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>
mrnuke · Feb 4, 2021 · a2ae016 · a2ae016
1 parent 5ab755d
commit a2ae016
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Showing 5 changed files with 415 additions and 2 deletions.
diff --git a/common/image-sig.c b/common/image-sig.c
@@ -15,6 +15,7 @@
 DECLARE_GLOBAL_DATA_PTR;
 #endif /* !USE_HOSTCC*/
 #include <image.h>
+#include <u-boot/ecdsa.h>
 #include <u-boot/rsa.h>
 #include <u-boot/hash-checksum.h>
 
@@ -82,8 +83,14 @@ struct crypto_algo crypto_algos[] = {
 		.sign = rsa_sign,
 		.add_verify_data = rsa_add_verify_data,
 		.verify = rsa_verify,
-	}
-
+	},
+	{
+		.name = "ecdsa256",
+		.key_len = ECDSA256_BYTES,
+		.sign = ecdsa_sign,
+		.add_verify_data = ecdsa_add_verify_data,
+		.verify = ecdsa_verify,
+	},
 };
 
 struct padding_algo padding_algos[] = {

diff --git a/include/image.h b/include/image.h
@@ -1200,16 +1200,19 @@ int calculate_hash(const void *data, int data_len, const char *algo,
 # if defined(CONFIG_FIT_SIGNATURE)
 #  define IMAGE_ENABLE_SIGN	1
 #  define IMAGE_ENABLE_VERIFY	1
+#  define IMAGE_ENABLE_VERIFY_ECDSA	1
 #  define FIT_IMAGE_ENABLE_VERIFY	1
 #  include <openssl/evp.h>
 # else
 #  define IMAGE_ENABLE_SIGN	0
 #  define IMAGE_ENABLE_VERIFY	0
+# define IMAGE_ENABLE_VERIFY_ECDSA	0
 #  define FIT_IMAGE_ENABLE_VERIFY	0
 # endif
 #else
 # define IMAGE_ENABLE_SIGN	0
 # define IMAGE_ENABLE_VERIFY		CONFIG_IS_ENABLED(RSA_VERIFY)
+# define IMAGE_ENABLE_VERIFY_ECDSA	0
 # define FIT_IMAGE_ENABLE_VERIFY	CONFIG_IS_ENABLED(FIT_SIGNATURE)
 #endif
 

diff --git a/include/u-boot/ecdsa.h 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