Merge pull request #1080 from soby-mathew/eb/RSA-PKCS1-5_support_1

Support legacy RSA PKCS#1 v1.5 in cert create

docs/user-guide.rst

@@ -405,6 +405,13 @@ Common build options
    AArch64 and facilitates the loading of ``SP_MIN`` and BL33 as AArch32 executable
    images.
 
+-  ``KEY_ALG``: This build flag enables the user to select the algorithm to be
+   used for generating the PKCS keys and subsequent signing of the certificate.
+   It accepts 3 values viz ``rsa``, ``rsa_1_5``, ``ecdsa``. The ``rsa_1_5`` is
+   the legacy PKCS#1 RSA 1.5 algorithm which is not TBBR compliant and is
+   retained only for compatibility. The default value of this flag is ``rsa``
+   which is the TBBR compliant PKCS#1 RSA 2.1 scheme.
+
 -  ``LDFLAGS``: Extra user options appended to the linkers' command line in
    addition to the one set by the build system.
 

drivers/auth/mbedtls/mbedtls_crypto.mk

@@ -7,9 +7,15 @@
 include drivers/auth/mbedtls/mbedtls_common.mk
 
 # The platform may define the variable 'TF_MBEDTLS_KEY_ALG' to select the key
-# algorithm to use. Default algorithm is RSA.
+# algorithm to use. If the variable is not defined, select it based on algorithm
+# used for key generation `KEY_ALG`. If `KEY_ALG` is not defined or is
+# defined to `rsa`/`rsa_1_5`, then set the variable to `rsa`.
 ifeq (${TF_MBEDTLS_KEY_ALG},)
+    ifeq (${KEY_ALG}, ecdsa)
+        TF_MBEDTLS_KEY_ALG		:=	ecdsa
+    else
         TF_MBEDTLS_KEY_ALG		:=	rsa
+    endif
 endif
 
 # If MBEDTLS_KEY_ALG build flag is defined use it to set TF_MBEDTLS_KEY_ALG for

make_helpers/defaults.mk

@@ -81,6 +81,9 @@ GENERATE_COT			:= 0
 # operations.
 HW_ASSISTED_COHERENCY		:= 0
 
+# Set the default algorithm for the generation of Trusted Board Boot keys
+KEY_ALG				:= rsa
+
 # Flag to enable new version of image loading
 LOAD_IMAGE_V2			:= 0
 

plat/arm/common/arm_common.mk

@@ -174,9 +174,6 @@ endif
 
 ifneq (${TRUSTED_BOARD_BOOT},0)
 
-    # By default, ARM platforms use RSA keys
-    KEY_ALG		:=	rsa
-
     # Include common TBB sources
     AUTH_SOURCES	:=	drivers/auth/auth_mod.c				\
 				drivers/auth/crypto_mod.c			\
@@ -195,8 +192,6 @@ ifneq (${TRUSTED_BOARD_BOOT},0)
 
     $(eval $(call FWU_FIP_ADD_IMG,NS_BL2U,--fwu))
 
-    TF_MBEDTLS_KEY_ALG	:=	${KEY_ALG}
-
     # We expect to locate the *.mk files under the directories specified below
 ifeq (${ARM_CRYPTOCELL_INTEG},0)
     CRYPTO_LIB_MK := drivers/auth/mbedtls/mbedtls_crypto.mk

tools/cert_create/include/cert.h

@@ -48,7 +48,7 @@ struct cert_s {
 int cert_init(void);
 cert_t *cert_get_by_opt(const char *opt);
 int cert_add_ext(X509 *issuer, X509 *subject, int nid, char *value);
-int cert_new(cert_t *cert, int days, int ca, STACK_OF(X509_EXTENSION) * sk);
+int cert_new(int key_alg, cert_t *cert, int days, int ca, STACK_OF(X509_EXTENSION) * sk);
 
