[libvirt] Some questions about virConnectAuthCallbackPtr
Some questions which seem to be left ambigious by the documentation for virConnectAuthCallbackPtr: http://libvirt.org/html/libvirt-libvirt.html#virConnectAuthCallbackPtr (1) For a single open, can this be called multiple times? I'm thinking, some authentication methods might give the user N attempts at typing the password, which might result in N callbacks here. (2) The documentation says: "Returns: 0 if all interactions were filled, or -1 upon error". However it also says "If an interaction cannot be filled, fill in NULL and 0". Does that mean it's OK (not an error, return 0) if a result field is set to NULL? Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones virt-top is 'top' for virtual machines. Tiny program with many powerful monitoring features, net stats, disk stats, logging, etc. http://et.redhat.com/~rjones/virt-top
Another comment about virConnectOpenAuth: Is it possible to test uses of this API from scripts? It'd be nice if the test driver allowed you to test authentication, but I notice in the source that all uses of virConnectAuthPtr are marked ATTRIBUTE_UNUSED, so I guess that's not a possible route. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones New in Fedora 11: Fedora Windows cross-compiler. Compile Windows programs, test, and build Windows installers. Over 70 libraries supprt'd http://fedoraproject.org/wiki/MinGW http://www.annexia.org/fedora_mingw
On Sat, Oct 13, 2012 at 04:02:56PM +0100, Richard W.M. Jones wrote:
Another comment about virConnectOpenAuth:
Is it possible to test uses of this API from scripts? It'd be nice if the test driver allowed you to test authentication, but I notice in the source that all uses of virConnectAuthPtr are marked ATTRIBUTE_UNUSED, so I guess that's not a possible route.
Hmm, yes, that's a bit sucky. The test driver ought to be enhanced to allow testing of this. Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
On Sat, Oct 13, 2012 at 03:52:06PM +0100, Richard W.M. Jones wrote:
Some questions which seem to be left ambigious by the documentation for virConnectAuthCallbackPtr:
http://libvirt.org/html/libvirt-libvirt.html#virConnectAuthCallbackPtr
(1) For a single open, can this be called multiple times? I'm thinking, some authentication methods might give the user N attempts at typing the password, which might result in N callbacks here.
Testing and reviewing the libssh2 backend, it seems this must be true (ie. N >= 1). BTW I cannot get the libssh2 backend in libvirt to work. For every host it says: libvirt_auth.c: authentication required for libvirt URI 'qemu+libssh2://localhost/system' libvirt_auth.c: credential 'echoprompt' Accept SSH host key with hash '<correct host key>' for host 'localhost:22' (y/n)?: y libguestfs: error: could not connect to libvirt (code 85, domain 50): SSH transport error: SSH host key for 'localhost' (<correct host key>) was not accepted No idea what I'm doing wrong. Nothing in the logs on the server indicate that anything is wrong on the remote side. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones virt-p2v converts physical machines to virtual machines. Boot with a live CD or over the network (PXE) and turn machines into Xen guests. http://et.redhat.com/~rjones/virt-p2v
On Sat, Oct 13, 2012 at 05:47:24PM +0100, Richard W.M. Jones wrote:
BTW I cannot get the libssh2 backend in libvirt to work. For every host it says:
libvirt_auth.c: authentication required for libvirt URI 'qemu+libssh2://localhost/system' libvirt_auth.c: credential 'echoprompt' Accept SSH host key with hash '<correct host key>' for host 'localhost:22' (y/n)?: y libguestfs: error: could not connect to libvirt (code 85, domain 50): SSH transport error: SSH host key for 'localhost' (<correct host key>) was not accepted
No idea what I'm doing wrong. Nothing in the logs on the server indicate that anything is wrong on the remote side.
