wmi-1.3.16 from opsview.com

2019-02-16 00:16:52 +01:00
parent 163fdd3d1b
commit 17b3af2911
2146 changed files with 678824 additions and 0 deletions
@@ -0,0 +1,700 @@
+/* 
+   Unix SMB/CIFS implementation.
+
+   Kerberos utility functions for GENSEC
+   
+   Copyright (C) Andrew Bartlett <abartlet@samba.org> 2004-2005
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+   
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include "includes.h"
+#include "system/kerberos.h"
+#include "auth/kerberos/kerberos.h"
+#include "auth/credentials/credentials.h"
+#include "auth/credentials/credentials_krb5.h"
+
+struct principal_container {
+	struct smb_krb5_context *smb_krb5_context;
+	krb5_principal principal;
+};
+
+static int free_principal(struct principal_container *pc)
+{
+	/* current heimdal - 0.6.3, which we need anyway, fixes segfaults here */
+	krb5_free_principal(pc->smb_krb5_context->krb5_context, pc->principal);
+
+	return 0;
+}
+
+static krb5_error_code salt_principal_from_credentials(TALLOC_CTX *parent_ctx, 
+						       struct cli_credentials *machine_account, 
+						       struct smb_krb5_context *smb_krb5_context,
+						       krb5_principal *salt_princ)
+{
+	krb5_error_code ret;
+	char *machine_username;
+	char *salt_body;
+	char *lower_realm;
+	const char *salt_principal;
+	struct principal_container *mem_ctx = talloc(parent_ctx, struct principal_container);
+	if (!mem_ctx) {
+		return ENOMEM;
+	}
+
+	salt_principal = cli_credentials_get_salt_principal(machine_account);
+	if (salt_principal) {
+		ret = krb5_parse_name(smb_krb5_context->krb5_context, salt_principal, salt_princ); 
+	} else {
+		machine_username = talloc_strdup(mem_ctx, cli_credentials_get_username(machine_account));
+		
+		if (!machine_username) {
+			talloc_free(mem_ctx);
+			return ENOMEM;
+		}
+		
+		if (machine_username[strlen(machine_username)-1] == '$') {
+			machine_username[strlen(machine_username)-1] = '\0';
+		}
+		lower_realm = strlower_talloc(mem_ctx, cli_credentials_get_realm(machine_account));
+		if (!lower_realm) {
+			talloc_free(mem_ctx);
+			return ENOMEM;
+		}
+		
+		salt_body = talloc_asprintf(mem_ctx, "%s.%s", machine_username, 
+					    lower_realm);
+		if (!salt_body) {
+			talloc_free(mem_ctx);
+		return ENOMEM;
+		}
+		
+		ret = krb5_make_principal(smb_krb5_context->krb5_context, salt_princ, 
+					  cli_credentials_get_realm(machine_account), 
+					  "host", salt_body, NULL);
+	} 
+
+	if (ret == 0) {
+		/* This song-and-dance effectivly puts the principal
+		 * into talloc, so we can't loose it. */
+		mem_ctx->smb_krb5_context = talloc_reference(mem_ctx, smb_krb5_context);
+		mem_ctx->principal = *salt_princ;
+		talloc_set_destructor(mem_ctx, free_principal);
+	}
+	return ret;
+}
+
+/* Obtain the principal set on this context.  Requires a
+ * smb_krb5_context because we are doing krb5 principal parsing with
+ * the library routines.  The returned princ is placed in the talloc
+ * system by means of a destructor (do *not* free). */
+
+krb5_error_code principal_from_credentials(TALLOC_CTX *parent_ctx, 
+					   struct cli_credentials *credentials, 
+					   struct smb_krb5_context *smb_krb5_context,
+					   krb5_principal *princ)
+{
+	krb5_error_code ret;
+	const char *princ_string;
+	struct principal_container *mem_ctx = talloc(parent_ctx, struct principal_container);
+	if (!mem_ctx) {
+		return ENOMEM;
+	}
+	
+	princ_string = cli_credentials_get_principal(credentials, mem_ctx);
