[PATCH] allow passdb backend to change trusted domain object password with clear text
Alexander Bokovoy
ab at samba.org
Tue Apr 11 05:11:50 UTC 2017
On ti, 11 huhti 2017, Andrew Bartlett wrote:
> On Mon, 2017-04-10 at 16:51 +0300, Alexander Bokovoy wrote:
> > On ma, 10 huhti 2017, Andrew Bartlett wrote:
> > > On Mon, 2017-04-10 at 10:22 +0300, Alexander Bokovoy wrote:
> > > > On pe, 07 huhti 2017, Jeremy Allison wrote:
> > > > > On Fri, Apr 07, 2017 at 11:08:44PM +0300, Alexander Bokovoy
> > > > > wrote:
> > > > >
> > > > > > I'll see what I can do there but this code is a copy/paste
> > > > > > from
> > > > > > another
> > > > > > helper we have for NT/LM hash pass-through. Guenther already
> > > > > > asked me to
> > > > > > consider how I can going these two functions in a common
> > > > > > piece
> > > > > > that
> > > > > > could be called for both cases, so I'll do refactoring for
> > > > > > this
> > > > > > too.
> > > > >
> > > > > Thanks. That other code might be wrong too :-).
> > > >
> > > > Attached is the patch that unifies NT hash/plain text pass-
> > > > through.
> > > > This is a more concise change that doesn't duplicate existing
> > > > code.
> > >
> > > How certain are we that our plaintext password is null terminated?
> > >
> > > + cr.creds.password = (const char*) plaintext.data;
> >
> > Good question. A plain text password is a data blob represented as up
> > to
> > 256 WCHARs. It is UTF-16 coded on wire and we have its length from
> > the
> > buffer. SetUserInfo2 SAMR call chain in decode_pw_buffer() does
> > explicitly
> > expect 512+4 bytes in the buffer. It then calls
> > convert_string_talloc() to
> > convert it to UNIX charset passing the correct value of the plaintext
> > password length. However, convert_string_talloc() expects the length
> > of
> > input string *including* the terminating null and we pass just the
> > string length.
> >
> > convert_string_talloc() then explicitly null-terminates the resulting
> > string by adding two nulls. In most cases UNIX charset is UTF-8, so
> > we
> > get null-terminated UTF-8 string down to PASSDB layer.
> >
> > However, MS-SAMR does not limit what does the password should
> > contain.
> > It says it is 'userPassword' value. Either 'userPassword' or
> > 'unicodePwd' cannot contain null characters according to MS-ADTS
> > 3.1.1.3.1.5 because they must be proper UTF-8 and UTF-16 strings
> > accordingly.
> >
> > So I think we are good here,
>
> Please copy this into a comment, so we remember and an auditor can be
> re-assured.
Re-sent with updated comment.
--
/ Alexander Bokovoy
-------------- next part --------------
>From 98d14ec7005c0f49cd8f017f22aaf210f56c67c0 Mon Sep 17 00:00:00 2001
From: Alexander Bokovoy <ab at samba.org>
Date: Fri, 31 Mar 2017 12:44:58 +0300
Subject: [PATCH] _netr_ServerPasswordSet2: use info level 26 to set plain text
machine password
To support password change for machine or trusted domain accounts in Active
Directory environment we need to pass down actual plain text password
instead of NT hashes. This would allow a backend like ipasam to update
Kerberos keys as well as NT hashes.
By calling samr_SetUserInfo2 info level 26 we ensure PASSDB layer can
actually get the plain text password. If PASSDB backend implements
pdb_update_sam_account() callback, it then gets the plain text password
from samr_SetUserInfo2.
A plain text password is a data blob represented as up to 256 WCHARs. It
is UTF-16 coded on wire and we have its length from the buffer.
SetUserInfo2 SAMR call chain in decode_pw_buffer() does explicitly
expect 512+4 bytes in the buffer. It then calls convert_string_talloc()
to convert it to UNIX charset passing the correct value of the plaintext
password length. However, convert_string_talloc() expects the length of
input string *including* the terminating null and we pass just the
string length.
convert_string_talloc() then explicitly null-terminates the resulting
string by adding two nulls. In most cases UNIX charset is UTF-8, so we
get null-terminated UTF-8 string down to PASSDB layer.
MS-SAMR does not limit what does the password should contain. It says
it is 'userPassword' value. Either 'userPassword' or 'unicodePwd' cannot
contain null characters according to MS-ADTS 3.1.1.3.1.5 because they
must be proper UTF-8 and UTF-16 strings accordingly.
We are talking to our own SAMR service here.
