#include "config.h" #include "charset.h" #include "credentials.h" #include "daemon_conf.h" #include "delay_updates.h" #include "file.h" #include "identity.h" #include "log.h" #include "motd.h" #include "multiprocessing.h" #include "protocol.h" #include "queue.h" #include "receiver.h" #include "server_cli.h" #include "transport_tcp.h" #include "transport_tls.h" #include "utils.h" #include #include #include #include #include #include #include #include #include #include #include static char* authorized_root; static int authorized_root_fd = -1; static bool allow_delete; static bool trust_sender; static bool allow_unauthenticated; /* --no-super operator veto: forces SUPER_MODE_OFF for every connection (even * root), so no super-user activity is attempted and any client --copy-as is * refused. Set once in main before the accept loop / stdio handler. */ static bool server_no_super; static const char* required_client_cn; /* --iconv CONVERT_SPEC the server was itself started with (borrowed argv * pointer). Its LOCAL half may override the local charset the client assumed; * see charset_wire_init_receiver. */ static const char* server_iconv_spec; /* Non-NULL exactly when the listener runs in --daemon mode. Loaded once in * main before any accept-loop fork, then shared read-only by every forked * connection child (and their threads). */ static DaemonConf* g_daemon_conf = NULL; /* Daemon credential store (Wave B), loaded once in main from --password-file / * --early-input and shared read-only by every forked connection child. When a * module declares `auth users` but no store was configured, the daemon refuses * to start (fail closed); the store is never NULL after a successful start when * such a module exists. */ static CredentialStore* g_credentials = NULL; /* Opaque context threaded through to the config-frame gate: the connection's * SSL object (NULL over plaintext) so the gate can warn when a credential * exchange is not encrypted, plus the super-mode override the gate decides on. * The gate never mutates the received (const) Config; it records a forced * SUPER_MODE_OFF here and the handler applies it exactly once after acceptance. */ typedef struct ModuleGateContext { SSL* ssl; /* The connection descriptor, so the gate can drive the SCRAM auth handshake * while it still owns the config-frame exchange (before the STATUS_OK ack). */ int fd; /* SUPER_MODE_OFF when this connection must not attempt any super-user activity (operator --no-super, or a daemon module without the `client owner = yes` opt-in); -1 when the config's own mode stands. */ int super_mode_override; } ModuleGateContext; /* Server half of the SCRAM challenge/response (A7 remediation, protocol * 2.19.0). Sends STATUS_AUTH_CHALLENGE (iteration count, base64 salt, base64 * server nonce), expects STATUS_AUTH_RESPONSE (base64 client nonce, base64 * ClientProof), verifies the proof constant-time and answers STATUS_AUTH_OK * with the base64 ServerSignature. On any failure BEFORE the success response * it sends exactly one generic STATUS_AUTH_FAILED and returns false; a failure * while writing the success signature cannot send a status and just drops an * already-broken connection. The verifier for an unknown/off-list * user is a dummy (deterministic per-username salt, store-wide iterations, dummy * keys, found=false) so the same math runs and no user-enumeration/timing oracle * is exposed. */ static bool server_auth_handshake(int fd, const Config* config, const DaemonModule* module) { bool result = false; CredentialVerifier verifier; memset(&verifier, 0, sizeof(verifier)); uint8_t snonce[CREDENTIAL_NONCE_LEN] = {0}; char salt_b64[25] = {0}; char snonce_b64[45] = {0}; char* cnonce_b64 = NULL; char* proof_b64 = NULL; uint8_t cnonce[CREDENTIAL_NONCE_LEN] = {0}; uint8_t proof[CREDENTIAL_KEY_LEN] = {0}; uint8_t server_sig[CREDENTIAL_KEY_LEN] = {0}; char sig_b64[45] = {0}; size_t cnonce_len = 0; size_t proof_len = 0; if (!config->auth_user) goto fail; /* no username: generic failure, no challenge */ if (!credentials_get_verifier(g_credentials, config->auth_user, (const char* const*)module->auth_users, module->auth_user_count, &verifier)) goto fail; /* a crypto failure still owes the gate a terminal frame */ if (!(credentials_random_bytes(snonce, sizeof(snonce)) && credentials_b64_encode(verifier.salt, CREDENTIAL_SALT_LEN, salt_b64, sizeof(salt_b64)) && credentials_b64_encode(snonce, sizeof(snonce), snonce_b64, sizeof(snonce_b64)))) goto fail; if (!(send_status(fd, STATUS_AUTH_CHALLENGE) && send_int(fd, (int)verifier.iters) && send_str(fd, salt_b64) && send_str(fd, snonce_b64))) goto fail; Status status = STATUS_ERROR; if (!(receive_status(fd, &status) && status == STATUS_AUTH_RESPONSE)) goto fail; cnonce_b64 = receive_str_redacted(fd); proof_b64 = receive_str_redacted(fd); if (!(cnonce_b64 && proof_b64 && credentials_b64_decode(cnonce_b64, cnonce, sizeof(cnonce), &cnonce_len) && cnonce_len == CREDENTIAL_NONCE_LEN && credentials_b64_decode(proof_b64, proof, sizeof(proof), &proof_len) && proof_len == CREDENTIAL_KEY_LEN)) goto fail; if (!credentials_verify_response(&verifier, config->auth_user, snonce, cnonce, proof, server_sig)) goto fail; /* Success writes exactly one terminal frame (STATUS_AUTH_OK). A broken pipe * while sending the signature just drops the connection; it must never emit a * second terminal status. */ result = credentials_b64_encode(server_sig, sizeof(server_sig), sig_b64, sizeof(sig_b64)) && send_status(fd, STATUS_AUTH_OK) && send_str_redacted(fd, sig_b64); goto cleanup; fail: /* Every failure path writes exactly one generic terminal status, satisfying * the gate's CONFIG_VALIDATE_ALREADY_TERMINATED contract. */ send_status(fd, STATUS_AUTH_FAILED); cleanup: credentials_burn(cnonce_b64, cnonce_b64 ? strlen(cnonce_b64) : 