+
+	/* A NULL here has meaning, as the gssapi server case will
+	 * then use the principal from the client */
+	if (!princ_string) {
+		talloc_free(mem_ctx);
+		princ = NULL;
+		return 0;
+	}
+
+	ret = krb5_parse_name(smb_krb5_context->krb5_context,
+			      princ_string, princ);
+
+	if (ret == 0) {
+		/* This song-and-dance effectivly puts the principal
+		 * into talloc, so we can't loose it. */
+		mem_ctx->smb_krb5_context = talloc_reference(mem_ctx, smb_krb5_context);
+		mem_ctx->principal = *princ;
+		talloc_set_destructor(mem_ctx, free_principal);
+	}
+	return ret;
+}
+
+/**
+ * Return a freshly allocated ccache (destroyed by destructor on child
+ * of parent_ctx), for a given set of client credentials 
+ */
+
+ krb5_error_code kinit_to_ccache(TALLOC_CTX *parent_ctx,
+				 struct cli_credentials *credentials,
+				 struct smb_krb5_context *smb_krb5_context,
+				 krb5_ccache ccache) 
+{
+	krb5_error_code ret;
+	const char *password;
+	time_t kdc_time = 0;
+	krb5_principal princ;
+	int tries;
+	TALLOC_CTX *mem_ctx = talloc_new(parent_ctx);
+
+	if (!mem_ctx) {
+		return ENOMEM;
+	}
+
+	ret = principal_from_credentials(mem_ctx, credentials, smb_krb5_context, &princ);
+	if (ret) {
+		talloc_free(mem_ctx);
+		return ret;
+	}
+
+	password = cli_credentials_get_password(credentials);
+
+	tries = 2;
+	while (tries--) {
+		if (password) {
+			ret = kerberos_kinit_password_cc(smb_krb5_context->krb5_context, ccache, 
+							 princ, 
+							 password, NULL, &kdc_time);
+		} else {
+			/* No password available, try to use a keyblock instead */
+			
+			krb5_keyblock keyblock;
+			const struct samr_Password *mach_pwd;
+			mach_pwd = cli_credentials_get_nt_hash(credentials, mem_ctx);
+			if (!mach_pwd) {
+				talloc_free(mem_ctx);
+				DEBUG(1, ("kinit_to_ccache: No password available for kinit\n"));
+				return EINVAL;
+			}
+			ret = krb5_keyblock_init(smb_krb5_context->krb5_context,
+						 ETYPE_ARCFOUR_HMAC_MD5,
+						 mach_pwd->hash, sizeof(mach_pwd->hash), 
+						 &keyblock);
+			
+			if (ret == 0) {
+				ret = kerberos_kinit_keyblock_cc(smb_krb5_context->krb5_context, ccache, 
+								 princ,
+								 &keyblock, NULL, &kdc_time);
+				krb5_free_keyblock_contents(smb_krb5_context->krb5_context, &keyblock);
+			}
+		}
+
+		if (ret == KRB5KRB_AP_ERR_SKEW || ret == KRB5_KDCREP_SKEW) {
+			/* Perhaps we have been given an invalid skew, so try again without it */
+			time_t t = time(NULL);
+			krb5_set_real_time(smb_krb5_context->krb5_context, t, 0);
+		} else {
+			/* not a skew problem */
+			break;
+		}
+	}
+
+	if (ret == KRB5KRB_AP_ERR_SKEW || ret == KRB5_KDCREP_SKEW) {
+		DEBUG(1,("kinit for %s failed (%s)\n", 
+			 cli_credentials_get_principal(credentials, mem_ctx), 
+			 smb_get_krb5_error_message(smb_krb5_context->krb5_context, 
+						    ret, mem_ctx)));
+		talloc_free(mem_ctx);
+		return ret;
+	}
+
+	/* cope with ticket being in the future due to clock skew */
+	if ((unsigned)kdc_time > time(NULL)) {
+		time_t t = time(NULL);
+		int time_offset =(unsigned)kdc_time-t;
+		DEBUG(4,("Advancing clock by %d seconds to cope with clock skew\n", time_offset));
+		krb5_set_real_time(smb_krb5_context->krb5_context, t + time_offset + 1, 0);
+	}
+	
+	if (ret == KRB5KDC_ERR_PREAUTH_FAILED && cli_credentials_wrong_password(credentials)) {
+		ret = kinit_to_ccache(parent_ctx,
+				      credentials,
+				      smb_krb5_context,
+				      ccache); 
+	}
+	if (ret) {
