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s4-auth: For LDAP simple bind, fall back to checking the ENCTYPE_AES256_CTS_HMAC_SHA1_96 if stored

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Since we don't store a salt per-key, but only a single salt, when we do
not have the NT hash in the unicodePwd (eg ntlm auth = disabled), the check
will fail for a previous password if the account was renamed prior to a
newer password being set.

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

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
This commit is contained in:
Andrew Bartlett 2022-06-10 12:47:01 +12:00
parent 18f2a6b231
commit 6029e2250c
3 changed files with 244 additions and 31 deletions
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3
auth/common_auth.h
View File

@ -129,6 +129,9 @@ struct auth4_context {
/* Private data for the callbacks on this auth context */
void *private_data;
/* Kerberos context, set up on demand */
struct smb_krb5_context *smb_krb5_context;
struct tevent_req *(*check_ntlm_password_send)(TALLOC_CTX *mem_ctx,
struct tevent_context *ev,
struct auth4_context *auth_ctx,

269
source4/auth/ntlm/auth_sam.c
View File

@ -3,7 +3,7 @@
Password and authentication handling
Copyright (C) Andrew Bartlett <abartlet@samba.org> 2001-2009
Copyright (C) Gerald Carter 2003
Copyright (C) Stefan Metzmacher 2005
Copyright (C) Stefan Metzmacher 2005-2010
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
@ -37,6 +37,9 @@
#include "libcli/auth/libcli_auth.h"
#include "libds/common/roles.h"
#include "lib/util/tevent_ntstatus.h"
#include "system/kerberos.h"
#include "auth/kerberos/kerberos.h"
#include "kdc/db-glue.h"
#undef DBGC_CLASS
#define DBGC_CLASS DBGC_AUTH
@ -53,6 +56,9 @@ extern const char *domain_ref_attrs[];
static NTSTATUS authsam_password_ok(struct auth4_context *auth_context,
TALLOC_CTX *mem_ctx,
const struct samr_Password *nt_pwd,
struct smb_krb5_context *smb_krb5_context,
const DATA_BLOB *stored_aes_256_key,
const krb5_data *salt,
const struct auth_usersupplied_info *user_info,
DATA_BLOB *user_sess_key,
DATA_BLOB *lm_sess_key)
@ -63,6 +69,46 @@ static NTSTATUS authsam_password_ok(struct auth4_context *auth_context,
case AUTH_PASSWORD_PLAIN:
{
const struct auth_usersupplied_info *user_info_temp;
if (nt_pwd == NULL && stored_aes_256_key != NULL && user_info->password.plaintext != NULL) {
bool pw_equal;
int krb5_ret;
DATA_BLOB supplied_aes_256_key;
krb5_keyblock key;
krb5_data cleartext_data = {
.data = user_info->password.plaintext,
.length = strlen(user_info->password.plaintext)
};
*lm_sess_key = data_blob_null;
*user_sess_key = data_blob_null;
krb5_ret = smb_krb5_create_key_from_string(smb_krb5_context->krb5_context,
NULL,
salt,
&cleartext_data,
ENCTYPE_AES256_CTS_HMAC_SHA1_96,
&key);
if (krb5_ret) {
DBG_ERR("generation of a aes256-cts-hmac-sha1-96 key for password comparison failed: %s",
smb_get_krb5_error_message(smb_krb5_context->krb5_context,
krb5_ret, mem_ctx));
return NT_STATUS_INTERNAL_ERROR;
}
supplied_aes_256_key = data_blob_const(KRB5_KEY_DATA(&key),
KRB5_KEY_LENGTH(&key));
pw_equal = data_blob_equal_const_time(&supplied_aes_256_key,
stored_aes_256_key);
krb5_free_keyblock_contents(smb_krb5_context->krb5_context, &key);
if (!pw_equal) {
return NT_STATUS_WRONG_PASSWORD;
}
return NT_STATUS_OK;
}
status = encrypt_user_info(mem_ctx, auth_context,
AUTH_PASSWORD_HASH,
user_info, &user_info_temp);
@ -197,6 +243,47 @@ static void auth_sam_trigger_repl_secret(TALLOC_CTX *mem_ctx,
TALLOC_FREE(tmp_ctx);
}
