krb5-samba: interdomain trust uses different salt principal

Salt principal for the interdomain trust is krbtgt/DOMAIN@REALM where
DOMAIN is the sAMAccountName without the dollar sign ($)

The salt principal for the BLA$ user object was generated wrong.

dn: CN=bla.base,CN=System,DC=w4edom-l4,DC=base
securityIdentifier: S-1-5-21-4053568372-2049667917-3384589010
trustDirection: 3
trustPartner: bla.base
trustPosixOffset: -2147483648
trustType: 2
trustAttributes: 8
flatName: BLA

dn: CN=BLA$,CN=Users,DC=w4edom-l4,DC=base
userAccountControl: 2080
primaryGroupID: 513
objectSid: S-1-5-21-278041429-3399921908-1452754838-1597
accountExpires: 9223372036854775807
sAMAccountName: BLA$
sAMAccountType: 805306370
pwdLastSet: 131485652467995000

The salt stored by Windows in the package_PrimaryKerberosBlob
(within supplementalCredentials) seems to be
'W4EDOM-L4.BASEkrbtgtBLA' for the above trust
and Samba stores 'W4EDOM-L4.BASEBLA$'.

While the salt used when building the keys from
trustAuthOutgoing/trustAuthIncoming is
'W4EDOM-L4.BASEkrbtgtBLA.BASE', which we handle correct.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13539

Pair-Programmed-With: Stefan Metzmacher <metze@samba.org>

Signed-off-by: Alexander Bokovoy <ab@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Wed Sep  5 03:57:22 CEST 2018 on sn-devel-144

(cherry picked from commit f3e349bebc443133fdbe4e14b148ca8db8237060)

Autobuild-User(v4-7-test): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(v4-7-test): Wed Sep  5 18:44:46 CEST 2018 on sn-devel-144

6 files changed, 63 insertions, 26 deletions

diff --git a/auth/credentials/credentials_krb5.c b/auth/credentials/credentials_krb5.c
index b88497dcace..fb4679747c0 100644
--- a/auth/credentials/credentials_krb5.c
+++ b/auth/credentials/credentials_krb5.c
@@ -34,6 +34,7 @@
 #include "auth/kerberos/kerberos_util.h"
 #include "auth/kerberos/pac_utils.h"
 #include "param/param.h"
+#include "../libds/common/flags.h"
 
 static void cli_credentials_invalidate_client_gss_creds(
 					struct cli_credentials *cred,
@@ -971,7 +972,7 @@ _PUBLIC_ int cli_credentials_get_keytab(struct cli_credentials *cred,
 	const char *upn = NULL;
 	const char *realm = cli_credentials_get_realm(cred);
 	char *salt_principal = NULL;
-	bool is_computer = false;
+	uint32_t uac_flags = 0;
 
 	if (cred->keytab_obtained >= (MAX(cred->principal_obtained, 
 					  cred->username_obtained))) {
@@ -996,9 +997,15 @@ _PUBLIC_ int cli_credentials_get_keytab(struct cli_credentials *cred,
 
 	switch (cred->secure_channel_type) {
 	case SEC_CHAN_WKSTA:
-	case SEC_CHAN_BDC:
 	case SEC_CHAN_RODC:
-		is_computer = true;
+		uac_flags = UF_WORKSTATION_TRUST_ACCOUNT;
+		break;
+	case SEC_CHAN_BDC:
+		uac_flags = UF_SERVER_TRUST_ACCOUNT;
+		break;
+	case SEC_CHAN_DOMAIN:
+	case SEC_CHAN_DNS_DOMAIN:
+		uac_flags = UF_INTERDOMAIN_TRUST_ACCOUNT;
 		break;
 	default:
 		upn = cli_credentials_get_principal(cred, mem_ctx);
@@ -1006,13 +1013,14 @@ _PUBLIC_ int cli_credentials_get_keytab(struct cli_credentials *cred,
 			TALLOC_FREE(mem_ctx);
 			return ENOMEM;
 		}
+		uac_flags = UF_NORMAL_ACCOUNT;
 		break;
 	}
 
 	ret = smb_krb5_salt_principal(realm,
 				      username, /* sAMAccountName */
 				      upn, /* userPrincipalName */
-				      is_computer,
+				      uac_flags,
 				      mem_ctx,
 				      &salt_principal);
 	if (ret) {
diff --git a/lib/krb5_wrap/krb5_samba.c b/lib/krb5_wrap/krb5_samba.c
index 0ba8aaecaea..73e89ea9525 100644
--- a/lib/krb5_wrap/krb5_samba.c
+++ b/lib/krb5_wrap/krb5_samba.c
@@ -24,6 +24,7 @@
 #include "system/filesys.h"
 #include "krb5_samba.h"
 #include "lib/crypto/crypto.h"
+#include "../libds/common/flags.h"
 
