s3-libcli Change krb5 smb sealing to call via gensec and gensec_gse

This also fixes the support for smb sealing with krb5 in make test, as
this now relies on secrets.tdb rather than /etc/krb5.keytab.

Andrew Bartlett

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

5 files changed, 86 insertions, 487 deletions

diff --git a/libcli/smb/smb_seal.c b/libcli/smb/smb_seal.c
index a6cfffb2e8..669b69ae00 100644
--- a/libcli/smb/smb_seal.c
+++ b/libcli/smb/smb_seal.c
@@ -169,150 +169,6 @@ static NTSTATUS common_gensec_encrypt_buffer(struct gensec_security *gensec,
 
 /******************************************************************************
  Generic code for client and server.
- gss-api decrypt an incoming buffer. We insist that the size of the
- unwrapped buffer must be smaller or identical to the incoming buffer.
-******************************************************************************/
-
-#if defined(HAVE_GSSAPI) && defined(HAVE_KRB5)
-static NTSTATUS common_gss_decrypt_buffer(struct smb_tran_enc_state_gss *gss_state, char *buf)
-{
-	gss_ctx_id_t gss_ctx = gss_state->gss_ctx;
-	OM_uint32 ret = 0;
-	OM_uint32 minor = 0;
-	int flags_got = 0;
-	gss_buffer_desc in_buf, out_buf;
-	size_t buf_len = smb_len_nbt(buf) + 4; /* Don't forget the 4 length bytes. */
-
-	if (buf_len < 8) {
-		return NT_STATUS_BUFFER_TOO_SMALL;
-	}
-
-	in_buf.value = buf + 8;
-	in_buf.length = buf_len - 8;
-
-	ret = gss_unwrap(&minor,
-			gss_ctx,
-			&in_buf,
-			&out_buf,
-			&flags_got,		/* did we get sign+seal ? */
-			(gss_qop_t *) NULL);
-
-	if (ret != GSS_S_COMPLETE) {
-		NTSTATUS status = NT_STATUS_ACCESS_DENIED;
-		char *gss_err;
-
-		gss_err = gssapi_error_string(talloc_tos(),
-					      ret, minor,
-					      GSS_C_NULL_OID);
-		DEBUG(0,("common_gss_decrypt_buffer: gss_unwrap failed. "
-			 "Error [%d/%d] - %s - %s\n",
-			 ret, minor, nt_errstr(status),
-			 gss_err ? gss_err : "<unknown>"));
-		talloc_free(gss_err);
-
-		return status;
-	}
-
-	if (out_buf.length > in_buf.length) {
-		DEBUG(0,("common_gss_decrypt_buffer: gss_unwrap size (%u) too large (%u) !\n",
-			(unsigned int)out_buf.length,
-			(unsigned int)in_buf.length ));
-		gss_release_buffer(&minor, &out_buf);
-		return NT_STATUS_INVALID_PARAMETER;
-	}
-
-	memcpy(buf + 8, out_buf.value, out_buf.length);
-	/* Reset the length and overwrite the header. */
-	smb_setlen_nbt(buf, out_buf.length + 4);
-
-	gss_release_buffer(&minor, &out_buf);
-	return NT_STATUS_OK;
-}
-
-/******************************************************************************
- Generic code for client and server.
- gss-api encrypt an outgoing buffer. Return the alloced encrypted pointer in buf_out.
-******************************************************************************/
-
-static NTSTATUS common_gss_encrypt_buffer(struct smb_tran_enc_state_gss *gss_state,
-					uint16_t enc_ctx_num,
-					char *buf,
-					char **ppbuf_out)
-{
-	gss_ctx_id_t gss_ctx = gss_state->gss_ctx;
-	OM_uint32 ret = 0;
-	OM_uint32 minor = 0;
-	int flags_got = 0;
-	gss_buffer_desc in_buf, out_buf;
-	size_t buf_len = smb_len_nbt(buf) + 4; /* Don't forget the 4 length bytes. */
-
-	*ppbuf_out = NULL;
-
-	if (buf_len < 8) {
-		return NT_STATUS_BUFFER_TOO_SMALL;
-	}
-
-	in_buf.value = buf + 8;
-	in_buf.length = buf_len - 8;
-
-	ret = gss_wrap(&minor,
-			gss_ctx,
-			true,			/* we want sign+seal. */
-			GSS_C_QOP_DEFAULT,
-			&in_buf,
-			&flags_got,		/* did we get sign+seal ? */
-			&out_buf);
-
-	if (ret != GSS_S_COMPLETE) {
-		NTSTATUS status = NT_STATUS_ACCESS_DENIED;
-		char *gss_err;
-
-		gss_err = gssapi_error_string(talloc_tos(),
-					      ret, minor,
-					      GSS_C_NULL_OID);
-		DEBUG(0,("common_gss_encrypt_buffer: gss_unwrap failed. "
-			 "Error [%d/%d] - %s - %s\n",
-			 ret, minor, nt_errstr(status),
-			 gss_err ? gss_err : "<unknown>"));
-		talloc_free(gss_err);
-
-		return status;
-	}
-
-	if (!flags_got) {
-		/* Sign+seal not supported. */
-		gss_release_buffer(&minor, &out_buf);
-		return NT_STATUS_NOT_SUPPORTED;
-	}
-
-	/* Ya see - this is why I *hate* gss-api. I don't
-	 * want to have to malloc another buffer of the
-	 * same size + 8 bytes just to get a continuous
-	 * header + buffer, but gss won't let me pass in
-	 * a pre-allocated buffer. Bastards (and you know
-	 * who you are....). I might fix this by
-	 * going to "encrypt_and_send" passing in a file
-	 * descriptor and doing scatter-gather write with
-	 * TCP cork on Linux. But I shouldn't have to
-	 * bother :-*(. JRA.
-	 */
-
-	*ppbuf_out = (char *)malloc(out_buf.length + 8); /* We know this can't wrap. */
-	if (!*ppbuf_out) {
-		gss_release_buffer(&minor, &out_buf);
-		return NT_STATUS_NO_MEMORY;
-	}
-
-	memcpy(*ppbuf_out+8, out_buf.value, out_buf.length);
-	smb_set_enclen(*ppbuf_out, out_buf.length + 4, enc_ctx_num);
-
-	gss_release_buffer(&minor, &out_buf);
-	return NT_STATUS_OK;
-}
-#endif
-
-/******************************************************************************
- Generic code for client and server.
  Encrypt an outgoing buffer. Return the alloced encrypted pointer in buf_out.
 ******************************************************************************/
 