static const struct samr_Password *hide_invalid_nthash(const struct samr_Password *in)
{
/*
* This is the result of:
*
* E_md4hash("", zero_string_hash.hash);
*/
static const struct samr_Password zero_string_hash = {
.hash = {
0x31, 0xd6, 0xcf, 0xe0, 0xd1, 0x6a, 0xe9, 0x31,
0xb7, 0x3c, 0x59, 0xd7, 0xe0, 0xc0, 0x89, 0xc0,
}
};
if (in == NULL) {
return NULL;
}
/*
* Skip over any all-zero hashes in the history. No known software
* stores these but just to be sure
*/
if (all_zero(in->hash, sizeof(in->hash))) {
return NULL;
}
/*
* This looks odd, but the password_hash module in the past has written
* this in the rare situation where (somehow) we didn't have an old NT
* hash (one of the old LM-only set paths)
*
* mem_equal_const_time() is used to avoid a timing attack
* when comparing secret data in the server with this constant
* value.
*/
if (mem_equal_const_time(in->hash, zero_string_hash.hash, 16)) {
in = NULL;
}
return in;
}
/*
* Check that a password is OK, and update badPwdCount if required.
@ -220,7 +307,15 @@ static NTSTATUS authsam_password_check_and_record(struct auth4_context *auth_con
const char * const attrs[] = { "pwdHistoryLength", NULL };
struct ldb_message *dom_msg;
struct samr_Password *nt_pwd;
DATA_BLOB _aes_256_key = data_blob_null;
DATA_BLOB *aes_256_key = NULL;
krb5_data _salt = { .data = NULL, .length = 0 };
krb5_data *salt = NULL;
DATA_BLOB salt_data = data_blob_null;
struct smb_krb5_context *smb_krb5_context = NULL;
const struct ldb_val *sc_val;
uint32_t userAccountControl = 0;
uint32_t current_kvno = 0;
bool am_rodc;
tmp_ctx = talloc_new(mem_ctx);
@ -243,6 +338,10 @@ static NTSTATUS authsam_password_check_and_record(struct auth4_context *auth_con
return nt_status;
}
userAccountControl = ldb_msg_find_attr_as_uint(msg,
"userAccountControl",
0);
sc_val = ldb_msg_find_ldb_val(msg, "supplementalCredentials");
if (nt_pwd == NULL && sc_val == NULL) {
@ -273,10 +372,55 @@ static NTSTATUS authsam_password_check_and_record(struct auth4_context *auth_con
}
}
auth_status = authsam_password_ok(auth_context, tmp_ctx,
/*
* If we don't have an NT password, pull a kerberos key
* instead for plaintext.
*/
if (nt_pwd == NULL &&
sc_val != NULL &&
user_info->password_state == AUTH_PASSWORD_PLAIN)
{
krb5_error_code krb5_ret;
krb5_ret = smb_krb5_init_context(tmp_ctx,
auth_context->lp_ctx,
&smb_krb5_context);
if (krb5_ret != 0) {
DBG_ERR("Failed to setup krb5_context: %s!",
error_message(krb5_ret));
return NT_STATUS_INTERNAL_ERROR;
}
/*
* Get the current salt from the record
*/
krb5_ret = dsdb_extract_aes_256_key(smb_krb5_context->krb5_context,
tmp_ctx,
msg,
userAccountControl,
NULL, /* kvno */
&current_kvno, /* kvno_out */
&_aes_256_key,
&salt_data);
if (krb5_ret == 0) {
aes_256_key = &_aes_256_key;
_salt.data = (char *)salt_data.data;
_salt.length = salt_data.length;
salt = &_salt;
}
}
auth_status = authsam_password_ok(auth_context,
tmp_ctx,
nt_pwd,
smb_krb5_context,
aes_256_key,
salt,
user_info,
user_sess_key, lm_sess_key);
if (NT_STATUS_IS_OK(auth_status)) {
if (user_sess_key->data) {
talloc_steal(mem_ctx, user_sess_key->data);
@ -317,7 +461,6 @@ static NTSTATUS authsam_password_check_and_record(struct auth4_context *auth_con
}
for (i = 1; i < MIN(history_len, 3); i++) {
struct samr_Password zero_string_hash;
const struct samr_Password *nt_history_pwd = NULL;
NTTIME pwdLastSet;
struct timeval tv_now;
@ -325,54 +468,120 @@ static NTSTATUS authsam_password_check_and_record(struct auth4_context *auth_con
int allowed_period_mins;
NTTIME allowed_period;