Signed-off-by: Alexander Bokovoy <ab at samba.org>
---
source3/rpc_server/netlogon/srv_netlog_nt.c | 67 +++++++++++++++++++++++------
1 file changed, 53 insertions(+), 14 deletions(-)
diff --git a/source3/rpc_server/netlogon/srv_netlog_nt.c b/source3/rpc_server/netlogon/srv_netlog_nt.c
index 6a42f34..25af98e 100644
--- a/source3/rpc_server/netlogon/srv_netlog_nt.c
+++ b/source3/rpc_server/netlogon/srv_netlog_nt.c
@@ -33,6 +33,7 @@
#include "../librpc/gen_ndr/ndr_lsa_c.h"
#include "rpc_client/cli_lsarpc.h"
#include "rpc_client/init_lsa.h"
+#include "rpc_client/init_samr.h"
#include "rpc_server/rpc_ncacn_np.h"
#include "../libcli/security/security.h"
#include "../libcli/security/dom_sid.h"
@@ -1140,14 +1141,27 @@ static NTSTATUS netr_creds_server_step_check(struct pipes_struct *p,
return status;
}
+
/*************************************************************************
*************************************************************************/
+struct _samr_Credentials_t {
+ enum {
+ CRED_TYPE_NT_HASH,
+ CRED_TYPE_PLAIN_TEXT,
+ } cred_type;
+ union {
+ struct samr_Password *nt_hash;
+ const char *password;
+ } creds;
+};
+
+
static NTSTATUS netr_set_machine_account_password(TALLOC_CTX *mem_ctx,
struct auth_session_info *session_info,
struct messaging_context *msg_ctx,
const char *account_name,
- struct samr_Password *nt_hash)
+ struct _samr_Credentials_t *cr)
{
NTSTATUS status;
NTSTATUS result = NT_STATUS_OK;
@@ -1157,9 +1171,11 @@ static NTSTATUS netr_set_machine_account_password(TALLOC_CTX *mem_ctx,
uint32_t acct_ctrl;
union samr_UserInfo *info;
struct samr_UserInfo18 info18;
+ struct samr_UserInfo26 info26;
DATA_BLOB in,out;
int rc;
DATA_BLOB session_key;
+ enum samr_UserInfoLevel infolevel;
ZERO_STRUCT(user_handle);
@@ -1232,22 +1248,44 @@ static NTSTATUS netr_set_machine_account_password(TALLOC_CTX *mem_ctx,
goto out;
}
- ZERO_STRUCT(info18);
+ switch(cr->cred_type) {
+ case CRED_TYPE_NT_HASH:
+ ZERO_STRUCT(info18);
- in = data_blob_const(nt_hash->hash, 16);
- out = data_blob_talloc_zero(mem_ctx, 16);
- sess_crypt_blob(&out, &in, &session_key, true);
- memcpy(info18.nt_pwd.hash, out.data, out.length);
+ infolevel = UserInternal1Information;
+
+ in = data_blob_const(cr->creds.nt_hash, 16);
+ out = data_blob_talloc_zero(mem_ctx, 16);
+ sess_crypt_blob(&out, &in, &session_key, true);
+ memcpy(info18.nt_pwd.hash, out.data, out.length);
+
+ info18.nt_pwd_active = true;
+
+ info->info18 = info18;
+ break;
+ case CRED_TYPE_PLAIN_TEXT:
+ ZERO_STRUCT(info26);
- info18.nt_pwd_active = true;
+ infolevel = UserInternal5Information;
- info->info18 = info18;
+ init_samr_CryptPasswordEx(cr->creds.password,
+ &session_key,
+ &info26.password);
+
+ info26.password_expired = PASS_DONT_CHANGE_AT_NEXT_LOGON;
+ info->info26 = info26;
+ break;
+ default:
+ status = NT_STATUS_INTERNAL_ERROR;
+ goto out;
+ break;
+ }
become_root();
status = dcerpc_samr_SetUserInfo2(h,
mem_ctx,
&user_handle,
- UserInternal1Information,
+ infolevel,
info,
&result);
unbecome_root();
@@ -1277,6 +1315,7 @@ NTSTATUS _netr_ServerPasswordSet(struct pipes_struct *p,
NTSTATUS status = NT_STATUS_OK;
int i;
struct netlogon_creds_CredentialState *creds = NULL;
+ struct _samr_Credentials_t cr = { CRED_TYPE_NT_HASH, {0}};
DEBUG(5,("_netr_ServerPasswordSet: %d\n", __LINE__));
@@ -1311,11 +1350,12 @@ NTSTATUS _netr_ServerPasswordSet(struct pipes_struct *p,
DEBUG(100,("%02X ", r->in.new_password->hash[i]));
DEBUG(100,("\n"));
+ cr.creds.nt_hash = r->in.new_password;
status = netr_set_machine_account_password(p->mem_ctx,
p->session_info,
p->msg_ctx,
creds->account_name,
- r->in.new_password);
+ &cr);
return status;
}
@@ -1330,7 +1370,7 @@ NTSTATUS _netr_ServerPasswordSet2(struct pipes_struct *p,
struct netlogon_creds_CredentialState *creds = NULL;
DATA_BLOB plaintext;
struct samr_CryptPassword password_buf;
- struct samr_Password nt_hash;
+ struct _samr_Credentials_t cr = { CRED_TYPE_PLAIN_TEXT, {0}};
become_root();
status = netr_creds_server_step_check(p, p->mem_ctx,
@@ -1367,13 +1407,12 @@ NTSTATUS _netr_ServerPasswordSet2(struct pipes_struct *p,
return NT_STATUS_WRONG_PASSWORD;
}
- mdfour(nt_hash.hash, plaintext.data, plaintext.length);
-
+ cr.creds.password = (const char*) plaintext.data;
status = netr_set_machine_account_password(p->mem_ctx,
p->session_info,
p->msg_ctx,
creds->account_name,
- &nt_hash);
+ &cr);
TALLOC_FREE(creds);
return status;
}
--
2.9.3
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