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<html><head><title>sftpc - The Unix SafeTP Client</title></head><BODY BGCOLOR="#FFFFFF"><h1>sftpc - The Unix SafeTP Client</h1><blockquote><b>sftpc</b> is the SafeTP client for Unix. Note that a separate<a href="http://safetp.cs.berkeley.edu">Windows client</a>is available.</blockquote><h2>SYNOPSIS</h2><blockquote><pre>sftpc [ <a href="#Options">options</a> ] server [ port ]</pre></blockquote><h2>DESCRIPTION</h2><blockquote><b>sftpc</b> works similarly to the ordinary Unix FTP client, except that itcan encrypt user's passwords (and, optionally, data) when conversing with a SafeTPserver, such as <a href="sftpd.html"><b>sftpd</b></a>.<p>The server to contact must be specified on the command line. Optionally,a port may be specified; if it is not, the default of 21 is used.<p>When <b>sftpc</b> is run for the first time on a given machine by a givenuser, it will gather entropy and create ElGamal keys. During entropygathering, you may be asked to type at the keyboard; please be patient withthis process, as it is essential for key security.<p>Upon connecting to the server, <b>sftpc</b> will authenticate the server,then ask for your username and password. Once these have been acceptedby the server, you can enter <a href="#Commands">interactive commands</a>.</blockquote><!-- -------------------- options -------------------- --><a name=Options><h2>OPTIONS</h2></a><blockquote><!-- undocumented switches: -p, -s, -., -m, -n, -@ --><!-- this section duplicates information available from 'sftpc -h'; I could have used an approach similar to that used for the interactive commands, but this is a much smaller and more stable set.. --><dl><dt><b>-v</b><dd>Prints the version number for <b>sftpc</b>.<p><dt><b>-z</b><i>pbsz</i><dd>Specifies the size of the protection buffer. Note that a value that iseither too large or too small may hurt performance; the default value hasbeen experimentally determined to be a good size for most situations.<p><dt><b>-i</b><dd>Starts <b>sftpc</b> in passive mode. See <a href="#passive">passive</a>command.<p><dt><b>-d</b><dd>Print extra debugging information.<p><dt><b>-a</b><dd>Print value of ADATs (Authentication DATa) exchanged duringauthentication. Mostly for debugging.<p><dt><b>-9</b><dd>Behave as a normal (RFC 959) FTP client. This effectively disablesall encryption, including password encryption. This option is<b>not</b> recommended, unless the network connection is secured bysome alternate means.<p><dt><b>-c</b><dd>Start with data encryption off. See <a href="#prot">prot</a> command.<p><dt><b>-t</b><dd>Start with data channel in integrity-only mode. See <a href="#prot">prot</a> command.<p><dt><b>-h</b><dd>Print the help message, which provides short descriptions of thecommand-line options.<p><dt><b>-X</b><dd>Accept new server keys without prompting the user.<p><dt><b>-Q</b><dd>Automatically use the normal (insecure) FTP protocol if theserver doesn't understand the encrypted protocol.</dl></blockquote><!-- ----------------- interactive commands ------------------ --><a name=Commands><h2>INTERACTIVE COMMANDS</h2></a><blockquote><p><dl><!-- sftpc_in.html -> sftpc.html: the next line will be replaced by the output of "sftpc -@" -->insert-command-docs<!-- end of inserted docs --></dl></blockquote><!-- --------------- configuration --------------------- --><a name="configuration"><h2>CONFIGURATION</h2></a><blockquote><h3>Basic Information</h3><b>sftpc</b> must store three kinds of configuration state:<ul><li>Random seed: Necessary to generate cryptographically secure random numbers during authentication and key generation.<li>ElGamal keys: Used to encrypt the conversation.<li>Server keys: Used to authenticate servers after first contact.</ul><p>Of these, by far the most sensitive are the ElGamal keys. Inparticular, if an attacker learns the ElGamal private key, he/shecan decrypt both future <em>and</em> past sessions protected withthat key.<p>The random seed is primarily a concern just prior to key generation;an attacker that knows the seed may be able to predict the generatedkey.<p>The server keys are only a concern if an attacker modifies them; inthat case, an attacker could masquerade as a trusted server.<h3><b>sftpc</b>'s Implementation</h3><p>The above state, especially the ElGamal private key, <em>must</em>be stored on the local disk (assuming typical insecure networkssuch as NFS). Therefore <b>sftpc</b> by default stores all of thisinformation in <tt>/tmp/<i>user</i></tt>, where <i>user</i> is the usernameof the person using <b>sftpc</b>.<p>This can be inconvenient, especially on systems where <tt>/tmp</tt> isnot saved across reboot. To support alternatives, <b>sftpc</b> willstore keys in a directory specified by the SAFETP_CONFIG environmentvariable.</blockquote><h2>SEE ALSO</h2><blockquote><a href="sftpd.html">sftpd</a>,<a href="http://safetp.cs.berkeley.edu/">SafeTP</a></blockquote></body></html>⌨️ 快捷键说明
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