Exemplo n.º 1
0
bool BusyWithNewProtocol(EvalContext *ctx, ServerConnectionState *conn)
{
    /* The CF_BUFEXT extra space is there to ensure we're not reading out of
     * bounds in commands that carry extra binary arguments, like MD5. */
    char recvbuffer[CF_BUFSIZE + CF_BUFEXT] = { 0 };
    char sendbuffer[CF_BUFSIZE] = { 0 };
    char filename[CF_BUFSIZE + 1];      /* +1 for appending slash sometimes */
    int received;
    ServerFileGetState get_args = { 0 };

    /* We already encrypt because of the TLS layer, no need to encrypt more. */
    const int encrypted = 0;

    /* Legacy stuff only for old protocol. */
    assert(conn->rsa_auth == 1);
    assert(conn->user_data_set == 1);

    /* Receive up to CF_BUFSIZE - 1 bytes. */
    received = ReceiveTransaction(conn->conn_info, recvbuffer, NULL);
    if (received == -1 || received == 0)
    {
        return false;
    }

    if (strlen(recvbuffer) == 0)
    {
        Log(LOG_LEVEL_WARNING, "Got NULL transmission, skipping!");
        return true;
    }

    /* Don't process request if we're signalled to exit. */
    if (IsPendingTermination())
    {
        Log(LOG_LEVEL_VERBOSE, "Server must exit, closing connection");
        return false;
    }

    /* TODO break recvbuffer here: command, param1, param2 etc. */

    switch (GetCommandNew(recvbuffer))
    {
    case PROTOCOL_COMMAND_EXEC:
    {
        /* TODO check it is always file, never directory, no end with '/' */
        char args[256];
        int ret = sscanf(recvbuffer, "EXEC %255[^\n]", args);
        if (ret != 1)                    /* No arguments, use default args. */
        {
            args[0] = '\0';
        }

        if (!AllowedUser(conn->username))
        {
            Log(LOG_LEVEL_INFO, "EXEC denied due to not allowed user: %s",
                conn->username);
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        char arg0[PATH_MAX];
        size_t zret = CommandArg0_bound(arg0, CFRUNCOMMAND, sizeof(arg0));
        if (zret == (size_t) -1)
        {
            goto protocol_error;
        }

        zret = PreprocessRequestPath(arg0, sizeof(arg0));
        if (zret == (size_t) -1)
        {
            goto protocol_error;
        }


        /* TODO EXEC should not just use paths_acl access control, but
         * specific "path_exec" ACL. Then different command execution could be
         * allowed per host, and the host could even set argv[0] in his EXEC
         * request, rather than only the arguments. */

        if (acl_CheckPath(paths_acl, arg0,
                          conn->ipaddr, conn->revdns,
                          KeyPrintableHash(ConnectionInfoKey(conn->conn_info)))
            == false)
        {
            Log(LOG_LEVEL_INFO, "EXEC denied due to ACL for file: %s", arg0);
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        if (!MatchClasses(ctx, conn))
        {
            Log(LOG_LEVEL_INFO, "EXEC denied due to failed class match");
            Terminate(conn->conn_info);
            return true;
        }

        DoExec(ctx, conn, args);
        Terminate(conn->conn_info);
        return true;
    }
    case PROTOCOL_COMMAND_VERSION:

        snprintf(sendbuffer, sizeof(sendbuffer), "OK: %s", Version());
        SendTransaction(conn->conn_info, sendbuffer, 0, CF_DONE);
        return true;

    case PROTOCOL_COMMAND_GET:
    {
        int ret = sscanf(recvbuffer, "GET %d %[^\n]",
                         &(get_args.buf_size), filename);

        if (ret != 2 ||
            get_args.buf_size <= 0 || get_args.buf_size > CF_BUFSIZE)
        {
            goto protocol_error;
        }

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Received:", "GET", filename);

        /* TODO batch all the following in one function since it's very
         * similar in all of GET, OPENDIR and STAT. */

        size_t zret = ShortcutsExpand(filename, sizeof(filename),
                                     SV.path_shortcuts,
                                     conn->ipaddr, conn->revdns,
                                     KeyPrintableHash(ConnectionInfoKey(conn->conn_info)));
        if (zret == (size_t) -1)
        {
            goto protocol_error;
        }

        zret = PreprocessRequestPath(filename, sizeof(filename));
        if (zret == (size_t) -1)
        {
            goto protocol_error;
        }