@@ -324,16 +180,7 @@ NTSTATUS common_encrypt_buffer(struct smb_trans_enc_state *es, char *buffer, cha
 		return NT_STATUS_OK;
 	}
 
-	switch (es->smb_enc_type) {
-		case SMB_TRANS_ENC_NTLM:
-			return common_gensec_encrypt_buffer(es->s.gensec_security, es->enc_ctx_num, buffer, buf_out);
-#if defined(HAVE_GSSAPI) && defined(HAVE_KRB5)
-		case SMB_TRANS_ENC_GSS:
-			return common_gss_encrypt_buffer(es->s.gss_state, es->enc_ctx_num, buffer, buf_out);
-#endif
-		default:
-			return NT_STATUS_NOT_SUPPORTED;
-	}
+	return common_gensec_encrypt_buffer(es->s.gensec_security, es->enc_ctx_num, buffer, buf_out);
 }
 
 /******************************************************************************
@@ -349,38 +196,9 @@ NTSTATUS common_decrypt_buffer(struct smb_trans_enc_state *es, char *buf)
 		return NT_STATUS_OK;
 	}
 
-	switch (es->smb_enc_type) {
-		case SMB_TRANS_ENC_NTLM:
-			return common_gensec_decrypt_buffer(es->s.gensec_security, buf);
-#if defined(HAVE_GSSAPI) && defined(HAVE_KRB5)
-		case SMB_TRANS_ENC_GSS:
-			return common_gss_decrypt_buffer(es->s.gss_state, buf);
-#endif
-		default:
-			return NT_STATUS_NOT_SUPPORTED;
-	}
+	return common_gensec_decrypt_buffer(es->s.gensec_security, buf);
 }
 
