diff options
Diffstat (limited to 'lib/ecdsa')
| -rw-r--r-- | lib/ecdsa/Kconfig | 24 | ||||
| -rw-r--r-- | lib/ecdsa/Makefile | 1 | ||||
| -rw-r--r-- | lib/ecdsa/ecdsa-libcrypto.c | 372 | ||||
| -rw-r--r-- | lib/ecdsa/ecdsa-verify.c | 139 |
4 files changed, 536 insertions, 0 deletions
diff --git a/lib/ecdsa/Kconfig b/lib/ecdsa/Kconfig new file mode 100644 index 00000000000..5c3d67d8144 --- /dev/null +++ b/lib/ecdsa/Kconfig @@ -0,0 +1,24 @@ +config ECDSA + bool "Enable ECDSA support" + depends on DM + help + This enables the ECDSA (elliptic curve signature) algorithm for FIT + image verification in U-Boot. The ECDSA algorithm is implemented + using the driver model, so CONFIG_DM is required by this library. + See doc/uImage.FIT/signature.txt for more details. + ECDSA is enabled for mkimage regardless of this option. + +if ECDSA + +config ECDSA_VERIFY + bool "Enable ECDSA verification support in U-Boot." + help + Allow ECDSA signatures to be recognized and verified in U-Boot. + +config SPL_ECDSA_VERIFY + bool "Enable ECDSA verification support in SPL" + depends on SPL + help + Allow ECDSA signatures to be recognized and verified in SPL. + +endif diff --git a/lib/ecdsa/Makefile b/lib/ecdsa/Makefile new file mode 100644 index 00000000000..32b6183f6ff --- /dev/null +++ b/lib/ecdsa/Makefile @@ -0,0 +1 @@ +obj-$(CONFIG_$(XPL_)ECDSA_VERIFY) += ecdsa-verify.o diff --git a/lib/ecdsa/ecdsa-libcrypto.c b/lib/ecdsa/ecdsa-libcrypto.c new file mode 100644 index 00000000000..1c5dde60691 --- /dev/null +++ b/lib/ecdsa/ecdsa-libcrypto.c @@ -0,0 +1,372 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * ECDSA image signing implementation using libcrypto backend + * + * The signature is a binary representation of the (R, S) points, padded to the + * key size. The signature will be (2 * key_size_bits) / 8 bytes. + * + * Deviations from behavior of RSA equivalent: + * - Verification uses private key. This is not technically required, but a + * limitation on how clumsy the openssl API is to use. + * - Handling of keys and key paths: + * - The '-K' key directory option must contain path to the key file, + * instead of the key directory. + * - No assumptions are made about the file extension of the key + * - The 'key-name-hint' property is only used for naming devicetree nodes, + * but is not used for looking up keys on the filesystem. + * + * Copyright (c) 2020,2021, Alexandru Gagniuc <mr.nuke.me@gmail.com> + */ + +#define OPENSSL_API_COMPAT 0x10101000L + +#include <u-boot/ecdsa.h> +#include <u-boot/fdt-libcrypto.h> +#include <openssl/ssl.h> +#include <openssl/ec.h> +#include <openssl/bn.h> + +/* Image signing context for openssl-libcrypto */ +struct signer { + EVP_PKEY *evp_key; /* Pointer to EVP_PKEY object */ + EC_KEY *ecdsa_key; /* Pointer to EC_KEY object */ + void *hash; /* Pointer to hash used for verification */ + void *signature; /* Pointer to output signature. Do not free()!*/ +}; + +static int alloc_ctx(struct signer *ctx, const struct image_sign_info *info) +{ + memset(ctx, 0, sizeof(*ctx)); + + if (!OPENSSL_init_ssl(0, NULL)) { + fprintf(stderr, "Failure to init SSL library\n"); + return -1; + } + + ctx->hash = malloc(info->checksum->checksum_len); + ctx->signature = malloc(info->crypto->key_len * 2); + + if (!ctx->hash || !ctx->signature) + return -ENOMEM; + + return 0; +} + +static void free_ctx(struct signer *ctx) +{ + if (ctx->ecdsa_key) + EC_KEY_free(ctx->ecdsa_key); + + if (ctx->evp_key) + EVP_PKEY_free(ctx->evp_key); + + if (ctx->hash) + free(ctx->hash); +} + +/* + * Convert an ECDSA signature to raw format + * + * openssl DER-encodes 'binary' signatures. We want the signature in a raw + * (R, S) point pair. So we have to dance a bit. + */ +static void ecdsa_sig_encode_raw(void *buf, const ECDSA_SIG *sig, size_t order) +{ + int