This adds ECDSA signature verification support. The code is based on the
Linux code as of Linux-6.10. The Linux code expects the key to be in
ASN.1 encoded format. We don't need this in barebox as directly compile
the x and y key values into the binary, so this is left out.
Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
---
crypto/Kconfig | 20 ++++
crypto/Makefile | 19 ++++
crypto/ecdsa.c | 169 ++++++++++++++++++++++++++++++
include/asm-generic/barebox.lds.h | 7 ++
include/ecdsa.h | 21 ++++
5 files changed, 236 insertions(+)
create mode 100644 crypto/ecdsa.c
create mode 100644 include/ecdsa.h
diff --git a/crypto/Kconfig b/crypto/Kconfig
index e953ef5e15..eeacd9ffb7 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -156,4 +156,24 @@ config JWT
config CRYPTO_ECC
bool
+config CRYPTO_ECDSA
+ bool "ECDSA support"
+ select CRYPTO_ECC
+
+config CRYPTO_ECDSA_BUILTIN_KEYS
+ bool
+ default y if CRYPTO_ECDSA_KEY != ""
+ select KEYTOC
+
+config CRYPTO_ECDSA_KEY
+ depends on CRYPTO_ECDSA
+ string "ECDSA key to compile in"
+ help
+ This option should be a filename of a PEM-formatted file containing
+ X.509 certificates to be included into barebox. If the string starts
+ with "pkcs11:" it is interpreted as a PKCS#11 URI rather than a file.
+
+ This avoids the mkimage dependency of CONFIG_BOOTM_FITIMAGE_PUBKEY
+ at the cost of an openssl build-time dependency.
+
endmenu
diff --git a/crypto/Makefile b/crypto/Makefile
index 83c05761de..0bbd495378 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -37,3 +37,22 @@ endif
$(obj)/rsa-keys.h: $(RSA_DEP) FORCE
$(call cmd,public_keys,$(CONFIG_CRYPTO_RSA_KEY_NAME_HINT):$(if $(RSA_DEP),$<,$(CONFIG_CRYPTO_RSA_KEY)))
endif
+
+extra-$(CONFIG_CRYPTO_ECDSA_BUILTIN_KEYS) += ecdsa-keys.h
+
+ifdef CONFIG_CRYPTO_ECDSA_BUILTIN_KEYS
+
+$(obj)/ecdsa.o: $(obj)/ecdsa-keys.h
+
+CONFIG_CRYPTO_ECDSA_KEY := $(CONFIG_CRYPTO_ECDSA_KEY:"%"=%)
+
+ifneq ($(filter-out pkcs11:% __ENV__%, $(CONFIG_CRYPTO_ECDSA_KEY)),)
+ECDSA_DEP := $(CONFIG_CRYPTO_ECDSA_KEY)
+endif
+
+$(obj)/ecdsa-keys.h: $(ECDSA_DEP) FORCE
+ $(call cmd,public_keys,ecdsa_key:$(if $(ECDSA_DEP),$<,$(CONFIG_CRYPTO_ECDSA_KEY)))
+
+endif
+
+obj-$(CONFIG_CRYPTO_ECDSA) += ecdsa.o
diff --git a/crypto/ecdsa.c b/crypto/ecdsa.c
new file mode 100644
index 0000000000..d6b534be6d
--- /dev/null
+++ b/crypto/ecdsa.c
@@ -0,0 +1,169 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2021 IBM Corporation
+ */
+
+#include <common.h>
+
+#include <crypto/internal/ecc.h>
+#include <crypto/ecdh.h>
+#include <ecdsa.h>
+
+struct ecc_ctx {
+ unsigned int curve_id;
+ const struct ecc_curve *curve;
+
+ bool pub_key_set;
+ u64 x[ECC_MAX_DIGITS]; /* pub key x and y coordinates */
+ u64 y[ECC_MAX_DIGITS];
+ struct ecc_point pub_key;
