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>
This commit is contained in:
Alexandru Gagniuc
Tom Rini
parent
4c17e5f691
commit
ed6c9e0b66
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@ -16,6 +16,7 @@
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DECLARE_GLOBAL_DATA_PTR;
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#endif /* !USE_HOSTCC*/
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#include <image.h>
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#include <u-boot/ecdsa.h>
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#include <u-boot/rsa.h>
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#include <u-boot/hash-checksum.h>
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@ -83,8 +84,14 @@ struct crypto_algo crypto_algos[] = {
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.sign = rsa_sign,
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.add_verify_data = rsa_add_verify_data,
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.verify = rsa_verify,
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}
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},
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{
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.name = "ecdsa256",
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.key_len = ECDSA256_BYTES,
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.sign = ecdsa_sign,
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.add_verify_data = ecdsa_add_verify_data,
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.verify = ecdsa_verify,
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},
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};
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struct padding_algo padding_algos[] = {
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@ -1224,16 +1224,19 @@ int calculate_hash(const void *data, int data_len, const char *algo,
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# if defined(CONFIG_FIT_SIGNATURE)
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# define IMAGE_ENABLE_SIGN 1
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# define IMAGE_ENABLE_VERIFY 1
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# define IMAGE_ENABLE_VERIFY_ECDSA 1
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# define FIT_IMAGE_ENABLE_VERIFY 1
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# include <openssl/evp.h>
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# else
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# define IMAGE_ENABLE_SIGN 0
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# define IMAGE_ENABLE_VERIFY 0
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# define IMAGE_ENABLE_VERIFY_ECDSA 0
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# define FIT_IMAGE_ENABLE_VERIFY 0
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# endif
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#else
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# define IMAGE_ENABLE_SIGN 0
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# define IMAGE_ENABLE_VERIFY CONFIG_IS_ENABLED(RSA_VERIFY)
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# define IMAGE_ENABLE_VERIFY_ECDSA 0
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# define FIT_IMAGE_ENABLE_VERIFY CONFIG_IS_ENABLED(FIT_SIGNATURE)
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#endif
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@ -0,0 +1,94 @@
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/* SPDX-License-Identifier: GPL-2.0+ */
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/*
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* Copyright (c) 2020, Alexandru Gagniuc <mr.nuke.me@gmail.com>.
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*/
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#ifndef _ECDSA_H
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#define _ECDSA_H
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#include <errno.h>
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#include <image.h>
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#include <linux/kconfig.h>
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/**
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* crypto_algo API impementation for ECDSA;
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* @see "struct crypto_algo"
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* @{
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*/
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#if IMAGE_ENABLE_SIGN
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/**
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* sign() - calculate and return signature for given input data
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*
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* @info: Specifies key and FIT information
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* @data: Pointer to the input data
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* @data_len: Data length
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* @sigp: Set to an allocated buffer holding the signature
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* @sig_len: Set to length of the calculated hash
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*
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* This computes input data signature according to selected algorithm.
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* Resulting signature value is placed in an allocated buffer, the
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* pointer is returned as *sigp. The length of the calculated
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* signature is returned via the sig_len pointer argument. The caller
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* should free *sigp.
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*
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* @return: 0, on success, -ve on error
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*/
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int ecdsa_sign(struct image_sign_info *info, const struct image_region region[],
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int region_count, uint8_t **sigp, uint *sig_len);
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/**
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* add_verify_data() - Add verification information to FDT
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*
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* Add public key information to the FDT node, suitable for
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* verification at run-time. The information added depends on the
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* algorithm being used. I just copypasted this from rsa.h.