-#if defined(HAVE_GSSAPI) && defined(HAVE_KRB5)
-/******************************************************************************
- Shutdown a gss encryption state.
-******************************************************************************/
-
-static void common_free_gss_state(struct smb_tran_enc_state_gss **pp_gss_state)
-{
-	OM_uint32 minor = 0;
-	struct smb_tran_enc_state_gss *gss_state = *pp_gss_state;
-
-	if (gss_state->creds != GSS_C_NO_CREDENTIAL) {
-		gss_release_cred(&minor, &gss_state->creds);
-	}
-	if (gss_state->gss_ctx != GSS_C_NO_CONTEXT) {
-		gss_delete_sec_context(&minor, &gss_state->gss_ctx, NULL);
-	}
-	SAFE_FREE(*pp_gss_state);
-}
-#endif
-
 /******************************************************************************
  Shutdown an encryption state.
 ******************************************************************************/
@@ -393,19 +211,9 @@ void common_free_encryption_state(struct smb_trans_enc_state **pp_es)
 		return;
 	}
 
-	if (es->smb_enc_type == SMB_TRANS_ENC_NTLM) {
-		if (es->s.gensec_security) {
-			TALLOC_FREE(es->s.gensec_security);
-		}
-	}
-#if defined(HAVE_GSSAPI) && defined(HAVE_KRB5)
-	if (es->smb_enc_type == SMB_TRANS_ENC_GSS) {
-		/* Free the gss context handle. */
-		if (es->s.gss_state) {
-			common_free_gss_state(&es->s.gss_state);
-		}
+	if (es->s.gensec_security) {
+		TALLOC_FREE(es->s.gensec_security);
 	}
-#endif
 	SAFE_FREE(es);
 	*pp_es = NULL;
 }
diff --git a/libcli/smb/smb_seal.h b/libcli/smb/smb_seal.h
index 9f9a8063cf..724b25ef5e 100644
--- a/libcli/smb/smb_seal.h
+++ b/libcli/smb/smb_seal.h
@@ -49,9 +49,6 @@ struct smb_trans_enc_state {
         bool enc_on;
         union {
                 struct gensec_security *gensec_security;
-#if defined(HAVE_GSSAPI) && defined(HAVE_KRB5)
-                struct smb_tran_enc_state_gss *gss_state;
-#endif
         } s;
 };
 
diff --git a/selftest/knownfail b/selftest/knownfail
index b0246e7b86..4a9f99e8cd 100644
--- a/selftest/knownfail
+++ b/selftest/knownfail
@@ -20,9 +20,6 @@
 ^samba3.blackbox.rpcclient over ncacn_np with \[spnego,smb2,bigendian\]
 ^samba3.blackbox.rpcclient over ncacn_np with \[spnego,connect,smb2\]
 ^samba3.blackbox.rpcclient over ncacn_np with \[spnego,connect,smb2,bigendian\]
-# GSSAPI/krb5 encrypted CIFS fails in the test environment at the moment
-^samba3.blackbox.smbclient_krb5 -e.smbclient
-^samba3.blackbox.smbclient_krb5 old ccache -e.smbclient
 # these show that we still have some differences between our system
 # with our internal iconv because it passes except when we bypass our
 # internal iconv modules
diff --git a/source3/libsmb/clifsinfo.c b/source3/libsmb/clifsinfo.c
index dd9da54d33..26f98311cb 100644
--- a/source3/libsmb/clifsinfo.c
+++ b/source3/libsmb/clifsinfo.c
@@ -30,6 +30,7 @@
 #include "auth_generic.h"
 #include "auth/gensec/gensec.h"
 #include "../libcli/smb/smbXcli_base.h"
+#include "auth/credentials/credentials.h"
 
 /****************************************************************************
  Get UNIX extensions version info.
@@ -585,16 +586,6 @@ static struct smb_trans_enc_state *make_cli_enc_state(enum smb_trans_enc_type sm
 	ZERO_STRUCTP(es);
 	es->smb_enc_type = smb_enc_type;
 
-#if defined(HAVE_GSSAPI) && defined(HAVE_KRB5)
-	if (smb_enc_type == SMB_TRANS_ENC_GSS) {
-		es->s.gss_state = SMB_MALLOC_P(struct smb_tran_enc_state_gss);
-		if (!es->s.gss_state) {
-			SAFE_FREE(es);
-			return NULL;
-		}
-		ZERO_STRUCTP(es->s.gss_state);
-	}
-#endif
 	return es;
 }
 
@@ -683,99 +674,33 @@ NTSTATUS cli_raw_ntlm_smb_encryption_start(struct cli_state *cli,
 	return status;
 }
 
