image: Add RSA support for image signing

RSA provides a public key encryption facility which is ideal for image
signing and verification.

Images are signed using a private key by mkimage. Then at run-time, the
images are verified using a private key.

This implementation uses openssl for the host part (mkimage). To avoid
bringing large libraries into the U-Boot binary, the RSA public key
is encoded using a simple numeric representation in the device tree.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/rsa.h

@@ -0,0 +1,108 @@
+/*
+ * Copyright (c) 2013, Google Inc.
+ *
+ * (C) Copyright 2008 Semihalf
+ *
+ * (C) Copyright 2000-2006
+ * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#ifndef _RSA_H
+#define _RSA_H
+
+#include <errno.h>
+#include <image.h>
+
+#if IMAGE_ENABLE_SIGN
+/**
+ * sign() - calculate and return signature for given input data
+ *
+ * @info:	Specifies key and FIT information
+ * @data:	Pointer to the input data
+ * @data_len:	Data length
+ * @sigp:	Set to an allocated buffer holding the signature
+ * @sig_len:	Set to length of the calculated hash
+ *
+ * This computes input data signature according to selected algorithm.
+ * Resulting signature value is placed in an allocated buffer, the
+ * pointer is returned as *sigp. The length of the calculated
+ * signature is returned via the sig_len pointer argument. The caller
+ * should free *sigp.
+ *
+ * @return: 0, on success, -ve on error
+ */
+int rsa_sign(struct image_sign_info *info,
+	     const struct image_region region[],
+	     int region_count, uint8_t **sigp, uint *sig_len);
+
+/**
+ * add_verify_data() - Add verification information to FDT
+ *
+ * Add public key information to the FDT node, suitable for
+ * verification at run-time. The information added depends on the
+ * algorithm being used.
+ *
+ * @info:	Specifies key and FIT information
+ * @keydest:	Destination FDT blob for public key data
+ * @return: 0, on success, -ve on error
+*/
+int rsa_add_verify_data(struct image_sign_info *info, void *keydest);
+#else
+static inline int rsa_sign(struct image_sign_info *info,
+		const struct image_region region[], int region_count,
+		uint8_t **sigp, uint *sig_len)
+{
+	return -ENXIO;
+}
+
+static inline int rsa_add_verify_data(struct image_sign_info *info,
+				      void *keydest)
+{
+	return -ENXIO;
+}
+#endif
+
+#if IMAGE_ENABLE_VERIFY
+/**
+ * rsa_verify() - Verify a signature against some data
+ *
+ * Verify a RSA PKCS1.5 signature against an expected hash.
+ *
+ * @info:	Specifies key and FIT information
+ * @data:	Pointer to the input data
+ * @data_len:	Data length
+ * @sig:	Signature
+ * @sig_len:	Number of bytes in signature
+ * @return 0 if verified, -ve on error
+ */
+int rsa_verify(struct image_sign_info *info,
+	       const struct image_region region[], int region_count,
+	       uint8_t *sig, uint sig_len);
+#else
+static inline int rsa_verify(struct image_sign_info *info,
+		const struct image_region region[], int region_count,
+		uint8_t *sig, uint sig_len)
+{
+	return -ENXIO;
+}
+#endif
+
+#endif