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*
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* @info: Specifies key and FIT information
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* @keydest: Destination FDT blob for public key data
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* @return: 0, on success, -ENOSPC if the keydest FDT blob ran out of space,
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* other -ve value on error
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*/
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int ecdsa_add_verify_data(struct image_sign_info *info, void *keydest);
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#else
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static inline
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int ecdsa_sign(struct image_sign_info *info, const struct image_region region[],
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int region_count, uint8_t **sigp, uint *sig_len)
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{
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return -ENXIO;
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}
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static inline
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int ecdsa_add_verify_data(struct image_sign_info *info, void *keydest)
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{
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return -ENXIO;
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}
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#endif
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#if IMAGE_ENABLE_VERIFY_ECDSA
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/**
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* verify() - Verify a signature against some data
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*
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* @info: Specifies key and FIT information
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* @data: Pointer to the input data
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* @data_len: Data length
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* @sig: Signature
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* @sig_len: Number of bytes in signature
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* @return 0 if verified, -ve on error
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*/
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int ecdsa_verify(struct image_sign_info *info,
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const struct image_region region[], int region_count,
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uint8_t *sig, uint sig_len);
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#else
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static inline
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int ecdsa_verify(struct image_sign_info *info,
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const struct image_region region[], int region_count,
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uint8_t *sig, uint sig_len)
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{
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return -ENXIO;
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}
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#endif
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/** @} */
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#define ECDSA256_BYTES (256 / 8)
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#endif
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@ -0,0 +1,306 @@
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// SPDX-License-Identifier: GPL-2.0+
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/*
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* ECDSA image signing implementation using libcrypto backend
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*
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* The signature is a binary representation of the (R, S) points, padded to the
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* key size. The signature will be (2 * key_size_bits) / 8 bytes.
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*
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* Deviations from behavior of RSA equivalent:
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* - Verification uses private key. This is not technically required, but a
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* limitation on how clumsy the openssl API is to use.
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* - Handling of keys and key paths:
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* - The '-K' key directory option must contain path to the key file,
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* instead of the key directory.
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* - No assumptions are made about the file extension of the key
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* - The 'key-name-hint' property is only used for naming devicetree nodes,
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* but is not used for looking up keys on the filesystem.
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*
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* Copyright (c) 2020,2021, Alexandru Gagniuc <mr.nuke.me@gmail.com>
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*/
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#include <u-boot/ecdsa.h>
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#include <u-boot/fdt-libcrypto.h>
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#include <openssl/ssl.h>
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#include <openssl/ec.h>
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#include <openssl/bn.h>
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/* Image signing context for openssl-libcrypto */
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struct signer {
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EVP_PKEY *evp_key; /* Pointer to EVP_PKEY object */
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EC_KEY *ecdsa_key; /* Pointer to EC_KEY object */
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void *hash; /* Pointer to hash used for verification */
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void *signature; /* Pointer to output signature. Do not free()!*/
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};
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static int alloc_ctx(struct signer *ctx, const struct image_sign_info *info)
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{
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memset(ctx, 0, sizeof(*ctx));
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if (!OPENSSL_init_ssl(0, NULL)) {
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fprintf(stderr, "Failure to init SSL library\n");
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return -1;
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}
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ctx->hash = malloc(info->checksum->checksum_len);
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ctx->signature = malloc(info->crypto->key_len * 2);
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if (!ctx->hash || !ctx->signature)
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return -ENOMEM;
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return 0;
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}
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static void free_ctx(struct signer *ctx)
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{
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if (ctx->ecdsa_key)
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EC_KEY_free(ctx->ecdsa_key);
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if (ctx->evp_key)
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EVP_PKEY_free(ctx->evp_key);
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if (ctx->hash)
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free(ctx->hash);
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}
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/*
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* Convert an ECDSA signature to raw format
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*
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* openssl DER-encodes 'binary' signatures. We want the signature in a raw
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* (R, S) point pair. So we have to dance a bit.