 #ifdef HAVE_COM_ERR_H
 #include <com_err.h>
@@ -445,8 +446,7 @@ int smb_krb5_get_pw_salt(krb5_context context,
  * @param[in]  userPrincipalName  The userPrincipalName attribute of the object
  *                                or NULL is not available.
  *
- * @param[in]  is_computer        The indication of the object includes
- *                                objectClass=computer.
+ * @param[in]  uac_flags          UF_ACCOUNT_TYPE_MASKed userAccountControl field
  *
  * @param[in]  mem_ctx            The TALLOC_CTX to allocate _salt_principal.
  *
@@ -459,7 +459,7 @@ int smb_krb5_get_pw_salt(krb5_context context,
 int smb_krb5_salt_principal(const char *realm,
 			    const char *sAMAccountName,
 			    const char *userPrincipalName,
-			    bool is_computer,
+			    uint32_t uac_flags,
 			    TALLOC_CTX *mem_ctx,
 			    char **_salt_principal)
 {
@@ -480,6 +480,23 @@ int smb_krb5_salt_principal(const char *realm,
 		return EINVAL;
 	}
 
+	if (uac_flags & ~UF_ACCOUNT_TYPE_MASK) {
+		/*
+		 * catch callers which still
+		 * pass 'true'.
+		 */
+		TALLOC_FREE(frame);
+		return EINVAL;
+	}
+	if (uac_flags == 0) {
+		/*
+		 * catch callers which still
+		 * pass 'false'.
+		 */
+		TALLOC_FREE(frame);
+		return EINVAL;
+	}
+
 	upper_realm = strupper_talloc(frame, realm);
 	if (upper_realm == NULL) {
 		TALLOC_FREE(frame);
@@ -493,7 +510,7 @@ int smb_krb5_salt_principal(const char *realm,
 	/*
 	 * Determine a salting principal
 	 */
-	if (is_computer) {
+	if (uac_flags & UF_TRUST_ACCOUNT_MASK) {
 		int computer_len = 0;
 		char *tmp = NULL;
 
@@ -502,20 +519,32 @@ int smb_krb5_salt_principal(const char *realm,
 			computer_len -= 1;
 		}
 
-		tmp = talloc_asprintf(frame, "host/%*.*s.%s",
-				      computer_len, computer_len,
-				      sAMAccountName, realm);
-		if (tmp == NULL) {
-			TALLOC_FREE(frame);
-			return ENOMEM;
-		}
+		if (uac_flags & UF_INTERDOMAIN_TRUST_ACCOUNT) {
+			principal = talloc_asprintf(frame, "krbtgt/%*.*s",
+						    computer_len, computer_len,
+						    sAMAccountName);
+			if (principal == NULL) {
+				TALLOC_FREE(frame);
+				return ENOMEM;
+			}
+		} else {
 
-		principal = strlower_talloc(frame, tmp);
-		TALLOC_FREE(tmp);
-		if (principal == NULL) {
-			TALLOC_FREE(frame);
-			return ENOMEM;
+			tmp = talloc_asprintf(frame, "host/%*.*s.%s",
+					      computer_len, computer_len,
+					      sAMAccountName, realm);
+			if (tmp == NULL) {
+				TALLOC_FREE(frame);
+				return ENOMEM;
+			}
+
+			principal = strlower_talloc(frame, tmp);
+			TALLOC_FREE(tmp);
+			if (principal == NULL) {
+				TALLOC_FREE(frame);
+				return ENOMEM;
+			}
 		}
+
 		principal_len = strlen(principal);
 