        PathRemoveTrailingSlash(filename, strlen(filename));

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Translated to:", "GET", filename);

        if (acl_CheckPath(paths_acl, filename,
                          conn->ipaddr, conn->revdns,
                          KeyPrintableHash(ConnectionInfoKey(conn->conn_info)))
            == false)
        {
            Log(LOG_LEVEL_INFO, "access denied to GET: %s", filename);
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        memset(sendbuffer, 0, sizeof(sendbuffer));

        if (get_args.buf_size >= CF_BUFSIZE)
        {
            get_args.buf_size = 2048;
        }

        /* TODO eliminate! */
        get_args.conn = conn;
        get_args.encrypt = false;
        get_args.replybuff = sendbuffer;
        get_args.replyfile = filename;

        CfGetFile(&get_args);

        return true;
    }
    case PROTOCOL_COMMAND_OPENDIR:
    {
        memset(filename, 0, sizeof(filename));
        int ret = sscanf(recvbuffer, "OPENDIR %[^\n]", filename);
        if (ret != 1)
        {
            goto protocol_error;
        }

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Received:", "OPENDIR", filename);

        /* sizeof()-1 because we need one extra byte for
           appending '/' afterwards. */
        size_t zret = ShortcutsExpand(filename, sizeof(filename) - 1,
                                      SV.path_shortcuts,
                                      conn->ipaddr, conn->revdns,
                                      KeyPrintableHash(ConnectionInfoKey(conn->conn_info)));
        if (zret == (size_t) -1)
        {
            goto protocol_error;
        }

        zret = PreprocessRequestPath(filename, sizeof(filename) - 1);
        if (zret == (size_t) -1)
        {
            goto protocol_error;
        }

        /* OPENDIR *must* be directory. */
        PathAppendTrailingSlash(filename, strlen(filename));

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Translated to:", "OPENDIR", filename);

        if (acl_CheckPath(paths_acl, filename,
                          conn->ipaddr, conn->revdns,
                          KeyPrintableHash(ConnectionInfoKey(conn->conn_info)))
            == false)
        {
            Log(LOG_LEVEL_INFO, "access denied to OPENDIR: %s", filename);
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        CfOpenDirectory(conn, sendbuffer, filename);
        return true;
    }
    case PROTOCOL_COMMAND_SYNCH:
    {
        long time_no_see = 0;
        memset(filename, 0, sizeof(filename));
        int ret = sscanf(recvbuffer, "SYNCH %ld STAT %[^\n]",
                         &time_no_see, filename);

        if (ret != 2 || filename[0] == '\0')
        {
            goto protocol_error;
        }

        time_t tloc = time(NULL);
        if (tloc == -1)
        {
            /* Should never happen. */
            Log(LOG_LEVEL_ERR, "Couldn't read system clock. (time: %s)", GetErrorStr());
            SendTransaction(conn->conn_info, "BAD: clocks out of synch", 0, CF_DONE);
            return true;
        }

        time_t trem = (time_t) time_no_see;
        int drift = (int) (tloc - trem);

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Received:", "STAT", filename);

        /* sizeof()-1 because we need one extra byte for
           appending '/' afterwards. */
        size_t zret = ShortcutsExpand(filename, sizeof(filename) - 1,
                                      SV.path_shortcuts,
                                      conn->ipaddr, conn->revdns,
                                      KeyPrintableHash(ConnectionInfoKey(conn->conn_info)));
        if (zret == (size_t) -1)
        {
            goto protocol_error;
        }

        zret = PreprocessRequestPath(filename, sizeof(filename) - 1);
        if (zret == (size_t) -1)
        {
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        if (IsDirReal(filename) == 1)
        {
            PathAppendTrailingSlash(filename, strlen(filename));
        }
        else
        {
            PathRemoveTrailingSlash(filename, strlen(filename));
        }