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*/
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static void ecdsa_sig_encode_raw(void *buf, const ECDSA_SIG *sig, size_t order)
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{
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int point_bytes = order;
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const BIGNUM *r, *s;
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uintptr_t s_buf;
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ECDSA_SIG_get0(sig, &r, &s);
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s_buf = (uintptr_t)buf + point_bytes;
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BN_bn2binpad(r, buf, point_bytes);
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BN_bn2binpad(s, (void *)s_buf, point_bytes);
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}
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/* Get a signature from a raw encoding */
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static ECDSA_SIG *ecdsa_sig_from_raw(void *buf, size_t order)
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{
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int point_bytes = order;
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uintptr_t s_buf;
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ECDSA_SIG *sig;
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BIGNUM *r, *s;
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sig = ECDSA_SIG_new();
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if (!sig)
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return NULL;
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s_buf = (uintptr_t)buf + point_bytes;
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r = BN_bin2bn(buf, point_bytes, NULL);
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s = BN_bin2bn((void *)s_buf, point_bytes, NULL);
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ECDSA_SIG_set0(sig, r, s);
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return sig;
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}
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/* ECDSA key size in bytes */
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static size_t ecdsa_key_size_bytes(const EC_KEY *key)
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{
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const EC_GROUP *group;
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group = EC_KEY_get0_group(key);
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return EC_GROUP_order_bits(group) / 8;
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}
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static int read_key(struct signer *ctx, const char *key_name)
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{
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FILE *f = fopen(key_name, "r");
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if (!f) {
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fprintf(stderr, "Can not get key file '%s'\n", key_name);
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return -ENOENT;
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}
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ctx->evp_key = PEM_read_PrivateKey(f, NULL, NULL, NULL);
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fclose(f);
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if (!ctx->evp_key) {
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fprintf(stderr, "Can not read key from '%s'\n", key_name);
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return -EIO;
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}
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if (EVP_PKEY_id(ctx->evp_key) != EVP_PKEY_EC) {
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fprintf(stderr, "'%s' is not an ECDSA key\n", key_name);
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return -EINVAL;
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}
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ctx->ecdsa_key = EVP_PKEY_get1_EC_KEY(ctx->evp_key);
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if (!ctx->ecdsa_key)
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fprintf(stderr, "Can not extract ECDSA key\n");
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return (ctx->ecdsa_key) ? 0 : -EINVAL;
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}
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/* Prepare a 'signer' context that's ready to sign and verify. */
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static int prepare_ctx(struct signer *ctx, const struct image_sign_info *info)
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{
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const char *kname = info->keydir;
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int key_len_bytes, ret;
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ret = alloc_ctx(ctx, info);
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if (ret)
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return ret;
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ret = read_key(ctx, kname);
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if (ret)
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return ret;
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key_len_bytes = ecdsa_key_size_bytes(ctx->ecdsa_key);
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if (key_len_bytes != info->crypto->key_len) {
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fprintf(stderr, "Expected a %u-bit key, got %u-bit key\n",
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info->crypto->key_len * 8, key_len_bytes * 8);
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return -EINVAL;
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}
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return 0;
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}
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static int do_sign(struct signer *ctx, struct image_sign_info *info,
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const struct image_region region[], int region_count)
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{
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const struct checksum_algo *algo = info->checksum;
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ECDSA_SIG *sig;
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algo->calculate(algo->name, region, region_count, ctx->hash);
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sig = ECDSA_do_sign(ctx->hash, algo->checksum_len, ctx->ecdsa_key);
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ecdsa_sig_encode_raw(ctx->signature, sig, info->crypto->key_len);
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return 0;
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}
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static int ecdsa_check_signature(struct signer *ctx, struct image_sign_info *info)
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{
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ECDSA_SIG *sig;
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int okay;
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sig = ecdsa_sig_from_raw(ctx->signature, info->crypto->key_len);
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if (!sig)
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return -ENOMEM;
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okay = ECDSA_do_verify(ctx->hash, info->checksum->checksum_len,
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sig, ctx->ecdsa_key);
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if (!okay)
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fprintf(stderr, "WARNING: Signature is fake news!\n");
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ECDSA_SIG_free(sig);
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return !okay;
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}
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static int do_verify(struct signer *ctx, struct image_sign_info *info,
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const struct image_region region[], int region_count,