point_bytes = order; + const BIGNUM *r, *s; + uintptr_t s_buf; + + ECDSA_SIG_get0(sig, &r, &s); + s_buf = (uintptr_t)buf + point_bytes; + BN_bn2binpad(r, buf, point_bytes); + BN_bn2binpad(s, (void *)s_buf, point_bytes); +} + +/* Get a signature from a raw encoding */ +static ECDSA_SIG *ecdsa_sig_from_raw(void *buf, size_t order) +{ + int point_bytes = order; + uintptr_t s_buf; + ECDSA_SIG *sig; + BIGNUM *r, *s; + + sig = ECDSA_SIG_new(); + if (!sig) + return NULL; + + s_buf = (uintptr_t)buf + point_bytes; + r = BN_bin2bn(buf, point_bytes, NULL); + s = BN_bin2bn((void *)s_buf, point_bytes, NULL); + ECDSA_SIG_set0(sig, r, s); + + return sig; +} + +/* ECDSA key size in bytes */ +static size_t ecdsa_key_size_bytes(const EC_KEY *key) +{ + const EC_GROUP *group; + + group = EC_KEY_get0_group(key); + return (EC_GROUP_order_bits(group) + 7) / 8; +} + +static int default_password(char *buf, int size, int rwflag, void *u) +{ + strncpy(buf, (char *)u, size); + buf[size - 1] = '\0'; + return strlen(buf); +} + +static int read_key(struct signer *ctx, const char *key_name) +{ + FILE *f = fopen(key_name, "r"); + const char *key_pass; + + if (!f) { + fprintf(stderr, "Can not get key file '%s'\n", key_name); + return -ENOENT; + } + + key_pass = getenv("MKIMAGE_SIGN_PASSWORD"); + if (key_pass) { + ctx->evp_key = PEM_read_PrivateKey(f, NULL, default_password, (void *)key_pass); + + } else { + ctx->evp_key = PEM_read_PrivateKey(f, NULL, NULL, NULL); + } + fclose(f); + if (!ctx->evp_key) { + fprintf(stderr, "Can not read key from '%s'\n", key_name); + return -EIO; + } + + if (EVP_PKEY_id(ctx->evp_key) != EVP_PKEY_EC) { + fprintf(stderr, "'%s' is not an ECDSA key\n", key_name); + return -EINVAL; + } + + ctx->ecdsa_key = EVP_PKEY_get1_EC_KEY(ctx->evp_key); + if (!ctx->ecdsa_key) + fprintf(stderr, "Can not extract ECDSA key\n"); + + return (ctx->ecdsa_key) ? 0 : -EINVAL; +} + +/* Prepare a 'signer' context that's ready to sign and verify. */ +static int prepare_ctx(struct signer *ctx, const struct image_sign_info *info) +{ + int key_len_bytes, ret; + char kname[1024]; + + memset(ctx, 0, sizeof(*ctx)); + + if (info->keyfile) { + snprintf(kname, sizeof(kname), "%s", info->keyfile); + } else if (info->keydir && info->keyname) { + snprintf(kname, sizeof(kname), "%s/%s.pem", info->keydir, + info->keyname); + } else { + fprintf(stderr, "keyfile, keyname, or key-name-hint missing\n"); + return -EINVAL; + } + + ret = alloc_ctx(ctx, info); + if (ret) + return ret; + + ret = read_key(ctx, kname); + if (ret) + return ret; + + key_len_bytes = ecdsa_key_size_bytes(ctx->ecdsa_key); + if (key_len_bytes != info->crypto->key_len) { + fprintf(stderr, "Expected a %u-bit key, got %u-bit key\n", + info->crypto->key_len * 8, key_len_bytes * 8); + return -EINVAL; + } + + return 0; +} + +static int do_sign(struct signer *ctx, struct image_sign_info *info, + const struct image_region region[], int region_count) +{ + const struct checksum_algo *algo = info->checksum; + ECDSA_SIG *sig; + + algo->calculate(algo->name, region, region_count, ctx->hash); + sig = ECDSA_do_sign(ctx->hash, algo->checksum_len, ctx->ecdsa_key); + + ecdsa_sig_encode_raw(ctx->signature, sig, info->crypto->key_len); + + return 0; +} + +static int ecdsa_check_signature(struct signer *ctx, struct image_sign_info *info) +{ + ECDSA_SIG *sig; + int okay; + + sig = ecdsa_sig_from_raw(ctx->signature, info->crypto->key_len); + if (!sig) + return -ENOMEM; + + okay = ECDSA_do_verify(ctx->hash, info->checksum->checksum_len, + sig, ctx->ecdsa_key); + if (!okay) + fprintf(stderr, "WARNING: Signature is fake news!