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Translated to:", "STAT", filename);

        if (acl_CheckPath(paths_acl, filename,
                          conn->ipaddr, conn->revdns,
                          KeyPrintableHash(ConnectionInfoKey(conn->conn_info)))
            == false)
        {
            Log(LOG_LEVEL_INFO, "access denied to STAT: %s", filename);
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        if (DENYBADCLOCKS && (drift * drift > CLOCK_DRIFT * CLOCK_DRIFT))
        {
            snprintf(sendbuffer, sizeof(sendbuffer),
                     "BAD: Clocks are too far unsynchronized %ld/%ld",
                     (long) tloc, (long) trem);
            Log(LOG_LEVEL_INFO, "denybadclocks %s", sendbuffer);
            SendTransaction(conn->conn_info, sendbuffer, 0, CF_DONE);
            return true;
        }
        else
        {
            Log(LOG_LEVEL_DEBUG, "Clocks were off by %ld", (long) tloc - (long) trem);
            StatFile(conn, sendbuffer, filename);
        }

        return true;
    }
    case PROTOCOL_COMMAND_MD5:
    {
        int ret = sscanf(recvbuffer, "MD5 %[^\n]", filename);
        if (ret != 1)
        {
            goto protocol_error;
        }

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Received:", "MD5", filename);

        /* TODO batch all the following in one function since it's very
         * similar in all of GET, OPENDIR and STAT. */

        size_t zret = ShortcutsExpand(filename, sizeof(filename),
                                     SV.path_shortcuts,
                                     conn->ipaddr, conn->revdns,
                                     KeyPrintableHash(ConnectionInfoKey(conn->conn_info)));
        if (zret == (size_t) -1)
        {
            goto protocol_error;
        }

        zret = PreprocessRequestPath(filename, sizeof(filename));
        if (zret == (size_t) -1)
        {
            goto protocol_error;
        }

        PathRemoveTrailingSlash(filename, strlen(filename));

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Translated to:", "MD5", filename);

        if (acl_CheckPath(paths_acl, filename,
                          conn->ipaddr, conn->revdns,
                          KeyPrintableHash(ConnectionInfoKey(conn->conn_info)))
            == false)
        {
            Log(LOG_LEVEL_INFO, "access denied to file: %s", filename);
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        assert(CF_DEFAULT_DIGEST_LEN <= EVP_MAX_MD_SIZE);
        unsigned char digest[EVP_MAX_MD_SIZE + 1];

        assert(CF_BUFSIZE + CF_SMALL_OFFSET + CF_DEFAULT_DIGEST_LEN
               <= sizeof(recvbuffer));
        memcpy(digest, recvbuffer + strlen(recvbuffer) + CF_SMALL_OFFSET,
               CF_DEFAULT_DIGEST_LEN);

        CompareLocalHash(filename, digest, sendbuffer);
        SendTransaction(conn->conn_info, sendbuffer, 0, CF_DONE);

        return true;
    }
    case PROTOCOL_COMMAND_VAR:
    {
        char var[256];
        int ret = sscanf(recvbuffer, "VAR %255[^\n]", var);
        if (ret != 1)
        {
            goto protocol_error;
        }

        /* TODO if this is literals_acl, then when should I check vars_acl? */
        if (acl_CheckExact(literals_acl, var,
                           conn->ipaddr, conn->revdns,
                           KeyPrintableHash(ConnectionInfoKey(conn->conn_info)))
            == false)
        {
            Log(LOG_LEVEL_INFO, "access denied to variable: %s", var);
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        GetServerLiteral(ctx, conn, sendbuffer, recvbuffer, encrypted);
        return true;
    }
    case PROTOCOL_COMMAND_CONTEXT:
    {
        char client_regex[256];
        int ret = sscanf(recvbuffer, "CONTEXT %255[^\n]", client_regex);
        if (ret != 1)
        {
            goto protocol_error;
        }

        /* WARNING: this comes from legacy code and must be killed if we care
         * about performance. We should not accept regular expressions from
         * the client, but this will break backwards compatibility.
         *
         * I replicated the code in raw form here to emphasize complexity,
         * it's the only *slow* command currently in the protocol.  */

        Item *persistent_classes = ListPersistentClasses();
        Item *matched_classes = NULL;

        /* For all persistent classes */
        for (Item *ip = persistent_classes; ip != NULL; ip = ip->next)
        {
            const char *class_name = ip->name;