Peter, This is because of a bug in the libvirt code: if (!askKey.result || STRCASENEQ(askKey.result, "y")) { virReportError(VIR_ERR_SSH, _("SSH host key for '%s' (%s) was not accepted"), sess->hostname, keyhash); VIR_FREE(keyhash); VIR_FREE(askKey.result); return -1; } The problem with this code is that it ignores the resultlen field. If the caller passes result[] = { 'y' } (no trailing \0), resultlen = 1, (which IMHO is a correct use of the API as described by the documentation), then STRCASENEQ above will not match the string. You need to use something like: askKey.resultlen >= 1 && askKey.result[0] == 'y' or else some sort of memcmp function. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming blog: http://rwmj.wordpress.com Fedora now supports 80 OCaml packages (the OPEN alternative to F#) http://cocan.org/getting_started_with_ocaml_on_red_hat_and_fedora
On 10/13/12 19:08, Richard W.M. Jones wrote:
On Sat, Oct 13, 2012 at 05:47:24PM +0100, Richard W.M. Jones wrote:
BTW I cannot get the libssh2 backend in libvirt to work. For every host it says:
libvirt_auth.c: authentication required for libvirt URI 'qemu+libssh2://localhost/system' libvirt_auth.c: credential 'echoprompt' Accept SSH host key with hash '<correct host key>' for host 'localhost:22' (y/n)?: y libguestfs: error: could not connect to libvirt (code 85, domain 50): SSH transport error: SSH host key for 'localhost' (<correct host key>) was not accepted
No idea what I'm doing wrong. Nothing in the logs on the server indicate that anything is wrong on the remote side.
Peter,
This is because of a bug in the libvirt code:
if (!askKey.result || STRCASENEQ(askKey.result, "y")) { virReportError(VIR_ERR_SSH, _("SSH host key for '%s' (%s) was not accepted"), sess->hostname, keyhash); VIR_FREE(keyhash); VIR_FREE(askKey.result); return -1; }
The problem with this code is that it ignores the resultlen field.
If the caller passes result[] = { 'y' } (no trailing \0), resultlen = 1, (which IMHO is a correct use of the API as described by the documentation), then STRCASENEQ above will not match the string.
You need to use something like:
askKey.resultlen >= 1 && askKey.result[0] == 'y'
or else some sort of memcmp function.
Rich.
Hm, that seems to be a fair point. I'll have a look and try to fix this today. Peter
On Mon, Oct 15, 2012 at 12:17:42PM +0200, Peter Krempa wrote:
On 10/13/12 19:08, Richard W.M. Jones wrote:
On Sat, Oct 13, 2012 at 05:47:24PM +0100, Richard W.M. Jones wrote:
BTW I cannot get the libssh2 backend in libvirt to work. For every host it says:
libvirt_auth.c: authentication required for libvirt URI 'qemu+libssh2://localhost/system' libvirt_auth.c: credential 'echoprompt' Accept SSH host key with hash '<correct host key>' for host 'localhost:22' (y/n)?: y libguestfs: error: could not connect to libvirt (code 85, domain 50): SSH transport error: SSH host key for 'localhost' (<correct host key>) was not accepted
No idea what I'm doing wrong. Nothing in the logs on the server indicate that anything is wrong on the remote side.
Peter,
This is because of a bug in the libvirt code:
if (!askKey.result || STRCASENEQ(askKey.result, "y")) { virReportError(VIR_ERR_SSH, _("SSH host key for '%s' (%s) was not accepted"), sess->hostname, keyhash); VIR_FREE(keyhash); VIR_FREE(askKey.result); return -1; }
The problem with this code is that it ignores the resultlen field.
If the caller passes result[] = { 'y' } (no trailing \0), resultlen = 1, (which IMHO is a correct use of the API as described by the documentation), then STRCASENEQ above will not match the string.
You need to use something like:
askKey.resultlen >= 1 && askKey.result[0] == 'y'
or else some sort of memcmp function.
Rich.
Hm, that seems to be a fair point. I'll have a look and try to fix this today.
And FWIW this case would fail (badly) too: result[] = { 'y', ... }; // ie. some random data resultlen = 0 Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones virt-p2v converts physical machines to virtual machines. Boot with a live CD or over the network (PXE) and turn machines into Xen guests. http://et.redhat.com/~rjones/virt-p2v
On Sat, Oct 13, 2012 at 06:08:42PM +0100, Richard W.M. Jones wrote:
On Sat, Oct 13, 2012 at 05:47:24PM +0100, Richard W.M. Jones wrote:
BTW I cannot get the libssh2 backend in libvirt to work. For every host it says:
libvirt_auth.c: authentication required for libvirt URI 'qemu+libssh2://localhost/system' libvirt_auth.c: credential 'echoprompt' Accept SSH host key with hash '<correct host key>' for host 'localhost:22' (y/n)?: y libguestfs: error: could not connect to libvirt (code 85, domain 50): SSH transport error: SSH host key for 'localhost' (<correct host key>) was not accepted
No idea what I'm doing wrong. Nothing in the logs on the server indicate that anything is wrong on the remote side.
