mirror of
https://github.com/trezor/trezor-firmware.git
synced 2024-11-16 04:29:08 +00:00
396 lines
12 KiB
C
396 lines
12 KiB
C
/*
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* This file is part of the Trezor project, https://trezor.io/
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*
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* Copyright (c) SatoshiLabs
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <string.h>
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#include "ed25519-donna/ed25519.h"
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#include "common.h"
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#include "flash.h"
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#include "image.h"
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#include "model.h"
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_Static_assert(VENDOR_HEADER_MAX_SIZE + IMAGE_HEADER_SIZE <= IMAGE_CHUNK_SIZE,
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"The size of the firmware headers must be less than or equal to "
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"IMAGE_CHUNK_SIZE");
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const uint8_t BOOTLOADER_KEY_M = 2;
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const uint8_t BOOTLOADER_KEY_N = 3;
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static const uint8_t * const BOOTLOADER_KEYS[] = {
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#if !PRODUCTION
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/*** DEVEL/QA KEYS ***/
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(const uint8_t *)"\xd7\x59\x79\x3b\xbc\x13\xa2\x81\x9a\x82\x7c\x76\xad\xb6\xfb\xa8\xa4\x9a\xee\x00\x7f\x49\xf2\xd0\x99\x2d\x99\xb8\x25\xad\x2c\x48",
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(const uint8_t *)"\x63\x55\x69\x1c\x17\x8a\x8f\xf9\x10\x07\xa7\x47\x8a\xfb\x95\x5e\xf7\x35\x2c\x63\xe7\xb2\x57\x03\x98\x4c\xf7\x8b\x26\xe2\x1a\x56",
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(const uint8_t *)"\xee\x93\xa4\xf6\x6f\x8d\x16\xb8\x19\xbb\x9b\xeb\x9f\xfc\xcd\xfc\xdc\x14\x12\xe8\x7f\xee\x6a\x32\x4c\x2a\x99\xa1\xe0\xe6\x71\x48",
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#else
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MODEL_BOOTLOADER_KEYS
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#endif
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};
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static secbool compute_pubkey(uint8_t sig_m, uint8_t sig_n,
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const uint8_t *const *pub, uint8_t sigmask,
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ed25519_public_key res) {
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if (0 == sig_m || 0 == sig_n) return secfalse;
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if (sig_m > sig_n) return secfalse;
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// discard bits higher than sig_n
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sigmask &= ((1 << sig_n) - 1);
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// remove if number of set bits in sigmask is not equal to sig_m
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if (__builtin_popcount(sigmask) != sig_m) return secfalse;
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ed25519_public_key keys[sig_m];
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int j = 0;
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for (int i = 0; i < sig_n; i++) {
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if ((1 << i) & sigmask) {
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memcpy(keys[j], pub[i], 32);
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j++;
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}
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}
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return sectrue * (0 == ed25519_cosi_combine_publickeys(res, keys, sig_m));
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}
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const image_header *read_image_header(const uint8_t *const data,
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const uint32_t magic,
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const uint32_t maxsize) {
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const image_header *hdr = (const image_header *)data;
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if (hdr->magic != magic) {
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return NULL;
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}
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if (hdr->hdrlen != IMAGE_HEADER_SIZE) {
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return NULL;
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}
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// TODO: expiry mechanism needs to be ironed out before production or those
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// devices won't accept expiring bootloaders (due to boardloader write
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// protection).
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// lowest bit is used for breaking compatibility between old TT bootloaders
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// and non TT images
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// which is evaluated in check_image_model function
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if ((hdr->expiry & 0xFFFFFFFE) != 0) return secfalse;
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if (hdr->codelen > (maxsize - hdr->hdrlen)) return secfalse;
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if ((hdr->hdrlen + hdr->codelen) < 4 * 1024) return secfalse;
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if ((hdr->hdrlen + hdr->codelen) % 512 != 0) return secfalse;
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return hdr;
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}
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secbool check_image_model(const image_header *const hdr) {
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// abusing expiry field to break compatibility of non-TT images with existing
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// bootloaders/boardloaders
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#ifdef TREZOR_MODEL_T
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if (hdr->expiry == 0 && hdr->hw_model == 0 && hdr->hw_revision == 0) {
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// images for model TT older than this check
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return sectrue;
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}
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#else
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if ((hdr->expiry & 0x01) == 0) {
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// for models other than TT, expiry == 0 is unacceptable, as the image will
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// run on bootloaders older that this check
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return secfalse;
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}
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#endif
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#ifndef TREZOR_EMULATOR
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if (hdr->hw_model != HW_MODEL) {
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return secfalse;
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}
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if (hdr->hw_revision != HW_REVISION) {
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return secfalse;
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}
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#endif
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return sectrue;
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}
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void get_image_fingerprint(const image_header *const hdr, uint8_t *const out) {
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IMAGE_HASH_CTX ctx;
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IMAGE_HASH_INIT(&ctx);
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IMAGE_HASH_UPDATE(&ctx, (uint8_t *)hdr, IMAGE_HEADER_SIZE - IMAGE_SIG_SIZE);
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for (int i = 0; i < IMAGE_SIG_SIZE; i++) {
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IMAGE_HASH_UPDATE(&ctx, (const uint8_t *)"\x00", 1);
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}
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IMAGE_HASH_FINAL(&ctx, out);
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}