+		DEBUG(1,("kinit for %s failed (%s)\n", 
+			 cli_credentials_get_principal(credentials, mem_ctx), 
+			 smb_get_krb5_error_message(smb_krb5_context->krb5_context, 
+						    ret, mem_ctx)));
+		talloc_free(mem_ctx);
+		return ret;
+	} 
+	return 0;
+}
+
+static int free_keytab(struct keytab_container *ktc)
+{
+	krb5_kt_close(ktc->smb_krb5_context->krb5_context, ktc->keytab);
+
+	return 0;
+}
+
+int smb_krb5_open_keytab(TALLOC_CTX *mem_ctx,
+			 struct smb_krb5_context *smb_krb5_context, 
+			 const char *keytab_name, struct keytab_container **ktc) 
+{
+	krb5_keytab keytab;
+	int ret;
+	ret = krb5_kt_resolve(smb_krb5_context->krb5_context, keytab_name, &keytab);
+	if (ret) {
+		DEBUG(1,("failed to open krb5 keytab: %s\n", 
+			 smb_get_krb5_error_message(smb_krb5_context->krb5_context, 
+						    ret, mem_ctx)));
+		return ret;
+	}
+
+	*ktc = talloc(mem_ctx, struct keytab_container);
+	if (!*ktc) {
+		return ENOMEM;
+	}
+
+	(*ktc)->smb_krb5_context = talloc_reference(*ktc, smb_krb5_context);
+	(*ktc)->keytab = keytab;
+	talloc_set_destructor(*ktc, free_keytab);
+
+	return 0;
+}
+
+struct enctypes_container {
+	struct smb_krb5_context *smb_krb5_context;
+	krb5_enctype *enctypes;
+};
+
+static int free_enctypes(struct enctypes_container *etc)
+{
+	free_kerberos_etypes(etc->smb_krb5_context->krb5_context, etc->enctypes);
+	return 0;
+}
+
+static krb5_error_code keytab_add_keys(TALLOC_CTX *parent_ctx,
+				       const char *princ_string,
+				       krb5_principal princ,
+				       krb5_principal salt_princ,
+				       int kvno,
+				       const char *password_s,
+				       struct smb_krb5_context *smb_krb5_context,
+				       krb5_keytab keytab)
+{
+	int i;
+	krb5_error_code ret;
+	krb5_enctype *enctypes;
+	char *enctype_string;
+	struct enctypes_container *etc;
+	krb5_data password;
+	TALLOC_CTX *mem_ctx = talloc_new(parent_ctx);
+	if (!mem_ctx) {
+		return ENOMEM;
+	}
+
+	etc = talloc(mem_ctx, struct enctypes_container);
+	if (!etc) {
+		talloc_free(mem_ctx);
+		return ENOMEM;
+	}
+	ret = get_kerberos_allowed_etypes(smb_krb5_context->krb5_context, 
+					  &enctypes);
+	if (ret != 0) {
+		DEBUG(1,("keytab_add_keys: getting encrption types failed (%s)\n",
+			 error_message(ret)));
+		talloc_free(mem_ctx);
+		return ret;
+	}
+
+	etc->smb_krb5_context = talloc_reference(etc, smb_krb5_context);
+	etc->enctypes = enctypes;
+
+	talloc_set_destructor(etc, free_enctypes);
+
+	password.data = discard_const_p(char *, password_s);
+	password.length = strlen(password_s);
+
+	for (i=0; enctypes[i]; i++) {
+		krb5_keytab_entry entry;
+		ret = create_kerberos_key_from_string(smb_krb5_context->krb5_context, 
+						      salt_princ, &password, &entry.keyblock, enctypes[i]);
+		if (ret != 0) {
+			talloc_free(mem_ctx);
+			return ret;
+		}
+
+                entry.principal = princ;
+                entry.vno       = kvno;
+		ret = krb5_kt_add_entry(smb_krb5_context->krb5_context, keytab, &entry);
+		enctype_string = NULL;
+		krb5_enctype_to_string(smb_krb5_context->krb5_context, enctypes[i], &enctype_string);
+		if (ret != 0) {
+			DEBUG(1, ("Failed to add %s entry for %s(kvno %d) to keytab: %s\n",
+				  enctype_string,
+				  princ_string,
+				  kvno,
+				  smb_get_krb5_error_message(smb_krb5_context->krb5_context, 
+							     ret, mem_ctx)));
+			talloc_free(mem_ctx);
+			free(enctype_string);		
+			krb5_free_keyblock_contents(smb_krb5_context->krb5_context, &entry.keyblock);