Peter,
This is because of a bug in the libvirt code:
if (!askKey.result || STRCASENEQ(askKey.result, "y")) { virReportError(VIR_ERR_SSH, _("SSH host key for '%s' (%s) was not accepted"), sess->hostname, keyhash); VIR_FREE(keyhash); VIR_FREE(askKey.result); return -1; }
The problem with this code is that it ignores the resultlen field.
If the caller passes result[] = { 'y' } (no trailing \0), resultlen = 1, (which IMHO is a correct use of the API as described by the documentation), then STRCASENEQ above will not match the string.
You need to use something like:
askKey.resultlen >= 1 && askKey.result[0] == 'y'
or else some sort of memcmp function.
We probably ought to clarify the docs that any strings should be NULL terminated, and that the resultlen does not include the NULL terminator in its count. Most of the auth code looks to assume that the returned data is NULL terminated. Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
On Mon, Oct 15, 2012 at 11:17:55AM +0100, Daniel P. Berrange wrote:
On Sat, Oct 13, 2012 at 06:08:42PM +0100, Richard W.M. Jones wrote:
On Sat, Oct 13, 2012 at 05:47:24PM +0100, Richard W.M. Jones wrote:
BTW I cannot get the libssh2 backend in libvirt to work. For every host it says:
libvirt_auth.c: authentication required for libvirt URI 'qemu+libssh2://localhost/system' libvirt_auth.c: credential 'echoprompt' Accept SSH host key with hash '<correct host key>' for host 'localhost:22' (y/n)?: y libguestfs: error: could not connect to libvirt (code 85, domain 50): SSH transport error: SSH host key for 'localhost' (<correct host key>) was not accepted
No idea what I'm doing wrong. Nothing in the logs on the server indicate that anything is wrong on the remote side.
Peter,
This is because of a bug in the libvirt code:
if (!askKey.result || STRCASENEQ(askKey.result, "y")) { virReportError(VIR_ERR_SSH, _("SSH host key for '%s' (%s) was not accepted"), sess->hostname, keyhash); VIR_FREE(keyhash); VIR_FREE(askKey.result); return -1; }
The problem with this code is that it ignores the resultlen field.
If the caller passes result[] = { 'y' } (no trailing \0), resultlen = 1, (which IMHO is a correct use of the API as described by the documentation), then STRCASENEQ above will not match the string.
You need to use something like:
askKey.resultlen >= 1 && askKey.result[0] == 'y'
or else some sort of memcmp function.
We probably ought to clarify the docs that any strings should be NULL terminated, and that the resultlen does not include the NULL terminator in its count. Most of the auth code looks to assume that the returned data is NULL terminated.
Indeed I changed libguestfs to pass strings which are NUL-terminated (not NULL!) with the \0 termination not included in the result count. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://et.redhat.com/~rjones/virt-df/
On Sat, Oct 13, 2012 at 03:52:06PM +0100, Richard W.M. Jones wrote:
Some questions which seem to be left ambigious by the documentation for virConnectAuthCallbackPtr:
http://libvirt.org/html/libvirt-libvirt.html#virConnectAuthCallbackPtr
(1) For a single open, can this be called multiple times? I'm thinking, some authentication methods might give the user N attempts at typing the password, which might result in N callbacks here.
It depends on the driver and auth mechanism, but yes, the callback can be invoked multiple times. The remote driver tries to ask for as many credentials at the same time as possible, but SASL allows for triggering the auth callback multiuple during the auth process. The ESX driver will actually ask for credentials separately IIRC.
(2) The documentation says: "Returns: 0 if all interactions were filled, or -1 upon error". However it also says "If an interaction cannot be filled, fill in NULL and 0". Does that mean it's OK (not an error, return 0) if a result field is set to NULL?
Correct, filling in NULL and 0 is an allowed non-error condition, to indicate that the user didn't have any data to provide for that field. Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
participants (3)
-
Daniel P. Berrange -
Peter Krempa -
Richard W.M. Jones