            /* Does this class match the regex the client sent? */
            if (StringMatchFull(client_regex, class_name))
            {
                /* For all ACLs */
                for (size_t i = 0; i < classes_acl->len; i++)
                {
                    struct resource_acl *racl = &classes_acl->acls[i];

                    /* Does this ACL apply to this host? */
                    if (access_CheckResource(racl, conn->ipaddr, conn->revdns,
                                             KeyPrintableHash(ConnectionInfoKey(conn->conn_info)))
                        == true)
                    {
                        const char *allowed_classes_regex =
                            classes_acl->resource_names->list[i]->str;

                        /* Does this ACL admits access for this class to the
                         * connected host? */
                        if (StringMatchFull(allowed_classes_regex, class_name))
                        {
                            PrependItem(&matched_classes, class_name, NULL);
                        }
                    }
                }
            }
        }

        if (matched_classes == NULL)
        {
            Log(LOG_LEVEL_INFO,
                "No allowed classes for remoteclassesmatching: %s",
                client_regex);
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        ReplyServerContext(conn, encrypted, matched_classes);
        return true;
    }
    case PROTOCOL_COMMAND_QUERY:
    {
        char query[256], name[128];
        int ret1 = sscanf(recvbuffer, "QUERY %255[^\n]", query);
        int ret2 = sscanf(recvbuffer, "QUERY %127s", name);
        if (ret1 != 1 || ret2 != 1)
        {
            goto protocol_error;
        }

        if (acl_CheckExact(query_acl, name,
                           conn->ipaddr, conn->revdns,
                           KeyPrintableHash(ConnectionInfoKey(conn->conn_info)))
            == false)
        {
            Log(LOG_LEVEL_INFO, "access denied to query: %s", query);
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        if (GetServerQuery(conn, recvbuffer, encrypted))
        {
            return true;
        }

        break;
    }
    case PROTOCOL_COMMAND_CALL_ME_BACK:

        if (acl_CheckExact(query_acl, "collect_calls",
                           conn->ipaddr, conn->revdns,
                           KeyPrintableHash(ConnectionInfoKey(conn->conn_info)))
            == false)
        {
            Log(LOG_LEVEL_INFO,
                "access denied to Call-Collect, check the ACL for class: collect_calls");
            return false;
        }

        ReceiveCollectCall(conn);
        /* On success that returned true; otherwise, it did all
         * relevant Log()ging.  Either way, it closed the connection,
         * so we're no longer busy with it: */
        return false;

    case PROTOCOL_COMMAND_BAD:

        Log(LOG_LEVEL_WARNING, "Unexpected protocol command: %s", recvbuffer);
    }

    /* We should only reach this point if something went really bad, and
     * close connection. In all other cases (like access denied) connection
     * shouldn't be closed.

     * TODO So we need this function to return more than true/false, because
     * now we return true even when access is denied! E.g. return -1 for
     * error, 0 on success, 1 on access denied. It can be an option if
     * connection will close on denial. */

protocol_error:
    strcpy(sendbuffer, "BAD: Request denied");
    SendTransaction(conn->conn_info, sendbuffer, 0, CF_DONE);
    Log(LOG_LEVEL_INFO, "Closing connection due to request: %s", recvbuffer);
    return false;
}
Exemplo n.º 2
0
static void KeepFileAccessPromise(const EvalContext *ctx, const Promise *pp)
{
    char path[PATH_MAX];
    size_t path_len = strlen(pp->promiser);
    if (path_len > sizeof(path) - 1)
    {
        goto err_too_long;
    }
    memcpy(path, pp->promiser, path_len + 1);

    /* Resolve symlinks and canonicalise access_rules path. */
    size_t ret2 = PreprocessRequestPath(path, sizeof(path));