-#if defined(HAVE_GSSAPI) && defined(HAVE_KRB5)
-
-#ifndef SMB_GSS_REQUIRED_FLAGS
-#define SMB_GSS_REQUIRED_FLAGS (GSS_C_CONF_FLAG|GSS_C_INTEG_FLAG|GSS_C_MUTUAL_FLAG|GSS_C_REPLAY_FLAG|GSS_C_SEQUENCE_FLAG)
-#endif
-
 /******************************************************************************
  Get client gss blob to send to a server.
 ******************************************************************************/
 
 static NTSTATUS make_cli_gss_blob(TALLOC_CTX *ctx,
-				struct smb_trans_enc_state *es,
-				const char *service,
-				const char *host,
+				struct gensec_security *gensec_security,
 				NTSTATUS status_in,
 				DATA_BLOB spnego_blob_in,
 				DATA_BLOB *p_blob_out)
 {
 	const char *krb_mechs[] = {OID_KERBEROS5, NULL};
-	OM_uint32 ret;
-	OM_uint32 min;
-	gss_name_t srv_name;
-	gss_buffer_desc input_name;
-	gss_buffer_desc *p_tok_in;
-	gss_buffer_desc tok_out, tok_in;
 	DATA_BLOB blob_out = data_blob_null;
 	DATA_BLOB blob_in = data_blob_null;
-	OM_uint32 ret_flags = 0;
 	NTSTATUS status = NT_STATUS_OK;
 
-	memset(&tok_out, '\0', sizeof(tok_out));
-
-	/* Guess the realm based on the supplied service, and avoid the GSS libs
-	   doing DNS lookups which may fail.
-
-	   TODO: Loop with the KDC on some more combinations (local
-	   realm in particular), possibly falling back to
-	   GSS_C_NT_HOSTBASED_SERVICE
-	*/
-	input_name.value = kerberos_get_principal_from_service_hostname(talloc_tos(),
-									 service, host);
-	if (!input_name.value) {
-		return NT_STATUS_NO_MEMORY;
-	}
-	input_name.length = strlen((char *)input_name.value);
-	ret = gss_import_name(&min, &input_name,
-			      GSS_C_NT_USER_NAME,
-			      &srv_name);
-	if (ret != GSS_S_COMPLETE) {
-		TALLOC_FREE(input_name.value);
-		return map_nt_error_from_gss(ret, min);
-	}
-
 	if (spnego_blob_in.length == 0) {
-		p_tok_in = GSS_C_NO_BUFFER;
+		blob_in = spnego_blob_in;
 	} else {
 		/* Remove the SPNEGO wrapper */
 		if (!spnego_parse_auth_response(ctx, spnego_blob_in, status_in, OID_KERBEROS5, &blob_in)) {
 			status = NT_STATUS_UNSUCCESSFUL;
 			goto fail;
 		}
-		tok_in.value = blob_in.data;
-		tok_in.length = blob_in.length;
-		p_tok_in = &tok_in;
-	}
-
-	ret = gss_init_sec_context(&min,
-				GSS_C_NO_CREDENTIAL, /* Use our default cred. */
-				&es->s.gss_state->gss_ctx,
-				srv_name,
-				GSS_C_NO_OID, /* default OID. */
-				GSS_C_MUTUAL_FLAG | GSS_C_REPLAY_FLAG | GSS_C_SEQUENCE_FLAG | GSS_C_DELEG_FLAG,
-				GSS_C_INDEFINITE,	/* requested ticket lifetime. */
-				NULL,   /* no channel bindings */
-				p_tok_in,
-				NULL,   /* ignore mech type */
-				&tok_out,
-				&ret_flags,
-				NULL);  /* ignore time_rec */
-
-	status = map_nt_error_from_gss(ret, min);
-	if (!NT_STATUS_IS_OK(status) && !NT_STATUS_EQUAL(status,NT_STATUS_MORE_PROCESSING_REQUIRED)) {
-		ADS_STATUS adss = ADS_ERROR_GSS(ret, min);
-		DEBUG(10,("make_cli_gss_blob: gss_init_sec_context failed with %s\n",
-			ads_errstr(adss)));
-		goto fail;
-	}
-
-	if ((ret_flags & SMB_GSS_REQUIRED_FLAGS) != SMB_GSS_REQUIRED_FLAGS) {
-		status = NT_STATUS_ACCESS_DENIED;
 	}
 
