TBB: add tool to generate certificates

This patch adds a tool that generates all the necessary elements
to establish the chain of trust (CoT) between the images.

The tool reads the binary images and signing keys and outputs the
corresponding certificates that will be used by the target at run
time to verify the authenticity of the images.

Note: the platform port must provide the file platform_oid.h. This
file will define the OIDs of the x509 extensions that will be added
to the certificates in order to establish the CoT.

Change-Id: I2734d6808b964a2107ab3a4805110698066a04be
diff --git a/tools/cert_create/src/cert.c b/tools/cert_create/src/cert.c
new file mode 100644
index 0000000..9705643
--- /dev/null
+++ b/tools/cert_create/src/cert.c
@@ -0,0 +1,180 @@
+/*
+ * 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 <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <openssl/conf.h>
+#include <openssl/err.h>
+#include <openssl/pem.h>
+#include <openssl/sha.h>
+#include <openssl/x509v3.h>
+
+#include "cert.h"
+#include "debug.h"
+#include "key.h"
+#include "platform_oid.h"
+#include "sha.h"
+
+#define SERIAL_RAND_BITS	64
+
+int rand_serial(BIGNUM *b, ASN1_INTEGER *ai)
+{
+	BIGNUM *btmp;
+	int ret = 0;
+	if (b)
+		btmp = b;
+	else
+		btmp = BN_new();
+
+	if (!btmp)
+		return 0;
+
+	if (!BN_pseudo_rand(btmp, SERIAL_RAND_BITS, 0, 0))
+		goto error;
+	if (ai && !BN_to_ASN1_INTEGER(btmp, ai))
+		goto error;
+
+	ret = 1;
+
+error:
+
+	if (!b)
+		BN_free(btmp);
+
+	return ret;
+}
+
+int cert_add_ext(X509 *issuer, X509 *subject, int nid, char *value)
+{
+	X509_EXTENSION *ex;
+	X509V3_CTX ctx;
+
+	/* No configuration database */
+	X509V3_set_ctx_nodb(&ctx);
+
+	/* Set issuer and subject certificates in the context */
+	X509V3_set_ctx(&ctx, issuer, subject, NULL, NULL, 0);
+	ex = X509V3_EXT_conf_nid(NULL, &ctx, nid, value);
+	if (!ex) {
+		ERR_print_errors_fp(stdout);
+		return 0;
+	}
+
+	X509_add_ext(subject, ex, -1);
+	X509_EXTENSION_free(ex);
+
+	return 1;
+}
+
+
+int cert_new(cert_t *cert, int days, int ca, STACK_OF(X509_EXTENSION) * sk)
+{
+	EVP_PKEY *pkey = cert->key->key;
+	EVP_PKEY *ikey = cert->issuer->key->key;
+	X509 *issuer = cert->issuer->x;
+	X509 *x = NULL;
+	X509_EXTENSION *ex = NULL;
+	X509_NAME *name = NULL;
+	ASN1_INTEGER *sno = NULL;
+	int i, num;
+
+	/* Create the certificate structure */
+	x = X509_new();
+	if (!x) {
+		return 0;
+	}
+
+	/* If we do not have a key, use the issuer key (the certificate will
+	 * become self signed). This happens in content certificates. */
+	if (!pkey) {
+		pkey = ikey;
+	}
+
+	/* If we do not have an issuer certificate, use our own (the certificate
+	 * will become self signed) */
+	if (!issuer) {
+		issuer = x;
+	}
+
+	/* x509.v3 */
+	X509_set_version(x, 2);
+
+	/* Random serial number */
+	sno = ASN1_INTEGER_new();
+	rand_serial(NULL, sno);
+	X509_set_serialNumber(x, sno);
+	ASN1_INTEGER_free(sno);
+
+	X509_gmtime_adj(X509_get_notBefore(x), 0);
+	X509_gmtime_adj(X509_get_notAfter(x), (long)60*60*24*days);
+	X509_set_pubkey(x, pkey);
+
+	/* Subject name */
+	name = X509_get_subject_name(x);
+	X509_NAME_add_entry_by_txt(name, "CN", MBSTRING_ASC,
+			(const unsigned char *)cert->cn, -1, -1, 0);
+	X509_set_subject_name(x, name);
+
+	/* Issuer name */
+	name = X509_get_issuer_name(x);
+	X509_NAME_add_entry_by_txt(name, "CN", MBSTRING_ASC,
+			(const unsigned char *)cert->issuer->cn, -1, -1, 0);
+	X509_set_issuer_name(x, name);
+
+	/* Add various extensions: standard extensions */
+	cert_add_ext(issuer, x, NID_subject_key_identifier, "hash");
+	cert_add_ext(issuer, x, NID_authority_key_identifier, "keyid:always");
+	if (ca) {
+		cert_add_ext(issuer, x, NID_basic_constraints, "CA:TRUE");
+		cert_add_ext(issuer, x, NID_key_usage, "keyCertSign");
+	} else {
+		cert_add_ext(issuer, x, NID_basic_constraints, "CA:FALSE");
+	}
+
+	/* Add custom extensions */
+	if (sk != NULL) {
+		num = sk_X509_EXTENSION_num(sk);
+		for (i = 0; i < num; i++) {
+			ex = sk_X509_EXTENSION_value(sk, i);
+			X509_add_ext(x, ex, -1);
+		}
+	}
+
+	/* Sign the certificate with the issuer key */
+	if (!X509_sign(x, ikey, EVP_sha1())) {
+		ERR_print_errors_fp(stdout);
+		return 0;
+	}
+
+	cert->x = x;
+	return 1;
+}