\n"); + + ECDSA_SIG_free(sig); + return !okay; +} + +static int do_verify(struct signer *ctx, struct image_sign_info *info, + const struct image_region region[], int region_count, + uint8_t *raw_sig, uint sig_len) +{ + const struct checksum_algo *algo = info->checksum; + + if (sig_len != info->crypto->key_len * 2) { + fprintf(stderr, "Signature has wrong length\n"); + return -EINVAL; + } + + memcpy(ctx->signature, raw_sig, sig_len); + algo->calculate(algo->name, region, region_count, ctx->hash); + + return ecdsa_check_signature(ctx, info); +} + +int ecdsa_sign(struct image_sign_info *info, const struct image_region region[], + int region_count, uint8_t **sigp, uint *sig_len) +{ + struct signer ctx; + int ret; + + ret = prepare_ctx(&ctx, info); + if (ret >= 0) { + do_sign(&ctx, info, region, region_count); + *sigp = ctx.signature; + *sig_len = info->crypto->key_len * 2; + + ret = ecdsa_check_signature(&ctx, info); + } + + free_ctx(&ctx); + return ret; +} + +int ecdsa_verify(struct image_sign_info *info, + const struct image_region region[], int region_count, + uint8_t *sig, uint sig_len) +{ + struct signer ctx; + int ret; + + ret = prepare_ctx(&ctx, info); + if (ret >= 0) + ret = do_verify(&ctx, info, region, region_count, sig, sig_len); + + free_ctx(&ctx); + return ret; +} + +static int do_add(struct signer *ctx, void *fdt, const char *key_node_name, + struct image_sign_info *info) +{ + int signature_node, key_node, ret, key_bits; + const char *curve_name; + const EC_GROUP *group; + const EC_POINT *point; + BIGNUM *x, *y; + + signature_node = fdt_subnode_offset(fdt, 0, FIT_SIG_NODENAME); + if (signature_node == -FDT_ERR_NOTFOUND) { + signature_node = fdt_add_subnode(fdt, 0, FIT_SIG_NODENAME); + if (signature_node < 0) { + if (signature_node != -FDT_ERR_NOSPACE) { + fprintf(stderr, "Couldn't create signature node: %s\n", + fdt_strerror(signature_node)); + } + return signature_node; + } + } else if (signature_node < 0) { + fprintf(stderr, "Cannot select keys signature_node: %s\n", + fdt_strerror(signature_node)); + return signature_node; + } + + /* Either create or overwrite the named key node */ + key_node = fdt_subnode_offset(fdt, signature_node, key_node_name); + if (key_node == -FDT_ERR_NOTFOUND) { + key_node = fdt_add_subnode(fdt, signature_node, key_node_name); + if (key_node < 0) { + if (key_node != -FDT_ERR_NOSPACE) { + fprintf(stderr, "Could not create key subnode: %s\n", + fdt_strerror(key_node)); + } + return key_node; + } + } else if (key_node < 0) { + fprintf(stderr, "Cannot select keys key_node: %s\n", + fdt_strerror(key_node)); + return key_node; + } + + group = EC_KEY_get0_group(ctx->ecdsa_key); + key_bits = EC_GROUP_order_bits(group); + curve_name = OBJ_nid2sn(EC_GROUP_get_curve_name(group)); + /* Let 'x' and 'y' memory leak by not BN_free()'ing them. */ + x = BN_new(); + y = BN_new(); + point = EC_KEY_get0_public_key(ctx->ecdsa_key); + EC_POINT_get_affine_coordinates(group, point, x, y, NULL); + + ret = fdt_setprop_string(fdt, key_node, FIT_KEY_HINT, + info->keyname); + if (ret < 0) + return ret; + + ret = fdt_setprop_string(fdt, key_node, "ecdsa,curve", curve_name); + if (ret < 0) + return ret; + + ret = fdt_add_bignum(fdt, key_node, "ecdsa,x-point", x, key_bits); + if (ret < 0) + return ret; + + ret = fdt_add_bignum(fdt, key_node, "ecdsa,y-point", y, key_bits); + if (ret < 0) + return ret; + + ret = fdt_setprop_string(fdt, key_node, FIT_ALGO_PROP, + info->name); + if (ret < 0) + return ret; + + ret = fdt_setprop_string(fdt, key_node, FIT_KEY_REQUIRED, + info->require_keys); + if (ret < 0) + return ret; + + return key_node; +} + +int ecdsa_add_verify_data(struct image_sign_info *info, void *fdt) +{ + const char *fdt_key_name; + struct signer ctx; + int ret; + + fdt_key_name = info->keyname ? info->keyname : "default-key"; + ret = prepare_ctx(&ctx, info); + if (ret >= 0) { + ret = do_add(&ctx, fdt, fdt_key_name, info); + if (ret < 0) + ret = ret == -FDT_ERR_NOSPACE ? -ENOSPC : -EIO; + } + + free_ctx(&ctx); + return