+};
+
+static int _ecdsa_verify(struct ecc_ctx *ctx, const u64 *hash, const u64 *r, const u64 *s)
+{
+ const struct ecc_curve *curve = ctx->curve;
+ unsigned int ndigits = curve->g.ndigits;
+ u64 s1[ECC_MAX_DIGITS];
+ u64 u1[ECC_MAX_DIGITS];
+ u64 u2[ECC_MAX_DIGITS];
+ u64 x1[ECC_MAX_DIGITS];
+ u64 y1[ECC_MAX_DIGITS];
+ struct ecc_point res = ECC_POINT_INIT(x1, y1, ndigits);
+
+ /* 0 < r < n and 0 < s < n */
+ if (vli_is_zero(r, ndigits) || vli_cmp(r, curve->n, ndigits) >= 0 ||
+ vli_is_zero(s, ndigits) || vli_cmp(s, curve->n, ndigits) >= 0)
+ return -EBADMSG;
+
+ /* hash is given */
+ pr_debug("hash : %016llx %016llx ... %016llx\n",
+ hash[ndigits - 1], hash[ndigits - 2], hash[0]);
+
+ /* s1 = (s^-1) mod n */
+ vli_mod_inv(s1, s, curve->n, ndigits);
+ /* u1 = (hash * s1) mod n */
+ vli_mod_mult_slow(u1, hash, s1, curve->n, ndigits);
+ /* u2 = (r * s1) mod n */
+ vli_mod_mult_slow(u2, r, s1, curve->n, ndigits);
+ /* res = u1*G + u2 * pub_key */
+ ecc_point_mult_shamir(&res, u1, &curve->g, u2, &ctx->pub_key, curve);
+
+ /* res.x = res.x mod n (if res.x > order) */
+ if (unlikely(vli_cmp(res.x, curve->n, ndigits) == 1))
+ /* faster alternative for NIST p521, p384, p256 & p192 */
+ vli_sub(res.x, res.x, curve->n, ndigits);
+
+ if (!vli_cmp(res.x, r, ndigits))
+ return 0;
+
+ return -EKEYREJECTED;
+}
+
+static int ecdsa_key_size(const char *curve_name)
+{
+ if (!strcmp(curve_name, "prime256v1"))
+ return 256;
+ else
+ return 0;
+}
+
+int ecdsa_verify(const struct ecdsa_public_key *key, const uint8_t *sig,
+ const uint32_t sig_len, const uint8_t *hash)
+{
+ struct ecc_ctx _ctx = {};
+ struct ecc_ctx *ctx = &_ctx;
+ unsigned int curve_id = ECC_CURVE_NIST_P256;
+ int ret;
+ const void *r, *s;
+ u64 rh[4], sh[4];
+ u64 mhash[ECC_MAX_DIGITS];
+ int key_size_bytes = key->size_bits / 8;
+
+ ctx->curve_id = curve_id;
+ ctx->curve = ecc_get_curve(curve_id);
+ if (!ctx->curve)
+ return -EINVAL;
+
+ ctx->pub_key = ECC_POINT_INIT(ctx->x, ctx->y, ctx->curve->g.ndigits);
+ memcpy(ctx->pub_key.x, key->x, key_size_bytes);
+ memcpy(ctx->pub_key.y, key->y, key_size_bytes);
+
+ ret = ecc_is_pubkey_valid_full(ctx->curve, &ctx->pub_key);
+ if (ret)
+ return ret;
+
+ r = sig;
+ s = sig + key_size_bytes;
+
+ ecc_swap_digits((u64 *)r, rh, ctx->curve->g.ndigits);
+ ecc_swap_digits((u64 *)s, sh, ctx->curve->g.ndigits);
+
+ ecc_swap_digits((u64 *)hash, mhash, ctx->curve->g.ndigits);
+
+ return _ecdsa_verify(ctx, (void *)mhash, rh, sh);
+}
+
+static LIST_HEAD(ecdsa_keys);
+
+static int ecdsa_key_add(struct ecdsa_public_key *key)
+{
+ list_add_tail(&key->list, &ecdsa_keys);
+
+ return 0;
+}
+
+const struct ecdsa_public_key *ecdsa_key_next(const struct ecdsa_public_key *prev)
+{
+ prev = list_prepare_entry(prev, &ecdsa_keys, list);