    if (ret2 == (size_t) -1)
    {
        if (errno != ENOENT)                        /* something went wrong */
        {
            Log(LOG_LEVEL_ERR,
                "Failed to canonicalize path '%s' in access_rules, ignoring!",
                pp->promiser);
            return;
        }
        else                      /* file does not exist, it doesn't matter */
        {
            Log(LOG_LEVEL_INFO,
                "Path does not exist, it's added as-is in access rules: %s",
                path);
            Log(LOG_LEVEL_INFO,
                "WARNING: this means that (not) having a trailing slash defines if it's (not) a directory!");
            /* Legacy: convert trailing "/." to "/" */
            if (path_len >= 2 &&
                path[path_len - 1] == '.' &&
                path[path_len - 2] == '/')
            {
                path[path_len - 1] = '\0';
                path_len--;
            }
        }
    }
    else                                 /* file exists, path canonicalised */
    {
        /* If it's a directory append trailing '/' */
        path_len = ret2;
        int is_dir = IsDirReal(path);
        if (is_dir == 1 && path[path_len - 1] != FILE_SEPARATOR)
        {
            if (path_len + 2 > sizeof(path))
            {
                goto err_too_long;
            }
            PathAppendTrailingSlash(path, path_len);
            path_len++;
        }
    }

    size_t pos = acl_SortedInsert(&paths_acl, path);
    if (pos == (size_t) -1)
    {
        /* Should never happen, besides when allocation fails. */
        Log(LOG_LEVEL_CRIT, "acl_Insert: %s", GetErrorStr());
        exit(255);
    }

    /* Legacy code */
    if (path_len != 1)
    {
        DeleteSlash(path);
    }
    Auth *ap = GetOrCreateAuth(path, &SV.admit, &SV.admittail);
    Auth *dp = GetOrCreateAuth(path, &SV.deny, &SV.denytail);

    AccessPromise_AddAccessConstraints(ctx, pp, &paths_acl->acls[pos],
                                       ap, dp);
    return;

  err_too_long:
    Log(LOG_LEVEL_ERR,
        "Path '%s' in access_rules is too long (%zu > %d), ignoring!",
        pp->promiser, strlen(pp->promiser), PATH_MAX);
    return;
}
Exemplo n.º 3
0
/**
 * Currently this function returns false when we want the connection
 * closed, and true, when we want to proceed further with requests.
 *
 * @TODO So we need this function to return more than true/false, because now
 * we return true even when access is denied! E.g. return -1 for error, 0 on
 * success, 1 on access denied. It can be an option if connection will close
 * on denial.
 */
bool BusyWithNewProtocol(EvalContext *ctx, ServerConnectionState *conn)
{
    /* The CF_BUFEXT extra space is there to ensure we're not *reading* out of
     * bounds in commands that carry extra binary arguments, like MD5. */
    char recvbuffer[CF_BUFSIZE + CF_BUFEXT] = { 0 };
    /* This size is the max we can SendTransaction(). */
    char sendbuffer[CF_BUFSIZE - CF_INBAND_OFFSET] = { 0 };
    char filename[CF_BUFSIZE + 1];      /* +1 for appending slash sometimes */
    ServerFileGetState get_args = { 0 };

    /* We already encrypt because of the TLS layer, no need to encrypt more. */
    const int encrypted = 0;

    /* Legacy stuff only for old protocol. */
    assert(conn->rsa_auth == 1);
    assert(conn->user_data_set == 1);

    /* Receive up to CF_BUFSIZE - 1 bytes. */
    const int received = ReceiveTransaction(conn->conn_info,
                                            recvbuffer, NULL);

    if (received == -1)
    {
        /* Already Log()ged in case of error. */
        return false;
    }
    if (received > CF_BUFSIZE - 1)
    {
        UnexpectedError("Received transaction of size %d", received);
        return false;
    }

    if (strlen(recvbuffer) == 0)
    {
        Log(LOG_LEVEL_WARNING,
            "Got NULL transmission (of size %d)", received);
        return true;
    }
    /* Don't process request if we're signalled to exit. */
    if (IsPendingTermination())
    {
        Log(LOG_LEVEL_VERBOSE, "Server must exit, closing connection");
        return false;
    }

    /* TODO break recvbuffer here: command, param1, param2 etc. */

    switch (GetCommandNew(recvbuffer))
    {
    case PROTOCOL_COMMAND_EXEC:
    {
        const size_t EXEC_len = strlen(PROTOCOL_NEW[PROTOCOL_COMMAND_EXEC]);
        /* Assert recvbuffer starts with EXEC. */
        assert(strncmp(PROTOCOL_NEW[PROTOCOL_COMMAND_EXEC],
                       recvbuffer, EXEC_len) == 0);

        char *args = &recvbuffer[EXEC_len];
        args += strspn(args, " \t");                       /* bypass spaces */