/* Reset these variables back to starting as empty */
aes_256_key = NULL;
salt = NULL;
/*
* Obtain the i'th old password from the NT password
* history for this user.
*
* We avoid issues with salts (which are not
* recorded for historical AES256 keys) by using the
* ntPwdHistory in preference.
*/
nt_status = samdb_result_passwords_from_history(tmp_ctx,
auth_context->lp_ctx,
msg, i,
NULL,
&nt_history_pwd);
/*
* Belts and braces: note that
* samdb_result_passwords_from_history() currently
* does not fail for missing attributes, it only sets
* nt_history_pwd = NULL, so "break" and fall down to
* the bad password count upate if this happens
*/
if (!NT_STATUS_IS_OK(nt_status)) {
/*
* If we don't find element 'i' we won't find
* 'i+1' ...
*/
break;
}
nt_history_pwd = hide_invalid_nthash(nt_history_pwd);
/*
* We choose to avoid any issues
* around different LM and NT history
* lengths by only checking the NT
* history
* We don't have an NT hash from the
* ntPwdHistory, but we can still perform the
* password check with the AES256
* key.
*
* However, this is the second preference as
* it will fail if the account was renamed
* prior to a password change (as we won't
* have the correct salt available to
* calculate the AES256 key).
*/
if (nt_history_pwd == NULL) {
if (nt_history_pwd == NULL && sc_val != NULL &&
user_info->password_state == AUTH_PASSWORD_PLAIN &&
current_kvno >= i)
{
krb5_error_code krb5_ret;
const uint32_t request_kvno = current_kvno - i;
/*
* If we don't find element 'i' we won't find
* 'i+1' ...
* Confirm we have a krb5_context set up
*/
if (smb_krb5_context == NULL) {
/*
* We get here if we had a unicodePwd
* for the current password, no
* ntPwdHistory, a valid previous
* Kerberos history AND are processing
* a simple bind.
*
* This really is a corner case so
* favour cleaner code over trying to
* allow for an old password. It is
* more likely this is just a new
* account.
*
* "break" out of the loop and fall down
* to the bad password update
*/
break;
}
/*
* Get the current salt from the record
*/
krb5_ret = dsdb_extract_aes_256_key(smb_krb5_context->krb5_context,
tmp_ctx,
msg,
userAccountControl,
&request_kvno, /* kvno */
NULL, /* kvno_out */
&_aes_256_key,
&salt_data);
if (krb5_ret != 0) {
break;
}
aes_256_key = &_aes_256_key;
_salt.data = (char *)salt_data.data;
_salt.length = salt_data.length;
salt = &_salt;
} else if (nt_history_pwd == NULL) {
/*
* If we don't find element 'i' in the
* ntPwdHistory and can not fall back to the
* kerberos hash, we won't find 'i+1' ...
*/
break;
}
/* Skip over all-zero hashes in the history */
if (all_zero(nt_history_pwd->hash,
sizeof(nt_history_pwd->hash))) {
continue;
}
/*
* This looks odd, but the password_hash module writes this in if
* (somehow) we didn't have an old NT hash
*/
E_md4hash("", zero_string_hash.hash);
if (mem_equal_const_time(nt_history_pwd->hash, zero_string_hash.hash, 16)) {
continue;
}
auth_status = authsam_password_ok(auth_context, tmp_ctx,
nt_history_pwd,
smb_krb5_context,
aes_256_key,
salt,
user_info,
user_sess_key,
lm_sess_key);
if (!NT_STATUS_IS_OK(auth_status)) {
/*
* If this was not a correct password, try the next

3
source4/auth/ntlm/wscript_build
View File

@ -4,7 +4,8 @@ bld.SAMBA_MODULE('auth4_sam_module',
source='auth_sam.c',
subsystem='auth4',
init_function='auth4_sam_init',
deps='samdb auth4_sam NTLMSSP_COMMON samba-hostconfig RPC_NDR_IRPC MESSAGING'
deps='samdb auth4_sam NTLMSSP_COMMON samba-hostconfig RPC_NDR_IRPC MESSAGING db-glue',
enabled=bld.AD_DC_BUILD_IS_ENABLED()
)