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feat(checksum): --checksum-choice/--cc and --checksum-seed for whole-file digest

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Adds real algorithm selection (xxh64 default, plus md5 via OpenSSL EVP) and a
64-bit seed for the per-file whole-file digest used by the --incremental/
--checksum handshake and basis-dir content verification. The seed also feeds
the delta path's per-block xxHash32 strong checksum (low 32 bits) so an
explicit seed deterministically changes those digests too. Sender and receiver
hash identically: the algorithm id and seed cross the config wire frame and the
STATUS_CHECK handshake now carries a length-prefixed, bounded digest instead of
a fixed 64-bit value. Unsupported algorithm names are rejected at parse time
(never a silent no-op). PROTOCOL_VERSION bumped 2.9.0 -> 2.10.0; defaults
(xxh64, seed 0) preserve prior byte-for-byte behavior.
This commit is contained in:
TapTap
2026-09-07 17:42:47 +02:00
parent 6701c103cb
commit 0afda6b094
12 changed files with 316 additions and 43 deletions
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src/shared/file_receive.c
+34 -17
View File
@@ -355,7 +355,8 @@ static File* receive_delta_file(int fd, const Config* config, const char* check_
return NULL;
}
DeltaSignature* sig = delta_signature_create(old_data, old_size, config->delta_block_size);
DeltaSignature* sig = delta_signature_create_seeded(old_data, old_size, config->delta_block_size,
(uint32_t)config->checksum_seed);
if (!sig) {
free(old_data);
*failed = true;
@@ -630,8 +631,8 @@ static bool basis_quick_matches(const Config* config, const struct stat* st, tim
so the caller can materialize the file without re-reading it. */
static bool basis_match_find(const Config* config, const char* check_path,
unsigned long long check_size, time_t check_mtime,
long check_mtime_nsec, uint64_t check_checksum, bool load_content,
BasisMatch* out) {
long check_mtime_nsec, const uint8_t* check_digest,
size_t check_digest_len, bool load_content, BasisMatch* out) {
memset(out, 0, sizeof(*out));
if (!config || !config_has_basis(config) || config->ignore_times)
return false;
@@ -651,10 +652,13 @@ static bool basis_match_find(const Config* config, const char* check_path,
if (basis_quick_matches(config, &st, check_mtime, check_mtime_nsec)) {
Data* content = basis_read_content(fd, check_size);
if (content) {
uint64_t basis_hash = check_size == 0 ? delta_xxhash64("", 0)
: content->data ? delta_xxhash64(content->data, content->size)
: 0;
if (basis_hash == check_checksum) {
uint8_t basis_digest[CHECKSUM_MAX_DIGEST_LEN];
size_t basis_len = 0;
bool hashed = checksum_digest((ChecksumAlgo)config->checksum_algo, config->checksum_seed,
content->data, content->size, basis_digest,
sizeof(basis_digest), &basis_len);
if (hashed && basis_len == check_digest_len && check_digest_len > 0 &&
memcmp(basis_digest, check_digest, check_digest_len) == 0) {
out->hit = true;
out->type = entry->type;
out->basis_path = candidate;
@@ -997,7 +1001,8 @@ File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
unsigned long long check_size;
long long check_mtime;
long long check_mtime_nsec;
uint64_t check_checksum = 0;
uint8_t check_digest[CHECKSUM_MAX_DIGEST_LEN];
size_t check_digest_len = 0;
if (!receive_n_data(fd, &check_size, sizeof(check_size)) ||
!receive_n_data(fd, &check_mtime, sizeof(check_mtime))) {
free(check_path);
@@ -1009,10 +1014,19 @@ File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
send_status(fd, STATUS_ERROR);
return NULL;
}
if ((config->checksum || config_has_basis(config)) &&
!receive_n_data(fd, &check_checksum, sizeof(check_checksum))) {
free(check_path);
return NULL;
if ((config->checksum || config_has_basis(config))) {
uint8_t wire_len;
if (!receive_n_data(fd, &wire_len, sizeof(wire_len)) || wire_len == 0 ||
wire_len > CHECKSUM_MAX_DIGEST_LEN) {
free(check_path);
send_status(fd, STATUS_ERROR);
return NULL;
}
check_digest_len = wire_len;
if (!receive_n_data(fd, check_digest, check_digest_len)) {
free(check_path);
return NULL;
}
}
if (check_size > MAX_RECEIVE_WHOLE_FILE_SIZE) {
@@ -1098,10 +1112,13 @@ File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
skipped and the transfer proceeds with the full new contents. */
bool match = false;
if (checksum_needs_read) {
if (old_size == 0)
match = delta_xxhash64("", 0) == check_checksum;
else
match = old_data != NULL && delta_xxhash64(old_data, (size_t)old_size) == check_checksum;
uint8_t old_digest[CHECKSUM_MAX_DIGEST_LEN];
size_t old_len = 0;
bool hashed = checksum_digest((ChecksumAlgo)config->checksum_algo, config->checksum_seed,
old_size == 0 ? "" : old_data, (size_t)old_size, old_digest,
sizeof(old_digest), &old_len);
match = hashed && old_len == check_digest_len && check_digest_len > 0 &&
memcmp(old_digest, check_digest, check_digest_len) == 0;
} else if (size_equal && !config->ignore_times) {
match = config->size_only || match_by_metadata;
}
@@ -1125,7 +1142,7 @@ File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
if (config_has_basis(config)) {
BasisMatch basis;
basis_match_find(config, check_path, check_size, (time_t)check_mtime, (long)check_mtime_nsec,
check_checksum, true, &basis);
check_digest, check_digest_len, true, &basis);
if (basis.hit) {
if (basis.type == BASIS_DEST_COMPARE) {
/* compare-dest never copies: an exact match only suppresses the data