 	} else if (userPrincipalName != NULL) {
diff --git a/lib/krb5_wrap/krb5_samba.h b/lib/krb5_wrap/krb5_samba.h
index 315d3c3492e..8305c1f77af 100644
--- a/lib/krb5_wrap/krb5_samba.h
+++ b/lib/krb5_wrap/krb5_samba.h
@@ -353,7 +353,7 @@ int smb_krb5_get_pw_salt(krb5_context context,
 int smb_krb5_salt_principal(const char *realm,
 			    const char *sAMAccountName,
 			    const char *userPrincipalName,
-			    bool is_computer,
+			    uint32_t uac_flags,
 			    TALLOC_CTX *mem_ctx,
 			    char **_salt_principal);
 int smb_krb5_salt_principal2data(krb5_context context,
diff --git a/selftest/knownfail.d/trust_user_account b/selftest/knownfail.d/trust_user_account
deleted file mode 100644
index 1de5052b11d..00000000000
--- a/selftest/knownfail.d/trust_user_account
+++ /dev/null
@@ -1 +0,0 @@
-^samba4.blackbox.trust_user_account.get.virtualKerberosSalt.for.TDA
diff --git a/source3/passdb/machine_account_secrets.c b/source3/passdb/machine_account_secrets.c
index d36fa268a4b..ce435ef3404 100644
--- a/source3/passdb/machine_account_secrets.c
+++ b/source3/passdb/machine_account_secrets.c
@@ -36,6 +36,7 @@
 #include "lib/crypto/crypto.h"
 #include "lib/krb5_wrap/krb5_samba.h"
 #include "lib/util/time_basic.h"
+#include "../libds/common/flags.h"
 
 #undef DBGC_CLASS
 #define DBGC_CLASS DBGC_PASSDB
@@ -1600,7 +1601,7 @@ NTSTATUS secrets_store_JoinCtx(const struct libnet_JoinCtx *r)
 		ret = smb_krb5_salt_principal(info->domain_info.dns_domain.string,
 					      info->account_name,
 					      NULL /* userPrincipalName */,
-					      true /* is_computer */,
+					      UF_WORKSTATION_TRUST_ACCOUNT,
 					      info, &p);
 		if (ret != 0) {
 			status = krb5_to_nt_status(ret);
diff --git a/source4/dsdb/samdb/ldb_modules/password_hash.c b/source4/dsdb/samdb/ldb_modules/password_hash.c
index 3a2582106d3..87784f0ed4c 100644
--- a/source4/dsdb/samdb/ldb_modules/password_hash.c
+++ b/source4/dsdb/samdb/ldb_modules/password_hash.c
@@ -128,7 +128,6 @@ struct setup_password_fields_io {
 		NTTIME pwdLastSet;
 		const char *sAMAccountName;
 		const char *user_principal_name;
-		bool is_computer;
 		bool is_krbtgt;
 		uint32_t restrictions;
 		struct dom_sid *account_sid;
@@ -676,15 +675,17 @@ static int setup_kerberos_keys(struct setup_password_fields_io *io)
 	krb5_data salt;
 	krb5_keyblock key;
 	krb5_data cleartext_data;
+	uint32_t uac_flags = 0;
 
 	ldb = ldb_module_get_ctx(io->ac->module);
 	cleartext_data.data = (char *)io->n.cleartext_utf8->data;
 	cleartext_data.length = io->n.cleartext_utf8->length;
 
+	uac_flags = io->u.userAccountControl & UF_ACCOUNT_TYPE_MASK;
 	krb5_ret = smb_krb5_salt_principal(io->ac->status->domain_data.realm,
 					   io->u.sAMAccountName,
 					   io->u.user_principal_name,
-					   io->u.is_computer,
+					   uac_flags,
 					   io->ac,
 					   &salt_principal);
 	if (krb5_ret) {
@@ -3151,7 +3152,6 @@ static int setup_io(struct ph_context *ac,
 								      "sAMAccountName", NULL);
 	io->u.user_principal_name	= ldb_msg_find_attr_as_string(info_msg,
 								      "userPrincipalName", NULL);
-	io->u.is_computer		= ldb_msg_check_string_attribute(info_msg, "objectClass", "computer");
 
 	/* Ensure it has an objectSID too */
 	io->u.account_sid = samdb_result_dom_sid(ac, info_msg, "objectSid");