[RFC] fix bug 12007 (libads and kinit only as fallback)

[Uri Simchoni]

On 07/06/2016 02:15 PM, Stefan Metzmacher wrote:
>> As a short term fix we may use a similar the logic in libads as in libsmb.
>>
>> The attached patches may need more work.
>>
I'm for the approach of those patches as a short term fix (and let's not
forget - a fix for stable versions).

I've tested and made slight modifications to your patch - beside build
issues the original patch broke "net ads join -Uuser%password", because
the kinit was populating a different ccache - the one pointed to by
ads->auth.ccache_name (yeah, what a mess...).

Please review and push if happy.

Thanks,
Uri.

-------------- next part --------------
From 6d5cd96d39b79d0054b923a2a5aea1dddce9d8d6 Mon Sep 17 00:00:00 2001
From: Stefan Metzmacher <metze at samba.org>
Date: Wed, 6 Jul 2016 12:48:11 +0200
Subject: [PATCH 1/2] libads: ensure the right ccache is used during gssapi
 bind

When doing gssapi sasl bind:
1. Try working without kinit only if a password is not
   provided
2. When using kinit, ensure the KRB5CCNAME env var is set
   to a private memory ccache, so that the bind is on behalf
   of the requested user.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12007

Signed-off-by: Stefan Metzmacher <metze at samba.org>
Reviewed-by: Uri Simchoni <uri at samba.org>
---
 source3/libads/sasl.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/source3/libads/sasl.c b/source3/libads/sasl.c
index d76d872..6c054cd 100644
--- a/source3/libads/sasl.c
+++ b/source3/libads/sasl.c
@@ -26,6 +26,7 @@
 #include "smb_krb5.h"
 #include "system/gssapi.h"
 #include "lib/param/loadparm.h"
+#include "krb5_env.h"
 
 #ifdef HAVE_LDAP
 
@@ -1015,21 +1016,29 @@ static ADS_STATUS ads_sasl_gssapi_bind(ADS_STRUCT *ads)
 {
 	ADS_STATUS status;
 	struct ads_service_principal p;
+	const char *ccache_name = "MEMORY:ads_sasl_gssapi_do_bind";
 
 	status = ads_generate_service_principal(ads, &p);
 	if (!ADS_ERR_OK(status)) {
 		return status;
 	}
 
-	status = ads_sasl_gssapi_do_bind(ads, p.name);
-	if (ADS_ERR_OK(status)) {
-		ads_free_service_principal(&p);
-		return status;
-	}
+	if (ads->auth.password == NULL ||
+	    ads->auth.password[0] == '\0') {
+		status = ads_sasl_gssapi_do_bind(ads, p.name);
+		if (ADS_ERR_OK(status)) {
+			ads_free_service_principal(&p);
+			return status;
+		}
 
-	DEBUG(10,("ads_sasl_gssapi_do_bind failed with: %s, "
-		  "calling kinit\n", ads_errstr(status)));
+		DEBUG(10,("ads_sasl_gssapi_do_bind failed with: %s, "
+			  "calling kinit\n", ads_errstr(status)));
+	}
 
+	if (ads->auth.ccache_name != NULL) {
+		ccache_name = ads->auth.ccache_name;
+	}
+	setenv(KRB5_ENV_CCNAME, ccache_name, 1);
 	status = ADS_ERROR_KRB5(ads_kinit_password(ads));
 
 	if (ADS_ERR_OK(status)) {
-- 
2.5.5


From 4ad9af428885b5c1b45de386b8f5899439b68ef2 Mon Sep 17 00:00:00 2001
From: Stefan Metzmacher <metze at samba.org>
Date: Wed, 6 Jul 2016 12:44:11 +0200
Subject: [PATCH 2/2] libads: ensure the right ccache is used during spnego
 bind

When doing spnego sasl bind:
1. Try working without kinit only if a password is not
   provided
2. When using kinit, ensure the KRB5CCNAME env var is set
   to a private memory ccache, so that the bind is on behalf
   of the requested user.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12007

Signed-off-by: Stefan Metzmacher <metze at samba.org>
Reviewed-by: Uri Simchoni <uri at samba.org>
---
 source3/libads/sasl.c | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/source3/libads/sasl.c b/source3/libads/sasl.c
index 6c054cd..85a2eb0 100644
--- a/source3/libads/sasl.c
+++ b/source3/libads/sasl.c
@@ -749,18 +749,29 @@ static ADS_STATUS ads_sasl_spnego_bind(ADS_STRUCT *ads)
 	if (!(ads->auth.flags & ADS_AUTH_DISABLE_KERBEROS) &&
 	    got_kerberos_mechanism) 
 	{
-		status = ads_sasl_spnego_gensec_bind(ads, "GSS-SPNEGO",
-						     CRED_MUST_USE_KERBEROS,
-						     p.service, p.hostname,
-						     blob);
-		if (ADS_ERR_OK(status)) {
-			ads_free_service_principal(&p);
-			goto done;
+		const char *ccache_name = "MEMORY:ads_sasl_spnego_bind";
+		if (ads->auth.ccache_name != NULL) {
+			ccache_name = ads->auth.ccache_name;
 		}
 
-		DEBUG(10,("ads_sasl_spnego_gensec_bind(KRB5) failed with: %s, "
-			  "calling kinit\n", ads_errstr(status)));
+		if (ads->auth.password == NULL ||
+		    ads->auth.password[0] == '\0')
+		{
+
+			status = ads_sasl_spnego_gensec_bind(ads, "GSS-SPNEGO",
+							     CRED_MUST_USE_KERBEROS,
+							     p.service, p.hostname,
+							     blob);
+			if (ADS_ERR_OK(status)) {
+				ads_free_service_principal(&p);
+				goto done;
+			}
+
+			DEBUG(10,("ads_sasl_spnego_gensec_bind(KRB5) failed with: %s, "
+				  "calling kinit\n", ads_errstr(status)));
+		}
 
+		setenv(KRB5_ENV_CCNAME, ccache_name, 1);
 		status = ADS_ERROR_KRB5(ads_kinit_password(ads)); 
 
 		if (ADS_ERR_OK(status)) {
-- 
2.5.5