With some authentication mechanism (PLAIN for example), sasl_client_start() can return SASL_OK, which translates to virNetSASLSessionClientStart() returning VIR_NET_SASL_COMPLETE. cyrus-sasl documentation is a bit vague as to what to do in such situation, but upstream clarified this a bit in http://asg.andrew.cmu.edu/archive/message.php?mailbox=archive.cyrus-sasl&... When we got VIR_NET_SASL_COMPLETE after virNetSASLSessionClientStart() and if the remote also tells us that authentication is complete, then we should end the authentication procedure rather than forcing a call to virNetSASLSessionClientStep(). Without this patch, when trying to use SASL PLAIN, I get: error :authentication failed : Failed to step SASL negotiation: -1 (SASL(-1): generic failure: Unable to find a callback: 32775) This patch is based on a spice-gtk patch by Dietmar Maurer. --- Changes since v1: - adjust comment before the for(;;) code block - add comment before the if (complete && ...) test as this is what is done for these tests in this block. src/remote/remote_driver.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/src/remote/remote_driver.c b/src/remote/remote_driver.c index 7181949..38da119 100644 --- a/src/remote/remote_driver.c +++ b/src/remote/remote_driver.c @@ -4122,9 +4122,16 @@ remoteAuthSASL(virConnectPtr conn, struct private_data *priv, complete, serverinlen, serverin); /* Loop-the-loop... - * Even if the server has completed, the client must *always* do at least one step - * in this loop to verify the server isn't lying about something. Mutual auth */ + * Even if the server has completed, the client must loop until sasl_client_start() or + * sasl_client_step() return SASL_OK to verify the server isn't lying + * about something. Mutual auth + * */ for (;;) { + /* Previous server call showed completion & sasl_client_start() + * told us we are locally complete too */ + if (complete && err == VIR_NET_SASL_COMPLETE) + break; + restep: if ((err = virNetSASLSessionClientStep(sasl, serverin, -- 1.8.4.2