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CVE-2021-20251 s4:dsdb: Make badPwdCount update atomic

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We reread the account details inside the transaction in case the account
has been locked out in the meantime. If it has, we return the
appropriate error code.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14611

Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
This commit is contained in:
Joseph Sutton 2022-07-09 15:54:12 +12:00 committed by Andrew Bartlett
parent a65147a9e9
commit 96479747bd
2 changed files with 24 additions and 8 deletions
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5
selftest/flapping.d/ldap-pwd-change-race
View File

@ -1,5 +0,0 @@
# This test currently depends on a race. The password_hash dsdb module
# relinquishes and immediately reacquires a transaction lock, and another
# process may be able to acquire it during the short period of time in which it
# is not held.
^samba.tests.krb5.lockout_tests.samba.tests.krb5.lockout_tests.LockoutTests.test_lockout_race_ldap_pw_change.ad_dc:local

27
source4/dsdb/samdb/ldb_modules/password_hash.c
View File

@ -45,6 +45,7 @@
#include "lib/crypto/md4.h"
#include "param/param.h"
#include "lib/krb5_wrap/krb5_samba.h"
#include "auth/auth_sam.h"
#include "auth/common_auth.h"
#include "lib/messaging/messaging.h"
#include "lib/param/loadparm.h"
@ -2729,7 +2730,8 @@ static int make_error_and_update_badPwdCount(struct setup_password_fields_io *io
struct ldb_context *ldb = ldb_module_get_ctx(io->ac->module);
struct ldb_message *mod_msg = NULL;
struct ldb_message *pso_msg = NULL;
NTSTATUS status;
struct ldb_message *current = NULL;
NTSTATUS status = NT_STATUS_OK;
int ret; /* The errors we will actually return */
int dbg_ret; /* The errors we can only complain about in logs */
@ -2775,13 +2777,28 @@ static int make_error_and_update_badPwdCount(struct setup_password_fields_io *io
goto done;
}
/*
* Re-read the account details, using the GUID in case the DN
* is being changed.
*/
status = authsam_reread_user_logon_data(
ldb, io->ac,
io->ac->search_res->message,
&current);
if (!NT_STATUS_IS_OK(status)) {
/* The re-read can return account locked out, as well
* as an internal error
*/
goto end_transaction;
}
/* PSO search result is optional (NULL if no PSO applies) */
if (io->ac->pso_res != NULL) {
pso_msg = io->ac->pso_res->message;
}
status = dsdb_update_bad_pwd_count(io->ac, ldb,
io->ac->search_res->message,
current,
io->ac->dom_res->message,
pso_msg,
&mod_msg);
@ -2831,7 +2848,11 @@ end_transaction:
done:
ret = LDB_ERR_CONSTRAINT_VIOLATION;
*werror = WERR_INVALID_PASSWORD;
if (NT_STATUS_EQUAL(status, NT_STATUS_ACCOUNT_LOCKED_OUT)) {
*werror = WERR_ACCOUNT_LOCKED_OUT;
} else {
*werror = WERR_INVALID_PASSWORD;
}
ldb_asprintf_errstring(ldb,
"%08X: %s - check_password_restrictions: "
"The old password specified doesn't match!",