diff --git a/boot/bootutil/src/bootutil_priv.h b/boot/bootutil/src/bootutil_priv.h index 208d189b9..c45ed6013 100644 --- a/boot/bootutil/src/bootutil_priv.h +++ b/boot/bootutil/src/bootutil_priv.h @@ -265,9 +265,18 @@ struct boot_loader_state { #endif /* MCUBOOT_DIRECT_XIP || MCUBOOT_RAM_LOAD */ }; +/* The function is intended for verification of image hash against + * provided signature. + */ fih_ret bootutil_verify_sig(uint8_t *hash, uint32_t hlen, uint8_t *sig, size_t slen, uint8_t key_id); +/* The function is intended for direct verification of image + * against provided signature. + */ +fih_ret bootutil_verify_img(uint8_t *img, uint32_t size, + uint8_t *sig, size_t slen, uint8_t key_id); + fih_ret boot_fih_memequal(const void *s1, const void *s2, size_t n); int boot_find_status(int image_index, const struct flash_area **fap); diff --git a/boot/bootutil/src/image_ed25519.c b/boot/bootutil/src/image_ed25519.c index 3730e30c2..6b6eb4501 100644 --- a/boot/bootutil/src/image_ed25519.c +++ b/boot/bootutil/src/image_ed25519.c @@ -67,17 +67,23 @@ bootutil_import_key(uint8_t **cp, uint8_t *end) return 0; } -fih_ret -bootutil_verify_sig(uint8_t *hash, uint32_t hlen, uint8_t *sig, size_t slen, - uint8_t key_id) +/* Signature verification base function. + * The function takes buffer of specified length and tries to verify + * it against provided signature. + * The function does key import and checks whether signature is + * of expected length. + */ +static fih_ret +bootutil_verify(uint8_t *buf, uint32_t blen, + uint8_t *sig, size_t slen, + uint8_t key_id) { int rc; FIH_DECLARE(fih_rc, FIH_FAILURE); uint8_t *pubkey; uint8_t *end; - if (hlen != IMAGE_HASH_SIZE || - slen != EDDSA_SIGNATURE_LENGTH) { + if (slen != EDDSA_SIGNATURE_LENGTH) { FIH_SET(fih_rc, FIH_FAILURE); goto out; } @@ -91,7 +97,7 @@ bootutil_verify_sig(uint8_t *hash, uint32_t hlen, uint8_t *sig, size_t slen, goto out; } - rc = ED25519_verify(hash, IMAGE_HASH_SIZE, sig, pubkey); + rc = ED25519_verify(buf, blen, sig, pubkey); if (rc == 0) { /* if verify returns 0, there was an error. */ @@ -105,4 +111,45 @@ bootutil_verify_sig(uint8_t *hash, uint32_t hlen, uint8_t *sig, size_t slen, FIH_RET(fih_rc); } +/* Hash signature verification function. + * Verifies hash against provided signature. + * The function verifies that hash is of expected size and then + * calls bootutil_verify to do the signature verification. + */ +fih_ret +bootutil_verify_sig(uint8_t *hash, uint32_t hlen, + uint8_t *sig, size_t slen, + uint8_t key_id) +{ + FIH_DECLARE(fih_rc, FIH_FAILURE); + + if (hlen != IMAGE_HASH_SIZE) { + FIH_SET(fih_rc, FIH_FAILURE); + goto out; + } + + FIH_CALL(bootutil_verify, fih_rc, hash, IMAGE_HASH_SIZE, sig, + EDDSA_SIGNATURE_LENGTH, key_id); + +out: + FIH_RET(fih_rc); +} + +/* Image verification function. + * The function directly calls bootutil_verify to verify signature + * of image. + */ +fih_ret +bootutil_verify_img(uint8_t *img, uint32_t size, + uint8_t *sig, size_t slen, + uint8_t key_id) +{ + FIH_DECLARE(fih_rc, FIH_FAILURE); + + FIH_CALL(bootutil_verify, fih_rc, img, size, sig, + EDDSA_SIGNATURE_LENGTH, key_id); + + FIH_RET(fih_rc); +} + #endif /* MCUBOOT_SIGN_ED25519 */ diff --git a/boot/bootutil/src/image_validate.c b/boot/bootutil/src/image_validate.c index ae22e27ed..1fde94636 100644 --- a/boot/bootutil/src/image_validate.c +++ b/boot/bootutil/src/image_validate.c @@ -56,6 +56,7 @@ #include "bootutil_priv.h" +#ifndef MCUBOOT_SIGN_PURE /* * Compute SHA hash over the image. * (SHA384 if ECDSA-P384 is being used, @@ -175,6 +176,7 @@ bootutil_img_hash(struct enc_key_data *enc_state, int image_index, return 0; } +#endif /* * Currently, we only support being able to verify one type of @@ -361,6 +363,43 @@ bootutil_get_img_security_cnt(struct image_header *hdr, return 0; } +#if defined(MCUBOOT_SIGN_PURE) +/* Returns: + * 0 -- found + * 1 -- not found or found but not true + * -1 -- failed for some reason + * + * Value of TLV does not matter, presence decides. + */ +static int bootutil_check_for_pure(const struct image_header *hdr, + const struct flash_area *fap) +{ + struct image_tlv_iter it; + uint32_t off; + uint16_t len; + int32_t rc; + + rc = bootutil_tlv_iter_begin(&it, hdr, fap, IMAGE_TLV_SIG_PURE, false); + if (rc) { + return rc; + } + + /* Search for the TLV */ + rc = bootutil_tlv_iter_next(&it, &off, &len, NULL); + if (rc == 0 && len == 1) { + bool val; + + rc = LOAD_IMAGE_DATA(hdr, fap, off, &val, 1); + if (rc == 0) { + rc = !val; + } + } + + return rc; +} +#endif + + #ifndef ALLOW_ROGUE_TLVS /* * The following list of TLVs are the only entries allowed in the unprotected @@ -377,6 +416,9 @@ static const uint16_t allowed_unprot_tlvs[] = { IMAGE_TLV_ECDSA_SIG, IMAGE_TLV_RSA3072_PSS, IMAGE_TLV_ED25519, +#if defined(MCUBOOT_SIGN_PURE) + IMAGE_TLV_SIG_PURE, +#endif IMAGE_TLV_ENC_RSA2048, IMAGE_TLV_ENC_KW, IMAGE_TLV_ENC_EC256, @@ -399,7 +441,6 @@ bootutil_img_validate(struct enc_key_data *enc_state, int image_index, uint32_t off; uint16_t len; uint16_t type; - int image_hash_valid = 0; #ifdef EXPECTED_SIG_TLV FIH_DECLARE(valid_signature, FIH_FAILURE); #ifndef MCUBOOT_BUILTIN_KEY @@ -416,7 +457,10 @@ bootutil_img_validate(struct enc_key_data *enc_state, int image_index, #endif /* EXPECTED_SIG_TLV */ struct image_tlv_iter it; uint8_t buf[SIG_BUF_SIZE]; +#if defined(EXPECTED_HASH_TLV) && !defined(MCUBOOT_SIGN_PURE) + int image_hash_valid = 0; uint8_t hash[IMAGE_HASH_SIZE]; +#endif int rc = 0; FIH_DECLARE(fih_rc, FIH_FAILURE); #ifdef MCUBOOT_HW_ROLLBACK_PROT @@ -425,6 +469,7 @@ bootutil_img_validate(struct enc_key_data *enc_state, int image_index, FIH_DECLARE(security_counter_valid, FIH_FAILURE); #endif +#if defined(EXPECTED_HASH_TLV) && !defined(MCUBOOT_SIGN_PURE) rc = bootutil_img_hash(enc_state, image_index, hdr, fap, tmp_buf, tmp_buf_sz, hash, seed, seed_len); if (rc) { @@ -434,6 +479,15 @@ bootutil_img_validate(struct enc_key_data *enc_state, int