFLAGS etc)
>
>6) Edit bufaux.c and bufaux.h, remove all the functions
>   related to bignums. Also remove the #include for openssl
>
>7) make sftp-server
>
>8) Copy the sftp-server binary to /usr/libexec/sftp-server
>   or similar on the target (edit Dropbear's options.h to
>   set where)
>
>I end up with a 35kB dynamic binary on x86 Debian.  You
>could probably combine sftp-server into a dropbearmulti
>binary with a bit of work fiddling with the main() function.
>There might be other code that could be trimmed from
>sftp-server, I haven't looked too closely.
>
>I'm unlikely to develop my own sftp-server for Dropbear in
>the near future.
>
>Cheers,
>Matt
>  
>