// Fetch a block from the host into fd->curr_block and fd->block_data.
// Returns 0 on successful fetch, negative otherwise.
static int fetch_block(struct fuse_data* fd, uint32_t block) {
if (block == fd->curr_block) {
return 0;
}
if (block >= fd->file_blocks) {
memset(fd->block_data, 0, fd->block_size);
fd->curr_block = block;
return 0;
}
if (block_cache_fetch(fd, block) == 0) {
fd->curr_block = block;
return 0;
}
size_t fetch_size = fd->block_size;
if (block * fd->block_size + fetch_size > fd->file_size) {
// If we're reading the last (partial) block of the file,
// expect a shorter response from the host, and pad the rest
// of the block with zeroes.
fetch_size = fd->file_size - (block * fd->block_size);
memset(fd->block_data + fetch_size, 0, fd->block_size - fetch_size);
}
int result = fd->vtab->read_block(fd->cookie, block, fd->block_data, fetch_size);
if (result < 0) return result;
fd->curr_block = block;
// Verify the hash of the block we just got from the host.
//
// - If the hash of the just-received data matches the stored hash
// for the block, accept it.
// - If the stored hash is all zeroes, store the new hash and
// accept the block (this is the first time we've read this
// block).
// - Otherwise, return -EINVAL for the read.
uint8_t hash[SHA256_DIGEST_SIZE];
SHA256_hash(fd->block_data, fd->block_size, hash);
uint8_t* blockhash = fd->hashes + block * SHA256_DIGEST_SIZE;
if (memcmp(hash, blockhash, SHA256_DIGEST_SIZE) == 0) {
return 0;
}
int i;
for (i = 0; i < SHA256_DIGEST_SIZE; ++i) {
if (blockhash[i] != 0) {
fd->curr_block = -1;
return -EIO;
}
}
memcpy(blockhash, hash, SHA256_DIGEST_SIZE);
block_cache_enter(fd, block);
return 0;
}
void bootimage_done(bootimage *img) {
unsigned sz = img->next_offset;
if (sz & 4095) {
sz += (4096 - (sz & 4095));
}
img->entry[1].info.image_size = sz;
img->entry[1].info.entry_count = img->count;
SHA256_hash((void*) &(img->entry[1]), 4096 - 64, img->entry[0].file.sha256);
}
void hash_payload(mpz_t hashed, mpz_t payload) {
int i;
char payload_str[strlen(DHE_PRIME)]; //not going to be hashing anything larger
char hex_hash[HEX_HASH_STR_LEN];
gmp_sprintf(payload_str, "%Zx", payload);
memcpy(hex_hash, SHA256_hash(payload_str), HEX_HASH_STR_LEN);
gmp_sscanf(hex_hash, "%Zx", hashed);
}
const uint8_t *DCRYPTO_SHA256_hash(const void *data, uint32_t n,
uint8_t *digest)
{
if (dcrypto_grab_sha_hw())
/* dcrypto_sha_wait() will release the hw. */
dcrypto_sha_hash(SHA256_MODE, data, n, digest);
#ifndef SECTION_IS_RO
else
SHA256_hash(data, n, digest);
#endif
return digest;
}
bootentry_file *bootimage_add_filedata(bootimage *img, unsigned type, void *data, unsigned len) {
unsigned n = img->count;
if (img->count == 64) return NULL;
img->count++;
// align to page boundary
img->next_offset = (img->next_offset + 4095) & (~4095);
img->entry[n].file.kind = KIND_FILE;
img->entry[n].file.type = type;
img->entry[n].file.offset = img->next_offset;
img->entry[n].file.length = len;
SHA256_hash(data, len, img->entry[n].file.sha256);
img->data[n] = data;
img->offset[n] = img->next_offset;
img->length[n] = len;
img->next_offset += len;
return &(img->entry[n].file);
}