 /* Macro to register the certificates used in the CoT */
 #define REGISTER_COT(_certs) \

tools/cert_create/include/key.h

@@ -22,7 +22,8 @@ enum {
 
 /* Supported key algorithms */
 enum {
-	KEY_ALG_RSA,
+	KEY_ALG_RSA,		/* RSA PSS as defined by PKCS#1 v2.1 (default) */
+	KEY_ALG_RSA_1_5,	/* RSA as defined by PKCS#1 v1.5 */
 #ifndef OPENSSL_NO_EC
 	KEY_ALG_ECDSA,
 #endif /* OPENSSL_NO_EC */

tools/cert_create/src/cert.c

@@ -79,7 +79,7 @@ int cert_add_ext(X509 *issuer, X509 *subject, int nid, char *value)
 	return 1;
 }
 
-int cert_new(cert_t *cert, int days, int ca, STACK_OF(X509_EXTENSION) * sk)
+int cert_new(int key_alg, cert_t *cert, int days, int ca, STACK_OF(X509_EXTENSION) * sk)
 {
 	EVP_PKEY *pkey = keys[cert->key].key;
 	cert_t *issuer_cert = &certs[cert->issuer];
@@ -112,11 +112,18 @@ int cert_new(cert_t *cert, int days, int ca, STACK_OF(X509_EXTENSION) * sk)
 	}
 
 	EVP_MD_CTX_init(&mdCtx);
+
+	/* Sign the certificate with the issuer key */
 	if (!EVP_DigestSignInit(&mdCtx, &pKeyCtx, EVP_sha256(), NULL, ikey)) {
 		ERR_print_errors_fp(stdout);
 		goto END;
 	}
 
+	/*
+	 * Set additional parameters if algorithm is RSA PSS. This is not
+	 * required for RSA 1.5 or ECDSA.
+	 */
+	if (key_alg == KEY_ALG_RSA) {
 		if (!EVP_PKEY_CTX_set_rsa_padding(pKeyCtx, RSA_PKCS1_PSS_PADDING)) {
 			ERR_print_errors_fp(stdout);
 			goto END;
@@ -131,6 +138,7 @@ int cert_new(cert_t *cert, int days, int ca, STACK_OF(X509_EXTENSION) * sk)
 			ERR_print_errors_fp(stdout);
 			goto END;
 		}
+	}
 
 	/* x509.v3 */
 	X509_set_version(x, 2);

tools/cert_create/src/main.c

@@ -89,6 +89,7 @@ static char *strdup(const char *str)
 
 static const char *key_algs_str[] = {
 	[KEY_ALG_RSA] = "rsa",
+	[KEY_ALG_RSA_1_5] = "rsa_1_5",
 #ifndef OPENSSL_NO_EC
 	[KEY_ALG_ECDSA] = "ecdsa"
 #endif /* OPENSSL_NO_EC */
@@ -223,7 +224,8 @@ static const cmd_opt_t common_cmd_opt[] = {
 	},
 	{
 		{ "key-alg", required_argument, NULL, 'a' },
-		"Key algorithm: 'rsa' (default), 'ecdsa'"
+		"Key algorithm: 'rsa' (default) - RSAPSS scheme as per \
+PKCS#1 v2.1, 'rsa_1_5' - RSA PKCS#1 v1.5, 'ecdsa'"
 	},
 	{
 		{ "save-keys", no_argument, NULL, 'k' },
@@ -450,8 +452,8 @@ int main(int argc, char *argv[])
 			sk_X509_EXTENSION_push(sk, cert_ext);
 		}
 
-		/* Create certificate. Signed with ROT key */
-		if (cert->fn && !cert_new(cert, VAL_DAYS, 0, sk)) {
+		/* Create certificate. Signed with corresponding key */
+		if (cert->fn && !cert_new(key_alg, cert, VAL_DAYS, 0, sk)) {
 			ERROR("Cannot create %s\n", cert->cn);
 			exit(1);
 		}