-	blob_out = data_blob_talloc(ctx, tok_out.value, tok_out.length);
+	status = gensec_update(gensec_security, ctx,
+			       NULL, blob_in, &blob_out);
 
 	/* Wrap in an SPNEGO wrapper */
 	*p_blob_out = spnego_gen_negTokenInit(ctx, krb_mechs, &blob_out, NULL);
@@ -784,11 +709,6 @@ static NTSTATUS make_cli_gss_blob(TALLOC_CTX *ctx,
 
 	data_blob_free(&blob_out);
 	data_blob_free(&blob_in);
-	TALLOC_FREE(input_name.value);
-	gss_release_name(&min, &srv_name);
-	if (tok_out.value) {
-		gss_release_buffer(&min, &tok_out);
-	}
 	return status;
 }
 
@@ -802,16 +722,41 @@ NTSTATUS cli_gss_smb_encryption_start(struct cli_state *cli)
 	DATA_BLOB blob_send = data_blob_null;
 	DATA_BLOB param_out = data_blob_null;
 	NTSTATUS status = NT_STATUS_UNSUCCESSFUL;
-	fstring fqdn;
-	const char *servicename;
+	struct auth_generic_state *auth_generic_state;
 	struct smb_trans_enc_state *es = make_cli_enc_state(SMB_TRANS_ENC_GSS);
 
 	if (!es) {
 		return NT_STATUS_NO_MEMORY;
 	}
 
-	servicename = "cifs";
-	status = make_cli_gss_blob(talloc_tos(), es, servicename, cli_state_remote_name(cli), NT_STATUS_OK, blob_recv, &blob_send);
+	status = auth_generic_client_prepare(NULL,
+					     &auth_generic_state);
+	if (!NT_STATUS_IS_OK(status)) {
+		goto fail;
+	}
+
+	gensec_want_feature(auth_generic_state->gensec_security, GENSEC_FEATURE_SESSION_KEY);
+	gensec_want_feature(auth_generic_state->gensec_security, GENSEC_FEATURE_SEAL);
+
+	cli_credentials_set_kerberos_state(auth_generic_state->credentials, 
+					   CRED_MUST_USE_KERBEROS);
+
+	status = gensec_set_target_service(auth_generic_state->gensec_security, "cifs");
+	if (!NT_STATUS_IS_OK(status)) {
+		goto fail;
+	}
+
+	status = gensec_set_target_hostname(auth_generic_state->gensec_security, 
+					    cli_state_remote_name(cli));
+	if (!NT_STATUS_IS_OK(status)) {
+		goto fail;
+	}
+
+	if (!NT_STATUS_IS_OK(status = auth_generic_client_start(auth_generic_state, GENSEC_OID_KERBEROS5))) {
+		goto fail;
+	}
+
+	status = make_cli_gss_blob(talloc_tos(), auth_generic_state->gensec_security, NT_STATUS_OK, blob_recv, &blob_send);
 	do {
 		data_blob_free(&blob_recv);
 		status = enc_blob_send_receive(cli, &blob_send, &blob_recv, &param_out);
@@ -819,25 +764,34 @@ NTSTATUS cli_gss_smb_encryption_start(struct cli_state *cli)
 			es->enc_ctx_num = SVAL(param_out.data, 0);
 		}
 		data_blob_free(&blob_send);
-		status = make_cli_gss_blob(talloc_tos(), es, servicename, fqdn, status, blob_recv, &blob_send);
+		status = make_cli_gss_blob(talloc_tos(), auth_generic_state->gensec_security, status, blob_recv, &blob_send);
 	} while (NT_STATUS_EQUAL(status, NT_STATUS_MORE_PROCESSING_REQUIRED));
 	data_blob_free(&blob_recv);
 
