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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<TITLE>Using the File Transfer Service</TITLE>
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<A NAME="4"><!-- Empty --></A>
<H2>4 Using the File Transfer Service</H2>
<A NAME="4.1"><!-- Empty --></A>
<H3>4.1 Overview</H3>
<P>This chapter describes how two File Transfer Service applications interact.
<A NAME="4.1.1"><!-- Empty --></A>
<H4>4.1.1 Components</H4>
<P>There are several ways the OMG File Transfer Service can be used.
Below one scenario is visualized:
<P>
<CENTER>
<IMG ALT="CosFileTransfer" SRC="CosFileTransfer.gif"><BR>
<EM><A NAME="CosFileTransfer"><!-- Empty --></A>Figure 1: The File Transfer Service Components.</EM>
</CENTER>
<P>
<UL>
<LI>
<STRONG>Source ORB:</STRONG> this is the ORB we want to transfer a file from/via and it holds
an object reference to a
<A HREF="CosFileTransfer_VirtualFileSystem.html">Virtual File System (VFS)</A> which,
in this example, represents an FTP server.
</LI>
<LI>
<STRONG>Target ORB:</STRONG> the goal may be, for example, to transfer a new file or append to an
existing file placed at the location that this ORB's <CODE>VFS</CODE> represents.
In this scenario it is the local disk or the NFS.
</LI>
<LI>
<STRONG>Transport Protocol:</STRONG> initially the ORB's, i.e., target and source, communicate via
normal <CODE>CORBA</CODE> requests to determine whether or not they can communicate. If the
File Transfer Service's have one, or more, <CODE>Transport Protocol</CODE> in common the data
will be streamed using this protocol. The cosFileTransfer application currently supports
<CODE>TCP/IP</CODE> and <CODE>SSL</CODE>.
</LI>
</UL>
<P>Which type of file system the <CODE>VFS</CODE> is supposed to represent is determined
by the options given when creating it, which is also how one determine which
<CODE>Transport Protocol</CODE> to use. Hence, the source and target <CODE>VFS</CODE> described above
can be started by invoking, respectively, the following operations:
<PRE>
1> SVFS = cosFileTransferApp:create_VFS('FTP', [], Host, 21, [{protocol, tcp}]),
2> TVFS = cosFileTransferApp:create_VFS({'NATIVE', 'cosFileTransferNATIVE_file'},
[], OtherHost, 0, [{protocol, tcp}]),
</PRE>
<P>Naturally can any combination of <CODE>VFS</CODE>-types be used and it is also possible
to use own drivers, i.e., <CODE>{'NATIVE', 'MyDriver'}</CODE>.
<P>After creating necessary <CODE>VFS's</CODE> we can login in and perform operations
on files and directories residing on each file system.<A NAME="4.1.2"><!-- Empty --></A>
<H4>4.1.2 How To Use SSL</H4>
<P>To be able to use <CODE>SSL</CODE> as transport protocol a few configuration
parameters must be set. The required parameters depend on if Orber is
the target or/and the source ORB. However, the SSL_CERT_FILE variable
must be defined in both cases.
<P>Setting of a CA certificate file with an option does not work due to
weaknesses in the SSLeay package. A work-around in the ssl application is
to set the OS environment variable SSL_CERT_FILE before SSL is started.
However, then the CA certificate file will be global for all connections
(both incomming and outgoing calls).<A NAME="4.1.2.1"><!-- Empty --></A>
<H5>4.1.2.1 Configurations when cosFileTransfer is Used as Target</H5>
<P>The following three configuration variables can be used to configure
cosFileTransfer's SSL target behavior.
<P>
<UL>
<LI>
<STRONG>ssl_server_certfile</STRONG> which is a path to a file containing a
chain of PEM encoded certificates for cosFileTransfer as target.
</LI>
<LI>
<STRONG>ssl_server_verify</STRONG> which specifies type of verification:
0 = do not verify peer; 1 = verify peer, verify client once, 2 =
verify peer, verify client once, fail if no peer certificate.
The default value is 0.
</LI>
<LI>
<STRONG>ssl_server_depth</STRONG> which specifies verification depth, i.e.
how far in a chain of certificates the verification process shall
proceed before the verification is considered successful. The
default value is 1.
</LI>
</UL>
<P>There also exist a number of API functions for accessing the values of
these variables:
<P>
<UL>
<LI>
cosFileTransferApp:ssl_server_certfile/0
</LI>
<LI>
cosFileTransferApp:ssl_server_verify/0
</LI>
<LI>
cosFileTransferApp:ssl_server_depth/0
</LI>
</UL>
<A NAME="4.1.2.2"><!-- Empty --></A>
<H5>4.1.2.2 Configurations when cosFileTransfer is used as Source</H5>
<P>Below is the list of configuration variables used when cosFileTransfer
act as the source application.
<P>
<UL>
<LI>
<STRONG>ssl_client_certfile</STRONG> which is a path to a file containing a
chain of PEM encoded certificates used in outgoing calls.
</LI>
<LI>
<STRONG>ssl_client_verify</STRONG> which specifies type of verification:
0 = do not verify peer; 1 = verify peer, verify client once, 2 =
verify peer, verify client once, fail if no peer certificate.
The default value is 0.
</LI>
<LI>
<STRONG>ssl_client_depth</STRONG> which specifies verification depth, i.e.
how far in a chain of certificates the verification process shall
proceed before the verification is considered successful. The
default value is 1.
</LI>
</UL>
<P>There also exist a number of API functions for accessing the values of
these variables in the client processes:
<P>
<UL>
<LI>
cosFileTransferApp:ssl_client_certfile/0
</LI>
<LI>
cosFileTransferApp:ssl_client_verify/0
</LI>
<LI>
cosFileTransferApp:ssl_client_depth/0
</LI>
</UL>
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