0); credentials_burn(proof_b64, proof_b64 ? strlen(proof_b64) : 0); free(cnonce_b64); free(proof_b64); credentials_burn((char*)snonce, sizeof(snonce)); credentials_burn(salt_b64, sizeof(salt_b64)); credentials_burn(snonce_b64, sizeof(snonce_b64)); credentials_burn((char*)cnonce, sizeof(cnonce)); credentials_burn((char*)proof, sizeof(proof)); credentials_burn((char*)server_sig, sizeof(server_sig)); credentials_burn(sig_b64, sizeof(sig_b64)); credentials_burn((char*)verifier.salt, sizeof(verifier.salt)); credentials_burn((char*)verifier.stored_key, sizeof(verifier.stored_key)); credentials_burn((char*)verifier.server_key, sizeof(verifier.server_key)); return result; } /* Aggregate payload bytes the multithreaded receiver may buffer ahead of the slow disk writer. Receiving one more chunk adds up to ~2 * MAX_CHUNK_SIZE of transient wire/decompression buffers on top of the queued payloads, so this ceiling keeps total per-connection receive memory (decompressed and per-file copied chunk buffers included) within MAX_CONNECTION_MEMORY. */ #define RECEIVER_QUEUE_MAX_BYTES (MAX_CONNECTION_MEMORY - 2 * MAX_CHUNK_SIZE) static bool tls_client_identity_allowed(SSL* ssl) { if (!ssl || !required_client_cn) return false; X509* certificate = SSL_get1_peer_certificate(ssl); if (!certificate) return false; char common_name[256]; int length = X509_NAME_get_text_by_NID(X509_get_subject_name(certificate), NID_commonName, common_name, sizeof(common_name)); size_t required_length = strlen(required_client_cn); bool allowed = length >= 0 && (size_t)length == required_length && required_length < sizeof(common_name) && credentials_secure_equal(common_name, required_client_cn, required_length); X509_free(certificate); return allowed; } static void release_authorization(void) { file_set_authorized_root(-1, NULL); utils_set_authorized_root_fd(-1); if (authorized_root_fd >= 0) close(authorized_root_fd); authorized_root_fd = -1; free(authorized_root); authorized_root = NULL; } static bool path_is_within(const char* root, const char* path) { size_t n = strlen(root); return strncmp(root, path, n) == 0 && (path[n] == '\0' || path[n] == '/'); } /* --mkpath contract: when the client's destination root directory does not exist yet on the server side, --mkpath tells the server to create it (and any missing leading components) below the authorized root at connection start. Without --mkpath the destination root must already exist: a missing root is rejected up front instead of being silently invented by a later write. Both paths are confined to the authorized root by the secure file helpers. */ static bool ensure_receive_root(const Config* config) { if (!config || !config->receive_root_directory) return false; if (config->mkpath) return file_ensure_directory_secure(config->receive_root_directory); return file_directory_exists_secure(config->receive_root_directory); } static bool configure_authorization(const char* root) { char resolved[PATH_MAX]; if (!root) { file_set_authorized_root(-1, NULL); utils_set_authorized_root(-1, NULL); return false; } int root_fd = open(root, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC); if (root_fd < 0) { file_set_authorized_root(-1, NULL); utils_set_authorized_root(-1, NULL); return false; } char fd_path[64]; int fd_path_length = snprintf(fd_path, sizeof(fd_path), "/proc/self/fd/%d", root_fd); if (fd_path_length < 0 || (size_t)fd_path_length >= sizeof(fd_path) || !realpath(fd_path, resolved)) { close(root_fd); file_set_authorized_root(-1, NULL); utils_set_authorized_root(-1, NULL); return false; } authorized_root = str_dup(resolved); if (!authorized_root) { close(root_fd); file_set_authorized_root(-1, NULL); utils_set_authorized_root(-1, NULL); return false; } authorized_root_fd = root_fd; if (!file_set_authorized_root(authorized_root_fd, authorized_root) || !utils_set_authorized_root(authorized_root_fd, authorized_root)) { file_set_authorized_root(-1, NULL); utils_set_authorized_root(-1, NULL); close(authorized_root_fd); authorized_root_fd = -1; free(authorized_root); authorized_root = NULL; return false; } return true; } /* Discriminates the outcome of the A7 auth gate so the dispatcher can map it * back to the config_receive_with_validate contract: accepted (including * "module needs no auth"), a config-level refusal carrying an error string, or * a handshake that already wrote its own terminal status frame. */ typedef enum { MODULE_AUTH_ACCEPTED = 0, MODULE_AUTH_REFUSED, MODULE_AUTH_TERMINATED, } ModuleAuthResult; /* Looks up the daemon module selected by the client's config frame and rejects * a `read only` one (every FastSync network transfer writes; there is no * read-only wire operation yet). Returns the module, or NULL with *error set * to the caller-facing rejection message. */ static const DaemonModule* module_gate_lookup_module(const Config* config, const char** error) { const DaemonModule* module = daemon_conf_find_module(g_daemon_conf, config->module); if (module == NULL) { char* escaped_module = output_escape(config->module, config->eight_bit_output); log_message(LOG_LEVEL_ERROR, "unknown daemon module '%s' requested", escaped_module ? escaped_module : ""); free(escaped_module); *error = "requested daemon module does not exist"; return NULL; } if (module->read_only) { log_message(LOG_LEVEL_ERROR, "daemon module '%s' is read only; refusing write transfer", config->module); *error = "requested daemon module is read only"; return NULL; } return module; } /* Per-module client-chosen ownership / super-user policy (P7 Wave E hardening): * a daemon module refuses EVERY ownership-affecting request (--numeric-ids, * --chown, --usermap/--groupmap, --fake-super, --copy-as, explicit --super) * unless the operator opted THIS module in with `client owner = yes`. * Otherwise