+			return ret;
+		}
+
+		DEBUG(5, ("Added %s(kvno %d) to keytab (%s)\n", 
+			  princ_string, kvno,
+			  enctype_string));
+		free(enctype_string);		
+		
+		krb5_free_keyblock_contents(smb_krb5_context->krb5_context, &entry.keyblock);
+	}
+	talloc_free(mem_ctx);
+	return 0;
+}
+
+static int create_keytab(TALLOC_CTX *parent_ctx,
+			 struct cli_credentials *machine_account,
+			 struct smb_krb5_context *smb_krb5_context,
+			 krb5_keytab keytab,
+			 BOOL add_old) 
+{
+	krb5_error_code ret;
+	const char *password_s;
+	char *enctype_string;
+	const char *old_secret;
+	int kvno;
+	krb5_principal salt_princ;
+	krb5_principal princ;
+	const char *princ_string;
+
+	TALLOC_CTX *mem_ctx = talloc_new(parent_ctx);
+	if (!mem_ctx) {
+		return ENOMEM;
+	}
+
+	princ_string = cli_credentials_get_principal(machine_account, mem_ctx);
+	/* Get the principal we will store the new keytab entries under */
+	ret = principal_from_credentials(mem_ctx, machine_account, smb_krb5_context, &princ);
+	if (ret) {
+		DEBUG(1,("create_keytab: makeing krb5 principal failed (%s)\n",
+			 smb_get_krb5_error_message(smb_krb5_context->krb5_context, 
+						    ret, mem_ctx)));
+		talloc_free(mem_ctx);
+		return ret;
+	}
+
+	/* The salt used to generate these entries may be different however, fetch that */
+	ret = salt_principal_from_credentials(mem_ctx, machine_account, 
+					      smb_krb5_context, 
+					      &salt_princ);
+	if (ret) {
+		DEBUG(1,("create_keytab: makeing salt principal failed (%s)\n",
+			 smb_get_krb5_error_message(smb_krb5_context->krb5_context, 
+						    ret, mem_ctx)));
+		talloc_free(mem_ctx);
+		return ret;
+	}
+
+	/* Finally, do the dance to get the password to put in the entry */
+	password_s = cli_credentials_get_password(machine_account);
+	if (!password_s) {
+		/* If we don't have the plaintext password, try for
+		 * the MD4 password hash */
+
+		krb5_keytab_entry entry;
+		const struct samr_Password *mach_pwd;
+		mach_pwd = cli_credentials_get_nt_hash(machine_account, mem_ctx);
+		if (!mach_pwd) {
+			DEBUG(1, ("create_keytab: Domain trust informaton for account %s not available\n",
+				  cli_credentials_get_principal(machine_account, mem_ctx)));
+			talloc_free(mem_ctx);
+			return EINVAL;
+		}
+		ret = krb5_keyblock_init(smb_krb5_context->krb5_context,
+					 ETYPE_ARCFOUR_HMAC_MD5,
+					 mach_pwd->hash, sizeof(mach_pwd->hash), 
+					 &entry.keyblock);
+		if (ret) {
+			DEBUG(1, ("create_keytab: krb5_keyblock_init failed: %s\n",
+				  smb_get_krb5_error_message(smb_krb5_context->krb5_context, 
+							     ret, mem_ctx)));
+			talloc_free(mem_ctx);
+			return ret;
+		}
+
+		entry.principal = princ;
+		entry.vno       = cli_credentials_get_kvno(machine_account);
+		ret = krb5_kt_add_entry(smb_krb5_context->krb5_context, keytab, &entry);
+		if (ret) {
+			DEBUG(1, ("Failed to add ARCFOUR_HMAC (only) entry for %s to keytab: %s",
+				  cli_credentials_get_principal(machine_account, mem_ctx), 
+				  smb_get_krb5_error_message(smb_krb5_context->krb5_context, 
+							     ret, mem_ctx)));
+			talloc_free(mem_ctx);
+			krb5_free_keyblock_contents(smb_krb5_context->krb5_context, &entry.keyblock);
+			return ret;
+		}
+		
+		krb5_enctype_to_string(smb_krb5_context->krb5_context, 
+				       ETYPE_ARCFOUR_HMAC_MD5,
+				       &enctype_string);
+		DEBUG(5, ("Added %s(kvno %d) to keytab (%s)\n", 
+			  cli_credentials_get_principal(machine_account, mem_ctx),