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secbool check_image_header_sig(const image_header *const hdr, uint8_t key_m,
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uint8_t key_n, const uint8_t *const *keys) {
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// check header signature
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uint8_t fingerprint[32];
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get_image_fingerprint(hdr, fingerprint);
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ed25519_public_key pub;
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if (sectrue != compute_pubkey(key_m, key_n, keys, hdr->sigmask, pub))
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return secfalse;
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return sectrue *
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(0 == ed25519_sign_open(fingerprint, IMAGE_HASH_DIGEST_LENGTH, pub,
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*(const ed25519_signature *)hdr->sig));
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}
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secbool __wur read_vendor_header(const uint8_t *const data,
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vendor_header *const vhdr) {
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memcpy(&vhdr->magic, data, 4);
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if (vhdr->magic != 0x565A5254) return secfalse; // TRZV
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memcpy(&vhdr->hdrlen, data + 4, 4);
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if (vhdr->hdrlen > VENDOR_HEADER_MAX_SIZE) return secfalse;
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memcpy(&vhdr->expiry, data + 8, 4);
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if (vhdr->expiry != 0) return secfalse;
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vhdr->origin = data;
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memcpy(&vhdr->version, data + 12, 2);
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memcpy(&vhdr->vsig_m, data + 14, 1);
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memcpy(&vhdr->vsig_n, data + 15, 1);
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memcpy(&vhdr->vtrust, data + 16, 2);
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memcpy(&vhdr->hw_model, data + 18, 4);
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if (vhdr->vsig_n > MAX_VENDOR_PUBLIC_KEYS) {
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return secfalse;
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}
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for (int i = 0; i < vhdr->vsig_n; i++) {
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vhdr->vpub[i] = data + 32 + i * 32;
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}
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for (int i = vhdr->vsig_n; i < MAX_VENDOR_PUBLIC_KEYS; i++) {
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vhdr->vpub[i] = 0;
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}
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memcpy(&vhdr->vstr_len, data + 32 + vhdr->vsig_n * 32, 1);
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vhdr->vstr = (const char *)(data + 32 + vhdr->vsig_n * 32 + 1);
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vhdr->vimg = data + 32 + vhdr->vsig_n * 32 + 1 + vhdr->vstr_len;
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// align to 4 bytes
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vhdr->vimg += (-(uintptr_t)vhdr->vimg) & 3;
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memcpy(&vhdr->sigmask, data + vhdr->hdrlen - IMAGE_SIG_SIZE, 1);
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memcpy(vhdr->sig, data + vhdr->hdrlen - IMAGE_SIG_SIZE + 1,
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IMAGE_SIG_SIZE - 1);
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return sectrue;
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}
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secbool check_vendor_header_model(const vendor_header *const vhdr) {
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#ifdef TREZOR_MODEL_T
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if (vhdr->hw_model == 0) {
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// vendor headers for model T have this field set to 0
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return sectrue;
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}
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#endif
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if (vhdr->hw_model == HW_MODEL) {
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return sectrue;
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}
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return secfalse;
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}
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secbool check_vendor_header_sig(const vendor_header *const vhdr, uint8_t key_m,
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uint8_t key_n, const uint8_t *const *keys) {
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if (vhdr == NULL) {
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return secfalse;
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}
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// check header signature
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uint8_t hash[IMAGE_HASH_DIGEST_LENGTH];
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IMAGE_HASH_CTX ctx;
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IMAGE_HASH_INIT(&ctx);
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IMAGE_HASH_UPDATE(&ctx, vhdr->origin, vhdr->hdrlen - IMAGE_SIG_SIZE);
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for (int i = 0; i < IMAGE_SIG_SIZE; i++) {
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IMAGE_HASH_UPDATE(&ctx, (const uint8_t *)"\x00", 1);
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}
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IMAGE_HASH_FINAL(&ctx, hash);
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ed25519_public_key pub;
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if (sectrue != compute_pubkey(key_m, key_n, keys, vhdr->sigmask, pub))
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return secfalse;
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return sectrue *
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(0 == ed25519_sign_open(hash, IMAGE_HASH_DIGEST_LENGTH, pub,
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*(const ed25519_signature *)vhdr->sig));
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}
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secbool check_vendor_header_keys(const vendor_header *const vhdr) {
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return check_vendor_header_sig(vhdr, BOOTLOADER_KEY_M, BOOTLOADER_KEY_N,
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BOOTLOADER_KEYS);
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}
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void vendor_header_hash(const vendor_header *const vhdr, uint8_t *hash) {
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IMAGE_HASH_CTX ctx;
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IMAGE_HASH_INIT(&ctx);
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IMAGE_HASH_UPDATE(&ctx, (const uint8_t *)vhdr->vstr, vhdr->vstr_len);
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IMAGE_HASH_UPDATE(&ctx, (const uint8_t *)"Trezor Vendor Header", 20);
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IMAGE_HASH_FINAL(&ctx, hash);
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}
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secbool check_single_hash(const uint8_t *const hash, const uint8_t *const data,
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int len) {
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uint8_t s_c[IMAGE_HASH_DIGEST_LENGTH] = {0};
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IMAGE_HASH_CALC(data, len, s_c);
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return sectrue * (0 == memcmp(s_c, hash, IMAGE_HASH_DIGEST_LENGTH));
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}
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secbool check_image_contents(const image_header *const hdr, uint32_t firstskip,
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const flash_area_t *area) {
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if (0 == area) {
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return secfalse;
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}
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// Check the firmware integrity, calculate and compare hashes
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size_t offset = IMAGE_CODE_ALIGN(firstskip);
