Initial commit - realms platform

openresty/lua/thumbnail.lua

@@ -0,0 +1,180 @@
+local _M = {}
+
+local THUMB_DIR = "/tmp/thumbs"
+local CACHE_TTL = 5  -- seconds before regenerating
+local FFMPEG_TIMEOUT = 15  -- seconds (needs more time for animated capture)
+local ANIMATION_DURATION = 3  -- seconds of video to capture
+local ANIMATION_FPS = 8  -- frames per second in output
+
+-- SECURITY FIX: Shell escape function to prevent command injection
+local function shell_escape(str)
+    -- Escape single quotes by ending the quoted string, adding escaped quote, and starting new quoted string
+    return "'" .. string.gsub(str, "'", "'\\''") .. "'"
+end
+
+local function file_exists(path)
+    local f = io.open(path, "r")
+    if f then
+        f:close()
+        return true
+    end
+    return false
+end
+
+local function file_size(path)
+    local f = io.open(path, "rb")
+    if f then
+        local size = f:seek("end")
+        f:close()
+        return size or 0
+    end
+    return 0
+end
+
+local function file_age(path)
+    -- Get file modification time using stat
+    local handle = io.popen("stat -c %Y " .. path .. " 2>/dev/null")
+    if not handle then
+        return nil
+    end
+    local mtime = handle:read("*a")
+    handle:close()
+
+    if not mtime or mtime == "" then
+        return nil
+    end
+
+    local now = os.time()
+    return now - tonumber(mtime)
+end
+
+local function generate_thumbnail(stream_key, thumb_path)
+    -- Build LLHLS URL - internal docker network
+    local llhls_url = "http://ovenmediaengine:8080/app/" .. stream_key .. "/llhls.m3u8"
+    local log_file = THUMB_DIR .. "/" .. stream_key .. ".log"
+
+    -- First, try to generate animated WebP
+    -- Using os.execute which blocks properly until complete
+    -- SECURITY FIX: Use shell_escape to prevent command injection
+    local cmd = string.format(
+        "timeout %d ffmpeg -y -i %s -t %d -vf 'fps=%d,scale=320:-1:flags=lanczos' -c:v libwebp -lossless 0 -compression_level 3 -q:v 70 -loop 0 -preset default -an %s > %s 2>&1",
+        FFMPEG_TIMEOUT,
+        shell_escape(llhls_url),
+        ANIMATION_DURATION,
+        ANIMATION_FPS,
+        shell_escape(thumb_path),
+        shell_escape(log_file)
+    )
+
+    ngx.log(ngx.INFO, "Generating thumbnail for stream: ", stream_key)
+
+    local exit_code = os.execute(cmd)
+
+    -- Check if file was created and has content
+    if file_exists(thumb_path) and file_size(thumb_path) > 100 then
+        ngx.log(ngx.INFO, "Thumbnail generated successfully: ", thumb_path)
+        os.remove(log_file)
+        return true
+    end
+
+    -- If animated webp failed, try static webp (single frame)
+    ngx.log(ngx.WARN, "Animated webp failed (exit: ", tostring(exit_code), "), trying static")
+
+    -- SECURITY FIX: Use shell_escape to prevent command injection
+    local static_cmd = string.format(
+        "timeout %d ffmpeg -y -i %s -vframes 1 -vf 'scale=320:-1:flags=lanczos' -c:v libwebp -q:v 75 %s > %s 2>&1",
+        FFMPEG_TIMEOUT,
+        shell_escape(llhls_url),
+        shell_escape(thumb_path),
+        shell_escape(log_file)
+    )
+
+    exit_code = os.execute(static_cmd)
+
+    if file_exists(thumb_path) and file_size(thumb_path) > 100 then
+        ngx.log(ngx.INFO, "Static thumbnail generated: ", thumb_path)
+        os.remove(log_file)
+        return true
+    end
+
+    -- Read log file for error info
+    local log_content = ""
+    local log_f = io.open(log_file, "r")
+    if log_f then
+        log_content = log_f:read("*a") or ""
+        log_f:close()
+    end
+
+    ngx.log(ngx.ERR, "Thumbnail generation failed (exit: ", tostring(exit_code), "): ", log_content:sub(-500))
+    return false
+end
+
+function _M.serve()
+    -- Get stream key from nginx variable
+    local stream_key = ngx.var.stream_key
+    if not stream_key or stream_key == "" then
+        ngx.status = 400
+        ngx.header["Content-Type"] = "text/plain"
+        ngx.say("Missing stream key")
+        return ngx.exit(400)
+    end
+
+    -- Sanitize stream key (alphanumeric, dash, underscore only)
+    if not stream_key:match("^[%w%-_]+$") then
+        ngx.status = 400
+        ngx.header["Content-Type"] = "text/plain"
+        ngx.say("Invalid stream key")
+        return ngx.exit(400)
+    end
+
+    local thumb_path = THUMB_DIR .. "/" .. stream_key .. ".webp"
+
+    -- Check if cached thumbnail exists and is fresh
+    local age = file_age(thumb_path)
+    local needs_refresh = not age or age > CACHE_TTL
+
+    if needs_refresh then
+        -- Generate new thumbnail
+        local ok = generate_thumbnail(stream_key, thumb_path)
+        if not ok then
+            -- If generation failed, check if we have a stale one to serve
+            if not file_exists(thumb_path) or file_size(thumb_path) < 100 then
+                ngx.status = 503
+                ngx.header["Content-Type"] = "text/plain"
+                ngx.header["Retry-After"] = "5"
+                ngx.say("Thumbnail generation in progress")
+                return ngx.exit(503)
+            end
+            -- Serve stale thumbnail
+        end
+    end
+
+    -- Verify file exists and has content
+    if not file_exists(thumb_path) or file_size(thumb_path) < 100 then
+        ngx.status = 503
+        ngx.header["Content-Type"] = "text/plain"
+        ngx.header["Retry-After"] = "5"
+        ngx.say("Thumbnail not ready")
+        return ngx.exit(503)
+    end
+
+    -- Serve the thumbnail file
+    ngx.header["Content-Type"] = "image/webp"
+    ngx.header["Cache-Control"] = "public, max-age=" .. CACHE_TTL
+    ngx.header["Access-Control-Allow-Origin"] = "*"
+
+    local f = io.open(thumb_path, "rb")
+    if not f then
+        ngx.status = 500
+        ngx.header["Content-Type"] = "text/plain"
+        ngx.say("Failed to read thumbnail")
+        return ngx.exit(500)
+    end
+
+    local content = f:read("*a")
+    f:close()
+
+    ngx.print(content)
+end
+
+return _M