 	if (NT_STATUS_IS_OK(status)) {
+		if (!gensec_have_feature(auth_generic_state->gensec_security, 
+					 GENSEC_FEATURE_SIGN) ||
+		    !gensec_have_feature(auth_generic_state->gensec_security, 
+					 GENSEC_FEATURE_SEAL)) {
+			status = NT_STATUS_ACCESS_DENIED;
+		}
+	}
+
+	if (NT_STATUS_IS_OK(status)) {
 		es->enc_on = true;
 		/* Replace the old state, if any. */
+		/* We only need the gensec_security part from here.
+		 * es is a malloc()ed pointer, so we cannot make
+		 * gensec_security a talloc child */
+		es->s.gensec_security = talloc_move(NULL,
+					&auth_generic_state->gensec_security);
 		smb1cli_conn_set_encryption(cli->conn, es);
 		es = NULL;
 	}
+fail:
 	common_free_encryption_state(&es);
 	return status;
 }
-#else
-NTSTATUS cli_gss_smb_encryption_start(struct cli_state *cli)
-{
-	return NT_STATUS_NOT_SUPPORTED;
-}
-#endif
 
 /********************************************************************
  Ensure a connection is encrypted.
diff --git a/source3/smbd/seal.c b/source3/smbd/seal.c
index 41d1765189..28bf688924 100644
--- a/source3/smbd/seal.c
+++ b/source3/smbd/seal.c
@@ -86,125 +86,25 @@ static NTSTATUS make_auth_gensec(const struct tsocket_address *remote_address,
 
 	gensec_want_feature(gensec_security, GENSEC_FEATURE_SEAL);
 
-	status = gensec_start_mech_by_oid(gensec_security, oid);
-
-	if (!NT_STATUS_IS_OK(status)) {
-		TALLOC_FREE(gensec_security);
-		return nt_status_squash(status);
-	}
-
-	es->s.gensec_security = gensec_security;
-
-	return status;
-}
-
-#if defined(HAVE_GSSAPI) && defined(HAVE_KRB5)
-
-/******************************************************************************
- Import a name.
-******************************************************************************/
-
-static NTSTATUS get_srv_gss_creds(const char *service,
-				const char *name,
-				gss_cred_usage_t cred_type,
-				gss_cred_id_t *p_srv_cred)
-{
-	OM_uint32 ret;
-	OM_uint32 min;
-	gss_name_t srv_name;
-	gss_buffer_desc input_name;
-	char *host_princ_s = NULL;
-	NTSTATUS status = NT_STATUS_OK;
-
-	gss_OID_desc nt_hostbased_service =
-	{10, discard_const_p(char, "\x2a\x86\x48\x86\xf7\x12\x01\x02\x01\x04")};
-
-	if (asprintf(&host_princ_s, "%s@%s", service, name) == -1) {
-		return NT_STATUS_NO_MEMORY;
-	}
-
-	input_name.value = host_princ_s;
-	input_name.length = strlen(host_princ_s) + 1;
-
-	ret = gss_import_name(&min,
-				&input_name,
-				&nt_hostbased_service,
-				&srv_name);
-
-	DEBUG(10,("get_srv_gss_creds: imported name %s\n",
-		host_princ_s ));
-
-	if (ret != GSS_S_COMPLETE) {
-		SAFE_FREE(host_princ_s);
-		return map_nt_error_from_gss(ret, min);
-	}
-
 	/*
-	 * We're accessing the krb5.keytab file here.
+	 * We could be accessing the secrets.tdb or krb5.keytab file here.
  	 * ensure we have permissions to do so.
  	 */
 	become_root();
 
-	ret = gss_acquire_cred(&min,
-				srv_name,
-				GSS_C_INDEFINITE,
-				GSS_C_NULL_OID_SET,
-				cred_type,
-				p_srv_cred,
-				NULL,
-				NULL);
-	unbecome_root();
-
-	if (ret != GSS_S_COMPLETE) {
-		ADS_STATUS adss = ADS_ERROR_GSS(ret, min);
-		DEBUG(10,("get_srv_gss_creds: gss_acquire_cred failed with %s\n",
-			ads_errstr(adss)));
-		status = map_nt_error_from_gss(ret, min);
-	}
-
-	SAFE_FREE(host_princ_s);
-	gss_release_name(&min, &srv_name);
-	return status;
-}
-
-/******************************************************************************
- Create a gss state.
- Try and get the cifs/server@realm principal first, then fall back to
- host/server@realm.
-******************************************************************************/
-
-static NTSTATUS make_auth_gss(struct smb_trans_enc_state *es)
-{
-	NTSTATUS status;
-	gss_cred_id_t srv_cred;
-	fstring fqdn;
+	status = gensec_start_mech_by_oid(gensec_security, oid);
 