image_index, if (out_hash) { memcpy(out_hash, hash, IMAGE_HASH_SIZE); } +#endif + +#if defined(MCUBOOT_SIGN_PURE) + /* If Pure type signature is expected then it has to be there */ + rc = bootutil_check_for_pure(hdr, fap); + if (rc != 0) { + goto out; + } +#endif rc = bootutil_tlv_iter_begin(&it, hdr, fap, IMAGE_TLV_ANY, false); if (rc) { @@ -477,8 +531,10 @@ bootutil_img_validate(struct enc_key_data *enc_state, int image_index, } } #endif - - if (type == EXPECTED_HASH_TLV) { + switch(type) { +#if defined(EXPECTED_HASH_TLV) && !defined(MCUBOOT_SIGN_PURE) + case EXPECTED_HASH_TLV: + { /* Verify the image hash. This must always be present. */ if (len != sizeof(hash)) { rc = -1; @@ -496,8 +552,12 @@ bootutil_img_validate(struct enc_key_data *enc_state, int image_index, } image_hash_valid = 1; + break; + } +#endif /* defined(EXPECTED_HASH_TLV) && !defined(MCUBOOT_SIGN_PURE) */ #ifdef EXPECTED_KEY_TLV - } else if (type == EXPECTED_KEY_TLV) { + case EXPECTED_KEY_TLV: + { /* * Determine which key we should be checking. */ @@ -522,9 +582,12 @@ bootutil_img_validate(struct enc_key_data *enc_state, int image_index, * The key may not be found, which is acceptable. There * can be multiple signatures, each preceded by a key. */ + break; + } #endif /* EXPECTED_KEY_TLV */ #ifdef EXPECTED_SIG_TLV - } else if (type == EXPECTED_SIG_TLV) { + case EXPECTED_SIG_TLV: + { /* Ignore this signature if it is out of bounds. */ if (key_id < 0 || key_id >= bootutil_key_cnt) { key_id = -1; @@ -538,12 +601,25 @@ bootutil_img_validate(struct enc_key_data *enc_state, int image_index, if (rc) { goto out; } +#ifndef MCUBOOT_SIGN_PURE FIH_CALL(bootutil_verify_sig, valid_signature, hash, sizeof(hash), buf, len, key_id); +#else + /* Directly check signature on the image, by using the mapping of + * a device to memory. The pointer is beginning of image in flash, + * so offset of area, the range is header + image + protected tlvs. + */ + FIH_CALL(bootutil_verify_img, valid_signature, (void *)flash_area_get_off(fap), + hdr->ih_hdr_size + hdr->ih_img_size + hdr->ih_protect_tlv_size, + buf, len, key_id); +#endif key_id = -1; + break; + } #endif /* EXPECTED_SIG_TLV */ #ifdef MCUBOOT_HW_ROLLBACK_PROT - } else if (type == IMAGE_TLV_SEC_CNT) { + case IMAGE_TLV_SEC_CNT: + { /* * Verify the image's security counter. * This must always be present. @@ -578,14 +654,21 @@ bootutil_img_validate(struct enc_key_data *enc_state, int image_index, /* The image's security counter has been successfully verified. */ security_counter_valid = fih_rc; + break; + } #endif /* MCUBOOT_HW_ROLLBACK_PROT */ } } +#if defined(EXPECTED_HASH_TLV) && !defined(MCUBOOT_SIGN_PURE) rc = !image_hash_valid; if (rc) { goto out; } +#elif defined(MCUBOOT_SIGN_PURE) + /* This returns true on EQ, rc is err on non-0 */ + rc = FIH_NOT_EQ(valid_signature, FIH_SUCCESS); +#endif #ifdef EXPECTED_SIG_TLV FIH_SET(fih_rc, valid_signature); #endif diff --git a/boot/zephyr/Kconfig b/boot/zephyr/Kconfig