Remove RSA PKCS#1 v1.5 support from cert_tool

Support for PKCS#1 v1.5 was deprecated in SHA 1001202 and fully removed
in SHA fe199e3, however, cert_tool is still able to generate
certificates in that form. This patch fully removes the ability for
cert_tool to generate these certificates.

Additionally, this patch also fixes a bug where the issuing certificate
was a RSA and the issued certificate was EcDSA. In this case, the issued
certificate would be signed using PKCS#1 v1.5 instead of RSAPSS per
PKCS#1 v2.1, preventing TF-A from verifying the image signatures. Now
that PKCS#1 v1.5 support is removed, all certificates that are signed
with RSA now use the more modern padding scheme.

Change-Id: Id87d7d915be594a1876a73080528d968e65c4e9a
Signed-off-by: Justin Chadwell <justin.chadwell@arm.com>

7 files changed, 12 insertions, 21 deletions

diff --git a/docs/getting_started/user-guide.rst b/docs/getting_started/user-guide.rst
index 89157386..1229e663 100644
--- a/docs/getting_started/user-guide.rst
+++ b/docs/getting_started/user-guide.rst
@@ -588,10 +588,8 @@ Common build options
 
 -  ``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: ``rsa``, ``rsa_1_5`` and ``ecdsa``. The option
-   ``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.
+   It accepts 2 values: ``rsa`` and ``ecdsa``. The default value of this flag
+   is ``rsa`` which is the TBBR compliant PKCS#1 RSA 2.1 scheme.
 
 -  ``KEY_SIZE``: This build flag enables the user to select the key size for
    the algorithm specified by ``KEY_ALG``. The valid values for ``KEY_SIZE``
diff --git a/drivers/auth/mbedtls/mbedtls_common.mk b/drivers/auth/mbedtls/mbedtls_common.mk
index f34d3d00..4b830154 100644
--- a/drivers/auth/mbedtls/mbedtls_common.mk
+++ b/drivers/auth/mbedtls/mbedtls_common.mk
@@ -48,9 +48,9 @@ LIBMBEDTLS_SRCS		:= $(addprefix ${MBEDTLS_DIR}/library/,	\
 					)
 
 # The platform may define the variable 'TF_MBEDTLS_KEY_ALG' to select the key
-# 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`.
+# 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,
+# then it is set to `rsa`.
 ifeq (${TF_MBEDTLS_KEY_ALG},)
     ifeq (${KEY_ALG}, ecdsa)
         TF_MBEDTLS_KEY_ALG		:=	ecdsa
diff --git a/tools/cert_create/include/cert.h b/tools/cert_create/include/cert.h
index 39b45b58..6db9b579 100644
--- a/tools/cert_create/include/cert.h
+++ b/tools/cert_create/include/cert.h
@@ -1,5 +1,5 @@
 /*
- * 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
  */
@@ -49,7 +49,6 @@ 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(
-	int key_alg,
 	int md_alg,
 	cert_t *cert,
 	int days,
diff --git a/tools/cert_create/include/key.h b/tools/cert_create/include/key.h
index c08beb8b..d96d9839 100644
--- a/tools/cert_create/include/key.h
+++ b/tools/cert_create/include/key.h
@@ -21,7 +21,6 @@ enum {
 /* Supported key algorithms */
 enum {
 	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 */
@@ -42,7 +41,6 @@ enum{
 /* 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 */
diff --git a/tools/cert_create/src/cert.c b/tools/cert_create/src/cert.c
index 8e8aee69..c68a265b 100644
--- a/tools/cert_create/src/cert.c
+++ b/tools/cert_create/src/cert.c
@@ -1,5 +1,5 @@
 /*
- * 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
  */
@@ -93,7 +93,6 @@ int cert_add_ext(X509 *issuer, X509 *subject, int nid, char *value)
 }
 
 int cert_new(
-	int key_alg,
 	int md_alg,
 	cert_t *cert,
 	int days,
@@ -143,10 +142,10 @@ int cert_new(
 	}
 
 	/*
-	 * Set additional parameters if algorithm is RSA PSS. This is not
-	 * required for RSA 1.5 or ECDSA.
+	 * Set additional parameters if issuing public key algorithm is RSA.
+	 * This is not required for ECDSA.
 	 */
-	if (key_alg == KEY_ALG_RSA) {
+	if (EVP_PKEY_base_id(ikey) == EVP_PKEY_RSA) {
 		if (!EVP_PKEY_CTX_set_rsa_padding(pKeyCtx, RSA_PKCS1_PSS_PADDING)) {
 			ERR_print_errors_fp(stdout);
 			goto END;
diff --git a/tools/cert_create/src/key.c b/tools/cert_create/src/key.c
index 93d31f7c..0f80cce9 100644
--- a/tools/cert_create/src/key.c
+++ b/tools/cert_create/src/key.c
@@ -112,7 +112,6 @@ err:
 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 */
 #ifndef OPENSSL_NO_EC
 	key_create_ecdsa, 	/* KEY_ALG_ECDSA */
 #endif /* OPENSSL_NO_EC */
diff --git a/tools/cert_create/src/main.c b/tools/cert_create/src/main.c
index 44a65eb9..0cbd2196 100644
--- a/tools/cert_create/src/main.c
+++ b/tools/cert_create/src/main.c
@@ -92,7 +92,6 @@ 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 */
@@ -277,8 +276,7 @@ static const cmd_opt_t common_cmd_opt[] = {
 	},
 	{
 		{ "key-alg", required_argument, NULL, 'a' },
-		"Key algorithm: 'rsa' (default) - RSAPSS scheme as per \
-PKCS#1 v2.1, 'rsa_1_5' - RSA PKCS#1 v1.5, 'ecdsa'"
+		"Key algorithm: 'rsa' (default)- RSAPSS scheme as per PKCS#1 v2.1, 'ecdsa'"
 	},
 	{
 		{ "key-size", required_argument, NULL, 'b' },
@@ -545,7 +543,7 @@ int main(int argc, char *argv[])
 		}
 
 		/* Create certificate. Signed with corresponding key */
-		if (cert->fn && !cert_new(key_alg, hash_alg, cert, VAL_DAYS, 0, sk)) {
+		if (cert->fn && !cert_new(hash_alg, cert, VAL_DAYS, 0, sk)) {
 			ERROR("Cannot create %s\n", cert->cn);
 			exit(1);
 		}