From b371acd1e03ef7eaf644932a8aafadcf49f7db3f Mon Sep 17 00:00:00 2001
From: Stefan Metzmacher <metze@samba.org>
Date: Sat, 22 Jan 2022 01:08:26 +0100
Subject: [PATCH] dcesrv_core: wrap gensec_*() calls in [un]become_root() calls

This is important for the source3/rpc_server code as it might
be called embedded in smbd and may not run as root with access
to our private tdb/ldb files.

Note this is only really needed for 4.15 and older, as
we no longer run the rpc_server embedded in smbd,
but we better be consistent for now.

This should be able to fix the problem the printing no longer works
on Windows 7 with 2021-10 monthly rollup patch (KB5006743).

Windows uses NTLMSSP with privacy at the DCERPC layer on top
of NCACN_NP (smb).

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14867

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>
(similar to commit 0651fa474cd68b18d8eb9bdc7c4ba5b847ba9ad9)
---
 librpc/rpc/dcesrv_auth.c         |  6 ++++++
 librpc/rpc/dcesrv_core.c         | 18 ++++++++++++++++++
 librpc/rpc/dcesrv_core.h         |  2 ++
 source3/rpc_server/rpc_config.c  |  2 ++
 source4/rpc_server/service_rpc.c | 10 ++++++++++
 5 files changed, 38 insertions(+)

diff --git a/librpc/rpc/dcesrv_auth.c b/librpc/rpc/dcesrv_auth.c
index 9d8df6c42e29..b4a29ea9ab4e 100644
--- a/librpc/rpc/dcesrv_auth.c
+++ b/librpc/rpc/dcesrv_auth.c
@@ -81,6 +81,7 @@ static bool dcesrv_auth_prepare_gensec(struct dcesrv_call_state *call)
 {
 	struct dcesrv_connection *dce_conn = call->conn;
 	struct dcesrv_auth *auth = call->auth_state;
+	struct dcesrv_context_callbacks *cb = &call->conn->dce_ctx->callbacks;
 	NTSTATUS status;
 
 	if (auth->auth_started) {
@@ -129,9 +130,11 @@ static bool dcesrv_auth_prepare_gensec(struct dcesrv_call_state *call)
 	auth->auth_level = call->in_auth_info.auth_level;
 	auth->auth_context_id = call->in_auth_info.auth_context_id;
 
+	cb->auth.become_root();
 	status = call->conn->dce_ctx->callbacks.auth.gensec_prepare(auth,
 						call,
 						&auth->gensec_security);
+	cb->auth.unbecome_root();
 	if (!NT_STATUS_IS_OK(status)) {
 		DEBUG(1, ("Failed to call samba_server_gensec_start %s\n",
 			  nt_errstr(status)));
@@ -324,6 +327,7 @@ bool dcesrv_auth_bind(struct dcesrv_call_state *call)
 NTSTATUS dcesrv_auth_complete(struct dcesrv_call_state *call, NTSTATUS status)
 {
 	struct dcesrv_auth *auth = call->auth_state;
+	struct dcesrv_context_callbacks *cb = &call->conn->dce_ctx->callbacks;
 	const char *pdu = "<unknown>";
 
 	switch (call->pkt.ptype) {
@@ -354,9 +358,11 @@ NTSTATUS dcesrv_auth_complete(struct dcesrv_call_state *call, NTSTATUS status)
 		return status;
 	}
 
+	cb->auth.become_root();
 	status = gensec_session_info(auth->gensec_security,
 				     auth,
 				     &auth->session_info);
+	cb->auth.unbecome_root();
 	if (!NT_STATUS_IS_OK(status)) {
 		DEBUG(1, ("Failed to establish session_info: %s\n",
 			  nt_errstr(status)));
diff --git a/librpc/rpc/dcesrv_core.c b/librpc/rpc/dcesrv_core.c
index 0bab4c106410..3f7c72db5845 100644
--- a/librpc/rpc/dcesrv_core.c
+++ b/librpc/rpc/dcesrv_core.c
@@ -951,6 +951,7 @@ static NTSTATUS dcesrv_bind(struct dcesrv_call_state *call)
 	struct dcerpc_binding *ep_2nd_description = NULL;
 	const char *endpoint = NULL;
 	struct dcesrv_auth *auth = call->auth_state;
+	struct dcesrv_context_callbacks *cb = &call->conn->dce_ctx->callbacks;
 	struct dcerpc_ack_ctx *ack_ctx_list = NULL;
 	struct dcerpc_ack_ctx *ack_features = NULL;
 	struct tevent_req *subreq = NULL;
@@ -1155,9 +1156,11 @@ static NTSTATUS dcesrv_bind(struct dcesrv_call_state *call)
 		return dcesrv_auth_reply(call);
 	}
 
+	cb->auth.become_root();
 	subreq = gensec_update_send(call, call->event_ctx,
 				    auth->gensec_security,
 				    call->in_auth_info.credentials);
+	cb->auth.unbecome_root();
 	if (subreq == NULL) {
 		return NT_STATUS_NO_MEMORY;
 	}
@@ -1172,10 +1175,13 @@ static void dcesrv_bind_done(struct tevent_req *subreq)
 		tevent_req_callback_data(subreq,
 		struct dcesrv_call_state);
 	struct dcesrv_connection *conn = call->conn;
+	struct dcesrv_context_callbacks *cb = &call->conn->dce_ctx->callbacks;
 	NTSTATUS status;
 
