TBB: add authentication module interface

This patch provides an API to access the authentication module that
will be used to verify the authenticity of the images loaded into
memory as part of the Trusted Board Boot process.

To include the authentication module as part of the build, set the
boolean build option TRUSTED_BOARD_BOOT. One single authentication
module must be registered at build time by setting the build option
AUTH_MOD=<mod_name>. All authentication modules will be located in
'common/auth/<mod_name>' and must present the <mod_name>.mk file that
will be included by the build system to compile the module sources.

To create an authentication module, an instance of auth_mod_t called
'auth_mod' must be declared in the module sources. The initialization
and verification functions provided by the module will be exported
through the function pointers specified when declaring this instance.

If an authentication module includes third party sources that do not
adhere to the C99 standard, the -pedantic option may be removed from
the build options by setting the flag DISABLE_PEDANTIC in the module
file <mod_name>.mk.

Change-Id: I080bb04bd421029bcdf22ec2c63807afbf061dcd

Makefile

@@ -74,6 +74,7 @@ GENERATE_COT		:= 0
 CREATE_KEYS		:= 1
 # Flags to build TF with Trusted Boot support
 TRUSTED_BOARD_BOOT	:= 0
+AUTH_MOD		:= none
 
 # Checkpatch ignores
 CHECK_IGNORE		=	--ignore COMPLEX_MACRO
@@ -306,6 +307,23 @@ ifneq (${GENERATE_COT},0)
     $(eval CRT_ARGS += --trusted-key-cert ${TRUSTED_KEY_CERT})
 endif
 
+# Check Trusted Board Boot options
+ifneq (${TRUSTED_BOARD_BOOT},0)
+    ifeq (${AUTH_MOD},none)
+        $(error Error: When TRUSTED_BOARD_BOOT=1, AUTH_MOD has to be the name of a valid authentication module)
+    else
+        # We expect to locate an *.mk file under the specified AUTH_MOD directory
+        AUTH_MAKE := $(shell m="common/auth/${AUTH_MOD}/${AUTH_MOD}.mk"; [ -f "$$m" ] && echo "$$m")
+        ifeq (${AUTH_MAKE},)
+            $(error Error: No common/auth/${AUTH_MOD}/${AUTH_MOD}.mk located)
+        endif
+        $(info Including ${AUTH_MAKE})
+        include ${AUTH_MAKE}
+    endif
+
+    BL_COMMON_SOURCES	+=	common/auth.c
+endif
+
 # Check if -pedantic option should be used
 ifeq (${DISABLE_PEDANTIC},0)
     CFLAGS		+= 	-pedantic

common/auth.c

@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2015, ARM Limited and Contributors. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * Neither the name of ARM nor the names of its contributors may be used
+ * to endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <assert.h>
+#include <auth.h>
+#include <debug.h>
+
+/*
+ * Initialize the authentication module
+ */
+void auth_init(void)
+{
+	assert(auth_mod.name);
+	assert(auth_mod.init);
+	assert(auth_mod.verify);
+
+	INFO("Using authentication module '%s'\n", auth_mod.name);
+	if (auth_mod.init() != 0)
+		assert(0);
+}
+
+/*
+ * Authenticate a certificate/image
+ *
+ * Return: 0 = success, Otherwise = error
+ */
+int auth_verify_obj(unsigned int obj_id, uintptr_t obj_buf, size_t len)
+{
+	assert(obj_id < AUTH_NUM_OBJ);
+	assert(obj_buf != 0);
+	assert(auth_mod.verify);
+
+	return auth_mod.verify(obj_id, obj_buf, len);
+}

include/common/auth.h

@@ -0,0 +1,88 @@
+/*
+ * Copyright (c) 2015, ARM Limited and Contributors. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * Neither the name of ARM nor the names of its contributors may be used
+ * to endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef AUTH_H_
+#define AUTH_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+/*
+ * Authentication infrastructure for Trusted Boot
+ *
+ * This infrastructure provides an API to access the authentication module. This
+ * module will implement the required operations for Trusted Boot by creating an
+ * instance of the structure 'auth_mod_t'. This instance must be called
+ * 'auth_mod' and must provide the functions to initialize the module and
+ * verify the authenticity of the images.
+ */
+
+/* Objects (images and certificates) involved in the TBB process */
+enum {
+	AUTH_BL2_IMG_CERT,
+	AUTH_BL2_IMG,
+	AUTH_TRUSTED_KEY_CERT,
+	AUTH_BL30_KEY_CERT,
+	AUTH_BL30_IMG_CERT,
+	AUTH_BL30_IMG,
+	AUTH_BL31_KEY_CERT,
+	AUTH_BL31_IMG_CERT,
+	AUTH_BL31_IMG,
+	AUTH_BL32_KEY_CERT,
+	AUTH_BL32_IMG_CERT,
+	AUTH_BL32_IMG,
+	AUTH_BL33_KEY_CERT,
+	AUTH_BL33_IMG_CERT,
+	AUTH_BL33_IMG,
+	AUTH_NUM_OBJ
+};
+
+/* Authentication module structure */
+typedef struct auth_mod_s {
+	/* [mandatory] Module name. Printed to the log during initialization */
+	const char *name;
+
+	/* [mandatory] Initialize the authentication module */
+	int (*init)(void);
+
+	/* [mandatory] This function will be called to authenticate a new
+	 * object loaded into memory. The obj_id corresponds to one of the
+	 * values in the enumeration above */
+	int (*verify)(unsigned int obj_id, uintptr_t obj_buf, size_t len);
+} auth_mod_t;
+
+/* This variable must be instantiated by the authentication module */
+extern const auth_mod_t auth_mod;
+
+/* Public functions */
+void auth_init(void);
+int auth_verify_obj(unsigned int obj_id, uintptr_t obj_buf, size_t len);
+
+#endif /* AUTH_H_ */