s3-libads: Rework kerberos_return_pac() to use GENSEC for the server-side

This removes the last user of ads_verify_ticket(), and means that we
only have one code path to verify an incoming krb5 (GSSAPI) ticket.

Andrew Bartlett

Signed-off-by: Stefan Metzmacher <metze@samba.org>

1 files changed, 167 insertions, 22 deletions

diff --git a/source3/libads/authdata.c b/source3/libads/authdata.c
index 44279a24d7..5a8ca28b14 100644
--- a/source3/libads/authdata.c
+++ b/source3/libads/authdata.c
@@ -26,15 +26,90 @@
 #include "librpc/gen_ndr/ndr_krb5pac.h"
 #include "smb_krb5.h"
 #include "libads/kerberos_proto.h"
+#include "auth/common_auth.h"
+#include "lib/param/param.h"
+#include "librpc/crypto/gse.h"
+#include "auth/gensec/gensec.h"
+#include "../libcli/auth/spnego.h"
 
 #ifdef HAVE_KRB5
 
+struct smb_krb5_context;
+
 /****************************************************************
-Given a username, password and other details, return the
-PAC_LOGON_INFO (the structure containing the important user
-information such as groups).
+Callback to get the PAC_LOGON_INFO from the blob
 ****************************************************************/
+static NTSTATUS kerberos_fetch_pac(struct auth4_context *auth_ctx,
+				   TALLOC_CTX *mem_ctx,
+				   struct smb_krb5_context *smb_krb5_context,
+				   DATA_BLOB *pac_blob,
+				   const char *princ_name,
+				   const struct tsocket_address *remote_address,
+				   uint32_t session_info_flags,
+				   struct auth_session_info **session_info)
+{
+	TALLOC_CTX *tmp_ctx;
+	struct PAC_DATA *pac_data = NULL;
+	struct PAC_LOGON_INFO *logon_info = NULL;
+	unsigned int i;
+	NTSTATUS status = NT_STATUS_INTERNAL_ERROR;
+
+	tmp_ctx = talloc_new(mem_ctx);
+	if (!tmp_ctx) {
+		return NT_STATUS_NO_MEMORY;
+	}
+
+	if (pac_blob) {
+		status = kerberos_decode_pac(tmp_ctx,
+				     *pac_blob,
+				     NULL, NULL, NULL, NULL, 0, &pac_data);
+		if (!NT_STATUS_IS_OK(status)) {
+			goto done;
+		}
+
+		/* get logon name and logon info */
+		for (i = 0; i < pac_data->num_buffers; i++) {
+			struct PAC_BUFFER *data_buf = &pac_data->buffers[i];
+
+			switch (data_buf->type) {
+			case PAC_TYPE_LOGON_INFO:
+				if (!data_buf->info) {
+					break;
+				}
+				logon_info = data_buf->info->logon_info.info;
+				break;
+			default:
+				break;
+			}
+		}
+		if (!logon_info) {
+			DEBUG(1, ("Invalid PAC data, missing logon info!\n"));
+			status = NT_STATUS_NOT_FOUND;
+			goto done;
+		}
+	}
+	talloc_set_name_const(logon_info, "struct PAC_LOGON_INFO");
+
+	auth_ctx->private_data = talloc_steal(auth_ctx, logon_info);
+	*session_info = talloc_zero(mem_ctx, struct auth_session_info);
+	if (!*session_info) {
+		status = NT_STATUS_NO_MEMORY;
+		goto done;
+	}
+	status = NT_STATUS_OK;
+
+done:
+	TALLOC_FREE(tmp_ctx);
 
+	return status;
+}
+
+/*
+ * Given the username/password, do a kinit, store the ticket in
+ * cache_name if specified, and return the PAC_LOGON_INFO (the
+ * structure containing the important user information such as
+ * groups).
+ */
 NTSTATUS kerberos_return_pac(TALLOC_CTX *mem_ctx,
 			     const char *name,
 			     const char *pass,
@@ -46,20 +121,29 @@ NTSTATUS kerberos_return_pac(TALLOC_CTX *mem_ctx,
 			     bool add_netbios_addr,
 			     time_t renewable_time,
 			     const char *impersonate_princ_s,
-			     struct PAC_LOGON_INFO **logon_info)
+			     struct PAC_LOGON_INFO **_logon_info)
 {
 	krb5_error_code ret;
 	NTSTATUS status = NT_STATUS_INVALID_PARAMETER;
-	DATA_BLOB tkt, ap_rep, sesskey1, sesskey2;
-	char *client_princ_out = NULL;
+	DATA_BLOB tkt, tkt_wrapped, ap_rep, sesskey1;
 	const char *auth_princ = NULL;
 	const char *local_service = NULL;
 	const char *cc = "MEMORY:kerberos_return_pac";
+	struct auth_session_info *session_info;
+	struct gensec_security *gensec_server_context;
+
+	struct gensec_settings *gensec_settings;
+	size_t idx = 0;
+	struct auth4_context *auth_context;
+	struct loadparm_context *lp_ctx;
+	struct PAC_LOGON_INFO *logon_info = NULL;
+
+	TALLOC_CTX *tmp_ctx = talloc_new(mem_ctx);
+	NT_STATUS_HAVE_NO_MEMORY(tmp_ctx);
 