+ list_for_each_entry_continue(prev, &ecdsa_keys, list)
+ return prev;
+
+ return NULL;
+}
+
+static struct ecdsa_public_key *ecdsa_key_dup(const struct ecdsa_public_key *key)
+{
+ struct ecdsa_public_key *new;
+ int key_size_bits;
+
+ key_size_bits = ecdsa_key_size(key->curve_name);
+ if (!key_size_bits)
+ return NULL;
+
+ new = xmemdup(key, sizeof(*key));
+ new->x = xmemdup(key->x, key_size_bits / 8);
+ new->y = xmemdup(key->y, key_size_bits / 8);
+ new->size_bits = key_size_bits;
+
+ return new;
+}
+
+extern const struct ecdsa_public_key * const __ecdsa_keys_start;
+extern const struct ecdsa_public_key * const __ecdsa_keys_end;
+
+static int ecdsa_init_keys(void)
+{
+ const struct ecdsa_public_key * const *iter;
+ struct ecdsa_public_key *key;
+ int ret;
+
+ for (iter = &__ecdsa_keys_start; iter != &__ecdsa_keys_end; iter++) {
+ key = ecdsa_key_dup(*iter);
+ if (!key) {
+ pr_err("Ignoring key with unknown curve_name %s\n", key->curve_name);
+ continue;
+ }
+
+ ret = ecdsa_key_add(key);
+ if (ret)
+ pr_err("Cannot add rsa key: %pe\n", ERR_PTR(ret));
+ }
+
+ return 0;
+}
+
+device_initcall(ecdsa_init_keys);
+
+#ifdef CONFIG_CRYPTO_ECDSA_BUILTIN_KEYS
+#include "ecdsa-keys.h"
+#endif
diff --git a/include/asm-generic/barebox.lds.h b/include/asm-generic/barebox.lds.h
index d3736ebaed..7f3b86f272 100644
--- a/include/asm-generic/barebox.lds.h
+++ b/include/asm-generic/barebox.lds.h
@@ -112,6 +112,12 @@
KEEP(*(.rsa_keys.rodata.*)); \
__rsa_keys_end = .; \
+#define BAREBOX_ECDSA_KEYS \
+ STRUCT_ALIGN(); \
+ __ecdsa_keys_start = .; \
+ KEEP(*(.ecdsa_keys.rodata.*)); \
+ __ecdsa_keys_end = .; \
+
#define BAREBOX_DEEP_PROBE \
STRUCT_ALIGN(); \
__barebox_deep_probe_start = .; \
@@ -141,6 +147,7 @@
BAREBOX_CLK_TABLE \
BAREBOX_DTB \
BAREBOX_RSA_KEYS \
+ BAREBOX_ECDSA_KEYS \
BAREBOX_PCI_FIXUP \
BAREBOX_DEEP_PROBE
diff --git a/include/ecdsa.h b/include/ecdsa.h
new file mode 100644
index 0000000000..e3df15a060
--- /dev/null
+++ b/include/ecdsa.h
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#ifndef _ECDSA_H
+#define _ECDSA_H
+
+struct ecdsa_public_key {
+ const char *curve_name; /* Name of curve, e.g. "prime256v1" */
+ const void *x; /* x coordinate of public key */
+ const void *y; /* y coordinate of public key */
+ unsigned int size_bits; /* key size in bits, derived from curve name */
+ struct list_head list;
+};
+
+int ecdsa_verify(const struct ecdsa_public_key *key, const uint8_t *sig,
+ const uint32_t sig_len, const uint8_t *hash);
+
+const struct ecdsa_public_key *ecdsa_key_next(const struct ecdsa_public_key *prev);
+
+#define for_each_ecdsa_key(key) \
+ for (key = ecdsa_key_next(NULL); key; key = ecdsa_key_next(key))
+
+#endif /* _ECDSA_H */
--
2.39.2
