s4-auth Supply more useful error messages on Kerberos failure

The practice of returning only NT_STATUS_INVALID_PARAMETER hasn't
helped our users to debug problems effectivly, and so we now return
more errors and try and give a more useful debug message when then
happen.

Andrew Bartlett

3 files changed, 28 insertions, 13 deletions

diff --git a/source4/auth/gensec/gensec_gssapi.c b/source4/auth/gensec/gensec_gssapi.c
index 3c579fee50..a03cf9edd7 100644
--- a/source4/auth/gensec/gensec_gssapi.c
+++ b/source4/auth/gensec/gensec_gssapi.c
@@ -315,7 +315,6 @@ static NTSTATUS gensec_gssapi_client_start(struct gensec_security *gensec_securi
 	gss_OID name_type;
 	OM_uint32 maj_stat, min_stat;
 	const char *hostname = gensec_get_target_hostname(gensec_security);
-	const char *principal;
 	struct gssapi_creds_container *gcc;
 	const char *error_string;
 
@@ -339,18 +338,18 @@ static NTSTATUS gensec_gssapi_client_start(struct gensec_security *gensec_securi
 
 	gensec_gssapi_state = talloc_get_type(gensec_security->private_data, struct gensec_gssapi_state);
 
-	principal = gensec_get_target_principal(gensec_security);
-	if (principal) {
+	gensec_gssapi_state->target_principal = gensec_get_target_principal(gensec_security);
+	if (gensec_gssapi_state->target_principal) {
 		name_type = GSS_C_NULL_OID;
 	} else {
-		principal = talloc_asprintf(gensec_gssapi_state, "%s/%s@%s",
+		gensec_gssapi_state->target_principal = talloc_asprintf(gensec_gssapi_state, "%s/%s@%s",
 					    gensec_get_target_service(gensec_security), 
 					    hostname, lpcfg_realm(gensec_security->settings->lp_ctx));
 
 		name_type = GSS_C_NT_USER_NAME;
 	}
-	name_token.value  = discard_const_p(uint8_t, principal);
-	name_token.length = strlen(principal);
+	name_token.value  = discard_const_p(uint8_t, gensec_gssapi_state->target_principal);
+	name_token.length = strlen(gensec_gssapi_state->target_principal);
 
 
 	maj_stat = gss_import_name (&min_stat,
@@ -373,12 +372,12 @@ static NTSTATUS gensec_gssapi_client_start(struct gensec_security *gensec_securi
 	case KRB5KDC_ERR_PREAUTH_FAILED:
 		return NT_STATUS_LOGON_FAILURE;
 	case KRB5_KDC_UNREACH:
-		DEBUG(3, ("Cannot reach a KDC we require to contact %s : %s\n", principal, error_string));
-		return NT_STATUS_INVALID_PARAMETER; /* Make SPNEGO ignore us, we can't go any further here */
+		DEBUG(3, ("Cannot reach a KDC we require to contact %s : %s\n", gensec_gssapi_state->target_principal, error_string));
+		return NT_STATUS_NO_LOGON_SERVERS;
 	case KRB5_CC_NOTFOUND:
 	case KRB5_CC_END:
-		DEBUG(3, ("Error preparing credentials we require to contact %s : %s\n", principal, error_string));
-		return NT_STATUS_INVALID_PARAMETER; /* Make SPNEGO ignore us, we can't go any further here */
+		DEBUG(2, ("Error obtaining ticket we require to contact %s: (possibly due to clock skew between us and the KDC) %s\n", gensec_gssapi_state->target_principal, error_string));
+		return NT_STATUS_TIME_DIFFERENCE_AT_DC;
 	default:
 		DEBUG(1, ("Aquiring initiator credentials failed: %s\n", error_string));
 		return NT_STATUS_UNSUCCESSFUL;
@@ -569,12 +568,24 @@ static NTSTATUS gensec_gssapi_update(struct gensec_security *gensec_security,
 			return NT_STATUS_MORE_PROCESSING_REQUIRED;
 		} else if (gss_oid_equal(gensec_gssapi_state->gss_oid, gss_mech_krb5)) {
 			switch (min_stat) {
+			case KRB5KRB_AP_ERR_TKT_NYV:
+				DEBUG(1, ("Error with ticket to contact %s: possible clock skew between us and the KDC or target server: %s\n",
+					  gensec_gssapi_state->target_principal,
+					  gssapi_error_string(out_mem_ctx, maj_stat, min_stat, gensec_gssapi_state->gss_oid)));
+				return NT_STATUS_TIME_DIFFERENCE_AT_DC; /* Make SPNEGO ignore us, we can't go any further here */
+			case KRB5KRB_AP_ERR_TKT_EXPIRED:
+				DEBUG(1, ("Error with ticket to contact %s: ticket is expired, possible clock skew between us and the KDC or target server: %s\n",
+					  gensec_gssapi_state->target_principal,
+					  gssapi_error_string(out_mem_ctx, maj_stat, min_stat, gensec_gssapi_state->gss_oid)));
+				return NT_STATUS_INVALID_PARAMETER; /* Make SPNEGO ignore us, we can't go any further here */
 			case KRB5_KDC_UNREACH:
-				DEBUG(3, ("Cannot reach a KDC we require: %s\n",
+				DEBUG(3, ("Cannot reach a KDC we require in order to obtain a ticetk to %s: %s\n",
+					  gensec_gssapi_state->target_principal,
 					  gssapi_error_string(gensec_gssapi_state, maj_stat, min_stat, gensec_gssapi_state->gss_oid)));
-				return NT_STATUS_INVALID_PARAMETER; /* Make SPNEGO ignore us, we can't go any further here */
+				return NT_STATUS_NO_LOGON_SERVERS; /* Make SPNEGO ignore us, we can't go any further here */
 			case KRB5KDC_ERR_S_PRINCIPAL_UNKNOWN:
-				DEBUG(3, ("Server is not registered with our KDC: %s\n", 
+				DEBUG(3, ("Server %s is not registered with our KDC: %s\n",
+					  gensec_gssapi_state->target_principal,
 					  gssapi_error_string(gensec_gssapi_state, maj_stat, min_stat, gensec_gssapi_state->gss_oid)));
 				return NT_STATUS_INVALID_PARAMETER; /* Make SPNEGO ignore us, we can't go any further here */
 			case KRB5KRB_AP_ERR_MSG_TYPE:
diff --git a/source4/auth/gensec/gensec_gssapi.h b/source4/auth/gensec/gensec_gssapi.h
index b55b4391e0..1b826b963d 100644
--- a/source4/auth/gensec/gensec_gssapi.h
+++ b/source4/auth/gensec/gensec_gssapi.h
@@ -64,5 +64,7 @@ struct gensec_gssapi_state {
 	size_t max_wrap_buf_size;
 	int gss_exchange_count;
 	size_t sig_size;
+
+	const char *target_principal;
 };
 
diff --git a/source4/auth/gensec/spnego.c b/source4/auth/gensec/spnego.c
index 4902cd8ee1..813bf0a730 100644
--- a/source4/auth/gensec/spnego.c
+++ b/source4/auth/gensec/spnego.c
@@ -495,6 +495,8 @@ static NTSTATUS gensec_spnego_parse_negTokenInit(struct gensec_security *gensec_
 			 * of this mech */
 			if (spnego_state->state_position != SPNEGO_SERVER_START) {
 				if (NT_STATUS_EQUAL(nt_status, NT_STATUS_INVALID_PARAMETER) || 
+				    NT_STATUS_EQUAL(nt_status, NT_STATUS_NO_LOGON_SERVERS) ||
+				    NT_STATUS_EQUAL(nt_status, NT_STATUS_TIME_DIFFERENCE_AT_DC) ||
 				    NT_STATUS_EQUAL(nt_status, NT_STATUS_CANT_ACCESS_DOMAIN_INFO)) {
 					/* Pretend we never started it (lets the first run find some incompatible demand) */