-	name_to_fqdn(fqdn, lp_netbios_name());
-	strlower_m(fqdn);
+	unbecome_root();
 
-	status = get_srv_gss_creds("cifs", fqdn, GSS_C_ACCEPT, &srv_cred);
 	if (!NT_STATUS_IS_OK(status)) {
-		status = get_srv_gss_creds("host", fqdn, GSS_C_ACCEPT, &srv_cred);
-		if (!NT_STATUS_IS_OK(status)) {
-			return nt_status_squash(status);
-		}
-	}
-
-	es->s.gss_state = SMB_MALLOC_P(struct smb_tran_enc_state_gss);
-	if (!es->s.gss_state) {
-		OM_uint32 min;
-		gss_release_cred(&min, &srv_cred);
-		return NT_STATUS_NO_MEMORY;
+		TALLOC_FREE(gensec_security);
+		return nt_status_squash(status);
 	}
-	ZERO_STRUCTP(es->s.gss_state);
-	es->s.gss_state->creds = srv_cred;
 
-	/* No context yet. */
-	es->s.gss_state->gss_ctx = GSS_C_NO_CONTEXT;
+	es->s.gensec_security = gensec_security;
 
-	return NT_STATUS_OK;
+	return status;
 }
-#endif
 
 /******************************************************************************
  Shutdown a server encryption context.
@@ -232,6 +132,8 @@ static NTSTATUS make_srv_encryption_context(const struct tsocket_address *remote
 					    enum smb_trans_enc_type smb_enc_type,
 					    struct smb_trans_enc_state **pp_es)
 {
+	NTSTATUS status;
+	const char *oid;
 	struct smb_trans_enc_state *es;
 
 	*pp_es = NULL;
@@ -245,32 +147,21 @@ static NTSTATUS make_srv_encryption_context(const struct tsocket_address *remote
 	es->smb_enc_type = smb_enc_type;
 	switch (smb_enc_type) {
 		case SMB_TRANS_ENC_NTLM:
-			{
-				NTSTATUS status = make_auth_gensec(remote_address,
-								   es, GENSEC_OID_NTLMSSP);
-				if (!NT_STATUS_IS_OK(status)) {
-					srv_free_encryption_context(&es);
-					return status;
-				}
-			}
+			oid = GENSEC_OID_NTLMSSP;
 			break;
-
-#if defined(HAVE_GSSAPI) && defined(HAVE_KRB5)
 		case SMB_TRANS_ENC_GSS:
-			/* Acquire our credentials by calling gss_acquire_cred here. */
-			{
-				NTSTATUS status = make_auth_gss(es);
-				if (!NT_STATUS_IS_OK(status)) {
-					srv_free_encryption_context(&es);
-					return status;
-				}
-			}
+			oid = GENSEC_OID_KERBEROS5;
 			break;
-#endif
 		default:
 			srv_free_encryption_context(&es);
 			return NT_STATUS_INVALID_PARAMETER;
 	}
+	status = make_auth_gensec(remote_address,
+				  es, oid);
+	if (!NT_STATUS_IS_OK(status)) {
+		srv_free_encryption_context(&es);
+		return status;
+	}
 	*pp_es = es;
 	return NT_STATUS_OK;
 }
@@ -338,75 +229,35 @@ NTSTATUS srv_encrypt_buffer(struct smbd_server_connection *sconn, char *buf,
  Until success we do everything on the partial enc ctx.
 ******************************************************************************/
 
-#if defined(HAVE_GSSAPI) && defined(HAVE_KRB5)
 static NTSTATUS srv_enc_spnego_gss_negotiate(const struct tsocket_address *remote_address,
 					     unsigned char **ppdata,
 					     size_t *p_data_size,
 					     DATA_BLOB secblob)
 {
-	OM_uint32 ret;
-	OM_uint32 min;
-	OM_uint32 flags = 0;
-	gss_buffer_desc in_buf, out_buf;
-	struct smb_tran_enc_state_gss *gss_state;
-	DATA_BLOB auth_reply = data_blob_null;
-	DATA_BLOB response = data_blob_null;
 	NTSTATUS status;
+	DATA_BLOB unwrapped_response = data_blob_null;
+	DATA_BLOB response = data_blob_null;
 