 	ZERO_STRUCT(tkt);
 	ZERO_STRUCT(ap_rep);
 	ZERO_STRUCT(sesskey1);
-	ZERO_STRUCT(sesskey2);
 
 	if (!name || !pass) {
 		return NT_STATUS_INVALID_PARAMETER;
@@ -137,28 +221,92 @@ NTSTATUS kerberos_return_pac(TALLOC_CTX *mem_ctx,
 		status = krb5_to_nt_status(ret);
 		goto out;
 	}
-	status = ads_verify_ticket(mem_ctx,
-				   lp_realm(),
-				   time_offset,
-				   &tkt,
-				   &client_princ_out,
-				   logon_info,
-				   &ap_rep,
-				   &sesskey2,
-				   False);
+
+	/* wrap that up in a nice GSS-API wrapping */
+	tkt_wrapped = spnego_gen_krb5_wrap(tmp_ctx, tkt, TOK_ID_KRB_AP_REQ);
+	if (tkt_wrapped.data == NULL) {
+		status = NT_STATUS_NO_MEMORY;
+		goto out;
+	}
+
+	auth_context = talloc_zero(tmp_ctx, struct auth4_context);
+	if (auth_context == NULL) {
+		status = NT_STATUS_NO_MEMORY;
+		goto out;
+	}
+	auth_context->generate_session_info_pac = kerberos_fetch_pac;
+
+	lp_ctx = loadparm_init_s3(tmp_ctx, loadparm_s3_context());
+	if (lp_ctx == NULL) {
+		status = NT_STATUS_INVALID_SERVER_STATE;
+		DEBUG(10, ("loadparm_init_s3 failed\n"));
+		goto out;
+	}
+
+	gensec_settings = lpcfg_gensec_settings(tmp_ctx, lp_ctx);
+	if (lp_ctx == NULL) {
+		status = NT_STATUS_NO_MEMORY;
+		DEBUG(10, ("lpcfg_gensec_settings failed\n"));
+		goto out;
+	}
+
+	gensec_settings->backends = talloc_zero_array(gensec_settings,
+						      struct gensec_security_ops *, 2);
+	if (gensec_settings->backends == NULL) {
+		status = NT_STATUS_NO_MEMORY;
+		goto out;
+	}
+
+	gensec_init();
+
+	gensec_settings->backends[idx++] = &gensec_gse_krb5_security_ops;
+
+	status = gensec_server_start(tmp_ctx, gensec_settings,
+					auth_context, &gensec_server_context);
+
 	if (!NT_STATUS_IS_OK(status)) {
-		DEBUG(1,("ads_verify_ticket failed: %s\n",
-			nt_errstr(status)));
+		DEBUG(1, (__location__ "Failed to start server-side GENSEC to validate a Kerberos ticket: %s\n", nt_errstr(status)));
 		goto out;
 	}
 
-	if (!*logon_info) {
+	talloc_unlink(tmp_ctx, lp_ctx);
+	talloc_unlink(tmp_ctx, gensec_settings);
+	talloc_unlink(tmp_ctx, auth_context);
+
+	status = gensec_start_mech_by_oid(gensec_server_context, GENSEC_OID_KERBEROS5);
+	if (!NT_STATUS_IS_OK(status)) {
+		DEBUG(1, (__location__ "Failed to start server-side GENSEC krb5 to validate a Kerberos ticket: %s\n", nt_errstr(status)));
+		goto out;
+	}
+
+	/* Do a client-server update dance */
+	status = gensec_update(gensec_server_context, tmp_ctx, NULL, tkt_wrapped, &ap_rep);
+	if (!NT_STATUS_IS_OK(status)) {
+		DEBUG(1, ("gensec_update() failed: %s\n", nt_errstr(status)));
+		goto out;
+	}
+
+	/* Now return the PAC information to the callers.  We ingore
+	 * the session_info and instead pick out the PAC via the
+	 * private_data on the auth_context */
+	status = gensec_session_info(gensec_server_context, tmp_ctx, &session_info);
+	if (!NT_STATUS_IS_OK(status)) {
+		DEBUG(1, ("Unable to obtain PAC via gensec_session_info\n"));
+		goto out;
+	}
+
+	logon_info = talloc_get_type_abort(gensec_server_context->auth_context->private_data,
+					   struct PAC_LOGON_INFO);
+	if (logon_info == NULL) {
 		DEBUG(1,("no PAC\n"));
 		status = NT_STATUS_INVALID_PARAMETER;
 		goto out;
 	}
 
+	*_logon_info = talloc_move(mem_ctx, &logon_info);
+
 out:
+	talloc_free(tmp_ctx);
 	if (cc != cache_name) {
 		ads_kdestroy(cc);
 	}
@@ -166,9 +314,6 @@ out:
 	data_blob_free(&tkt);
 	data_blob_free(&ap_rep);
 	data_blob_free(&sesskey1);
-	data_blob_free(&sesskey2);
-
-	TALLOC_FREE(client_princ_out);
 
 	return status;
 }