+			  cli_credentials_get_kvno(machine_account),
+			  enctype_string));
+		free(enctype_string);		
+
+		krb5_free_keyblock_contents(smb_krb5_context->krb5_context, &entry.keyblock);
+
+		/* Can't go any further, we only have this one key */
+		talloc_free(mem_ctx);
+		return 0;
+	}
+	
+	kvno = cli_credentials_get_kvno(machine_account);
+	/* good, we actually have the real plaintext */
+	ret = keytab_add_keys(mem_ctx, princ_string, princ, salt_princ, 
+			      kvno, password_s, smb_krb5_context, keytab);
+	if (!ret) {
+		talloc_free(mem_ctx);
+		return ret;
+	}
+
+	if (!add_old || kvno == 0) {
+		talloc_free(mem_ctx);
+		return 0;
+	}
+
+	old_secret = cli_credentials_get_old_password(machine_account);
+	if (!old_secret) {
+		talloc_free(mem_ctx);
+		return 0;
+	}
+	
+	ret = keytab_add_keys(mem_ctx, princ_string, princ, salt_princ, 
+			      kvno - 1, old_secret, smb_krb5_context, keytab);
+	if (!ret) {
+		talloc_free(mem_ctx);
+		return ret;
+	}
+
+	talloc_free(mem_ctx);
+	return 0;
+}
+
+
+/*
+ * Walk the keytab, looking for entries of this principal name, with KVNO other than current kvno -1.
+ *
+ * These entries are now stale, we only keep the current, and previous entries around.
+ *
+ * Inspired by the code in Samba3 for 'use kerberos keytab'.
+ *
+ */
+
+static krb5_error_code remove_old_entries(TALLOC_CTX *parent_ctx,
+					  struct cli_credentials *machine_account,
+					  struct smb_krb5_context *smb_krb5_context,
+					  krb5_keytab keytab, BOOL *found_previous)
+{
+	krb5_error_code ret, ret2;
+	krb5_kt_cursor cursor;
+	krb5_principal princ;
+	int kvno;
+	TALLOC_CTX *mem_ctx = talloc_new(parent_ctx);
+	const char *princ_string;
+	if (!mem_ctx) {
+		return ENOMEM;
+	}
+
+	*found_previous = False;
+	princ_string = cli_credentials_get_principal(machine_account, mem_ctx);
+
+	/* Get the principal we will store the new keytab entries under */
+	ret = principal_from_credentials(mem_ctx, machine_account, smb_krb5_context, &princ);
+	if (ret) {
+		DEBUG(1,("update_keytab: makeing krb5 principal failed (%s)\n",
+			 smb_get_krb5_error_message(smb_krb5_context->krb5_context, 
+						    ret, mem_ctx)));
+		talloc_free(mem_ctx);
+		return ret;
+	}
+
+	kvno = cli_credentials_get_kvno(machine_account);
+
+	/* for each entry in the keytab */
+	ret = krb5_kt_start_seq_get(smb_krb5_context->krb5_context, keytab, &cursor);
+	switch (ret) {
+	case 0:
+		break;
+	case HEIM_ERR_OPNOTSUPP:
+	case ENOENT:
+	case KRB5_KT_END:
+		/* no point enumerating if there isn't anything here */
+		talloc_free(mem_ctx);
+		return 0;
+	default:
+		DEBUG(1,("failed to open keytab for read of old entries: %s\n",
+			 smb_get_krb5_error_message(smb_krb5_context->krb5_context, 
+						    ret, mem_ctx)));
+		talloc_free(mem_ctx);
+		return ret;
+	}
+
+	while (!ret) {
+		krb5_keytab_entry entry;
+		ret = krb5_kt_next_entry(smb_krb5_context->krb5_context, keytab, &entry, &cursor);
+		if (ret) {
+			break;
+		}
+		/* if it matches our principal */
+		if (!krb5_kt_compare(smb_krb5_context->krb5_context, &entry, princ, 0, 0)) {
+			/* Free the entry, it wasn't the one we were looking for anyway */
+			krb5_kt_free_entry(smb_krb5_context->krb5_context, &entry);
+			continue;
+		}
+
+		/* delete it, if it is not kvno -1 */
+		if (entry.vno != (kvno - 1 )) {
+			/* Release the enumeration.  We are going to
+			 * have to start this from the top again,
+			 * because deletes during enumeration may not
+			 * always be consistant.
+			 *
+			 * Also, the enumeration locks a FILE: keytab
+			 */
+		
+			krb5_kt_end_seq_get(smb_krb5_context->krb5_context, keytab, &cursor);
+
+			ret = krb5_kt_remove_entry(smb_krb5_context->krb5_context, keytab, &entry);
+			krb5_kt_free_entry(smb_krb5_context->krb5_context, &entry);
+
+			/* Deleted: Restart from the top */
+			ret2 = krb5_kt_start_seq_get(smb_krb5_context->krb5_context, keytab, &cursor);
+			if (ret2) {
+				krb5_kt_free_entry(smb_krb5_context->krb5_context, &entry);
+				DEBUG(1,("failed to restart enumeration of keytab: %s\n",
+					 smb_get_krb5_error_message(smb_krb5_context->krb5_context, 
+								    ret, mem_ctx)));
+				
+				talloc_free(mem_ctx);
+				return ret2;
+			}
+
+			if (ret) {
+				break;
+			}
+			
+		} else {
+			*found_previous = True;
+		}
+		
+		/* Free the entry, we don't need it any more */
+		krb5_kt_free_entry(smb_krb5_context->krb5_context, &entry);
+		
+		
+	}
+	krb5_kt_end_seq_get(smb_krb5_context->krb5_context, keytab, &cursor);
+
+	switch (ret) {
+	case 0:
+		break;
+	case ENOENT:
+	case KRB5_KT_END:
+		ret = 0;
+		break;
+	default:
+		DEBUG(1,("failed in deleting old entries for principal: %s: %s\n",
+			 princ_string, 
+			 smb_get_krb5_error_message(smb_krb5_context->krb5_context, 
+						    ret, mem_ctx)));
+	}
+	talloc_free(mem_ctx);
+	return ret;
+}
+
+int smb_krb5_update_keytab(TALLOC_CTX *parent_ctx,
+			   struct cli_credentials *machine_account,
+			   struct smb_krb5_context *smb_krb5_context,
+			   struct keytab_container *keytab_container) 
+{
+	krb5_error_code ret;
+	BOOL found_previous;
+	TALLOC_CTX *mem_ctx = talloc_new(parent_ctx);
+	if (!mem_ctx) {
+		return ENOMEM;
+	}
+	
+	ret = remove_old_entries(mem_ctx, machine_account, 
+				 smb_krb5_context, keytab_container->keytab, &found_previous);
+	if (ret != 0) {
+		talloc_free(mem_ctx);
+		return ret;
+	}
+	
+	/* Create a new keytab.  If during the cleanout we found
+	 * entires for kvno -1, then don't try and duplicate them.
+	 * Otherwise, add kvno, and kvno -1 */
+	
+	ret = create_keytab(mem_ctx, machine_account, smb_krb5_context, 
+			    keytab_container->keytab, 
+			    found_previous ? False : True);
+	talloc_free(mem_ctx);
+	return ret;
+}
+
+_PUBLIC_ int smb_krb5_create_memory_keytab(TALLOC_CTX *parent_ctx,
+				  struct cli_credentials *machine_account,
+				  struct smb_krb5_context *smb_krb5_context,
+				  struct keytab_container **keytab_container) 
+{
+	krb5_error_code ret;
+	TALLOC_CTX *mem_ctx = talloc_new(parent_ctx);
+	const char *rand_string;
+	const char *keytab_name;
+	if (!mem_ctx) {
+		return ENOMEM;
+	}
+	
+	*keytab_container = talloc(mem_ctx, struct keytab_container);
+
+	rand_string = generate_random_str(mem_ctx, 16);
+	if (!rand_string) {
+		talloc_free(mem_ctx);
+		return ENOMEM;
+	}
+
+	keytab_name = talloc_asprintf(mem_ctx, "MEMORY:%s", 
+				      rand_string);
+	if (!keytab_name) {
+		talloc_free(mem_ctx);
+		return ENOMEM;
+	}
+
+	ret = smb_krb5_open_keytab(mem_ctx, smb_krb5_context, keytab_name, keytab_container);
+	if (ret) {
+		return ret;
+	}
+
+	ret = smb_krb5_update_keytab(mem_ctx, machine_account, smb_krb5_context, *keytab_container);
+	if (ret == 0) {
+		talloc_steal(parent_ctx, *keytab_container);
+	} else {
+		*keytab_container = NULL;
+	}
+	talloc_free(mem_ctx);
+	return ret;
+}
+