any client could force arbitrary ownership inside the module root. * The ownership check is evaluated against the ORIGINAL config so an explicit * --super is refused even when an operator --no-super veto already forced the * effective copy to OFF (the veto must not silently convert a refusal into an * accept); when no ownership flag is present, super-user DEVICE activities are * forced off for this connection instead. Returns an error string on refusal, * NULL on acceptance. */ static const char* module_gate_check_ownership(const Config* config, const DaemonModule* module, ModuleGateContext* gate_ctx) { if (module->client_owner) return NULL; /* Ownership: refuse the whole transfer up front (a clear failure). */ if (identity_ownership_requested(config)) { log_message(LOG_LEVEL_ERROR, "daemon module '%s' refuses client-chosen ownership/super-user activities " "(no `client owner = yes` opt-in); refusing", config->module); return "client-chosen ownership is not permitted by this daemon module"; } /* Super-user DEVICE activities (char/block mknod and --write-devices) are permitted under the default AUTO mode, so without this override a root daemon would still let a non-opted module create arbitrary device nodes and write raw devices. Force them off for this connection: those entries are skipped (never mknod'ed) while an ordinary `-a` push still succeeds without device nodes, matching the operator's least-privilege choice. The operator-level --no-super veto is already folded into this. */ if (gate_ctx) gate_ctx->super_mode_override = SUPER_MODE_OFF; return NULL; } /* A7 auth gate: runs the SCRAM challenge/response for an auth-required module * BEFORE the module root is installed and before any data moves. Returns * MODULE_AUTH_ACCEPTED when the module needs no auth or the handshake succeeds, * MODULE_AUTH_REFUSED with *error set on a config-level rejection, or * MODULE_AUTH_TERMINATED when the handshake already wrote a terminal status. */ static ModuleAuthResult module_gate_authenticate(const Config* config, const DaemonModule* module, ModuleGateContext* gate_ctx, const char** error) { if (module->auth_user_count == 0) return MODULE_AUTH_ACCEPTED; /* Fail closed: no store -> refuse (server misconfiguration, STATUS_ERROR). */ if (g_credentials == NULL) { log_message(LOG_LEVEL_ERROR, "daemon module '%s' requires authentication but no credential store is " "configured (--password-file/--early-input); refusing", config->module); *error = "requested daemon module requires authentication and no credential " "store is configured"; return MODULE_AUTH_REFUSED; } /* Transport policy (A7-3/S1): an auth-required module only accepts * credentials over (a) an encrypted, verified TLS connection whose client * certificate matches --client-cn, or (b) an actual PLAINTEXT connection * from a loopback peer that the operator explicitly opted into with * --allow-unauthenticated. A remote plaintext peer, an un-flagged loopback * plaintext peer, and a loopback TLS peer whose certificate does not match * --client-cn are all refused HERE, before the challenge is sent, so an * unverified client never receives a nonce: the loopback allowance requires * !gate_ctx->ssl, so --tls + --allow-unauthenticated can never be used to * bypass the client-CN check. The operator flag never permits REMOTE * plaintext auth: remote peers still require verified TLS regardless. */ bool tls_ok = gate_ctx && gate_ctx->ssl && SSL_get_verify_result(gate_ctx->ssl) == X509_V_OK && tls_client_identity_allowed(gate_ctx->ssl); bool local_ok = allow_unauthenticated && gate_ctx && !gate_ctx->ssl && gate_ctx->fd >= 0 && utils_fd_peer_is_local(gate_ctx->fd); if (!tls_ok && !local_ok) { log_message(LOG_LEVEL_ERROR, "daemon module '%s' requires authentication over an encrypted, verified TLS " "connection (or an opted-in loopback plaintext transport); refusing", config->module); *error = "daemon module requires authentication over an encrypted, verified TLS " "connection"; return MODULE_AUTH_REFUSED; } /* Belt-and-braces: the transport policy above already guarantees a context * with a usable socket (verified TLS implies a live SSL object and loopback * allowance requires gate_ctx->fd >= 0), so this is unreachable today; keep * the guard so the handshake can never be driven over an invalid fd. */ if (!gate_ctx || gate_ctx->fd < 0) { log_message(LOG_LEVEL_ERROR, "daemon module '%s': no auth transport available", config->module); *error = "authentication failed for the requested daemon module"; return MODULE_AUTH_REFUSED; } /* The handshake writes exactly one terminal status on failure and signals so * via MODULE_AUTH_TERMINATED; the username may be logged (never the password * or any derived proof). */ if (!server_auth_handshake(gate_ctx->fd, config, module)) { char* escaped_user = config->auth_user ? output_escape(config->auth_user, config->eight_bit_output) : NULL; log_message(LOG_LEVEL_ERROR, "daemon module '%s': authentication failed for user '%s'", config->module, escaped_user ? escaped_user : "(none)"); free(escaped_user); return MODULE_AUTH_TERMINATED; } char* escaped_user = output_escape(config->auth_user, config->eight_bit_output); log_message(LOG_LEVEL_INFO, "daemon module '%s': user '%s' authenticated", config->module, escaped_user ? escaped_user : ""); free(escaped_user); return MODULE_AUTH_ACCEPTED; } /* Installs the module's configured path as the connection's authorized root. * Returns an error string when the root is unusable, NULL on success. */ static const char* module_gate_install_root(const Config* config, const DaemonModule* module) { if (!configure_authorization(module->path)) { log_message(LOG_LEVEL_ERROR, "daemon module '%s' path '%s' is not usable", config->module, module->path ? module->path : "(null)"); return "requested daemon module root is not usable"; } return NULL; } /* Config-frame gate (runs inside config_receive_with_validate, BEFORE the * STATUS_OK ack, so a rejected connection is refused at the config handshake * and no file data is ever exchanged). * * Plain mode: a connection that carries a daemon module name is refused (the * standalone server simply does not offer modules; honouring one would silently * change what the destination means). Empty module -> accept. * * Daemon mode: the client MUST select a module (host::module/path). The * requested module is looked up in the daemon config and its configured `path` * becomes the authorized root via configure_authorization -- exactly the same * root confinement the standalone server applies to its single * --destination-root, but per-module and NEVER client-chosen. The module is * refused (with a clear log) when it is unknown, when it is `read only` (every * FastSync network transfer writes; there is no read-only wire operation yet), * when it requests client-chosen ownership without the module's * `client owner = yes` opt-in (P7 Wave E hardening), or when the presented * daemon credentials fail for a module that declares `auth users`. Wave A * refused every auth-required module (auth was not yet implemented); Wave B * authenticates the client instead (see below). */ static const char* server_module_gate(const Config* config, void* context) { ModuleGateContext* gate_ctx = (ModuleGateContext*)context; if (!config) return "missing config frame"; /* Operator veto: --no-super forces SUPER_MODE_OFF for this connection before the copy-as gate is evaluated. The received config is const, so the gates below evaluate a shallow effective copy (only super_mode differs); the handler applies the recorded override to the accepted config exactly once. */ Config effective = *config; if (server_no_super) { effective.super_mode = SUPER_MODE_OFF; if (gate_ctx) gate_ctx->super_mode_override = SUPER_MODE_OFF; } /* --copy-as (P7 Wave E, protocol 2.18.0): FastSync's safe subset forces the ownership of every written entry to the requested ids, which needs a privileged (root) receiver. An unprivileged receiver REFUSES the whole transfer here, at the config handshake and BEFORE the STATUS_OK ack, so no file data is exchanged and there is never a silent wrong-ownership result. The daemon's per-module client-chosen-ownership refusal is enforced after the module lookup below (it needs the module's opt-in) and covers --copy-as like every other ownership flag. */ if (identity_copy_as_refused(&effective)) { if (geteuid() != 0) log_message(LOG_LEVEL_ERROR, "--copy-as requires a privileged receiver (root); refusing"); else log_message(LOG_LEVEL_ERROR, "--copy-as refused: super-user activities are disabled by the server " "(--no-super); refusing"); return "cannot perform --copy-as on this receiver"; } /* --iconv (protocol 2.16.0): the receiver's exact conversion direction (the client spec's wire charset into this server's local charset, including a server-side --iconv override) must be usable BEFORE the STATUS_OK ack, so an impossible conversion is refused at the handshake instead of failing the first file mid-transfer. The client spec itself was already sanity checked by validate_received_config. */ if (config->iconv_spec && !charset_wire_receiver_spec_valid(config->iconv_spec, server_iconv_spec)) return "client --iconv conversion cannot be honored by this server"; bool is_daemon = g_daemon_conf != NULL; bool has_module = config->module != NULL && config->module[0] != '\0'; if (!is_daemon) { if (has_module) return "client requested a daemon module but this server is not running " "with --daemon"; return NULL; } if (!has_module) return "daemon connection did not select a module (expected a " "host::module/path destination)"; const char* error = NULL; const DaemonModule* module = module_gate_lookup_module(config, &error); if (!module) return error; error = module_gate_check_ownership(config, module, gate_ctx); if (error) return error; switch (module_gate_authenticate(config, module, gate_ctx, &error)) { case MODULE_AUTH_REFUSED: return error; case MODULE_AUTH_TERMINATED: return CONFIG_VALIDATE_ALREADY_TERMINATED; case MODULE_AUTH_ACCEPTED: break; } /* accepted; the authorized root is now the module's path */ return module_gate_install_root(config, module); } void handler(int file_descriptor) { SSL* ssl = io_get_ssl(); ProtocolSession session; protocol_session_init(&session, file_descriptor, file_descriptor); protocol_session_set_ssl(&session, ssl); protocol_session_bind(&session); ModuleGateContext gate_ctx; gate_ctx.ssl = ssl; gate_ctx.fd = file_descriptor; gate_ctx.super_mode_override = -1; /* All teardown state starts empty so the single `done` epilogue is safe to * reach from any error path (including before the config frame arrives). */ Config* config = NULL; PipelineContextReceiver* context = NULL; char* joined_destination = NULL; bool charset_ready = false; config = config_receive_with_validate(file_descriptor, server_module_gate, &gate_ctx); if (config == NULL) { log_message(LOG_LEVEL_ERROR, "Failed to receive config"); goto done; } /* Apply the super-mode veto the gate decided on (operator --no-super, or a * daemon module without the `client owner = yes` opt-in) exactly once, so * every downstream gate (identity_apply_ownership via privilege_super_permitted, * device-node creation) sees SUPER_MODE_OFF. The gate never mutated the * received config. */ if (gate_ctx.super_mode_override != -1) config->super_mode = (SuperMode)gate_ctx.super_mode_override; protocol_set_8_bit_output(config->eight_bit_output); if (!authorized_root) { log_message(LOG_LEVEL_ERROR, "No server-side destination root configured"); goto done; } if (!allow_unauthenticated && ssl == NULL) { log_message(LOG_LEVEL_ERROR, "Rejected unauthenticated plaintext connection"); goto done; } if (ssl && required_client_cn && !tls_client_identity_allowed(ssl)) { log_message(LOG_LEVEL_ERROR, "Rejected TLS client with unauthorized identity"); goto done; } /* Daemon mode: the module's root is the authorized root (installed by server_module_gate), and the client's destination is a MODULE-RELATIVE path. Reject an absolute destination up front so the module-relative confinement contract is never eroded by a client that tries to address the module root by absolute path. */ if (g_daemon_conf && config->receive_root_directory && config->receive_root_directory[0] == '/') { log_message(LOG_LEVEL_ERROR, "Rejected absolute daemon destination (must be relative to the " "selected module root)"); goto done; } char* destination = config->receive_root_directory; if (destination && destination[0] != '/') joined_destination = path_cat(authorized_root, destination); if (joined_destination) destination = joined_destination; if (!destination || has_path_traversal(destination) || !path_is_within(authorized_root, destination)) { log_message(LOG_LEVEL_ERROR, "Rejected destination outside authorized root"); free(joined_destination); joined_destination = NULL; goto done; } if (joined_destination) { free(config->receive_root_directory); config->receive_root_directory = joined_destination; joined_destination = NULL; } if (!config->receive_root_directory) { goto done; } config->use_delete = config->use_delete && allow_delete; /* --iconv (protocol 2.16.0): install the receiver-side wire->local conversion now that the client's full CONVERT_SPEC has been received and validated, before any received file name is decoded. The server's own --iconv (if any) may override the local charset; a spec the client is known to have validated cannot fail here unless the server's override names an unsupported charset. */ if (config->iconv_spec) { if (!charset_wire_init_receiver(config->iconv_spec, server_iconv_spec)) { log_message(LOG_LEVEL_ERROR, "--iconv: unsupported charset conversion requested (LOCAL[,REMOTE])"); goto done; } charset_ready = true; } /* --delete-missing-args deletes destination mirrors receiver-side, so it is deletion and stays gated by the same --allow-delete server policy. When the server policy is off the flag is inert (the missing entries are still skipped via its implied --ignore-missing-args, but nothing is deleted). */ config->delete_missing_args = config->delete_missing_args && allow_delete; /* --mkpath: create the destination root (and its missing leading components) before anything else; without it the root must pre-exist. A failure here aborts the connection cleanly before any file data is exchanged. */ if (!ensure_receive_root(config)) { char* escaped_root = output_escape(config->receive_root_directory, log_get_8_bit_output()); log_message(LOG_LEVEL_ERROR, "destination root is not available: %s", escaped_root ? escaped_root : ""); free(escaped_root); goto done; } /* A --delay-updates transfer stages under a private 0700 directory inside the receive root. Create it up front (wiping leftovers of any previously interrupted delayed transfer) so a fully-skipped run also starts clean. */ if (config->delay_updates) { config->delay_context = delay_updates_context_create(config->receive_root_directory); if (!config->delay_context || !delay_updates_prepare(config->delay_context)) { log_message(LOG_LEVEL_ERROR, "Failed to initialize --delay-updates staging area"); goto done; } } /* Preserve the negotiated identity policy for the fd-relative ownership apply path. Each connection is its own forked process, so this per-process snapshot never races another connection. A failed deep copy (allocation failure) leaves the snapshot cleared, so refuse the connection rather than silently applying the wrong ownership policy. */ if (!identity_set_active(config)) { log_message(LOG_LEVEL_ERROR, "Failed to activate identity policy"); goto done; } /* Persist the negotiated --keep-dirlinks policy once, here at config-accept, before any multithreaded receiver/writer threads are spawned, so the fd-walk reads a stable value during the whole transfer (and never bleeds across the per-connection forked processes). */ file_set_keep_dirlinks(config->keep_dirlinks); /* --trust-sender is a LOCAL receiver policy: it never crosses the wire (so a wire peer can never enable it). The standalone server only honours it when its own CLI was started with --trust-sender (the client forwards that switch into the remote argv via --remote-option=--trust-sender; the server then parses it here and applies the policy below). Set before any multithreaded receiver/writer threads are spawned so the fd-walk reads a stable value during the whole transfer, and never bleeds across the per-connection forked processes. Off by default. */ file_set_trust_sender(trust_sender); /* Wave C MOTD: on the daemon listener path only, once the module gate + auth have accepted and every destination check has passed, send the configured `motd file` as the first server->client frame before any transfer data (rsync sends its MOTD as the first thing from the server on a daemon connection). Every daemon connection gets the frame -- an unset or unreadable motd file sends an empty string -- so the client's read is deterministic and an absent file is never an error. The --stdio SSH path has no MOTD (g_daemon_conf is NULL there). No PROTOCOL_VERSION bump: the frame is symmetric server->client in every 2.15.0 daemon build (see the Wave C note in config.h). */ if (g_daemon_conf) { char* motd = motd_read_file(g_daemon_conf->global.motd_file); if (!motd_send(file_descriptor, motd ? motd : "")) { free(motd); log_message(LOG_LEVEL_ERROR, "Failed to send daemon