Re: [libvirt] [PATCH] phyp: ssh authentication with pub keys fixed

11 Nov 2009

2009/11/10 Eduardo Otubo <otubo@linux.vnet.ibm.com>:
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Eduardo Otubo wrote:
...
Matthias Bolte wrote:
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2009/11/9 Eduardo Otubo <otubo@linux.vnet.ibm.com>:
...
Matthias Bolte wrote:
...
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diff --git a/src/phyp/phyp_driver.c b/src/phyp/phyp_driver.c
index a92046a..f96d2d6 100644
--- a/src/phyp/phyp_driver.c
+++ b/src/phyp/phyp_driver.c
[...]
...
@@ -282,10 +297,8 @@ openSSHSession(virConnectPtr conn,
virConnectAuthPtr
auth,
   /* Trying authentication by pubkey */
   while ((rc =
           libssh2_userauth_publickey_fromfile(session, username,
You assign conn->uri->user to username and use it without checking for
NULL. You should either check conn->uri->user for NULL in phypOpen(),
as you do it for conn->uri->server and conn->uri->path, and return
VIR_DRV_OPEN_ERROR if its NULL or request a username via the auth
callback if conn->uri->user is NULL.
Ok.
...
...
-                                                "/home/user/"
-                                                ".ssh/id_rsa.pub",
-                                                "/home/user/"
-                                                ".ssh/id_rsa",
+                                                pubkey,
+                                                pvtkey,
                                               password)) ==
The password (actually the passphrase) is NULL at this point. Is this
really working?
Talking with libssh2 guys, this feature is not exactly working well,
they
said that it is possible to pass a random passphrase (or even NULL) that
it
will authenticate using pub and pvt keys. So, I assumed this as a
hardcoded
NULL just until they fix this function.
Hm, okay. May be you should add a comment about this.
...
...
...
          LIBSSH2_ERROR_EAGAIN) ;
   if (rc) {
So you fallback to username/password authentication if keyfile
authentication failed (rc != 0). According to the
libssh2_userauth_publickey_fromfile manpage it may return this error
codes:
LIBSSH2_ERROR_ALLOC - An internal memory allocation call failed.
LIBSSH2_ERROR_SOCKET_SEND - Unable to send data on socket.
LIBSSH2_ERROR_SOCKET_TIMEOUT
LIBSSH2_ERROR_PUBLICKEY_UNRECOGNIZED - The username/public key
combination was invalid.
LIBSSH2_ERROR_PUBLICKEY_UNVERIFIED - The username/public key
combination was invalid, or the signature for the supplied public key
was invalid.
Appearently, going further the man pages and tracing all the function
return
points, I figured out that this function may also return
LIBSSH2_ERROR_SOCKET_NONE or LIBSSH2_ERROR_NONE for many reasons. As far
as
I understand, LIBSSH2_ERROR_NONE is for a succesful pubkey
authentication,
and LIBSSH2_ERROR_SOCKET_NONE is for a non succesful. Adjusted all
values
for this if construction.
...
IMHO its not useful to fallback to username/password authentication
for the first three possible errors, only if a keyfile related error
occurs like the last two.
In this case I explicit check for errors (LIBSSH2_ERROR_ALLOC,
LIBSSH2_ERROR_SOCKET_SEND and LIBSSH2_ERROR_SOCKET_TIMEOUT) before
fallback.
...
I wonder which error code will be returned if one or both keyfiles
don't exist. Maybe you should check if both keyfiles exist before
calling libssh2_userauth_publickey_fromfile() and fallback to
username/password authentication if one or both are missing.
Ok. I am stating files now.
...
...
@@ -341,15 +354,22 @@ openSSHSession(virConnectPtr conn,
virConnectAuthPtr auth,
           goto disconnect;
       } else
           goto exit;
+    } else {
+        goto exit;
   }
 disconnect:
   libssh2_session_disconnect(session, "Disconnecting...");
   libssh2_session_free(session);
 err:
+    VIR_FREE(userhome);
+    VIR_FREE(pubkey);
+    VIR_FREE(pvtkey);
   VIR_FREE(password);
   return NULL;
 exit:
+    VIR_FREE(userhome);
VIR_FREE(pubkey) is missing here, it's there in the first version of
this
patch.
Ok.
Thanks again :)
[]'s
...
diff --git a/src/phyp/phyp_driver.c b/src/phyp/phyp_driver.c
index a92046a..94581b2 100644
--- a/src/phyp/phyp_driver.c
+++ b/src/phyp/phyp_driver.c
[...]
...
@@ -280,15 +302,19 @@ openSSHSession(virConnectPtr conn,
virConnectAuthPtr auth,
    }
    /* Trying authentication by pubkey */
+    if (stat(pvtkey, &pvt_stat) || stat(pubkey, &pub_stat))
You could have used access(pvtkey, R_OK) instead, but stat() is okay.
Don't you want to try username/password authentication in case of
missing keyfiles? Instead you goto err.
...
+        goto err;
+
    while ((rc =
            libssh2_userauth_publickey_fromfile(session, username,
-                                                "/home/user/"
-                                                ".ssh/id_rsa.pub",
-                                                "/home/user/"
-                                                ".ssh/id_rsa",
-                                                password)) ==
+                                                pubkey,
+                                                pvtkey,
+                                                NULL)) ==
           LIBSSH2_ERROR_EAGAIN) ;
-    if (rc) {
+
+    if (rc == LIBSSH2_ERROR_NONE
Didn't you say LIBSSH2_ERROR_NONE would be returned in case of
successful authentication? I think you wanted to check for
LIBSSH2_ERROR_SOCKET_NONE here, didn't you?
...
+        || rc == LIBSSH2_ERROR_PUBLICKEY_UNRECOGNIZED
+        || rc == LIBSSH2_ERROR_PUBLICKEY_UNVERIFIED) {
        int i;
        int hasPassphrase = 0;
Keep it up, you'll get this patch right :-)
Matthias
Hope this is the last patch I send on this topic! :)
All fixed.
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Actually, I can't do that construction. Using the label and the goto that
way. I just put the label right above the if statement and set the rc to
fallback to keyboard interactive (in case of files not found).
[]'s
Okay, I've applied the difference between this patch and the last patch.

Matthias

    