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Add documentation of the new PSCP `-unsafe' option and the

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associated warning message.

[originally from svn r1221]
This commit is contained in:
Simon Tatham 2001-08-28 09:53:51 +00:00
parent d1d2fd7a13
commit bbc7f197bc
1 changed files with 52 additions and 4 deletions
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doc/pscp.but
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@ -1,12 +1,9 @@
\versionid $Id: pscp.but,v 1.12 2001/07/01 09:21:01 simon Exp $
\versionid $Id: pscp.but,v 1.13 2001/08/28 09:53:51 simon Exp $
\#FIXME: Need examples
\C{pscp} Using PSCP to transfer files securely
\# Explain PSCP: the command line, the modes of use (local->remote
\# and remote->local, recursive, wildcards).
\i{PSCP}, the PuTTY Secure Copy client, is a tool for transferring files
securely between computers using an SSH connection.
@ -76,6 +73,48 @@ server \c{example.com} as user \c{fred} to the file
\c pscp c:\documents\csh-whynot.txt fred@example.com:/tmp/csh-whynot
You can use wildcards to transfer multiple files in either
direction, like this:
\c pscp c:\documents\*.doc fred@example.com:docfiles
\c pscp fred@example.com:source/*.c c:\source
However, in the second case (using a wildcard for multiple remote
files) you may see a warning like this:
\c warning: remote host tried to write to a file called 'terminal.c'
\c when we requested a file called '*.c'.
\c If this is a wildcard, consider upgrading to SSH 2 or using
\c the '-unsafe' option. Renaming of this file has been disallowed.
This is due to a fundamental insecurity in the old-style SCP
protocol: the client sends the wildcard string (\c{*.c}) to the
server, and the server sends back a sequence of file names that
match the wildcard pattern. However, there is nothing to stop the
server sending back a \e{different} pattern and writing over one of
your other files: if you request \c{*.c}, the server might send back
the file name \c{AUTOEXEC.BAT} and install a virus for you. Since
the wildcard matching rules are decided by the server, the client
cannot reliably verify that the filenames sent back match the
pattern.
PSCP will attempt to use the newer SFTP protocol (part of SSH 2)
where possible, which does not suffer from this security flaw. If
you are talking to an SSH 2 server which supports SFTP, you will
never see this warning.
If you really need to use a server-side wildcard with an SSH 1
server, you can use the \c{-unsafe} command line option with PSCP:
\c pscp -unsafe fred@example.com:source/*.c c:\source
This will suppress the warning message and the file transfer will
happen. However, you should be aware that by using this option you
are giving the server the ability to write to \e{any} file in the
target directory, so you should only use this option if you trust
the server administrator not to be malicious (and not to let the
server machine be cracked by malicious people).
\S2{pscp-usage-basics-user} \c{user}
The login name on the remote server. If this is omitted, and \c{host}
@ -187,6 +226,15 @@ Since specifying passwords in scripts is a bad idea for security
reasons, you might want instead to consider using public-key
authentication; see \k{pscp-pubkey}.
\S{pscp-pubkey} Return value
PSCP returns an \cw{ERRORLEVEL} of zero (success) only if the files
were correctly transferred. You can test for this in a batch file,
using code such as this:
\c pscp file*.* user@hostname:
\c if errorlevel 1 echo There was an error
\S{pscp-pubkey} Using public key authentication with PSCP
Like PuTTY, PSCP can authenticate using a public key instead of a