+	cb->auth.become_root();
 	status = gensec_update_recv(subreq, call,
 				    &call->out_auth_info->credentials);
+	cb->auth.unbecome_root();
 	TALLOC_FREE(subreq);
 
 	status = dcesrv_auth_complete(call, status);
@@ -1233,6 +1239,7 @@ static NTSTATUS dcesrv_auth3(struct dcesrv_call_state *call)
 {
 	struct dcesrv_connection *conn = call->conn;
 	struct dcesrv_auth *auth = call->auth_state;
+	struct dcesrv_context_callbacks *cb = &call->conn->dce_ctx->callbacks;
 	struct tevent_req *subreq = NULL;
 	NTSTATUS status;
 
@@ -1277,9 +1284,11 @@ static NTSTATUS dcesrv_auth3(struct dcesrv_call_state *call)
 		return NT_STATUS_OK;
 	}
 
+	cb->auth.become_root();
 	subreq = gensec_update_send(call, call->event_ctx,
 				    auth->gensec_security,
 				    call->in_auth_info.credentials);
+	cb->auth.unbecome_root();
 	if (subreq == NULL) {
 		return NT_STATUS_NO_MEMORY;
 	}
@@ -1295,10 +1304,13 @@ static void dcesrv_auth3_done(struct tevent_req *subreq)
 		struct dcesrv_call_state);
 	struct dcesrv_connection *conn = call->conn;
 	struct dcesrv_auth *auth = call->auth_state;
+	struct dcesrv_context_callbacks *cb = &call->conn->dce_ctx->callbacks;
 	NTSTATUS status;
 
+	cb->auth.become_root();
 	status = gensec_update_recv(subreq, call,
 				    &call->out_auth_info->credentials);
+	cb->auth.unbecome_root();
 	TALLOC_FREE(subreq);
 
 	status = dcesrv_auth_complete(call, status);
@@ -1570,6 +1582,7 @@ static NTSTATUS dcesrv_alter(struct dcesrv_call_state *call)
 	struct ncacn_packet *pkt = &call->ack_pkt;
 	uint32_t extra_flags = 0;
 	struct dcesrv_auth *auth = call->auth_state;
+	struct dcesrv_context_callbacks *cb = &call->conn->dce_ctx->callbacks;
 	struct dcerpc_ack_ctx *ack_ctx_list = NULL;
 	struct tevent_req *subreq = NULL;
 	size_t i;
@@ -1681,9 +1694,11 @@ static NTSTATUS dcesrv_alter(struct dcesrv_call_state *call)
 		return dcesrv_auth_reply(call);
 	}
 
+	cb->auth.become_root();
 	subreq = gensec_update_send(call, call->event_ctx,
 				    auth->gensec_security,
 				    call->in_auth_info.credentials);
+	cb->auth.unbecome_root();
 	if (subreq == NULL) {
 		return NT_STATUS_NO_MEMORY;
 	}
@@ -1698,10 +1713,13 @@ static void dcesrv_alter_done(struct tevent_req *subreq)
 		tevent_req_callback_data(subreq,
 		struct dcesrv_call_state);
 	struct dcesrv_connection *conn = call->conn;
+	struct dcesrv_context_callbacks *cb = &call->conn->dce_ctx->callbacks;
 	NTSTATUS status;
 
+	cb->auth.become_root();
 	status = gensec_update_recv(subreq, call,
 				    &call->out_auth_info->credentials);
+	cb->auth.unbecome_root();
 	TALLOC_FREE(subreq);
 
 	status = dcesrv_auth_complete(call, status);
diff --git a/librpc/rpc/dcesrv_core.h b/librpc/rpc/dcesrv_core.h
index 41ae622ecfe6..48adebe1b0a2 100644
--- a/librpc/rpc/dcesrv_core.h
+++ b/librpc/rpc/dcesrv_core.h
@@ -386,6 +386,8 @@ struct dcesrv_context_callbacks {
 		NTSTATUS (*gensec_prepare)(TALLOC_CTX *mem_ctx,
 					struct dcesrv_call_state *call,
 					struct gensec_security **out);
+		void (*become_root)(void);
+		void (*unbecome_root)(void);
 	} auth;
 	struct {
 		NTSTATUS (*find)(struct dcesrv_call_state *);
diff --git a/source3/rpc_server/rpc_config.c b/source3/rpc_server/rpc_config.c
index 2f1a01da1c0b..289c4f398409 100644
--- a/source3/rpc_server/rpc_config.c
+++ b/source3/rpc_server/rpc_config.c
@@ -31,6 +31,8 @@
 static struct dcesrv_context_callbacks srv_callbacks = {
 	.log.successful_authz = dcesrv_log_successful_authz,
 	.auth.gensec_prepare = dcesrv_auth_gensec_prepare,
+	.auth.become_root = become_root,
+	.auth.unbecome_root = unbecome_root,
 	.assoc_group.find = dcesrv_assoc_group_find,
 };
 
diff --git a/source4/rpc_server/service_rpc.c b/source4/rpc_server/service_rpc.c
index ae8d91e68f01..5bc28f85ca78 100644
--- a/source4/rpc_server/service_rpc.c
+++ b/source4/rpc_server/service_rpc.c
@@ -40,9 +40,19 @@
 #include "../libcli/named_pipe_auth/npa_tstream.h"
 #include "samba/process_model.h"
 
+static void skip_become_root(void)
+{
+}
+
+static void skip_unbecome_root(void)
+{
+}
+
 struct dcesrv_context_callbacks srv_callbacks = {
 	.log.successful_authz = log_successful_dcesrv_authz_event,
 	.auth.gensec_prepare = dcesrv_gensec_prepare,
+	.auth.become_root = skip_become_root,
+	.auth.unbecome_root = skip_unbecome_root,
 	.assoc_group.find = dcesrv_assoc_group_find,
 };
 
-- 
2.25.1