_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@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

1 files changed, 64 insertions, 15 deletions

diff --git a/source3/rpc_server/netlogon/srv_netlog_nt.c b/source3/rpc_server/netlogon/srv_netlog_nt.c
index 6a42f345c53..c36e6590b5c 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);
+
+			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);
 
-	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 = UserInternal5InformationNew;
 
-	info18.nt_pwd_active = true;
+			init_samr_CryptPasswordEx(cr->creds.password,
+						  &session_key,
+						  &info26.password);
 
-	info->info18 = info18;
+			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,
@@ -1353,6 +1393,10 @@ NTSTATUS _netr_ServerPasswordSet2(struct pipes_struct *p,
 		return status;
 	}
 
+	DEBUG(3,("_netr_ServerPasswordSet2: Server Password Seti2 by remote "
+		 "machine:[%s] on account [%s]\n",
+		 r->in.computer_name, creds->computer_name));
+
 	memcpy(password_buf.data, r->in.new_password->data, 512);
 	SIVAL(password_buf.data, 512, r->in.new_password->length);
 
@@ -1362,18 +1406,23 @@ NTSTATUS _netr_ServerPasswordSet2(struct pipes_struct *p,
 		netlogon_creds_arcfour_crypt(creds, password_buf.data, 516);
 	}
 
-	if (!extract_pw_from_buffer(p->mem_ctx, password_buf.data, &plaintext)) {
+	if (!decode_pw_buffer(p->mem_ctx,
+			      password_buf.data,
+			      (char**) &plaintext.data,
+			      &plaintext.length,
+			      CH_UTF16)) {
+		DEBUG(2,("_netr_ServerPasswordSet2: unable to extract password "
+			 "from a buffer. Rejecting auth request as a wrong password\n"));
 		TALLOC_FREE(creds);
 		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;
 }