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Received:", "EXEC", args);

        bool b = DoExec2(ctx, conn, args,
                         sendbuffer, sizeof(sendbuffer));

        /* In the end we might keep the connection open (return true) to be
         * ready for next requests, but we must always send the TERMINATOR
         * string so that the client can close the connection at will. */
        Terminate(conn->conn_info);

        return b;
    }
    case PROTOCOL_COMMAND_VERSION:

        snprintf(sendbuffer, sizeof(sendbuffer), "OK: %s", Version());
        SendTransaction(conn->conn_info, sendbuffer, 0, CF_DONE);
        return true;

    case PROTOCOL_COMMAND_GET:
    {
        int ret = sscanf(recvbuffer, "GET %d %[^\n]",
                         &(get_args.buf_size), filename);

        if (ret != 2 ||
            get_args.buf_size <= 0 || get_args.buf_size > CF_BUFSIZE)
        {
            goto protocol_error;
        }

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Received:", "GET", filename);

        /* TODO batch all the following in one function since it's very
         * similar in all of GET, OPENDIR and STAT. */

        size_t zret = ShortcutsExpand(filename, sizeof(filename),
                                     SV.path_shortcuts,
                                     conn->ipaddr, conn->revdns,
                                     KeyPrintableHash(ConnectionInfoKey(conn->conn_info)));
        if (zret == (size_t) -1)
        {
            goto protocol_error;
        }

        zret = PreprocessRequestPath(filename, sizeof(filename));
        if (zret == (size_t) -1)
        {
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        PathRemoveTrailingSlash(filename, strlen(filename));

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Translated to:", "GET", filename);

        if (acl_CheckPath(paths_acl, filename,
                          conn->ipaddr, conn->revdns,
                          KeyPrintableHash(ConnectionInfoKey(conn->conn_info)))
            == false)
        {
            Log(LOG_LEVEL_INFO, "access denied to GET: %s", filename);
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        memset(sendbuffer, 0, sizeof(sendbuffer));

        if (get_args.buf_size >= CF_BUFSIZE)
        {
            get_args.buf_size = 2048;
        }

        /* TODO eliminate! */
        get_args.conn = conn;
        get_args.encrypt = false;
        get_args.replybuff = sendbuffer;
        get_args.replyfile = filename;

        CfGetFile(&get_args);

        return true;
    }
    case PROTOCOL_COMMAND_OPENDIR:
    {
        memset(filename, 0, sizeof(filename));
        int ret = sscanf(recvbuffer, "OPENDIR %[^\n]", filename);
        if (ret != 1)
        {
            goto protocol_error;
        }

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Received:", "OPENDIR", filename);

        /* sizeof()-1 because we need one extra byte for
           appending '/' afterwards. */
        size_t zret = ShortcutsExpand(filename, sizeof(filename) - 1,
                                      SV.path_shortcuts,
                                      conn->ipaddr, conn->revdns,
                                      KeyPrintableHash(ConnectionInfoKey(conn->conn_info)));
        if (zret == (size_t) -1)
        {
            goto protocol_error;
        }

        zret = PreprocessRequestPath(filename, sizeof(filename) - 1);
        if (zret == (size_t) -1)
        {
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        /* OPENDIR *must* be directory. */
        PathAppendTrailingSlash(filename, strlen(filename));

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Translated to:", "OPENDIR", filename);

        if (acl_CheckPath(paths_acl, filename,
                          conn->ipaddr, conn->revdns,
                          KeyPrintableHash(ConnectionInfoKey(conn->conn_info)))
            == false)
        {
            Log(LOG_LEVEL_INFO, "access denied to OPENDIR: %s", filename);
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        CfOpenDirectory(conn, sendbuffer, filename);
        return true;
    }
    case PROTOCOL_COMMAND_SYNCH:
    {
        long time_no_see = 0;
        memset(filename, 0, sizeof(filename));
        int ret = sscanf(recvbuffer, "SYNCH %ld STAT %[^\n]",
                         &time_no_see, filename);

        if (ret != 2 || filename[0] == '\0')
        {
            goto protocol_error;
        }

        time_t tloc = time(NULL);
        if (tloc == -1)
        {
            /* Should never happen. */
            Log(LOG_LEVEL_ERR, "Couldn't read system clock. (time: %s)", GetErrorStr());
            SendTransaction(conn->conn_info, "BAD: clocks out of synch", 0, CF_DONE);
            return true;
        }

        time_t trem = (time_t) time_no_see;
        int drift = (int) (tloc - trem);