ret; +} diff --git a/lib/ecdsa/ecdsa-verify.c b/lib/ecdsa/ecdsa-verify.c new file mode 100644 index 00000000000..4d1835b598a --- /dev/null +++ b/lib/ecdsa/ecdsa-verify.c @@ -0,0 +1,139 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * ECDSA signature verification for u-boot + * + * This implements the firmware-side wrapper for ECDSA verification. It bridges + * the struct crypto_algo API to the ECDSA uclass implementations. + * + * Copyright (c) 2020, Alexandru Gagniuc <mr.nuke.me@gmail.com> + */ + +#include <crypto/ecdsa-uclass.h> +#include <dm/uclass.h> +#include <u-boot/ecdsa.h> + +/* + * Derive size of an ECDSA key from the curve name + * + * While it's possible to extract the key size by using string manipulation, + * use a list of known curves for the time being. + */ +static int ecdsa_key_size(const char *curve_name) +{ + if (!strcmp(curve_name, "prime256v1")) + return 256; + else + return 0; +} + +static int fdt_get_key(struct ecdsa_public_key *key, const void *fdt, int node) +{ + int x_len, y_len; + + key->curve_name = fdt_getprop(fdt, node, "ecdsa,curve", NULL); + if (!key->curve_name) { + debug("Error: ecdsa cannot get 'ecdsa,curve' property from key. Likely not an ecdsa key.\n"); + return -ENOMSG; + } + + key->size_bits = ecdsa_key_size(key->curve_name); + if (key->size_bits == 0) { + debug("Unknown ECDSA curve '%s'", key->curve_name); + return -EINVAL; + } + + key->x = fdt_getprop(fdt, node, "ecdsa,x-point", &x_len); + key->y = fdt_getprop(fdt, node, "ecdsa,y-point", &y_len); + + if (!key->x || !key->y) + return -EINVAL; + + if (x_len != (key->size_bits / 8) || y_len != (key->size_bits / 8)) { + printf("%s: node=%d, curve@%p x@%p+%i y@%p+%i\n", __func__, + node, key->curve_name, key->x, x_len, key->y, y_len); + return -EINVAL; + } + + return 0; +} + +static int ecdsa_verify_hash(struct udevice *dev, + const struct image_sign_info *info, + const void *hash, const void *sig, uint sig_len) +{ + const struct ecdsa_ops *ops = device_get_ops(dev); + const struct checksum_algo *algo = info->checksum; + struct ecdsa_public_key key; + int sig_node, key_node, ret; + + if (!ops || !ops->verify) + return -ENODEV; + + if (info->required_keynode > 0) { + ret = fdt_get_key(&key, info->fdt_blob, info->required_keynode); + if (ret < 0) + return ret; + + return ops->verify(dev, &key, hash, algo->checksum_len, + sig, sig_len); + } + + sig_node = fdt_subnode_offset(info->fdt_blob, 0, FIT_SIG_NODENAME); + if (sig_node < 0) + return -ENOENT; + + /* Try all possible keys under the "/signature" node */ + fdt_for_each_subnode(key_node, info->fdt_blob, sig_node) { + ret = fdt_get_key(&key, info->fdt_blob, key_node); + if (ret < 0) + continue; + + ret = ops->verify(dev, &key, hash, algo->checksum_len, + sig, sig_len); + + /* On success, don't worry about remaining keys */ + if (!ret) + return 0; + } + + return -EPERM; +} + +int ecdsa_verify(struct image_sign_info *info, + const struct image_region region[], int region_count, + uint8_t *sig, uint sig_len) +{ + const struct checksum_algo *algo = info->checksum; + uint8_t hash[algo->checksum_len]; + struct udevice *dev; + int ret; + + ret = uclass_first_device_err(UCLASS_ECDSA, &dev); + if (ret) { + debug("ECDSA: Could not find ECDSA implementation: %d\n", ret); + return ret; + } + + ret = algo->calculate(algo->name, region, region_count, hash); + if (ret < 0) + return -EINVAL; + + return ecdsa_verify_hash(dev, info, hash, sig, sig_len); +} + +U_BOOT_CRYPTO_ALGO(ecdsa) = { + .name = "ecdsa256", + .key_len = ECDSA256_BYTES, + .verify = ecdsa_verify, +}; + +/* + * uclass definition for ECDSA API + * + * We don't implement any wrappers around ecdsa_ops->verify() because it's + * trivial to call ops->verify(). + */ +UCLASS_DRIVER(ecdsa) = { + .id = UCLASS_ECDSA, + .name = "ecdsa_verifier", +}; |