-	if (!partial_srv_trans_enc_ctx) {
-		status = make_srv_encryption_context(remote_address,
-						     SMB_TRANS_ENC_GSS,
-						     &partial_srv_trans_enc_ctx);
-		if (!NT_STATUS_IS_OK(status)) {
-			return status;
-		}
+	status = make_srv_encryption_context(remote_address,
+					     SMB_TRANS_ENC_GSS,
+					     &partial_srv_trans_enc_ctx);
+	if (!NT_STATUS_IS_OK(status)) {
+		return status;
 	}
 
-	gss_state = partial_srv_trans_enc_ctx->s.gss_state;
-
-	in_buf.value = secblob.data;
-	in_buf.length = secblob.length;
-
-	out_buf.value = NULL;
-	out_buf.length = 0;
-
 	become_root();
 
-	ret = gss_accept_sec_context(&min,
-				&gss_state->gss_ctx,
-				gss_state->creds,
-				&in_buf,
-				GSS_C_NO_CHANNEL_BINDINGS,
-				NULL,
-				NULL,		/* Ignore oids. */
-				&out_buf,	/* To return. */
-				&flags,
-				NULL,		/* Ingore time. */
-				NULL);		/* Ignore delegated creds. */
-	unbecome_root();
-
-	status = gss_err_to_ntstatus(ret, min);
-	if (ret != GSS_S_COMPLETE && ret != GSS_S_CONTINUE_NEEDED) {
-		return status;
-	}
+	status = gensec_update(partial_srv_trans_enc_ctx->s.gensec_security,
+			       talloc_tos(), NULL,
+			       secblob, &unwrapped_response);
 
-	/* Ensure we've got sign+seal available. */
-	if (ret == GSS_S_COMPLETE) {
-		if ((flags & (GSS_C_INTEG_FLAG|GSS_C_CONF_FLAG|GSS_C_REPLAY_FLAG|GSS_C_SEQUENCE_FLAG)) !=
-				(GSS_C_INTEG_FLAG|GSS_C_CONF_FLAG|GSS_C_REPLAY_FLAG|GSS_C_SEQUENCE_FLAG)) {
-			DEBUG(0,("srv_enc_spnego_gss_negotiate: quality of service not good enough "
-				"for SMB sealing.\n"));
-			gss_release_buffer(&min, &out_buf);
-			return NT_STATUS_ACCESS_DENIED;
-		}
-	}
+	unbecome_root();
 
-	auth_reply = data_blob(out_buf.value, out_buf.length);
-	gss_release_buffer(&min, &out_buf);
+	/* status here should be NT_STATUS_MORE_PROCESSING_REQUIRED
+	 * for success ... */
 
-	/* Wrap in SPNEGO. */
-	response = spnego_gen_auth_response(talloc_tos(), &auth_reply, status, OID_KERBEROS5);
-	data_blob_free(&auth_reply);
+	response = spnego_gen_auth_response(talloc_tos(), &unwrapped_response, status, OID_KERBEROS5);
+	data_blob_free(&unwrapped_response);
 
 	SAFE_FREE(*ppdata);
 	*ppdata = (unsigned char *)memdup(response.data, response.length);
@@ -414,12 +265,10 @@ static NTSTATUS srv_enc_spnego_gss_negotiate(const struct tsocket_address *remot
 		status = NT_STATUS_NO_MEMORY;
 	}
 	*p_data_size = response.length;
-
 	data_blob_free(&response);
 
 	return status;
 }
-#endif
 
 /******************************************************************************
  Do the NTLM SPNEGO (or raw) encryption negotiation. Parameters are in/out.
@@ -500,16 +349,10 @@ static NTSTATUS srv_enc_spnego_negotiate(connection_struct *conn,
 	if (kerb_mech) {
 		TALLOC_FREE(kerb_mech);
 
-#if defined(HAVE_GSSAPI) && defined(HAVE_KRB5)
 		status = srv_enc_spnego_gss_negotiate(conn->sconn->remote_address,
 						      ppdata,
 						      p_data_size,
 						      secblob);
-#else
-		/* Currently we don't SPNEGO negotiate
-		 * back to NTLMSSP as we do in sessionsetupX. We should... */
-		return NT_STATUS_LOGON_FAILURE;
-#endif
 	} else {
 		status = srv_enc_ntlm_negotiate(conn->sconn->remote_address,
 						ppdata,