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uint8_t *raw_sig, uint sig_len)
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{
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const struct checksum_algo *algo = info->checksum;
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if (sig_len != info->crypto->key_len * 2) {
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fprintf(stderr, "Signature has wrong length\n");
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return -EINVAL;
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}
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memcpy(ctx->signature, raw_sig, sig_len);
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algo->calculate(algo->name, region, region_count, ctx->hash);
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return ecdsa_check_signature(ctx, info);
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}
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int ecdsa_sign(struct image_sign_info *info, const struct image_region region[],
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int region_count, uint8_t **sigp, uint *sig_len)
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{
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struct signer ctx;
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int ret;
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ret = prepare_ctx(&ctx, info);
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if (ret >= 0) {
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do_sign(&ctx, info, region, region_count);
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*sigp = ctx.signature;
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*sig_len = info->crypto->key_len * 2;
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ret = ecdsa_check_signature(&ctx, info);
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}
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free_ctx(&ctx);
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return ret;
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}
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int ecdsa_verify(struct image_sign_info *info,
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const struct image_region region[], int region_count,
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uint8_t *sig, uint sig_len)
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{
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struct signer ctx;
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int ret;
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ret = prepare_ctx(&ctx, info);
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if (ret >= 0)
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ret = do_verify(&ctx, info, region, region_count, sig, sig_len);
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free_ctx(&ctx);
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return ret;
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}
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static int do_add(struct signer *ctx, void *fdt, const char *key_node_name)
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{
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int signature_node, key_node, ret, key_bits;
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const char *curve_name;
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const EC_GROUP *group;
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const EC_POINT *point;
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BIGNUM *x, *y;
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signature_node = fdt_subnode_offset(fdt, 0, FIT_SIG_NODENAME);
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if (signature_node < 0) {
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fprintf(stderr, "Could not find 'signature node: %s\n",
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fdt_strerror(signature_node));
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return signature_node;
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}
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key_node = fdt_add_subnode(fdt, signature_node, key_node_name);
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if (key_node < 0) {
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fprintf(stderr, "Could not create '%s' node: %s\n",
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key_node_name, fdt_strerror(key_node));
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return key_node;
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}
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group = EC_KEY_get0_group(ctx->ecdsa_key);
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key_bits = EC_GROUP_order_bits(group);
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curve_name = OBJ_nid2sn(EC_GROUP_get_curve_name(group));
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/* Let 'x' and 'y' memory leak by not BN_free()'ing them. */
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x = BN_new();
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y = BN_new();
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point = EC_KEY_get0_public_key(ctx->ecdsa_key);
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EC_POINT_get_affine_coordinates(group, point, x, y, NULL);
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ret = fdt_setprop_string(fdt, key_node, "ecdsa,curve", curve_name);
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if (ret < 0)
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return ret;
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ret = fdt_add_bignum(fdt, key_node, "ecdsa,x-point", x, key_bits);
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if (ret < 0)
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return ret;
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ret = fdt_add_bignum(fdt, key_node, "ecdsa,y-point", y, key_bits);
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if (ret < 0)
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return ret;
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return 0;
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}
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int ecdsa_add_verify_data(struct image_sign_info *info, void *fdt)
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{
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const char *fdt_key_name;
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struct signer ctx;
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int ret;
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fdt_key_name = info->keyname ? info->keyname : "default-key";
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ret = prepare_ctx(&ctx, info);
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if (ret >= 0)
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do_add(&ctx, fdt, fdt_key_name);
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free_ctx(&ctx);
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return ret;
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}
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@ -70,6 +70,8 @@ RSA_OBJS-$(CONFIG_FIT_SIGNATURE) := $(addprefix lib/rsa/, \
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rsa-sign.o rsa-verify.o \
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rsa-mod-exp.o)
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ECDSA_OBJS-$(CONFIG_FIT_SIGNATURE) := $(addprefix lib/ecdsa/, ecdsa-libcrypto.o)
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AES_OBJS-$(CONFIG_FIT_CIPHER) := $(addprefix lib/aes/, \
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aes-encrypt.o aes-decrypt.o)
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@ -124,6 +126,7 @@ dumpimage-mkimage-objs := aisimage.o \
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gpimage.o \
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gpimage-common.o \
|
||||
mtk_image.o \
|
||||
$(ECDSA_OBJS-y) \
|
||||
$(RSA_OBJS-y) \
|
||||
$(AES_OBJS-y)
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue