Add cert_create tool support for RSA key sizes

cert_tool is now able to accept a command line option for specifying the
key size. It now supports the following options: 1024, 2048 (default),
3072 and 4096. This is also modifiable by TFA using the build flag
KEY_SIZE.

Change-Id: Ifadecf84ade3763249ee8cc7123a8178f606f0e5
Signed-off-by: Justin Chadwell <justin.chadwell@arm.com>

make_helpers/tbbr/tbbr_tools.mk

 #
-# Copyright (c) 2015-2018, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -21,6 +21,7 @@
 # Build options added by this file:
 #
 #   KEY_ALG
+#   KEY_SIZE
 #   ROT_KEY
 #   TRUSTED_WORLD_KEY
 #   NON_TRUSTED_WORLD_KEY
@@ -52,6 +53,7 @@ $(eval $(call TOOL_ADD_PAYLOAD,${FWU_CERT},--fwu-cert,,FWU_))
 # packed in the FIP). Developers can use their own keys by specifying the proper
 # build option in the command line when building the Trusted Firmware
 $(if ${KEY_ALG},$(eval $(call CERT_ADD_CMD_OPT,${KEY_ALG},--key-alg)))
+$(if ${KEY_SIZE},$(eval $(call CERT_ADD_CMD_OPT,${KEY_SIZE},--key-size)))
 $(if ${HASH_ALG},$(eval $(call CERT_ADD_CMD_OPT,${HASH_ALG},--hash-alg)))
 $(if ${ROT_KEY},$(eval $(call CERT_ADD_CMD_OPT,${ROT_KEY},--rot-key)))
 $(if ${ROT_KEY},$(eval $(call CERT_ADD_CMD_OPT,${ROT_KEY},--rot-key,FWU_)))

tools/cert_create/include/key.h

 /*
- * Copyright (c) 2015-2017, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -9,8 +9,6 @@
 
 #include <openssl/ossl_typ.h>
 
-#define RSA_KEY_BITS		2048
-
 /* Error codes */
 enum {
 	KEY_ERR_NONE,
@@ -30,6 +28,9 @@ enum {
 	KEY_ALG_MAX_NUM
 };
 
+/* Maximum number of valid key sizes per algorithm */
+#define KEY_SIZE_MAX_NUM	4
+
 /* Supported hash algorithms */
 enum{
 	HASH_ALG_SHA256,
@@ -37,6 +38,16 @@ enum{
 	HASH_ALG_SHA512,
 };
 
+/* Supported key sizes */
+/* NOTE: the first item in each array is the default key size */
+static const unsigned int KEY_SIZES[KEY_ALG_MAX_NUM][KEY_SIZE_MAX_NUM] = {
+	{ 2048, 1024, 3072, 4096 },	/* KEY_ALG_RSA */
+	{ 2048, 1024, 3072, 4096 },	/* KEY_ALG_RSA_1_5 */
+#ifndef OPENSSL_NO_EC
+	{}				/* KEY_ALG_ECDSA */
+#endif /* OPENSSL_NO_EC */
+};
+
 /*
  * This structure contains the relevant information to create the keys
  * required to sign the certificates.
@@ -58,7 +69,7 @@ typedef struct key_s {
 int key_init(void);
 key_t *key_get_by_opt(const char *opt);
 int key_new(key_t *key);
-int key_create(key_t *key, int type);
+int key_create(key_t *key, int type, int key_bits);
 int key_load(key_t *key, unsigned int *err_code);
 int key_store(key_t *key);
 

tools/cert_create/src/key.c

@@ -41,7 +41,7 @@ int key_new(key_t *key)
 	return 1;
 }
 
-static int key_create_rsa(key_t *key)
+static int key_create_rsa(key_t *key, int key_bits)
 {
 	BIGNUM *e;
 	RSA *rsa = NULL;
@@ -63,7 +63,7 @@ static int key_create_rsa(key_t *key)
 		goto err;
 	}
 
-	if (!RSA_generate_key_ex(rsa, RSA_KEY_BITS, e, NULL)) {
+	if (!RSA_generate_key_ex(rsa, key_bits, e, NULL)) {
 		printf("Cannot generate RSA key\n");
 		goto err;
 	}
@@ -82,7 +82,7 @@ err:
 }
 
 #ifndef OPENSSL_NO_EC
-static int key_create_ecdsa(key_t *key)
+static int key_create_ecdsa(key_t *key, int key_bits)
 {
 	EC_KEY *ec;
 
@@ -109,7 +109,7 @@ err:
 }
 #endif /* OPENSSL_NO_EC */
 
-typedef int (*key_create_fn_t)(key_t *key);
+typedef int (*key_create_fn_t)(key_t *key, int key_bits);
 static const key_create_fn_t key_create_fn[KEY_ALG_MAX_NUM] = {
 	key_create_rsa, 	/* KEY_ALG_RSA */
 	key_create_rsa, 	/* KEY_ALG_RSA_1_5 */
@@ -118,7 +118,7 @@ static const key_create_fn_t key_create_fn[KEY_ALG_MAX_NUM] = {
 #endif /* OPENSSL_NO_EC */
 };
 
-int key_create(key_t *key, int type)
+int key_create(key_t *key, int type, int key_bits)
 {
 	if (type >= KEY_ALG_MAX_NUM) {
 		printf("Invalid key type\n");
@@ -126,7 +126,7 @@ int key_create(key_t *key, int type)
 	}
 
 	if (key_create_fn[type]) {
-		return key_create_fn[type](key);
+		return key_create_fn[type](key, key_bits);
 	}
 
 	return 0;

tools/cert_create/src/main.c

@@ -10,6 +10,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <stdbool.h>
 
 #include <openssl/conf.h>
 #include <openssl/engine.h>
@@ -69,6 +70,7 @@
 /* Global options */
 static int key_alg;
 static int hash_alg;
+static int key_size;
 static int new_keys;
 static int save_keys;
 static int print_cert;
@@ -155,6 +157,18 @@ static int get_key_alg(const char *key_alg_str)
 	return -1;
 }
 
+static int get_key_size(const char *key_size_str)
+{
+	char *end;
+	long key_size;
+
+	key_size = strtol(key_size_str, &end, 10);
+	if (*end != '\0')
+		return -1;
+
+	return key_size;
+}
+
 static int get_hash_alg(const char *hash_alg_str)
 {
 	int i;
@@ -174,6 +188,7 @@ static void check_cmd_params(void)
 	ext_t *ext;
 	key_t *key;
 	int i, j;
+	bool valid_size;
 
 	/* Only save new keys */
 	if (save_keys && !new_keys) {
@@ -181,6 +196,26 @@ static void check_cmd_params(void)
 		exit(1);
 	}
 
+	/* Validate key-size */
+	valid_size = false;
+	for (i = 0; i < KEY_SIZE_MAX_NUM; i++) {
+		if (key_size == KEY_SIZES[key_alg][i]) {
+			valid_size = true;
+			break;
+		}
+	}
+	if (!valid_size) {
+		ERROR("'%d' is not a valid key size for '%s'\n",
+				key_size, key_algs_str[key_alg]);
+		NOTICE("Valid sizes are: ");
+		for (i = 0; i < KEY_SIZE_MAX_NUM &&
+				KEY_SIZES[key_alg][i] != 0; i++) {
+			printf("%d ", KEY_SIZES[key_alg][i]);
+		}
+		printf("\n");
+		exit(1);
+	}
+
 	/* Check that all required options have been specified in the
 	 * command line */
 	for (i = 0; i < num_certs; i++) {
@@ -245,6 +280,10 @@ static const cmd_opt_t common_cmd_opt[] = {
 		"Key algorithm: 'rsa' (default) - RSAPSS scheme as per \
 PKCS#1 v2.1, 'rsa_1_5' - RSA PKCS#1 v1.5, 'ecdsa'"
 	},
+	{
+		{ "key-size", required_argument, NULL, 'b' },
+		"Key size (for supported algorithms)."
+	},
 	{
 		{ "hash-alg", required_argument, NULL, 's' },
 		"Hash algorithm : 'sha256' (default), 'sha384', 'sha512'"
@@ -286,6 +325,7 @@ int main(int argc, char *argv[])
 	/* Set default options */
 	key_alg = KEY_ALG_RSA;
 	hash_alg = HASH_ALG_SHA256;
+	key_size = -1;
 
 	/* Add common command line options */
 	for (i = 0; i < NUM_ELEM(common_cmd_opt); i++) {
@@ -315,7 +355,7 @@ int main(int argc, char *argv[])
 
 	while (1) {
 		/* getopt_long stores the option index here. */
-		c = getopt_long(argc, argv, "a:hknps:", cmd_opt, &opt_idx);
+		c = getopt_long(argc, argv, "a:b:hknps:", cmd_opt, &opt_idx);
 
 		/* Detect the end of the options. */
 		if (c == -1) {
@@ -330,6 +370,13 @@ int main(int argc, char *argv[])
 				exit(1);
 			}
 			break;
+		case 'b':
+			key_size = get_key_size(optarg);
+			if (key_size <= 0) {
+				ERROR("Invalid key size '%s'\n", optarg);
+				exit(1);
+			}
+			break;
 		case 'h':
 			print_help(argv[0], cmd_opt);
 			exit(0);
@@ -371,6 +418,11 @@ int main(int argc, char *argv[])
 		}
 	}
 
+	/* Select a reasonable default key-size */
+	if (key_size == -1) {
+		key_size = KEY_SIZES[key_alg][0];
+	}
+
 	/* Check command line arguments */
 	check_cmd_params();
 
@@ -413,7 +465,7 @@ int main(int argc, char *argv[])
 		if (new_keys) {
 			/* Try to create a new key */
 			NOTICE("Creating new key for '%s'\n", keys[i].desc);
-			if (!key_create(&keys[i], key_alg)) {
+			if (!key_create(&keys[i], key_alg, key_size)) {
 				ERROR("Error creating key '%s'\n", keys[i].desc);
 				exit(1);
 			}