MOTD"); goto done; } free(motd); } if (config->use_multithreading) { Queue* q = queue_create(100, file_destroy); if (q == NULL) goto done; context = pipeline_context_receiver_create(config, q, file_descriptor, ssl); if (context == NULL) { queue_destroy(q); goto done; } protocol_session_set_max_alloc(&context->session, config->max_alloc); atomic_store(&context->session.total_allocated_bytes, atomic_load(&session.total_allocated_bytes)); pipeline_context_receiver_set_queue_byte_limit(context, RECEIVER_QUEUE_MAX_BYTES); thrd_t receiver = {0}; thrd_t writer = {0}; bool receiver_created = thrd_create(&receiver, receive_thread, context) == thrd_success; bool writer_created = false; if (receiver_created) writer_created = thrd_create(&writer, write_thread, context) == thrd_success; if (!receiver_created || !writer_created) { log_perror("Error creating Threads"); if (receiver_created) { mtx_lock(&context->mutex); atomic_store(&context->cancelled, true); cnd_broadcast(&context->condition_not_full); cnd_broadcast(&context->condition_not_empty); mtx_unlock(&context->mutex); /* Unblock a worker parked in socket I/O without closing the fd (the * child owns the single close). shutdown() only affects sockets; for * the --stdio pipe the receiver's per-message poll timeout still * bounds the join, so do nothing there rather than close a descriptor * another thread may still be using. */ struct stat fd_stat; if (fstat(file_descriptor, &fd_stat) == 0 && S_ISSOCK(fd_stat.st_mode)) shutdown(file_descriptor, SHUT_RDWR); thrd_join(receiver, NULL); } if (writer_created) thrd_join(writer, NULL); goto done; } int receiver_result; int writer_result; thrd_join(receiver, &receiver_result); thrd_join(writer, &writer_result); bool transfer_ok = receiver_result == thrd_success && writer_result == thrd_success; if (transfer_ok) { /* Commit-style (late) deletion: receive_thread handed the keep-set manifest here instead of deleting while write_thread might still be draining, so by now every file is on disk and the whole transfer is known to have succeeded. Remove the extras before publishing a --delay-updates run; the walker skips the staging directory. */ if (context->deferred_manifest) { if (!manifest_delete_all(config, context->deferred_manifest)) { transfer_ok = false; } delete_manifest_free(context->deferred_manifest); context->deferred_manifest = NULL; } } if (transfer_ok) { /* --delay-updates: receive_thread has finished the whole protocol stream (including manifest/delete handling) and write_thread has drained its queue, so every staged file is complete. Publish atomically before the success/outcome frame so a --remove-source-files sender only learns of files that were actually installed. */ if (config->delay_updates && config->delay_context && !delay_updates_publish(config->delay_context, config)) { transfer_ok = false; } /* P7 Wave D: all writers have joined and the late deletion (and --delay-updates publication) has committed above, so it is finally safe to stamp directory times; a directory's mtime must not be clobbered by its children or by an extra removal. */ if (transfer_ok) dir_time_list_apply(&context->dir_times, config->receive_root_directory); } if (transfer_ok) { if (!receiver_send_final_success(file_descriptor, config, &context->outcomes)) transfer_ok = false; } else { send_status(file_descriptor, STATUS_ERROR); } if (!transfer_ok) log_message(LOG_LEVEL_ERROR, "Transfer failed"); } else { if (receiver_receive_files(config, file_descriptor) != 0) log_message(LOG_LEVEL_ERROR, "Transfer failed"); } done: /* Single cleanup epilogue: every error path jumps here, so the iconv * receiver conversion is released, the identity snapshot cleared, the * protocol session unbound and the config freed exactly once. The * connection fd is deliberately NOT closed here -- the child functions own * its single close (plain_child_fn / tls_child_fn), and the --stdio call * site must leave stdin/stdout open. */ if (charset_ready) charset_wire_free(); /* The delay-updates staging tree is released by config_delete (which the branch below always reaches), so it is cleaned exactly once. */ identity_clear_active(); protocol_session_unbind(); if (context != NULL) { /* context owns both the config and the queue it was created with. */ pipeline_context_receiver_destroy(context); context = NULL; config = NULL; } else { config_delete(config); config = NULL; } free(joined_destination); } #ifndef FASTSYNC_SERVER_AS_LIB static Server* g_server = NULL; static void cleanup(int sig) { (void)sig; if (g_server) server_delete(&g_server); daemon_conf_free(g_daemon_conf); g_daemon_conf = NULL; credentials_free(g_credentials); g_credentials = NULL; _exit(0); } static void print_server_usage(void) { printf("FastSync Server\n"); printf("Usage: fastsync-server [options]\n\n"); printf("Options:\n"); printf(" --stdio Run in stdio mode (SSH transport)\n"); printf(" --daemon Run as a persistent daemon listener using a module\n"); printf(" config file (-p/config port; default 873)\n"); printf(" --config=FILE Daemon config file (default: ~/.config/fastsync/\n"); printf(" fastsyncd.conf, else /etc/fastsyncd.conf)\n"); printf(" --dparam=KEY=VALUE Override one global config key on the command line\n"); printf(" (port, motd file, address)\n"); printf(" --no-detach Stay in the foreground (default detaches to\n"); printf(" background when running --daemon)\n"); printf(" --password-file=FILE Credential store for modules that declare\n"); printf(" 'auth users' (line format:\n"); printf(" user:$fastsync$1$pbkdf2-sha256$iters$salt$stored$server,\n"); printf(" generated by --hash-credentials). Legacy\n"); printf(" user:SHA256HEX lines are rejected. Requires\n"); printf(" --daemon; an auth-required module with no store\n"); printf(" refuses to start\n"); printf(" --early-input=FILE Second credential store layered over\n"); printf(" --password-file (same format); usually a secrets-\n"); printf(" manager/process-substitution file. Requires --daemon\n"); printf(" -p TCP port (default: 8080, range: 1-65535)\n"); printf(" --tls Enable TLS encryption\n"); printf(" --cert TLS certificate file (PEM)\n"); printf(" --key TLS private key file (PEM)\n"); printf(" --ca TLS CA certificate file (PEM)\n"); printf(" --client-cn TLS client certificate CN (mandatory with --tls)\n"); printf(" --destination-root Authorized destination root (default: .)