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Received:", "STAT", filename);

        /* sizeof()-1 because we need one extra byte for
           appending '/' afterwards. */
        size_t zret = ShortcutsExpand(filename, sizeof(filename) - 1,
                                      SV.path_shortcuts,
                                      conn->ipaddr, conn->revdns,
                                      KeyPrintableHash(ConnectionInfoKey(conn->conn_info)));
        if (zret == (size_t) -1)
        {
            goto protocol_error;
        }

        zret = PreprocessRequestPath(filename, sizeof(filename) - 1);
        if (zret == (size_t) -1)
        {
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        if (IsDirReal(filename) == 1)
        {
            PathAppendTrailingSlash(filename, strlen(filename));
        }
        else
        {
            PathRemoveTrailingSlash(filename, strlen(filename));
        }

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Translated to:", "STAT", filename);

        if (acl_CheckPath(paths_acl, filename,
                          conn->ipaddr, conn->revdns,
                          KeyPrintableHash(ConnectionInfoKey(conn->conn_info)))
            == false)
        {
            Log(LOG_LEVEL_INFO, "access denied to STAT: %s", filename);
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        Log(LOG_LEVEL_DEBUG, "Clocks were off by %ld",
            (long) tloc - (long) trem);

        if (DENYBADCLOCKS && (drift * drift > CLOCK_DRIFT * CLOCK_DRIFT))
        {
            snprintf(sendbuffer, sizeof(sendbuffer),
                     "BAD: Clocks are too far unsynchronized %ld/%ld",
                     (long) tloc, (long) trem);
            Log(LOG_LEVEL_INFO, "denybadclocks %s", sendbuffer);
            SendTransaction(conn->conn_info, sendbuffer, 0, CF_DONE);
            return true;
        }

        StatFile(conn, sendbuffer, filename);

        return true;
    }
    case PROTOCOL_COMMAND_MD5:
    {
        int ret = sscanf(recvbuffer, "MD5 %[^\n]", filename);
        if (ret != 1)
        {
            goto protocol_error;
        }

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Received:", "MD5", filename);

        /* TODO batch all the following in one function since it's very
         * similar in all of GET, OPENDIR and STAT. */

        size_t zret = ShortcutsExpand(filename, sizeof(filename),
                                     SV.path_shortcuts,
                                     conn->ipaddr, conn->revdns,
                                     KeyPrintableHash(ConnectionInfoKey(conn->conn_info)));
        if (zret == (size_t) -1)
        {
            goto protocol_error;
        }

        zret = PreprocessRequestPath(filename, sizeof(filename));
        if (zret == (size_t) -1)
        {
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        PathRemoveTrailingSlash(filename, strlen(filename));

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Translated to:", "MD5", filename);

        if (acl_CheckPath(paths_acl, filename,
                          conn->ipaddr, conn->revdns,
                          KeyPrintableHash(ConnectionInfoKey(conn->conn_info)))
            == false)
        {
            Log(LOG_LEVEL_INFO, "access denied to file: %s", filename);
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        assert(CF_DEFAULT_DIGEST_LEN <= EVP_MAX_MD_SIZE);
        unsigned char digest[EVP_MAX_MD_SIZE + 1];

        assert(CF_BUFSIZE + CF_SMALL_OFFSET + CF_DEFAULT_DIGEST_LEN
               <= sizeof(recvbuffer));
        memcpy(digest, recvbuffer + strlen(recvbuffer) + CF_SMALL_OFFSET,
               CF_DEFAULT_DIGEST_LEN);

        CompareLocalHash(filename, digest, sendbuffer);
        SendTransaction(conn->conn_info, sendbuffer, 0, CF_DONE);

        return true;
    }
    case PROTOCOL_COMMAND_VAR:
    {
        char var[256];
        int ret = sscanf(recvbuffer, "VAR %255[^\n]", var);
        if (ret != 1)
        {
            goto protocol_error;
        }

