lib: Add support for ECDSA image signing

mkimage supports rsa2048, and rsa4096 signatures. With newer silicon
now supporting hardware-accelerated ECDSA, it makes sense to expand
signing support to elliptic curves.

Implement host-side ECDSA signing and verification with libcrypto.
Device-side implementation of signature verification is beyond the
scope of this patch.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

1 files changed, 94 insertions, 0 deletions

diff --git a/include/u-boot/ecdsa.h b/include/u-boot/ecdsa.h
new file mode 100644
index 0000000..979690d
--- /dev/null
+++ b/include/u-boot/ecdsa.h
@@ -0,0 +1,94 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (c) 2020, Alexandru Gagniuc <mr.nuke.me@gmail.com>.
+ */
+
+#ifndef _ECDSA_H
+#define _ECDSA_H
+
+#include <errno.h>
+#include <image.h>
+#include <linux/kconfig.h>
+
+/**
+ * crypto_algo API impementation for ECDSA;
+ * @see "struct crypto_algo"
+ * @{
+ */
+#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 ecdsa_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. I just copypasted this from rsa.h.
+ *
+ * @info:	Specifies key and FIT information
+ * @keydest:	Destination FDT blob for public key data
+ * @return: 0, on success, -ENOSPC if the keydest FDT blob ran out of space,
+ * other -ve value on error
+ */
+int ecdsa_add_verify_data(struct image_sign_info *info, void *keydest);
+#else
+static inline
+int ecdsa_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 ecdsa_add_verify_data(struct image_sign_info *info, void *keydest)
+{
+	return -ENXIO;
+}
+#endif
+
+#if IMAGE_ENABLE_VERIFY_ECDSA
+/**
+ * verify() - Verify a signature against some data
+ *
+ * @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 ecdsa_verify(struct image_sign_info *info,
+		 const struct image_region region[], int region_count,
+		 uint8_t *sig, uint sig_len);
+#else
+static inline
+int ecdsa_verify(struct image_sign_info *info,
+		 const struct image_region region[], int region_count,
+		 uint8_t *sig, uint sig_len)
+{
+	return -ENXIO;
+}
+#endif
+/** @} */
+
+#define ECDSA256_BYTES	(256 / 8)
+
+#endif