The PrivateKey property is used when you want to
authenticate with the server using a private/public key
pair, instead of using a Password. This is a
feature that should be supported by all SFTP servers.
The principal behind the use of private keys is this: you own a private key (which no one else knows). You supply the
server with the public key that
corresponds to your private key.
When you initiate a connection, wodSFTP will request publickey
authentication. The server will check its internal list of
public keys (usually stored in ~/.ssh/authorized_keys2 or ~/.ssh2/authorized files) and, if a match is found,
it will send a request to wodSFTP to prove that you own the
private key. Internally, wodSFTP
will sign some data using the key you provided, and the server will
check the signatures. If they match, you will be allowed to
login. Some servers will also require you to enter a
password, in which case the server is even more
secure.
To generate a PrivateKey that you can use with the server, use the
Keys object (included in setup package) like this (VB
sample):
Dim key As New
wodSFTPKeyLib.Keys
key.Generate RSAkey ' 1024 bits is
default
key.Save RSAkey, "C:\my_rsa_key.txt", "My secret password"
The above sample will generate your private key and store it
to file on disk, protected with a password. You
can then immediately continue your code like this:
Sftp.Login = "johndoe"
Sftp.PrivateKey = key.PrivateKey(RSAkey)
Sftp.Authentication = authPubkey
.......
Sftp.Connect
As generation of keys can be a lengthy process (for
keys with a large number of bits it can take few seconds), you
shouldn't generate it every time you need to use it.
Instead, as you have saved it, you should try to load it from
the disk. The following code illustrates this type of usage:
Dim key As New
wodSFTPKeyLib.Keys
On Error
Resume Next
' try to load previously saved
key
key.Load "C:\my_rsa_key.txt", "My secret password"
If Err <> 0 Then 'key was not saved
yet
key.Generate
RSAkey ' 1024 bits is
default
key.Save
RSAkey, "C:\my_rsa_key.txt", "My secret password"
' next time you run this code it
will be able to load it from the disk,
' so expensive Generate will not be
called anymore.
End If
Now that you have created your PrivateKey, you should
let the server know about it. You should do this by pasting the
public key into the appropriate files
on the server. For SFTP servers (version 2), these are
~/.ssh2/authorization which
should have the line of text Key
somefile.pub on a separate line in the file,
~/.ssh2/somefile.pub which should
contain your public key, as returned by the Keys.PublicKeySSH property.
For OpenSSH server, you should paste the contents of
Keys.PublicKeyOpenSSH property into
~/.ssh/authorized_keys2 as a new
line in the file.
For VC users, you can prepare a returned key (loaded from
file, for example) by converting it to SAFEARRAY like
this:
(Buffer holds key data, and Bufsize holds key len)
SAFEARRAY *psa;
SAFEARRAYBOUND rgsabound[1];
char HUGEP *data;
rgsabound[0].lLbound=0;
rgsabound[0].cElements=Bufsize;
psa =
SafeArrayCreate(VT_UI1,1,rgsabound);
if (!psa)
return WSA_NOT_ENOUGH_MEMORY;
SafeArrayAccessData(psa, (void HUGEP*
FAR*)&data);
memcpy(data,Buffer, Bufsize);
SafeArrayUnaccessData(psa);
VARIANT var;
var.vt =VT_ARRAY | VT_UI1;
var.parray=psa;
and now you can pass this VARIANT into the PrivateKey
property or you can pass LPDISPATCH from the IKeys object
directly in the same manner:
VARIANT var;
var.vt = VT_DISPATCH;
var.pdispVal = (LPDISPATCH)your_keys_object_instance
and it will work too.
The Bufsize variable should contain the maximum data length
that can be stored in the Buffer variable. If you set Bufsize =
0, then the function will return with error
ERROR_INSUFFICIENT_BUFFER and Bufsize will contain the required
buffer size.