        /* TODO if this is literals_acl, then when should I check vars_acl? */
        if (acl_CheckExact(literals_acl, var,
                           conn->ipaddr, conn->revdns,
                           KeyPrintableHash(ConnectionInfoKey(conn->conn_info)))
            == false)
        {
            Log(LOG_LEVEL_INFO, "access denied to variable: %s", var);
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        GetServerLiteral(ctx, conn, sendbuffer, recvbuffer, encrypted);
        return true;
    }
    case PROTOCOL_COMMAND_CONTEXT:
    {
        char client_regex[256];
        int ret = sscanf(recvbuffer, "CONTEXT %255[^\n]", client_regex);
        if (ret != 1)
        {
            goto protocol_error;
        }

        Log(LOG_LEVEL_VERBOSE, "%14s %7s %s",
            "Received:", "CONTEXT", client_regex);

        /* WARNING: this comes from legacy code and must be killed if we care
         * about performance. We should not accept regular expressions from
         * the client, but this will break backwards compatibility.
         *
         * I replicated the code in raw form here to emphasize complexity,
         * it's the only *slow* command currently in the protocol.  */

        Item *persistent_classes = ListPersistentClasses();
        Item *matched_classes = NULL;

        /* For all persistent classes */
        for (Item *ip = persistent_classes; ip != NULL; ip = ip->next)
        {
            const char *class_name = ip->name;

            /* Does this class match the regex the client sent? */
            if (StringMatchFull(client_regex, class_name))
            {
                /* Is this class allowed to be given to the specific
                 * host, according to the regexes in the ACLs? */
                if (acl_CheckRegex(classes_acl, class_name,
                                   conn->ipaddr, conn->revdns,
                                   KeyPrintableHash(ConnectionInfoKey(conn->conn_info)),
                                   NULL)
                    == true)
                {
                    Log(LOG_LEVEL_DEBUG, "Access granted to class: %s",
                        class_name);
                    PrependItem(&matched_classes, class_name, NULL);
                }
            }
        }

        if (matched_classes == NULL)
        {
            Log(LOG_LEVEL_INFO,
                "No allowed classes for remoteclassesmatching: %s",
                client_regex);
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        ReplyServerContext(conn, encrypted, matched_classes);
        return true;
    }
    case PROTOCOL_COMMAND_QUERY:
    {
        char query[256], name[128];
        int ret1 = sscanf(recvbuffer, "QUERY %255[^\n]", query);
        int ret2 = sscanf(recvbuffer, "QUERY %127s", name);
        if (ret1 != 1 || ret2 != 1)
        {
            goto protocol_error;
        }

        if (acl_CheckExact(query_acl, name,
                           conn->ipaddr, conn->revdns,
                           KeyPrintableHash(ConnectionInfoKey(conn->conn_info)))
            == false)
        {
            Log(LOG_LEVEL_INFO, "access denied to query: %s", query);
            RefuseAccess(conn, recvbuffer);
            return true;
        }

        if (GetServerQuery(conn, recvbuffer, encrypted))
        {
            return true;
        }

        break;
    }
    case PROTOCOL_COMMAND_CALL_ME_BACK:
        /* Server side, handing the collect call off to cf-hub. */

        if (acl_CheckExact(query_acl, "collect_calls",
                           conn->ipaddr, conn->revdns,
                           KeyPrintableHash(ConnectionInfoKey(conn->conn_info)))
            == false)
        {
            Log(LOG_LEVEL_INFO,
                "access denied to Call-Collect, check the ACL for class: collect_calls");
            return false;
        }

        ReceiveCollectCall(conn);
        /* On success that returned true; otherwise, it did all
         * relevant Log()ging.  Either way, we're no longer busy with
         * it and our caller can close the connection: */
        return false;

    case PROTOCOL_COMMAND_BAD:

        Log(LOG_LEVEL_WARNING, "Unexpected protocol command: %s", recvbuffer);
    }

    /* We should only reach this point if something went really bad, and
     * close connection. In all other cases (like access denied) connection
     * shouldn't be closed.
     */

protocol_error:
    strcpy(sendbuffer, "BAD: Request denied");
    SendTransaction(conn->conn_info, sendbuffer, 0, CF_DONE);
    Log(LOG_LEVEL_INFO,
        "Closing connection due to illegal request: %s", recvbuffer);
    return false;
}