Как водится, покопавшись во внутренностях Битрикса, нашел ответ, о котором нет ни слова в документации. Может кому-то пригодится.
[CODE]
$res = CFile::GetFileArray($attach_id);
$attach["name"] = $res["ORIGINAL_NAME"];
$attach["size"] = $res["FILE_SIZE"];
$attach["type"] = $res["CONTENT_TYPE"];
$attach["tmp_name"] = $_SERVER["DOCUMENT_ROOT"].$res["SRC"];
$arFields = Array (
"AUTHOR_ID" => "332",
"AUTHOR_NAME" => "AntonovSV",
"AUTHOR_IP" => "192.168.117.33",
"USE_SMILES" => "Y",
"POST_DATE" => "07-05-2009 08:47:08",
"POST_MESSAGE" => "В принципе все уже придумано до нас.",
"POST_MESSAGE_HTML" => "В принципе все уже придумано до нас.",
"ATTACH_HITS" => 0,
"NEW_TOPIC" => "N",
"APPROVED" => "Y",
"POST_MESSAGE_CHECK" => "b1ebecac63036965b53370b0be1f3e97",
"GUEST_ID" => "13082",
"AUTHOR_REAL_IP" => "192.168.117.33",
"ATTACH_IMG" => $attach,
"EDIT_DATE" => "01-01-1970 03:00:00",
"FORUM_ID" => "296",
"TOPIC_ID" => "399",
);
$postRes = CForumMessage::Add($arFields); [/CODE]
[CODE]
$res = CFile::GetFileArray($attach_id);
$attach["name"] = $res["ORIGINAL_NAME"];
$attach["size"] = $res["FILE_SIZE"];
$attach["type"] = $res["CONTENT_TYPE"];
$attach["tmp_name"] = $_SERVER["DOCUMENT_ROOT"].$res["SRC"];
$arFields = Array (
"AUTHOR_ID" => "332",
"AUTHOR_NAME" => "AntonovSV",
"AUTHOR_IP" => "192.168.117.33",
"USE_SMILES" => "Y",
"POST_DATE" => "07-05-2009 08:47:08",
"POST_MESSAGE" => "В принципе все уже придумано до нас.",
"POST_MESSAGE_HTML" => "В принципе все уже придумано до нас.",
"ATTACH_HITS" => 0,
"NEW_TOPIC" => "N",
"APPROVED" => "Y",
"POST_MESSAGE_CHECK" => "b1ebecac63036965b53370b0be1f3e97",
"GUEST_ID" => "13082",
"AUTHOR_REAL_IP" => "192.168.117.33",
"ATTACH_IMG" => $attach,
"EDIT_DATE" => "01-01-1970 03:00:00",
"FORUM_ID" => "296",
"TOPIC_ID" => "399",
);
$postRes = CForumMessage::Add($arFields); [/CODE]