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size_t end_offset = offset + hdr->codelen;
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// Check area between headers and code
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uint32_t padding_size = offset - firstskip;
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const uint8_t *addr =
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(uint8_t *)flash_area_get_address(area, firstskip, padding_size);
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for (size_t i = 0; i < padding_size; i++) {
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if (*addr++ != 0) {
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return secfalse;
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}
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}
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while (offset < end_offset) {
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size_t bytes_to_check = MIN(IMAGE_CHUNK_SIZE - (offset % IMAGE_CHUNK_SIZE),
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end_offset - offset);
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const void *data = flash_area_get_address(area, offset, bytes_to_check);
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if (!data) {
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return secfalse;
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}
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size_t hash_offset = (offset / IMAGE_CHUNK_SIZE) * 32;
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if (sectrue !=
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check_single_hash(hdr->hashes + hash_offset, data, bytes_to_check)) {
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return secfalse;
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}
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offset += bytes_to_check;
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}
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// Check the padding to the end of the area
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end_offset = flash_area_get_size(area);
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if (offset < end_offset) {
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// Use the first byte in the checked area as the expected padding byte
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// Firmware is always padded with 0xFF, while the bootloader might be
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// padded with 0x00 as well
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uint8_t expected_byte = *(
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(const uint8_t *)flash_area_get_address(area, offset, sizeof(uint8_t)));
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if (expected_byte != 0x00 && expected_byte != 0xFF) {
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return secfalse;
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}
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uint32_t expected_word = expected_byte << 24 | expected_byte << 16 |
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expected_byte << 8 | expected_byte;
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while (offset < end_offset) {
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size_t bytes_to_check = MIN(
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IMAGE_CHUNK_SIZE - (offset % IMAGE_CHUNK_SIZE), end_offset - offset);
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size_t words_to_check = bytes_to_check / sizeof(uint32_t);
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size_t single_bytes_to_check = bytes_to_check % sizeof(uint32_t);
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const uint8_t *bytes = (const uint8_t *)flash_area_get_address(
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area, offset, single_bytes_to_check);
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if (!bytes) {
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return secfalse;
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}
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for (size_t i = 0; i < single_bytes_to_check; i++) {
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if (bytes[i] != expected_byte) {
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return secfalse;
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}
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}
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offset += single_bytes_to_check;
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const uint32_t *data = (const uint32_t *)flash_area_get_address(
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area, offset, bytes_to_check - single_bytes_to_check);
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if (!data) {
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return secfalse;
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}
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for (size_t i = 0; i < words_to_check; i++) {
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if (data[i] != expected_word) {
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return secfalse;
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}
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}
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offset += words_to_check * sizeof(uint32_t);
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}
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}
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return sectrue;
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}
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secbool check_firmware_header(const uint8_t *header, size_t header_size,
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firmware_header_info_t *info) {
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// parse and check vendor header
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vendor_header vhdr;
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if (sectrue != read_vendor_header(header, &vhdr)) {
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return secfalse;
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}
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if (sectrue != check_vendor_header_keys(&vhdr)) {
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return secfalse;
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}
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// parse and check image header
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const image_header *ihdr;
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if ((ihdr = read_image_header(header + vhdr.hdrlen, FIRMWARE_IMAGE_MAGIC,
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FIRMWARE_MAXSIZE)) == NULL) {
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return secfalse;
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}
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if (sectrue !=
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check_image_header_sig(ihdr, vhdr.vsig_m, vhdr.vsig_n, vhdr.vpub)) {
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return secfalse;
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}
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// copy vendor string
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info->vstr_len = MIN(sizeof(info->vstr), vhdr.vstr_len);
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if (info->vstr_len > 0) {
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memcpy(info->vstr, vhdr.vstr, info->vstr_len);
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}
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// copy firmware version
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info->ver_major = ihdr->version & 0xFF;
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info->ver_minor = (ihdr->version >> 8) & 0xFF;
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info->ver_patch = (ihdr->version >> 16) & 0xFF;
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info->ver_build = (ihdr->version >> 24) & 0xFF;
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// calculate and copy the image fingerprint
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get_image_fingerprint(ihdr, info->fingerprint);
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// calculate hash of both vendor and image headers
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IMAGE_HASH_CALC(header, vhdr.hdrlen + ihdr->hdrlen, info->hash);
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return sectrue;
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}
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