\n"); printf(" --address Bind the listening socket to this address\n"); printf(" -4, --ipv4 Bind an IPv4 socket (default)\n"); printf(" -6, --ipv6 Bind an IPv6 socket\n"); printf(" --allow-delete Permit manifest deletion\n"); printf(" --trust-sender Trust the remote sender's file list\n"); printf(" --no-super Operator veto: never attempt super-user activities\n"); printf(" (ownership, device nodes) even as root, and refuse\n"); printf(" any client --copy-as/--super request\n"); printf(" --iconv=LOCAL[,REMOTE] Declare this server's LOCAL charset for file-name\n"); printf(" conversion: received names are translated to this\n"); printf(" charset (the wire charset still comes from the\n"); printf(" client's CONVERT_SPEC). A name that cannot be\n"); printf(" represented fails the run cleanly\n"); printf(" --allow-unauthenticated Allow plaintext/anonymous network clients\n"); printf(" (an auth-required module still accepts only opted-in\n"); printf(" loopback plaintext; remote auth requires verified TLS)\n"); printf(" --hash-credentials Read 's user:password lines and print\n"); printf(" PBKDF2 credential-store lines to stdout, then exit.\n"); printf(" Use the output as --password-file for --daemon;\n"); printf(" redirect it to an owner-only (0600) file\n"); printf(" --iterations N PBKDF2 iteration count for --hash-credentials\n"); printf(" (default %u, range %u-%u)\n", CREDENTIAL_DEFAULT_ITERS, CREDENTIAL_MIN_ITERS, CREDENTIAL_MAX_ITERS); printf(" -v, --verbose Enable debug logging\n"); printf(" --help Show this help\n"); } /* Resolve the daemon config default: ~/.config/fastsync/fastsyncd.conf when it * exists (or when HOME is set), otherwise /etc/fastsyncd.conf. Returns a * pointer to a static buffer (never NULL). */ static const char* default_daemon_config_path(void) { const char* home = getenv("HOME"); if (home && *home) { static char user_path[PATH_MAX]; int n = snprintf(user_path, sizeof(user_path), "%s/.config/fastsync/fastsyncd.conf", home); if (n > 0 && (size_t)n < sizeof(user_path) && access(user_path, R_OK) == 0) return user_path; } /* Fall back to the traditional system path. */ return "/etc/fastsyncd.conf"; } /* Detach from the controlling terminal: fork, exit the parent, and make the * surviving child a session leader (setsid) with stdio redirected to * /dev/null. The listening socket is already open (bound in main before this * runs), so it is inherited by the background daemon. Returns true on * success (in the daemon's own process). */ static bool daemonize(void) { pid_t pid = fork(); if (pid < 0) return false; if (pid > 0) _exit(0); if (setsid() < 0) return false; pid = fork(); if (pid < 0) return false; if (pid > 0) _exit(0); int devnull = open("/dev/null", O_RDWR); if (devnull >= 0) { dup2(devnull, STDIN_FILENO); dup2(devnull, STDOUT_FILENO); dup2(devnull, STDERR_FILENO); if (devnull > STDERR_FILENO) close(devnull); } /* Do not pin the launch CWD (module-relative 'path' entries would resolve * against an unstable working directory) and drop the restrictive host umask * so modules can create files/dirs with the modes the config requests. */ if (chdir("/") != 0) log_message(LOG_LEVEL_WARNING, "daemon: chdir to / failed: %s", strerror(errno)); umask(0); return true; } int main(int argc, char* argv[]) { ServerCliOptions opts; char cli_err[512]; int parse_result = server_cli_parse(argc, argv, &opts, cli_err, sizeof(cli_err)); if (parse_result == 1) { print_server_usage(); return 0; } if (parse_result < 0) { server_cli_options_free(&opts); fprintf(stderr, "Error: %s\n", cli_err); print_server_usage(); return 1; } /* --hash-credentials: standalone offline tool; read user:password lines and * emit new-format credential-store lines, then exit. */ if (opts.hash_credentials_file) { uint32_t iters = opts.hash_iterations_set ? opts.hash_iterations : CREDENTIAL_DEFAULT_ITERS; /* The output is secret material: if it is redirected to a regular file, * warn when that file is group/other-accessible (the store must be 0600). */ struct stat out_st; if (fstat(STDOUT_FILENO, &out_st) == 0 && S_ISREG(out_st.st_mode) && (out_st.st_mode & (S_IRWXG | S_IRWXO)) != 0) fprintf(stderr, "Warning: credential-store output is a group/other-accessible file; restrict it to " "mode 0600 (chmod 600)\n"); char hash_err[512]; if (credentials_hash_file(opts.hash_credentials_file, iters, stdout, hash_err, sizeof(hash_err)) != 0) { fprintf(stderr, "Error: %s\n", hash_err); server_cli_options_free(&opts); return 1; } server_cli_options_free(&opts); return 0; } int exit_code = 0; signal(SIGPIPE, SIG_IGN); if (opts.verbose) { set_log_level(LOG_LEVEL_DEBUG); set_log_debug_flags(LOG_DEBUG_ALL); } if (opts.tls_ca && !opts.use_tls) log_message(LOG_LEVEL_WARNING, "--ca has no effect without --tls"); /* Persist the parsed server policies into the process-global policy state * BEFORE the stdio branch: an SSH-launched `--stdio` server (whose argv came * from the client via --remote-option and friends) must honor --allow-delete, * --trust-sender and --client-cn exactly like the standalone listener. */ required_client_cn = opts.client_cn; allow_delete = opts.allow_delete; trust_sender = opts.trust_sender; allow_unauthenticated = opts.allow_unauthenticated; server_no_super = opts.no_super; server_iconv_spec = opts.iconv_spec; signal(SIGINT, cleanup); signal(SIGTERM, cleanup); if (opts.stdio_mode) { /* SSH authenticates the stdio transport outside of FastSync. */ allow_unauthenticated = true; if (!configure_authorization(opts.destination_root)) { char* escaped = output_escape(opts.destination_root, false); fprintf(stderr, "Error: invalid destination root '%s'\n", escaped ? escaped : ""); free(escaped); server_cli_options_free(&opts); return 1; } io_set_fds(STDIN_FILENO, STDOUT_FILENO); /* handler() does not own the stdio fds: it never closes its descriptor * argument, so STDIN/STDOUT stay open for this (single-shot) SSH session * and are released by process exit. */ handler(STDIN_FILENO); release_authorization(); server_cli_options_free(&opts); return 0; } int port = opts.port; int bind_family = opts.bind_family; const char* bind_address = opts.bind_address; if (opts.daemon_mode) { const char* config_path = opts.config_path ? opts.config_path : default_daemon_config_path(); g_daemon_conf = daemon_conf_load(config_path, cli_err, sizeof(cli_err)); if (!g_daemon_conf) { server_cli_options_free(&opts); fprintf(stderr, "Error: %s\n", cli_err); return 1; } for (int i = 0; i < opts.dparam_count; i++) { if (daemon_conf_apply_dparam(g_daemon_conf, opts.dparams[i], cli_err, sizeof(cli_err)) != 0) { fprintf(stderr, "Error: --dparam: %s\n", cli_err); exit_code = 1; goto out; } } /* Effective port: -p (highest) > --dparam port > config port (default 873). */ if (!opts.port_set) port = g_daemon_conf->global.port; if (!bind_address) bind_address = g_daemon_conf->global.address; if (g_daemon_conf->module_count == 0) log_message(LOG_LEVEL_WARNING, "daemon config has no modules; every connection will be refused"); /* Surface the operator's client-chosen-ownership opt-in prominently: an opted-in module lets its clients request arbitrary owner ids inside that module root. */ for (int i = 0; i < g_daemon_conf->module_count; i++) { if (g_daemon_conf->modules[i].client_owner) log_message(LOG_LEVEL_WARNING, "daemon module '%s' allows client-chosen ownership and super-user device " "activities (`client owner = yes`); clients may request arbitrary owner ids " "and device nodes within that module root -- pair it with `auth users` " "unless the module is intentionally open to the network", g_daemon_conf->modules[i].name); } /* Daemon credential store (Wave B). --password-file and --early-input * feed the same store, loaded BEFORE the listener forks so every * connection child shares one read-only store. Fail closed at startup: a * module that declares `auth users` without a store (or with an empty * store) refuses to start rather than serving a module whose credentials * can never be verified. */ g_credentials = credentials_load(opts.password_file, opts.early_input_file, cli_err, sizeof(cli_err)); if (!g_credentials) { server_cli_options_free(&opts); fprintf(stderr, "Error: %s\n", cli_err); return 1; } bool credential_source_given = opts.password_file != NULL || opts.early_input_file != NULL; for (int i = 0; i < g_daemon_conf->module_count; i++) { const DaemonModule* module = &g_daemon_conf->modules[i]; if (module->auth_user_count == 0) continue; if (!credential_source_given) { fprintf(stderr, "Error: module '%s' declares 'auth users' but no credential store was given " "(--password-file or --early-input); refusing to start (fail closed)\n", module->name); server_cli_options_free(&opts); return 1; } if (credentials_store_size(g_credentials) == 0) { fprintf(stderr, "Error: module '%s' declares 'auth users' but the credential store is empty; " "refusing to start (fail closed)\n", module->name); server_cli_options_free(&opts); return 1; } for (int j = 0; j < module->auth_user_count; j++) { if (!credentials_store_has(g_credentials, module->auth_users[j])) log_message(LOG_LEVEL_WARNING, "daemon module '%s': auth user '%s' has no credential store entry; that " "user can never authenticate", module->name, module->auth_users[j]); } } } else { if (!configure_authorization(opts.destination_root)) { char* escaped = output_escape(opts.destination_root, false); fprintf(stderr, "Error: invalid destination root '%s'\n", escaped ? escaped : ""); free(escaped); server_cli_options_free(&opts); return 1; } } ServerBindOptions bind_opts; bind_opts.bind_address = bind_address; bind_opts.family = bind_family; g_server = server_create_ex(port, &bind_opts); if (!g_server) { log_message(LOG_LEVEL_ERROR, "Failed to create server"); release_authorization(); exit_code = 1; goto out; } if (opts.use_tls) { if (!opts.tls_cert || !opts.tls_key || !opts.tls_ca || !opts.client_cn) { fprintf(stderr, "Error: --tls requires --cert, --key, --ca, and --client-cn\n"); server_delete(&g_server); release_authorization(); exit_code = 1; goto out; } tls_global_init(); if (!server_create_tls(g_server, opts.tls_cert, opts.tls_key, opts.tls_ca)) { log_message(LOG_LEVEL_ERROR, "Failed to set up TLS"); server_delete(&g_server); release_authorization(); exit_code = 1; goto out; } } /* Detach after the listening socket (and TLS context) exist so the * background daemon inherits a fully-bound listener. --no-detach runs in * the foreground, which is how tests drive the daemon. */ if (opts.daemon_mode && !opts.no_detach) { if (!daemonize()) { log_message(LOG_LEVEL_ERROR, "Failed to daemonize"); server_delete(&g_server); release_authorization(); exit_code = 1; goto out; } } if (opts.use_tls) server_listen_tls(g_server, handler); else server_listen(g_server, handler); server_delete(&g_server); release_authorization(); out: daemon_conf_free(g_daemon_conf); g_daemon_conf = NULL; credentials_free(g_credentials); g_credentials = NULL; server_cli_options_free(&opts); return exit_code; } #endif