index a131c29a3..dc97a1c86 100644 --- a/boot/zephyr/Kconfig +++ b/boot/zephyr/Kconfig @@ -134,6 +134,14 @@ config BOOT_IMG_HASH_ALG_SHA512 endchoice # BOOT_IMG_HASH_ALG +config BOOT_SIGNATURE_TYPE_PURE_ALLOW + bool + help + Hidden option set by configurations that allow Pure variant, + for example ed25519. The pure variant means that image + signature is calculated over entire image instead of hash + of an image. + choice BOOT_SIGNATURE_TYPE prompt "Signature type" default BOOT_SIGNATURE_TYPE_RSA @@ -183,10 +191,31 @@ endif config BOOT_SIGNATURE_TYPE_ED25519 bool "Edwards curve digital signatures using ed25519" - select BOOT_ENCRYPTION_SUPPORT - select BOOT_IMG_HASH_ALG_SHA256_ALLOW + select BOOT_ENCRYPTION_SUPPORT if !BOOT_SIGNATURE_TYPE_PURE + select BOOT_IMG_HASH_ALG_SHA256_ALLOW if !BOOT_SIGNATURE_TYPE_PURE + # The SHA is used only for key hashing, not for images. + select BOOT_SIGNATURE_TYPE_PURE_ALLOW + help + This is ed25519 signature calculated over SHA512 of SHA256 of application + image; that is not completely correct approach as the SHA512 should be + rather directly calculated over an image. + Select BOOT_SIGNATURE_TYPE_PURE to have a PureEdDSA calculating image + signature directly on image, rather than hash of the image. if BOOT_SIGNATURE_TYPE_ED25519 + +config BOOT_SIGNATURE_TYPE_PURE + bool "Use Pure signature of image" + depends on BOOT_SIGNATURE_TYPE_PURE_ALLOW + help + The Pure signature is calculated directly over image rather than + hash of an image. + This is more secure signature, specifically if hardware can do the + verification without need to share key. + Note that this requires that all slots for which signature is to be + verified need to be accessible through memory address space that + cryptography can access. + choice BOOT_ED25519_IMPLEMENTATION prompt "Ecdsa implementation" default BOOT_ED25519_TINYCRYPT diff --git a/boot/zephyr/include/mcuboot_config/mcuboot_config.h b/boot/zephyr/include/mcuboot_config/mcuboot_config.h index a4e0ccefc..88502132b 100644 --- a/boot/zephyr/include/mcuboot_config/mcuboot_config.h +++ b/boot/zephyr/include/mcuboot_config/mcuboot_config.h @@ -148,6 +148,10 @@ #define MCUBOOT_HASH_STORAGE_DIRECTLY #endif +#ifdef CONFIG_BOOT_SIGNATURE_TYPE_PURE +#define MCUBOOT_SIGN_PURE +#endif + #ifdef CONFIG_BOOT_BOOTSTRAP #define MCUBOOT_BOOTSTRAP 1 #endif diff --git a/docs/design.md b/docs/design.md index 8539ae0d7..1598fb2ff 100755 --- a/docs/design.md +++ b/docs/design.md @@ -111,6 +111,8 @@ struct image_tlv { #define IMAGE_TLV_ECDSA_SIG 0x22 /* ECDSA of hash output */ #define IMAGE_TLV_RSA3072_PSS 0x23 /* RSA3072 of hash output */ #define IMAGE_TLV_ED25519 0x24 /* ED25519 of hash output */ +#define IMAGE_TLV_SIG_PURE 0x25 /* If true then any signature found has been + * calculated over image directly. */ #define IMAGE_TLV_ENC_RSA2048 0x30 /* Key encrypted with RSA-OAEP-2048 */ #define IMAGE_TLV_ENC_KW 0x31 /* Key encrypted with AES-KW-128 or 256 */