cert_tool: Support for legacy RSA PKCS#1 v1.5

This patch enables choice of RSA version at run time to be used for
generating signatures by the cert_tool. The RSA PSS as defined in
PKCS#1 v2.1 becomes the default version and this patch enables to specify
the RSA PKCS#1 v1.5 algorithm to `cert_create` through the command line
-a option. Also, the build option `KEY_ALG` can be used to pass this
option from the build system. Please note that RSA PSS is mandated
by Trusted Board Boot requirements (TBBR) and legacy RSA support is
being added for compatibility reasons.

Fixes ARM-Software/tf-issues#499
Change-Id: Ifaa3f2f7c9b43f3d7b3effe2cde76bf6745a5d73
Co-Authored-By: Eleanor Bonnici <Eleanor.bonnici@arm.com>
Signed-off-by: Soby Mathew <soby.mathew@arm.com>

diff --git a/docs/user-guide.rst b/docs/user-guide.rst
index 1502c8c1059a07b57e05d657e0269ddd2f00b152..1181495cfc77a12efdb39c95efcd985dcddbcebf 100644 (file)
--- a/docs/user-guide.rst
+++ b/docs/user-guide.rst
@@ -407,8 +407,10 @@ 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 2 values viz ``rsa``, ``ecdsa``. The default value of this flag
-   is ``rsa``.
+   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.

diff --git a/drivers/auth/mbedtls/mbedtls_crypto.mk b/drivers/auth/mbedtls/mbedtls_crypto.mk
index 38197164c93e980b4f9b61e10f584fa05cbcff28..21b857bffe4a3465daaee700776674cdbce20165 100644 (file)
--- a/drivers/auth/mbedtls/mbedtls_crypto.mk
+++ b/drivers/auth/mbedtls/mbedtls_crypto.mk
@@ -9,7 +9,7 @@ include drivers/auth/mbedtls/mbedtls_common.mk
 # 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`, then set the variable to `rsa`.
+# 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

diff --git a/tools/cert_create/include/cert.h b/tools/cert_create/include/cert.h
index 543f12233aa4fcd4c9dac74a77288c86972e67d9..256e7afd25b0cd6f5b23d1484a46995cac97c804 100644 (file)
--- a/tools/cert_create/include/cert.h
+++ b/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) \

diff --git a/tools/cert_create/include/key.h b/tools/cert_create/include/key.h
index 4b9e88258c3ef9468c6114cda95f103f99124ff1..304fa6154f80fa8ca92342c3f44d12ffddce1ea2 100644 (file)
--- a/tools/cert_create/include/key.h
+++ b/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 */

diff --git a/tools/cert_create/src/cert.c b/tools/cert_create/src/cert.c
index 9775664a38d3d2b9cb9805a804b99ca24b7de80c..1b84e36d35ac020e86d3e58f24a67fca443f7c59 100644 (file)
--- a/tools/cert_create/src/cert.c
+++ b/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];
@@ -90,7 +90,7 @@ int cert_new(cert_t *cert, int days, int ca, STACK_OF(X509_EXTENSION) * sk)
        X509_NAME *name;
        ASN1_INTEGER *sno;
        int i, num, rc = 0;
-       EVP_MD_CTX  mdCtx;
+       EVP_MD_CTX mdCtx;
        EVP_PKEY_CTX *pKeyCtx = NULL;
 
        /* Create the certificate structure */
@@ -112,24 +112,32 @@ 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;
        }
 
-       if (!EVP_PKEY_CTX_set_rsa_padding(pKeyCtx, RSA_PKCS1_PSS_PADDING)) {
-               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;
+               }
 
-       if (!EVP_PKEY_CTX_set_rsa_pss_saltlen(pKeyCtx, RSA_SALT_LEN)) {
-               ERR_print_errors_fp(stdout);
-               goto END;
-       }
+               if (!EVP_PKEY_CTX_set_rsa_pss_saltlen(pKeyCtx, RSA_SALT_LEN)) {
+                       ERR_print_errors_fp(stdout);
+                       goto END;
+               }
 
-       if (!EVP_PKEY_CTX_set_rsa_mgf1_md(pKeyCtx, EVP_sha256())) {
-               ERR_print_errors_fp(stdout);
-               goto END;
+               if (!EVP_PKEY_CTX_set_rsa_mgf1_md(pKeyCtx, EVP_sha256())) {
+                       ERR_print_errors_fp(stdout);
+                       goto END;
+               }
        }
 
        /* x509.v3 */

diff --git a/tools/cert_create/src/main.c b/tools/cert_create/src/main.c
index f14601c8bc52e12360806d27d551b51891967173..df59961b0ac18b07c386355e853f031199fd3a56 100644 (file)
--- a/tools/cert_create/src/main.c
+++ b/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);
                }